A new approach for improving the properties of tailings sand autoclaved aerated concrete - From a mineralogical perspective

This study proposed a new method to improve the performance of tailings sand autoclaved aerated concrete (SAAC). Firstly, high silicon iron tailings from the Anqian area and low silicon molybdenum tailings from the Weinan area were selected, and the mineral composition of these two tailings was analyzed. Then, the single mineral in the two tailings were used instead of siliceous raw materials to prepare mineral autoclaved concrete (MAC). The autoclaved reactivities of these minerals were analyzed through compressive strength, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG-DTG), and scanning electron microscopy (SEM), and which minerals were beneficial for the preparation of SAAC were determined. On this basis, magnetic separation and gravity-magnetic separation processes were used to pretreat Anqian iron tailings and Weinan molybdenum tailings, respectively. Finally, the effectiveness of this method was verified by preparing SAAC made with tailings before and after pretreated. The tested results showed that the autoclaved activities of siliceous minerals were in the following order: quartz hornblende, feldspar, chlorite, while the montmorillonite and biotite, and the metal mine (hematite and pyrite) did not have autoclaved re- activities. The main crystalline phase of hydration products in MAC made with single mineral without autoclaved reactivities were C-S-H, Ca(OH)2, 2 , CaCO3, 3 , and hibschite, and that in MAC made with quartz, hornblende, feldspar, and chlorite were C-S-H, tobermorite, Ca(OH)2, 2 , CaCO3, 3 , and hibschite (except quartz). After 1.3 T strong magnetic separation treatment, the content of Fe2O3 2 O 3 in iron tailings decreased from 11.11 % to 4.16 %, and the compressive strength of SAAC made with iron tailings with magnetic separation pretreated increased by 11.43 % comparted to that of SAAC made with original iron tailings. After gravity separation and 1.1 T strong magnetic separation pretreated, the content of SiO2 2 in molybdenum tailings increased from 63.97 % to 84.03 %, and the mineral content of biotite decreased from 40.5 % to 11.2 %. The compressive strength of SAAC made with molybdenum tailings with gravity-magnetic separation pretreated increased by 24.09 % comparted to that of SAAC made with original molybdenum tailings.