Research On Mechanical Properties And Sulfate Attack Resistance Of Reactive Powder Concrete

In the process of social and economic development,the construction industry's requirements for concrete materials are also constantly developing.Ultra-high strength concrete has become the main development direction of concrete construction materials.Reactive powder concrete(RPC)is a kind of fiber reinforced concrete material with high strength,high toughness and low permeability.However,the application of RPC in engineering is limited due to high temperature steam curing and high cost.In this paper,the preparation technology of autoclaved RPC is proposed.The static mechanical properties and sulfate resistance of autoclaved RPC are studied.The main research contents and results are as follows:(1)The preparation technology of autoclaved RPC was put forward.Self-leveling autoclaved RPC with three grades of steel fibers,C100,C120 and C140,whose volume ratio is 0,1% and 2%,was prepared by using high-grade cement,superplasticizer and high-strength admixture as raw materials.The results show that the strength and toughness of autoclaved RPC increase with the addition of steel fibers,and the increase of splitting tensile strength and flexural strength is higher than that of compressive strength.From brittleness to toughness.(2)Study on sulfate resistance of autoclaved RPC.The results show that:(1)Steel fibers can affect the sulfate resistance of autoclaved RPC.The sulfate resistance of non-steam-cured RPC can be improved by adding steel fibers in a certain range.The sulfate resistance of non-steam-cured RPC without steel fibers is much lower than that of non-steam-cured RPC with steel fibers,but the sulfate resistance of non-steam-cured RPC blocks with steel fibers volume ratio of 1% and 2% differs slightly.2.The strength grade of concrete can affect the sulfate resistance of non-steam-cured RPC.Corrosion performance.In a certain range,thehigher the strength grade of non-steam-cured RPC,the stronger its sulfate resistance.3.Dry-wet cycle and bending stress can affect the sulfate resistance of non-steam-cured RPC.In sulfate solution,the drying and wetting cycle of non-steam-cured RPC is much more serious than that of long-term immersion,and the index decreases rapidly.The application of bending stress can accelerate the erosion rate of sulfate on non-steam-cured RPC.(3)In order to analyze the influence of sulfate corrosion,wet-dry cycle and bending stress on the durability of autoclaved RPC and predict the effective life of concrete structures,three indexes,namely,relative mass loss,relative dynamic elastic modulus and compressive strength corrosion resistance coefficient,are selected to establish a three-index damage model of concrete which is helpful to life prediction through experimental data.(4)Based on Fick's second law,a free diffusion model of sulfate ion in autoclaved RPC was established.The sulfate diffusion of autoclaved RPC was simulated by finite element software analysis.The simulation results were compared with the measured ones.The simulation results were in good agreement with the experimental results.