High-strength lightweight blocks prepared from the by-product of aluminium removed from fly ash

Paper in proceeding, 2014

A large amount of powder by-product is generated when Al2O3 is extracted from fly ash. The purpose of this study is to investigate the properties of the powder and find an effective method to reuse it. XRF, XRD, and SEM were used to analysis its compositions and microstructures. The powder was then compressed at the pressure of from 20 to 100 MPa. Results show that the powder was disordered calcium silicate hydrate with an average Ca/Si molar ratio of 1.08. It becomes hardened blocks by compressing. The bulk density of the hardened blocks is between 500 and 800 kg m-3 corresponding to the pressure of 20 to 60 MPa. Their flexible strength is from 1.60 to 5.35 MPa, and compressive strength from 8.50 to 30.50 MPa. The blocks can be recycled by repeating the procedure of crushing blocks, grinding them into powder, and compressing the powder into hardened blocks. This powder can be sustainably reused to prepare lightweight blocks with high strength.