Reliability Analysis And Life Prediction Of Hybrid Fiber Reinforced Concrete After Freeze-thaw Cycles

Fibers with different quality and geometrical form in the concrete can improve not only the balance of the equilibrium of three-dimensional distribution,but also the coordination between aggregate and fiber.In this paper,fibers are added to the matrix concrete capacity to improve the frost resistance of the concrete.Basalt fiber and steel fiber were matched with durafiber respectively.These two kinds of mixed fibers were put into concrete matrix for a comparative experimental research.The quick freezing method which is widely used was chosen in the freezing and thawing test.Based on the comparative analysis of the concrete mass loss,relative dynamic elastic modulus loss and the mechanical properties(compressive strength and splitting tensile strength)loss after 0?25?50?75?100?125?150?175?200 freeze-thaw cycles,the fibers' effect and mechanism in the aspect of improving the frost resistance ability and reducing the mechanical properties losses are elucidated.The method of freeze-thaw reliability analysis based on cumulative fatigue damage theory was used to analysis the reliability of the fiber reinforced concrete.The logarithmic distribution was used in the analysis procedure.The number of freeze-thaw cycles were taken as random variables.Mass loss,the same evaluation index of quick freezing method and slow freezing method,was tried to be taken as the random variable.Combined with freeze-thaw damage criterion,limit state equation was established.Reliability index was obtained by using the center point method.For quick freezing method:mass attenuation model was used to predict freeze-thaw cycles of the concrete under laboratory conditions;The damage index ?)was calculated based on test results,the growth model of ?)was carried out to predict freeze-thaw cycles of the concrete under laboratory conditions.For slow freezing method:damage index ?' for the evaluation criterion of slow freezing method was proposed,and its rationality was verified by the test results of another scholar;For the almost non load bearing structure,compressive strength failure criterion of slow freezing method was taken as the standard.Combined with relevant standard,freeze-thaw cycle life of the concrete under laboratory conditions was predicted by calculating the bearing capacity reliability index.Taking Shenyang as an example,combined with the gas phase statistics,the freeze-thaw life of fiber concrete in actual environment was predicted according to the freeze-thaw cycle life under laboratory conditions.