A novel process for synthesis of tobermorite fiber from high-alumina fly ash

Abstract

A new two-step process was developed for the synthesis of tobermorite fiber from high alumina fly ash. The results reveal that high alumina extraction efficiency from the fly ash can be achieved in the first step and tobermorite fiber with excellent properties can be produced from the dealumination slag in the second step. FETEM images show that typical single crystal fibers with a length of 5–10 μm and a length-to-diameter ratio of 50–100 have been synthesized successfully. The strength tests after compression molding demonstrate that the compressive and flexural strengths of the products are greater than 0.34 MPa and 0.85 MPa, respectively, with a low bulk density of 218 kg/m3 and a thermal conductivity of 0.059 W/(m·k). It fully complies with China's national standards for calcium silicate insulation materials. Therefore, the fibers production is very promising to be used in the building external wall thermal insulation application.