Effect of pre-treatment methods of crumb rubber on strength, permeability and acid attack resistance of rubberised geopolymer concrete

Abstract

Concrete industry has been leading to severe energy consumption and is on a path towards unsustainable development. Geopolymer concrete (GPC) uses alternative binders and can be considered a suitable alternative to conventional concrete. On the other hand, huge waste is produced by industries, posing disposal concerns. Rubber waste is a significant waste that can substitute natural aggregate (NA) in concrete. In this study, the effect of replacement of fine aggregates with crumb rubber (CR) on the properties of GPC was investigated. Natural fine aggregates (NFA) were partially replaced by CR with 10, 20, and 30% in volume. The effect of CR pre-treated using different methods such as water, NaOH, cement paste, and ultrafine slag (UFS) on the strength of GPC was examined. The GPC mixes were prepared using 8 M sodium hydroxide (NaOH) and were heat cured at 60°C. The properties of fresh and hardened GPC including, slump, density, compressive strength, flexural strength, splitting tensile strength, and elastic modulus of GPC were investigated. Furthermore, durability characteristics such as water absorption and acid attack resistance were also experimentally examined since an in-depth investigation of durability of GPC incorporating rubber has not been conducted in the previous studies. The experimental results showed that slump, density, and different strengths decreased with an increase in CR%. In contrast to the other batches, the pre-treatment methods with NaOH and UFS improved the properties of GPC. NaOH treatment enhanced the adhesion between CR and other GPC constituents, resulting in a dense matrix structure formation. The formation of calcium silicate products improved the characteristics of GPC when UFS treated CR was utilised. In general, GPC with CR absorbed more water than the reference GPC (without CR) while lower water absorption was observed when pre-treated CR was utilised. GPC with CR also showed poorer resistance to acid attack (HCl and H2SO4).