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

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 signif-icant 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 degrees 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 ratio of 50% exhibited the highest capacities, contrasting with reduced capacities when the basalt ratio was elevated to 75%. Conversely, samples utilizing a sodium hydroxide (NaOH) molarity (M) of 12 demonstrated su-perior performance. Impressively, the compressive strength exceeding 40 MPa was achieved with the amalgamation of M 12 and 50% basalt 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.