Investigation on Compaction Behaviour of Modified Asphalt Mixtures

Abstract

Asphalt mixture is conventionally used as wearing and binder courses in flexible pavement. While placing the asphalt mixture, compaction is applied using field roller compactors. In this process, the air voids of the asphalt mixture are decreased, which helps the mix to achieve various volumetric properties. These properties are critical for the long-term performance of pavement. Improper compaction may result in premature failure during the pavement’s service life. The compaction characteristics of asphalt mixtures are dependent upon several factors, including but not limited to aggregate gradation, asphalt binder, and compaction temperature. Therefore, it is crucial to investigate the compaction properties of asphalt mixtures with varying constituents. The objective of this study is to compare the compaction behaviour of modified and unmodified asphalt mixtures using the Superpave Gyratory Compactor (SGC). The major scopes of this study encompass modified sample preparation, performing compaction studies on asphalt mixtures, and estimating and analysing various compaction indices. Next, the compaction indices of two asphalt mixtures were compared to assess their key differences in the compaction mechanisms. The findings indicate that the modified asphalt mixtures provided superior resistance to densification but required substantially more effort to compact in the field, with a Construction Densification Index (CDI) of 4089.02 compared to 549.20 for the unmodified asphalt mixture. Whereas the unmodified mixture exhibited a lower resistance to initial compaction, with a gyration number of 16 to attain its Locking Point (LP) value, compared to the modified mixtures, which required 55 gyrations. It is envisaged that this study will provide important insights into the factors that govern the compaction characteristics of asphalt mixtures and thereby help construct pavements with long-term performance.