Effect of Aggregate Size and Gradation on Pervious Concrete Mixtures

The purpose of this research was to determine the effects of aggregate size and gradation on the unit weight, strength, porosity, and permeability of pervious concrete mixtures. The water-cement ratio (w/c) and cement-aggregate ratio (c/a) were kept constant at 0.29 and 0.22, respectively, with a design unit weight of 2002 kg/m 3 (125 lb/ft 3 ). Fifteen different aggregate gradations were tested and categorized according to nominal maximum aggregate sizes (NMASs) of 9.5, 12.5, and 19.0 mm (0.38, 0.49, and 0.75 in.) and had a range of uniformity coefficients C u . The results indicated that as the porosity increased, strength decreased and permeability increased. In general, as the C u of the aggregate increased-that is, the gradation became less uniform or single-sized and more well-graded-the strength also increased, whereas the porosity and permeability decreased. There appeared to be an optimum/pessimum C u range in which the strength of the pervious concrete reached a maximum and the permeability reached a minimum.