A perspective of water movement across an organic cutback interfacial layer

Abstract

In order to restrain vertical water movement into pavements, a cutback is applied between the base and asphalt concrete. This article provides an evaluation and analysis of vertical water movement through organic cutbacks. The guiding objectives were to ascertain pourability of cutbacks by establishing their rheology, to assess dependence of water movement rate across cutbacks on materials used and time, and to determine whether this water flow is through diffusion. Two Arabian asphalts were mixed with kerosene as diluent at varied ratios to form cutbacks that were applied on compacted model base combinations made of Crusher Run Rock and laterites. Water movement across the cutback was monitored over time using moisture probes. Results of data analyzed show that the cutbacks were pseudo-plastic which behaviour was shear rate specific. The main factors influencing water movement ranked in order of significance were base combination, asphalt type, cutback composition and duration of flow. The experimental water flow data at the cutback bottom do not fit onto Fick’s law implying that this flow through the cutback is not by diffusion. The study points to a possibility of interactions between water and the cutback internal components which is an area of further research. There is limited information on diffusion coefficients for water flow across petroleum products like cutbacks which should also arouse research interest.