Influence of Agricultural Waste Ash as Pozzolana on the Physical Properties and Compressive Strength of Cement Mortar

The increasing demand in cement has inspired researchers in both developed and developing countries around the world to explore and consider alternative materials as partial replacement of cement both in concrete and in mortar. In this study, the influence of agricultural waste, particularly corn cob ash, (CCA) as pozzolanic material or supplementary cementitious material (SCM) on the physical properties and compressive strength of cement mortar was investigated. CCA was used as partial replacement of cement ranging from 0% to 20% by weight at water-cementitious ratio of 0.6 and mix proportion of 1 cementitious: 3 fillers. The physical properties evaluated for the mortar paste were setting time and consistency; and compressive strength of hardened mortar cube. The chemical analysis of CCA was conducted, and results indicated that the CCA used in this study is classified as Class C pozzolana with combined SiO₂ + Al₂O₃ + Fe₂O₃ of 55.86%. The addition of CCA increases the initial and final setting time. The study also revealed that the addition of CCA in the mortar mix reduces the plasticity or fluidity of the paste. Further, the result indicated that the compressive strength of mortars with CCA decreased as the amount of CCA replacements increased in the mixture. The mortar pastes with varying amount of cement replacements, however, are superior for use as mortar for masonry construction.