Abstract
Many chemicals associated with manure are identified as having a detrimental effect on concrete. The major problem, however, is the effect of hydrogen sulphide and its derivatives, which leads to sulphuric acid corrosion. Sulphuric acid corrosion can be caused due to attack of aggressive media naturally existing in environment. Another possibility of corrosion formation is biogenic acid effect through the agency of microorganisms. The corrosion resistance of concrete depends on the type and chemical composition of the cement as well as the pH of the attacking acid.
The paper is focused on the study of chemical corrosion of concrete samples resulting in increased leaching due to sulphate environment. Sulphate aggressive environment was represented by 0.5 % solution of H2SO4 (pH value of 0.99) and 0.5 % Al2(SO4)3 solution (sulphate concentration of 3,000 mg/L). Distilled water used as reference medium as proper leaching simulation environment. Concrete composites with/without coal fly ash cement replacement were used for the experiments. The laboratory experiments proceeded during the 60 days.
No significant differences in chemical composition of concrete samples before and after the experiment were observed except for the iron, aluminum and silicon concentrations. Summarizing the results of chemical composition of the liquid media before and after the experiments, the initial concentrations of Ca in leachates have been increased 2.0 to 3.5, 16.4 to 18.3 and 4.1 to 5.1 times for distilled water, sulphuric acid and aluminum sulphate, respectively. In point of view of calcium leaching, the concrete sample with fly ash was confirmed to be more resistant to sulphuric acid in comparison to the sample without fly ash. The initial concentrations of Si have been increased 1.9 to 1.91, 3.2 to 3.3 and 1.89 to 1.92 times for distilled water, sulphuric acid and aluminum sulphate, respectively. In case of all liquid media the increasing character of pH values have been noticed. The most visible increase of pH value to the alkali region was observed in case of distilled water (more than 1.8 times for both types of composites).
