Evaluation of permanent deformation and resilient modulus of pavement base with different gradations and percentages of clay plasticiser

Characteristics of unbound granular pavement materials vary among transportation and road association around the world based on function, environmental conditions, and materials availability. Plasticity index (PI) is one of the most important characteristics of unbound granular pavement courses both in the construction stage and throughout its service life. It indicates the range of moisture contents over which the fines in the pavement material behave plastically. This study investigates the effect of a refined clay plasticiser called Claypro (CP) on the elastic and plastic behaviour of unbound granular base materials at different gradations. This paper aims to find the optimum clay content (CP) that achieves an acceptable PI and maintains high elastic performance and high plastic strain resistance under traffic loading. Elastic and plastic responses of 18 mixtures at three different gradations, representing two types of crushed rock materials namely; Hornfels and Basalt, were evaluated at three different CP contents. Repeated load triaxial (RLT) test was carried out with a high number of cycles to estimate the resilient modulus (M-R) and the permanent deformation of these mixtures. The shakedown concept was also applied to assess the deformation behaviour of the tested engineered mixtures under multi-stage RLT test. Results showed that 1% Claypro (CP) content is considered the optimum for all gradations of both aggregate types considered herein.