Effect of harsh environment on cement mortar containing natural pozzolans

This investigation aims to study the effect of the harsh environment on cement mortar containing pumice powder (natural pozzolana) as a partial substitute for ordinary Portland cement (OPC). The harsh environmental conditions applied in this study consisted of seawater supplemented with 5% of sodium sulfate (Na2SO4). Mortar mixtures were produced by replacing 0%, 5%, 10%, and 20% of the OPC mass with natural pozzolana (NP). Mortar samples were treated under two conditions. First, the mortar samples were immersed in tap water. Second, mortar samples are immersed in harsh environmental conditions. In the harsh environment, mortar samples were subjected to 90 cycles of dry-wet, 48-hour drying, and 48-hour wetting over a period of 360 days. Compressive strength, flexural strength, strength loss, change in length, water absorption, and initial surface absorption tests were performed on specimens aged 7, 28, 90, 180, and 360 days. Besides thermogravimetric and microstructure analysis of cement samples that were conducted at a test age of 180 days. The inclusion of NP as a partial replacement of OPC at a rate of 10% improved the results of compressive and flexural strength and achieved the lowest rates of porosity and water absorption of the mortar samples. The inclusion of NP as a partial replacement for OPC reduced the damage caused by the harsh environment.