Increasment of Durability of Concre -te Against Sorrosion Acid With Li -me Stone



Concrete corrosion in Water and wastewater network pipes, treatment factory structures, slaughterhouse and structures in industrial zone with acidic rain always is a serious problem. Concrete corrosion in water and wastewater environment is usually generated and accelerated by biological activities. Hydrogen sulfide in wastewater, efflux in sewer atmosphere and with biologic activities of special bacteria on concrete surface, it changed to sulfuric acid. Generated sulfuric acid can corrode concrete. Also acidicrain in polluted industrial zones can corrode concrete structures in these locations.
In this research effect of using limestone Lime aggregate instead of silicic aggregate on concrete durability against 1 percent sulfuric Acid solution is evaluated. Only the paste of the concrete that was made by silicic aggregate can react with corrosive solution. So concrete surface becomes rough and there are many places for growing bacteria and penetrating corrosive solution between paste and aggregate. After corrosion development, uncorroded aggregate without paste, is disparted from concrete bulk. But in the case of the concrete that was made by limestone aggregate, paste and aggregate are corroded in same rate and there is more material to react with corrosive solution. Also in the case of limestone aggregate, there is a micro neutralized environment around concrete surface, that is prevent corrosion process.
For evaluating this change in concrete material, chemical accelerated corrosion test method according to ASTM-C267-01 standard is used. There are two sets of cylindrical concrete speci -men that was submerged into 1 percent sulfuric acid solution. These two sets are similar in water/ cement ratio, size of aggregates, cement type, molding and curing conditions. But there is just one difference about using silicic aggregate for first series and limestone aggregate for second series of samples. Weight, dimension, pressure strength and appearance of specimen were measured at different immersion periods. Data analyses showed that using limestone aggregate has a good effect on concrete durability. According to test results, in comparison to silicic concrete, the limestone concrete showed about 50% increase in durability against acidic corro -sion.