Preparation of Autoclaved Bricks from Residue after Vanadium Extraction in Panzhihua

Autoclaved bricks were prepared from residue after vanadium extraction in Panzhihua,lime and sand by compaction moulding-autoclaving maintenance method,and the effects of rise and fall speeds of pressure,steam pressure and curing time on the compressive strength of the samples were studied.The compositions and microstructure of samples were analyzed,and the comprehensive performances and radioactivity were tested.The results show that the compressive strength of the samples increases first and then decreases with the increase in pressure-increasing speed and steam pressure,and that of the samples can be improved with appropriate decrease in pressure-reducing speed and increase in curing time.When the mass fractions of the residue,lime and sand are respectively 60%,23% and 17%,the rising and falling pressure speed is 0.7 MPa/h,and the steam pressure as well as the curing time is respectively 2 MPa and 7 h,the mechanical properties and radioactivity of the products meet the relevant industry standards respectively.The XRD and SEM analysis results show that after the autoclaved curing,needle-like tobermorite,slab-like hard calcium silicate and amorphous hydrated calcium silicate are formed in the products.The hydrated products interweave with coarse aggregate to form a compact structure,giving the products higher compressive strength and lower radioactivity index.