Synthesis and characterisation of asbestos-free calcium silicate–based thermal insulating material using novel fly ash-based binder

Calcium silicate–based materials have been a long-time favourite in thermal insulation applications. This work emphasises synthesising calcium silicate–based thermal insulating material via solid-state reaction using silica, calcium carbonate and fly ash as binding material. The calcium silicate formulations were mixed into a ratio of 1:1:1 (CaO:SiO₂:FA) and sintered at temperatures 800–1100°C for 2 h. The developed tailored powder and the sample with calcium silicate formulations were characterised by X-ray diffraction, IR, thermagravimetric analysis, scanning electron microscopy (SEM)-EDS and thermophysical properties (thermal diffusivity, heat capacity per unit volume and thermal conductivity). The synthesised samples are composed mainly of calcium silicate phases, that is, wollastonite with minor larnite and rankinite. The microstructure was evaluated by SEM. It was found that the developed calcium silicate material reached low thermal conductivity values, that is, 0.29 and 0.42 W/mK (for 2P1000 and 2P1100, respectively). The thermal constant analysis of the material shows the stability of the material at high temperatures. Thus, the present results suggest that in-situ calcium silicate–based material prepared is a good thermal insulation ceramic material.