Basalt as Pozzolana and Filler in Ordinary Portland Cement

Pozzolana is defined as a siliceous or siliceous and aluminous materials which in itself possess little or no cementing properties, but will in a finally divided form and in the presence of moisture react with Ca(OH)₂ at ordinary temperature to form compound possessing cementious properties. Pozzolanic cement contains Portland cement as one of their main components in addition to natural or industrial by products. These include slag, fly ash, homra, silica fumes, rice husk ash, etc. The aim of the present investigation is to study the effect of fresh basalt on the properties of ordinary Portland cement pastes. The rate of hydration was studied from the determination of free lime, combined water and insoluble residue up to 90 days of hydration. The physico-mechanical properties such as bulk density, apparent porosity and compressive strength of the hardened cement pastes were determined. The results revealed that the water of consistency increases with the basalt content whereas the setting time was slightly elongated. On the other side, the combined water increases with the basalt content and curing time. This is mainly due to the effect of nucleating of basalt as filler. The addition of 20 wt% basalt gives the higher compressive strength of the cement pastes in comparison to OPC and cement pastes containing 5, 10 and 15 wt% basalt at all curing times.