Incorporating recycled concrete aggregate in pervious concrete pavements

Pervious concrete is a green alternative to conventional pavements with minimal fine aggregate and high void content. Pervious concrete allows water to infiltrate through the pavement thereby reducing the runoff and the requirement for stormwater management systems. The effectiveness of pervious concrete for use in the Canadian climate is currently being evaluated. Virgin aggregate sources within Canada are limited and other sources need to be evaluated for use, such as Recycled Concrete Aggregate (RCA). Recycling concrete from curbs and gutters, sidewalks and parking lots reduces the amount of concrete being put into landfills. Using RCA in new concrete has multiple advantages to the environment namely, reducing dumping at landfill sites, reducing gravel mining and reducing hauling of virgin aggregate and therefore reducing emissions. The purpose of this research was to incorporate RCA into pervious concrete to create a very sustainable concrete product for paving. The research methodology involved substituting the coarse aggregate in the pervious concrete mix design with 15%, 30%, 50% and 100% RCA. Cylinders were cast in the laboratory for each percentage of RCA and also a control pervious concrete mix design containing only virgin aggregate. Each of the concrete batches that were mixed was tested for slump, temperature, entrained air, and unit weight. The testing was done to determine whether the batches were consistent and within the recommended limits specified. A single sized RCA was used and it was saturated prior to the batching process. Once the cylinders were cast they were tested at 7, 14 and 28 days for compressive strength. Some of the cylinders were cut and tested for permeability and void content. The testing showed that pervious concrete with an optimum RCA content has strengths, voids and permeability comparable to that of pervious concrete containing only virgin aggregate. In short, the paper shows that RCA provides an environmentally friendly material choice for pavements.