Study On Mechanical Property And Permeability Of Chloride-corroded Concrete

Reinforced concrete structures are common structures in civil engineering,which are widely used in all kinds of cross-sea bridges,civil construction as well as transportation and port engineering.However,concrete construction under chlorine salt environment is easy to be corroded,which can lead to construction property degradation.What’s more,the degradation will influence the safety,reliability and application of concrete,which will shorten service life and cause huge economic loss.To some extent,some severe durability failures and maintenances are impossible to solve.In daily life,people tend to estimate service life based on ideal structural property.While the truth is the service life will be effected by all kinds of factors.We can come to an end that it is necessary to improve property and performance of reinforced concrete structure under chlorine salt environment.Relied on National Science Foundation of China Project "Service performance evolution rule and difference on reinforced concrete columns of corrosions-resistant bar and conventional carbon bar under marine environment"(No.51678513),this paper aims to research on compressive strength of damaged concrete beam,stress-strain curve,elastic modulus,Poisson’s ratio as well as permeability regularity of chloride ion.The main research work is as follows:This paper carried out cube compressive strength test on rust-corroded concrete and chloride-corroded concrete.Through application of constant current-dry cycle to accelerate rust corrosion on rust-corroded concrete beam.We aim to analyze the relationship between compressive strength of rust-corroded concrete cube and the corrosion rate,mean crack width as well as maximum crack width.The result shows the compressive strength of rust-corroded concrete will decrease with the increase of steel rust rate.Through dry cycle test on chloride-corroded concrete,we analyze the relationship between compressive strength and time of dry cycle.The results show compressive strength of chloride-corroded concrete,will tend to rise first and then down with the increase of time of dry cycle.Through stress-strain curve and modulus of elasticity test,elastic modulus test,poisson’s ratio test on rust-corroded concrete prism,we aim to explore the change rule between modulus of elasticity and rust time,the relationship among the compressive strength of rust-corroded concrete prism,Poisson’s ratio and mean crack width.With the research on the distribution and development of rust expansion crack,the result shows that tilt rate of stress-strain curve will decline gradually with the increase of rust rate during the stress-strain curve rising;the tilt rate of normal concrete decline dramatically while the tilt rate of rust concrete is stable at the end of decline stage.The modulus of elasticity on rust-corroded concrete prism will generally tend to go down.What’s more,the poisson’s ratio of rust-corroded concrete will decrease gradually with the increase of mean crack width.Rust expansion crack with 3%rust rate will lead to one-side damage of protective layer,while rust expansion crack with 6%-9%rust rate will lead to double-side damage of protective layer.Through the method of dry cycle,we aim to explore the effects of one-side corrosion and double-side corrosion on chlorine ion penetration.The result shows the value of free chlorine ion will decrease with the increase of corrosion depth both in one-side corrosion and double-side corrosion test.Furthermore,in same corrosion depth,chlorine ion value in double-side corrosion test is 1.21 times as many as that in one-side corrosion test.