Preparation,properties And Mechanisms Of Cement-based Composites With Nano-ZrO₂

Nano-ZrO₂?NZ?is a material with high strength and toughness,excellent wearing resistant and good thermo-chemical stability.Reactive powder concrete?RPC?has high strength and durability and compacted microstructures.In this dissertation,NZ is added in RPC to develop composite with enhanced strength and toughness.The effect of NZ content on strength and electrical resistivity of PRC and its mechanisms,the effect of preparation techniques on strength of NZ filled RPC and its mechanisms,and mechanical properties of NZ filled RPC are investigated.he main contents and conclusions are as follows:1 RPC with NZ at levels of 0.0%,0.5%,1.0%,3.0% and 5.0% are fabricated.Their flexural strength,compressive strength,splitting strength,electrical resistivity,microstructure,hydration and phase are investigated.The research results showed that NZ can improve the flexural,compressive and splitting tensile strength of RPC.The 3.0% NZ has the greatest contribution to the growth of strength of RPC at 28 d of curing age.NZ has a certain inhibitory effect on cement hydration.The filling effect of NZ makes matrix denser,which can reduce the calcium hydroxide crystal orientation and improve the microstructure of the matrix.NZ can reduce the electrical resistivity,but NZ filled RPC doesn't have pressure sensitive property under the research content.2 RPC with 3.0% content of NZ are prepared by different preparation techniques.Their flexural strength,compressive strength,splitting tensile strength and microstructure,hydration and phase are tested.The research results showed that NZ added in RPC but not replaced cement,ultrasonic dispersion and curing in saturated lime water are unobvious for enhancing the strength of NZ filled RPC.The strength of NZ filled RPC features obvious increase when the specimens are made with high speed mixing or high temperature water curing,which can accelerate the hydration of cement and reduce the mass and orientation of calcium hydroxide crystals to improve the microstructure of the composites.3 RPC with 3.0% content of NZ specimens cured with 90? water for 48 h are fabricated.The uniaxial compressive stress-strain curves,four-point bending load-deflection curves,three-point bending fracture and four-point shear fracture are tested.The research results showed that the addition of NZ leads to the decrease in elasticity modulus and Poisson 's ratio of RPC.Although brittle failure occurs when NZ filled RPC is under ultimate load,adding NZ can improve the compressive and bending capacity of RPC and the energy absorbed when the specimens are destroyed.NZ can effectively improve the fracture toughness of RPC.