Waste Paint as Admixture for Glass Fiber–Reinforced Concrete Building Façades

Building façade elements should have aesthetically pleasing geometrical shapes made up of sustainable materials with energy-efficient designs. The low mass-to-high strength ratio of glass fiber–reinforced concrete (GFRC) has the potential to be adopted as a façade material and has been used in the manufacturing of façade elements. The workability of GFRC mixes is comparatively low; therefore, commercial polymer admixtures are used to improve it. The application of commercial polymers may reduce the fire resistance of GFRC mixes due to their easy combustibility. This study investigated the possible application of waste paint to completely replace commercial polymer admixtures in GFRC. It explored the optimum dosage of waste paint to achieve the required strength of a GFRC mix to be used as a façade material. First, characterization of the waste paint was carried out using its rheological properties and solid content, which were compared with commercially available polymer and paint. Subsequently, the effect of different dosages of waste paint (i.e., 0.5%, 1%, and 2% by mass) on the workability and mechanical properties of GFRC mixes (e.g., compressive and flexural strength) was evaluated. Water absorption and porosity were also evaluated. Finally, the combustibility of GFRC mixes with waste paint was evaluated to qualitatively assess fire performance when compared with polymer GFRC mixes. The experimental results demonstrated that the addition of waste paint to the GFRC mixes improved workability. Furthermore, the mixes with a waste paint dosage of less than 1% showed no significant variation in compressive strength compared with the commercial polymer mix. However, the mix with 1% waste paint enhanced flexural strength by 34% whereas a further increase in waste paint content was observed to reduce flexural capacity due to an increase in porosity. Finally, the fire performance of the mixes showed that waste paint is a noncombustible material and can be used as a potential substitute for polymer admixtures in façade applications.