Experimental Study And Theoretical Analysis On The Mechanical Properties Of Concrete After Freezing And Thawing

The concrete of the bridge infrastructure under soggy saturated or soppy state in the North Sea marine environment take place freeze-thaw damage, as the temperature changes positive and negative alternately brought by the sea water freeze-thaw. Frost resistance is an important aspect of durability of concrete structure. The mechanic performance of concrete will be destroyed after freezing and thawing. For these reasons research on the mechanical properties of concrete after the role of freeze-thaw cycle is of great significant meaning to project. In this paper, the major contributions are summarized as follows by experimental research and theoretical analysis.1,Concrete cubic specimens and mortar cubic specimens with a size of 100mm×100mm×100mm were made according to the characteristic of concrete of the Qingdao Gulf Bridge infrastructure. Freezing-thawing cycle test were carried on using of these concrete cubic specimens and mortar cubic specimens. The freeze-thaw cycles include0,100,200,300.The weight loss are measured on each frost-resistance grades;2,The uniaxial loading experiments, splitting-tensile experiments and biaxial compression experiments of concrete specimens and mortar cubic specimens under normal environment and after freeze-thaw cycles have been carved out with triaxial test system. The failure paterns of concrete are described, The loss of concrete specimen mass , elastic modulus and stress-strain relationship are got;3,Based on the test results and concrete micro-mechanical, concrete was taken as a three-phase composite consisting of cement mortar matrix, aggregates and their interfaces. To consider the non-uniformity of the various components, the nature of the material of the various components was assignment in accordance with the Weibull distribution. Using constitutive relationship of elastic damage mechanics to describe the mechanical characteristic of concrete mesoscopic. The concrete test block is numerically simulated on meso-level by RFPA, the compressive strength is got, together with the tensile strength of concrete and stress-strain relationship;4,Through theoretical analysis and the test results, relationship between the decreasing percents of strength of concrete and the freeze-thaw cycles is analyzed, the strength reduction equations were got with the changes in the number of freeze-thaw; 5,Based on the damage mechanics and Ottosen failure model, a frost damage failure model is established with elastic modulus and Possion ratio under damage are the damage variable.The frost damage failure model can provides a theoretical reference for Durability assessment of concrete of the Qingdao Gulf Bridge infrastructure.