Abstract
Pervious concrete was investigated for potential use as a permeable reactive barrier (PRB) for treatment of acid mine drainage (AMD). Pervious concrete mixtures of varied water-cement ratios = 0.50, 0.40, 0.35, 0.30, 0.27 and cement contents = 300, 360, 380, 400 kg/m3 were prepared. Dolomite and granite aggregates types of 9.5 mm size were employed. Tests done were density, compressive strength, porosity. Water treatment was determined by analysis of the influent and effluent AMD after passage through the pervious concrete.
It was found that a filter thickness of at least 500 mm was required to increase the pH of acidic mine water from 2.8 pH to 5 - 7 pH value, and corresponding reduction in electrical conductivity. When used in the filter mix design, the granite aggregate gave better treatment performance compared to the dolomite aggregate. The concrete PRB treatment led to effective removal of major metals from the AMD. The treatment reduced the metals in the AMD by 30% SO4, 99% Fe, 50-83% Mn, 85% Ca, 30% TDS. There was, however, a noticeable increase in magnesium concentration in the water effluent by 49-66% Mg. These results are short-term tests and further work is underway on the system’s life expectancy.