Development of Equivalent Stress Block Parameters for Fly-Ash-Based Geopolymer Concrete

Abstract

Advances in research and development of geopolymer concrete have made it a feasible alternative material for civil and infrastructural applications. However, currently, there is a gap in design methodology due to lack of knowledge on geopolymer concrete, which has been a significant barrier for engineers and designers. The current research addresses this gap, modeling an equivalent stress block of fly-ash-based geopolymer concrete, to enable the design of sections. It was found that the design parameters based on the standard codes are not well suited for the fly-ash-based geopolymer concrete structures. In addition, the elastic modulus model obtained from Ordinary Portland Cement concrete is inappropriate for fly-ash-based geopolymer. Therefore, in this study, the stress–strain relation, an elastic modulus model and equivalent stress block design parameters were obtained from experimental results, also using prior published data, for flexural strength predictions of fly-ash-based geopolymer concrete members. A simplified stress–strain relationship based on Thorenfeldt’s model, as well as the stress block design equations, was fit to test data. The results showed that the simplified stress–strain model is reasonably accurate. The prediction of flexural moment capacity based on the proposed design parameters correlated well with experimental test data. It was found that the nominal moment capacity using standard code design parameters was about 1.43 times higher than with the proposed design parameters.