Texas Tech University

Project 0-5169

Constructability Review of Surface Treatments Constructed on Base Courses


It is common practice for TxDOT to construct surface treatments (1-, 2- or 3- course) directly over base courses. Such surface treatments may act as either wearing surfaces or underseals (or interlayers). The decision to use surface treatments is based on a number of factors including low life-cycle cost, low initial construction cost, inexpensive maintenance, historically favorable experience, availability of experienced contractors, and availability of sound local materials. Problems associated with surface treatments include flushing/bleeding in the wearing courses, debonding at the interface with the base layer, poor ride quality, loss of aggregate (raveling) and ineffective sealing of the pavement. When a surface treatment is used as an underseal, its failure may lead to accelerated failure of the overlying surface layer. Constructability issues related to surface treatments often dictate their performance. However, a formal statewide constructability review of surface treatments over base has not been conducted either by TxDOT or by other state highway agencies in the recent past. The objective of this research project was to conduct a comprehensive constructability review of surface treatment as practiced by TxDOT districts and to identify best practices. A comprehensive survey of existing surface treatment practices was conducted, both by interviewing highway professionals and by visiting construction projects. Information collected from the constructability review was used to develop a district training workshop and to develop a design and construction guide for surface treatments. The workshop was delivered by researchers at eight regional locations. This report highlights the key findings from the constructability review and its related tasks.

surface treatment review