Strength and deformation characteristics of recycled concrete aggregate as a backfill material

A series of consolidated drained triaxial compression tests were performed on recycled concrete aggregates to investigate the feasibility of their use as a backfill material for geotechnical engineering structures requiring a high stability while allowing a limited amount of deformation, such as embankments and conventional type and geosynthetic-reinforced soil retaining walls supporting highway and railway. The experimental results showed the following. The compressive strength q(max) when well compacted at water content in the vicinity of the optimum water content w(opt) is similar to that of typical well graded gravelly soil that is categorized as the highest class backfill material. When well compacted at the same energy level, the peak strength and pre-peak stiffness of recycled concrete aggregate is insensitive to changes in the moulding water content relative to w(opt). When well compacted around w(opt) the effect of confining pressure on qmax is similar to the one of typical well graded gravelly soil, while confined saturation does not have any detrimental effects on the q(max) and pre-peak stiffness. With a decrease in the compacted dry density from the maximum dry density at fixed water content around w(opt) for a given compaction energy level, the q(max) and pre-peak stiffness decreases at a very high rate. The viscous property of the recycled concrete aggregate is similar to the one of ordinary type backfill materials. When well compacted around w(opt) residual strains by sustained and cyclic loading are not significant.