Effects of wollastonite powder on the fresh properties of self-compacted concrete

The use of mineral additions in self-compacting concrete (SCC) as a substitute for Portland cement can not only improve the engineering properties and durability of concrete, but also reduce the environmental impacts of cement production. Nonetheless, due to the high sensitivity of SCC to its constituent materials, an appropriate study on the performance of mineral additions in the production of SCC is absolutely essential. The purpose of this study was to evaluate the fresh properties of SCC containing wollastonite powder in comparison with silica fume and natural zeolite. In this respect, 18 SCC mixtures were designed in four groups with different water/binder ratio and additions contents. Immediately after mixing, the fresh properties of concrete mixtures were evaluated for slump flow, visual stability index, T50, V-funnel time, J-ring and the sieve stability index. The results revealed that although, regardless of the water/binder ratio, the incorporation of wollastonite decreases the slump flow diameter, it can reduce the demand for high-range water reducer admixture usage in comparison with natural zeolite and silica fume. Also, the increase in viscosity and passing ability improvement were observed when wollastonite is used in SCC. Sieve stability index indicated a good segregation resistance in the presence of wollastonite.