Study On Basic Mechanical Properties And Bonding Properties Of Slag-Limestone Concrete

With the popularization and application of "green high performance concrete" and other new types of concrete, mixing slag, limestone powder and other industrial by-product into concrete can meet the requirements of concrete industrial sustainable development. Through a combination of physical experiment and theoretical analysis method, this paper analyses the work performance, mechanical properties, uniaxial compressive stress-strain curve, bonding properties and comparison of fine microstructure and macroscopic properties of sla-limestone concrete, aim at providing theoretical guidance for the application of slag and limestone powder in practical engineering, the main conclusions and results are as follows:(1) There is a large difference and good complementarity between particle size, microstructure and chemical composition of cement, slag and limestone powder and it can be applied in the concrete to improve the basic performance of ordinary concrete. Using 30% slag,30% slag and 20% different fineness(350m2/kg, 450m2/kg and 650m2/kg) limestone powder replace cement equally can improve concrete work performance significantly, and mixing with slag and limestone powder can play a "super stack effect" on improving the work performance of concrete.(2) Slag concrete and slag-limestone concrete cube compressive strength, cube split tensile strength and flexural strength in the early stage are lower than those of ordinary concrete.But the late strength of slag concrete increase rapidly and catch up and exceed the corresponding strength of ordinary concrete, slag-limestone concrete strength is always lower than that of ordinary concrete, its strength increases with the fineness of limestone powder.(3) Different concrete axial compressive strength, peak strength, peak strain and elastic modulus increase with the cube compressive strength. The incorporation of limestone powder can reduce the brittleness and improve the toughness of concrete.(4) The failure mode of different reinforced-concrete bonding specimens are splitting failure, the bond stress-slip curve only rise. Bond stress of free end at the beginning of slip, ultimate bonding strength and the corresponding free end slip increase with the fineness of limestone powder.(5) Under standard curing conditions, the hydration reaction of ordinary concrete is faster than slag concrete and slag-limestone concrete in the early stage, but reaction rate of slag concrete and slag-limestone concrete decrease significantly in the middle and late stage and the concrete strength increases rapidly. Through a series of microstructure analysis(XRD, XRF and SEM) obtained, limestone powder can participate in the hydration reaction, indicating the hydration activity. The changes of fine microstructure slag-limestone concrete and the results of the macroscopic properties can verify each other.