Image: UBC Okanagan
Engineering professor Sumi Siddiqua and graduate student Priscila Barreto.
Researchers from the University of British Columbia’s Okanagan campus have found a way to juice up a traditional building material, potentially opening it up for wider use both locally and around the world.
UBC Okanagan engineering professor Sumi Siddiqua and graduate student Priscila Barreto have found a way to strengthen compressed soil—commonly known as rammed earth—by cutting it with specific binding agents.
Siddiqua explains that concrete is still the principal building material used in most conventional construction but that progressive builders are starting to seek out cheaper and more environmentally friendly materials.
She thinks rammed earth could be an answer, now that she and Barreto have found a way to make it stronger.
Rammed earth is still used by a significant chunk of the world’s population, but the material has significant structural limitations.
To improve this, the pair tested the addition of calcium carbide residue and fly ash as binding agents in the rammed earth. They found that, when cured for 60 days, the walls containing binding agents were 25 times stronger than those without.
The increased strength greatly improves their potential for use in modern construction.
“The core of our challenge was to pinpoint the strongest composition of binding materials,” says Siddiqua. “While research shows that some amount of clay is required to stabilize soils, having a mechanism to better bind the soil grains is the key.”
Barreto, an international student from Brazil, began this research while at UBC Okanagan as an undergraduate and continued the work into her graduate studies.
“In countries like Brazil and regions like the Sertão in the country’s northeast, rammed earth is commonly used as a building technique,” explains Barreto. “The opportunity to enable people to build stronger and safer structures with natural soil is one of my central motivations for doing this research.”
Siddiqua says there is clearly a demand for this type of material and the technique has been used in small cities in Canada, including the Okanagan, where small residential homes are being built with readily available materials.
“We targeted rammed earth structures because local construction engineers have approached us looking to improve traditional rammed earth structures with stabilization techniques like ours,” she says.
The research was published in the journal Construction and Building Materials, and was supported by both a Discovery and ENGAGE Grant from the Natural Sciences and Engineering Council of Canada.
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