Investigations on Pastes and Mortars of Ordinary Portland Cement Admixed with Wollastonite and Microsilica

Abstract

Wollastonite is abundantly available in Rajasthan, Tamil Nadu, Uttarakhand, and Andhra Pradesh states of the Indian Union as a low-cost material. In this study, investigations were made on pastes and mortars to evaluate its potential as a new material for admixing with ordinary portland cement with or without microsilica. Its physical and chemical properties were analyzed. Wollastonite consists of 45.6% of CaO and 48% of SiO2 , mostly in amorphous form. It has an average specific surface area of 842.7 m2 /kg and retention on 45-micron sieve of 3.20%. When ground to fine powder, it attains an average particle size of 4 microns which is about 4.5 times finer than ordinary portland cement. Scanning electron microscope images show that wollastonite particles were solid, acicular in shape, and have rough surfaces. Several cementitious mix proportions of ordinary portland cement, wollastonite, and microsilica were investigated for normal consistency, initial and final setting time of paste, and compressive str...