Workability of warm mix asphalt additives and mechanical property characterization of asphalt concrete
Warm mix asphalt (WMA) technology offers a promising solution to address the ecological concern of asphalt mixtures. Warm asphalt (WA), is expected to be a sustainable paving technology that integrates energy conservation, noise reduction, and performance optimization. This study aims to characterize and compare the engineering properties of WA mixture prepared with various WMA additives. To achieve this goal, WA mixtures were prepared with seven different WMA additives, including Adgezol 3-TD, DAD-TA2, Azol 1007, Cecabase RT 945, DAD-TA, Doros-T and Amdor TS-1. Comprehensive laboratory tests were conducted to characterize their workability and engineering properties, including penetration, fragility and softening temperature of bitumen, and dynamic viscosity. According to the experimental results, WMA additives including Adgezol 3-TD, DAD-TA2, Doros-T and Azol 1007 provided a 30% reduction in dynamic viscosity of modified bitumen; however, with such WMA additives as DAD-TA, Cecabase RT 945 and Amdor TS-1 no reduction in dynamic viscosity of modified bitumen was observed. Coefficients that consider the complex of physical, mechanical, technological and economic properties, as well as a generalized criterion (Fk) for the technical and economic efficiency of chemical additives were developed. It was proposed to divide warm mix additives into two groups: additives that improve the efficiency of bitumen by 5% (Fk≥1.05) or more, as well as additives that do not improve the efficiency of bitumen by more than 5% (Fk≤1.05), that is, have no significant effect on the properties. Comprehensive laboratory tests were conducted to characterize their workability and mechanical properties, including moisture susceptibility. According to the experimental results, only with Cecabase RT 945 and DAD-TA one can achieve compliance with regulatory requirements for hot asphalt concrete. The influence of warm mix additives on the structure of bitumen was studied. Using the Arrhenius equation, the change in the activation energy required to overcome the potential (kinetic) barrier of the bitumen with the surfactants had been calculated. The workability of warm mix additives was investigated, on the basis of which their classification was proposed.