Sustainable cement mortar production using rice husk and eggshell powder: a study of strength, electrical resistivity, and microstructure

Abstract In order to preserve the natural fine aggregates and proper waste resources recycling, rice husk and eggshell powders were used as filler materials in production of standard M30 grade mortar. Natural fine aggregate was replaced with rice husk powder (RHP) at 3%, 5%, 7%, 10%, 12%, and 15%, and with eggshell powder (EP) at 3%, 5%, and 7%, both at a constant water-to-cement ratio of 0.40. Compressive strength, split tensile strength, water absorption, pore distribution, and electrical resistivity of the mortar samples were investigated. Also, XRD, SEM, and EDS were performed to observe the samples’ chemical phases and microstructure. The results show that up to 15% RHP reduced the compressive strength by 20–35%, whereas the up to 7% EP obtained a similar (varies by 0–5%) result compared to the control sample at 28 days. Furthermore, the results suggest that sand replacement with RHP and EP had no impact on the water absorption and pore volume of mortars. Also, the samples made with up to 15% RHP and 7% EP improved the resistivity by up to 80% and 15%, respectively, providing better resistance to chloride ion migration. Based on the results, it is recommended to use the RHP and EP up to a level of 5% and 7%, respectively, in sustainable M30 grade mortar production.