Development of a Volumetric Mix Design Protocol for Dense-Graded Cold Mix Asphalt

Abstract

Cold mix asphalt (CMA) provides a number of benefits that make it a promising alternative to hot mix asphalt and warm mix asphalt, including reduction in both heating energy and emissions, as well as longer working time for transportation and placement of the mixture. However, the challenges faced in the mix design procedure to control the volumetrics and performance of CMA limit the widespread use of CMA. In this paper, a volumetric-based mix design protocol for asphalt emulsion-based CMA is proposed to consider the residual water retained in the mixture after curing and ensure a uniform process for selection of design emulsion content and preparation of mixture samples. The protocol steps include selection of materials, compaction, curing, density measurements, volumetric analysis, simple performance test, and evaluation of moisture sensitivity. Mixtures utilizing two aggregate sources with different absorptions are used to show examples of applying the volumetric mix design protocol. The design emulsion content is determined based on the volumetric analysis in the proposed design. The moisture sensitivity is also evaluated for the mixture at design emulsion content in the form of tensile strength ratio under modified wet condition. It is anticipated that the proposed mix design protocol advances the current state of practice for all emulsion-related mixtures, such as dense-graded cold mixes and cold recycled mixes.