Highway Research Record

VI. RESEARCH WORK DONE IN ACADEMIC INSTITUTIONS RELATED TO THESIS WORK
B. PAVEMENT ENGINEERING AND PAVING MATERIALS
Application of Recycling Techniques in Bituminous Pavement Overlays

Date of Start:August 2004
Indian Institute of Technology Madras (R, C)

Scope and Objective
(i) To study the engineering properties of bitumen and bituminous mixes obtained from core samples from in-service      pavements and study the effect of traffic, ageing etc.,
(ii) To study the properties of the aged bitumen by adding rejuvenators / recycling agent and determine the optimum      quantity of rejuvenator to be added
(iii) To find the gradation of the aggregates in the core sample and estimate the quantity of fresh aggregates to be added (if      necessary)
(iv) Redesigning the bituminous mix by Marshall mix design method and study the mix properties
(v) Carryout an economic analysis and quantify the advantages of the adoption of the recycling technologies.

Methodology
In the present thesis, properties of an aged bituminous pavement are analysed by extricating bituminous surface. The binder and the aggregates are separated and tested. The binder was tested for its properties and aggregates were subjected to sieve analysis to find the gradation of the sample. The rejuvenator was added at different percentages to rejuvenate the aged asphalt back to its original characteristics.
After the addition of fresh aggregates and binder, the mix was then recycled. This recycled bituminous material was then tested for its properties, which satisfied the MORTH requirements. Further, the properties of rejuvenated bitumen were then tested and compared with the virgin bitumen and aged bitumen.

Findings and Conclusions

The recycling process is a viable technology. The aged bitumen can be rejuvenated back to its original form in terms of penetration value, softening point and ductility. The aged bitumen having penetration value of around 40, softening point of 53 degree centigrade was rejuvenated to penetration and softening point values of 65 and 54 degree centigrade respectively after the addition of optimum rejuvenator content.
The aging of the bitumen which causes loss in the binding property was restored to certain/elaborate extent as explained by the dynamic shear rheometer tests and Brookfield viscometer test.
By adopting the recycling process, cost saving to the tune of 23% per lane per km can be achieved. This can go up if the fresh requirement of aggregates required 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.