Reliable Laboratory Tests: A Prerequisite for the Design of High-Quality Slurry Surfacing Mixtures

Abstract

Surface treatment with slurry surfacing is a quick and cost-effective technique to restore the condition and performance of a road surface, compared with the replacement of the wearing course. It is therefore not surprising that cities and municipalities, faced with increasingly tight budgets, choose slurry surfacing to maintain their roads. A slurry surfacing with good performance and a long service life requires, above all, a well formulated mixture and a good control of the execution quality. Slurry surfacing could then even be considered for ultrathin wearing courses on new pavements. From 2016 to 2020, the Belgian Road Research Centre (BRRC) was engaged in a 4-year research project called BeP2S (Better Performing Slurry Surfacing) financially supported by the Belgian Bureau for Standardization (NBN). The project focussed on laboratory testing, gathering data and field experience, assessing the link between laboratory and field performance, and the mix design process. This paper is dedicated to the European test methods of the EN 12274 series (“Slurry surfacing–Test methods”), as well as some alternative test methods, which were evaluated (complexity, relevance for the mix design process, …) and improved in terms of test conditions, precision, and discriminating power. Five performance-related tests proved to have sufficient ability to discriminate between mixtures with variations in mix design. Recommendations were made for the ranges within which the laboratory test results should fall in order for the slurry surfacing to perform well.