Abstract
Thin maintenance surfaces (TMSs) provide an economical method of extending pavement life for asphaltic concrete or bituminous roads. Two phases of research were undertaken to demonstrate TMSs and establish guidelines for their use in Iowa. The project involved the construction and observation of multiple test sections on four rural U.S. highways in Iowa over a 3-year period. Average annual daily traffic on these highways ranged from approximately 1,000 to 5,000. Test sections included single and double chip seals with various types and sizes of aggregates and two types of binder: cationic emulsion and high-float emulsion. Test sections of microsurfacing, microsurfacing cape seal, and thin-lift hot-mix overlay were also placed. These TMS treatments were compared with control sections. Researchers designed the chip seal test sections, monitored the construction process, and collected quality-control information on materials. The pavement condition index (PCI) and skid resistance were measured and compared for each test section before and after construction. TMSs improved PCI when materials were selected properly and quality construction techniques were used. Success was achieved with chip seal that used graded cover aggregates and small cover aggregates and also with various thin-lift overlays. Difficulties were experienced with microsurfacing aggregates that had few fines. The results of the study reinforce the importance of selecting the right type of TMS, ensuring construction quality, and having favorable weather during and after construction.
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