Low temperature production of wollastonite from limestone and silica sand through solid-state reaction

Wollastonite was produced using solid-state reaction from limestone and silica sand. Limestone containing a high percentage of CaO (55.10%) and silica sand with 99% SiO2 were used as starting materials. The ratios of limestone/sand used were 1:1, 2:1 and 3:1 with various firing temperatures, namely 1100, 1200, 1300, 1400 and 1450 °C. The raw materials and fired products were characterised for mineral phases, chemical composition of content such as CaO, SiO2 and loss on ignition (LOI), density and microstructure. CaSiO3 with an α-phase was detected at firing temperatures as low as 1300 °C, together with olivine and quartz phases, obtained from a 1:1 ratio. No α-CaSiO3 was detected for 2:1 and 3:1 ratios; only olivine and larnite phases were present. The density of the product was 2.93 g cm−3, which is close to the theoretical value, with a specific surface area of 3.23 m2 g−1. This study shows that the Malaysian limestone and silica sand can produce good properties of wollastonite materials.