Numerical Analysis Of Stress Effect Concrete Sulfate Attack

Chemical reaction caused by environmental factors play a vital role in the durability deterioration of the concrete materials, the early failure of concrete structure and the shortened lifetime of structural services. Sulfate attack is one of the environmental factors that induced the concrete durability damage. The damage mechanisms of the concrete durability caused by the environmental sulfate attack are that, the sulfate ions penetrate into the concrete and react with its component to produce harmful crystals, which lead to the expansive strain and form stress effects in concrete. The establishment of stress effect in concrete caused by sulfate attack is necessary for analyzing the deterioration process of concrete materials and the durability design of the concrete structures. By theoretical modeling and numerical simulation, this paper investigated the stress effect in concrete caused by ettringite-induced volumetric expansion under sulfate attack. The main contents and conclusions are as follows:(1) Based on the diffusion-reaction law of sulfate ions in concrete and Fick second law and reaction kinetics, the expansion volume strain in concrete under sulfate attack, in which the ettringite as the inner expansive product of concrete is considered, is proposed.(2) Depending on Galerkin method and the variational equation of Elasticity, the plane equations of stress effects in concrete under sulfate attack, and its weak form is established, while considering the expansion volume strain in concrete under sulfate attack, and proceedingly form the basic equations of finite element method to analysis the force effect of concrete caused by sulfate erosion.(3) The Radial Basis Point Inerpolation(RPIM) meshless method is used to solve the strain of concrete under sulfate attack by basic equations of finite element method. For the problem of the stress effect in concret under sulfate attack, the corresponding solving format was given. Using MATLAB software, a2D static meshless analysis program was developed, and the volumetric expansion strain and stress effect in concrete under sulfate attack have been further analyzed.(4) Utilzing the developed computer program, the plane stress effects in concrete at a certain time under sulfate attack are numerically investigated. The results show that concrete strain in concrete border area is larger attacked by the sulfate and strain farther away from the border area is smaller. There is tension stress near the concrete plane angle point attacked by the sulfate attack while compressive stress at the border and internal. The Internal compressive stress is greater than the compressive stress near the border. The calculated results play an important role in reference value to the analysis on failure of concrete structures damage due to the erosion product.