Study On Strength And Volume Expansion Of Steel Slag Cementitious Composites With Inorganic Fibers

China is a large country with steel production, the crude steel output reached7.79million tons in2013. As a important by-product of iron and steel smelting, steel slag’s output is10%～15%of crude steel’s. Utilization status of steel slag is high output, low utilization rate in China. There are some self-shortages restrict the application and popularization of steel slag, for example, volume expansion and poor cementitious activity. the amount of China’s steel slag accumulation reached12.8million tons at present, a large number of land resources occupied, environment polluted, so, improving the utilization rate of steel slag to be solved immediately.In order to solve the volume expansion of steel slag, improve the utilization rate, this paper studies the effects of glass fiber or mineral fiber on strength and volume expansion of steel slag cementitious composites, draws the following4conclusions.1. According to specific surface area-grinding time curve graph, the suitable grinding time is180min. combination of substitutive method and standard method be selected for measurement of water requirement of normal consistency of cementitious materials. 2. Strength of mortar specimens decreases with steel slag content increasing. Flexual strength decreases with fiber content increasing. When the content of fiber is0.5%, a large number of random distribute fibers reinforce the mortar specimens, early flexual strength rised. With the contents of glass fiber and mineral fiber both for0.5%, the3d flexual strength of mortar specimens increased by8.0%and3.17%, respectively, than the content is0.4%. Compressive strength decreases with fiber content increasing. The3d and28d compressive strength increased by5.2%,2.36%while the content of glass fiber is0.1%, which decreased by11.6%,3.5%while the content is0.1%. The effects of mineral fiber are approximately same as glass fiber. The average expansion rate of autoclave specimens with fibers is lower than the autoclave specimens with non fiber. As the contents of fibers kept increasing, the expansion rates of autoclave specimens droped. The expansion rates of autoclave specimens with mixed fibers (3mm and12mm glass fiber) is lower than the single fibers (3mm,6mm or12mm glass fiber).3. As for steel slag-blast furnace fiber-cement clinker cementitious composites, as the glass fiber content kept increasing, strength of mortar specimens in each hydration curing age increased then droped.28d curing age strength of mortar specimens with0.3%wt glass fiber is highest. The content of mineral fiber had little effect on flexual strength of mortar specimens at early curing ages, late compressive strength of mortar decreased with mineral fiber content increasing, and late flexual strength decreased first then increased with mineral fiber content increasing. The expansion rate decreased by26.60%while adding0.3%glass fiber, the expansion rate decreased by29.36%while adding0.3%basalt fiber.4. In early curing age, there are a few C-S-H gels on the surface of fibers, poor interfial adhersion between fibers and paste leads to low early strength of mortar specimens. With hydrating, C-S-H gels and Ca(OH)2crystals produced on the surface of fibers, that improved the interfial adhersion between fibers and paste and the strength of mortar specimens. C3A reacts with Ca(OH)2to form lots of lamellar structure AFms, that compact the structure of mortar. The chemical composition of mineral fiber is similar with mortar’s and therefore interfial adhersion of mineral fiber and paste is better than glass fiber and paste, but the distribution of glass fiber is better.