Effect of Extra Water on the Compressive Strength of Periwinkle Shell Ash Based Geopolymer Mortar.

Abstract

The effect of extra-water on geopolymer mortar samples under compressive loading was investigated in this study. The PSA processed at 800^oC was used as the source material. The mortar samples were made with moulds of 70.6mm² cube according to the British standard. The samples were tested after 7, 14, and 28 days of curing. River sand was used as fine aggregates. Mix 1 and 2 were prepared with W/B ratios of 0.18 and 0.13 respectively. The river sand used for the study had specific gravity of 2.60 and fineness modulus of 4.98. The 28-day compressive strengths for Mix 1 (19.9, 18.1, 17.4, 16.5, 14.2, and 8.2 N/mm²) and Mix 2 (25.0, 22.9, 18.3, 17.5, 16.2 and 15.2 N/mm²) showed, Mix 2 performed better than the Mix 2 with less extra-water content.  The paired t-test used in the study showed that, there was significant improvement on the strength of the mortar samples when the W/B ratio was reduced from 0.18 to 0.13 since the calculated value of t = 3.112 > tabulated t at 5 df = 2.015.