The Constitutive Relation Of Stirrup-confined Concrete Experiment Research Under Acid Rain Environment Erosion

Acid rainwater corrosion is a complex chemical process. Once the concretematerial eroded by acid rainwater, the material performance deterioration occurs as thedegree of erosion. The performance degradation of concrete material insaide manychemical composition will be involved in the chemical reaction. Concrete both microand macro seriously affects the mechanical properties degradation of concrete, to lead toa decline of its useful life, and affact the quality of people's production and life.Over the past two decades, the study of sour rainwater corrosion of concrete focuson material damage mechanism of concrete, macro and micro performance,thedegradation law and so on. However, the degradation of the overall performance ofreinforced concrete elements is less and the research of confined concrete stress-strainrelations in sour rainwater corrosive environment has never been studied. Reinforcedconcrete member after corroded by acid rain, its internal steel bar and concrete workability will be severely affected, so this configuration of stirrups in the reinforcedconcrete member the effects of the lateral restraint of concrete will be greatly weakened,especially its deformation capacity has been significantly down. The seismicperformance of reinforced concrete member and structure analysis will have muchimpact, therefore, in this paper, the constitutive relation of confined concrete aftercorroded by acid rain experiment research has important theoretical significance andapplication value.?1?In order to study the stress-strain curves of confined concrete, total of48reinforced concrete prism specimens were designed, size of150mm×150mm×450mmand the corrosion test were made under four different sour rainwater environment. The variable parameters are PH value, SO42-concentration, hanger bars characteristic value,and the etching time. Four acid rain environment A?PH4.5, SO42-0.002mol/L), B(PH3.0, SO42-0.002mol/L), C (PH3.0, SO42-0.06mol/L), D (PH1.0, SO42-0.1mol/L?.And the specimen after erosion was axial compression test, through experimentmapped the constraints in the measured stress-strain curve of concrete.?2?After the corrosion of stirrups obtained by regression of uniaxial compressivestress-strain curves of confined concrete rise section is divided into two parts, the firsthalf of rising period belongs to the flat stage, presents the concave curve form, the slopeis very small; After the rising part and the decline curve of concrete and corrosionshapes are basically identical. After erosion curve integral taper shape, the decline curvechange steeper.This paper still adopts the traditional two stages (the rise and declinesection) to establish the corrosion of acid rain stirrups under the constraint of concretestress-strain curve.?3?Corrosion of concrete elastic modulus, peak stress, peak strain, limit strainchange by test analysis. And reflect the corrosion environment, hanger barscharacteristic value and the corrosion time as a parameter, and involves the acidifieddepth, with the test data to determine the rising and declining period of equation and therelated parameters of expression.In conclusion, the confined concrete constitutive model in acid rain environmentalcan more accurately reflect properties of material mechanics by erosion solutionconcentration erosion, time stirrup characteristic value, and acidification depth.Research results such as regression of constitutive relation equation and determine theparameters in the formula, etc, can be applied to the southwest acid rain area corrodedby acid rain, the nonlinear analysis of reinforced concrete structures.