Experimental Study On Constitutive Relationship Of Carbonized Concrete Under Monotonous And Repeated Load

Today, the global atmospheric co2concentration is rising. The Carbonization is oneof the main factors causing durability degradation to the concrete structure.Carbonization changed the concrete interior pore’s structure and chemical composition,which has enormous influence on the mechanical properties of concrete. Concrete’sstress–strain relationship is the main material basis of concrete structure seismicperformance research. This paper aimed at researching the stress–strain relationship ofcarbonized concrete under monotonous and repeated load, which can further improveseismic performance evaluation theory of the existing reinforced concrete structure andhas important theoretical research value to the concrete structure engineering disasterprevention.To explore the stress–strain relationship of carbonized concrete under monotonousand repeated pressure load. At first, this paper designed the three kinds of strength gradeof concrete cylinder specimens. Take some part of the specimen to carbonization testcompletely, got six groups of carbonization and never carbonization test specimen. Foreach set of specimens with equal strain rate applied is monotonous and repeatedpressure load, got stress–strain curve of test specimens under the monotonous andrepeated pressure load.Secondly, by comparing the stress–strain whole curves of carbonized concrete andnever carbonation of concrete under monotonous pressure load and stress–strainenvelope curve under repeated pressure load, to analyze the influence of carbonizationon stress–strain relationship of concrete. The results show that peak strain and ultimatestrain of concrete after carbonization lesser than never carbonization, and the ultimatestrain decreased range is bigger, the brittleness of concrete after carbonization increased, especially after the decline period; the peak stress of concrete have been improved to acertain extent, and the improved range is inversely proportional to the strength ofconcrete.Thirdly, this paper compares the stress–strain load–unload envelope curve ofcarbonized concrete under repeated pressure load with stress–strain whole curve undermonotonous pressure load. The results show that they are almost the same.Finally, this paper adopted the equations adviced by Guo Zhenhai to fit thestress–strain whole curves of carbonized concrete under monotonous pressure load andload–unload curve under repeated pressure load. Got parameters a and b values in theequation of stress–strain whole curves of carbonized concrete under monotonouspressure load, n value in the equation of unload curve, parameters n and α values in theequation of load curve of carbonized concrete under repeated pressure load. This paperhas been established constitutive equations of carbonized concrete and can be used forboth the nonlinear analysis of existing reinforced concrete structure.