System Chemistry to Control Potential Environmental and Safety Hazards of Recycled Concrete Aggregate With Lead-Based Paint

The lead (Pb) content of concrete is often a concern to project managers and environmental regulators. Waste reduction policies give an incentive to limit landfilling of demolition debris, but many material recycling scenarios involve some environmental exposure to crushed concrete. This work observed a demolition project to investigate relative Pb concentrations and solubility of Pb in runoff water. Painted walls were sampled before demolition; mass of concrete was calculated; and a projected Pb concentration for total demolition debris was calculated. An extraction experiment was designed to mimic the environmental performance of using crushed concrete as a paving material for parking lots. This experiment showed that, for expected levels of Pb, very little of the heavy metal moved. Levels of Pb in runoff water remained below drinking water standards. Also, after exposure to a simulated 2 years of rainfall, the concrete retained very high alkalinity, which limits the action of acidic rain. The original document contains color images.