Influence of Creep and Sand Type on the Compression Behavior of Sand-Rubber Composites

Even though the mechanical behavior of granular soil–rubber mixtures has attracted significant attention and promising applications in geotechnical engineering, less attention has been paid to the influence of creep and long–term response of these composites. The present study examined the compression behavior of two types of sands mixed with recycled granulated rubber with emphasis on the influence of rubber percentage and sand grain type, providing in this way some new insights with emphasis on creep influences. One natural material is composed of Leighton Buzzard quartz sand of noncrushable grains, and the second material is composed of completely decomposed granite of crushable grains (note that the terms crushable and noncrushable refer to the range of maximum overburden pressures applied in the study that ranged from 0.3 to 6.7 MPa). The influence of creep on the compression behavior of the samples was associated with the location (or not) of the pure sand and their mixtures on the normal compression line (NCL) when creep deformations were evaluated. In specific, the rate of creep deformation was found to be independent of the stress level as long as the sample had reached its NCL during compression. Even though for LBS–rubber, there was a clear decrease of the stiffness of the mixtures expressed with the constrained modulus, this was not the case for the CDG–rubber mixtures, and within the scatter of the data, the ratio of creep index to compression index fell in a relatively narrow range (0.005–0.05), suggesting that the creep deformations could be predicted based on conventional oedometer tests with short–term measurements of the applied normal stress.