Investigation of boundary layer impact on pervious concrete

Abstract

Industrial application of pervious concrete (PC) is limited by uncertainty in assessing performancecharacteristics in design phase. Compaction increases uniformity of characteristics in mass production.Spatial distribution of porosity indicates existence of boundary layers in laboratory samples, whichaffect mechanical properties of PC specimens and applications. This study analyses the impact ofdesign parameters on boundary layers and porosity distribution of PC. The effect of boundary layersobserved in laboratory scale samples is vital in scaling them up for industrial applications.Approximately 2400 laboratory specimens of 150 × 150 × 150 mm3were cast with varying aggregate-to-cement (A/C) ratio (2.5–7.0), aggregate-size-distribution (12–25 mm), compaction energy (15–75blows from standard proctor rammer) and compaction energy distribution (2 distributions in 3 layers)with 6 replications. Porosity and porosity distributions were analysed using image analysis techniques.The A/C ratio and compaction were observed to impact characteristics of the bottom boundary layer,which varies in thickness up to 25 mm. Optimising design parameters not only enhances theperformance of pervious concrete but also optimally reduces the boundary layer effect. The boundarylayer of the top face is not significantly affected by design parameters and was observed to be ratherconstant at 10 mm.