Study On Basic Mechanical Properties And Bonding Properties Of Limestone-fly Ash-slag Concrete

For mineral,technical and ecological reasons,mineral admixtures have become an important component of concrete.The limestone powder,fly ash,slag and other industrial by-product mixed into concrete,can obtain good economic effect and environmental effect,accord with the requirement of 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 limestonefly ash-slag concrete,aim at providing theoretical guidance for the application of limestone powder,fly ash and slag 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,fly ash,slag and limestone powder and it can be applied in the concrete to improve the basic performance of ordinary concrete.Using 15% fly ash,15% slag and 20% different fineness(350m~2/kg,450m~2/kg and 650m~2/kg)limestone powder replace cement can improve concrete mixture work performance significantly,and mixing with fly ash,slag and limestone powder can play a "super stack effect" on improving the work performance of concrete mixture.(2)Fly ash-slag concrete and limestone powder-fly ash-slag concrete cube compressive strength,cube splitting tensile strength and flexural strength are lower than ordinary concrete.The strength of limestone powder-fly ash-slag concrete increases with the increase of fineness of lime 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 is 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 that of fly ash-slag concrete and limestone-fly ash-slag concrete in the early stage,but reaction rate of fly ash-slag concrete and limestone-fly ash-slag 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 activity is low.The changes of fine microstructure limestone-fly ash-slag concrete and the results of the macroscopic properties can verify each other.