Book Description

Aggregates used in the construction of roads must be durable, abrasion resistant, and freeze thaw resistant in order to perform well in pavement or as base course. The objective of this study was to investigate whether the Micro Deval test will provide better, timelier, and more repeatable information about the quality of an aggregate than the Sodium Sulfate Soundness test. This objective was met by (1) conducting a thorough literature review, (2) testing a variety of soils from across Montana, and (3) analyzing these results to reveal potential trends. The literature review indicated that the Micro Deval test has good repeatability characteristics, and that it correlates well to field performance. Laboratory tests (Micro Deval, L.A. Abrasion, and Sodium Sulfate) were conducted on a variety of soil types to examine the repeatability of each test method, and to examine how well the methods correlate with each other in terms of predicting aggregate durability and degradation. Test results were normalized to facilitate direct comparisons between the three methods. Linear regression of the data points and corresponding confidence intervals were plotted to qualitatively assess agreement or disagreement between test methods. The authors concluded that the Micro Deval test is a suitable replacement for the Sodium Sulfate test as the primary method for evaluating aggregate durability, with limitations. Because there were some inconsistent durability determinations between test methodologies, the authors recommend that the Micro-Deval test results be further supported by a second aggregate durability test whenever the Micro Deval results fall between the cutoff value and plus 30 percent of the cutoff value. In other words, when the Micro Deval test result for an aggregate is between 18 and 24 percent loss, a second test using an alternate method is recommended before any conclusions are made regarding the durability or quality of an aggregate.