Reinforced concrete for the manure storage of a farm operation is often exposed to aggressive environmental conditions. Temporary storage of liquid manure underneath barn floors produces corrosive agents generated from aerobic and anaerobic fermentation, causing premature corrosion of reinforcement steel and degradation of the concrete. The rehabilitation of reinforced concrete structures due to corrosion of steel-reinforcing bars is quite expensive compared with the use of more resistant concrete at the time of construction, as it is generally accepted that the quality of the concrete cover that protects the reinforcement is critical in limiting corrosion damage. For Canadian climatic conditions, storage of manure for a period of 6 months, or even longer, is generally recommended, and in some provinces legislated, so that manure spreading can be avoided during winter. Before the manure can be removed from storage it usually has to be agitated, which causes the concentration of the various corrosive gases to increase drastically. Methane and carbon dioxide concentrations increased to a level 2–3 times higher than the level before mixing took place. Hydrogen sulphide concentration increased by a factor of 100–1000, whereas the NH3 concentration was 2–5 times lower. Of these, hydrogen sulphide is the most corrosive agent that leads to the rapid deterioration of concrete floors in barns. It is suspected that the relative humidity of the air, the concentration of various gases and vapours above liquid manure pits and the continuous wetting of concrete floor slats are all contributing factors (Svennerstedt et al., 1999). As a consequence of the concrete degradation, slatted floors have deteriorated, in some instances to the point of requiring replacement in less than 5 years. In order to improve the durability of concrete and the environmental protection under such severe agricultural aggressive conditions, some recent investigations have been carried out in an attempt to find ways to reduce the rate of deterioration by changing the concrete composition (Jiang, 2002; De Belie et al., 1997; Idriss, 2000). The overall objective of this study is to provide the technology to design and construct defences against reinforced concrete deterioration so that manure handling and storage structures will be able to withstand the corrosive environment created by the manure, and last a reasonable service life (25–30 years). In the present study 48 concrete cylindrical specimens, 100mmin diameter and 100mm in height, with a reinforcing steel bar in the centre were exposed to hydrogen sulphide gas and sulphate solution, some for more than 3 years. One half of the specimens was partially immersed in sodium sulphate (20,000ppm) and also subjected to hydrogen sulphide gas (1,000ppm). The second set was subjected to hydrogen sulphide gas only. Each set consisted of 8 different treatments including Portland cement (PC) concrete with 0.4 and 0.5W/CM ratios, PC concrete with 8% silica fume replacement, 25% fly ash and 35% slag of the total amount of cementing material and specimens made of PC concrete with combinations of silica fume and fly ash (6%, 25%), and silica fume and slag (6%, 25%). Finally one treatment was carried out with sulphate-resistant cement.

From the results it can be concluded that high-quality concrete with a low W/CM ratio and sulphate-resistant binder-like type 50 Portland cement (SR) is a simple and cost effective method to produce durable reinforced concrete for livestock buildings.

For more information the full article can be found at http://www.sciencedirect.com/science/journal/15375110