Properties of Recycled Concrete Aggregates

Properties of Recycled Concrete Aggregates

Recycled concrete aggregates (RCA) have higher water absorption rates than virgin aggregates. Higher absorption rates are indicative of higher volume fractions of old cement mortar sticking with the virgin aggregate particles within the original concrete1-3. ASTM C 33, Specification for Concrete Aggregates, carries a dependence on an abmachine for reduce coal moisture contentrasion loss (by ASTM C 535) of lower than 50% for aggregates used in concrete construction and much less than 40% for crushed stone used in pavements4. In line with the ACI 555 Committee Report4, all RCA with the exception that made from the poorest quality recycled concrete, can be expected to meet these abrasion loss requirements. The abrasion property with the aggregates controls the abrasion resistance with the concrete, a property that's essential for warehouse floors, and concrete pavements. The relative density of RCA is 5%-10% less than that relating to virgin aggregates (VA)5. This is due to bricks in demolished construction waste6 and/or the lower density of the cement mortar that is still honored the aggregates.

Construction and Demolition Debris

Construction and demolition (C&D) debris is excess material produced during new construction, renovation, and demolition of buildings and structures. This debris comprises of materials such as asphalt, brick, concrete, masonry, lumber, shingles, roofing materials, glass, plastics, aluminum, steel, architectural elements, drywall, insulation, wiring, plumbing and electrical fixtures, vinyl and aluminum siding, corrugated cardboard, soil, rocks, tree stumps and other landscaping. Standard construction and demolition operations haul and dispose these materials en masse to separation and transfer facilities in order to permitted landfills. Some C&D facilities may separate materials on site for more processing and recycling. Others simply add materials towards the heaping piles of waste inside the landfill. With the total recorded4 waste stream, 30-40 percent is shipped to municipal landfills, 35-45 percent is shipped to specialty C&D landfills, and 20 to 30 percent of C&D debris is recycled.

Economic Development and C&D Recycling

There are community-level great things about recycling and reuse of C&D debris. Diversion of materials through recycling or salvage supports economic development as well as the improvement of communities. Sometimes known as waste-based development, recycling and reuse industries create jobs and revenue, provide small business development opportunities and job training outlets, minimizing landfill expansion needs.

C&D recycling may be used within a larger industrial development effort to create higher wage jobs with a region. Studies conducted by the Waste to operate Partnership13 and the US Economic Information Study14 indicate manufacturing of secondary materials increases the economic impact of recycling collection and processing fourfold. Wage rates in manufacturing are typically more than those wages in collection or processing. The range and processing phases do provide low skilled and entry-level workforce opportunities in the region.