Investigation of mechanical performance and voids structure of cement-stabilised macadam under freeze-thaw actions

In cold regions, the mechanical performance of cement-stabilised macadam (CSM) deteriorates significantly due to freeze-thaw (F-T) actions. This paper attempts to investigate the F-T attenuation mechanism of mechanical performance of CSM from the perspective of the evolution of voids structure. To this end, multiple groups performance tests were conducted to study the effect of cement content, freezing temperature, and humidity conditions on the mechanical performance of CSM. Then the size distribution and evolution process of internal voids of CSM after F-T actions were investigated by computed tomography (CT) test. The results indicate that the resilient modulus (RM) and compressive strength (CS) of CSM decrease when F-T cycles increase until 15, and then stabilise gradually with a reduction of less than 5% in the last 5 cycles. It is presumbly attributed to the generation and melt of ice lenses in voids, distorting original matrix of particles. Additionally, increasing cement content can reduce the deterioration of mechanical performance, while increasing moisture content and decreasing freezing temperature promote the deterioration of mechanical performance. The F-T actions cause volume expansion of the larger voids (>100 mm(3)) before 5 cycles and then mainly result in more small voids (<1 mm(3)) during 5 & SIM;15 cycles. There is an apparent linear relationship between average voids ratio and RM and CS for CSM. The correlation coefficient R (2) is higher than 0.92 and 0.73, respectively.