Seal coats, also known as chip seals or surface dressings, play a significant role in the preventive maintenance programs of highways. Aggregate loss (or ravelling) is a common problem with seal coats. It creates a negative perception about the integrity of the roadway and is a safety hazard to the travelling public. It can be the result of physical and chemical incompatibilities which are often accentuated by construction conditions and practices. These include surface dust and moisture in the aggregate, and binder temperatures when aggregate is spread and rolled. Most highway agencies still rely on separate tests to determine the suitability of binders and aggregates, and a need exists for a performance-based test protocol to evaluate aggregate-binder compatibility. A research project sponsored by TxDOT and conducted by the authors resulted in the development of such a test protocol that incorporates anticipated construction and performance conditions. The test is simple, easy to run and does not require expensive, sophisticated equipment. It has shown great promise as a laboratory tool to select aggregate-asphalt combinations that suit local conditions. This paper presents the new test protocol along with results of its preliminary tests. (a) For the covering entry of this conference, please see ITRD abstract no. E217100.
Abstract