Investigating the moisture susceptibility of warm asphalt mixtures modified by sasobit redux (SR)

Environmental and health concerns have been increasing in the road construction industry. Hot Mix Asphalt (HMA) is produced at (150-170) degrees C. As a result, efforts were directed to reduce the mixing and compaction temperatures of HMA keeping safely technical properties. Warm Mix Asphalt (WMA) is considered one of the good solutions to reduce energy consumption, gas emissions and keep a healthy environment. WMA was produced using different additives. Sasobit redux (SR) is a new material proposed to act as a warm mix additive; however limited research was conducted to evaluate the performance of WMA modified with SR. This paper aims to evaluate and enhance various properties of asphalt binder and mixtures modified with SR. The SR content varied from 0 to 5% by weight of bitumen. Penetration, softening point, rotational viscosity, complex shear modulus (G*), phase angle (delta), percent recovery (%R), and non-recoverable creep compliance (Jnr) were evaluated for control and modified bitumen. Different asphalt mixtures were prepared using control and modified bitumen. Two different mixed gradations (4C and 3B) were used. Marshall, wheel tracking, indirect tensile strength, unconfined compression, the Cantabro test, and moisture susceptibility tests were carried out to evaluate the performance of the mixtures. The results showed that 2.5% of SR resulted in reducing mixing and compaction temperatures, reaching 117 and 111 degrees C, respectively. At 2.5% SR, binder viscosity was reduced by 89% at 135 degrees C, the softening point increased by 45%, and penetration decreased by 24% when compared to the control binder. SR enhanced Marshall stability, flow, Marshall Quotient, resistance to moisture damage, and resistance to rutting. The Marshall stability increased by 24 and 25% for both gradation (4C) and (3B) at optimum SR content. The rut depth values of modified asphalt mixes for gradations 4C and 3B decreased by 22 and 28%, respectively.