Shear Strength Characteristics of Recycled Glass

A comparison of the California bearing ratio (CBR) for recycled glass (RG) with other recycled materials and a basaltic virgin aggregate, all having similar gradations, revealed that the CBR of RG is superior to that of recycled asphalt pavement but less than that of recycled concrete and virgin aggregate. Direct shear tests were then run on the as-received gradation to derive strength parameters for RG prepared at very high and very low relative densities. For dense RG, the peak failure envelope was nonlinear with secant friction angles varying from 50 degrees to 61 degrees. For loose RG, the peak and critical state failure envelopes were linear with friction angles of 41 degrees and 38 degrees, respectively. Bolton's postulate that the peak friction angle is approximately equal to the critical friction angle plus 0.8 times the maximum angle of dilation works well for the RG tested in direct shear. A friction angle of 38 degrees at critical state is significant, implying that RG has the potential to be used in even more foundation and ground improvement applications that are so often associated with transportation infrastructure construction. With increased use of recycled materials, civil engineers can help comply with the demand for sustainable development, a major theme in society today.