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Technical guide
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The Technical Department for Transport, Roads and Bridges Engineering and Road Safety (Service d'études
techniques des routes et autoroutes - Sétra) is a technical department within the Ministry of Transport and
Infrastructure. Its field of activities is the road, the transportation and the engineering structures.
The Sétra supports the public owner
The Sétra supplies State agencies and local communities (counties, large cities and urban communities) with
informations, methodologies and tools suited to the specificities of the networks in order to:
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improve the projects quality;
help with the asset management;
define, apply and evaluate the public policies;
guarantee the coherence of the road network and state of the art;
put forward the public interests, in particular within the framework of European standardization;
bring an expertise on complex projects.
The Sétra, producer of the state of the art
Within a very large scale, beyond the road and engineering structures, in the field of transport, intermodality,
sustainable development, the Sétra:
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takes into account the needs of project owners and prime contractors, managers and operators;
fosters the exchanges of experience;
evaluates technical progress and the scientific results;
develops knowledge and good practices through technical guides, softwares;
contributes to the training and information of the technical community.
The Sétra, a work in partnership
• The Sétra associates all the players of the French road community to its action: operational services; research
organizations; Scientific and Technical Network (Réseau Scientifique et Technique de l'Equipement – RST), in
particular the Public Works Regional Engineering Offices (Centres d'études techniques de l'Equipement –
CETE), companies and professional organizations; Expressway concessionary operators; other organizations
such as French Rail Network Company (Réseau Ferré de France – RFF) and French Waterways Network (Voies
Navigables de France - VNF); Departments like the department for Ecology and Sustainable Development…
• The Sétra regularly exchanges its experience and projects with its foreign counterparts, through bilateral cooperations, presentations in conferences and congresses, by welcoming delegations, through missions and
expertises in other countries. It takes part in the European standardization commissions and many authorities
and international working groups. The Sétra is an organization for technical approval, as an EOTA member
(European Organisation for Technical Approvals).
Technical guide
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Published by Sétra and carried out by the French Road Engineering Committee (CFTR)
This document is the translation of the work "Thermorecyclage", published in May 2004 under
the reference 0410.
The CFTR is a federative structure which joins together various components of the
French road community in order to work out an expression of the state of the art
shared by all and used as reference to the road professionals in the fields of
pavements, earthworks and road drainage.
Main actions of the CFTR:
• laying down documents expressing the state of the art;
• drawing up technical advices on fitness for the use of processes, products and equipments, as
well as qualification documents for equipments;
• issuing approvals for road laboratories;
• carrying out procedures of certification and conformity with standards.
French Road Engineering Committee
Association ruled under the law of 1 st july 1901.
Its Head office is located at:
10 rue Washington 75008 Paris
Phone: 33 (0)1 44 13 32 84 – Fax: 33 (0)1 42 25 89 99
mél : [email protected]
internet : http://www.cftr.asso.fr
Hot remixing - Technical Guide
As part of the activities of the "Methodology" Sectoral Committee of the French Road Technique
Commission (Comité français pour les techniques routières CFTR), this technical guide has been written by
a working group including representatives of the scientific and technical network of the Ministry of
Transport, Infrastructure, Regional Development, Tourism and the Sea, contractor technical divisions and
producers in the roads sector.
Its contents have been validated by the various members of the CFTR.
Editorial team:
• Michel Dauzats (L.R.P.C., Aix-en-Provence)
• Jean François Lafon (L.R.P.C., Toulouse)
• Pierre Pringuet (COLAS Midi Méditerranée)
"Tools" collection - Sétra
– 4 –
juin 2007
Contents
Contents............................................................................................................................................... 5
Why in situ hot remixing?.................................................................................................................. 7
Equipment........................................................................................................................................... 8
Pre-heaters ....................................................................................................................................... 8
Scarification/mixing and laying machines ..................................................................................... 10
First type ................................................................................................................................. 10
(Figure 3) comprises, apart from new heating panels ............................................................ 10
Second type.............................................................................................................................. 11
(Figure 4) differs from the first through its type of cohesion breaker and its mixing method. 11
Third type ................................................................................................................................ 13
(Figure 5) is identical to the second for the cohesion breaking and mixing, with in addition 13
Laying ............................................................................................................................................ 13
Preliminary studies........................................................................................................................... 14
Characterization of materials in situ .............................................................................................. 14
Processing study............................................................................................................................. 15
Formulation testing ........................................................................................................................ 15
Inspections......................................................................................................................................... 17
Scope.................................................................................................................................................. 18
Performances and behavior............................................................................................................. 20
Sensitive points ................................................................................................................................. 22
Future of the technique .................................................................................................................... 23
Appendix 1 ........................................................................................................................................ 25
Rejuvenating agents ......................................................................................................................... 25
Appendix 2 ........................................................................................................................................ 27
Sample formulation studies ............................................................................................................. 27
Study consistency........................................................................................................................... 27
Actual study scenarios, examples .................................................................................................. 27
Preliminary survey .................................................................................................................. 28
Objectives of the special technical specifications ................................................................... 29
Correcting agents.................................................................................................................... 29
Hot remixing study .................................................................................................................. 29
Formulation study ................................................................................................................... 34
Comments................................................................................................................................ 35
Site........................................................................................................................................... 36
Studies ..................................................................................................................................... 37
A few test results...................................................................................................................... 38
– 5 –
juin 2007
Technological advances since the end of the 1970s in in situ roadmixing of asphalt have used a distressed
layer to the greatest advantage after heating by making it re-usable without removing or adding material or
by additions, with total or partial removal of material, to achieve the desired material once laid.
These techniques, known as hot remixing, hot reforming or repaving, are grouped under the single term of hot
remixing or in situ hot recycling. This includes all bituminous asphalt recycling on the site by heating, pavement
scarification, mixing with or without additions (aggregates with or without pre-coating, binders, additives, etc.)
and re-laying the mix.
– 6 –
juin 2007
Why in situ hot remixing?
Road network managers face a variety of problems posed by maintenance and repair of surface courses:
• surface cracking of bituminous concretes due to ageing of the bitumen;
• creep of surface courses due to:
- the use of crushed or rolled sand,
- bitumen overdoses or poor choice of binder class,
- inappropriate formulation for the traffic or climate;
• cracking from fatigue triggered by the surface course slipping from its substrate. This phenomenon could
be superimposed on the surface cracking through ageing.
The manager frequently has no other conventional alternative to solving these problems than:
• laying a new asphalt course sufficiently thick (more than 4 cm) to restrict cracking re-occurring rapidly in
the surface, particularly when surface cracking is involved and the substrate is very distressed.
• laying a very thick course of more than 7 cm when there is fatigue in the surface course following
slipping, to avoid ruining the slipped asphalt and its base layer;
• milling the surface course rutted by creep and replacing it by new asphalt without its predecessor's
defects, all the more so as the build-up of rutted asphalt through creep is exceptional as it is only possible
to guarantee elimination of the phenomenon by laying major thicknesses.
In all circumstances, any build-up of more than 4 cm implies not inconsiderable ancillary work being added
to the cost of the operation: raising shoulders and rails, processing of hard shoulders, median breaks,
shallow surface water and drainage channels, etc.
Where there is sufficient structure, slotting an in situ hot remixing into a maintenance and repair scenario
can be both economical and advantageous, for the lifetime of an asphalt can be prolonged by five to eight
years using this type of technique.
Apart from limiting ancillary work, this technique is used for:
• selective processing of lanes or distressed zones;
• maintenance of underpass clearances;
• removal of tapered lanes in line with underpasses;
• savings in aggregates and transport of materials:
• re-use of all or part of noble and high-performing materials;
• creation of hot longitudinal joints without problem;
• continuity between shoulder and pavement;
• correction of:
- unevenness, particularly small wavelength defects,
- macro-roughness by adding aggregates with strong intrinsic characteristics,
- formulation inappropriate for the traffic or the compactness by modifying the aggregate composition or
the dosage in bitumen;
• eliminating the potential rutting by adding additives.
– 7 –
juin 2007
Equipment
In situ remixing involves processing the bituminous asphalts by heating, breaking the cohesion, mixing
with the necessary correcting agents and re-laying the mix. Specific equipment is used for these various
operations:
• raising and maintaining the temperature of the pavement prior to breaking its cohesion using a set of preheaters fitted with large areas of radiating panels.
• breaking the cohesion and depending on the equipment, windrowing in the axis of the asphalt machine;
• mixing the old asphalt with the necessary correcting agents using a double-shaft horizontal mixer or a
screed with an alternative transverse movement;
• spreading the mix obtained out to the desired profile using a heavy paver screed;
• compacting using conventional equipment suitable for the processed thickness.
The standard equipment (Fig. 1) comprises a set of pre-heaters, a scarification machine for mixing and
spreading the remixed material and equipment for compacting and finishing the remixed asphalt.
The following are equipment used on the French market:
- SOAVE RECYCLING process, developed and used in Italy,
- the THERMOCOL process,
- WIRTGEN equipment.
Pre-heaters
All machines are designed under the same principle. Each pre-heater is equipped with 40 to 60 m² of
infrared radiating panels supplied by liquefied gas. On modern pre-heaters, panels are mounted on
telescopic beams used to move and retract the various components automatically (Fig. 2).
Depending on the depth being processed, the climatic conditions and performances sought, the minimum
heating area is 175 to 200 m2; this can reach 250 or even 300 m2 for greater thicknesses and if
meteorological conditions are less than ideal (wind and wet asphalt).
The in situ asphalts are heated to an average temperature of 120 to 140°C over a thickness of up to 7 cm for
a single-layer asphalt and a width of 2.5 to 4 m.
This operation must ensure a slow, gradual rise in the temperature of the asphalt being processed to avoid
any major thermal shock and binder deterioration. Each pre-heater moves forward at between 2 and 6 m/mn
and must be adjusted to the prevailing conditions to maintain a temperature > than 80°C at the interface
with the substrate, in the knowledge that it can reach 250°C at the surface of the asphalt (Photo 1).
The following are normally adopted:
- 4 to 6 m/mn for roadmixing on 3 to 4 cm,
- 2 to 3 m/mn for thicknesses of 6 to 7 cm.
– 8 –
juin 2007
Figure 1: standard hot remixing equipment
Figure 2: Pre-heater
Préchauffage
Sens d'avancement
Préchauffeuse en position de travail
Préchauffeuse en position de transfert
DMF régénération
Compactage
Pre-heating
Direction of progress
Pre-heater in working position
Pre-heater in transfer position
Rejuvenating DMF
Compacting
– 9 –
juin 2007
Scarification/mixing and laying machines
There are three main types of machine.
First type
(Figure 3) comprises, apart from new heating panels
• a silo used to spread pre-coating chippings over the carpet being processed. They can be introduced from
the silo immediately after surface pre-heating of the old surfacing before cohesion-breaking milling to
ensure aggregate pre-heating and a homogenous mix with the asphalt components in situ;
• a second, smaller silo, used for additive dosing: fibers, etc.
• as the machine advances so a transverse rotating milling machine breaks the cohesion of the pre-heated
layer;
• all the milled and added materials are then mixed by a mixing screed operating over the entire width and
thickness to be processed. This screed is operated by alternative transverse movement from left to right; it
has ten rotating mixer heads each one fitted with four fingers and turning both ways to ensure effective
mixing;
• the added or rejuvenating binder is injected during mixing. The binder is added from a tank fitted
permanently on the processing machine;
• the asphalt thus reformed is spread uniformly over the entire width of a heavy paver screed built into the
processing machine, before being spread and compacted by the screed's vibrations and tampers.
Conventional equipment appropriate to the thickness being processed is used for the final compacting.
Photo 1: pre-heater in working order
Sens d'avancement
Gravillons laqués
Chauffe
Fibre
Malaxeur
Décohésionneur
Régénérant - Bitume
Figure 3: SOAVE process
Coated chippings
Heating
Fiber
Mixer
Cohesion breaker
Rejuvenator - Bitumen
– 10 –
juin 2007
Second type
(Figure 4) differs from the first through its type of cohesion breaker and its mixing method
This compact assembly comprises:
• a central drum and two side drums (working width 2.5 m to 4 m) on which are mounted picks. These
picks break the cohesion up to a maximum depth of 10 cm by penetrating the softened asphalt. Two spiral
shafts, one on the right and one on the left, place the broken material in the longitudinal axis of the
machine; a large spray jet operated or not by a to-and-fro transverse movement sprays the added binder;
• a longitudinal mixer of 150 metric tons per hour fitted with two horizontal paddle shafts; the broken
material is loaded onto this by four ejectors;
• a heavy paver screed spreads a regular, uniform layer of processed asphalt
• a temperature-controlled tank with its dosing system for the added binder;
• a silo at the front of the machine, used to dose and lay the coated chippings and, if appropriate, fibers premixed with the chippings;
• a second, smaller silo located just before the cohesion breaker (Photo 3), used to dose and lay the other
additions: polyolefins, fibers, etc.;
• conventional equipment appropriate to the thickness being processed is used for the compacting.
Photo 2: view of the DMF - Cohesion breaker, mixer and paver
Photo 3: cohesion breaker
Figure 4: THERMOCOL process
L'ensemble DMF
Décohésionneur
Malaxeur
Table lourde de finisseur
Cuve à bitume
Trémie gravillons laqués
Trémie fibres de P.E.
Détail
DMF assembly
Cohesion breaker
Mixer
Heavy paver screed
Bitumen tank
Coated chippings silo
PE fibers silo
Detail
– 11 –
juin 2007
Sens d'avancement
Gravillons laqués
Fibres
Régénérant
Bitume
Finisseur
Coated chippings
Fibers
Rejuvenating agent
Bitumen
Paver
– 12 –
juin 2007
Third type
(Figure 5) is identical to the second for the cohesion breaking and mixing, with in addition
the chance to add new asphalt fed from a silo at the head of the machine, transported and spread:
- in front of the mixer (Fig. 5), for incorporation in the rejuvenated asphalts, or
- after mixing (Fig. 6), for grading and leveling by the laying screed.
Appropriate conventional equipment is used for the final compacting in both cases.
Laying
The performance of these machines is dictated by the thickness to be processed, the presence of water in
the asphalt, the need to deal with the interface, the heating surface and the meteorological conditions
(Photo 4).
Average daily performances for thicknesses of 3 to 4 cm over a 4 m width are between 6,000 and 8000 m2;
for thicknesses of 6 to 7 cm, there are between 3,000 and 6,000 m2.
Photo 4: general view of a hot remixing unit
Figure 5: REMIX process (WIRTGEN)
(asphalt added in front of the mixer)
Figure 6: REMIX process (WIRTGEN)
(asphalt added after the mixer)
Sens d'avancement
Trémie d'apport d'enrobés
Added asphalt silo
– 13 –
juin 2007
Preliminary studies
Whatever the problem, a preliminary site survey is absolutely essential. The first investigations
characterize the substrate from various aspects:
• structural: the pavement structure must not be involved except for the bonding of the surface course in
relation to its substrate;
• qualitative: the substrate asphalt may show three types of defect:
- wear,
- cracking of the binder through ageing or fatigue cracking through a bonding failure with respect to its
substrate,
- rutting through creep due to poor matching of traffic, climate and formulation,
• geometric: by a cross-section examination of the extent of the problem and any altimetric constraints.
Where there is rutting, should the entire pavement be processed, a single direction or the slow lane?
If the problem is cracking, it is possible or necessary, to apply a new surface course over and above the
asphalt processing.
For the success of this operation, the compounder has a duty to compile information on the material to be
processed (formulae, material characteristics and inspections), to break down the homogeneous
composition zones and highlight unusual points.
The materials on the site are characterized from samples taken by core sampling or by plates cut from the
asphalt, in the lane axis if rutting is involved.
Sufficient core samples must be taken to be representative of the section being processed. In all
circumstances, this number must be at least fifteen units in Ø 150 mm, for each homogenous section, for
the minimum processing surface.
Half the core sampling should be applied to cracks (longitudinal, star cracks or short transverse cracks) and
the other half to the uncracked asphalt, to obtain a good assessment of the bonding (it is not unknown to
note a lack of bonding in line with a crack, particularly when this covers the entire layer).
Characterization of materials in situ
This involves acquiring the following information:
- thickness and nature of the asphalt layer to be processed,
- bonding or slipping of the interface,
- bulk density,
- aggregate type and grading,
- binder content,
- characteristics of bitumen in situ (penetration, binder softening point, asphaltenes).
A minimum of six or seven binder contents and four or five binder recoveries must be determined per
homogeneous sector to determine its characteristics and be representative of the construction site.
Experience shows:
- the binder content in the old asphalt is slightly less than in the asphalt checked during manufacture,
- there is greater percentage of fines,
- the binder content is generally more widely dispersed,
- it can be useful to check whether or not pollutants are present using simulated distillation in the case of
rutting through creep.
– 14 –
juin 2007
Processing study
Based on the characteristics of the materials in situ and criteria required for the finished product, the
formulation study is used to determine the processing parameters:
• depth,
• type and proportion of additions:
- chippings, pre-coating chippings,
- pre-coated chippings with fiber,
- fibers,
- polyolefins,
- binders,
• extra binder to offset any deficit and losses from burning off the surface section of the asphalt (200 to 400
g/m2), even correct its consistency,
• rejuvenators to adjust both the viscosity and the chemical make-up of the bitumen (any oil company is
normally a source of supply for these rejuvenators).
It is acknowledged that when the penetrability at 25°C of the extracted binder is less than 101/10mm, the
material cannot be recycled.
If the penetrability is higher than 301/10mm, a correction can be made by added bitumen from a lower class,
otherwise adding a rejuvenating agent raises the penetration in the finished product to a value comparable
to new bitumen after coating, without exceeding normal binder doses.
Choosing a rejuvenating rate requires knowledge of the characteristics of the binder being recycled, the
binder dose rate and its targeted characteristics after recycling. The rule of mixtures or supplier
nomographs are used for this purpose.
Formulation testing
Once the techniques, the processing depth and the additions or correcting agents to be applied based on the
type of problem have been defined, the formulation study must schedule the tests to characterize the
product after recycling.
This involves checking through several tests that the expected properties have been obtained after asphalt
recycling. The manufacture of mixes cannot comply with standard NF P 98-250-1, given the base
constituent (old asphalt). The cohesion of the asphalt sample is broken after warming up (usually in an
oven) before mixing the sample in normal fashion with the planned correcting agents and additions.
This sample preparation method (oven drying) is not fully representative of construction site conditions and
it can therefore be useful to apply this heat in the laboratory with infrared radiating panels to simulate the
site conditions: surface burning and time taken to raise the temperature. In this case it is advisable to use
asphalt plates.
The warm-up time depends on the thickness processed; it can take 30 to 45 minutes in three phases of 10 to
15 minutes each and diffusion times without heating of around five minutes.
These hot remixing operations normally only apply to surface asphalts. Based on the type of asphalt chosen
and the requirement level for the formulation study, the mix must comply with criteria cover the results of
tests to determine its performances.
The compounder may decide to try several compositions when a mix satisfying the requirements is
obtained. The mix is subjected to a gyratory compactor (PCG) test and specific checks like a water
resistance examination.
The PCG test, the method's key point, sets the binder content and gives indications on the potential
performances of the mix.
The Duriez test checks that the binder content is greater than the lowest permitted binder content for the
mix and also determines its resistance to water
– 15 –
juin 2007
The rutting test is used to specify:
- the effect of the type of rejuvenating binder
- mix stability
- effect of additives
- validity of the aggregate composition.
– 16 –
juin 2007
Inspections
Operating inspections focus on checking:
• the roadmixing thickness,
• the interface temperatures (higher than 80°C) and the recycled asphalt behind the cohesion breaker,
• aggregate, binder added fiber and addition dose rates,
• forward speed.
The following must be checked on the finished product:
• on samples taken from behind the paver screed:
- binder content and grading,
- penetrability and softening point of the final binder,
• on core samples:
- bulk density to determine the void percentage,
- the remixed thickness,
- bonding to the substrate,
• on site:
- the HSV (texture depth by sand patch) roughness if the roadmixed material is used as a surface course,
- longitudinal evenness.
N.B.
Compared with a new asphalt, the binder content dispersions and bitumen characteristics are fairly high and it is not unusual to obtain
standard deviations in binder content in the order of 0.35%.
This dispersion results from accumulated heterogeneities in the original asphalt and those generated by the
remixing.
Figure 7: without milling
Figure 8: with milling
Couches de roulement décollés de leur support
Traitement jusqu'à l'interface et ajouts ajustés au cas à
traiter
Sans renforcement
Avec renforcement
Solution mixte avec fraisage
Rabotage sur une épaisseur égale à la nouvelle couche de
roulement
Traitement jusqu'à l'interface
Nouvelle couche de roulement
Surface courses slipped from their substrate
Processing up to the interface and additions adjusted to the
case being processed
Without strengthening
With strengthening
Mixed solution with milling
Planing a thickness equal to the new surface course
Processing up to the interface
New surface course
– 17 –
juin 2007
Scope
This technique for restoring surface characteristics, eliminating cracking or rebonding the processed layer
to its substrate applies to clearly-dimensioned pavements or with minimum structural needs.
The fields of application for this technique are as follows:
• rebond thick surfacing to its substrate (Figs. 7 and 8). This processing is sometimes used with a
combination of advance milling over 2 to 3 cm followed by rejuvenating the asphalt layer including the
interface and the upper section of the substrate asphalt (1 to 2 cm) (Photo 5);
• obliterate cracking (Fig. 9) caused by ageing of the binder in the surface courses of road and airport
pavements, by rejuvenating the binder characteristics:
• restore the transverse evenness and macro-texture of a pavement rutted by creep (Fig. 10), by
incorporating into the mix, as appropriate:
- chippings pre-coated with 0.8% bitumen to improve the surface characteristics,
- bitumen to offset the burning and drop in binder content due to the addition of chippings.
- low-density polyolefins in the form of cabling waste or gross product of some 0.4 to 0.8% in relation to the
mix to modify the asphalt's susceptibility to creep, mainly from the effect of reinforcement (Photos 6 and 7).
Photo 5: processing an airport runway
Figure 9: cracked pavement scenario
Fissuration due au vieillissement du bitume
Sans renforcement
Avec renforcement
Figure 10: processing rutted pavements
Cracking due to bitumen ageing
Without strengthening
With strengthening
– 18 –
juin 2007
Couches de roulements orniérées
Ajout de P.E.B.D.
Avec B.B.T.M. pour améliorer les caractéristiques de
surface
Rutted surface courses
Addition of low-density polyethylene (LDPE)
With very thin asphalt to improve the surface characteristics
In the special case of thin or porous asphalts produced with polymer bitumens, the binder characteristics
and dose rate for these asphalts can be restored.
The technological limitations of the process relate to:
- the heating unit capacity,
- operation time,
- thickness of the course to be processed,
- pavement geometry (curve radii too tight),
- meteorological conditions (rain, cold, strong winds),
- the types of material found in the asphalt; the application of this technique may be inadvisable if the
bitumen has aged too much (it is difficult to use too hard a bitumen of Pen25 < 101/10 mm for rejuvenation
purposes).
These techniques are very useful when the initial pavement level must be maintained or when it is
sufficient to process a single lane of a pavement by maintaining the level of adjacent lanes without facing
connection problems to existing structures; the final dimension is in fact achieved by removing a quantity
of old asphalt equivalent to the addition. The process also offers unquestionable ease of operating, for once
processed and compacted, the pavement can be re-opened to traffic shortly after the machine has passed
through.
Photo 6: processing rutted pavements
Photo 7: processing rutted pavements, night work
– 19 –
juin 2007
Performances and behavior
The surfaces processed over the last fifteen or so years can be used for a first assessment of this technique,
which is fairly highly rated among the range of techniques made available to managers by the companies.
This technique applied to materials showing signs of distress - slipping, cracking and creep - can be
perfected, but by virtue of the principle that it is impossible to build new with old, there is no comparison
between a plant-manufactured asphalt and an asphalt hot remixed in situ.
With these restrictions in mind, what then is the conclusion:
• from the heat aspect, experience shows that where the surface temperatures just prior to cohesion
breaking are in the order of 220 to 230°C, temperatures only in the order of 100°C between 6 and 7 cm are
obtained. Thus it is unrealistic to process thicknesses of more than 7 cm without detracting from
performance and therefore profitability, particularly if this involves rebonding two layers.
• from the homogeneity aspect, whatever mixing method is used (horizontal, WIRTGEN system) or vertical
arm (SOAVE system), samples taken from behind the pavers produce the following assessments:
- dispersions (σ) of binder contents noted over a period of twelve years are between 0.3 and 0.47 (Rouen
method); they are linked to the heterogeneity of the coating being recycled, the dispersion of the added
binder, the mixing method and time, the lack of automatic control for the added binder according to the
processed thickness.
- no significant changes in grading, if only an increase in the percentage of fines compared with the
original asphalt,
- dispersion in the binder characteristics after hot remixing is high and the initial objectives can prove
difficult to maintain despite preliminary studies.
• the layer rebonding rate is between 85 and 100%. It relates to the presence of water at the interface, the
meteorological conditions during the work, poor assessment of the interface and sometimes insufficient
heating capacity,
• the surface characteristics measured when a hot remixed asphalt is not covered, show that:
- the average macro-roughness are those obtained from traditional medium coarse asphalts HSv ≥ 0.75, but
with high dispersions,
- the unevenness measured with the longitudinal profile analyzer (APL) 25 has taken great steps forward in
recent years and higher percentages are obtained after work than those in the base asphalt.
• on the long-term behavior aspect, note that the service life for a surface course showing severe distress
and requiring recovering or milling and replacement can be extended for several years by hot remixing in
situ and for a cost equivalent to the price of very thin asphalt surfacing according to the surface areas to be
processed.
The deferred operations given in the table below speak for themselves.
Although this technique does not have full command of all parameters, managers, particularly expressway
managers, find it very useful for processing rutted slow lanes (over four million square meters processed).
On sections with intense traffic, managers appreciate the operating flexibility and minimum inconvenience
for users (the work can be carried out at night with installation and rapid removal of material).
Initial site
Type of problem
Hot remixing operation - Year
Re-use or build-up
1973
Cracking
4 cm hot remix + BBTM - 1989
2001/2002
6 cmAC + 2.5 cm BBTM
1981
Cracking
4 cm hot remix + BBTM - 1989
1994/1995
2.5 cm BBTM
– 20 –
juin 2007
1983
Cracking
Hot remix (rebonding) + BBTM - 1988
1999
7 cm milling + 7 cm BBME
slow lane
1994
Rutting/Creep
Hot remix slow lane - 1995/1996
2001/2002
Localized repairs
BBTM = very thin asphalt
BBME = high-modulus asphalt
– 21 –
juin 2007
Sensitive points
As the special feature of the process is to keep all the asphalt and mix it with the necessary additions, the
mix temperature must be in the order 130°C. Where there is slippage and water presense at the interface, it
is advisable for the temperature at the bottom of the layer to be > 80°C.
When thicknesses of 6 to 7 cm are being processed, it can often be preferable to increase the number of
pre-heaters and extend the heating unit rather than reduce the speed of the machine, to prevent burning and
over-ageing.
A key point in this technique is the study phase, used to define additions required and indirectly to improve
control of the dose rate variations of the various constituents.
It goes without saying that this techniques requires well-trained laying teams and suitable inspections:
grading, binder content, bitumen characteristics, void percentages and surface characteristics.
Particular attention must be paid to start-up areas, potential sources of segregation and risk of stripping.
– 22 –
juin 2007
Future of the technique
In situ hot remixing can result in substantial savings in raw materials - aggregate and bitumen - by re-using
"in situ" all the materials in the thickness of the surfacing being renovated: it thus contributes indirectly to
environmental preservation. The economic conditions and technical progress made over the last ten years
show that this technique has been quite successful, particularly on expressways (Fig. 11), as it is potentially
of interest to road managers, inasmuch as the constant improvement of materials should produce the
homogeneity sought.
Standardized separation of functions for surfacing (binder course + surface course) and the search for high
macro-roughness by using very thin or even porous asphalt will limit the use of this type of technique with
its main niche use of recycling thick high-modulus asphalt layers (6 to 7 cm). Attempts by contractors to
widen the use of very thin and porous asphalts for recycling purposes are dealt with in innovation charters
and are therefore currently being finalized.
Modernization of equipment - heat-controlled binder tanks, automatic binder dosing control systems with
automatic pilot adjusting additions according to the stated thickness to be processed and recording of
addition quantities, pressurized binder injection system, fume recovery and processing to respect the health
and safety of users and staff - is possible if the market is large enough. It is necessary for each unit to
process a minimum of 300,000 m2 every year to depreciate equipment and retain skilled teams.
Hot remixing is part of an overall road network maintenance strategy of the GLAT type (major regional
development links) or expressways under concession; it can increase the service life of surface courses
(this may be doubled) at an advantageous cost and preserve the environment.
It can only be envisaged to process surface areas of more than 20,000 m², given the daily performances
which can reach 6 to 10,000 m²/day for 4 m width under favorable meteorological conditions.
Brakes on developing the technique, namely:
• lobbying of base material producers,
• low bitumen price levels,
• low waste disposal costs,
should see the impact of these parameters rapidly fading. There will remain the disparity of materials,
sufficient number of machines to meet demand, absence of technical regulations and blockages over
traditional techniques.
Mandatory waste recycling from 2002 onwards, environmental safety by re-using the road as a natural
resource deposit and savings in transport should be the driving forces for this technique, above all, if
combined with more traditional techniques, limiting risks taken by managers.
– 23 –
juin 2007
Figure 11: use of the technique
5 000 000 m2 de 1988 à 2002
Autoroutes non concédées
Pistes aéronautiques
Routes départementales
Routes nationales
Autoroutes concédées
5,000,000 m2 from 1988 to 2002
Non-conceded expressways
Airport runways
District roads
State highways
Conceded expressways
– 24 –
juin 2007
Appendix 1
Rejuvenating agents
The choice of rejuvenating agents depends on the problem faced; it is acknowledged that when the
penetrability at 25°C of the binder extracted from an asphalt is less than 10 1/10mm, the material is difficult
to recycle.
There are two possible scenarios for penetrabilities higher than 10:
• the penetration is higher than 30 and can be corrected by addition of bitumen from a higher penetration
class;
• the penetration is lower than 30 and a rejuvenating agent must be added to bring the finished product up
to a value comparable to a value obtained with new bitumen, without exceeding the normal binder
percentage.
The following must be known to determine the rejuvenating agent rate:
• the binder dose and penetration in the asphalt being recycled;
• the target bitumen dose and penetration for the asphalt after recycling.
These data define the recycling binder percentage that must be included in the total binder for the recycled
asphalt (binder added by old asphalt + recycling binder).
The rejuvenation dose rate is determined:
• by calculation using the rule of mixtures
100 x log P = a log P1 + b log P2
with a and b the respective percentages of two penetrability binders P1 and P2.
• by use of nomographs supplied by the petroleum product suppliers:
Sample calculation
In situ recycling without the addition of new aggregate with rejuvenating agent with a fictitious
penetrability of 105 in 6 cm thickness, with:
MVA = 2.35 T/m3
Xv = 5.0 %
XN = 5.7 %
PV = 15 1/10 mm
Rejuvenating agent penetration = 105 1/10 mm
PN = 40 1/10 mm
Xv = Binder content after pre-heating.
With the nomograph, the fraction of rejuvenating agent required is y = 11.1
With the
x 100 = 11.14 %
calculation: y =
i.e.
= 0.646 of targeted binder
– 25 –
juin 2007
Exemple d'abaques de mélange de liant régénérant
Pénétration du liant final
Régénérant / liant final
Sample rejuvenating binder mixing nomographs
Final binder penetration
Rejuvenating agent/final binder
The amount of rejuvenating agent to be added per m2:
V =6 x 2.35
x 10 = 0.84 l/m²
x
The binder content of the asphalt after recycling will therefore be:
V =6 x 2.35
x 10 = 0.84 l/m²
x
i.e. a slight deficit over the set objective of 5.7%.
If the machine advances at 2 m/mn for a 4 m working width, the rejuvenating agent dose rate will be 6.96
l/min.
• Additives
The most commonly used additives are:
- mineral fibers, normally combined with chippings,
- polyethylene (cable waste) or fibers.
– 26 –
juin 2007
Appendix 2
Sample formulation studies
Study consistency
Analyses performed as part of the preliminary survey and the type of problem are used to define the
technique, preparatory work and the additions to be applied.
Based on the adopted processing technique, the formulation study must plan for tests to characterize the
product after recycling. If the targeted goal is to process rutting, a wheel tracking test must check if the
objective is achieved. If the problem involves rejuvenating a very cracked asphalt course due to ageing, it
is important to ensure that the characteristics of the material after processing are acceptable for a surface
course in addition to the rutting resistance.
Actual study scenarios, examples
It seemed appropriate to examine three study scenarios actually carried out to illustrate our comments:
A - Processing cracked asphalt with added plant-manufactured correcting asphalt (repaving),
B - Processing rutting,
C - Processing slippage with asphalt ageing.
– 27 –
juin 2007
A - Repairs to the surface course of the runway at the Tahiti Aerodrome F AAA (Study EJ.
Lefebvre + CETE)
Soundings of the main runway revealed slippage of the surface course and an alarming distress evolution stripping, crazing and presence of water - although the structural quality of the platform was not in doubt.
The choice of technique for the repair work was duty bound to correct the existing defects:
• reduce the stresses in the existing surface course caused by its slipping defect,
• restore the surface state of the surface course,
• take advantage of the work to perform some slight structural strengthening.
The analysis lead to hot remixing of the entire surface course, with structural addition of 3 cm of new
asphalt.
In a single operation with partial maintenance of air traffic, it was possible with this technique to:
- rebond the surface course to its substrate,
- repave this course over 6 cm
- build up fully bonded asphalts by 3 cm, which then became an integral part of the hot remixed layer.
Preliminary survey
The binder content and the density were measured in twenty core samples:
TL = 5.07 % σ = 0.748
min. 4.35% - max. 6.9%
Out of ten samples (grouping of two core samples), the characteristics of the extracted binder and the
grading of the aggregate structure (mean curve below) were determined.
Tests on recovered binder
Sampling zone
1
2
3
4
5
6
7
8
9
10
Av.
Penetrability at 25°C
(in 1/10 mm)
13
12
14
11
10
9
8
9
10
10
10.6
70.8
73.0
77.5
75.4
75.9
77.8
81.8
83.0
81.5
79.5
rounded to
77.6
Ring-and-ball
temperature (°C)
Average asphaltene
content (%)
23.5
Grading
Sieve/mm
14
12.5
10
6.3
3.15
2
0.315
0.08
% passing fraction
asphalt in situ
100
98
82
62
44
34
15
8.4
– 28 –
juin 2007
Objectives of the special technical specifications
Grading:
The aggregate structure curve should integrate as far as possible in the 0/10 envelope in the STBA
specifications.
Mechanical performances:
DURIEZ test
C % 94 to 96
RC > 6 MPa
r/R > 0.75
PCG test
C10 < 90 %
C80 95 to 97%
MARSHALL test Stability > 800 daN
Final binder consistency:
The penetrability at 25°C in 1/10 mn, measured in the final binder after recycling, should be that of a class
60/70 bitumen.
Correcting agents
Added material
0/8 crushed basaltic sand with 12.5% fines.
Added binder
80/100 bitumen mixture, origin Singapore, with added TOTAL MR 50 rejuvenating agent
80/100 bitumen characteristics
- Penetrability at 26°C (1/10 mm): 84
- Ring-and-ball temperature (°C): 45.4
- LCPC penetrability index: - 2.8
- PFEIFFER penetrability index: - 1.2
- Asphaltene content: 8.8 %
Various mixtures were studied:
80/100
60
50
40
MR/50
40
50
60
Hot remixing study
Correcting asphalt feasibility study
The aim was to comprehend rapidly the binder content to be planned for the added asphalt based on:
• binder content or of the richness modulus targeted for the final asphalt,
• binder content of the milled material measured on various core samples from the first batch,
• providing indications at the same time on the theoretical density of the final asphalt.
A drainage test was performed by coating 0/8 at 120°C with a mixture of half 80/100 and half MR50 for
the two binder contents 8.8% and 9.5%.
– 29 –
juin 2007
Changes in PCG compactness according to the binder content. Three formula were
studied:
Formula - Composition
(%)
A
B
C
Aggregates from milled
materials (considered at
5.55% and not 5.07)
67.14
67.24
67.35
BARMAC 0/8 correcting
agent
32.86
32.76
32.65
6,30
3,72
1,28
1,28
6,45
3,73
1,36
1,36
6,62
3,73
1,44
1,44
4.0
4.1
4.2
TOTAL bitumen (%)
- incl. aged binder
- incl. 80/100
- incl. MR 50
Richness modulus of final
asphalt
Batches produced at a temperature of 120° to create ageing conditions similar to those on the site.
Mechanical mixture performances
Formula
A
B
C
1 - Composition (%)
Milled material aggregates: (with
5.55% binder)
67.14
67.24
67.35
BARMAC 0/8 correcting agent
32.86
32.76
32.65
TOTAL bitumen
- incl. aged binder
- incl. 80/100
- incl. MR 50
6,30
3,72
1,28
1,28
6,45
3,73
1,36
1,36
6,62
3,73
1,44
1,44
Richness modulus
4.0
4.1
4.215
Theoretical asphalt density (t/m3)
2.65
2.65
2.644
2 - PCG test
Compactness at n gyrations (%)
- 10 gyrations
- 60 gyrations
- 80 gyrations
86,9
94,0
95,1
88,7
95,7
96,6
89,2
96,0
96,9
160
120
100
Bleeding towards n gyrations
– 30 –
juin 2007
Verification of binder rejuvenation
Formula
A
B
C
Resulting calculated penetrability
60
62
65
57
64
71
53.1
52.1
49.7
Characteristics of recovered binder
- penetrability at 25°C
(in 1/10 mm)
- ring-and-ball temperature (°C)
These results demonstrate that the MR 50 and 80/100 percentages in a 50/50 mixture are very suitable for
binder rejuvenation in the 60/70 range provided for in the special technical specifications.
Study of mechanical performances for the composition adopted
Major bleeding was noted for formula B and C which meant that only asphalts from formula A were
characterized.
Specifications
Values obtained
DURIEZ
- Compactness (%)
- RC (MPa)
- r/R
94 - 96
> 6.0
> 0.75
92.8 (normal mould) d = 2.46
94.5 (dilated mould)(*) d = 2.51
6.0 (normal mould)
0.82 (normal mould)
PCG
- C10 (%)
- C80 (%)
< 90
95 - 97
86.9
95.1
> 800 daN
-
930
97.1
MARSHALL
- Stability (daN)
- Compactness (%)
(*) Due to the planned 9 cm thickness.
Final binder content adjustment in the asphalt
As the percentage of binder in the formula adopted 6.3% (richness modulus 4) was high and near the
maximum permitted on the construction site (specification 3.6 to 3.8), the contract decided to study and
adopt a formula of 6% TOTAL binder to take account also of the tremendous variability of the binder
content in the asphalt being recycled.
(binder content in core samples 5.07%)
(plates for milled materials 5.55%)
This variability prompted the contractor to adopt the following composition:
- milled material aggregates
(considered with 5.4 % binder):
67.00 %
ARMAC
-B
0/8 crushed:
33.00 %
- total binder:
6.00 %
including aged binder:
3.62 %
including 80/100:
1.19 %
including MR 50:
1.19 %
- Richness modulus:
3.8
- Theoretical asphalt density (t/m3):
2.67
– 31 –
juin 2007
Which resulted in an added asphalt formulation with a binder content of 7.22% binder to obtain a recycled
asphalt with 6% binder.
Study conclusions
An examination of the study results led the contractor to propose the NOVATHERM hot remixing process for
the FAAA airport runway, with:
• the following average formulation:
- milled material aggregates:
67% (considered with 5.4 % binder)
- BARMAC 0/8 correcting aggregate: 33%
- total binder content:
6.00% K = 3.8
• added binder: composed of equal proportions of SHELL 80/100 bitumen and TOTAL MR 50 rejuvenating
agent
• added asphalt: made up entirely of BARMAC 0/8 crushed basaltic with a 7.22% dose of added binder
defined above.
Site checks
The site showed the need to readjust the percentage of TOTAL MR 50 in the added binder, namely 44%
rejuvenating agent for 56% 80/100 bitumen.
An LPC rutting test on the composition laid revealed no double coating phenomenon (4% rutting at 30,000
cycles).
Consistency measurements on the binder extracted from the recycled asphalt complied with the required
specifications:
Pen 25°C of the recycled binder:
Asphalt binder content:
5.9 %
68 1/10mm
– 32 –
juin 2007
B - Rutting due to creep Expressway A07 - ASF
The section between Avignon Nord and Avignon Sud was widened to three lanes by the outside in 1992;
unevenness problems when laying the binder course on the east pavement led the contractor to use two
layers 3.5 cm thick instead of the 7 cm 0/14 asphalt provided for in the contract. The compositions of these
two layers proposed by the contractor were adopted by the Construction Manager without the results of the
rutting tests.
This technique produced a longitudinal unevenness, sadly at the cost of the transverse unevenness as
marked rutting was observed in 1994.
AC1 10/14 Rivolet (solid rock)
32%
6/10 Alluvial deposits from Rhône Lacanau
34%
32%
Limestone fines
2%
35/50 Esso
5.42%
AC2 6/10 Alluvial deposits from Rhône Lacanau
60%
40%
35/50 Esso
5.34%
Grading
Sieve
16
14
10
6.3
4.0
2.0
0.315
0.08
% passing
fraction AC1
100
93
60
37
35
34
15.3
7.8
% passing
fraction AC2
100
100
93
43
40
29
14.3
7.1
Preliminary survey
The study commenced with a core sampling campaign intended to recover materials to be studied for
recycling. Forty core samples were taken on the site; they were sawn to the "-6 cm" dimension - the
thickness to be recycled - then hot crumbled to simulate the action of an in situ hot remixing machine.
No slipping was detected at the 1st or 2nd interfaces during core sampling (nominal dimension "-3.5 cm" or
"7 cm").
Thickness AC1
m = 3.5 cm σ 0.3
AC2
m = 3.5 cm σ 0.4
AC1 + BB2 m = 6.8 cm σ 0.55
The resulting material therefore contains:
- the 3.5 cm from the surface course,
- the tack coat,
- the first 2.5 centimeters of the lower layer (3.5 cm nominal thickness).
The aggregate evolution during recycling was considered equivalent to changes caused by the core
sampling.
– 33 –
juin 2007
Estimation of the composition of these "milled materials"
with AC1 56%
AC2 44%
Total binder content
5.38 %
Binder consistency (calculated)
P25 = 25; TBA = 64
Sieve (mm)
14
10
6.3
4
2
0.315
0.08
(% passing fraction as is)
99
77
49
37
31
14.7
7.5
After milling (estimation)
99
79
50
39
32
13
11
Formulation study
Four asphalt compositions were manufactured with these milled materials with various additions to test
them with the wheel tracking test;
- 2/6 Durance for coating
- 0/4 LD Sollac slag for coating
with the following grading:
6.3
4
3.15
2
1
0.5
0.315
0.2
0.08
99
83
76
62
48
38
31
25
12.5
• composition 1: this is the milled material
(re-shaping, no addition)
• composition 2: Milled material
2/6 Durance Rognonas
coated with 2.2% 35/50
• composition 3: Milled material
Solmer 0/4 slag sand
Coated with 15% 50/70
• Composition 4: Milled material
Recovered polyethylene
only; it represents the material after a hot reforming operation
= 90%
= 10%
= 90%
= 10%
= 99%
= 1%
Sieve/mm
14
10
6.3
4
2
0.315
0.08
Compositions 1 and 4
99
78
50
39
34
19
11
Composition 2
99
80
54
40
31
14.4
10.1
Composition 3
99
80
54
43
32
13.2
11.1
– 34 –
juin 2007
Wheel tracking tests
Composition
1
2
3
4
0.3 %
1.2 %
4%
8%
Sand patch test (mm)
0.71
1.3
0.62
1.1
Rutting test (at 60°C)
10.6% with
104 cycles
4 % with
3*104 cycles
10.1 % with
3*104 cycles
2.9 % with
3*104 cycles
Percentage of asphalt voids
For the compositions subjected to the wheel tracking tests, the binder contents and consistency estimated
after recycling are show in the table below.
Composition
1
2
3
4
5.38
5.06
5.26
5.38
(+ 1% PE)
Penetrability at 26°C (10-1 mm)
25
25
26
/
Ring-and-ball temperature (°C)
64
64
62
/
Binder content (%)
Comments
Simple hot reforming (solution 1) is unsatisfactory; the material is very easy to handle (voids = 0.3%) and
liable to rutting.
Correction with a coated slag sand is also not suitable, for the same reason.
Solutions 2 (correction with 10% 2/6 coated chippings) and 4 (correction with 1% polyethylene) produce
equivalent and satisfactory behavior in terms of rutting.
A solution can therefore be chosen based on secondary criteria relating to its reliability and practical
implications.
Addition of coated 2/6:
Very reliable solution, the addition is easy to manufacture and its quality and quantity can be controlled;
however, the addition of 10% material creates an over-thickness of some 6 mm on the slow lane compared
with the other two lanes.
Addition of polyethylene:
The addition dose rate is fairly difficult to control and the homogeneity of the addition behind a hot
remixing machine is not easily discernible. In addition, inspection by sample analysis becomes problematic
and there is not method of controlling the dose rate of the addition, apart from looping.
On the plus side, recycling is at a constant volume (no over-thickness) and the results obtained on several
sites are satisfactory.
– 35 –
juin 2007
Site
The solution finally adopted by the Construction Manager was to add coated Durance chippings with 2.2%
35/50 bitumen and 0.6% polyolefins (cable waste).
The daily polyolefin dose was achieved by bringing the amount of PE consumed every day to the
theoretical tonnage of asphalt reprocessed in situ.
This calculation method was also applied to the pre-coated 2/6.
Binder content inspections:
Theoretical 5.1%
Average
4.88% (n = 18)
0.26%
σ
Pre-coated chippings
2.4% for 2.2%.
Grading
Sieve
20
14
12.5
10
8
6.3
4
2
0.315
0.008
Theoretical (%)
100
99
95
81
62
46
39
29
15
7.2
Average (%)
100
98.7
94.2
75.4
58.9
46.2
37.3
27.1
13.5
7.8
Standard
deviation (%)
/
0.8
1.5
4.6
6.3
6.5
4.3
2.6
1.0
0.6
Grading dispersions are, in our opinion, linked partly to variations in the introduction of pre-coated 2/6,
where the in-plant processing caused the 4/6 fraction to drop and the fines content to rise.
Laying
The bulk density gradient was measured on core samples taken in situ. The measurements were used to
calculate an average bulk density and determine the approximate thickness of the hot remixed layer.
Thickness
- number of measurements
- theoretical
- average
- standard deviation
Percentage of voids
- number of measurements 22
- average
7.1%
- standard deviation
2.4%
22
6 cm
4.92 cm
0.69 cm
The thicknesses of the hot remixed layer are only slightly dispersed around an average lower than the
planned thickness; the void percentages are very dispersed.
– 36 –
juin 2007
C - Asphalt cracked by ageing, slipped from its substrate (Expressway A07 - 1988) - ASF
The problem was as follows: the high-modulus basalt asphalt in situ laid 7 cm thick was cracked by fatigue
(slipping) and ageing of the binder.
The work involved:
• milling the surface course on both Expressway lanes (2 cm),
• hot remixing over 6 cm the asphalt in situ (to reinstate the slipped interface),
• lay a very thin asphalt of 50 to 55 kg/m2.
Preliminary survey
The tests performed with the flow meter when laying the surface course (1983) returned a binder content of
5.7%.
Given the distress observed, the core samples revealed a 5.48% binder content (TOTAL study). New
investigations by the contract holder returned a 5.1% binder content only.
Objectives of tender regulations:
• increase the binder content to 6.2%
• rejuvenate the bitumen to obtain:
- penetration between 40 and 50 1/10 mm
- binder softening point between 50 and 60°C
• obtain a good tack (100%) and compactness of the recycled asphalt of between 91 and 98%.
Studies
Three TOTAL rejuvenating binders were envisaged - MR5, MR10 and MR50.
A rutting test performed on asphalt sampled on the site before hot remixing with 0.65% in asphalt weight
of the MR5 rejuvenating agent added in the laboratory produced the following results:
• binder content before rejuvenation: % 5.3
• binder content after rejuvenation: % 5.7
Binder characteristics
Before rejuvenation
After rejuvenation
PeN 25°C
10 mm/10
32
TBA
> 80
63.5
FRAASS
+9
- 5.5
Asphaltenes
29.9 %
26.5 %
Compactness results obtained in the laboratory: 96.3 to 97.3%
Wheel tracking test results: 60°C 30,000 cycles 3.4%
Comments
Binder penetration in the old asphalt is very low. The addition of 0.655 MR5 should have resulted in a
higher binder dose rate; this difference could be caused by rejuvenating agent dispersion problems in the
laboratory.
– 37 –
juin 2007
A few test results
Binder
PeN 25°C
TBA
Asphaltenes
Asphalts
31 to 67
51.2 60.2°C
18.8 21.8%
Binder content
Compactness
Layer bonding
Thickness
5.42 % (σ = 0.45) n = 93
92.4 % (σ = 3.12)
89.2%
5.1 cm (σ = 0.6)
Comments
Low, dispersed binder content:
• fairly dispersed binder characteristics
• efficient bonding
• significant amount of water in the asphalt
• satisfactory behavior after ten years in service with no surface maintenance or repair. The current central
lane (former fast lane) is still in good state after fourteen years.
– 38 –
juin 2007
Ever-increasing economic and environmental constraints are
pushing road professionals to take an interest in potential natural
material deposits that exist in pavements being demolished or
renovated.
Techniques known as hot remixing, hot reforming or repaving are
grouped under the single term of in situ hot remixing. This term
groups all the in situ bituminous asphalt recycling operations by
heating, pavement scarification, mixing with or without additions
(aggregates with or without pre-coating, binders, additives, etc) and
re-laying the mix.
This document is available and can be downloaded on Sétra website:
http://www.setra.equipement.gouv.fr
Cover - Photographers: L R d'Autun et entreprises A PPI A - C OLAS - E UROVIA - S CREG - W IRTGEN
The Sétra authorization is required for reproduction of this document (all or even part)
© 2007 Sétra - Reference: 0731A - ISRN: EQ-SETRA--07-ED29—FR+ENG
The Sétra belongs
to the Scientific and
Technical Network (RST)
of the French Public
Work Ministry

gouv.fr lacanau site

Transcription

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