Mechanical activation of diabase and its effect on the properties and microstructure of Portland cement

Many volcanic rocks with pozzolanic properties are used as additives in cement production. Although diabase is a volcanic rock, it has not been used as an additive material in cement production until now. In this study, pozzolanic reaction ability, mechanical, hydration and microstructure properties were investigated before and after mechanical activation in order to increase the usability of diabase in cement production. Firstly diabase samples were analyzed for chemical, mineralogical compositions and pozzolanic activity. The diabase was first subjected to dry grinding separately from clinker to increase the amorphous structure by decreasing its crystalline structure and mechanical activation was achieved.The pozzolanic activity of the ground diabase gradually increased depending on the grinding time. The effects of 10%, 30% and 50% addition of natural diabase by weight on the characteristics of cement pastes and cement mortars were researched. Zeolite containing cliptonolite mineral was used as a comparison material with diabase. The Blended cement specimens were tested for particle size, setting time, water demand, soundness, heat of hydration, and compressive strength. The compressive strength proportion of the cement mortar samples containing large quantities of natural diabase were lower than that of the Portland control cement at all tested ages up to 28 days, but it was a higher compressive strength than zeolite blended cements. 10%, 30% and 50% diabase blended cements and 10%, 30% and 50% zeolite blended cements give results above the Cem IV 32.5 R standards. 10%, 30% and 50% diabase blended cements have achieved high early compressive strength than zeolite blended cements. 10%, 30% and 50% diabase blended cements have achieved low final compressive strength than zeolite blended cements. In addition, diabase blended cements may produced at approximately 5% lower cost than zeolite blended cements. All results proved that diabase may be a good alternative to new generation mineral additives in producing cement.