Warm mix asphalt incorporated with cup lump rubber and palm oil fuel ash

Abstract

Natural or synthetic rubber has become a preferred bitumen modifier to produce more durable asphalt, notably among them is cup lump rubber (CLR). While there are several benefits of modifying bitumen with CLR, there are concerns about the high energy consumption, cost, and excessive fume emissions. Warm-mix asphalt (WMA) represents technology that allows a reduction in mixing and compaction temperatures of asphalt mixes. Since its inception, many agencies around the world have shifted from producing hot mix asphalt (HMA) to WMA. However, little documented research explore the application of CLR in WMA. This research is aimed at determining the performance of WMA incorporating CLR and palm oil fuel ash (POFA). It combined the success achieved by CLR in bitumen modification (CMB) with the advantages of WMA technology. The CLR is used to modify 60/70 PEN bitumen. Evotherm is then added to produce warm cup lump modified bitumen (WCMB). WCMB is used in preparing dense-graded AC14 mix and the performance in term of strength, rutting, fatigue, moisture susceptibility, and thermal cracking was determined. Due to the propensity of WMA to moisture susceptibility, POFA was incorporated to the bitumen (wet process) to counter any potential adhesive failure of the warm cup lump modified asphalt (WCMA) mixture. The results show that the WCMA mixture possess excellent moisture damage resistance with 99% tensile strength ratio (TSR). This was achieved despite reducing more than 40 ? of the conventional asphalt production temperature. Asphalt Pavement Analyser (APA) test result also shows that the mixture displayed less than 2 mm rut depth at 8000 cycles. Converting hot cup lump modified asphalt (HCMA) into a WMA leads to realising the highest resilient modulus, thus having a higher cracking resistance than in HMA. Furthermore, the outcome from Bending Beam Rheometer (BBR) test revealed that the addition of Evotherm remarkably improved the low-temperature performance of CMB, with the bitumen capable of withstanding more than -32 ?. Fourier Transform Infrared (FTIR) analysis found a slight reduction in some of the double and single bonds stretching without affecting the main functional groups. Atomic Force Microscopy (AFM) scan also revealed a clear dispersion of the bee-structure with distinct separation of para-phase from peri-phase. Contact angle test result confirms that POFA modification slightly improved the moisture damage resistance of WMA by increasing its hydrophobicity from 98° to 101°. Similar marginal improvement was observed from the rutting test results. This lead to the conclusion that CMB is successfully applied in WMA without compromising the mechanical performance of the mix. The 40 ? reduction in the mixing and compaction temperature of HCMA amounts to significant reduction in the amount of Green House Gas (GHG) emissions to the environment and translates to significant monetary savings to the government and contractors.