Comparing various characteristics of oven-cured and field-cured prime coat materials applied to granular bases
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A prime coat is defined as a low-viscosity bituminous material such as cutback, asphalt emulsions, or polymer-based chemicals applied onto the surface of road bases in order to protect the base from the penetration of moisture into the base layer. Other functions of prime coat include (1) providing good adhesion between a granular base and the bituminous surface, (2) strengthening the surface of the base by binding the fine particles, and (3) sealing against any voids along the base surface in order to reduce water absorption. To achieve these functions, a prime coat should successfully penetrate the granular base and should cure fully. In this study, field-curing data on selected prime coats was collected during March 12th-18th, 2014 and April 12th-18th, 2014. Oven-curing data was also collected in a laboratory using an adjustable oven. Identical prime coats including the four most commonly used prime coats by TxDOT ((1) Cutback MC-30, (2) asphalt emulsions and cutback mixture AEP, (3) polymer emulsions EC-30 and (4) asphalt emulsions SS-1H and CSS-1H) and base materials were divided into the two types of testing environments, one field-cured, and one in an accelerated and controlled indoor, oven-curing environment. Once the specimens were fully cured, evaluation of the engineering properties of the specimens were carried out in order to determine if oven-cured specimens can be expected to exhibit the same engineering characteristics as the field-cured specimens. Evaluation of water absorption tests, indirect indicator of relative strength, and penetration tests were performed on all specimens for both field-cured and oven-cured specimens. Importantly, a comparison of these results shows the viability of using accelerated, laboratory curing procedures. Prime coat field-testing procedures will be suggested using oven-curing rather than field-curing, reducing the amount of time required for sample preparation. Prime coat testing could conceivably be completed in a single day due to the accelerated curing rates. This advantage would reduce cost and man-hours of new prime coat material testing.