Evolution of maximum shear modulus and compression index of rigid-soft mixtures under repetitive K0 loading conditions

Abstract

The engineering properties of rigid-soft mixtures (i.e., sand-tire chip mixtures) under static loading conditions have been extensively studied; however, the corresponding properties under repetitive loading have not been adequately examined. This study investigates the evolution of the maximum shear modulus (G(max)) and compression index (C-c) of rigid-soft mixtures subjected to static and repetitive loading up to the number of cycles = 10(4). A floating ring oedometer cell equipped with bender elements and an automatic control system was designed to investigate the impact of the size ratio (SR) and tire chip fraction (TF) on G(max) and C-c during repetitive loading. During the initial static loading, the G(max) of tested mixtures increase with increasing SR or decreasing TF because SR and TF determine the connectivity between rigid sand particles. A huge increase in G(max) of rigid-soft mixtures during the repetitive loadings compared to pure sand and pure tire chip indicates the transition of sand-to-rubber contacts to sand-to-sand contacts caused by the repetitive loadings. The increased rate of coordination number between sand particles caused by repetitive loading is a function of SR and TF, resulting in the highest increase in G(max) caused by repetitive loadings for the mixture with SR = 0.44 at TF = 20%, reflecting an opposite effect of SR on G(max) compared to static loading. In addition, the lower impact of SR on C-c after repetitive loadings was observed.