ABSTRACT
Concrete overlays are discussed in detail in ACI 325.13R-06 Concrete Overlays for Pavement Rehabilitation (ACI Committee 325 2006) and Smith et al. (2002). The Smith et al. report was used as the basis for ACI 325.13R-06. Concrete overlays may be placed over either asphalt or concrete pavements. Information about concrete overlays and recommendations for deter-
mining which concrete overlay alternatives should be used are provided in Chapter 3 of ACI Committee 325 report 325.13R-06. Factors to consider include user costs, lane-closure requirements, traffic control considerations, desired performance life, duration of construction, and local experience with rehabilitation alternatives (ACI Committee 325 2006: 11-13). For example, the US States of Iowa and Texas have developed considerable experience with bonded concrete overlays, and are thus more likely to consider them and use them under the appropriate conditions than other agencies. Many other agencies, however, are very reluctant to use them. In practice, it is almost always necessary to consider asphalt overlay
alternatives as well as concrete overlays. Advantages and disadvantages of different types of pavement overlays, as well as typical life estimates, are reviewed in ACI 325.13R. As an example, structurally bonded concrete overlays are similar to asphalt overlays, although with a longer life (15-25 years versus 10-15 years) (ACI Committee 325 2006: 12). It has been found that concrete overlays deteriorate much more slowly than asphalt overlays, and are likely to last significantly longer (Packard 1994).
