Study On Self-Blunting Of Crack And Its Mechanism In Smart Concrete

Possessing excellent piezoelectric properties and electric conductivity, Carbon Fiber Reinforced Concrete (CFRC) is a kind of smart concrete and has its own special merit. Especially its good electric conductivity provides the fine condition for carrying out electro-deposit technology on the CFRC. With the support of the National Nature Science Funds, this paper primarily explores and discusses the method of crack's self-blunting and its mechanism.This paper, applying the electro-deposition technology, analyzes and studies the crack-blunting method of CFRC by Finite Element Simulation (FES) and experiment. Finite Element Method (FEM) is used to quantificationally simulate the current density distribution of the whole CFRC sample, and to explain the mechanism and reason for precipitations' depositing in the crack tip. Experimental phenomena and results in this paper perfectly agree with that of the FES. The results from the FES prove mat current density near the crack tip is 2 quantity-level greater than other positions of the CFRC sample, therefore, precipitations are firstly deposited near the crack tip and are also the most. Experimental results manifest that crack tip is completely blunted and the sample's surface is almost covered by precipitations which are about 1-1.5mm thick; Chemical composition of precipitations on the sample's surface and in the crack tip is analyzed, and the result shows that it is the same as that of the concrete itself. So precipitations on the sample's surface and in the crack tip are helpful to rehabilitate the noumenon materials of concrete.Finally, in order to essentially expound main mechanics properties, this paper adopts Weibull statistic theory to evaluate bending strength of CFRC whose cracks or damages have been blunted. The reason that Weibull modulusm and eigenstrength bO are increased, and that cracks or damages is how to influence m and σ0 are expressed by Weak Loop Theory (WLT). The CFRC sample is always ruptured in the place where materials weakly resist outside force, and because the cracks' or damages' distribution of CFRC is random, bending strength of CFRC takes on dispersed. The numeric analysis result of bending strength shows that m and σ0 will greatly rise with the increase of electro-deposition time. According to the above discussion, the conclusion that bending strength of CFRC is greatly improved can be drawed. The results of whole experiment indicate that applying electro-deposition technology will be an effective method of blunting crack tip and healing crack.