Effects of hydrated lime on mechanical behaviour of asphalt concrete at nanoscale

Asphalt concrete (AC) is a mix of mineral aggregates and natural sand held together with a binder of bitumen. This paper presents the effects of adding hydrated lime (HL) to AC on the nanoscaled mechanical properties. Two hot mixes of AC were used (one control mix and one mix with HL). Nanoindentation was conducted to study the load–displacement behaviour at nanoscale and evaluate the nanomechanical (elastic modulus and hardness) properties of AC across the mastic, matrix and aggregate phases. It was observed that the HL-containing samples have greater resistance to deformation at nanoscale in the mastic and matrix phases. The resistance is more pronounced in the mastic phase. There is also strong evidence suggesting that HL has the most potent effect on the mastic phase, with significant increase in elastic modulus and hardness

An Investigation into the Use of Ultrasonic Wave Transmission Techniques to Evaluate Air Voids in Asphalt

Air voids and their distribution are very important factors that influence the structural performance of asphalt pavements under traffic loading. Several simple methods exist for the overall (macro) evaluation of air voids in asphalt mixture, however there are very few methods available to assess their micro-distribution within an asphalt matrix. While X-ray methodologies have historically been used by researchers to investigate the complex distribution of air voids in asphalt mixtures, both cost and ease of application do not support their widespread use. The use of non-destructive ultrasonic wave transmission techniques (UWT) is outlined in the paper as an accurate, rapid and economical alternative method. UWT is able to both estimate the total air voids and their distribution within laboratory compacted asphalt samples. Asphalt samples with 14 mm nominal aggregate size manufactured with three types of bitumen; Class 320 (C320), Multigrade (M1000) and a SBS Polymer Modified Bitumen (PMB-A5S) and with different air voids were analysed using UWT techniques. The results have shown that UWT testing has the potential of being a rapid and cost-effective method of estimating total air voids and their distribution in laboratory asphalt mixtures