Search

This paper evaluates the fracture properties of mixtures subjected to different short-term ageing conditions obtained from semi-circular bending test. Response Surface Method (RSM) was used to develop an experimental matrix based on the central composite design. Ageing temperature, ageing duration and duration in humidity and ultraviolet chamber were selected as short-term ageing parameters, while fracture toughness or stress intensity factor (K), broken aggregate (BA) and adhesion failure (AF) were regarded as responses. Image analysis technique was employed for quantification of failures (including adhesion and cohesion failures) on the fractured surface of mixtures. The susceptibility of mixtures' fracture properties to temperatures was also determined in terms of KTS. The responses were analysed using RSM. The results showed that ageing temperature and ageing duration were the dominating ageing factors affect responses. Ageing increment resulted in higher K and BA while exhibited contradictory effects on AF. Test temperature increment reduced the fracture toughness. The KTS was increased at higher temperatures. Lastly, RSM and image analysis technique exhibited great reliability and capability to study the behaviour of the responses exposed to various ageing conditions. [ABSTRACT FROM AUTHOR]

This study investigated the effect of short-term and long-term ageing on the dynamic modulus of foamed warm mix asphalt (WMA) produced by water injection and traditional hot mix asphalt (HMA). Four asphalt binders (PG 64-22, PG 64-28, PG 70-22 and PG 76-22) and one aggregate (limestone NMAS 12.5 mm) were used in the preparation of the laboratory-produced asphalt mixtures. The short-term and long-term ageing of the asphalt mixtures were simulated using AASHTO R 30. The experimental test results showed lower dynamic modulus values for foamed WMA than those obtained for traditional HMA for both short-term and long-term oven-aged specimens. By comparing the dynamic modulus values of the short-term and long-term oven-aged specimens, it was observed that some mixtures, such as those prepared using PG 64-22, had a smaller increase in dynamic modulus for foamed WMA mixtures than traditional HMA mixtures, while a comparable increase in dynamic modulus for both foamed WMA and HMA was observed for other mixtures, such as those prepared using PG 70-22 and PG 76-22. This suggests that the binder type plays a significant role in determining the ageing characteristics of foamed WMA and HMA mixtures. [ABSTRACT FROM AUTHOR]