Dalhousie University research explores use of recycled gypsum in concrete

Jan 20, 2024

The Gypsum Association (GA)—in partnership with Divert NS, in Nova Scotia, Canada— has announced its support for Dalhousie University Phase II research exploring the viability of using construction and demolition (C&D) waste gypsum in concrete.

The research, led by Pedram Sadeghian, associate professor and Canada research chair in sustainable infrastructure at Dalhousie's Centre for Innovation in Infrastructure (CII) in the department of civil and resource engineering, already shows promise as a means of diverting waste gypsum panels from landfills and into a new product.

By incorporating recycled gypsum powder in concrete mixes, GA says it can reduce the amount of cement needed. The result is concrete with a lower carbon footprint.

"As durability is important for the majority of construction materials, our research group at Dalhousie University aims to study the durability of concrete containing recycled gypsum by monitoring compressive strength and potential expansion after exposure to selected environmental conditions. such as moisture and salt particle penetration, that are common to concrete structures exposed to the environment," Sadeghian explains.

Gypsum is commonly used in cement manufacturing in small percentages; however, Dalhousie's Phase I research demonstrated that gypsum could be a viable supplementary cementing material when combined with fly ash in concrete. Project outcomes from the initial study already have been shared in the Journal of Cleaner Production.

Phase I of the project (2018-2020) was supported by Divert NS, which in addition to funding research and development initiatives, delivers education and awareness programs, works collaboratively to develop and implement stewardship agreements, and promotes innovation through the development of value-added manufacturing.

"Divert NS is always looking for innovative waste diversion projects in Nova Scotia," says Jeff MacCallum, CEO of Divert NS. "Dr. Sadeghian's research represents a significant opportunity for the C&D sector to reduce wallboard waste, and we’re enthusiastic about potential GHG reductions if gypsum is proven a viable concrete additive."

"We are very pleased to join Divert NS in supporting research that may improve numerous environmental outcomes," says GA Executive Director Stephen H. Meima. "The gypsum industry is committed to landfill diversion of C&D gypsum panel waste and Professor Sadeghian's work demonstrates that waste gypsum panels may have value beyond their service life in buildings and homes."

Phase II research will take place over the next two years. During that time, the durability of various concrete mixes containing gypsum powder recycled from waste drywall will be the primary focus. A total of 81 specimens will be prepared and tested under three environmental exposures and three exposure durations. Results will be used to understand the performance and environmental benefits of concrete containing recycled gypsum over the life of structures.