Table of Contents

4.2 Recycled Asphalt Pavement (RAP)

Recycled asphalt pavement (RAP) has been used successfully for many years in road rehabilitation. However, the acceptance and understanding of RAP as a reliable and soundly performing material is not universal despite its apparent reported cost savings.

Similar medium- to long-term qualitative studies need to be conducted in Australia before RAP can be a standard material for pavement construction and maintenance. In addition, investigation into the optimal proportion of RAP that produces the greatest GHG emission reduction consistent with similar long-term performance of normal asphalt pavements is being addressed (Austroads 2010a). RAP is often brought in from a stockpile. However, it is possible to recycle asphalt on site when rehabilitating a pavement. This has been practiced internationally for many years with reasonable results; however, it requires specialised equipment (Austroads 2010a).

Two examples of products developed from RAP in South Australia are provided in Case Study 2.

Case Study 2: Recycled Materials Developed from RAP

ResourceCo was established in South Australia in 1993. It is South Australia’s largest recycler of C&D waste. In the road infrastructure area it produces minus 20 mm granular pavement materials marketed as ‘Bitumate’ and ‘Bitumix’. ‘Bitumate’ is made from reclaimed clean asphalt and pavement material that is free of contaminants. ‘Bitumate’ is used as a granular unsealed pavement surfacing and low-traffic basecourses. ‘Bitumix’ is manufactured from ‘Bitumate’ with a high float bitumen emulsion added at specified dose rates. ‘Bitumix’ is used as an alternative to traditional deep lift asphalt with a wearing course asphalt overlaid on top. It is only used as a wearing course in low-traffic areas with a minimum thickness of 50 mm.

Independent testing (Andrews et al. 2004) of both ‘Bitumate’ and ‘Bitumix’ showed similar properties to more traditional materials that would be used in their respective applications under laboratory and post-construction testing. The long-term performance of these materials was not available at the time of this testing.

Because of its physical properties, ‘Bitumate’ is expected to perform differently to traditional pavement materials. A summary of the laboratory test results is presented in Table 4.1. The retention of the residual bitumen binder during the processing of ‘Bitumate’ is expected to improve the mechanical interlocking and binding of each particle in the pavement. Consequently, the benefits derived are: reduced dust generation from traffic, longer life pavements, reduced number of maintenance cycles and costs, and reduced land fill disposal due to using recycled asphalt. The oldest application of ‘Bitumate’ is about 10 years; anecdotal observation is that it appears to have performed satisfactorily to date.

In terms of ‘Bitumix’, the addition of the emulsion partially reactivates the residual bitumen binder retained during the manufacturing process. A summary of the laboratory test results for several types of ‘Bitumix’ is presented in Table 4.2. This increased total binder content is expected to further improve the mechanical interlocking and binding of each particle within the pavement. Benefits are similar to those claimed for ‘Bitumate’ with the addition of being able to be laid cold and kept for several days before being applied. Similar to ‘Bitumate’, the oldest application of ‘Bitumix’ is about 10 years and anecdotal observation suggests that it also appears to have performed satisfactorily to date.

Table 4.1: Laboratory test results: ‘Bitumate’

TestTest procedureGrading based specification limits
Sieve Size mmPer cent Finer
Particle size distributionTSA –MAT-TP14126.5100
19.090 - 100
13.274 - 96
9.561 - 85
4.7542 - 66
2.3628 - 50
0.42511 - 27
0.0754 - 14
Liquid limitAS 1289 3.2.2Max 28%
Plasticity IndexAS 1289 3.3.1Min 1% Max 8%
Linear ShrinkageAS 1289 3.4.1Max 4%
LA Abrasion Grading BAS 1141 .23: 2009Max 45%
Foreign Materials Type 2
(Plaster, clay, friable material)RTA-NSW T276Max 1%
Foreign Materials Type 3
(Plastic, rubber, wood)RTA-NSW T276Max 0.5%
Bitumen content Max 4%

Source: ResourceCo (2017).

Table 4.2: Laboratory test results: ‘Bitumix’

Test procedureManufacturing tolerance
Quality control tests
Product20 mm Bitumix14 mm Bitumix10 mm Bitumix
Sieve size mmPercent passing
Particle size distribution53   
37.5   
26.5100  
19.090 - 100100 
13.274 - 9695 - 100100
9.561 - 8574 - 9690 - 100
4.7542 - 6661 - 8560 - 85
2.3628 - 5042 – 6035 - 55

TSA –MAT-TP141

(DPTI n.d.)

0.42511 - 2711 - 3510 – 45
0.0754 - 144 - 145 - 15
AS1289 3.2.2Liquid limitMax 28%
AS1289 3.3.1Plasticity IndexMin 1% Max 8%
AS1289 3.4.1Linear ShrinkageMax 4%
AS1141.23LA Abrasion Grading BMax 45%
TSA-MAT-TP470
(DPTI n.d.)
Bitumen contentMax 4%
Added binderEmulsion 
Added binderCement, lime or polymer 

Source: ResourceCo (2017).