Use of Recycled Concrete as Unbound Base Aggregate in Airfield and Highway Pavements to Enhance Sustainability

This research evaluated the use of recycled concrete aggregate (RCA) from airfield and highway pavements to enhance sustainability based on engineering, economic, and environmental criteria. The objective was to develop evaluation and construction guidelines by defining the minimum standards for RCA as unbound base. The research approach included contacts with industry representatives, technical assessments, site visits, and performance review of airfield pavements with unbound RCA layers. RCA can be used as unbound base material if produced from uncontaminated PCC. All virgin aggregate tests and their limits are applicable to RCA except the sulfate soundness test, which is waived for RCA due to the incompatibility of PCC components with the chemical reactants used in the test. RCA should not be used where there is a potential for sulfate exposure from subgrade soils, ground water, or other external sources. RCA from ASR-distressed PCC can be used considering site conditions. RCA is not a hazard to the environment. An economic analysis can be conducted by considering initial material and construction costs for both RCA and virgin aggregate.