Evaluation of the Physical/Chemical Properties of Recycled Concrete Aggregates (RCA) and RCA-blends for Materials Acceptance and Water Quality Impacts
Construction and Maintenance Practices
Environmental Process, Natural Resources
Research Idea Scope
PennDOT has developed material specifications on Recycled Concrete Aggregates (RCA) in an effort to expand the use of recycled materials in highway and maintenance applications. The specifications were developed from the most recent available research and case studies conducted by other state Departments of Transportations (DOTs) and the Federal Highway Administration (FHWA). The DOT and FHWA research has focused on the use of RCA from controlled sources, such as DOT salvaged concrete pavements. RCA derived from a variety of other sources has not been evaluated and would require additional testing of the material to demonstrate that it would meet DOT aggregate specification quality standards. In addition, there are environmental concerns on the potential impact of high pH leachate from RCA to receiving waterways and water bodies. Our proposed research is to develop a set of engineering (gradation) and environmental (pH) test criteria for select applications of RCA and blends by: 1. Developing a correlation between laboratory leachate (pH) test values and field sampling pH results for a range of RCA and conventional aggregate gradation blends of materials. (0/100, 25/75 and 50/50 blends of recycled concrete aggregates vs. virgin aggregate blends). 2. Utilizing the results to establish a set of laboratory test criteria for select RCA and blends applications for material supplier approvals. 3. Conducting field studies of RCA and blends leachate to correlate the laboratory test results and to quantify pH water quality impacts at critical downgradient distances or points.
Urgency and Payoff
The research findings will provide DOT’s data for evaluating the properties of RCA and blends; reduce their material approval requirements; and quantify the potential environmental impacts. This data will be beneficial towards expanding the use of these recycled materials in highway and maintenance applications and possibly reduce project costs.
Kenneth J. Thornton, PennDOT-Bureau of Design, Pollution Prevention Section, Telephone: 717-787-0459