Mechanical And Functional Performances Of Super-fine Stainless Wire Reinforced Reactive Powder Concrete

Super-fine stainless wire(SSW)is produced through drawing.It not only has the mechanical property of primary steel fiber but also can overcome the interface bonding problem between concrete and organic fiber.Its diameter is micorscale,thus leading to high aspect ratio.Therefore,it can form extensive reinforcing,toughening and conductive network at lower content level.Thus,SSW reinforced RPC has multifunctional performances such as high strength,high toughness,electrical conductivity and electromagnetic properites,presenting wide application prospect in civil engineering.The strength,constitutive relation,toughness and multifunctional performances of SSW reinforced RPC were studied in this dissertation.The main contents and conclusions are as follows:1)The room temperature curing strength and constitutive relation of SSW reinforced RPC were studied.The uniaxial compression constitutive model was established and the reinforcing mechanism of SSW was discussed.Experimental results showed that the reinforcing effect of SSW with diameter of 20?m is better than that of SSW with diameter of 8?m.The increased ratio of elasticity modulus and possion ratio can reach up to 25.1%and 41.2%,respectivly.The linear coefficient between prismatic and cubic compressive strength is 0.99.Meanwhile,the linear slope between splitting tensile strength and compressive strength,flexural strength is 1/13-1/17 and 0.77,respectively.The peak strain of RPC under different load types increases significantly due to the addition SSW.The uniaxial compression constitutive model can well describe the damage delaying effect of SSW on the basis of continuum damage mechanic theory.The strength of composites can be expressed as the quadratic polynomial of SSW factor.The disordered distribution SSW forms three-dimensional "woven network" in RPC,and plays as the crack resistance zone in the form of "inter-anchored" and "rope woven" until they are sapped,rotated and stripped.The Ca(OH)2 orientation index is decreased because of the addition SSW.2)The accelerated curing strength and constitutive relation of SSW reinforced RPC were investigated.The uniaxial compression constitutive model containing environment factor was built up.The accelerated curing reinforcing mechanism of SSW was studied.Experimental results showed that the strength and deformation of SSW reinforced RPC at different curing age further increase due to the accelerated curing.The elasticity modulus,passion ratio and bulk modulus are increased by 87.4%,114.8%and 165.6%respectively.The linear coefficient between prismatic and cubic compressive strength is 0.97.The linear slope between splitting tensile strength and compressive strength,flexural strength is 1/11-1/14 and 0.80,respectivly.The limit damage of SSW reinforced RPC calculated by the amendment uniaxial compression constitutive model containing environment factor is 0.26.Because of accelerated curing,the "inter-anchored" effect is more significantly,and the effect of SSW on RPC hydration extent is weakened.Meanwhile,the Ca(OH)2 orientation index decrease continuously.3)The compressive toughness,flexural toughness,fracture toughness and impact toughness of SSW reinforced RPC were studied.The crack resistance mechanism was discussed.The flexural toughening model and the dynamic impact constitutive model were built up.Experimental results showed that the toughening effect of SSW with diameter of 20?m is better than that of SSW with diameter of 8?m and there is multiple cracking trendency when the flexural tensile failure happens.The SSW is more easily to be snapped after the accelerated curing.Notched beam equivalent flexural strength is increased by 80%when the SSW content increases.The plate bending toughness is increased by 201.9%.The theory value calculated with flexural toughening model based on composite material considering boundary wall effect is well consistent with the experimental value.The initial fracture toughness and unstable fracture toughness are increased by 185.2%and 179.2%respectively on the basis of double K fracture model.The increase ratio of fracture energy can reach up to 1017.1%.Meanwhile,notched beam four point shear fracture toughness is increased by 137.3%and the failure state is mainly I-II compound crack.The rate-hardening effect of RPC is weakened by the inclusion of SSW.The dynamic impact constitutive model based on viscoelastic plastic theory can describe the dynamic impact stress-strain relationship of SSW reinforced RPC well when the strain rate is larger than 300/s.4)The electrical property and conductive mechanism of SSW reinforced RPC were studied.Meanwhile,the sensing property of SSW reinforced RPC under cyclic load and failure load was analyzed.The functional properties such as damping capacity,electromagnetic wave shielding and absorbing performance,thermal and wear-resistance property were also investigated.Experimental results showed that the conductive percolation phenomenon happens when the SSW with diameter of 8?m and 20?m is 1.5%and 0.5%,respectively.The direct current and alternating current electrical resistivity can be decreased by 6-7 order of magnitudes,and the capacitance can be increased by 5-6 order of magnitudes because of the addition SSW.The conductive passage of SSW reinforced RPC mainly depends on overlap of SSW and pore solution.The strain sensitivity of composites under cyclic compressive loading is up to 41.86.Meanwhile,the strain sensitivity under prismatic compressive loading,flexural tensile loading and splitting tensile loading can reach up to 143.07,23.98 and 146.5,respectively.The fractional change in electrical resistivity of SSW reinforced RPC can reflect the stretch process of crack tip under three point flexural fracture loading,and it also can reflect the crack initiation and crack develop speed under four point shear loading.The damping ratio of SSW reinforced RPC is increased by 19.9%.The electromagnetic wave shielding effectiveness is improved by 202.9%,and the peak reflectivity is-36.5dB.The heat conductivity coefficient is increased by 73.8%,and the specific heat capacity falls from 1523.0 J/(kg·K)to 1439.3 J/(kg·K).Mass loss per unit area of SSW reinforced RPC under wear loading is decreased by 51.8%.