Durability studies on concrete containing wollastonite

Depletion of natural resources and emission of carbon dioxide are the major factors associated with cement production. Also, conventional concrete often fails to prevent the ingress of moisture and aggressive ions adequately. The concern for concrete durability surfaced globally by the time the structures built with high grade concretes started yielding to distress. Several materials such as fly ash, metakaolin, silica fume, stone waste, rubber tyre, slag, wollastonite etc. which are either industrial wastes or natural minerals, have been examined to make durable concrete. Among the various admixtures studied in the past, the effect of wollastonite on concrete has not been investigated in detail. Wollastonite is a calcium meta-silicate (CaSiO3) mineral with particles similar to cement particles by size. In the present investigation, eighteen concrete mixes at three w/b ratios (0.45, 0.50 and 0.55) were prepared, by substituting Portland cement with wollastonite at varying replacement levels (0-25%). Substitution of 10-15% cement by wollastonite resulted in improved strength and durability of concrete. SEM and MIP results indicated that substitution of cement by wollastonite upto 15% reduced porosity and densified the concrete microstructure.