Compressive Strength of Corn Stalk Ash as Supplementary Cementitious Material in Mortar

The availability of agricultural wastes, especially corn stalks, offers sustainability benefits in reducing the demand for cement production. Altering this waste into ash becomes significant for cementitious material. Thus, the study utilized corn stalk ash (CSA) as a partially cementitious material in producing cement mortar. This experimental study aims to understand the compressive strength of CSA mortar samples and their characteristics, such as absorption and their correlation. Compressive strength and absorption tests were performed in the laboratory to specimen control (M0) and partial replacement of CSA to Portland Composite Cement (PCC) at different portions of 5%, 10%, and 15% or M5, M10, and M15 at 7d, 28d, and 56d. Before mixing, we measured cement and fine aggregate (sand) properties with a water-to-binder ratio (w/b) of 0.48, based on the standard reference in producing an ordinary mix mortar. The CSA used came from an agricultural field around central Java known to have good pozzolanic reactivity. Then, the average compressive strength and weight change were measured. The results indicate that the optimum increase in compressive strength of mortar was achieved with a 10 percent CSA replacement, which exhibited 96% enhancement from 7 to 28 days compared to other mixes. In addition, the weight changes of the mortar mix have shown an increase with the CSA replacement through 10 percent at 28 days of curing. Nevertheless, the relation between compressive strength and weight change of specimens shows a low linear relationship.