Investigating the Effect of Asphalt Ageing on the Mechanical Properties of Asphalt Mixtures Made by Limestone and Siliceous Aggregates

In this study the effect of aggregate source on the ageing of asphalt binder ageing in asphalt mixtures has been investigated. Limestone and siliceous aggregates have been used for making specimens with the same binder and aggregate gradation. The mixtures were tested after subjecting to short and long term ageing, and the properties of the mixtures after each ageing condition have been evaluated and compared.  Marshall Stability, flow and Marshall Quotient (MQ), indirect tensile strength (ITS) and moisture susceptibility have been investigated. Results reveal that the mixture made by limestone aggregates has higher Marshall Stability, Marshall Quotient, and indirect tensile strength than the mixture made by siliceous aggregates, while the mixture made by siliceous aggregates has higher moisture susceptibility. The difference between the moisture susceptibility of the mixtures is more after ageing. Results also show that ageing results in increase of Marshall Stability, Marshall Quotient, the ITS in dry condition, and decrease of Marshall flow and tensile strength ratio.  It was found that long term ageing condition of 7 days at 85°C, results in 13 and 62% improvement in Marshall stability and ITS, respectively, in the mixture made by limestone aggregates, while these values for the siliceous aggregates are 17 and 32%. The effect of ageing on the Marshall Properties and moisture susceptibility for the mixture made by siliceous aggregates is higher than that for the mixtures made by limestone aggregates. However, the effect of ageing on the ITS in dry condition is higher for the mixture made by limestone aggregates.