Mesoscale Simulation of Chloride Diffusion in Concrete Subjected to Flexural Loading

Abstract

In real structures, concrete is always cracked due to various mechanisms such as drying shrinkage, chemical attack, thermal gradients, freezing-thawing cycles, alkali-aggregate reaction and external loading. It has been realized that cracking can significantly accelerate the deterioration of reinforced concrete structure because it provides preferential flow channels and allows more chlorides to penetrate. This paper aims to illustrate the effect of external loading or cracking of concrete on the chloride diffusion rate by numerical simulation method. The lattice network model on mesoscopic composite structure of concrete is used to evaluate the diffusion properties of cracked concrete, while the Rigid Body Spring Model (RBSM) is adopted to quantify the parameters of cracking, such as the crack number and width. The chloride diffusion coefficient through a single crack is determined as 10000 mm2/h when crack width is larger than the critical value and 3000 mm2/h when smaller than this critical value. Different flexural loading levels are applied to the concrete beam samples in order to obtain different damage degree in concrete. By means of a series of calculations, it is indicated that loading can significantly increase the chloride diffusion rate and penetration depth in concrete. Comparison with available test data shows that the proposed model can to some extent reflect the loading effect on chloride diffusion, particularly under higher loading levels than those applied in the tests.