Workability of Hot-Mix Asphalt

TLDR

Workability refers to properties of hot‑mix asphalt that affect its movement through equipment, handwork, and compactibility on the roadway. The study defined workability as the ease of placing, hand‑working, and compacting HMA and aimed to evaluate a prototype device that could detect changes in workability caused by mix characteristics. The authors evaluated a prototype device designed to measure HMA workability and detect changes caused by mix characteristics. The prototype device successfully measured HMA workability, revealing that aggregate type, nominal maximum aggregate size, binder type, and temperature influence workability, with PG76‑22 mixes less workable than PG64‑22, and that workability generally increases with temperature, while gradation shape alone had no effect but interacted significantly with other factors.

Abstract

The term "workability" has been used to describe several properties related to the construction of hot-mix asphalt (HMA). For this study, workability was defined as a property describing the ease with which HMA can be placed, worked by hand, and compacted. This definition provides a term that is applicable to movement of HMA through equipment to the roadway, handwork of HMA, and compactibility on the roadway. The primary objective of this study was to evaluate a prototype device to measure the workability of HMA mixes that could identify the change in workability due to changes in mix characteristics. The findings of this study led to successful design of a device to measure the workability of HMA mixes. The workability of HMA was affected by aggregate type, nominal maximum aggregate size, binder type, and temperature. Gradation shape did not have a significant effect on workability. However, numerous two- and three-way interactions that included gradation shape were significant. Mixes modified to meet a PG76-22 were significantly less workable than mixes containing an unmodified PG64-22. There was a relationship between workability and temperature that showed increased workability at higher temperatures.