ICEB Design and Cons.. - Center for Vocational Building Technology

ICEB: Design and Construction Manual
Civil Engineering Senior Design 2010 Cal Poly, San Luis Obispo Clayton Proto, Geotechnical Danielle Sanchez, Water Kendra Rowley, Structural Robert Thompson, Seismic Dr. Robb Moss, Project Advisor This is a design and construction manual for interlocking compressed earth block (ICEB) dwellings in seismic regions. ICEBs are seen as a valuable technology for emerging countries, but their current design and construction procedures have not yet been fully examined. The manual seeks to outline the necessary field tests, seismic resisting structural elements, design guidelines, as well as water management recommendations for creating economic, sustainable, safe, and durable dwellings. The intended audiences of this manual are both development workers and local communities within emerging countries who possess limited technical knowledge. This work is a compilation of a thorough literature review and laboratory strength testing at California Polytechnic State University, San Luis Obispo, by both graduate and undergraduate students. INTRODUCTION ................................................................................................................................... 1 SOIL ..................................................................................................................................................... 2 SOIL STRUCTURE ...................................................................................................................................... 2 SOIL DEPOSITS ......................................................................................................................................... 3 SOIL IDENTIFICATION................................................................................................................................. 3 CONDUCTING TESTS .................................................................................................................................. 5 SOIL SELECTION CRITERIA ......................................................................................................................... 12 SOIL REMEDIATION ................................................................................................................................. 13 CEMENT ............................................................................................................................................... 14 BLOCK PRODUCTION .......................................................................................................................... 15 SOIL PREPARATION ................................................................................................................................. 16 MEASURING ......................................................................................................................................... 17 MIXING ............................................................................................................................................... 17 PRESSING ............................................................................................................................................. 20 CURING ................................................................................................................................................ 22 TESTING OF BLOCKS ................................................................................................................................ 22 STRUCTURAL DESIGN ......................................................................................................................... 26 FOOTINGS ............................................................................................................................................ 26 WALLS ................................................................................................................................................. 34 ROOF .................................................................................................................................................. 38 SEISMIC DESIGN ................................................................................................................................. 42 GENERAL DESIGN CONSIDERATION FOR EARTHQUAKE FORCES ......................................................................... 43 SEISMIC DESIGN EXAMPLE PROCEDURE ....................................................................................................... 48 FAILURES MODES OF ICEB STRUCTURES...................................................................................................... 58 WATER MANAGEMENT ...................................................................................................................... 61 WALLS ................................................................................................................................................. 61 ROOF WATER CONSIDERATIONS ................................................................................................................ 64 FOUNDATION ........................................................................................................................................ 66 OPENINGS ............................................................................................................................................ 72 APPENDIX A ....................................................................................................................................... 75 APPENDIX B ....................................................................................................................................... 77 GAPS .................................................................................................................................................. 78 WORKS CITED .................................................................................................................................... 79 Introduction The first stabilized compressed earth blocks, or CEBs, were made in 1954 with development of the world’s first block press, the CINVA‐Ram, by engineer Raul Ramirez (Wheeler, 2006). CEBs are made by mixing a small amount of binder, typically cement, with soil and then compressing the mixture to produce a regular and durable block. CEBs have a number of advantages as a building material, most notably how economical their production can be. The primary component, soil, is typically acquired immediately adjacent to the project site at a minimal cost. Other costs, such as the energy required for firing traditional bricks, are eliminated in CEB production. The overall energy input and low cost of materials make CEBs both an economical and environmentally friendly method of construction. A number of years after the CINVA‐Ram was first invented, the press design was improved upon by a block press capable of producing interlocking compressed earth blocks, or ICEBs (Wheeler, 2005). The biggest advantage of ICEBs over their non‐interlocking counterparts is that ICEBs can be laid without the use of mortar. This construction aspect is a substantial economical improvement, as it is a reduction in both material and labor costs. However, ICEB construction will not always be an appropriate or the most economical method of construction, and many factors need to be taken into account for a preliminary assessment. •
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Only after all of these steps have been satisfied should design and block production begin. Page
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Any and all information regarding local regulations, permits, and codes pertaining to the project must be gathered Environmental considerations should be assessed. Conditions such as extreme rainfall, soft footing soil, or Figure 1: ICEBs (Wheeler, 2005) extremely seismic regions may require so much mitigation such that ICEB construction is no longer economical The availability of building materials, such as cement, rebar, and corrugated steel need to be determined Soils in the immediate vicinity of the project site should be sampled and tested, as outlined in this manual, to determine if they can be used for CEB construction Soil Soil is defined as any loose material deposits on the Earth’s surface which distinguishes it from the parent rocks of which it is derived. Soil formation is a product of the weathering of the Earth’s crust and the subsequent decomposition into its various mineral constituents. Soil at a given location may have been formed locally, a residual soil, or it may have been transported great distances by air or water and be termed a transported soil. Because this natural process of weathering is completely non‐uniform, no two soil samples are exactly alike. This enormous variability in soil composition means that any given soil has a wide range of potential properties which need to be assessed for any construction project. For the construction of ICEB dwellings, the soil’s role is doubly important: it both underlies the foundation and is the primary building material. This section is intended to advise the user on how to identify a soil and assess its potential for use in ICEB construction. Therefore, these tests should be performed in the preliminary site assessment. If a soil is found to not be suitable, various methods of soil remediation are outlined. Soil Structure The mechanical behavior of a soil is primarily based upon the grain sizes of its constituent particles. The four soil classifications which we will consider in ICEB construction are: gravels, sands, silts, and clays. By properly identifying and modifying the proportions of each of these grain sizes, the user will have a great deal of control over the final block quality. Gravels‐ Particle diameters greater than 2 mm, may be rounded or jagged. Have no noticeable amounts of swell and shrinkage. No cohesion. Excessive gravels may interfere with the block press. Sands‐ Particle diameters between 2 and .06 mm (metric), typically made of quartz or silica. Have minimal amount of swell and shrinkage. No cohesion. Sands play an important role in forming a cement matrix in the blocks. Page
Figure 2: Grain sizes (Schildkamp, 2009) Clays‐ Particle diameters less than .002 mm, clays are subject to significant amount of swelling and shrinkage. High amounts of cohesion. Some clay is required for block production, but excessive amounts are considered detrimental to finished block quality.
2 Silts‐ Particle diameters between .06 and .002 mm, subject to some amounts of swelling and shrinkage. Some cohesion. Excessive amounts of silts are considered detrimental to finished block quality. Soil Deposits Soils are constantly undergoing the weathering process, and as a result they usually form layers, or horizons, of similarly composed soils at the same depth. Organic matter accumulates in horizons in the upper most portions of the soil, while the parent rock resides at a depth below the surface. Soil most suited for ICEB production is located below the organic top soil, typically 10‐50 cm in depth, and above rocky soil (Morel et al. 2001). This is illustrated in Figure 3. Figure 3: Soil Deposits (Schildkamp, 2009) The usable soil thickness can vary from a few centimeters to many meters in depth. Because of this, the user is encouraged to examine multiple potential borrow sites Soil Identification If performed properly, the following tests should give the user sufficient information to judge a soil’s suitability. However, these tests only give a basic understanding of a soil’s composition and properties, and therefore do not guarantee finished blocks will be 100% satisfactory. Instead, these tests will only indicate which soils have the highest probability of being amenable to ICEB production. In all cases, test finished blocks to ensure their quality before construction. Page
3 Before selecting a site or taking a sample, consult all pertinent information with regard to local soil and geologic setting. Potential sources include soil science maps, hydrologic and rainfall data, and geologic surveys. Taking a Sample Suggested Equipment: Auger, mechanical or hand operated Required Equipment: Shovel, sample containers, labels Duration: Anywhere from 10 minutes to a few hours A sample of potential soil can be rapidly taken from depths of up to 5 m by using an auger. The downside of using an auger is that it has the potential to mix soils from different depths. Alternatively, a 1 m wide by 2 m deep hole can be dug to allow for the sampling of soil. The soil from the hole should first be removed completely, and then samples are taken directly by digging into the hole wall at various depths. Care should be taken to ensure the safety of anyone in the hole, as the hole may be prone to collapse in weak soils. Conditions permitting, samples may also be taken from a naturally exposed slope where soil layers are clearly visible. Because the sample is from the surface, extra care should be taken to remove all surficial organic matter or debris. A 2‐3 kg sample should be sufficient for all identification procedures. Tips: •
Avoid mixing separate soil horizons. •
Do not attempt to improve a sample by adding or removing anything from the sample's natural state. •
If soil is heterogeneous, do not try to take an "average" sample. Take multiple samples instead. •
Record and label all samples. Samples should be labeled according to their location with respect to a monument or a grid system, date, depth, person taking the sample, and any additional comments. Quartering After a sample is obtained from the field, the method of quartering is used to select an unbiased subsample of material to conduct tests with. Figure 4: Quartering
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4 1. Pile the soil on a flat surface, and then flatten the cone into a disc‐like shape. 2. Divide the sample into quarters by scoring the soil surface, and then discard two opposite quarters. 3. Repeat this process until the desired amount of material remains. Conducting Tests The following are a compilation of various tests that can be performed on soil samples with very limited equipment. As stated before, the tests outlined herein will not yield foolproof or precise results, but simply give a general indication of a soil's suitability. Conduct additional laboratory tests if working on an important housing project or if these tests yield either conflicting or inconclusive results. The following soil tests can be divided into two main categories: •
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Qualitative o Visual Examination o Smell Test o Sedimentation Analysis o Fine Grain Identification Quantitative o Linear Shrinkage (Alcock’s Test) o Washing Test The final determination of soil suitability is primarily based on the two quantitative tests, but it is important to also ensure agreement of all test results. Visual Examination Optional equipment: Magnifying glass Duration: A few minutes A dry sample is examined by sight to estimate the relative fractions of gravels, sands, and fines. The fines fraction, a combination of clays and silts, is considered to be just beyond the resolving power of the naked eye. Describe maximum particle size from fine (.06 mm) to coarse (2 mm) for sands, or minimum sieve opening particles will pass for gravel. Example: 20% 10 mm gravel, 30% fine to coarse sand, 50% fines. These results should be compared to those obtained in Sedimentation Test. Smell Test Duration: A few minutes Page
5 Smell the soil sample immediately after removal from the ground. A musty smell indicates the presence of organic matter. This musty smell is made stronger upon heating or wetting. Organic matter is undesirable for ICEB production, so noticeable amounts of organic matter means soil will typically have to be taken from either a deeper depth to be sufficiently below the organic layer or a different site altogether. Sedimentation Test Necessary Equipment: Transparent jar or bottle at least .5 L in capacity Duration: 5 minutes for conducting test, a few hours for results 1. Fill the container ¼ full with soil, and add enough water to fill the jar. 2. Seal the top, and then shake the container vigorously to suspend the soil particles. 3. Let the container stand for a few hours or until the water is clear. Observe sediment layers. Interpretation: Gravel particles will have settled the fastest, and therefore will be at the bottom of the container. Gravel is immediately followed by sands, then silts, and finally clays. Organic matter will float to the top. Estimate the proportion of each of these by their relative layer thickness. This is illustrated in Figure 5. Observed results should be compared to those obtained in the Washing Test. Notes: •
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Clays and silts may be overestimated because of their expansion in the Figure 5: Sedimentation Test (Houben and Guillard, 1994)
presence of water. Because of longer settlement times, better results are obtained by the use of a taller container. Fine Grain Identification – After ASTM D 2488­06 The following tests (Dry Strength, Dilatancy, Toughness, and Plasticity) are to be performed in succession. Begin by selecting a representative sample of soil by Quartering and manually remove particles larger than .6 mm (coarse sand and larger), or any particles observed to interfere with the tests. Approximately a handful sized sample is required. Add water to a small soil sample until it has a putty‐like consistency. Make three or four test specimens by rolling the soil into balls about 12mm in diameter. Allow samples to fully air or sun dry. Test strength by crushing balls between thumb and finger, noting the strength as described in Table 1. Page
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6 Dry Strength Table 1: Criteria for Describing Dry Strength Description None Criteria Specimens crumble simply by handling Low Specimens crumble into powder with some pressure Medium Specimens break into pieces or crumble with application of considerable pressure High Specimens cannot be broken between thumb and finger, can only be broken into pieces between a thumb and a hard surface Very High Specimens cannot be broken between a thumb and a hard surface Dilatancy 1. Take a small sample of soil and add water until it has a soft but not sticky consistency. 2. Mold the soil into a ball approximately 12 mm in diameter. 3. Spread the soil ball into the palm of one hand with a knife or spatula into a thin layer. 4. While leaving the palm horizontal, alternate between opening and closing the palm of the hand. Note how rapidly water appears on the soil surface. 5. Squeeze the sample by making a fist or pinching the sample. Note how quickly water disappears while squeezing. 6. Use Table 2 to describe dilatancy characteristics. Table 2: Criteria for Describing Dilatancy Description None Criteria No visible change in the specimen Slow Water appears slowly on the surface of the specimen during opening and closing, and does not disappear or disappears slowly upon squeezing Rapid Water appears quickly on the surface of the specimen during opening and closing, and disappears quickly upon squeezing Page
7 Toughness 1. Using the same sample as from the Dilatancy test, shape the soil into an elongated pat. 2. Roll the pat into a thread about 3 mm in diameter. 3. Fold the sample threads and reroll repeatedly until the thread crumbles at a diameter of about 3 mm. This is approximately the plastic limit. Note the required pressure to roll the thread. 4. Lump the thread pieces together and knead the lump until it crumbles. 5. Describe the toughness of the thread and lump in accordance with the criteria in Table 3. Figure 6: Rolling the soil (Schildkamp, 2009)
Table 3: Criteria for Describing Toughness Description Low Criteria Only slight pressure is required to roll the thread near the plastic limit. The thread and the lump are weak and soft Medium Medium pressure is required to roll the thread to near the plastic limit. The thread and the lump have medium stiffness High Considerable pressure is required to roll the thread to near the plastic limit. The thread and the lump have very high stiffness Page
8 Plasticity 1. From the sample behavior observed in the Toughness test, use the criteria in Table 4 to assign an appropriate plasticity description. Table 4: Criteria for Describing Plasticity Description Non‐plastic Criteria Low The thread can barely be rolled and the lump cannot be formed when drier than the plastic limit Medium The thread is easy to roll and not much time is required to reach the plastic limit. The thread cannot be rerolled after reaching the plastic limit. The lump crumbles when drier than the plastic limit. High It takes considerable time rolling and kneading to reach the plastic limit. The thread can be rerolled several times after reaching the plastic limit. The lump can be formed without crumbling when drier than the plastic limit A 3mm thread cannot be rolled at any water content Table 5: Classification of Inorganic Fine‐Grained Soils from Manual Tests Description Low‐Plasticity Silt (ML) Dry Strength Dilatancy Plasticity & Toughness None to low Slow to rapid None to low Low‐Plasticity Clay (CL) Medium to high None to slow Medium High‐Plasticity Silt (MH) Low to medium None to slow Low to medium High‐Plasticity Clay (CH) High to very high None High Linear Shrinkage (Alcock's Test) Necessary Equipment: Wooden box with dimensions 4x4x60 cm, oil, spatula Duration: 30 minutes for preparation, 3‐7 days for drying Page
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Remove gravel and coarse sands (>.6mm) from a sample of soil. Add water to the soil sample until it has reached optimum moisture content (OMC)*. Grease the inside surfaces of the box. Press the moistened soil into the box, using a wooden spatula for the corners. Smooth the top of the box. Let dry 3 days in the sun, or 7 days in the shade. 7. Push the dried soil to one end of the box. Measure and record the distance from the soil to the other end of the box. *See the Drop Test (Page 19) for instructions on how to determine OMC Figure 7: Linear Shrinkage Test (Houben and Guillard, 1994)
Washing Test An alternative to this test is wet sieving a sample of soil using a Number 200 (75 micron) sieve. Necessary Equipment: A precise scale, such as a triple beam balance; an oven, microwave, or other means for thoroughly drying the soil samples; buckets, bowls, and tins of varying sizes; and a 2 mm screen Duration: 30‐60 minutes for conducting test, longer for drying sample General: The idea behind this test is that the fines (clays and silts) in the soil will remain suspended in water for a short amount of time, while sands and gravels settle out immediately. By carefully and repeatedly washing a soil sample, all of the clay and silt particles can be removed. 1. Take a sample of soil approximately 500‐1000 g. 2. Dry the soil until its mass stops dropping and record the final mass of the soil. •
Note: Samples that feel and look completely dry may still have some water content. For accurate results, it is important that the sample be completely void of water. 3. Place the dried sample in a bucket or bowl and fill with water. 4. Thoroughly agitate the soil in the bottom of the bucket to suspend the fines. Note: The first time you fill the bucket with water, organic matter may float to the top. Remove the organic matter manually. If there is a large amount of organic matter at the surface, the soil will likely be unsuitable for use. Page
5. Carefully decant the bucket by pouring off as much water as possible while leaving the sand and gravels undisturbed at the bottom. 10 •
6. Refill the bucket with water and repeat Steps 4 & 5 until the water remains clear after agitation, signifying that all the fines have been removed. Depending on soil type and sample size, this may take upwards of 20 repetitions. 7. Remove, dry, screen (2 mm), and weigh the remaining sand and gravel sample. Compare with the initial measurements to determine the relative percentages of gravel, sands, and fines. Example test results and analysis are provided in Appendix A. Water Testing Salts or other deposits in the water may interfere with the cement binding process. To account for this possibility, two simple tests are used. The first is a tasting test, in which the water is tasted to determine if there are any salts present. In the second test, water is evaporated out of a pan and the pan is then inspected for residual deposits. These deposits are to be avoided altogether. In general, potable water is considered suitable for use (Rigassi, 1995). Chemical Testing This manual does not address ways of detecting potentially harmful chemicals, such as sulfates, in soils. Calcium sulfates in particular are common in soils, and attack the hardened cement matrix. The research or development of field methods for identifying sulfates in soils is a top priority. Page
11 Soil Selection Criteria A very important characteristic determining a soil's suitability is its clay content. At high concentrations (>20%), clay interferes with the bonding of the cement particles, as well as introducing large shrink/swell characteristics into the block. However, some amount of clay content is in fact desired because the natural cohesive properties provided by the clay particles reduce the necessary amounts of binding agents. Additionally, the clay content provides cohesion to allow for freshly made blocks to be handled immediately after pressing. A minimum clay content of at least 5% is therefore required, and 15% is recommended (Venkatarama Reddy et al., 2007). The three best indicators of soil suitability for cement stabilization were determined to be linear shrinkage, sand content, and plasticity index, with the classification for favorable soils being <6% linear shrinkage, or >65% sand, or PI <15% (Burroughs, 2006). The recommended criteria for selecting a soil are as follows: AND •
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<6% linear shrinkage, as determined by the Linear Shrinkage Test o This ensures that there is not a significant amount of highly expansive clays and limits the overall clay content. >65% sand content, as determined by the Washing Test o This ensures that there is a sufficient amount of sand for cement binding, and also limits the clay content. <10% gravel (2‐5 mm diameter), as determined by the Washing Test >15% fines, as determined by the Washing Test o This ensures blocks will have enough strength to be handled immediately after pressing. At least medium plasticity/toughness and dry strength, as determined by Fine Grain Identification o This ensures that the fines fraction is not solely silts. No significant amounts of organic matter, as determined by the Smell and Sedimentation Tests Page
It should be noted that the above criteria is more strict than usual for CEB production. However, given the very limited amount of testing which is done on the soil, these stricter soil criteria are justified. If the user has the ability to conduct a more thorough testing of a soil or has previous experience using a soil for CEB production, the omission of some of these requirements may be permissible. 12 •
Soil Remediation The soil at a specific site may not meet all of the requirements for ICEB production. The following are various ways to improve a soil to allow for more satisfactory results. •
Not enough sand or too much linear shrinkage: Add more sand. If a source of sand is available, the grain size proportions of both soil samples should be taken (Note: good sand will have negligible amounts of fines). Combine the two in proper proportions such that the resulting soil has the desired grain size distribution. Sample calculations of this procedure are provided in Appendix A. If a source of sand is not readily available, the original soil may be washed to remove fines. To ensure that not all of the fines are removed, only a fraction of the soil should be washed of its fines, and the resulting sand is then recombined with the original unwashed soil. •
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Too much gravel content: Remove gravel particles by screening the soil. Also, a pulverizer may be used to break down the larger gravels into small pieces. Not enough fines (<15%): Add more fines. A clayey soil has to be located, and the sand and fines contents of each should be determined. The two can then be mixed in proportions such that the resulting soil has the desired grain size distribution. Insufficient Dry Strength or Plasticity: Locate and add a source of clayey soil. Organic matter: The addition of 2% lime may help to neutralize the effects of organic matter (Houben and Guillard, 1994). Otherwise, select a different soil for use. Laboratory Testing If the provided field tests are insufficient, the following are some recommended lab tests to help determine soil suitability: •
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Atterberg Limits‐ PI < 15 is desired Sieve and hydrometer grain size analysis o Well graded soils yield better results o Pinpoint silt and clay fractions Standard Proctor compaction Clay mineralogical analysis‐ Expansive clays, such as montmorillonites, are detrimental to block production Chemical analysis Cement Cement has been used for improving a soil's mechanical properties for nearly a century. In ICEB production, the effects of addition of cement are as follows: •
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Increasing block strength‐ Both the wet and dry compressive strength of a favorable soil increase. Past studies have shown each additional 1% of cement content increases compressive strength by approximately .4 MPa (Burroughs, 2006). Stability‐ Decreases the magnitude of both dry shrinkage and wet swelling Durability‐ Reduces a block’s susceptibility to erosion, especially at high sand contents Virtually any soil can be adequately stabilized with cement, but for certain soil types this becomes uneconomical due to the high amount of cement required. A cement content of 10‐12% is seen as being an approximate economical limit. Generally speaking, at least 5% cement content by weight is needed to provide adequate strength, durability, and stability. However, a thorough soil analysis and past soil‐
concrete test results may permit using a cement content of as low as 3‐4%. This manual assumes the use of ordinary Portland Cement. Cements containing other materials such as fly ash can be used, but the required amounts may need to be adjusted. Because of varying field conditions and further variations in the block production process, required amount of cement may need to be increased by up to 150% (Houben and Guillard, 1994). Table 6: Estimating Cement Contents with Linear Shrinkage Results Suggested Initial Cement Content (by weight) Linear Shrinkage (Alcock’s Test) Results <1.5 cm (2.5%) 5% 1.5 to 3 cm (2.5‐5%) 3 to 4.5 cm (5‐7.5)% 4.5 to 6 cm (7.5‐10%)
6% 8% 10% After Houben and Guillard (1994) Page
14 Block Production This manual is written assuming that its readers have access to a hand operated CVBT ICEB block press. Block output is wholly dependent on the size and skill of the team making the blocks, but a reasonably anticipated output to expect is on the order of 300‐600 blocks/day. A small house requires approximately 3000 blocks to construct, requiring roughly a week’s worth of production. For every step listed below, there are mechanical and labor savings alternatives available. However, given the assumed scale of production, these mechanical methods are generally not addressed. Overview of the block production process: Soil Preparation
Measuring
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15 Curing
Testing
Soil Preparation Extraction The approximate amount of materials required for one day of production (300 blocks) are: •
2 m3 of untreated soil‐ This is roughly a pile of dirt 1.25m high, or ten 200 L barrels •
130 kg cement (6% stabilization) •
225 L of water
Expected rates of manual soil extraction vary greatly depending upon ground conditions, anywhere from 1‐4 m3 of soil per man‐day (8 hours). Important: Before beginning extraction, the user must figure out how areas with removed earth will be remediated upon completion of the project. It is recommended that the topsoil and any waste materials be retained for re‐filling any holes. Also, if any changes are noticed in soil color or texture during the extraction process, the soil should again be tested to determine its properties. Transportation Soil needs to be transported from the excavation site to the preparation area. This is typically done via wheelbarrow. Production is on the order of 10 m3 of soil per man‐day. For longer distances (100‐500 m), an animal driven cart may be a more efficient alternative. Drying Soil should be spread out and allowed to dry before pulverizing or crushing. This is best done on a hard, flat surface. Drying can be done over an uncovered area during the dry season; otherwise a roofed and protected area is mandatory. Drying times vary considerably based on soil and weather conditions. Page
Screening Screening may not be necessary if the pulverizer is observed to thoroughly crush the soil. However, screening is mandatory if the soil is manually crushed. For use with the CVBT block press, all soil should pass a 5 mm screen. 16 Pulverizing/Crushing For operations with clayey soils, the use of a mechanical pulverizer is virtually mandatory. Large rocks should either be removed manually or by the use of a large opening screen. Consult the pulverizer manual for specific operating instructions. Outputs vary, but are on the order of 30 m3 per day. Manual crushing of dried soil clumps has an extremely low output, on the order of 1m3 per man‐day (Houben and Guillard, 1994). Measuring Measuring of soil and sand should first be done by weight and then transitioned to a volumetric system. A volumetric system is easier, and is more accurate when dealing with soils that have potentially varying mositure contents. Before a volumetric system can be used, buckets, wheelbarrows, and shovels of varying sizes should be "calibrated" to determine their capacities for sand and soil. To ensure a consistent finished product, cement needs to be measured out by weight on a precise scale or volumetrically by using a specially made measuring box. If measuring is done by dividing a full sack of cement, the sack should be divided up into equal parts at one time (See Figure 8). Figure 8: The measuring of cement Mixing Mixing greatly affects finished block quality, and therefore must be done thoroughly. When performed manually, both wet and dry mixing should be done on a hard, flat, non‐absorbent surface. In both cases, special attention should be paid to ensure that the shovels scrape and pick up soil from the very bottom of the pile. Page
17 Dry Mixing The soil, cement, and any necessary sand should be combined and then thoroughly mixed to achieve a mix which is homogeneous in both color and texture. If this is done by hand, the pile should be turned at least 3 times. Figure 9 illustrates this procedure. A regular concrete mixer can also be used for dry mixing. Figure 9: The dry mixing process 80%
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Figure 10: Effect of retention time on 28‐day compressive strength
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It is important to move from wet mixing the soil to compression as quickly as possible. Figure 10 shows the effect of retention time, the time from first hydration to compression, on block strength (Kerali and Thomas, 2002). Discard any soil with a retention time of greater than 60 minutes. 100%
Relative Compressive Strength
Wet mixing Once the dry mixing is complete, water is added to hydrate the concrete and allow the soil to be compressed. Moisture content of a soil is defined as: The optimum moisture content (OMC) is the specific moisture content which allows for the densest particle formation for a given compaction effort. Although the compaction processes are completely different, the OMC obtained from a Standard Proctor Compaction test correlates closely with the water content at which the blocks should be formed (Rigassi, 1995). However, the total amount of water added to a mix should not be determined by a single fixed moisture content value, but rather the Drop Test is used to estimate the OMC while mixing each batch. Optimum moisture contents of soils used for block production typically lie within a range of 10 to 14 %. It is recommended that enough water is added to the mix such that it is at 10% moisture content, and then additional increments of 1% are added while conducting the Drop Test at each increment. Once a familiarity with a specific soil has been established, this process can be modified to allow for a more efficient wet mixing process. It is also recommended to have a hold back of dry, mixed soil to be readily used in the event the sample is too wet. Drop Test 1. Take a handfull of moistened soil and shape it into a ball using a moderate amount of pressure. 2. Drop the ball of soil onto a hard surface from a height of 1 m. 3. Observe the reaction of the ball. Observed Result
Conclusion
Ball shattered or broke Soil is too dry into more than 7 pieces Ball broke into 4‐6 pieces Water content suitable for compression Ball broke into 3 or less pieces, or didn't break at Soil is too wet all 4. Repeat Drop Test at least 3 times to get an average result. Wet mixing works best with a group of 2‐4 people. Use a wide‐nozzle watering can to wet the mixture while turning. Avoid wetting a mix too rapidly to prevent the formation of clumps. Continue to turn the mix, wetting if necessary, and break up any large clumps. Wet mixing is complete when soil is homogenous and passes the Drop Test. Page
19 Unlike dry mixing, a cement mixer can NOT be used. Pressing A measured quantity of soil that is poured in the block press is called a charge. After the wet mixing is complete, weigh out charges in individual containers. All charges should be the same weight to ensure a sufficient and consistent block density. For the CVBT press, minimum block dry densities of at least 1700kg/m3 should be achieved (Fitzmaurice, 1958; Spence, 1975), with 1800kg/m3 recommended (Venkatarama Reddy and Gupta, 2005). In addition to cement content, block density is a primary factor of overall product quality (Gooding and Thomas, 1997). Dry density is defined as: See Appendix A for sample calculations detailing how to determine charge size. Pour the weighed charge into the mold, and level the surface by hand. Clear off the grout‐hole inserts so that they are fully exposed, and compress the soil in the corners by hand. Figure 11: Filling the block press Page
When removing blocks from the press, handle them from the sides and place it on a board for transportation to the curing area. When removed from the press, a pocket penetrometer can be used to check for a minimum strength of 5kg/cm2. If the block isn’t strong enough, the charge sizes should be increased. 20 The compression stroke should be as smooth as possible and at least 2 seconds in duration to help prevent lamination of the soil. Allow the soil to remain fully compressed for an additional 1‐2 seconds before disengaging the lever arm. Observe the block surfaces and consult Table 7 for suggested means of correcting the production process. Table 7: Adjusting Block Production Observed Effect Possible Cause Block sticking to bottom plate Excessive water content after compression Decrease water content Rough block surfaces Excessive water content Decrease water content Excessive water content Decrease water content Too rapid rate of compression Difficulty compressing or ejecting block Block is too dense Compress block at a slower rate Reduce charge size Block has too much clay Add more sand to block mix Uneven block ejection Saturate the surface of the block where the crack appears before ejection Lamination or layering of soil Crack appears on top surface during the ejection process Remediation A Note on Block Inserts The CVBT press is compatible with a number of inserts which allow the production of specialty blocks required for the construction process. Among the most useful inserts are those required for construction are: •
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Channel blocks‐ Allow for horizontal reinforcement to be installed inside the walls Half blocks‐ Allow for proper construction of openings and T‐wall intersections End blocks‐ Produced without one side’s grout channel, for use in corners, openings, and intersections
Depending on what inserts are being used, the charge size may have to be scaled down to produce desired block densities. Some specialty blocks, such as the channel blocks, must be handled in a much more careful manner than regular blocks and may not be able to be stacked while curing. Page
21 Curing Relative Compressive Strength
The basic theory behind properly curing CEBs is to keep them as moist as possible for as long as possible. Figure 12 (Kerali and Thomas, 2002) shows the effects of various curing methods on 28‐day compressive strength. 100%
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60%
40%
20%
0%
Open air, dry
Open air, periodically damped
Sheet Covered
Fully immersed in water
Figure 12: The effect of curing conditions on 28‐day compressive strength CEBs have minimum curing time of 14 days, while 28 is strongly recommended. During this time the material should be kept in an environment that is as moist as possible, sheltered from the sun, and protected from temperature extremes. The curing area should be located on level, hard ground close to the block production. The blocks should be stacked on a ground tarp, in individual columns, no more than 5 blocks in height. To allow for handling and placement, spacing between the block columns should be approximately 4 cm. Freshly molded blocks are weak, and must be handled with care. The blocks then must be covered with additional tarps, and it is strongly recommended that they be generously watered twice daily. Testing of Blocks Before blocks are used, it is important that they are first tested to ensure they are of satisfactory quality. Much like in soil testing, these tests fall into both qualitative and quantitative categories. Qualitative Page
22 Internal Texture Examine the internal texture and coloring of broken blocks. Soil fractions should be evenly distributed, and the color should be homogenous throughout. If not, a more thorough mixing effort is needed. External Texture The characteristics of dried ICEBs should be compared to those listed in Table 8. Corrections to the soil mixture can then be made to improve block quality. External Resilience Brush the block with a metal brush using an equal force and number of repetitions. In the second test, jab a sharp tipped tool into the block face. Examine the surface. Acceptable limits should be set for a block’s intended use (Rigassi, 1995). Figure 13‐ External Resilience
Table 8: Dried Block Characteristics Block Characteristics Possible Cause Remediation Smooth, strong, but with cracks Too much clay content Add more sand to block mix Rough, no cracks, brittle Too much sand content Reduce amount of sand or add additional fines Smooth, no cracks, not brittle, strong Good block None Dimensional and Crack Tolerances The following tolerances are for non‐interlocking CEBs (Boubekeur et al., 1998). Because ICEBs are laid without mortar, the blocks are especially sensitive to dimensional differences in height and length and require stricter tolerances. +1 to ‐3 mm for length +1 to ‐2 mm for width +2 and ‐2 mm for height Additionally, the difference between any two CEBs should not exceed: Page
23 3 mm in length 2 mm in width 3 mm in height Cracks are not tolerated on surfaces exposed to water. On covered or protected surfaces, cracks may not exceed the following: .5 mm in width 20 mm in length 5 mm in depth 2 in number per face Quantitative Testing Different building codes and authors recommend various compressive strength requirements from CEBs. This manual is aiming for compliance with the Australian building code, considered to be the most strict of all CEB codes, which requires that 95% of blocks test at a compressive strength >2.0 MPa (Heathcote, 1991). Minimum saturated strength should be at least 1.4 MPa (Fitzmaurice 1958). Given the high compressive forces needed to fail a single ICEB, it is unlikely that such a test can adequately and routinely be performed in the field. The following two tests are proposed for further investigation as potential methods of field testing for ICEB compressive strength. Three Point Bending This test has been recommended as a simple method for indirectly testing compressive strength of CEBs. In the test, the ICEB is loaded at its mid‐span and then the flexural modulus of rupture is then determined by assuming pure bending. However, due to the relatively short span of the block, arching action may occur thus invalidating the pure bending assumption. The following equation (Morel et al., 2007) accounts for this arching action: 1
4
2
Where: equivalent compressive strength P failure load L span between the two roller supports e block height l block width Page
24 h0 characteristic height For testing of ICEB blocks, the block width l should have the grout holes subtracted out. The characteristic height for typical CEBs is 23 mm, but preliminary testing must be done to calibrate for the ICEB’s irregular geometry. Advantages: Relatively easy procedure for testing after apparatus is constructed. Disadvantages: Concrete‐based materials behave less predictably in tension; results need to be calibrated specifically for CVBT‐ICEB block geometry. Compression Testing For this test, a sample is carefully cut out of the ICEB and then tested in compression. Advantages: Test is direct compression. Disadvantages: Issues with successfully removing sample and loading it normally, different aspect ratio. Improving Strength If blocks are of insufficient quality, some or all of the following steps can be taken to improve block quality. Crush the clay clumps more thoroughly. Spend more time both wet and dry mixing. Decrease mix size to reduce retention time. Increase density by compressing heavier charges. Improve the curing process, either by keeping the blocks wetter, letting them cure longer, or both. 6. Increase cement content. 7. Alter relative grain fractions, or select a new soil source. Page
25 1.
2.
3.
4.
5.
STRUCTURAL DESIGN Footings Dimensions Use Table 9 below for determining the required footing dimensions of a 1 story ICEB building. Table 9: Selection of footing dimensions Allowable Foundation Pressure* (kPa) Footing Width (cm) Gravel or Sandy Gravel (GP, GW) 144 30 Sand, silty sand, clayey sand, silty gravel, or clayey gravel (SW, SP, SM, SC, GM, GC) 96 45 Clay, sandy clay, silty clay, clayey silt, silt, or sandy silt (CL, ML, MH, CH) 72 60 Not suitable ‐ Soil Material Class (USCS) Mud, organic silt, organic clays, or peat (OL, OH, Pt) *(International Building Code, 2006) Footing Material Cyclopean Concrete Cyclopean concrete is not recommended for use in seismic areas due to difficulties with tying in reinforcement. Compressed Earth Blocks CEBs are not recommended for footing construction. If there is no other alternative, a CEB foundation should only be used in the most arid of climates, and a base concrete slab is highly recommended. Page
26 Reinforced Concrete Reinforced concrete has the best performance of all footing materials, and is highly recommended for earthquake regions. See Figure 14 for the design. For this design, a spread footing will be cast in the ground. See Footing Construction on Page 27 for construction. Figure 14: Reinforced concrete spread footing detail. Height and width of footing should be at a 1:2 ratio. * This (9 cm) is an approximate measurement so that the middle bar is centered Layout In seismically active regions, the layout of a structure must be based off simple and symmetric shapes to provide stability during shaking. For simplicity purposes, this manual focuses on a modular design layout with exterior dimensions of 4.2 m by 4.2m, including the corner columns. To make a larger dwelling unit, there are two options. First, this module can be reproduced and constructed separately next to each other, without touching. Acceptable layouts using this method can be found in Simple Form and Symmetry of the Design Considerations in the Seismic Design Chapter on Page 43, Figure 39. Secondly, an exterior wall of one module can be used as an interior wall of a larger structure by adding a door and another room with the same dimensions and reinforcement detailing as the standard module. Acceptable layouts using this method can be found in Simple Form and Symmetry in the Seismic Design Chapter on Page 44, Figure 41. Footing Construction Digging the Trench After the building layout has been determined, the next step is to dig the trench for the footing. Page
27 Necessary Equipment: Tape measure, wooden stakes, lumber (multiple 50x25s or 100x50s), screws nails, string, plumb bob, spray marking paint, and a hand level. Dimensions of the Perimeter The corners of the layout must first be marked by driving stakes into the ground. For a square module, the dimensions of the four sides must be measured out to determine where to drive in the stakes. It is important to keep in mind that these stakes will mark the outside edge of the footings rather than the outside edge of the walls themselves. To account for this, the distance that should be added to each side at the corners is: – ½ 2
For example, if the footing is 60 cm in width, the length added to each corner is: 60 7.5 2
22.5 This means that the outer trench dimensions would be 45 cm longer than that of the outside wall. Making Square Corners and Straight Sides Ensuring accurate alignment is crucial to avoid stress concentrations caused by non‐uniformity. Even what may seem like insignificantly small errors can become multiplied as construction progresses. To help prevent this, the use of batter boards are employed. Making Batter Boards 1. After the appropriate outside footing dimensions has been determined above, measure out the approximate corner locations and mark them with a stake. These are called the perimeter stakes. 2. Drive four more stakes to outline the corner, two on each side, as seen in Figure 15: Batter boards are placed 1 m away from the exterior corner Figure 15. These four stakes should be of footing perimeter to aid in tying the perimeter line strings. about 1 meter away from the perimeter stake, as well as 1 meter apart from each other. 3. Screw two 50X25s (2X1) or 100X50 (2X4) across the stakes to complete the batter boards, making sure they are level with a hand level. • Note: The batter boards do not need to be perfectly square. 28 Nails tacked on batter boards
Figure 16: Strings are pulled between the nails on the batter boards to outline the perimeter of the footing. Page
Using Batter Boards 1. Suspend a plumb bob over the marked perimeter stake 2. At that corner, locate one of the two sides of the footing perimeter that make up the corner. As if you are extending that side past the corner, follow it until it meets the batter board at a perpendicular angle. Tack a nail on the batter board at this point. See Figure 16. 3. Repeat Step 2 for the other side that makes up the corner. 4. Repeat Steps 2 and 3 for each corner of your layout. 5. When all nails are in place, pull string between all exterior points to outline the perimeter, as seen in Figure 17. 6. Square up the sides using the Diagonal Method. Diagonal Method Measure the diagonals and adjust the string lines until
both the diagonals are equal. For the foundation to be square, AB = CD. The sides should be checked as well to make sure AD = CB and AC = DB
Figure 17: The diagonal method measures the diagonals of an enclosed rectangle
Page
29 Marking the Final Perimeter 1. Suspend a plumb bob from intersecting strings at a corner such that the plumb bob rests just above the ground surface 2. When the plumb bob is steady, drive a nail into the ground at this point. 3. Repeat Steps 1 &2 for all building corners. 4. Tie a string between the nails just above the ground surface signifying the building perimeter. 5. Following these string lines, use spray paint to mark the perimeter on the ground surface. This should be done carefully to ensure square and straight lines. An alternative to spray paint is a chalk line. Pull the chalk line string out between the two nails instead of the string lines. Once secured, pull the string up about 5 or 6 inches to snap it once on the ground – it should leave a chalk line directly below the string. Make sure the line ends at each of the nails. 6. Remove the string from the nails and batter boards and repeat the process for the inside perimeter of the footing, measuring the width of the footing from your chalked line. 7. Once all strings are removed, begin digging the footing trench just along the inside of the marked footing perimeter. If using the cyclopean footing, dig the trench to the depth of the footing. If using the reinforced concrete footing, dig the trench to a depth of 8 cm above the top of the footing to accommodate the formwork. Make sure to shovel the dirt to the outside of the perimeter. Vertical Reinforcement Design The vertical reinforcement for the walls will be cast directly in the footing, so the spacing must be determined beforehand. The spacing and layout of the vertical reinforcement is determined specifically to withstand earthquake shaking, and the design can be found in Reinforcement Section of the Seismic Design Chapter on Page 47. Page
Tying Spliced Reinforcement Rebar is more manageable, the bars can be spliced to shorter lengths. Avoid splicing within the first third of the length of the wall. To tie spliced longitudinal reinforcement together within the footings, the bars should overlap a distance of at least 40X the bar diameter (Hausler, 2009). Overlapped bars can be welded or tied with a wire tie as seen in Figure 19. Spliced bars should bend around corners in an L shape and extend into the next wall by a length of 40 times the bar diameter (40db). The bent length 30 Laying Longitudinal Reinforcement The longitudinal reinforcement must be suspended above the ground about 5 cm to ensure that it is covered with enough concrete to prevent rusting. To do this, concrete spacers are used. Concrete spacers are cubes or disks of concrete that are 5 cm thick to represent the 5 cm clearance of concrete from the bottom edge of the footing. See Figure 18. The spacers are cast with two wires in the center to tie around the rebar to hold the spacers in place while pouring. Position the spacers along the bottom of the formwork, three at a time along the width of the footing at the same location of the three reinforcement bars in Figure 14 (See Figure 18). Two will be placed 5 cm from the edges, and one in the middle. Spacers should be laid every 1m along the length of the wall. Figure 18: Spacers are placed in the form work to hold the rebar should overlap with and be tied to the longitudinal bar in that wall as seen in Figure 20. For T‐sections where an interior wall meets an exterior wall at a perpendicular angle, see Interior Walls on Page 35. Figure 19: Splicing options Figure 20: Illustrating continuous horizontal reinforcement around corners Page
31 Laying Vertical Reinforcement Vertical reinforcement will be cast in the spread footing and hooked around the middle longitudinal bar as seen in Figure 21 so that it is centered in the reinforcement hole in the ICEBs. If possible, the wire ties in the concrete spacers should be tied around the vertical rebar as well. Use short lengths of vertical reinforcement initially so you will be able to reach the top to slide a channel block over the top for the base of the wall. It is possible to lengthen the bar later. cast. Page
Set up two stakes and lean them from opposite directions against a vertical reinforcement bar to make a teepee shape. Tie the stakes together at the top to the rebar to make a tripod to hold the bar straight and erect as seen in Figure 22. Channel blocks will be slid onto the vertical rebar from the top once the footing has been cast. Ensure that you can reach the top of the vertical reinforcement to slide a channel block over the top before pouring the footing. If it is too long, untie it from the concrete spacers and cut it shorter until you can reach the top as seen in Figure 22. If cutting is too difficult, the rebar can be bent at a 90 degree angle at a reasonable height and the block slid on this way. The rebar will be bent back after the blocks are stacked to the bend. If the rebar is cut, the rebar can be extended later by one of the three methods pictured in Figure 19. Figure 22: Vertical rebar should be cut to a height that is easily reached to slide a block over the top. Blocks are added after footing is 32 Figure 21: Vertical reinforcement tied in to the reinforced spread footing. * This is an approximate measurement – the middle bar should be centered. Mixing Concrete to Pour Prepare a concrete mixture with the ratios 1:2:4, 1 part cement, 2 parts sand, and 4 parts stone dust (.5 cm) (Wheeler, 2005). Measurements are 25 kg of Portland cement, 6 buckets of sand, and 12 buckets of stone dust. Water is a tricky ingredient ‐ the mixture should be workable so that it can pour easily but not too runny so that it loses its strength. Add water a little at a time until it is workable. Only add more water if the mixture cannot easily pour and do so in small amounts until it is workable. Pour the concrete in to the form work slowly to avoid air pockets and shifting of the rebar. All reinforcement should be covered except for the vertical bars sticking out of the footing. Internal reinforcement should never be exposed! Scrape any excess concrete off the top of the form to make a level surface for stacking the channel blocks as the base of the wall. Ring Beam at Base of Wall Channel blocks with horizontal reinforcement and concrete will be used as the first layer and will be tied to the vertical reinforcement from the footing (See Figure 23). This is called a ring beam. A two cm layer of rich mortar will be used as the bond between the blocks and the footing as seen in Figure 21. Cement should be sprinkled on the exposed areas of mortar once the channel blocks are in place to seal the mortar. Mortar mixture has ratios of 1:3, 1 part cement, and 3 parts sand (Wheeler, 2005). Water should be added until the mixture is workable but can be molded so that the height will remain at 2 cm without any slump. Remember to use channel blocks with one open dowel to slide over the vertical reinforcement. Horizontal Reinforcement Horizontal reinforcement will be one D12 bar centered in the channel as seen in Figure 21. It will be laid and positioned using a procedure similar to the one detailed in Laying Longitudinal Reinforcement on Page 30. Where the horizontal rebar meets the vertical reinforcement from the footing, a wire tie should be used to bind the two together. Same overlapping and bending rules apply for the horizontal rebar as for the longitudinal rebar in the footing. See Tying Spliced Reinforcement on Page 30. Figure 23: A layer of channel blocks with horizontal rebar will be placed on top of the footing. Page
33 Mixing and Pouring Concrete Use same mixing ratios as in Mixing Concrete to Pour. Pour carefully along the channel so that it completely fills the dowels with the reinforcement as well as the channel so that all reinforcement is covered. Scrape off any excess concrete at the top of the channel to make a level surface with the top of the blocks as seen in Figure 23. It is important to pour all of the reinforced concrete in the same layer at the same time to ensure simultaneous drying. If you run out of concrete in a layer and have to make more, that concrete may dry before you can pour the rest, resulting in a cold joint. Cold joints must be avoided to ensure structural soundness, so plenty of concrete should be made beforehand. 1 mix will fill 40 linear meters of channel blocks. Walls
2.5 meters high (25 blocks) and 3.6 m long (12 blocks). Including columns the length = 4.2m. First Layer Next the standard ICEB blocks will be laid and aligned for the base layer of the wall. It is important to ensure accurate alignment to avoid stress concentrations. Even what seem like insignificantly small errors may become multiplied as construction progresses. Accurate Alignment (Wheeler, 2005) 1. Lay corner blocks first, make sure they are square, and pull a line between them. Lay the blocks in between along this line. 2. Use batter boards and string similar to the method for laying out the trench perimeter. Lay blocks along the line of the string 3. Compare blocks to ensure all blocks are of the same dimensions 4. Use nails to make up extra height for any short blocks. Let the grout fill in around the nails and then pull them out. Figure 24: Use nails on top of short blocks to raise the next layer so that it is level. Use nails with different diameters for different sized blocks. Page
Horizontal reinforcement Channel blocks with reinforced concrete should be laid every 7 blocks in height, and will be sufficient for earthquakes (Hausler, 2009) 34 Openings Channel blocks with reinforced concrete must be laid at the base and top of all openings. To make this easy, all windows should start in the 9th layer of blocks so the 8th layer will be a continuous layer of channel blocks at the base of all window openings and will also act as the first layer of horizontal reinforcement. The windows will then be 7 blocks in height so that another continuous ring beam can be laid along the top of all the windows. Use planks of wood and sticks to support the opening as the concrete dries as seen in Figure 25. To tie horizontal reinforcement within the ring beams see Tying Spliced Reinforcement on Page 30. Window openings should not be more than 1.2 m, or 4 blocks, wide. * Vertical reinforcement should also be used in the dowels on either side of the windows as seen in Figure 25. For details on this design, refer to the Reinforcement section on Page 47. Figure 25: Horizontal and vertical reinforcement must outline the openings. Tying to Vertical Reinforcement Every time a layer of channel blocks is laid, the horizontal rebar should be tied to the vertical rebar with wire ties or welds. Concrete Mixing and Pouring For concrete mixture and horizontal pours, see First Layer on Page 34. For vertical pours, the same mixture will be used but a new procedure will be applied. Vertical pours should be made at the same time as the channel blocks are filled, so every 8th layer of blocks. A reinforcement bar of a smaller diameter should be moved up and down in the hole as you pour to help the concrete reach the bottom of the dowel channel and to get rid of air bubbles. The concrete for the channel should be poured just after the rebar holes are filled so all the concrete dries at the same time. After pouring for the entire structure is done, water the wall 3 times per day for three days. Page
35 Interior Walls Tying interior walls into an exterior wall is important to ensure continuity. There are two acceptable patterns, the first being ideal. The second should be used if the intersecting interior wall is laid after the exterior wall and it is impossible to lay a block within the exterior wall as seen in Cobra (Wheeler, 2005). Option 1 – Cobra Pattern Figure 26: Cobra ‐ This pattern starts with a block laid so it is intersecting an exterior wall Option 2 – Peacock Pattern Figure 27: Peacock ‐ This pattern starts with a block laid against the edge of an exterior wall Page
Figure 28: T intersection 36 Tying Reinforcement To tie reinforcement at T intersections, it is ideal for the horizontal reinforcement coming from the exterior wall to bend in at the T intersection and continue to be the horizontal reinforcement for the intersecting interior wall as seen in Figure 28. The horizontal reinforcement from the exterior wall from the other direction would then bend in an L shape to overlap with the interior wall reinforcement. The same overlapping rules apply as stated in Tying Spliced Reinforcement on Page 30. As an alternative to this method, if the Peacock pattern is used, the horizontal reinforcement from an interior wall will bend in an L shape to overlap with the reinforcement along the intersecting exterior wall. Again, the same overlapping rules apply. Ring Beam Channel blocks are used along the perimeter of the top of the structure. By filling the channels with reinforced concrete, a ring beam will be formed that will tie all the walls together. Tying the Ring Beam into the Walls Bend corner vertical rebar in an L shape to lie in channel blocks and tie to horizontal rebar in ring beam. For overlapping and tying rules, see Tying Spliced Reinforcement on Page 30. The vertical rebar along the length of the walls will stick out into the ring beam and hook to the horizontal rebar in the channel as seen in Figure 29. Figure 29: Vertical rebar from walls hooks in to ring beam. Tying horizontal reinforcement See Tying Spliced Reinforcement on Page 30. Page
37 Pouring concrete Follow the mixing and pouring procedures under Mixing and Pouring Concrete section on Page 33. It is important to mix enough concrete to complete pouring the ring beam. If you run out, and have to make more, this could result in cold joints. An incomplete ring beam results in cold joints and an overall structure that is not safe. Make sure there is concrete at the connections so the entire ring beam is continuous. Avoid inaccurate mixture ratios that result in poor quality concrete. Roof Design – Timber Truss 38 Figure 31: Truss Design for a wall length of double the standard (8.4m). See "Construction" on Page 40 for details on truss connections Page
Figure 30: Truss Design for a standard length wall (4.2 m). See “Construction" on Page 40 for details on the truss connection. Figure 32: Truss connection Detail B with M19 bolts
Figure 33: Truss connection Detail A with M19 bolts These trusses should be evenly spaced along the length of the exterior walls as seen in Figure 34. Fastening to the ring beam can be seen on Page 40. Figure 34: Illustration of roof truss spacing along shear wall Page
39 Construction A good quality hard timber should be used for the roof truss (timber class I or class II is good) (Hausler, 2009). Use 100X100 members (4X4). Tight connections should be made at the joints with no spaces between the timber members. Fasten truss joint connections with bolts (19mm), using a steel plate when two or more members come together as seen in Figure 35. Figure 35: Fasten truss connections with bolt, bridge washer, and steel connection plate. Nails are not strong enough for truss connections (Hausler, 2009) Roof Attachments It is not acceptable to use the vertical rebar in the corners of the walls to tie the roof truss to the ring beam. The vertical rebar should be used to tie the ring beam to the walls so there is a solid connection, and to avoid corrosion from exposed rebar. The truss will be anchored directly into the ring beam with the use of M19 threaded rods. Page
Figure 36: Illustrating the lower cord anchoring to the top of the shear wall 40 Anchoring procedure Size M19 threaded rods should be cast into the ring beam concrete at a spacing of 1 m, only along the two shortest parallel exterior walls. The distance of the first rod from the edge of the wall should be determined so that the set of rods is centered. For example for a 4.2 m long wall, the spacing of the first rod will be 10 cm as seen in Figure 36. Then while making the truss, the base beam should have drilled holes every 1 m along the beam to match up with the location of the threaded rods. Place the beam on top of the ring beam so the rods insert into the drilled holes. Tighten bolts and bridge washers down on the rods to secure the wooden beam to the ring beam. Gable Wall ICEB blocks should not be used in the gable wall. These will easily crack and collapse in an earthquake since there is no bracing or support. Instead, use an economical and simple alternative. This would include any light‐weight material like timber, corrugated steel (CGI) sheet, or calciboard. Figure 37: Calciboard is a cheap and easy alternative for the gable wall (Hausler, 2009) Roof Cover A CGI sheet should be installed on top of the truss using screws directly into the wood. This will help direct the rain water through the metal channels, off the roof, and away from the walls of the house. Use a CGI sheet of 2 mm minimum. If necessary, a softer thatched overlay can be laid on top of this to dampen the rain. Page
41 Figure 38: Make sure the CGI sheets are installed so the grooves line up, creating continuous channels (Hausler, 2009) Seismic Design Page
42 It is not known for certain whether the current design and construction practices of ICEB buildings are adequate for use in highly seismic regions. However, after carefully investigating and comparing other earth structures to the current ICEB design, there is some indication that they may not be sufficiently designed for high level earthquake performance. The information in this section is presented in three subsections: • General Design Consideration for Earthquake Forces The presented considerations are not reliant on future research and have been proven time and time again and maybe regarded as “commonsense”. These considerations are extremely important in masonry design, but they also hold in more general cases. Following the guidelines laid out in this section will allow for a simple yet fundamentally necessary structural design. • Seismic Design Example Procedure Currently the seismic design procedure for ICEB structures is incomplete. However, this section lays out a method that will be utilized upon acquiring further ICEB data from future shear wall testing. • Failure Modes of ICEB Structures This final section addresses failure modes of other earth and masonry structures. The exact failure modes of ICEB structures remain unknown, but it is reasonable to suggest the possibilities and make predictions which can be confirmed after shear wall testing. Little is known about the actual behavior of ICEB structures due to the lack of research and observation of behavior in seismic regions. The following three subsections serve to be a road map for a future comprehensive ICEB seismic design section. Due to the uncertainty that currently exists with ICEB technology, the following recommendations can, for the time being, only be considered estimates and predictions. Additional testing remains necessary for any specific ICEB design recommendations to be stated with certainty. General Design Consideration for Earthquake Forces Simple Form and Symmetry “It has long been acknowledged that the configuration, and the simplicity and directness of the seismic resistance system of a structure, is just as important, if not more important, than the actual lateral design forces.” ‐ William Holmes, structural engineer The implementation of simple form and symmetry into a building begins at the layout stage of design. The various aspects of simplicity and symmetry should be addressed in both vertical and horizontal fashions. In ICEB design these aspects can be addressed easily. Design should be done using simple plan layout. Plan layout simplicity can be ensured by choosing a standard symmetric design, such as a square or rectangular plan layout, and using this standard design on different scales to piece together more complicated plan layout designs. Figure 39, Figure 40, and Figure 41 illustrate this concept and can be found below. Being able to design more complex layouts with smaller substructures requires precise information on deflections, and is important in order to provide gaps avoiding any battering contact between substructures. Figure 39: Techniques for accommodating complicated layouts (x = long wall dim; y = short wall dim) Page
43 Figure 40: Good structure layouts (x = long wall dim; y = short wall dim) Figure 41: Correct wall opening and mass distribution (CG = center of gravity; CR = center of rotation) Figure 42: Cross hatching represents the continuous load path that will deliver forces exerted on the structure to the foundation Page
44 Following Through with Load Transfers In order for a structure to be sound in a seismic event, there must be a clearly designated load path to direct all structural forces into the foundation. Using rebar and common practice construction techniques for tying structural elements together, the perimeters of the walls and the corners of the structure can be strengthened to ensure that loads are distributed to the foundation. These practices include development length, splicing, and bar diameter criteria. Further details for reinforcement can be found in the Tying Reinforcement discussion in the Structural Design section of this manual. An illustration of the continuous load path found in an ICEB shear wall can be found in Figure 42 below, which illustrates a basic wall design 2.5m X 4.2m. Bond and Anchorage Wall­Foundation The interface between the first layer of blocks and the foundation is crucial. This location will experience the highest lateral forces of any location on the structure, making it very important to attain minimum block strength and also sufficient anchoring to the foundation. The method of anchoring must be capable of transferring lateral loads to the foundation. Current ICEB designs are anchored by rebar being cast into the foundation at the ends of the walls and the first layer on blocks being set on a bed of rich mortar. The purpose of the mortar is waterproofing, to prevent the blocks from absorbing water. It is recommended to add additional rebar anchoring points to the interior span of the wall. Anchoring into the foundation will occur as often as vertical reinforcement appears in the walls, because it is simply an extension of the vertical reinforcement that has been cast into the foundation. Details on the actual spacing of the vertical reinforcement can be found in the following discussion on Reinforcement. Figure 43: Roof connections that leave too much uncertainty about earthquake performance Page
45 Roof Current ICEB structures being built in Thailand have roof‐structure connections that may be insufficient, and there is good reason to doubt the capacity of the designs in other regions under earthquake loading. Forces from the roof connections are concentrated locally in the ring beam via the reinforcement that has been cast into it. The roof is attached to the rebar protruding from the ring beam with a bracket or weld. These poor connections make the roof susceptible to the failure of detachment. The proposed roof connection has been more properly specified with a bolt anchoring system that is cast into the top ring beam, allowing the horizontal beam of the timber truss to be mechanically fastened to the top of the wall. An illustration of a roof‐structure connection can be found in Figure 36. Wall Aspect Ratio Wall aspect ratio, the ratio of wall height to width, must be considered during structural design. From past shear wall tests, it has been observed that as the aspect ratio of a shear wall increases the failure becomes more ductile (Booth and Key, 2006). A wall with a low aspect ratio fails with the most contribution coming from shear failure, making failure brittle. Table 10 below illustrates the decrease in percent contribution to failure from shear as wall aspect ratio increases. ICEB shear walls will first be tested with an aspect ratio of 1, it is reasonable to expect a brittle failure at maximum capacity. From the information acquired during testing, it can be determined whether or not ICEB design shall be catered to brittle behavior, or if more ductility can be introduced into the system with different wall or reinforcement orientations. Table 10: Decrease in percentage deflection due to shear Aspect Ratio
h/L
0.25
1
2
4
8
Percentage Deflection Due to Shear
Cantilever Wall
Fixed End Wall
92
98
43
75
16
43
5
16
1
4.5
Redundancy “Historically the majority of deaths in earthquakes have been caused by small houses collapsing on their occupants. Thus, complacency is not warranted when dealing with small‐scale buildings.” ‐ Tony Gibbs Avoiding catastrophic failure is truly a motivation for this manual. In order to ensure occupant safety, ICEB structures must be designed with redundancy. However, the simplicity of ICEB structures limits the capacity to which redundancy can be built in. The two locations which most require redundancy are at the roof‐structure interaction and the base‐foundation interaction. Both locations require additional and proper anchorage. Page
Similarly, the base of all structural walls must be sufficiently anchored to the foundation in order to avoid detachment. This may also be addressed with additional anchors at regular intervals, foundation anchors will be placed as often as vertical reinforcement appears in the wall. Original ICEB structures only had a rebar tie‐in to the foundation at each wall end with mortar beneath the first row of blocks. 46 At the roof, it is important that the timber truss not detach from the ring beam and batter the structure. To minimize this possibility, it is necessary to anchor the roof to the ring at regular intervals, using approximately 1 anchor/meter of wall, which can be seen in Figure 36. Ductility “Ring beams at various levels, which are linked together with vertical ties, will reinforce the structure very well and make it ductile.” – Auroville Earth Institute Reinforcement Reinforcement details are important and should never be overlooked. Failures of rebar connections, splicings, and ties are easily avoidable if proper procedure is followed. U.S. masonry design code limits lap splicing to use on rebar less than 36mm in diameter. Therefore, all methods of splicing may be used within the ICEB structure because the rebar will never approach the 36 mm size. The size of rebar ( ) within the structure is limited by the grouted channel width ( ) (Rosenblueth, 1980). /4 Reinforcement plays a large role in overall safety, because preventing total collapse of a structure relies upon a designer’s use of the steel’s ductility to prevent a brittle failure. The following guidelines should be followed to help ensure that the reinforcement in the structure is utilized properly: • Reinforcement shall be continuous around all corners and through intersections (Lindeburg and Baradar, 2001). • Reinforcement must be placed in all 4 dowel holes of the blocks forming the pillar‐like portion of the wall at the structural corners. Because the corners are high stress locations and are vulnerable to the failure depicted in Figure 50 . • 12 mm may be used for vertical reinforcement at corners, wall intersection, or around openings. •
No splicing of rebar is permitted in locations where plastic hinge development (possible blowout) is expected, such as at the end of walls close down to the foundation. •
Since wall height (2.5 m) is over the height for walls requiring only corner reinforcement (2.4 m). Spacing is suggested 1.65 m and would be equal for a wall length of 3.3 m. A spacing of 1.2 m must be used for ICEB construction with the intent of being conservative The spacing of vertical rebar will not always work out to be assigned where a rebar dowel exists in a block. When this happens, favor support of the middle of the wall because the wall ends already have a conservative amount of rebar specified. To determine that frequency of vertical rebar, divide the length of the wall by 1.2m, disregard the remaining value, and evenly space the number of vertical rebar locations calculated. Page
47 The ICEB design is relies on the experience of the Auroville Earth Institute, and is utilizes the design concept of tying rings beams at multiple levels together using vertical rebar in order to introduce ductility to the design. Additionally, the vertical rebar tying together the rings beams is developed into the foundation, serving as added wall anchoring. Seismic Design Example Procedure Below is a comprehensive procedure for analysis of an ICEB shear wall. It is important to understand that this is only an example model of how the procedure may appear, and thus may be substantially refined after completion of the shear wall testing. The current design may be best described as a structure with a confining frame around a reinforced infill wall. Determining the response modification coefficient and overstrength factor are not possible at this time. Both the response modification coefficient and the overstrength factor require significant judgment and knowledge of existing structure’s behavior during seismic activity. Once again, it is hoped that future shear wall testing designs will allow for determination of the design coefficients the ability of designers to increase ICEB redundancy and optimize the elements participating in lateral force resistance. Below are the steps of an example design procedure that have been adopted from FEMA‐450, which is a publication in the United States and is not expected to accompany this design manual (FEMA, 2003). 1. The Seismic use group depends on the type of structure and the degree of public hazard. There are three category options. Group III consists of structures having essential facilities that are required immediately after an earthquake. Group II consists of structures that pose a significant public risk due to occupancy. Group I contains all structures that are not categorized as II or III. Due to the efficiency of block production and the small amount of information for ICEB behavior, it is not projected that ICEBs should be used for Group II or III structures. An ICEB home will always be category I. 2. The seismic use group is used in order to determine the occupancy importance factor. This value is chosen from the table below, but will always be 1 for an ICEB home. Table 11: Occupancy factor based on seismic use group 3. Soil at the site chosen for construction must be identified. Potential sources for classifying the site’s soil include soil science maps, hydrologic and rainfall data, and geologic surveys. If the resources are available, a standard penetration test may be used in an attempt to correlate hammer blows to soil strength. Figure 44 illustrates the test setup. N is the number of hammer blows it takes to drive a split‐spoon sampler 45 cm into the ground. The hammer must weigh 68kg and be dropped through a distance of 76 cm. Getting an estimate for the N value of the soil will allow for choosing between classes C – E. If the number of blows is substantially more than 50, it is recommended to make a conservative estimate and design for class B soil. If soil data is 48 I
1.0
1.25
1.5
Page
Seismic Use Group
I
II
III
not readily available and the resources are not attainable to administer an SPT, choose soil class D for design. Soil class can be chosen from Table 12 if soil parameters are known. Table 12: Site soil classes Soil Classes Description
Shear Wave Velocity (m/s)
Blow Count, Nu Undrained Shear Strength, Su (kPa)
Hard rock
> 1500
Rock
760 ‐ 1500 Very dense soil and soft rock C
360 ‐ 760
> 50
Stiff soil
D
180 ‐ 360
15 ‐ 50
Any soil profile < 180
E
<15
* Or soft clay defined as soil with PI > 20, w ≥ 40 percent, and su < 25 kPa
A
B
> 100
50 ‐ 100
<50*
Site Class F is not advisable for building and is described as: Site consisting of liquefiable soils, highly sensitive clays and/or collapsible, weakly cemented soils. The method for accommodating this site class is avoidance, ICEB structures shall not be built in these locations. The discussion of site classification under Design Considerations describes soil found with a site class F and the reasons it should be avoided. Figure 44: Standard penetration test setup Page
49 4. Determine 0.2 sec and 1.0 sec period accelerations for the maximum considered earthquake (MCE) in the region that has been chosen for construction. A resource for attaining these values is the Global Seismic Hazard Map or the USGS earthquake hazard maps. 0.2 sec
1.0 sec
5. After determining the site classification designation and the MCE accelerations, use Table 13 and Table 14 below to determine site coefficients, and . Table 13: Values of site coefficient Fa Page
50 Table 14: Values of site coefficient Fv 6. Use the site coefficients determined in Step 5 to adjust the accelerations to be site specific values. This adjustment considers both the earthquake history of the region and the specific properties found at the construction site. 7. Adjust the mapped accelerations for design by using the following equations. 2
3
2
3
8. Choose the seismic design category based on the spectral accelerations, SDS and SD1, and seismic use group from the tables below. Table 15: Seismic design category based on SDS 9. & 10. Steps 9 and 10 can be essentially one step but are considered two in order to avoid omitting any critical design considerations. Both plan and vertical structural irregularities must Page
51 Table 16: Seismic design category based on SD1 be addressed in order to avoid eccentric structural motions and forces in the event of an earthquake. Plan irregularities include: Torsional A torsional irregularity is caused when an eccentricity exists in the plan layout. This eccentricity can be attributed to poor mass distribution, re‐entrant corners, and/or non‐parallel systems. Figure 41 gives a good illustration of mass and layout symmetry that avoids a torsion irregularity. Error! Reference source not found. below illustrates a couple of options for parallel and non‐parallel layout. It is always advisable to avoid the non‐parallel layout options. Figure 45: Non‐parallel vs. parallel layouts (FEMA, 2003) Re‐entrant Corners Below is an illustration of re‐entrant corners. If the ratio of the short wall dimension, A, to the long wall dimension, L, is greater than .18‐.20, the design may be considered to have re‐entrant corners. Re‐entrant corners are a specific potential cause for torsion and unknown concentrated stresses. The reason for the torsional behavior and stress concentration is the difference between the wings of the structure and its core. Figure 46: Parameters for determining whether a layout has re‐entrant corners (Auroville Earth Institute) Page
52 Vertical irregularities do not apply to a single‐story ICEB structure but are a topic of further ICEB design development. 11. “The blocks make load bearing walls.” – Geoffrey Wheeler The structural system type of an ICEB home is a bearing wall. 12. 13, & 14 These three steps consist of determining the response modification coefficient, overstrength factor, and the deflection amplification factor. The reduction modification coefficient relies on the energy dissipation capacity of the structure under cyclic loading. The greater the structure’s capacity to dissipate energy, the larger the value of R that may be used in design. The energy dissipation resulting from hysteretic behavior can be measured as the area enclosed by the force‐deformation curve of the structure as it experiences several cycles of excitation. Figure 47 below illustrates a ductile response hysteris and a less ductile response, or pinched hysteris loop (FEMA, 2003). Figure 47: Hysteresis loops from cyclic loading (FEMA, 2003) As the R value increases the design loads may be decreased from those that are originally calculated based off the ground motion. Page
53 The overstrength factor may be solved for using the below equations once the R values are attained. Typical overstrength values for both bearing walls and reinforced infill walls fall between 1.5 and 2.5 (FEMA, 2003). It is unknown as to where the value for the actual behavior of an ICEB wall will fall until shear wall testing is complete. The values of the amplification factor may be measured from a similar plot, to the one pictured below, correlating to the actual wall behavior. Figure 48: Relationship between lateral seismic force and deflection and the factors necessary for determining design loads ‐ Ductility reduction factor Ω
Page
54 15. This step consists of determining whether or not there is a system or height limitation associated with the type of design chosen. There is no limitation associated with a one‐story ICEB design. However, as ICEB technology advances to taller structures and more advanced uses, it will be important to determine a valid correlation between ICEB bearing wall behavior and another type of bearing wall behavior. Knowing how an ICEB bearing wall correlates to another type will allow for more understanding of possible necessary system and wall height limitations. System correlations will be able to be established with the knowledge of R, Ωo, and Cd and how those values compare to already established ones. Additionally, certain ICEB design systems may be inappropriate for use on certain site classes. Shear wall testing and acquisition of factors will be a great gain for further understanding of this step in the design. 16. For a single‐story ICEB structure, the redundancy factor is 1.0. For future designs that may expand beyond one‐story and dwelling type use, the design must fulfill certain criteria. If the seismic design category assigned to the site is D, E, or F, the design must satisfy the following criteria in order for the structure to be 1.0, otherwise it is 1.3. Removal of shear wall or wall pier with a height‐to‐length‐ratio greater than 1.0 within any story, or collector connections thereto, must not result in more than a 33 percent reduction in story strength, nor create an extreme torsional irregularity. Design in seismic design categories B and C always have a redundancy factor equal to 1.0. 17. Determine the approximate fundamental period of the structure. A sample calculation of the fundamental period can be found in the Appendix B. 18. Determine seismic dead weight by calculating the number of blocks that complete a portion of wall, multiply it by the charge mass (~8.2kg), then multiply it by the acceleration of gravity (9.81 / ). An estimation of rebar mass per linear foot and an estimation of roof weight are also necessary. Example: Determining dead weight of a solid (no openings) wall of dimensions 4.2m x 2.5m. Weight from blocks: 359 Weight from reinforcement: 31
8.2
2870 .
28 Weight from Roof: Depends of roof dimensions Page
55 9.81
19. Determine the value of CS (seismic response coefficient) to be used in calculating the base shear. ⁄
0.01 0.5
⁄
0.6 20. At this point in the design, an analysis procedure would likely be chosen in order to evaluate the design. The choices for analysis procedures include the Equivalent Lateral Force procedure and the Response Spectrum procedure. The Equivalent Lateral Force procedure is most appropriate for an ICEB structure and is easy to replicate. For a one‐story structure, the equivalent lateral force is applied at the top of the wall, and there is no force distribution to be done. Therefore, this manual will not cover the procedure for distributing the lateral force to various structure stories. Additionally, the Response Spectrum procedure will not be outlined. 21. Determine the base shear: Determination of base shear is a simple procedure but is unable to be calculated at this time due to the absence of knowledge of wall performance. Namely, the R value must be known to calculate base shear. Knowing the magnitude of base shear will also allow for a check on the quality of anchoring to the foundation. Page
56 Table 17: Summary Example Design Procedure No.
Item
FEMA – 450- 1/2003
Section
Table
Value
1.
Seismic Use Group
1.2
1.3-1
I II III
2.
Occupancy Importance Factor
1.3
1.3-1
I = 1.0, 1.25, or 1.5
3.
Site Classification
3.5
3.5-1
ABCDEF
4.
MCE Ss and S1
5.
Site Coefficients Fa and Fv
6.
Site Coefficient Adjusted MCE
SRA
SS=
S1=
3.2
3.3
3.3-1
3.3-2
3.3.2
3.3-1
3.3-2
Fa=
Fv=
SMS = FaSS
SM1 = FvS1
SDS= SMS
7.
Design Spectral Acceleration
8.
Seismic Design Category
Page
57 9.
Irregularity: Plan
3.3.3
3.3-3
3.3-4
SS1 = SM1
1.4
1.4-1
ABCDEF
4.3-2
Torsional
Re-entrant
Non-parallel
4.3.2.3
4.3-3
Does not apply to a
one-story ICEB
structure
4.3
4.3-1
Bearing Wall
4.3.2.2
10.
Irregularity: Vertical
11.
Structural System
12.
Coefficient R
4.3.1
4.3-1
R= testing
13.
Overstrength Factor
4.3.1
4.3-1
Ωo= testing
14.
Deflection Amplification
4.3.1
4.3-1
Cd = testing
15.
Structural System / Height
Limitation
4.3.1
4.3-1
Correlation Unknown
16.
Redundancy Factor
4.3.3
17.
Fundamental Period
5.2.2
ρ = 1.0
T=
.
18.
Seismic Dead Weight
5.2.1
W=
19.
Design Base Shear
5.2.1
Cs = testing
20.
Lateral Force Procedure
5.2
21.
Design Base Shear, Vb
5.2.1
Equivalent Lateral
Force
Vb = testing
Failures Modes of ICEB Structures At this time, it is not possible to ascertain the specific types of failures that an ICEB structure may sustain during ground shaking. After investigation of other earthen structures, similar types of failures were assumed for ICEB behavior, and designs to mitigate these failures were made. Each of the potential failures listed below is numbered and corresponds to a location on the structure in the accompanying Figure 49. A brief summary of each design consideration pertaining to the possible failures is also included (Auroville Earth Institute). Diagonal Shear Crack of Piers (1) With the new structural design intent, of relying on the perimeter elements of the structure to resist lateral forces, less stress is intended to be distributed to the locations on the wall between the corners of the structure. The true design intent here is to create somewhat of an increased strength boundary with a reinforced infill wall. This design allows for lateral forces to be absorbed in the wall perimeters and ring beams at various levels that consist of reinforcement running in channel blocks surrounded by concrete. Figure 50, Figure 51, and Figure 52 illustrate diagonal shear cracks. Horizontal Shear Crack of Long Pier (2) ICEB technology allows for dry stacking of blocks, i.e. no mortar is needed at the block‐to‐block interface. This alone limits any horizontal cracking of the walls because the blocks are not expected to fail with horizontal cracks. However, important information may be gained in shear wall testing as the strength of the block dowels is revealed. The actual failure of the dowels shearing off the blocks may prove to be a concern. Page
Bending Crack of Wall (4) Bending of the walls puts a lot of stress on the block interfaces near the corners of the structure. This is a result of a walls tendency to span vertically between the structure corners. It is possible to control the span of the wall so that it spans horizontally, but that would result in the wall not being load bearing. 58 Bending Cracks at Lintels (3) The lintels must have a ductile response and contain rebar developed to a sufficient length beyond the corners of windows and doors in order to reduce the concentration of stress at these locations. It is not necessary to determine the development length of the reinforcement that passes over the windows because the row of blocks at the top of the window is made of channel blocks and will always have reinforcement in it. The advantage of ICEBs is that they are load bearing. Therefore, it is safe to expect forces in these locations and mitigation measures may be developed after shear wall testing exposes the actual behavior. Roof Damage from Vertical Ground Shaking (5) Current ICEB roof designs have highly concentrated loads ‐which would undergo vertical accelerations‐ applied to the ring beam. A new anchoring system has been introduced to the design and consists of a u‐
plate cast into the ring beam, which holds the ends of the roof truss. The lower cord of the roof truss is bolted to the ring beam at regular intervals. A detail may be found for the roof design in the Structural Design chapter under Roof Attachments. Roof Damage from Raking Caused by Torsional Motion of Structure (6) Step 9 of the accompanying example seismic analysis procedure addresses building irregularity in the design process. Torsional irregularity is relevant to roof raking. To decrease likelihood of torsional deflections, the building should be made as close to doubly‐symmetric as possible. This reduces the raking of the roof structure, and similarly decreases the stresses within it and on the connections. Methods of doing this are suggested in the discussion of Simple Form and Symmetry, in the section on design considerations. Figure 49: Potential failures of an ICEB home (Auroville Earth Institute) Page
59 Figure 50: Shear cracks at corner (Auroville Earth Institute) Figure 51 : Large diagonal cracks (Auroville Earth Institute) Figure 52: Failure mechanism of walls (Auroville Earth Institute) Page
60 Water Management Waterproofing systems have the ability to control humidity and interior temperature for comfortable habitation while also improving a structure’s performance. An ICEB looses roughly half of its strength when fully saturated with water (Morel et al., 2007), and therefore needs to be protected much more so than an ordinary masonry building. Sufficient waterproofing is indispensible for maintaining a structure’s longevity. The ICEB walls need to be protected from three different water attacks: wind driven rain on the building’s exterior, capillary rise of water from the foundation, and water seepage from the roof (Garrison et al., 1983). To protect against these threats, multiple different waterproofing methods need to be taken. Walls Option 1: Leave the blocks exposed If the highly sandy soils recommended in the Soil Selection Criteria section (Page 15) are used for block production, the blocks will exhibit sufficient durability in most environments (Venkatarama Reddy and Gupta, 2005). However, exposed blocks may require additional cement to ensure the blocks do not erode. Additionally, a water‐based sealer such as Okon and El Rey adobe sealers can be applied to the exposed walls for additional protection (Hallock, 2010). Exposed blocks will not be effective in moist climates susceptible to frost (Hallock, 2010). If exposed blocks are chosen, extra blocks may need to be produced in order to make them visibly pleasing such that there are no hairline cracks or broken corners. In addition, the wall will have a darker tone, thus creating a warmer interior building. More maintenance may be required compared to a plaster wall if a sealer coat must be periodically applied to the exposed blocks (Hallock, 2010). Option 2: Plaster Plastered walls provide the best performance of all exterior waterproofing systems. The plaster acts as a barrier against water penetration, increases a wall’s strength, and prevents the wall from weakening due to excess water. The plaster is easily repairable and can be costly; however there are hidden costs in not using plaster. Page
61 After construction is complete (the walls and roofs are finished), wait at least a week before applying the plaster. If you choose to plaster the interior walls, do this prior to plastering the exterior walls. The heat on the outside of the wall will help the plaster bind easily to the interior wall. (BuildChange.com, 2009) Applying Plaster to a Wall Suggested Equipment: Plasterer’s rake, a large bucket, a plasterer’s hock, and a float (DoItYourself.com, 2010) 1. Clean the walls of excess grout and dirt and wet the wall to prevent the blocks from sucking water out of the plaster. 2. Mix the plaster by combining Clay: Sand: Cement with water in 3:6:1 proportions until it reaches a thick, spreadable consistency. 3. Start plastering at the top of the wall and work downwards. The minimum thickness should be 1.5 cm. It is important to use a firm pressure while applying plaster to a wall to ensure that it binds to the wall efficiently (BuildChange.com, 2009). 4. Apply a cement slurry to the wall. The cement slurry consists of 4:7 proportions of cement: water (Zhang et al., 2005), mixed to the consistency of thick paste. Cement slurry is meant to fill in any gaps or holes that were missed while plastering. The layer should be thin. Tips: •
•
•
Always have a little more plaster than needed. When an additional batch of plaster is made, it may be difficult to obtain the exact same consistent plaster previously used on a wall. When making a new batch of plaster, all equipment should be cleaned and old plaster discarded (DoItYourself.com, 2010). Terminate the plaster 5 cm above grade to prevent the water in the soil from penetrating the stucco. If the plaster is left with its original color and is not dyed, it provides optimum passive cooling as it reflects more light and heat than white paint (Hallock, 2010). Option 3: Traditional three­coat stucco to the wall Stucco is durable, fire resistant and can withstand extreme weather conditions (associatedcontent.com, 2008). The system consists of a scratch coat, brown coat, and finish coat. Stucco can also be aesthetically pleasing; wet stucco allows for designs to be etched into with a stylus. After the walls and roof are complete, wait at least a week before installing the traditional three‐coat stucco. Stuccoing a Wall Suggested Equipment: Wheel barrow, trowel or shovel, plasterer’s rake, putty knife (DoItYourself.com, 2010) Page
62 Mixing the Stucco 1. Use Table 18 to determine the correct proportions of dry materials, and then combine them. Only one hour’s worth of stucco should be made at one time (essortment.com, 2002). Table 18: Mix Proportions for Stucco Coats Portland Cement Hydrated Lime Sand Scratch Coat 1 1 2.5‐4 Brown Coat 1 1 3.5‐5 Finish Coat 1 1 1.5‐3 2. Add sufficient water while mixing such that the mix has the consistency of a thick paste (essortment.com, 2002). 3. Continue mixing until stucco has uniform color and consistency while protecting it from direct sunlight (essortment.com, 2002). Note: If the mixture begins to harden, you can retemper it only once by adding water to the mixture until it reaches a thick paste consistency (essortment.com, 2002). Applying the stucco (Bhg.com, 2010) 1. Clean the walls of excess grout and dirt. 2. Apply a concrete bonding agent or cement slurry onto the wall using a trowel. A concrete bonding agent helps the scratch coat bind to the wall more effectively (cement.org, 2010). Allow a full day for the bonding agent to completely dry. 3. Apply the scratch coat uniformly to the wall. Refer to Figure 53. The thickness of this coat should be between 5 and 12 mm. Allow this coat to harden for Figure 53: Apply the scratch coat a few hours. 4. Use a plasterer’s rake to scratch the coat horizontally. Refer to Figure 54. The newly formed ridges should be as half as thick as the original thickness of the stucco. This allows the second coat to bond to the first coat more easily. 5. Let the stucco to harden for at least one full day. During this period, spray the wall with water every few hours. This allows the stucco to cure properly. 7. Allow the coat to harden for two full days. Continue to spray the wall every few hours during this hardening period. Page
63 6. Before applying the brown coat, thoroughly Figure 54: Scratch the coat horizontally using a moisten the scratch coat. Apply the brown coat at a plasterer's rake. uniform thickness of 5 to 10mm. 8. Use a trowel to apply the finish coat uniformly, and a putty knife to smooth the edges. The thickness of the finish coat should be 5 to 10mm. 9. Allow the wall to cure for two days while wetting every few hours. 10. Caulk around the doors and windows. Caulking is usually made of silicone, polyurethane, or acrylic (Thomas, 2010). Filling the cracks and holes will prevent water from leaking into the building or weakening the wall (Thomas, 2010). Tips: •
•
Terminate the stucco 10 cm above grade to prevent the water in the soil from penetrating the stucco. Do not apply exterior paints to the finish coat because this may increase moisture impermeability, resulting in the formation of cracks and the separation of the stucco and the wall (Austinenergy.com, 2010). Option 4: Acrylic Paint Acrylic paint is water‐resistant and a very fast drying paint. Either 100% acrylic or alkyd‐modified latex serves as good exterior paints (Vandervort, 2010). However, acrylic paint will peel off the blocks in a short period of time. It would be better leave the blocks exposed. Make sure that there are no gaps or holes in the walls before applying the paint. Apply the paint from the top down, working on one wall at a time. Roof Water Considerations The roof is an absolutely essential waterproofing feature of any structure. Roofing nails or staples will be used to attach the corrugated metal to the roof truss. Brush the area where the nails are positioned with tar so that the water doesn’t penetrate through the small holes. The following must be used to protect the roof and the wall‐roof connection from moisture intrusion. Wide overhangs Wide overhangs provide better protection for the walls, doors, and windows as well as keep runoff water further away from the foundation. Overhangs provide shade during the summer. It is recommended to use overhangs at least 60 cm in length, as seen in Figure 55. Figure 55: 60 cm overhang Page
64 Rain Gutters and Downspouts Rain gutters direct the runoff from the roof towards proper drainage and away from the building. They protect windows, doors, and the foundation from excess moisture. Without the use of this system, water damages may occur and erode the soil around the foundation. Different types of gutters that can be used for the roof: Vinyl gutters are lightweight and can be easily cut. They are dent and rust resistant. However, these gutters can deform in very hot climates (Tate, 2010).See Figure 56. Galvanized steel gutters are the most durable type. They work well in monsoon rains. They are usually more expensive than vinyl gutters (Tate, 2010). Aluminum gutters are the most popular gutters. They are rust resistant, but can be easily dented. In regions with heavy rains, it is recommended to use 15.5 cm gutters to Figure 56: Gutter Types (Tate, 2010) prevent water overflow (Tate, 2010). How to install the gutters: Use straps, brackets, and/or hangars to attach gutters to the house’s eaves. For rain gutters to drain properly, ensure that they slope 1 cm for every 3 m toward a downspout (Hazelton, 2009). Gutters will be attached to the end of the roof truss. It is best to have one downspout per gutter positioned such that the downspout is located on the lower end of the gutter. Drive screws through each bracket and into the eaves to attach the gutters. Apply tar over the area, where the screws are exposed on the roof with tar to prevent leakage. Before cutting the downspout and fitting the pieces together, make sure the downspout stops 1 m above grade. The tapered end of the downspout will be directed towards a sump basket which collects the rainwater. Page
65 Water Purification A ceramic water filter can be used after collecting the rainwater with a sump basket, similar to that in Figure 58. Ceramic filters remove pathogens and other contaminants from water. Under laboratory conditions, the filters removed 99.9% of fecal coliform. The lifetime of these ceramic water filters is 2 years (PottersforPeace.org, 2006). The bucket is fired to around 860 degrees Celsius, and then the filter is coated with colloidal silver. The colloidal silver is an Figure 58: Ceramic water filter effective filter due to its fine pore size and its (PottersforPeace.org, 2006) bactericidal properties. The proportions of clay and sawdust and the firing temperature determine the 1.5 to 2.5 liter per hour rate of filtration. Local production costs determine the price of the Figure 57: Inside of ceramic water filter ready to use filters with the receptacle. Prices range between $15‐25. (PottersforPeace,2006) Prices for replacement filter elements are $4 to $6. Fifty filters a day can easily be made with three or four workers (PottersforPeace.org, 2006). Foundation Groundwater tables, rain, condensation, and leakage from the upper portion of the walls are all means by which water has the potential to infiltrate footings. A good drainage and barrier system is the only way to stop water intrusion into the footing and subsequent capillary rise into the ICEB walls. Installing a drainage and moisture barrier system in addition to a properly sloped ground will produce greater results of preventing leakage and moisture intrusion. Thus, it is recommended to use all four of the following methods. 1. Waterproof the footings The footings must be waterproofed such that seepage or dampness through the walls does not occur. The following methods can be used to waterproof the footings. Option 1.A: PVC waterproofing and mortar The combination of using PVC waterproofing and mortar may be the most effective since the mortar binds the channel blocks to the surface, and PVC prevents water from seeping into the walls (Wheeler, 2005). Some characteristics of PVC are its high tensile strength and elongation. It allows the substrate to move with changes in the temperature without cracks (Bikudo.com, 2010). 1.
2.
3.
4.
Apply a 3‐4 cm layer of mortar. Add cement powder and trowel it into the mortar. Place plastic film (PVC waterproofing membrane) onto the mortar. Apply another layer of mortar on top of the PVC. Option 1.B: Mortar Mortar binds the surface of the footing to the block. It is cost‐effective. 1. Apply a 3‐4 cm layer of mortar onto the footing (Wheeler, 2005). Refer Figure 21. 2. Add cement powder on top of the layer and use a trowel to bind the cement into the mortar. Then lay the first block on top of this layer (Wheeler, 2005). Page
During excavations, place a drainage system at the bottom of the trenches. Dig the trench until reaching good soil. Compact the bottom of the trench and the backfills near the house (Houben and Guillard, 1994). See Figure 59. The system should be within 1.5 m of the foundation. The first layer, consisting of burnt clay, should be placed at the bottom of the trench. The clay is intended to collect water and direct 66 2. Drainage An adequate drainage system is important in order to keep water away from the house. Observe if water is stagnant within 3 m of the proposed foundation an hour after rain has occurred (foundationrepairs.com, 2009). If water is observed to be stagnant, a drainage system should be installed. However, drainage systems alone are not guaranteed to prevent water intrusion. it away from the building by diffusion. The second layer should be filled with stones and gravel. This layer acts as a filter system. 3. Moisture barrier Even with an excellent drainage system, water can still flow under the surface and reach the floor level. Moisture barriers are designed to keep water from seeping into the floors and walls. Use a screen (plastic sheet) and apply it to the outer surface of the foundation. See Figure 59. This system prevents capillary movement between the base course and the foundation. Ensure that this barrier system is perfectly continuous. Other damp‐proof courses are water‐repellent cement (500kg/m3) and bituminous products (Houben and Guillard, 1994). See Figure 59. 4. Surface drainage Slope the ground away from the building to encourage drainage. The finished grade should slope away from the foundation at a rate of 5 to 10 cm per 1 m for 3 m. (Palmer, 2007) Apply a layer of silty clay with a thickness of 5 to 10 cm on top of the finished grade. (Anderson, 2010) This will keep runoff from permeating down through the backfill. Substitutes for silty clay are silt loam, sandy clay loam, and clay loam (deh.enr.state.nc.us, 2004). Figure 59: Waterproofing the footings, surface drainage, drainage below grade, and moisture barriers are shown Page
67 Vegetation should be planted around the building in order to slowly direct the water down the slope. However, vegetation should not be placed closer than a meter or two from the building, as plants near the foundation may cause excess water to accumulate and push the soil upwards. For unstable soils In extremely arid climates, soil can be unstable. Alluvium soils are also unstable since they can be expansive. There must be additional actions in order to protect the foundation from settlement, moisture intrusion, and capillary movement towards the surface. It is necessary to provide a good drainage system for all types of soil (Houben and Guillard, 1994). In addition to the methods listed above, expansive soils can be stabilized by treating it with lime Quicklime or hydrated lime may also be used. Lime is inexpensive and is most effective on clayey soils. Precautions should be taken to not inhale the lime dust (austinenergy.com, 2010). Protection from Insect Infestation Insects typically favor humid areas, and the infestations can be a nuisance or even cause damages to the building (Houben and Guillard, 1994). •
•
•
•
•
Provide a good drainage system. Ensure the structure’s borders are clean all the time. Fill in the cracks of the masonry by caulking it. Avoid wooden floors. Treat the soil by using anti‐termite insecticides or diatomaceous earth. Diatomaceous earth is made up of tiny fossilized phytoplankton. It is a natural occurring soft sedimentary mineral that is grinded up into a fine, white powder. It is used as a pesticide (ghorganics.com, 2010). Types of Floors Floors must prevent perforations and moisture from seeping in as well as stand up to loadings (Houben and Guillard, 1994). Solid floors help keep the interior of the house cool during summer. These types of floors must be applied on top of the load‐bearing layer and should be structurally independent from the walls. Page
1. Apply a thin layer of cement grout mixed with fine sand and sawdust. The layer consists of 1:1:1 proportions of Sand: Cement: Sawdust. To increase the stability and load‐bearing capacity of the layer, soak the sawdust in lime or cement slurry (Houben and Guillard, 1994). 2. Allow the sawdust to dry before adding it into the final mixture. After the finish layer is completely dried, the floor may be waxed or polished (Houben and Guillard, 1994). 68 Option 1: Thin layer of cement grout Cement grout is cost effective and can increase the floor’s strength. The following steps must be performed for the finish layer. Option 2: Stabilized Adobe Mortar with Bitumen The stabilized adobe mortar with bitumen will act as a monolithic floor. Monolithic floors have no joints or seams and are designed to prevent leaks (alphasourceintl.com, 2009). The following steps must be performed for the finish layer (Houben and Guillard, 1994). 1. Prepare the soil properly according to the four guidelines (Water Proof, Drainage, Moisture Barrier, Surface Drainage) mentioned previously. 5. Properly position the formwork for the floor. 6. Pour the adobe mortar uniformly and in one pour. Use a screed to spread it evenly 7. Allow the layer to dry. Cracks due to shrinkage will occur. Use a finer adobe mortar to fill in the gaps. Trowel the mortar evenly and then allow it to dry. 8. After it is dry, apply a mixture of turpentine and linseed oil to treat the floor’s surface. 9. Allow the floor to dry for a week. After the floor is completely dry, the floor may be polished or waxed. Option 3: Stabilized Concrete Mortar Another option is stabilized concrete mortar. This may be more expensive to use than adobe mortar. The formula consists of 1:6‐8 proportions of Cement: Sandy soil (Houben and Guillard, 1994). 1. Prepare the soil properly according to the four guidelines (Water Proof, Drainage, Moisture Barrier, Surface Drainage) mentioned previously. 2. Properly position the formwork for the floor. 3. Apply a 5 cm layer of stabilized concrete mortar to the load‐bearing capacity layer. Ensure the construction joints are provided every 1.5m. The joints should be 3cm deep and 0.5cm wide (Houben and Guillard, 1994). Option 4: More Alternatives Other alternatives for floors are rammed earth or rammed stabilized clay‐straw (Houben and Guillard, 1994). Rammed earth must be stabilized with rather Portland Cement or asphalt emulsions (Schooled, 2001). Asphalt emulsion is asphalt dispersed in water and then stabilized in a chemical system (emultech.com, 2000). Note: If a floor design is not used, it is still recommended to follow the guidelines in Preparations to Install the Floor below to ensure there is no seepage or capillary movement towards the surface. Preparations to Install the Floor Preparations to install the floor must be made in order to prevent capillary action and leakage. The following steps must be performed to ensure no water intrusion and are illustrated in Page
69 Figure 60 (Houben and Guillard, 1994). Page
70 1. Prepare the soil. Remove all organic matter from the soil (BuildChange.com, 2009). Ram the top layer of the soil unless the load‐bearing capacity is adequate or the soil is subject to expand. Before floor construction begins, make sure the soil is dry. 2. Waterproof the soil. Lay a 10 cm layer of moist clay (other options are bitumen, lime‐stabilized sandy soil, stabilized earth plaster, or a plastic sheet) in carefully rammed layers. The layer of clay prevents capillary action by acting as a damp‐proof membrane. Wait for each layer to dry and make sure the cracks are filled before adding another layer. The last layer should be rammed and finished with a flattening hammer. Any option used must rise up along the base of the wall to keep water out. 3. Use stones to act as a filter system. The layer of stones should be 20 to 25 cm. Place the largest stones prior to the gravel. Dry stone can be substituted for gravel and coarse sand. 4. Apply an insulating layer. An insulating layer should cover the layer of stones and gravel. The insulating layer can be straw‐clay with a thickness of 10 cm. If the layer is too flexible, use a bearing course to distribute the load. 5. Apply a load‐bearing layer. Apply a 4cm thick layer of clay and cut straw to the insulating layer. Add 4cm to 6 cm long straw stalks and cement mortar to the mixture. The clay‐straw mixed with cement should have a formula of one volume of cement for every six volumes of washed sand. Allow the layer to cure and harden. Moistening the layer helps the curing process and strengthens the layer. Figure 60: Preparations to install the floor. Page
71 Openings Openings provide ventilation, sunlight, and add accessibility to a structure. However, if they are not constructed correctly, water can use these openings to easily infiltrate the structure leading to premature degradation of the structure. Therefore, it is important doors and windows are adequately waterproofed. It is recommended to complete the placement of the blocks and then determine the correct dimensions of the windows and the door. This will prevent gaps and water intrusion from occurring. Use the correct dimensions to order the opening frames (Enderson, 2010). Windows Use galvanized steel flashing above the window. Make sure the galvanized steel flashing extends to the top and onto the channel blocks just above the opening. The metal flashing will be in between the two channel blocks and secured by nails and mortar. Ensure the steel flashing is sloped downwards and is extended away from the building 15 cm. See Figure 61. Place a fired brick sill below the opening to prevent moisture from entering into the windows. Slope the fired brick sill downwards and away from the building. Use silicone, acrylic, polyurethane, or cement sealant on the joint where the window meets the exterior siding of the building (Wheeler, 2005). Page
72 Ways to fasten a window frame to the blocks: 1. Drill holes in the blocks. 2. Put plastic or wood inserts in the holes. 3. Drive screws through the frame and into the insert. Tips: •
•
•
Brush the area, where the screws are positioned in the block, with mortar to prevent water intrusion in the walls. Avoid perforations in the bottom of the window frame as they can cause leakages. The thicker the window panes are (280mm glass thickness is recommended), the more heat loss is reduced and noise insulation is improved as well (megahowto.com, 2010). Doors Figure 61: Window installation system Doors are susceptible to water intrusion if the waterproofing (Wheeler, 2005) system is not properly installed. Install galvanized sheet metal flashing above the door opening using the same method for the windows. Flashing is required to keep water away from the bottom of the door. Apply a self‐adhesive waterproofing flashing to cover the area under the door. See Figure 62. Ensure the corners where the walls meet the floor are sealed as well (Carter, 2010). See Figure 63. Figure 62: Apply flashing to the load bearing layer at the foot of the door. (Carter, 2010) Page
73 Figure 63: Flashing must be applied to the corners as well. (Carter, 2010) Page
74 Appendix A Table A.1: Example Washing Test Results Mass, dried (grams) Relative Proportion Relative Percentage Gravel 42 42/682 6.2% Sand 490 490/682 71.8% Fines 150* 150/682 22.0% Soil, initial 682 682/682 100.0% *inferred Sample calculation for determining remediation proportions Soil A: 3% gravel, 56% sand, 41% fines Soil B: 2% gravel, 92% sand, 6% fines Target soil: 65% sand 56%
92%
65% 100% 1
56%
36%
.25 ,
92%
65% 9% .75 A 3B Combine Soil A and Soil B in 3:1 proportions Page
75 Sample calculation for determining charge size Moisture content 12% Volume of block 3825 cm3 Target dry density 1800 kg/m3 1800 /
1800 /
6.89 1800 /
. 003825 .12 1.12
7.7 /
Page
76 . 12
Appendix B Page
77 Sample calculation for the approximate fundamental period of and ICEB shear wall 2.4 m X 2.5 m Gaps The following is a list of unresolved questions that came up during this project. These are among the first things that need to be addressed in the future. Structural & Seismic Soils & Block Production Water Management Gaps Consider expansion joints to help prevent cracks. Should a vapor barrier be used for Traditional 3 coat stucco? Priority Moderate Moderate Look more into ceramic water filters. Potters for Peace organization helps people make them. Look for more options to purify water. Investigate waterproofing membranes and their connections to the wall. Identifying chemical presences in the soil. Moderate Moderate High High Difficulty Moderate Low‐
Moderate Moderate Moderate Moderate Moderate Correlating field block test to compressive strength. High High Investigating soil additives and alternating binding agents. Low Moderate Investigate the feasibility of making the blocks solid with dowel holes only for vertical reinforcement. High Low Describe a method for assessing potential settlement of a project site Moderate Moderate Identify whether grout and concrete channels inhibit dowel shear resistance. High Moderate Determine Response modification factor (R). Determine Overstrength Factor (Ω0). Deflection Amplification Factor (Cd). High High High High High High Consider splicing longer timber truss members and the timber joinery that would be used to increase strength. Moderate Investigate the performance of cyclopean footings in earthquakes as an economical alternative to reinforced concrete. Low Verify the capacity of the vertical reinforcement spacing based on shear wall testing. High For larger truss designs than laid out in this manual, investigate the use and necessity of larger timber beams. High Moderate Moderate High Moderate Page
78 Works Cited Page
79 Adam, E. A., and Agib, A. R. A. (2001) Compressed Stabilised Earth Block Manufacture in Sudan. Paris: United Nations Educational, Scientific and Cultural Organization. “Advantages of a Stucco Exterior on Your Home.” 23 June 2008. Associated Content. 4 April 2010. http://www.associatedcontent.com/article/825895/advantages_of_a_stucco_exterior_on.html>. Anderson, B. “Foundation Drainage.” (2010) ServiceMagic, Inc. 21 Feb. 2010. <http://www.servicemagic.com/article.show.FoundationDrainage.13702.html#ixzz0mAapWHze>. “Applying Stucco.” (2010) Meredith Corporation. 4 April 2010. <http://www.bhg.com/home‐
improvement/exteriors/siding/applying‐stucco/?Page=2>. “Asphalt Emulsions: Emulsion Basics.” (2000) Valley Slurry Seal Co. 15 April 2010. <http://www.emultech.com/index.htm?Page=/asphaltemulsions_basics.htm >. Bales, C., Donahue, C., Fischer, M., Mellbom, A., and Pearson, T. (2009) INTERLOCKING COMPRESSED EARTH BLOCKS From Soils to Structures. San Luis Obispo: California Polytechnic State University. Boubekeur, S., and Houben, H. comps. (1998) Compressed Earth Blocks Standards. Brussels: Center for Development of Industry. Bryan, A. J. (1988) “Criteria for the Suitability of Soil for Cement Stabilization." Building and Environment 23.4: 309‐319. Burroughs, Steve. (2006) "Strength of Compacted Earth: Linking Soil Properties to Stabilizers." Building Research and Information 34.1: 55‐65. Carter, T. “Exterior Door Installation Video.” (2010) Tim Carter. 15 April 2010. <http://www.askthebuilder.com/Exterior_Door_Installation_Video.shtml>. “Earth Construction.” Sustainable Building Sourcebook. (2010) Austin Energy Green Building. 10 Jan. 2010. http://www.austinenergy.com/Energy%20Efficiency/Programs/Green%20Building/Sourcebook/earthCo
nstruction.htm. “How to Layout and Perform Footing Excavation Without Heavy Equipment” eHow, Inc. demand Media, 2010. Web. 1 May, 2010. http://www.ehow.com/how_4809087_perform‐footing‐excavation‐heavy‐
equipment.html Page
Enderson, L. “How to Construct a Window Frame.” (2010) eHow, Inc. 15 April 2010. http://www.ehow.com/how_4829746_construct‐window‐frame.html. Building Seismic Safety Council. (2003) NEHRP Recommended Provisions for Seismic Regulations for New Buildings and Other Structures. FEMA 450‐1/2003 “Filters.” (2006) Potters For Peace. 28 April 2010. http://pottersforpeace.org/?Page_id=9. Fitzmaurice, R. (1958) Manual on Stabilised Soil Construction for Housing. Technical Assistance Programme, United Nations, New York. “Floor Systems and Coatings.” (2010) AlphaSource. 15 April 2010. http://alphasourceintl.com/pl/floor_ctgs.htm#Monolithic Flooring Systems. “Foundation Drainage.” (2009) Advanced Foundation Repairs. 15 April 2010. http://www.foundationrepairs.com/foundationmaintenance/drainage.php. Garrison, J.W. and Ruffner, Elizabeth F. (1983) “Common Sources of Deterioration.” Adobe: Practical & Technical Aspects of Adobe Conservation. Tuscon, AZ: Library of Congress Cataloging. 16‐18. Geiger Research Institute of Sustainable Building.(2004). New Mexico Compressed Earth Block Building Code. Gooding, D. and Thomas, T.(1997) 'Soilcrete blocks', Building Research & Information, 25.4: 202‐209. Guillaud, H., Joffroy, T., and Odul, P. (1995) COMPRESSED EARTH BLOCKS: MANUAL OF DESIGN AND CONSTRUCTION. Vol. 2. CRATerre‐EAG. Hallock, J. and N. “Block Placement.” Earth Block, Inc. 14 April 2010. http://www.earthblockinc.com/placement.htm. Hazelton, R. “How to Install Gutters.” (2009). Ron Hazelton Productions – Do It Yourself Home Improvement. 10 April 2010. http://www.ronhazelton.com/article/outdoors/other/UDIyNg/How_to_Install_Gutters. Hausler, E.A. (2009) Handbook for Building Simple, Earthquake‐Resistant Houses. Build Change. Web. 28 Feb, 2010. http://www.buildchange.org/tech/BC_BOOK‐english.pdf Heathcote, K. (1991) "Compressive Strength of Cement Stabilized Pressed Earth Blocks." Building Research and Information 19.2: 101‐105. Houben, H. and Guillaud, H. (1994) Earth Construction: A Comprehensive Guide. CRATerre‐EAG, ITDG Publ.,London. 80 “How to Construct Windows.” 13 Jan. 2010. Mega How To. 15 April 2010. http://www.megahowto.com/how‐to‐construct‐windows. “How to Build Strong and Sturdy Houses.” 2009. Build Change. 4 March 2010. http://www.buildchange.org/tech/BC_BOOK‐english.pdf. “How to Make Stucco.” 2002. Essortment. 4 April 2010. http://www.essortment.com/all/stuccomixtures_rgfy.htm. Hydraform. “Experimental Earthquake Loading of a Full Scale Dry Stacked Masonry Structure” Hydrafrom Earthquake – Resistant System. Hydraform, 2010. Web. May 12, 2010. http://www.hydraform.com/BuildingSystems/Earthquake.asp Page
81 Kerali, A. G. and Thomas, T. H.(2002) 'Effect of mix retention and curing on low‐cement walling blocks', Building Research & Information, 30: 5, 362‐366 Key, D. (2006) "3.5 Analysis for Capacity Design; 8.1 (Lessons from Earthquake Damage." Earthquake Design Practice for Buildings. By Edmund Booth. 2nd ed. Thomas Telford. Krinitzsky, E.L. (1993). Fundamentals of Earthquake Resitant Construction. John Wiley and Sons, Inc. Maïni, S. (2010) "Disaster Resistance: Earthquakes and Structures." MS. Auroville Earth Institute, Auroshilpam, Auroville. Auroville Earth Institute. Web. 13 May 2010. <http://www.earth‐
auroville.com/?nav=menu&pg=disaster&id1=12&lang_code=en>. Merrill, A.F. (1947) The Rammed‐Earth House. New York: Harper & Brothers Publishers Middleton, G.F. (1953) Build Your House of Earth. Sydney: Australia: Halstead Press PTY LTD, 1953. Minke, G. (2006) Building With Earth. Berlin: Publishers for Architecture, 2006. Print Morel, J. C., Mesbah, A., Oggero, M., and Walker, P. (2001) "Building Houses with Local Materials: Means to Drastically Reduce the Environmental Impact of Construction." Building and Environment 36: 119‐126. Morel, J.C., Pkla, A., and Walker, P. (2007) "Compressive strength testing of compressed earth blocks." Construction and Building Materials 21: 303‐309. MSJC. (2005). ACI 530 Code, Specifications, and Commentary. Page
Palmer, W.D. “10 Tips for Foundation Drainage.” (2007) Residential Concrete Magazine. 1 July 2007. Concrete Construction. 15 April 2010. http://concreteconstruction.net/industry‐
news.asp?sectionID=716&articleID=540600. “PVC waterproof membrane.” (2010) Bikudo.com. 21 Feb. 2010. http://www.bikudo.com/product_search/details/45596/pvc_waterproof_membrane.html#desc. Rigassi, V. (1995) Compressed Earth Blocks: Manual of Production, Vol. 1, CRATerre‐EAG, Vilefontaine. Sabnis, G.M. and Harris, O. H.G. (2010) “Case 10.3.4 Interlocking Mortarless Block Masonry” Structural modeling and experimental techniques. CRC Press LLC, 1999. Google books. Web. 20 Feb. Santhakumar, A.R. (2010) "Design of Reinforced Masonry." Lecture. Slide Share: Present Yourself. IIT Madras. Web. 13 May 2010. http://www.slideshare.net/tejaandeiitm/design‐of‐reinforced‐masonry Schildkamp, M. (2009) Suitability of Local Soil for Cost Saving Construction Techniques V.2. Smart Shelter Foundation. Schooley, C. “Rammed Earth.” (2010) Green Home Building. 15 April 2010. http://www.greenhomebuilding.com/rammedearth.htm. “Soil Characteristics (Morphology).” (2010) 8 June 2004. North Carolina Department of Environmental and Natural Resources. 15 April 2010. http://www.deh.enr.state.nc.us/osww_new/new1/images/Rules/1941.pdf. Spence, R. J. S. (1975) "Predicting the Performance of Soil‐cement as a Building Material in Tropical Countries." Building Science 10: 155‐159. Step‐By‐Step Masonry and Concrete. Preparing Sites for Wall Footings. Better Homes and Gardens, 2010. Web. 1 May, 2010. http://www.bhg.com/home‐improvement/exteriors/concrete/preparing‐sites‐
for‐wall‐footings/?Page=2 “Stucco.” (2010) Portland Cement Association. 15 April 2010. http://www.cement.org/stucco/faq_bonding.asp. Tate, M. (2010) “Types of Gutters‐Aluminum, Vinyl, Steel and Copper.” 2010. EzineArticles.com. http://ezinearticles.com/?Types‐of‐Gutters‐‐‐Aluminum,‐Vinyl,‐Steel‐and‐Copper&id=3523550. Thomas, R. (2010) “How Does Caulking Work?” 2010. eHow, Inc. http://www.ehow.com/how‐
does_4587850_caulking‐work.html. Vandervort, D. (2010) “Buying and Installing Gutters.” Home Tips, LLC. 10 April 2010. http://www.hometips.com/buying‐guides/rain‐gutters.html. 82 Page
83 Vandervort, D. (2010) “House Paint Options.” Home Tips, LLC. 10 April 2010. http://www.hometips.com/buying‐guides/house‐paint‐options.html. Venkatarama Reddy, B. V., and Gupta, A. (2005) "Characteristics of Soil‐cement Blocks Using Highly Sandy Soils." Materials and Structures 38: 651‐658. Venkatarama Reddy, B. V., Lal, R., and Nanjunda Rao, K. S. (2007) "Optimum Soil Grading for Soil‐
Cement Blocks." Journal of Materials in Civil Engineering 19.2: 139‐148. Walker, P. (1995) "Strength, Durability and Shrinkage Characteristics of Cement Stabilised Soil Blocks." Cement & Concrete Composites 17: 301‐10. “Wall Finishes: Plastering.” (2010) Do It Yourself. 21 Feb. 2010. http://www.doityourself.com/stry/plastering. Wheeler, G. (2005) Interlocking Compressed Earth Blocks Manual of Construction. Vol. 2. Center for Vocational Building Technology. Zhang, B.X., Wang, K.H., Cleveland, T.G. “Development and Characterization of Soil‐Cement Slurry.” 14 April 2005. University of Houston, Department of Civil and Environmental Engineering. 22 Feb. 2010. http://cigmat.cive.uh.edu/content/cigmina98/poster14.html.