A case study of a pervious concrete quality assurance program

Pervious concrete typically comprises a zero slump mixture with little to no fine aggregate and uniformly graded coarse aggregate. The workability of such mixtures can be highly sensitive to variations in moisture content and compaction effort, leading to large variations in the final void contents for a given pavement project.

Research and experience have shown that pervious concrete mixtures proportioned to have 15 to 25% air void contents should have sufficient infiltration rates to limit storm water surface runoff and adequate strength to avoid raveling. Until recently, however, there were no U.S. standards for the verification of air void content in fresh concrete or infiltration rates for in-place concrete.

To help producers, contractors, and owners verify that their pavement projects will perform as needed, ASTM Committee C09.49, Pervious Concrete, has recently introduced Standard C1688, "Standard Test Method for Density and Void Content of Pervious Concrete" and Standard C1701, "Standard Test Method for Infiltration Rate of Pervious Concrete." These standards were used as part of the quality assurance program for the construction of a parking lot at the Metropolitan Community College (MCC) in Omaha, NE. Using test placements to develop a compaction-density relationship, appropriate mixture properties could be defined without guesswork. Workability tests and unit weight tests per ASTM C1688 were used to screen loads to ensure that we placed only workable concrete that could be consolidated to achieve a target air void content.

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