Rutting Susceptibility and Moisture Damage of Asphalt Mixes Containing RAP and SASOBIT (WMA) In Pakistan

Abstract

Recycled Asphalt Pavement (RAP) use in pavement has increased a lot from the last two decades. RAP usage has now become common practice in many countries. Highway agencies around the world are endeavoring to use larger quantities of reclaimed asphalt pavement (RAP) in order to meet not only economical and environmental friendly but also to preserve natural resource and similar or even better performing hot mix asphalt (HMA) mixtures. Comprehensive road networks are a basis for economic development of any country. Overtime damages like rutting, moisture damage and cracking renders the pavement inadequate to serve the traffic. The use of reclaimed asphalt pavement (RAP) serves a distinct part in achieving the national goal of prosperity. This research work presents an experimental study to evaluate the effect of different percentages of RAP on the volumetric properties of asphalt mixtures. Mix designs of one aggregate source and a RAP source with and without addition of 2% Sasobit for warm mix asphalt (WMA) using 12.5 mm nominal maximum aggregate size were prepared. RAP material gradation was found and blended in the virgin aggregate gradation to get approximately our desired gradation with in specified limits of NHA Class B. The mix designs included a control mix with 0% RAP and six samples of HMAs with 10%, 20%, 30%, 45%, 60% and 100% RAP to get an optimal percentage on which performance testing to be done after finding out the volumetric of RAP containing mixtures. NHA class-B wearing course gradation, NRL penetration grade of 60-70, aggregate source of Margalla, 2% Sasobit for WMA mixes and RAP from Islamabad Lahore Motorway (M-2) were used in this study. This research-study undertakes the rutting susceptibility and moisture damage in RAP incorporated asphalt mixes using Hamburg Wheel Tracking Device (HWTD). Rutting resistance of only RAP containing mixture is increased up to 18.18% for 20% RAP and RAP containing WMA increased up to 29.12 % for 20% RAP with 2% Sasobit, as compared to the controlled mixtures. Moisture damage results at 50°C temperature of water showed 21.55% increased resistance for 20% RAP and 16.54 % for mix containing 20% RAP with 2% Sasobit, in comparison to the controlled mixtures. This research showed that all tested HMAs with RAP and WMAs with both RAP and Sasobit performed better than the mixtures prepared with virgin aggregate. Cost comparison of control mix and RAP containing mixture was done on major asphalt production. Comparison shows that using up to 20% RAP in HMA mixture can save total cost up-to 22% and by using up to 20% RAP with 2% Sasobit in WMA mixture total cost can be up-to 19%.