Experimental Research On Mechanical Properties And Microstructure Analysis Of Shrinkage-compensating Nano-SiO₂Steel Fiber Reinforced Concrete

As the rapid development of the building industry, transportation industry, marine industry and environmental industry, with the emergence of large-span, light and used in all kinds of harsh conditions, development of high strength, good tensile performance and low permeability of concrete materials is imperative. In this paper, on the basis of shrinkage-compensating concrete, adding steel fiber and Nano-SiO2which made of shrinkage-compensating of Nano-SiO2and steel fiber reinforced concrete, through the basic mechanical performance tests and electron microscope scanning, studies the material compressive strength, tensile strength and microstructure, analyzed the cause of the strength increase.Basic mechanical property test under steel fiber volume ratio and the Nano-SiO2dosage of variables to the orthogonal experiment, a total of16groups of concrete mixture ratio design,192blocks, respectively, test the concrete7d,28d compressive strength, splitting tensile strength.7d compressive strength tests show, Nano-SiO2mixed in shrinkage-compensating of Nano-SiO2and steel fiber reinforced concrete have significantly improved the early compressive strength of materials, with the increase of nano-SiO2dosage, concrete compressive strength increased first and then decreased, at0.6～1.2%dosage of ideal effect, compared with plain concrete compressive strength increased by24.5%;28d compressive strength test showed that the optimal mechanical properties of nano-SiO2content at1.2%higher than plain concrete compressive strength increased by9.4%.Steel fiber mixed in shrinkage-compensating of Nano-SiO2and steel fiber reinforced concrete have significantly improved tensile splitting strength of the material, with the increase of steel fiber,7d and28d roughly the same growth trend splitting tensile strength of steel fiber volume content of0.8to1.2%, the splitting tensile strength increased rapidly, more than1.2%ash after split tensile crack growth leveled off. Steel fiber content is1.2%,7d and28d splitting tensile strength than plain concrete were increased78.6%and78.4%.Microstructure test was carried out on the basis of the basic mechanical properties, material hydration products and interfacial transition zone observed by scanning electron microscope analysis from the point of view of the material microstructure on the macroscopic properties. Test results showed that nano-SiO2shrinkage compensation hydration products of steel fiber concrete orientation is low, dense growth. Promote the incorporation of nano-SiO2cement hydration, reducing porosity, thereby increasing the mechanical strength and durability of concrete can. Between the steel fiber and aggregate micro-crack width comparison test, not mixed with nano-SiO2, the steel fiber and aggregate width of5.311um exists between micro-cracks; mixing nano-SiO2, the micro-cracks are hydrates filling, effectively improve the durability of concrete.