High Calcium Ash Incorporated Into Clay, Sand and Cement Mortars Used For Encapsulating of Heavy Metals

Many heavy and toxic metals are found in variable concentrations contained in the High Calcium Ash (HCA) produced by direct combustion of the bituminous limestone. Huge quantities of ash will be produced when bituminous limestone is utilized as energy source for electricity production or retorting process to produce crude oil in Jordan. One of the main serious environmental impact of this ash is the leachability of heavy metals and its potential contamination of the surface and groundwater reservoirs in the catchment area of Wadi Al-Mujieb. Encapsulation of Lead, Zinc, and Manganese ions were investigated by mixing of HCA with sand, cement and clay (kaolin) mortars. HCA was added with different percentages (e.g. 0%, 3.5% and 10%) to variable ratios of sand-cement-clay mixtures. Beside heavy metal encapsulation analysis; the unconfined compressive strength, water consumption and permeability were carried out for the produced mortars. The results shows that an effective heavy metal encapsulation were achieved with 10% HCA added to 25% clay, 50% sand and 25% cement mixture. Pb and Mn was encapsulated, very low Zn was detected and leached from the mortars. On the other hand, the maximum unconfined compressive strength (16.83 MPa) was reached when 10% HCA was added to the mixture of 25% clay, 25% sand and 50% cement. The permeability was decreasing with increasing HCA, because of the pozzolanic composition of HCA similar to Ordinary Portland Cement (OPC).