The utilization of Recycled Concrete Aggregate (RCA) as an unbound base product in the highway environment is extensively examined in a new white paper available from the Construction Materials Recycling Association (CMRA). The purpose of the white paper was to provide the information needed to show governmental highway engineers at all levels an objective view of using RCA as a base product in roadwork.
CMRA estimates that about 140 million tons of concrete are recycled annually in the United States, and the most common end market is as a base product for roads. “Recycled Concrete Aggregate: A Sustainable Choice for Unbound Base” looks at all aspects of RCA’s use in this market, from incoming material, processing, specifications, pros and cons, and cost advantages. It also includes the results of a survey to state highway departments of transportation that yielded 38 responses on how they are using the material.
According to the CMRA white paper, “Recycled Concrete Aggregate is currently being used to some degree in the vast majority of the state Departments of Transportation across the country. RCA has proven to be both a viable and valuable alternative to the use of virgin aggregates for base courses. The performance is equal to, if not better than, virgin aggregate base course when used appropriately. Significant research has been conducted and published for over 10 years. An AASHTO specification has been in place since 2002. Potential concerns, including precipitates, leachates, durability testing and the existence of asphalt pavement and brick have been addressed.
The paper was organized and written by Cecil Jones, president, Diversified Engineering Services. Jones is the retired chief materials engineer for North Carolina’s DOT, and past head of AASHTO’s Task Force On Recycled Materials. As such, he is familiar with the barriers that RCA has faced in the past and what questions DOT personnel want answered before they will approve a recycled product for use in roads.