![]() Higher porosity of RCA leads to a higher absorption. This paste reduces the specific gravity and increases the porosity compared to similar virgin aggregates. Recycled concrete aggregates contain not only the original aggregates, but also hydrated cement paste. Recycled concrete aggregates produced from all but the poorest quality original concrete can be expected to pass the same tests required of conventional aggregates. The crushing characteristics of hardened concrete are similar to those of natural rock and are not significantly affected by the grade or quality of the original concrete. ![]() Most of the unprocessed crushed concrete aggregate is sold as 1½ inches or 2 inches fraction for pavement subbases.Īfter removal of contaminants through selective demolition, screening, and /or air separation and size reduction in a crusher to aggregate sizes, crushed concrete can be used as: new concrete for pavements, shoulders, median barriers, sidewalks, curbs and gutters, and bridge foundations structural grade concrete soil-cement pavement bases lean-concrete or econo-crete bases and bituminous concrete. In general, applications without any processing include: Reinforcing steel and other embedded items, if any, must be removed, and care must be taken to prevent contamination by other materials that can be troublesome, such as asphalt, soil and clay balls, chlorides, glass, gypsum board, sealants, paper, plaster, wood, and roofing materials. The quality of concrete with RCA is very dependent on the quality of the recycled material used. See ACI 555 (2001) for more information on processing old concrete into recycled concrete aggregates. It involves breaking, removing, and crushing existing concrete into a material with a specified size and quality. Recycling of concrete is a relatively simple process. Most agencies specify using the material directly in the project that is being reconstructed. The states that do use recycled concrete aggregate (RCA) in new concrete report that concrete with RCA performs equal to concrete with natural aggregates. ![]() According to a 2004 FHWA study, 38 states recycle concrete as an aggregate base 11 recycle it into new portland cement concrete. Concrete recycling gains importance because it protects natural resources and eliminates the need for disposal by using the readily available concrete as an aggregate source for new concrete or other applications. Construction materials are increasingly judged by their ecological characteristics.
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