Influence of Aggregate Gradation and Mineral Admixtures on the Properties of Permeable Concrete: An Experimental Study

Strength and permeability are crucial design factors for permeable concrete (PC), but limited research has examined the influence of aggregate size and mineral admixtures on PC properties. In the studies, the constant head permeability method was used to find the coefficient of permeability of the PC, as there is no standard method for measuring it correctly and precisely in laboratory conditions. X-ray fluorescence spectroscopy, scanning electron microscopy, and Fourier-transform infrared spectroscopy analyses were performed on cement, fly ash (FA), and microsilica (MS) to characterize their morphology, chemical properties, quality, and reactivity. Also, the experiment aims to investigate the influence of various aggregate grading (single-, two-, and three-particle size gradations), MS and FA, and water-to-binder ratio (0.20, 0.25, and 0.30) with a constant C/A ratio of 0.25 on the compressive strength (CS), split tensile strength (STS), flexural strength (FS), permeability, and porosity of PC. The findings demonstrate that three-particle size gradation mixes give higher CS, STS, and FS than single- and two-particle size gradations. For single-sized aggregates, permeability decreases with increasing particle size. A combination of three-particle size gradations results in the lowest permeability. The maximum CS and maximum permeability for the combined use of MS and FA are found at the replacement levels of 5% and 10%, respectively. The investigation also established the correlation between porosity and permeability.