Research On Properties Deterioration And Corrosion Prevention Technology Of Concrete In Acidic Water

Pyrite exists in broken mountain belt which lies in K64+400-K92+000 of the highway from Yichang to Badong in Hubei Province. Acidic environment results from the oxidation of pyrite in pit, tailings pile and scrap heap, thus rivers were polluted. In acidic environment, cement hydration productions like C-S-H gel and CH will react with hydrogen ion and decompose, it will cause loss of Ca2+ and Mg2+ resulting in the deterioration of mechanical properties and durability of concrete. As well, the passive state of steel is destroyed and the corrosion of steel is promoted. So the durability and anti-corrosion technology of highway cenment concrete in acidic enviroment was researched in this paper.The researchment contents are shown as following:(1) Accelerating methods of the concrete deterioration in acidic environment are researched. Solutions of different pH and sulfate concentration were selected to accelerate the process of deterioration. Results show that acid of pH<2 can not be selected as the accelerating solution, and sulfate concentration should be choosen according to actual aggressive medium. Because sulfate concentration may causes different process of deterioration to concrete. Concrete deterioration in acidic environment should be characterized by strength which can reflect the internel structure change in stead of mass loss and appearance that can only show the change of the face.(2) Effects of mix design to the concrete acid resistance were researched. Factors like type of cement, Lithology of aggregate, water binder ratio, mineral admixtures, and chemical addtions were researched. SRPC (High sulphate resistance Portland cement) 20%-50% FA of grade I, or more than 50% GGBS(ground granulated blast-furnace slag) of S95 can be used to improve the acid resistance of concrete. In acidic water of pH≥2, Lithology of aggregate has little effect to concrete acid resistance.(3) Until desired ages, the paste was tested for micro-chemical composition analysis and microstructure observation using SEM and XRF. The basic reason for deterioration of concrete in sulfuric acid is the degradation of C-S-H gel in matrix. Increasing the content of SiO2 to low the C/S in cement paste can improve the acid resistance of concrete. At the same time, impermeability of concrete should be improved.(4) Prevention technology of concrete in acidic water in actual projects. Based on the actual pile and type of corrosion, special mixes for concrete durability and construction requirements were designed. C40 concrete with high content of admixture and low DRCM is prepared for the piles. Exposed experiments are being carried out in actural environment.