Effect of hospital waste pyrolysis hydrocarbon (HWPHC) on fracture behavior of Warm Mix asphalt (WMA) under freeze–thaw damage (FTD)

Abstract

Warm mix asphalt (WMA) is more susceptible to macroscopic cracks than other mixtures due to insufficient aggregate-bitumen adhesion, especially at low temperatures. In this study, the behavior of low-temperature cracking (LTC) and intermediate temperature cracking (ITC) of WMA mixture with and without the environmentally friendly additive called hospital waste pyrolysis hydrocarbon (HWPHC) was evaluated at −15 and +15°C under mode I loading conditions using three geometries: symmetric specimen SCB, classical-modified specimen SCB-1, and symmetric specimen ENDB. In order to determine the effect of freeze–thaw damage (FTD) on the mixtures, samples with and without the HWPHC additives were subjected to 0 and 3 FTD cycles. The results showed that adding 3 % and 6 % of HWPHC additive increased the fracture resistance of the samples, i.e., fracture energy (GF) and fracture toughness (KIC) at temperatures of ±15 °C using all three mentioned geometries under 0 and 3 FTD cycles. At temperatures of ±15 °C and for all mixtures with and without additives, the average GF and KIC for symmetric specimen ENDB (vertical crack) are lower and higher than for symmetric specimen SCB (vertical crack) and classical-modified specimen SCB-1 (angular crack), respectively. Therefore, the complete fracture potential and crack initiation for the ENDB geometry were higher and lower than the other two geometries (under 0 and 3 FTD cycles). Also, at temperatures of ±15 °C and under 0 and 3 FTD cycles, the flexibility indices showed that adding HWPHC reduced the flexibility of the WMA mixture slightly. Finally, the increase in the fracture resistance and resistance to elastic deformation of the mixtures modified with HWPHC additive was achieved using two Tensile Stiffness Index (TSI) and Tensile Strength (TS) indices. Therefore, in addition to helping to reduce the amount of environmental waste and increase cleaner production, the mentioned mixtures can be used to improve the LTC and ITC fracture performance of the WMA mixture under mode I and FTD conditions.