Classification of pulverized coal ash. Part 2: Leaching properties of concrete with pulverized coal fly ash as partial cement replacement

摘要

In part 1 the leaching behavior of pulverized coal ash is dealt with. addressing leachability as a function of the liquid-to-solid ratio and as a function of pH. In this report the leaching behavior of cement-based products, containing pulverized coal ash is described. The utilization of pulverized coal fly ash as an admixture in cement has been prompted by the beneficial properties of coal fly ash. The coal fly ash can be used in the clinker production and as a partial cement replacement due to its pozzolanic properties. As a result of discussions on the environmental effects of coal ash utilization the leaching properties of cement mortars containing coal fly ash were studied in a previous study. The actual cement concrete tubes containing cement, sand, coal fly ash, gravel and water were tested for their leachability, using a standardized leach testing procedure. The test is based on the assessment of intrinsic leaching properties. The results are compared with data obtained from another study on pure cement/coal fly ash/sand mortars. In addition the results from a study on a size-reduced cement/fly ash mortar are given as a function of liquid-to-solid ratio and contact time. The information gained from that study is relevant to assess the potential long-term effects after complete deterioration of the cement-based matrix and the influence of particle size on leaching. Based on the intrinsic information obtained in these studies, estimates are given for the long-term release of trace contaminants from coal fly ash in concrete applications. 21 figs., 18 tabs., 5 appendices, 30 refs.