Experimental Study And Numerical Simulation Of Sulfuric Acid Corroded Concrete

Sulfuric acid is widely present in production and living environm ents,such as industrial plants and urban sewage pipes.Under the long-term effect of sulfuric acid,in the process of sulfuric acid intruding into concrete materials,there is a process of solid decalcification of pore walls and intrusion into concrete po re solution,which leads to corrosion damage of concrete materials.Under the action of sulfuric acid,the corrosion degree and corrosion rate of concrete are mainly affected by the p H value and the mode of action.Therefore,it is of great significance to study the sulfuric acid corrosion characteristics of concrete under different p H values and different mode s of action.This paper conducted a long-term immersion test to study the corrosion process of concrete specimens under the action of sulfuric acid.Obtained the corrosion characteristics of concrete specimens under different p H values and different action modes,and on the basis of experimental research,use COMSOL Multiphysics to carry out the numerical simulation of sulfuric acid corrosion of concrete materials,and verifi ed the reliability of the numerical simulation.The specific research content inclu des:(1)Indoor test research: The corrosion of concrete under the action of sulfuric acid was studied through long-term immersion test.Three control co nditions were considered during the test: Neither change the soaking solution nor clean the surface of the test piece、Replace the soaking liquid but do not clean the surface of the test piece、Replace the soaking liquid and clean the surface of the test pie ce.After the test,a graph of sulfuri c acid consumption related to soaking time was obtained.And through SEM,EDS,XRD analysis to get the surface morphology and mineral composition of the concrete specimens.Research shows: As the p H value in the soaking solution decreases,The corrosion degree of concrete under different control conditions gradually increases.When the p H is 4,the effect is not obvious.When the p H is 3 and 2,the cumulative acid consumption of concrete under the control condition of replacing the soaking liquid and cleani ng the surface of the test piece is1.16～1.56 times that under the cont rol condition of replacing the soaking liquid but not cleaning the surface of the test piece.The cumulative acid consumption of concrete under the control condition of replacing the so aking liquid and cleaning the surface of the test piece is 1.32～5.50 ti mes that under the control condition of neither changing the soaking liquid nor cleaning the surface of the test piece;Replace the soaking solution and clean the surface of the test pi ece,so that the surface layer of the concrete test piece in the soakin g solution will produce different corrosion products.According to whether there is a Ca SO4 loss mechanism and the cleaning effect of the surface l ayer of the specimen,the corrosion is divided into three types,analyzed the relationship between the consum ption of sulfuric acid and the p H value of the soaking solution.When there is no Ca SO4 surface layer formed in the process of sulfuric acid attack ing the concrete,when the p H value of the dilute sulfuric acid soaking solution drops from 4 to 3 or from 3 to 2,the consumption of sulfuric acid is increased by about 7 times,There is a good similar relationship between the corrosion rate and the p H value of sulfuric acid.In the case of C a SO4 attached surface layer formed during the process of sulfuric acid attack on concrete,the Ca SO4 surface layer has a "blocking" effect on the process of sulfuric acid corrosion of concrete,slowed down the corrosio n rate,the similar relationship betwe en the p H value of sulfuric acid and the corrosion rate is completely b roken.The formation of Ca SO4 surface layer in the process of sulfuric acid attack on concrete is an important reason for the destruction of test s imilarity.(2)Use COMSOL Multiphysics to model and analyze the corrosion of sulfuric acid immersed concrete unde r corresponding test conditions.The simulation process of calcium corrosion is considered by the solid-liquid equilibrium curve of calcium ions,and through the adjustment of porosity and tortuosity,the diffusion coefficient of calcium ions when calcium corrosion occurs in concrete specimens under different control conditions is reflected.The acceleration factor F is used to reflect the influence of different p H values on the diffusio n coefficient,the acceleration function g(t)reflects the influence of different control conditions on the diffusion coefficient in the process of sulfuric acid corrosion of concrete,the calcium ion concentration distribution curve c alculated、 the law of sulfuric acid consumption with time and The influence of the surface coating on the corrosion rate of the specimen by the simulation calculation of the concrete specimen is obtained.The test results and the numerical simulation result s are compared and analyzed,and the reliability of the calcium corrosion model is verified.