Experimental evaluation of the effect of aggregate gradation on strength gain and drainage ability of pervious concrete

Pervious concrete (PC) is a promising solution for urban stormwater management, yet achieving an optimal balance between mechanical integrity and hydraulic functionality remains a critical challenge. Although previous studies have examined compressive strength and permeability, the quantitative interplay between these properties under controlled aggregate gradation has not been clearly isolated. This study systematically evaluates five PC mixes (N6, N67, N7, N8, and N89) incorporating single-sized and gap-graded coarse aggregates (ASTM No. 6 to No. 89). Uniform mix design, mixing, and compaction procedures were applied to isolate the effect of gradation. Experimental tests included compressive and flexural strength, water absorption, infiltration rate, permeability coefficient, porosity, and cross-sectional structural analysis. As gradation shifted from coarser to finer, porosity increased from 12.6% (N6) to 19.7% (N89), resulting in a 250.8% rise in infiltration rate (5823 to 20,424 mm/h) and a 150% increase in permeability (1.06 to 2.65 cm/s). Conversely, compressive strength decreased from 14.89 MPa to 8.52 MPa (–42.8%). Among the mixtures, N8 achieved the most balanced performance. These findings highlight the critical role of aggregate gradation in tailoring PC properties for applications requiring both structural capacity and effective drainage.