Performance Evaluation of Pozzolanic Cements Versus Ordinary Portland Cement: Mechanical, Durability, and Compositional Insights at the Paste and Mortar Scale

The production of ordinary Portland cement (OPC) is energy-intensive and a major contributor to CO2 emissions and global warming. Moreover, OPC concrete may exhibit limited durability in aggressive environments. This study presents a comparative evaluation of pozzolanic cements and OPC. Three commercially produced cement types in Egypt were investigated: CEM I 42.5N, CEM II/A-P 42.5N, and CEM IV/A 42.5N-SR. An extensive experimental program included standard tests on cement paste and mortar, including consistency, setting times, soundness, flow, drying shrinkage, sulfate resistance, and compressive strength at 2, 28, 90, and 180 days under water, sulfate, and chloride conditions. The heat of hydration and the effect of thermal exposure at 300 °C for 1 and 3 h on compressive strength were also examined. TGA, DSC, XRD, and XRF analyses were performed on the as-received unhydrated cement powders to characterize their initial thermal, mineralogical, and chemical features. The results showed that CEM I developed higher early-age mortar strength, whereas the pozzolanic cements showed favorable later-age strength development, reduced drying shrinkage, lower sulfate expansion, lower heat of hydration, and increased residual strength after thermal exposure. Overall, the study provides a multi-technique material-scale assessment of commercially produced pozzolanic cements and clarifies how their initial composition is reflected in paste and mortar behavior under the adopted laboratory conditions.