The self-gelation properties of calcined wollastonite powder

Abstract

Wollastonite is treated as a special admixture in cement-based materials due to its fibrous shape. A systematic study on the self-gelation property of wollastonite-water pastes after calcined at 800 °C, 900 °C, 1000 °C and 1100 °C for 2 h was conducted. X-ray Diffraction (XRD), Thermal analysis (TG-DSC), scanning electron microscope (SEM) and Infrared Absorption Spectrum (FTIR) were applied to analyse the composition of calcined wollastonite. XRD was then applied to analyse the change of the hydration product and it was found that diffraction intensity of peaks significantly increased after calcination and the highest peaks were observed at 1100 °C. Based on the self-gelation tests, the XRD analysis indicated that in the later hydration process of pastes, calcined wollastonite powder took part in the hydration reaction resulting in slight drops in the characteristic peak. Meanwhile, the compressive strength of calcined wollastonite at 1100 °C was the highest after 28d curing, which indicated that calcined wollastonite exhibited better gelling behaviour, caused by the decomposition of calcite.