Strength characteristics and micro-scale mechanism of high liquid limit clay treated by recycled construction and demolition wastes (CDW) aggregates

Abstract

High liquid limit soil has low strength and poor immersion stability, which may cause engineering problems when used as embankment filling. In this paper, recycled concrete aggregate (RCA) and recycled brick aggregate (RCB) were used to improve the mechanical strength and immersion stability of high liquid limit clay. A series of laboratory tests including compaction tests, unconfined compression strength (UCS) test, direct shear test, California bearing ratio (CBR) test and Scanning electron microscope (SEM) test was carried out to study the evolution of mechanical properties of treated soil. The test results show that the addition of recycled aggregate (RA) would reduce the optimum water content (OWC) and maximum dry density (MDD) of high liquid limit clay. With the increase of the content of RA, the UCS of the treated soil generally increases first and then decreases. The longer the curing age, the greater the UCS. Mixing RA with high liquid limit clay will increase the stability and shear strength of high liquid limit clay. With the increase of RA content, the internal friction angle of the treated soil gradually increases; the cohesion first increases and then decreases. Compared with the untreated high liquid limit clay, the bearing capacity and immersion stability of the treated soil have been significantly treated, and with higher content of RCA, the bearing capacity and immersion stability of the treated soil trend to be stronger. SEM images show that the incorporation of RA can promote the formation of agglomerates to increase the integrity. The results of this experimental study can provide reference value for actual engineering.