Partial Cement Replacement in Concrete with Gypsum Powder Recycled from Waste Drywalls

Construction industry is one of the most significant contributors to environmental issues in today's world. For this reason, sustainable approaches in building industry have always been sought by researchers in this domain. Cement manufacturing process, for example, emits considerable amounts of greenhouse gases contributing to global warming. Replacing cement with other materials which have less environmental footprints has been considered a solution. Construction and demolition waste disposal, also, could cause environmental issues in landfills. Gypsum drywalls account for a considerable amount of construction waste which contains a noticeable amount of gypsum. Utilizing recycled gypsum from waste drywalls as a partial replacement for cement in concrete could address both problems regarding the impact of construction on the environment. In this study, recycled gypsum powder from waste drywall will be used as a partial replacement for cement in concrete. Five concrete mix designs which include 0, 10, and 20% of recycled fine gypsum powder and whole gypsum are considered for this study. Since it has been proven that gypsum does not function well as the only partial replacement of cement, 50% of each mix design is dedicated to fly ash. Three cylindrical (100 mm x 200 mm) specimens of each mix design are planned to be tested at 7, 28, and 90 days. This paper will introduce the combination of fly ash and recycled gypsum as a sustainable replacement for cement in concrete and suggest more environmentally friendly concrete for our infrastructure.