Investigation on Clogging Potential of Recycled Concrete Aggregate in French Drain Systems

Recycled concrete aggregate (RCA) has been used as replacement for virgin aggregates in road foundation, embankment, portland cement concrete, and hot-mix asphalt. The use of RCAs in drainage systems (i.e., base/subbase layer and French drain) has not received much attention because of the poor drainage performance of RCAs. Two major causes are (1) the accumulation of excess fines precipitated on geotextile and (2) deposition of calcite precipitation over time. To date, not many studies have been conducted on the drainage performance of RCAs. This limited and unavailable information hinders the use of RCA as drainage materials although there are many benefits to these in promoting sustainability in geotechnical and pavement engineering systems. In this paper, the drainage performance of RCA, No. 4 gradation used in a French drain system, has been investigated. Physical properties (i.e., abrasion resistance, gradation, absorption, etc.) of RCA were investigated, and a number of permeability (constant-head) tests were conducted. With the permeability test, the effect of fines (less than 75 µm) on the RCA permeability was evaluated. Lastly, accelerated calcite precipitation testing was devised and conducted to evaluate long-term performance of RCA associated with the calcite precipitation that can reduce permittivity of geotextile.