Experimental modelling of chemically graded geopolymer under flexure: load application perpendicular to the graded region

Abstract

The fracture stress, strain pattern distribution and Young’s modulus of chemically graded geopolymer (GFC) specimens were modelled analytically. The GFC specimens were fabricated via the sequential pouring of two different alkali-activated fly ash mixtures into the moulds. Diffusion of the constituent materials of the mixtures into each other prior to hardening causes functionally graded regions in the specimens. The heat-cured specimens with gradual changes in their chemical composition and mechanical properties were subjected to flexural load perpendicular to the graded direction. The fracture stress and modulus of elasticity of the specimens were determined through the rule of mixtures. The models were evaluated by different proposed strain distribution patterns in the deflected beams. The inverse tangent function was proposed as the best function for strain distribution in the deflected specimens. The best performance model was acquired by using exponential functions to represent variations in both fracture stress and modulus of elasticity. However, all models can predict the flexural strength of functionally graded geopolymers by a reasonable approximation.