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4 cement; the binder is a polymer. The overlays are thin, typi- Reference Information System (TRIS) was a major source cally less than 1 in. in thickness and often 0.5 in. or less. of information. Professor Yoshihiko Ohama of Nihon Uni- The substrate is normally a portland cement concrete bridge versity in Japan has maintained a complete bibliography on deck, although in a few instances steel decks or concrete concrete-polymer materials over the past several years, and pavements have been used. his database, which was last updated in 2007, was used in this review (5). The proceedings of the International Con- Definitions taken in part from ACI 548.5R-96 Guide for gress in Polymers in Concrete were searched for information Polymer Concrete Overlays (1) are given in the Glossary at along with other conference proceedings that were potential end of the report. A few of the more important definitions are sources of information. presented in this section. The American Concrete Institute (ACI) has published Epoxy resin--A resin that contains epoxy groups princi- many papers on TPOs in journals and in special publica- pally responsible for its polymerization. tions. ACI Committee 548 Polymers in Concrete has also published several documents on TPOs including a Guide for Monomer --A small molecule from which much larger Polymer Concrete Overlays (1) and a specification for epoxy polymer molecules can be made, usually in liquid form for TPO construction (2). concrete applications. AASHTO has published Guide Specifications for Poly- Multiple-layer overlay --Two or more layers of polymer mer Concrete Bridge Deck Overlays, which has been widely concrete bonded to concrete; normally each layer consists adopted, at least in part, by many agencies (6 ). of an application of resin with aggregate broadcast into the surface. Survey of Transportation Agencies, Material Suppliers, and Contractors Polymer --The product of polymerization, more com- monly a rubber or resin consisting of large molecules formed Survey forms were developed and sent to state DOTs and by polymerization. Canadian provinces. Selected vendors and selected contrac- tors that have had experience with TPOs were surveyed by Polymer concrete (PC) --A composite material in which telephone. The agency survey forms, contained in Appendix the aggregate is bound in a matrix with a polymer binder. A, were e-mailed to agencies. Contractors and vendors were interviewed by telephone. Some follow-up telephone inter- Premix overlay --The method of initially blending a poly- views with agencies were conducted to obtain additional mer binder, with fine and coarse aggregate and fillers, if used, information. and then mixing until all particles are completely wetted. Once the composite has been mixed as required, it is trans- ported and placed. The term applies to polymer concrete. REPORT ORGANIZATION Resin--A natural or synthetic, solid or semisolid organic The report is organized in the following manner: material of indefinite and often high molecular weight, with a tendency to flow under stress. It usually has a softening or Chapter One--Introduction melting range and usually fractures conchoidally. Chapter Two--Literature Findings and Specifications Chapter Three--Performance of Overlays from Slurry overlay --Overlay applied by placing an applica- Surveys and Interviews tion of resin or monomer followed by broadcasting aggregate Chapter Four--Proven Practices onto the surface. Chapter Five--Repair Chapter Six--Conclusions Thin polymer overlays (TPOs) --One or more layers of References polymer concrete bonded to concrete, normally 1 in. or less Bibliography in thickness. Glossary of Terms Appendix A: Questionnaires Appendix B: Stresses in Overlays METHODOLOGY FOR OBTAINING INFORMATION Appendix C: Warranty and Payment Bond Literature Review The information obtained from the various sources was reviewed to obtain the background on the topics listed in A literature review was conducted that included the most the scope. The information was grouped into the subtopics likely sources of information on TPOs. The Transportation used in the chapters. The factors that influence performance

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5 were derived from these sources. The best practices are a Little information on costs and repairs was obtained from summary of the knowledge that has produced overlays that the literature and from surveys and interviews. For this rea- have performed well as reported by the states and provinces. son, these issues are addressed in only a cursory manner.