Micro-surfacing mixtures with reclaimed asphalt pavement: Mix design and performance evaluation

Abstract

Micro-surfacing is used as a pavement preservation and maintenance technique to improve surface skid resistance, abrasion resistance, water resistance, and durability. Recently, reclaimed asphalt pavement (RAP) has been used in micro-surfacing mixtures with good promise and improved sustainability. The use of RAP helps reduce greenhouse gas emissions during the production of new asphalt pavement materials and enhance the environmental sustainability of the overall transportation infrastructure. However, exploring how to reasonably use RAP in micro-surfacing while also considering its unique yet complicate asphalt-emulsion-water-cement-aggregate system is still worth further investigation. The objective of this study is to propose a modified mix design and material evaluation approach for RAP micro-surfacing mixtures so that its performance, especially as rut filling materials, can be satisfied for field application. In this paper, the optimum asphalt content (OAC) of RAP micro-surfacing mixtures was determined according to the optimized rutting resistance. Rejuvenators were incorporated to evaluate their effectiveness on RAP micro-surfacing mixtures. Laboratory compaction was proposed in the mix design stage to simulate the rolling in the field. Furthermore, to support the design concept and to verify the mix designs for acceptable engineering properties, several performance tests were used to evaluate the mixing condition, moisture susceptibility, shear resistance, and skid resistance of RAP micro-surfacing mixtures. The results showed that the OAC decreased with the increase of the RAP content. The rejuvenators restored the initial characteristics of RAP binder in micro-surfacing and improved its mixing time and rutting resistance. Laboratory compaction could accelerate the curing and improve the consistency and rutting resistance of the mixtures. Adding RAP could improve the mixing time but there was an optimum RAP content. With the increase of RAP content, the moisture and skid resistance of micro-surfacing were improved. RAP usage had no consistent impact on the interlayer shear strength between micro-surfacing and its substrate structure. Overall, with appropriate application, high content RAP can be added to micro-surfacing with both environmental and engineering benefit.