Effects of glass fiber on recycled fly ash and basalt powder based geopolymer concrete

Abstract

This experimental study encompasses a comprehensive exploration of multiple parameters aiming to enhance the strength, workability, setting time, and environmental attributes of geopolymer concrete (GPC). A pivotal solution lies in substituting fly ash with waste basalt powder, not only reducing binder costs but also ameliorating the overall ecological footprint. A secondary significant factor entails the integration of trimmed glass fibers. Throughout the experimentation process, the predominant GPC binder and fly ash underwent substitution with basalt powder at the proportions of 25%, 50%, and 75%. The mixtures were augmented with glass fibers of 3 mm, 6 mm, and 12 mm lengths, introduced at the ratios of 0.5%, 1%, 2%, and 3%. Then, the acquired samples were subjected to a 24-h curing regimen in an 85 °C oven. Subsequently, after a 7-day period of exposure to external conditions post-incubation, these samples were tested for both the compressive and flexural strengths. Samples incorporating a basalt powder ratio of 50% exhibited the highest capacities, contrasting with reduced capacities when the basalt powder ratio was elevated to 75%. Conversely, samples utilizing a sodium hydroxide (NaOH) molarity (M) of 12 demonstrated superior performance. Impressively, the compressive strength exceeding 40 MPa was achieved with the amalgamation of M 12 and 50% basalt powder additive. However, the workability experienced a notable reduction at the fiber ratios of 2% and 3%. The molarity concentrations did not impede the slump, workability, or setting time. A consistent setting time of 6 h was attained, and the desired workability was obtained without the need for a superplasticizer. For achieving the optimal triad of the workability, setting time, and strength, while maximizing the environmental advantages of GPC, the recommendation is to incorporate a distinct combination comprising 1–2% glass fibers (with 12 mm length), M 12, and 50% basalt powder into the mixture formulation.