Idaho Degradation Test Study

Project Details







Adrienne Woods


Idaho Transportation Department


Aggregate tests, Materials, Specifications, Test procedures

Project description

The Idaho Degradation Test (IT-15) is a modified version of a degradation test developed by Washington State DOT in 1959 and is one of several tests used to qualify or disqualify aggregate sources and products. With time, the original research data and the criteria that established the Idaho Degradation Specification has been lost. This lack of data prevents ITD from full understanding the significance of the test results. The test itself has poorly defined procedures causing variability in results between individuals and labs. This test was developed and implemented when ITD performed the source testing and consistency may not have been an issue. At this time, it is unknown if variations are inherent in the test procedure or attributable to differences in how the test is being performed by the individual testing firms. This test needs validation to gain a better understanding of the test method and its results as it relates to aggregate quality. This research will be the first step to quantify the differences within the test, establish clear direction in how to process the aggregates for testing and compare results to other nationally recognized test procedures on the exact same material. As current aggregate sources become depleted and a need for developing new sources arises, ITD needs to ensure that the specification is established on sound and current data. This will enable ITD to prevent the use of low-quality aggregate on the roadways while allowing for an appropriately conservative specification. This research will gather all existing documentation into one place. New data will be generated and categorized to create a dataset that can be expanded in the future. ITD will have updated data to support the Idaho Degradation Specification or potentially propose new or modified specifications. Further, the research could lead to the addition of other degradation tests used to establish the suitability of aggregates.