Sulphate and sulphide corrosion in livestock buildings, Part II: Reinforcing steel corrosion

Part II of the paper deals with the effect of the corrosive livestock building environment on the reinforcing steel in reinforced concrete. The corrosion of the steel in the test specimens presented in detail in Part I was monitored by measuring the electrochemical potential between concrete surface and the steel at regular intervals. Also, the reinforcing steel was visually inspected after exposure tests were completed and specimens were split to recover the steel. The results indicate that Portland cement (PC) concrete with a 0.5 water/cementitious material (W/CM) ratio provided the least corrosion protection for the reinforcing steel, as might be expected. All mixes containing silica fume, all with a W/CM ratio of 0.4, performed better than PC concrete with a 0.4 W/CM ratio (PC40). Mixes containing high-calcium fly ash (Class C) were less sulphate resistant than the ones with silica fume, whereas those containing slag performed nearly as well as the ones with silica fume. Mixes made with sulphate-resisting cement (SR) were also more resistant than Type 10 Portland cement in both sets of exposures used in these tests. In general, the steel in the specimens that were exposed to hydrogen sulphide and sulphate solution corroded more and faster than those exposed to the hydrogen sulphide gas only. It was also found that in the corrosive test environment concrete corrosion was more critical than reinforcing steel corrosion with the 45 mm cover used.