Drainage performance evaluation of reclaimed concrete aggregate

Reclaimed concrete aggregate (RCA) is used as replacement or mixed with virgin aggregates to be used in embankments, hot-mix asphalt (HMA), Portland cement concrete, and base/sub-base layers in pavement systems. However, RCA has not received a lot of attention as a drainage media because of low abrasion resistance, which causes excess fines content, and the potential of clogging material on filter fabrics. The performance of RCA as drainage material has not been evaluated by many researchers, and the limited information restricts its use. This paper describes the testing methods used to evaluate RCA as a French drain material; the French drain system collects water runoff from the road pavement and transfers it to slotted pipes underground and then filters through aggregate. RCA was tested for its physical properties including specific gravity, unit weight, percent voids, absorption, and abrasion resistance. RCA cleaning/washing methods were also applied to evaluate the fines removal processes. A petrographic examination was conducted by using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffracation (XRD). The permeability of RCA was also tested using the No. 4 gradation. The results showed that RCA has a high abrasion value, that is, it is very susceptible to breaking down from abrasion during transportation, stockpiling, or placing. The permeability tests show that the No. 4 gradation does not restrict the flow of water; however, the flow rate is highly dependent on the hydraulic system itself.