Effect Of Difference Curing Modes On Dura Bility Of High Performance Concrete

High performance concrete(HPC)has been widely used at present.Curing is one of the most important procedures in concrete construction practices,especially for HPC.HPC has extreme low water to binder ratio,large amount of active admixture.HPC has been found to be even more sensitive to curing conditions than ordinary concrete,particularly at early ages.However,the evaluation approach of the curing efficiency is seldom at present,so it is difficult to determine the efficiency of HPC cured on site,so the curing in the construction often is neglected,which affects the performance of HPC,especially the durability.Many scholars have made some researches on curing of normal concrete.However,there is few report about the effects of different curing modes on durability of highperformance concrete.The paper mainly analyzed the effects of different curing modes on freezing resistance and reinforcement corrosion resistance of high-performance concrete as well as their effects on internal temperature and humidity of large-volume concrete through manners such as comparative experiments.Five different curing modes were designed,including natural curing,curing with curing agent,curing with thin film,standard curing and curing with straw cover.One hundred and twenty cubic test specimens with dimensions of 100mm×100mm×100mm were designed and poured for testing of compressive strength and splitting strength after freezing and thawing.SEM scanning was used to research internal microscopic structures of high-performance concrete after freezing and thawing cycles.Fifteen prismatic test specimens with dimensions of 100mm×100mm×400mm were used for testing of relative dynamic elasticity modulus after freezing and thawing.Fifteen test specimens with dimensions of 100mm×100mm×370mm were used to test reinforcement corrosion resistance of high-performance concrete under different curing modes.Four cubic test specimens with dimensions of 800mm×800mm×800mm were used to test earlier-stage changes in internal temperature and humidity of large-volume high-performance concrete.The ANSYS finite element software was used for temperature field simulation of large-volume concrete.Research results indicate:1.Different curing modes slightly affected the mass loss rate of high-performance concrete test specimens after freezing and thawing.However,with the increase of freezing and thawing,the decrease rates of compressive strength of test specimens were nearly equal to under different curing modes.2.After freezing and thawing cycles,the internal structures of high-performance concrete with straw cover curing and standard curing were more compact and only a few of cracks were generated,while obvious crack meshes appeared in the internal stractures of high-performance concrete with natural curing.3.Reinforcement corrosion resistance of high-performance concrete under different curing modes is as follows(from high to low): standard curing,curing with straw cover,curing with thin film,curing with curing agent,and natural curing.Therein,reinforcement corrosion resistance of high-performance concrete under curing with thin film and curing with curing agent are similar.4.Maximum temperature differences between inside and outside of large-volume test specimens under curing with thin film and curing with straw cover were 6.8? and 7.6?,respectively.In comparison with natural curing,the maximum humidity difference between inside and outside of largevolume high-performance concrete could be reduced significantly by curing with thin film,curing with curing agent and curing with straw cover.The temperature difference between inside and outside under natural curing was the maximum,the value reached 10.2?,while that under curing with curing agent was the minimum,the value was 5.0?.