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Study On Chloride Erosion Resistance Of Reinforced Recycled Concrete Under Biaxial Load

Posted on:2020-07-28Degree:MasterType:Thesis
Country:ChinaCandidate:Y C C OuFull Text:PDF
GTID:2531306902952699Subject:Structural engineering
Abstract/Summary:PDF Full Text Request
Concrete structure is an important part of all kinds of building structures.The corrosion of reinforcement caused by chloride corrosion is the main reason for premature damage of concrete structure.With the application and development of recycled concrete technology in these years,recycled concrete made by completely or partially replacing natural aggregate has been applied in practical engineering,which will become a development trend in the future.Therefore,the study of chloride ion transport characteristics in recycled concrete is of great significance to the life prediction of practical engineering structures.However,in practical engineering applications,the concrete structure often need to bear the load of different forms,and the existing research on exploring the chlorine salt erosion resistance of recycled concrete often does not take into account different loads influence on chloride ion penetration process,so the related test result and the real working condition still exist certain difference.On the basis of domestic and foreign researches,this paper adopted the environment-friendly carbonization strengthening method to realize the CO2 curing strengthening of recycled aggregate,and studied the transmission and diffusion characteristics of chloride ions in recycled concrete under different stress levels,and explored the microscopic and micro mechanism of load affecting chloride ion diffusion.The main work is as follows:(1)Broken in three different intensity of original concrete,was prepared by three different performance of recycled aggregates,with the method of CO2 curing strengthening,has realized the recycled aggregates carbide strengthened,and the before and after strengthening the basic performance of the relevant test,the test results show that the recycled aggregates carbide improved after its water absorption and crushing index,apparent density,porosity,bulk density all have different degrees of modification.(2)The mixture ratio of recycled concrete was designed,six types of recycled concrete and one kind of raw concrete were poured,the compressive strength test and RCM rapid chloride ion permeation test were carried out,and the influence of carbonization strengthening of recycled aggregate on the macro performance of recycled concrete was studied.The results show that the carbonation of recycled aggregate can improve the chloride penetration resistance and compressive strength of recycled concrete.(3)The influence of single and biaxial compressive loads on the chloride penetration resistance of recycled concrete was studied by using the self-developed chloride dispersion coefficient testing device under load.The results show that the chloride diffusion coefficient of recycled concrete decreases with the increase of the stress level under the single and bidirectional compressive load at low stress level,but increases when the applied stress level exceeds a certain critical stress level.In addition,carbonization of recycled aggregate can reduce the sensitivity of recycled concrete to compressive load.(4)The main strain field nephogram of recycled concrete under uniaxial and biaxial compressive loads was obtained by using DIC non-contact strain testing method,and the mesoscopic mechanism of the influence of compressive load on chloride ion diffusion characteristics was analyzed.Studies have shown that compared with natural aggregate concrete,the strain development of recycled concrete is more rapid at the same stress level,and micro-cracks affecting the diffusion and transmission of chlorine ion will appear earlier,and carbonization strengthening can alleviate this trend to a certain extent.(5)The pore structure of recycled concrete under the continuous action of different stress horizontal compressive load was tested by means of the micro pore structure measurement method of mercury injection meter.It is found that with the increase of stress level,the porosity of mortar decreases first and then increases,and the pore diameter distribution of various micropores also changes greatly,and the harmful pores decrease first and then increase.
Keywords/Search Tags:Recycled concrete, Carbonization strengthening, Biaxial loading, Chlorine diffusion coefficient, Micro-pore structure, Digital image correlation
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