How Are the Subsurface Drainage Outlets in Iowa Roadways with Recycled Concrete Aggregate Base Performing?

This paper discusses subdrain outlet condition and performance in Iowa roadways. A forensic test plan was developed and executed during wet summer conditions covering over 230 and 120 drain outlet locations of the newly constructed jointed plain concrete pavement (JPCP) and the hot mix asphalt (HMA) over JPCP sites, respectively. The tufa formation (i.e., calcium carbonate deposits) is the primary cause of drainage outlet blockage in newly constructed JPCP sites using recycled portland cement concrete (RPCC) as a subbase material. Lesser tufa formation from the use of RPCC base in JPCP was observed with the: (a) use of plastic outlet pipe without the gate screen type rodent guard, (b) use of blended RPCC and virgin aggregate materials. The observations of moisture-related surface distresses nearby blocked drainage outlet locations in HMA over JPCP indicates that compromised drainage outlet performance could accelerate the development of moisture-related distresses in HMA over JPCP.