Preparation and Characterization of Calcium Silicate Slag Based Lightweight Wall Materials

Abstract

Potassium feldspar (KAlSi3O8) can be used to extract potassium to solve the shortage of water soluble potash resources in China, but it will produce large amount of calcium silicate slag. Resource recycling from calcium silicate slag can be realized by synthesising wall materials. In this research， calcium silicate slag based lightweight wall materials have been successfully prepared by calcium silicate hydrates (CSH), lime and fly ash through autoklave process. Furthermore, the wall materials are charactered by strength determination, X-ray diffraction (XRD) analysis, and Scanning electron microscopy (SEM) analysis. The results show that the compressive strength is mainly influenced by the lime/fly ash mass ratio (L/F), CSH content and water/solid ratio (W/S). The compressive strength of 21.1-23.9 MPa and density of 0.87-0.91 g/cm3 are achieved respectively with the L/F value of 0.82-1.00, CSH content of 70 % and W/S of 0.9. The main hydrate product of wall materials is 11Å tobermorite [Ca5(OH)2Si6O16•4H2O], which is partly formed from the phase transformation of CSH, and partly produced by the reaction among raw materials during the process of autoclaving. The tobermorite is easy formed at low L/F value and it has a contribution to the low density for its flake-like structure that make the materials porous.