Fly ash and limestone in diatomite-blended Portland cement

The aim of the present study was to investigate the use of diatomite, which has limited use in the cement industry due to its porous structure in spite of its high reactive silica content, by modifying its porous structure with fly ash and limestone blend. To this end, physical, chemical, mineralogical and zeta potential (electrokinetic) analyses were performed on raw materials. Hydration progress was followed by using standard cement tests and X-ray, and 28-day microstructures of pastes were determined by scanning electron microscopy. Raw material test results have revealed that the particle structure of the raw materials affects the grindability of composite cements, while the Si-O⁻ content in the zeta potentials makes it negative, and the Ca²⁺ content makes it positive. Standard cement test results indicate that water demand and setting time of pastes were related to diatomite ratio, and fly ash and filler limestone affected the development of strength by their electrokinetic properties.