Highway Research Record

II. PAVEMENT ENGINEERING AND PAVING MATERIALS
2. FLEXIBLE PAVEMENT
NEW PROJECTS
Recycling of Pavement Materials

Date of Start: April 2004
(i) Larsen and Toubro Limited, ECC Division, Chennai. (R, S, I)
(ii) Indian Institute of Technology, Chennai (R, S, I)

Scope & Objectives
(i) To find out the properties of aged bitumen from an existing pavement and restoring its original properties by adding      optimum quantity of rejuvenator.
(ii) To correct the reclaimed material with proper mix design.

Methodology

Rehabilitation, upgradation and maintenance of any road transportation system depend on the fiscal resources to finance the system. The commonly used recycling methods are:
(1) Hot mix recycling,
(2) hot in-place recycling,
(3) cold in-place recycling, and
(4) full depth reclamation.
In the cold in-place recycling process, the existing Hot Mix Asphalt (HMA) pavement is milled to a depth of 75 to 100 mm. The Reclaimed Asphalt Pavement (RAP) is reduced, if needed, and mixed with recycling agent, such as asphalt binder emulsion, fly ash, cement, lime, or other stabilizing agents. The HMA is then placed and compacted as a base course. A wearing course is then applied.
In this project, 25 core samples and 25 kg of scarified bituminous materials were collected from the existing pavement structure located in South India. The existing pavement was composed of 50 mm thick base course layer of bituminous material followed by the 250 mm thick water bound macadam as the base course over subgrade of 500 mm thick. The samples were collected at different wheel path locations along the length of the road.

Conclusions

(i) The aged bitumen having penetration value of around 40, softening point of 53oC was rejuvenated to penetration and      softening values of 65 and 54oC respectively.
(ii) The reclaimed bituminous material aggregate gradation showed the presence of more fine particles due to vehicular traffic.      The reclaimed material was corrected by the addition of fresh aggregates of required sieve size to the desired gradation .
(iii) The Marshall stability test done on the recycled samples showed values conforming to the MORTH specifications. The aging       of the bitumen, which causes loss in the binding property, was restored to optimum extent as per the results obtained by      the Brookfield viscometer test.

Significance / Utilization Potential

By adopting the recycling process, significant savings can be obtained. The savings can go up if the demand on fresh aggregates for the gradation correction is less. Besides the saving in direct cost, there are significant indirect cost savings in terms of conservation of materials and energy as compared to the construction of new pavement structure.

Recommendations
(i) Characterization of aging of bitumen by dynamic shear rheometer.
(ii) Long-term performance of rejuvenated bitumen pavement structures.

Reports/Publications
“Recycling of Pavement Materials”, M. Azad Ali, M.Tech Thesis, L&T ECC LTD and IIT Madras collaborative research program.