Exemplification of sustainable sodium silicate waste sediments as coarse aggregates in the performance evaluation of geopolymer concrete

Abstract

This investigation presents the experimental studies on mechanical properties of geopolymer concrete (GPC) developed with the addition of sodium silicate waste sediments (SSW) as coarse aggregates. Conventional crushed granite coarse aggregate (CA) was replaced by SSW from the sodium silicate manufacturing plant. The GPC was developed by replacing the natural CA with SSW from 0% − 70% with a trend in exercising circular economy in the concrete. The GPC with 100% CA was used as the control specimen to compare the results of different replacement levels of SSW. A low calcium Fly ash (FA) and Ground granulated blast furnace slag (GGBS) were used as binder materials, along with sodium hydroxide and sodium silicate solutions as activator solutions. The sodium hydroxide of 4 M and sodium hydroxide to sodium silicate ratio of 1:1.5 were used in the development of the mixes. Two types of curing conditions namely, ambient and oven curing were adopted. The M30 grade design mix was used for control and CA replaced specimens. The mechanical properties such as compressive, tensile, and flexural strengths along with the elastic modulus of GPC at the ages of 7-, and 28-day were investigated. Microstructural analysis was conducted to examine the influence of SSW on the strength characteristics of GPC. The analyses were performed to evaluate the energy requirement and CO2 emission of GPC and OPCC (Ordinary Portland Cement Concrete) in the production of 1 m3 concrete based on the previous literature. The significance of the proposed research work emphasizes the utilization of waste SSW as an aggregate material for the development of GPC. Therefore, a sustainable GPC mix can be developed with lower energy requirement and CO2 emission. The results revealed that the specimens with 40% SSW cured at 60 °C produced the targeted strength of 34.6 MPa. Meanwhile, the mixes with 40% − 70% of SSW exhibited superior performance in terms of cost and eco-efficiencies.