ACI 548.5R-16 Guide for Polymer Concrete Overlays

ACI 548.5R-16 Guide for Polymer Concrete Overlays. 3.4—Polyesters 3.4.1 Description—Polyester binders used for the prepara- tion of polymer concrete (PC) are two-component systems, with one containing the polyester resin and the second containing the initiator, which is usually an organic peroxide (Ribeiro et al. 2003). The properties of the polyester binder depend primarily on the chemical composition of the poly- ester resin component and are much less infuenced by the selection of the promoter/initiator system, the primary contribution of which is to control the rate of cure. The peroxides, used as initiators, gradually lose their reac- tivity at elevated temperatures (over 90°F [32°C]). Addition- ally, polyesters exhibit a strong odor during application, due to the presence of styrene in the resin, which are regulated by the National Institute for Occupational Safety and Health. Both polyester resin and initiator components should be stored in cool, protected areas. Systems containing solvents and unreactive diluents should not be used. 3.4.2 Polyester properties—All components used for physical testing should be conditioned at 73 ± 2°F (23 ± 1°C) for at least 24 hours before mixing, curing, or testing (Tables 3.4.1a and 3.4.1b). 3.4.2.2 Chemical resistance—Cured polyester binders are resistant to water, deicing chemicals, dilute acids, gasoline, and other petroleum products (Topliyska et al. 2006). Some polyester resins may not be resistant to alkaline substrates. 3.4.2.3 Weathering—The surface aggregate protects the polyester binder from weathering. 3.4.2.4 Permeability—PC overlays will exhibit low permeability, reducing the penetration of chlorides into the substrate that are the primary cause of reinforcing steel corrosion and the subsequent damage. 3.4.2.5 Primers—Priming is always necessary when premixed polyester systems are used. Primers improve the performance of polyester overlays. Polyester resins, epoxies, and methacrylates can be used, but the manufacturer of the polyester should be consulted before selection is made. Poly- ester primer, if recommended by the manufacturer to be the same resin used for PC binders, may be used with premixed systems. Epoxy primers are resistant to the styrene or other monomers present in the polyester resin. Epoxy primers can improve the bond of polyester PC overlays to damp or alkaline substrates, though the application of polyester PC overlays to damp surfaces is not recommended. Methac- rylate primers are solutions of acrylic polymers in methyl methacrylate (MMA) or high-molecular-weight methacry- late (HMWM) monomers. 4.1—General Polymer concrete (PC) is made by combining monomeric or polymeric binders with aggregates. The aggregates and binders can...