Performance of hot mix asphalt incorporating treated crumb rubber and treated plastic additives using dry process

Abstract

Pavement defect shortens the service life of mixture, demonstrated by failures such as cracking, rutting, and stripping. Incorporating additives into conventional mixture is an approach to improve its performance and service life. Therefore, this research was conducted in three phases using treated crumb rubber (TCR) and treated plastic (TP) as additives in the mixture. In the first phase, both additives were characterised using thermogravimetric analysis (TGA), field-emission scanning electron microscope (FE-SEM) and energy dispersive x-ray (EDX). Eight different percentages of TCR from 0.25 % to 5.0 % and six different percentages of TP from 0.25 % to 3.0 % were incorporated into a 14 mm nominal maximum aggregate size (AC14) mixture using a dry process. Marshall test was carried out to determine the optimum percentage of the additives. Results show that the mixtures of 0.75 % TCR and 0.75 % TP met all the required specifications and were selected as the optimum percentage. The mixtures with 0.75 % TCR and 0.75 % TP improved the fatigue cracking and rutting resistance compared to the conventional mixture. In the second phase, mechanical tests such as resilient modulus, dynamic creep, rutting and moisture damage of compacted and uncompacted mixtures and scanning electron microscope (SEM) were conducted to evaluate the performance of the mixture containing TCR and TP. Although the modified mixtures with both additives showed better performance than the conventional mixture, the TCR mixture was susceptible to rutting and moisture damage, while the TP mixture was identified with stripping potential. To overcome the issues, a combination of TCR and TP was investigated in the final phase. A mixture with 50 % TCR and 50 % TP shows 37 %, 44 % and 4 % improvement in the fatigue, rutting and moisture damage resistance, respectively, compared to the conventional mixture. It can be concluded that the combination of TCR-TP in mixture using dry process can be used as an alternative mixture to improve pavement performance.