Evaluation of Marshall Stability Design Principles: Applied to Cold In-Place Recycling

Abstract

The objective of this paper is to document limitations and robustness issues with Marshall stability (MS) testing for cold in-place recycling (CIR) mix designs. This paper focuses efforts on MS because many departments of transportation are using this test for CIR design, and the data presented in this paper supports abandonment for any type of CIR mix design. Unconfined compressive strength (UCS) and indirect tensile strength data is used throughout the paper for benchmarking, as both tests are used in various capacities for in-place recycling designs. Portland cement and asphalt emulsion binders were assessed in this paper. In comparison with UCS design curves with cement, MS results for emulsion were not as rational and often did not respond to emulsion content changes in a logical manner. MS repeatability was poor for the materials evaluated in this paper. Replicate design curves ranged from all points below a design threshold (i.e., all emulsion dosage levels failed to meet the design criteria) to all points above a design threshold (i.e., all emulsion dosage levels successfully met the design criteria). The typical minimum MS criteria (5.56 kN) was exceeded without any emulsion for specimens oven conditioned for 2 h at 40°C. A notable limitation of the data presented in this paper was that retained MS (i.e., assessment of moisture conditioning effects) was not performed comprehensively throughout the work.