Ggbs Cement-based Composites Anti-sulfate Acid Rain Erosion Performance

"Acid rain" is a worldwide environment pollution problem, and itcan also cause deterioration to cement-based materials. This paper basedon the acid rain corrosion on the bridge concrete and it's protectionmethod at foshan first cycle road, studied the sulfate acid rain resistancesof cement paste and mortar containing GGBS by soaking dry/wet cycles,and the acid rain developed according to the typical acid rain in China isof sulfate. The influence of acid rain on the destroy of ggbs cement-basedmaterial was determined by observing the appearance and measuring thestrength,mass,neutralization depth of the specimens treated by thedry/wet cycle tests, and the SEM,XRD and chemical analyzed methodwere used to post the corrosion mechanism. Meanwhile, concretespecimens with the best GGBS replacement were made subjected to spraydry/wet cycles experiment in order to further know the resistance ofconcrete to acid rain.From the research, it is found that: during the corrosion of simulatingacid rain, the color of cement-based materials can change to yellow, whendrying the surface of specimens has white crystal, and also has thelayered desquamation. The strength and mass of the speciem up first andthen go down. The pH value and CaO content decrease all the time, theneutralization depth of the cement mortar increased all along theexperiment. For the total performances, the admixture of 20%～30%GGBS is favorable to the resistance of sulfate acid rain and Cl^- diffusion.The experimental results show that the trends obtained by soaking andspraying methods are consistent with each other. However, corrosion rateis higher in the soaking method compared to the spraying method; theexperiment results of cement paste, mortar, conctere also consistent witheach other, and the corrosion of mortar can present the majorityperformance of concrete.Thermodynamics analyses indicate that the deterioration of Portland cemen-based materials to acid rain is spontaneous; the Portland cementbased-materials is not durable at all, but the addictive of GGBS can retardthe corrosion evolution. From the research results and SEM,XRDanalyses, the conclusion can be made: in the course of corrosion, duringthe early time, the corrosion of SO₄^2-take the dominant role, it acts withthe Ca²⁺ which released by H⁺ to produce CaSO₄·2H₂O, and fills thepore, so the mass and strength increased; during the later time, H⁺ willgradually take the dominant role, and the SO₄^2- can also induce expansionof specimen. So the deterioration of GGBS cement-based materials wascaused by the dissolution of H⁺ and the expansion of SO₄^2- together, andthe coexistence of H⁺ and SO₄^2- accelerates the deterioration process. Inthe acid rain region, concrete material should choose cement and mineraladdmixture which have better ressistance to acid rain corrosion first, andshould also take low water to binder ratio.