Mechanical and thermo-gravimetric properties of unsaturated polyester resin blended with FGD gypsum Habib Tabatabai ⇑ , Morteza Janbaz, Azam Nabizadeh Department of Civil and Environmental Engineering, University of Wisconsin-Milwaukee, WI 53211, USA highlights  Properties of polyester resin blended with FGD gypsum were studied.  Ambient mechanical properties were markedly enhanced with up to 50% gypsum content.  TGA results showed major improvement in mass retention with higher gypsum contents.  FGD gypsum can form an exterior barrier protecting the interior areas from fire.  FGD gypsum can potentially be a low-cost additive for fire resistance in polymers. article info Article history: Received 13 January 2017 Received in revised form 5 November 2017 Accepted 6 December 2017 Keywords: FGD gypsum Industrial by-product Polyester resin FRP Thermo-gravimetric analysis Mechanical properties Fire resistance abstract A major disadvantage of polymeric materials is their flammability and generation of toxic gases under fire. Mechanical and thermo-gravimetric properties of an unsaturated polyester resin blended with Flu-Gas Desulfurization (FGD) gypsum were assessed. Limited open flame tests were also performed. Results indicate that ambient mechanical properties of polyester resin can be enhanced with up to 50% FGD gypsum content. TGA results show significant improvement in mass retention proportional to gypsum content. Under direct fire, FGD gypsum can form a protective physical barrier on the resin’s exte- rior surfaces. FGD gypsum can potentially be an effective and low-cost fire-resistance additive for polymers. Ó 2017 Elsevier Ltd. All rights reserved. 1. Introduction Over the past two decades, there has been increased interest in the use of fiber-reinforced polymer (FRP) composites in civil/struc- tural engineering applications. The primary uses of FRP laminated composites have been in the repair and seismic retrofit of struc- tures. FRP laminated composites are sometimes wrapped around inadequately-reinforced columns to increase strength and ductility of columns when subjected to earthquake loads. They have also been used to improve the flexural/shear strength of beams and slabs. Full-size FRP members have also been used in new construc- tion. Although FRP composites offer enhanced corrosion resistance and superior strength-to-weight ratio, they are susceptible to sig- nificant damage in fires. Typical resins used in manufacturing FRP composites (ther- mosets such as polyester or vinyl ester resins and thermoplastics such as polyethylene or polyurethane) are all extremely flammable and produce significant toxic smoke. The lack of fire resistance is a major impediment to widespread use of FRP composites and other polymer-based materials in civil engineering structures, especially in indoor applications. Polyester resins are typically used in FRP composites due to their rapid curing, good mechanical properties and relatively low cost. As compared to epoxy resins, polyester resins are more sensitive to elevated temperatures [1]. Some fire resistance requirements may be satisfied by using fil- lers such as Alumina Trihydrate (ATH) in the resin. On the other hand, specialized resins containing halogens such as bromine, or phenol resins, or additives such as antimony oxide can be used for fire resistance as well. However, these measures may not pro- vide adequate protection [2]. In 2004, a study sponsored by the Federal Aviation Administra- tion (FAA) reported relationships between structure, composition, https://doi.org/10.1016/j.conbuildmat.2017.12.041 0950-0618/Ó 2017 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail addresses: ht@uwm.edu (H. Tabatabai), mjanbaz@uwm.edu (M. Janbaz), azam@uwm.edu (A. Nabizadeh). Construction and Building Materials 163 (2018) 438–445 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat