Study on Road Durability of Multilevel Built-In Waterborne Epoxy Micro-Surfacing

Micro-surfacing has been commonly used in engineering applications as a preventive maintenance technology. However, given its low temperature stability and insufficient adhesion between layers, micro-surfacing leads to the insufficient durability of pavements and shows poor resistance to flaking and rutting easy to scatter, etc. Although the aggregate meets the requirements, micro-surfacing has an unreasonable gradation. Moreover, despite satisfying the requirements, the emulsified asphalt lacks bond strength, high temperature stability, and rutting resistance. To address these limitations, this study proposes a design method using multilevel dense built-in gradation waterborne epoxy micro-surfacing and investigates the main factors that affect road performance to improve the road durability of micro-surfacing. The particle size characteristics of different proportions of waterborne epoxy and emulsified asphalt mixtures were analyzed via laser particle size analysis test to study the curing time of waterborne epoxy resin (WER). According to the design system of the multilevel dense built-in gradation (MDBG) and the Bailey method, three types of micro-surfacing gradation were designed. The relationships of gradation, oil-stone ratio, and WER content with the abrasion and water resistances of micro-surfacing were tested by conducting 1 h and 6 d wet wheel abrasion tests. Results show that the curing of WER involves two stages, and that the blend ratio affects the curing time. The coarse aggregate ratio R_CA of MDBG can be used to design different gradations, and R_CA should be set between 0.5 and 1.0. The application of WER can improve the mixture abrasion and rutting resistance of micro-surfacing, whereas an appropriate aggregate gradation, oil-stone ratio, and curing time are identified as prerequisites for WER with an optimum content of 5.0% to 7.0%.