Recycling lead-based paint contaminated deconstructed masonry materials as aggregate for Portland cement concrete-A cost effective and environmental friendly approach

摘要

Four lead-based paint (LBP) contaminated deconstructed masonry materials (two types of concrete blocks and two types of clay bricks) were crushed and used to replace all natural aggregate in conventional concrete. To reduce cost, the crushed materials were neither sieved nor re-graded. After their physical properties and lead-leaching ability were characterized, these masonry materials were used for concrete with various mix proportions. The workability, lead-leaching ability and compressive strength of the concrete were studied. A cost-savings analysis was conducted to compare such a masonry deconstruction method with tradition ones (including LBP removal, hazardous and non-hazardous material disposal) for three hypothetical buildings. The results indicated that after being used as aggregate in Portland cement concrete, the lead is sequestered, or rendered non-leachable, due to the high alkalinity of Portland cement, and the concrete no longer has the toxicity characteristic for lead. Well-designed and well-manufactured concrete made with all LBP-contaminated, recycled aggregates can have satisfactory workability and strength for a variety of constructions, including roadways, parking lots and foundations. The savings from eliminating LBP removal and waste material disposal as well as minimizing the use of secure landfills range from approximately $4.63 to $412.80/m~2, depending on the size of the deconstruction project and the applicable environmental protection regulations. Recycling such masonry materials as concrete aggregate is a cost effective and environmentally friendly approach.