Evaluation of the Impact of Silo Storage on Thermal Cracking of the Hot Mix Asphalt with RAP

The use of Reclaimed Asphalt Pavement (RAP) in Hot Mix Asphalt (HMA) production is consistent with the concept of sustainability and when designed and constructed properly, it can potentially provide a more cost-effective alternative to conventional road practices. However, RAP is suspected to have negative effects on thermal cracking resistance of Hot Mix Asphalt mixes. The extent of blending between aged binder and virgin binder in asphalt mixtures could affect both the performance of the produced HMA and the economic competitiveness of the recycling process. During the production process of HMA with RAP, it is generally understood that a partial blending occurs between aged and virgin binders. Yet, a limited number of studies have considered the time-temperature effects of the silo storage on the performance of HMA RAP mixes. In this study, the effect of silo storage time on mitigation of thermal cracking of the HMA containing RAP is examined. HMA samples of HL-3 and HL-8 mixes, designed with 15% and 30% RAP respectively, were collected after production from the asphalt plant at different silo-storage intervals (1, 4, 8, and 12 hours), with their temperature being closely monitored and recorded. The thermal cracking resistance of the resulting mixes were characterised using Thermal Stress Restrained Specimen Test (TSRST). Results indicate that the samples collected after 8 and 12 hours of silo storage exhibited an improvement in the thermal cracking resistance accompanied with a reduction in their corresponding stiffness compared to those collected at 0 hours. These results indicate that silo storage would then improve the blending between aged and virgin binders and improve the low temperature behaviour of the asphalt mix.