Sulfide and Sulfate Attack on Reinforced Concrete of Livestock Buildings

Abstract

Although reinforced concrete is one of the most durable construction materials, in farm buildings it is subjected to high levels of hydrogen sulfide and sulfate that result in corrosion. This leads to premature deterioration of slatted floors and other concrete components of liquid manure storages. The rehabilitation of reinforced concrete structures due to corrosion is expensive and impractical. Prevention is the better approach. Hazardous gases are released from stored manure. Of these, hydrogen sulfide is the most corrosive. Sulfatereducing bacteria generate sulfuric acid as the end of their metabolism 48 concrete cylinders, 100mm diameter and 100mm high, were made with Portland cement, and various combinations of slag, fly ash and silica fume. Each has a reinforcing steel bar embedded in it. 24 cylinders are half immersed in sodium sulfate (20,000ppm SO4 2-) and also subjected to hydrogen sulfide gas (1,000ppm H2S). The second set of 24 is subjected only to hydrogen sulfide gas. In each set, there are 8 different treatments. Initial results indicate that after 11 cycles of testing over about 22 months that the PC concrete with 0.5 W/C ratio is the least corrosion resistant. All treatments containing silica fume, fly ash or slag, except the fly ash/silica fume combination, performed better thus far than PC concrete with 0.4 W/C ratio. Also, there is an indication that concrete with sulfate resistant cement is more resistant than type I Portland cement. Indeed, sulfate resistant cement concrete was one of the best performers in both sets of tests.