Sumi Siddiqua’s (left) research group at UBC investigates low-carbon building materials for climate-resilient infrastructure. (Image: UBC Engineering)

“Everything old is new again and that is precisely why we’ve been investigating rammed earth construction,” said Sumi Siddiqua, Civil Engineering Professor and Lead Researcher with The University of British Columbia’s Advanced Geomaterials Testing Lab. Siddiqua is part of a research group at UBC Okanagan that’s revisiting old building practices — the use of byproducts and cast-offs — as a way to improve building materials and sustainability of the trade.

Siddiqua’s research group at UBC investigates low-carbon building materials for climate-resilient infrastructure. It uses sustainable additives to modernize an ancient building technology, rammed earth. The construction of rammed earth minimizes the exploitation of virgin materials and primarily uses locally available earthen materials.

One such alternative is wood fly ash, a byproduct of pulp mills and also fly ash that is a byproduct of coal-fired power plants, explained Siddiqua. Industry has been trying to find a use for materials like fly ash that predominantly end up in landfills. Better described as a fine powder, fly ash shares the same strength and texture characteristics as cement, and is often added to concrete to enhance its strength.

According to her, wood ash production is remarkably increasing due to biomass production as a renewable form of energy. “The ash is currently landfilled in vast areas at a cost, incurring environmental concerns and taking up valuable land space. On the other hand, extensive use of coal fly ash and the trend away from burning coal has led to the material's scarcity and high price.”

“There are many benefits to using this material,” said Siddiqua, adding that “Using local soil along with rammed earth products reduces sand exploitation. And just as importantly, this material is not affected by wildfires to the same extent as current wooden structures.”

With international shortages in construction sand, builders are searching for cheap, and readily available materials that are equally as strong, for next-generation cement. Together with BC Housing, a provincial Crown agency responsible for subsidized housing options, UBC’s Build Better Cluster is partnering with Indigenous communities to integrate rammed earth into the construction of new homes.

Under most circumstances, test results show fly ash enhances the structure’s properties and makes it suitable for use in cold and hot climates as load-bearing, non-load-bearing, and isolation panel walls. Fly ash also has the added benefit of providing increased insulation properties and being available in remote communities.

Although Siddiqua doesn’t foresee a huge uptick in rammed earth homes and buildings sprouting up in the short term, the addition of materials like fly ash into composite cements has already begun.

“There is an increasing trend in rammed earth utilization, primarily for aesthetic walls and panels. We hope that with further research in this field, we can draw more attention and trust to using rammed earth as a structural part,” she said.

The next steps to facilitate rammed earth utilization are large-scale laboratory tests to simulate real-life loading situations. “Moreover, our group is investigating the viability of carbon capture and storage in rammed earth to produce net-zero or negative-emission building materials,” Siddiqua added.

The research was supported by a Natural Science and Engineering Research Council of Canada Discovery and Engage grant.

“There is an increasing demand for sustainable building products here in Canada and around the world, and materials like fly ash are just the start of a new and important trend,” Siddiqua said.

This article was written by Chitra Sethi, Editorial Director, SAE Media Group. For more information, visit .