Wear Resistance And Chloride Penetration Resistance Of Nano Cement-Base Composites

Reactive powder concrete（RPC）with high strength and high durability possesses denser microstructure than traditional concrete.Nano materials with surface effect,filling effect and nucleation effect can improve the microstructure of concrete.In this paper,nano-silica（NS）,nano-titanium（NT）,nano-zirconia（NZ）and nano-boron nitride（BN）were incorporated into RPC,aiming at developing cementitious composites with better performance.The effect of types and contents of nanofillers and curing methods on wear resistance and chloride penetration resistance of RPC were investigated,and these two performances were characterized by abrasion loss per unite area and chloride transport coefficient,resepectively.The reinforcement mechanisms of these nanofillers on RPC were explored by thermogravimetry（TG）analysis,X-ray powder diffraction（XRD）analysis and scanning electron microscope（SEM）.The main research results are listed as follows:1.NS can significantly improve the wear resistance and chloride penetration resistance of RPC.The optimum contents of NS to acquire the least abrasion loss per unite area（0.38kg/m²）and chloride transport coefficient(0.6×10^-13m²/s)of RPC with standard curing are both 1%,while that of RPC with accelerated curing are both 3%.The highest wear resistance and chloride penetration resistance of RPC can be achieved with the addition of 3%NS with accelerated curing.3%NS can produce more pozzolanic reaction and increase the polymerization degree of silicate inside RPC with accelerated curing.2.The wear resistance and chloride penetration resistance of RPC with NT are both higher than that of control sample.The optimum contents of NT to acquire the least abrasion loss per unite area（0.43kg/m²）and chloride transport coefficient（0m²/s）of RPC with standard curing are both 3%,while that of RPC with accelerated curing are both 1%.Chloride penetration resistance of NT filled RPC with standard curing is higher than that of NT filled RPC with accelerated curing.3.NZ can obviously modify the wear resistance and chloride penetration resistance of RPC.The optimum contents of NZ to acquire the least abrasion loss per unite area（0.42kg/m²）and chloride transport coefficient（0m²/s）of RPC with standard curing are both 1%,while that of RPC with accelerated curing are 3%and 1%.High content is beneficial for enhancing impact of NZ on wear resistance of RPC with accelerated curing.Chloride penetration resistance of NZ filled RPC with standard curing is higher than that of NZ filled RPC with accelerated curing,while wear resistance of NZ filled RPC with accelerated curing is higher than that of NZ filled RPC with standard curing.4.The introduction of BN can obviously enhance the wear resistance and chloride penetration resistance of RPC.Under standard curing,the optimum contents of BN to acquire the least abrasion loss per unite area（0.28kg/m²）and chloride transport coefficient（0m²/s）of RPC are 0.5%and 1.5%,respectively.Under accelerated curing,the optimum contents of BN to acquire the least abrasion loss per unite area（0.32kg/m²）and chloride transport coefficient（0m²/s）of RPC with accelerated curing are 0.5%and 1.0%,respectively.Wear resistance of BN filled RPC with standard curing is higher than that of BN filled RPC with accelerated curing,while chloride penetration resistance of BN filled RPC with accelerated curing is higher than that of BN filled RPC with standard curing.The bridge cracking and pull out effects of BN can effectively delay the generation and development of micro cracks caused by high temperature swelling stress inside RPC matrix with accelerated curing.5.Comparing the effects of NS/NT/NZ/BN on the wear resistance and chloride penetration resistance of RPC,it can be concluded that NZ is the best reinforcing filler with standard curing and NS is the best reinforcing filler with accelerated curing.