Achieving Volumetrics and HMA Compactibility
The Bailey method was originally developed by Robert D. Bailey of the Illinois Department of Transportation in the early 1980s. It is a practical tool that has been successfully utilized for developing and analyzing hot asphalt mixes in the lab and field. The Bailey method provides a good starting point for mix design and an invaluable aid when making adjustments at the plant to improve air voids, VMA and the overall workability of the mix, whether you are using Marshall or Superpave. The paper describes the methodology in detail with some real life examples to help mix designers and contractors better understand the mixes that are currently being used across Canada.
Essentially, the “Bailey Method of Gradation Selection” is a tool for developing and analyzing blend gradations in the lab and field. It gives designers and contractors a better appreciation of aggregate packing and its influence on mix volumetrics and compactibility. The method includes guidelines for evaluating aggregates and the aggregate blend by volume, as well as by weight, and makes provision for the use of Reclaimed Asphalt Pavement (RAP).
The focus of the Bailey method is aggregate packing. In order to better understand aggregate packing, we need to determine what particles form the coarse aggregate structure and which ones fit into the voids created within that structure.
The Bailey Method applies to coarse-graded, fine-graded and SMA mixtures. The method can help explain why some Superpave mixes are difficult to compact. It also provides insight as to why small gradation changes, which often occur during production and are within allowable tolerances, can cause significant changes to mixture volumetric properties and/or field compactibility.
- Bailey Method Achieving Volumetrics and HMA Compactibility Paper (PDF 400KB)
- Bailey Method Powerpoint (PDF 775KB)
- Bailey Method Offers Technicians Volumetric Control (PDF 628KB)