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

Freezing-thawing damage is one of the important subjects of durability research onconcrete structure. Concrete structure of many regions in our country endure coldweather in the winter, and often suffer from random monotonous or cyclic loading in thesafe period of use. Therefore, It discusses stress-strain relationship of frozen-thawedconcrete under monotonous and cyclic loading in this paper, which will provide basicdata for research of seismic performance on concrete structure. It also has an importanttheoretical research value to disaster prevention and reduction of concrete structureproject.In this paper, the two batches of concrete prism block were subjected to rapidfreeze-thaw cycle test, which Maximum number is400times. During the text, thequality and dynamic elastic modulus were measured every25times. The relationshipbetween quality loss rate, relative dynamic elastic modulus and the freeze-thaw cycleswas established. The five groups of test blocks respectively enduring freeze-thaw cyclesof0,100,200,300,400times were subjected to monotonous and cyclic loading andtheir failure mode were observed. The failure mode under monotonous loading wascompared with it under cyclic loading. The relationship between the peak stress andstrain under monotonous and cyclic loading and the cycle time of freeze-thaw wereestablished. The stress-strain curves after different freeze-thaw cycles were described.At last, analyzing the test result of the frozen-thawed concrete specimen withdifferent cycles under monotonous and cyclic loading. Using the software of Matlabto fit with the two-stage formula and working out the parameter a and b for the ascentstage and descent stage of uni-axial compression, and describing the relationshipbetween the time N of freeze-thaw cycle and them. The unloading curves under cyclic loading were fitted with the formula for not freeze-thaw concrete, and working out theparameter n. Using the formula n=1+sε u/εpwhich is modificated from the formulan=1+0.7ε u/εpdescribing the relationship equation between the parameter s and thetime N of freeze-thaw cycle. The reloading curves under cyclic loading were fitted withthe formula for not freeze-thaw concrete. And describing regularities of distribution ofthe parameter n and α from the reloading curves.