Experimental Research Of Low-Carbon Concrete By Double Mixing Steel Slag

In China, the annual emissions of steel slag waste by iron and steel industry isabout15%～20％of steel production, a series of environmental problems has beeninitiated because of a large number of abandoned steel slag, seriously affected theenvironment and residents normal life; unused space being stacked by steel slag, alsobring certain economic burden and resource loss. As the composite development trendand high utilization rate of industrial waste in concrete industry, the large mixingamount, high utilization rate and diverse recycling way of steel slag remains to befurther research.The research purpose of this project is high value-added utilization of steel slag,granular steel slag by coarse crushing and screening as coarse aggregate, steel slagpowder by fine grinding to certain fineness as admixture, replacing natural gravelaggregate and cement respectively for preparation of concrete double mixing steelslag.Concrete volume stability as test prerequisite, the macro mechanical properties,durabilities and long-term performance of double mixing steel slag aggregate/steelslag powder concrete has been studied; the micro-structure of differentaggragate-cement interface and compound cementitious system was analyzed bymicroscopic test methods, such as SEM, XRD and microhardness test, etc.Experimental result shows that: on the basis of25%steel slag aggregate insteadof natural gravel,30%/40%steel slag powder instead of cement as admixture, thevolume stability of concrete by double mixing steel slag qualified, the mechanicalproperty and durability satisfied the experimental design; thereinto, compressionresistance, carbonation resistance, sulfate resistance of concrete which double mixing25%steel slag aggregate and30%steel slag, can be improved significantly; it is worth focusing on that, on the basis of concrete double mixing25%steel slagaggregate and30%steel slag powder, compound mixing20%blast furnace slagpowder, mechanical and durable properties both showed up the best performance, thereplacement of steel slag aggregate and waste slag reached to25%,50%respectively,achieved the research object of high volume steel slag concrete.The micro-structure test of seel slag concrete shows that: the interface of steelslag aggregate-cement appears structural integrity, microhardness value is higher thangravel-cement interface; compound cementitious system has higher and moresufficient extent of hydration, the micro-structure characteristics provided a theorybasis for excellent macro performance of double mixing steel slag concrete.