Wood-based pulp mill fly ash (PFA) could be an economically sustainable and low-carbon binder for cement, said the team from the University of British Columbia Okanagan.
Waste materials from pulp and paper have long been seen as possible fillers for building products but normally end up in landfill. The researchers are developing guidelines to use the materials for road construction.
The team was particularly interested in PFA, a non-hazardous commercial waste product. The North American pulp and paper industry, for example, generates more than 1m tons (907,000 tonnes) of ash every year by burning wood in power boiler units for energy production. When sent to a landfill, the producer pays about $25-50 per ton, so mills are looking for alternative uses for the materials.
“Anytime we can redirect waste to a sustainable alternative, we are heading in the right direction,” said UBC associate professor Dr Sumi Siddiqua, who co-published the new research with postdoctoral research fellow Dr Chinchu Cherian.
“The porous nature of PFA acts like a gateway for the adhesiveness of the other materials in the cement that enables the overall structure to be stronger and more resilient than materials not made with PFA,” said Dr Cherian.
“Through our material characterisation and toxicology analysis, we found further environmental and societal benefits that producing this new material was more energy efficient and produced low-carbon emissions.”
The construction industry is concerned that toxins used in pulp and paper mills could leach out of the materials, said Dr Siddiqua, but the research reportedly found that the cementation bonds were so strong that “little to no” release of chemicals was apparent.
Further research is required to establish guidelines for PFA modifications to ensure its consistency, Dr Cherian said, but she is confident the research is on the right track.
“Overall, our research affirms the use of recycled wood ash from pulp mills for construction activities such as making sustainable roads and cost-neutral buildings can derive enormous environmental and economic benefits. And not just benefits for the industry, but to society as a whole, by reducing waste going to landfills and reducing our ecological footprints.”
The research was published in the Journal of Cleaner Production with support from the Bio-Alliance Initiative and Mitacs.
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