Exploring the Effects of the Substitution of Freshly Mined Sands with Recycled Crushed Glass on the Properties of Concrete

Although many works have reported on the effects of using waste materials on the functional properties of concrete, the results are generally diverse. In this work, the effects of substitution of fresh sands with crushed waste glass (CWG) for a concrete mix design of 32 MPa concrete is explored. The mechanical properties were followed with standardised mechanical tests including compression, indirect tensile, and four-point bend tests. It is shown that the compressive strength of concrete containing 15% of CWG produced the highest compressive strength of 34.54 MPa. The splitting tensile and flexural strengths of the concrete mixtures containing CWG both exhibited a maximum strength of 3.21 and 4.90 MPa, respectively at 15% CWG content. Furthermore, it was found that a maximum of 30% CWG can be substituted without a reduction in the mechanical strength. The loss of strength with higher volume proportion of CWG is attributed to the morphological difference between the riverbed and CWG sand particles. The latter had sharp ends that at a critical content might promote stress concentration. Semiquantitative analysis by energy-dispersive spectroscopy (EDS) in a scanning electron microscope (SEM) suggests the presence of alkaline silica reaction (ASR) gel at the interface of glass particles and the mortar matrix. Further exploration of glass mortar interfaces found evidence of ASR gel-induced cracking in the vicinity of the CWG particles in mortar matrix.