Use of Calcined Clay as Natural Pozzolana to Partially Replace Portland Cement and Its Environmental Impacts

Today's building materials use more and more different natural and industrial pozzolanic and cementitious materials. Supplementary cementitious materials (SCMs) are known to give concrete and mortar an advantage over other binder types and building materials in terms of mechanical and durability performance, sustainability, and reduced environmental charges. The development of naturally occurring pozzolans or calcined clays that are produced locally is essential for increasing the sustainability of the construction sector. Raw soil locally extracted from a city named Nizwa (NZS) in Oman was subjected to grinding, calcination, and characterization and then used at 10, 25, 35, and 50% as partial substitution of general use ordinary Portland cement (OPC) in mortar mixes. The compressive strength and durability of the blend mortar were evaluated. The results showed a minor decrease in the flow of the modified mortar mixes. The density of the hardened mortar was not significantly affected by the NZS substitution, but at certain substitution levels, the strength at 1 and 28 days had somewhat decreased. In the meantime, the porosity and absorption have reduced by around 1%.