Experimental Research On Ceramsite Prepared By Using Steel Slag

Steel slag is an inevitable by-product in steelmaking process. The yield of it increases with the sharp rise of steel production, while the recycling methods and capabilities for it are very limited. Therefore, utilizing the slag effectively and comprehensively is important to promote the development of iron and steel industry in China in a sustainable and efficient way. The concrete used in high-rise building and long-span bridge field was made from the ceramsite which has remarkable economic benefits, having characteristics of lighter weight, higher specific strength and better shock resistance, etc. So fly ash sintering-expanded ceramsite and burn-free ceramsite were prepared by steel slag-based mixtures. This is a new mean for the utilization of steel slag, which raise the technological content and added value of the material and has the dual effect of environment and economy.This article is divided into two parts, preparation of sintering-expanded ceramsite and preparation of burn-free ceramsite.In the first part, sintering-expanded cerimsite was made by using steel slag as raw materials. The effect of steel slag and fly ash mixing amount on ceramsite performance was studied. Expansion mechanism was discussed and the ceramsite was characteried. First, the effect of different formulas on sintering and expansion property and performance of ceramsite were analyzed synthetically. The result shows that with the increasing of steel slag, the sintering temperature has been decreased. However, excessive steel slag will restrict the expansion and reduce the sintering range of cerimisite. By comprehensive consideration, the optimum formation of the ceramisite were fly ash75%wt, steel slag10%wt, clay10%wt, and carbon powder for5%respectively. Second, the optimum sintering processing parameters were defined by the optimization of orthogonalization experiment that is precalcined temperature for600℃, precalcined time for20min, burning temperature for1230℃, burning time for4min.After sintering, there is brown compact coat around the ceramsite section which forms loose honeycomb structure. The surface of ceramsite has obvious glaze luster. Each index of ceramsite meets the high-strength ceramsite’s requirements of GB/T17431.1-1998. By using modern test technique XRD and SEM, most parts of the ceramsite are glassy state of aluminate and silicate which forms loose porous structure. The main crystal phases of ceramsite are quartz, mullite and wollastonite etc. Function of primary chemical contents of steel slag in the burning process and expansion mechanism are also analyzed. The study shows that the contents and mineral composition of steel slag play the vital role on inflating and fluxing of cermsite.In the second part, free-burn ceramsite was made by using steel slag. The effects of admixture and curing regime on ceramsite performance were studied. First, stimulation effect of different activator was investigated, and were chosed the gypsum and water glass as activator in this research. Second, the effect of ratio of fly ash and steel slag on ceramsite performance was studied, and the optimum ratio is3:2. Last, amount of additive was determined preliminarily by single factor experiment, and the optimum amount of additive was obtained. The optimal content of aluminum powder, gypsum and water glass were0.5%wt,5%wt and2%wt respectively. In addition, the curing regime of cerimisite was also studied in this paper. The result shows that both improving curing temperature and curing time have obvious effect on ceramsite strength development. The process of free-burned cerimsite preparation mainly concludes gas-development and hydration-hardening rages. The recombination of steel slag and fly ash can promote the reaction of hydration progress, every component produces C-S-H.Comparison between sintering-expanded cerimsite and burn-free cerimsite made in this work, we can see that the bulk density and1h water absorption of burn-free cerimsite are higher than sintering-expanded cerimsite, but these two kinds of cerimsite have no obvious distinguish at the aspect of cylinder compressive strength. Burn-free cerimsite has superiority in the filed of steel slag utilization.