Experimental investigation of the compressive and tensile strengths of geopolymer mortar: The effect of sand/fly ash (S/FA) ratio

This paper presents an investigation on the compressive and tensile properties of geopolymer mortar. Particularly the effect of sand/fly ash (S/FA) ratio on its strengths is highlighted. Compressive and splitting tensile tests on a 50 mm × 100 mm cylindrical specimen with S/FA ratio between 0 and 6 have been carried out. Experimental results showed that the failure of geopolymer specimen tested was dominated by splitting, shearing and central cracking. Compressive and tensile strengths of up to 12.4 MPa and 2.1 MPa; respectively, can be obtained from the given mixture. It was found that both strengths are decreasing with increasing S/FA ratio more pronouncedly at a ratio between 0 and 1.5. Moreover, the strength increasing trend can be considered as S/FA independent.