Influence of waste glass and effective microorganism on the mechanical properties of concrete

Abstract

The high demand for concrete in construction leads to the depletion of natural resources such as natural aggregates and clay. The use of waste material in concrete could assist in reducing natural resource depletion and carbon footprints. The use of waste glass in concrete as fine aggregate replacement affects the Interfacial transition zone (ITZ) of glass aggregate concrete and using glass powder as a cement substitute results in low early strength. The purpose of this research was to investigate the properties of concrete with windscreen waste glass as cement and fine aggregates replacement together with effective microorganism (EM) and to establish the appropriate mix proportion that will contribute to enhancing the properties of windscreen glass fine aggregate concrete. Concrete ingredients were altered to contain glass powder (GP) from windscreen glass waste as partial cement replacement (20%) and glass fine aggregate (GFA) as fine aggregate replacement in a proportion of 0-100% (in 20% increments) with EM as water substitute (10%). The laboratory work involves the characterization of waste glass materials and formulation of the size particle of glass aggregate to be used in concrete as fine aggregate replacement. The characterization includes sieve analysis, strength activity index, X-ray Fluorescence (XRF), X-ray diffraction (XRD) and Thermo-gravimetric analysis (TGA). The fresh and hardened properties of glass fine aggregate effective micro-organism concrete (GFAEMC) were investigated. The properties assessed include the workability, compressive strength, splitting tensile strength, flexural strength, modulus of elasticity, and water absorption. Further studies were carried out on the microstructural properties of concrete using scanning electron microscopy (SEM), Energy dispersive x-ray analysis (EDX), X-ray diffraction (XRD), and Thermo-gravimetric analysis (TGA) to ascertain the filling mechanism and bonding effect at the micro-scale level. In addition, three reinforced concrete beams containing waste glass with two containing EM and one without EM, as well as a control concrete beam, were cast and tested to assess the behaviour of reinforced concrete beams under flexure. Based on the findings, the use of waste glass as fine aggregate and cement replacement in concrete improved concrete properties. Adding waste glass with EM in concrete mix improved the compressive strength, flexural strength, splitting tensile strength, and modulus of elasticity (MOE) by 3.37%, 3%, 6%, and 1%, respectively compared to the control, after 28 days. Also, the water absorption of GFAEMC with a 100% GFA as fine aggregate substitute is slightly lower by 2% than that of the control concrete. The microscale analysis showed that GFAEMC samples had a denser microstructure with more CSH gel when compared to the control. In addition, the ultrasonic pulse velocity (UPV) of GFAEMC samples also indicates a denser microstructure. In addition, the ultimate loads of beams glass fine aggregate effective microorganism (BGFAEM), glass powder (BGP20), glass fine aggregate - glass powder effective microorganism (BGFAGPEM) were all higher than BC (control beam). Beam BGFAEM recorded higher stiffness value than beam BC by 18%. The flexural behaviour of reinforced concrete beams with windscreen glass waste and EM is comparable with the control beam. Based on the findings of this study, it can be concluded that incorporating windscreen waste glass as cement and fine aggregates replacement with EM show positive effects and enhanced concrete properties.