Influence of Water Film Thickness on the British Pendulum Number for Tined Concrete Pavements

Abstract

Wet pavement friction decreases due to the increase in water film thickness (WFT), leading to a significant increase in vehicle crash occurrences. The British Pendulum Test is one of the methods used to measure pavement friction in wet conditions for the input of geometric design and pavement management systems. The British Pendulum Number (BPN) in wet conditions varies with WFT. Following standard procedures, water film thickness was created by spraying water on the pavement surface. However, the measurement of BPN did not include specific information about the thickness of the water film present during testing. To address these issues, WFTs and BPNs were measured using artificial rainfall generated by a rainfall simulator across various intensities, drainage lengths, pavement slopes, and pavement surfaces. This study aims to investigate the influence of water film thickness on BPN for wet pavement friction and provide the WFT corresponding to each BPN measurement for different surface types. BPNs of three test slabs, including a smooth surface and tined surfaces with 16 and 25 mm spacing, were measured under wet conditions by spraying water, and by creating water film thicknesses using a rainfall simulator. This study demonstrates that the BPNs of nontined surfaces and longitudinally and transversely tined surfaces with 25 mm spacing exhibit a significant decrease with increasing water film thickness, whereas those with 16 mm spacing show a slight decrease. These findings are attributed to the lower friction observed in both nontined and longitudinally tined pavements, in contrast to surfaces with transverse tinning.