University of Vermont Transportation Research Center

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This study evaluates the factors affecting the testing of strength and hydraulic parameters of pervious concrete pavement (PCP), presents results of long-term infiltration monitoring and cleaning operations, and investigates freeze-thaw durability of pervious concrete and the effects of fly ash. The specific objectives of this study were to: (1) determine how rubber capping and sulfur capping affect compressive strength measurements of PCP; (2) determine the effects of height to diameter (H:D) ratio of cylindrical specimens on compressive strength measurements of PCP; (3) compare various methods used to determine infiltration rate of PCP in the field to one another and to laboratory measurements of hydraulic conductivity; (4) monitor two PCP facilities in Vermont for changes to infiltration rate over time; (5) evaluate the effects of various cleaning methods on the restoration of infiltration rates; (6) determine the effects of deicing salts on pervious concrete, using a modified and more field representative testing procedure that involves slow freeze-thaw cycling in drained condition, and (7) determine the effects of cement replacement with increasing amounts of fly ash on the freeze-thaw durability of pervious concrete. In addition, the results of this study were used to suggest correlations to the field observations seen at several pervious concrete sites in Vermont. Capping with rubber pads was found to provide more consistent compressive strength measurements compared to sulfur capping for both H:D ratios studied. H:D ratios less than the standard 2:1 were found to increase results of compressive strength measurements; however, a ratio of 1:1 was found to provide inconsistent results. Compressive strength specimens with H:D ratios less than 2:1 can be divided by 1.1 to estimate compressive strength of 2:1 H:D specimens. Results of laboratory hydraulic conductivity, single ring, double ring and falling head infiltrometer testing were found to correlate linearly to one another with a relation of 1.0 : 1.8 : 1.5 : 9.0 for 6” thick PCP. Long-term field monitoring of infiltration rates indicated reductions of 59% and 26% for the facilities investigated. Cleaning methods were found to differ in effectiveness, with average restoration rates of 21% for street sweeping, 30% for vacuum truck cleaning, 85% for pressure washing, 10% for hand vacuuming, and 100% for combined pressure washing and vacuuming. Sodium Chloride deicing salt at 8%, followed by 4 and 2% resulted in the greatest freeze-thaw damage. Water alone did not result in damage during 100 one per day freeze-thaw cycles. Fly Ash replacement of 10 and 20% showed a decrease in freeze-thaw damage as compared to a control mix with no fly ash replacement.