Architects make cement out of salt

A Dubai-based architect duo is looking to break from conventional building practices with an alternative cement conceived in the salt flats of the UAE and made using a problematic waste material.

Wael Al Awar and Kenichi Teramoto, principal architects at waiwai, enlisted the scientific knowhow of universities in the UAE and Japan to create a cement made using brine generated by the UAE’s desalination plants, which remove salt from seawater.

They were inspired by the UAE’s mineral-rich sabkha — salt flats that are part of the country’s wetlands. “It a huge area … that’s often overlooked,” Al Awar told CNN.

Sabkha have been used in architecture before: centuries ago, blocks were hewn from salt flats and used to build Siwa, a medieval town in Egypt close to the Libyan border. But rather than mine the delicate sabkha ecosystem, Al Awar and Teramoto turned to waste brine, which contains many of the same minerals.
The ancient fortifications of Shali at the Siwa Oasis, Egypt.

The ancient fortifications of Shali at the Siwa Oasis, Egypt. Credit: CRIS BOURONCLE/AFP/AFP via Getty Images

The freshwater-scarce UAE has one of the largest desalination operations in the world. It produces roughly one fifth of the world’s brine as a byproduct — approximately 28 million cubic meters a day, according to a 2019 UN-backed report. But discharging brine into the sea can harm marine life. Finding uses for desalination brine has come into national focus, prompting the launch of a 3.4 million AED ($930,000) “Rethink Brine Challenge” earlier this year.
A close up of a sabkha flat in the UAE. The flats contain microbes and are "a living environment [that] actually absorbs CO2," according to architect Wael Al Awar.

A close up of a sabkha flat in the UAE. The flats contain microbes and are “a living environment [that] actually absorbs CO2,” according to architect Wael Al Awar. Credit: Courtesy of National Pavilion UAE La Biennale Di Venezia/waiwai

Brine contains magnesium minerals. Kemal Celik, an assistant professor of civil and urban engineering at New York University Abu Dhabi and part of a team at the university’s AMBER Lab, extracted a magnesium compound from the liquid, and used it to make the cement.

Celik says the cement was cast into blocks, which were then placed in a carbon dioxide chamber to set — an innovation which speeds up the production process. The cement was subjected to testing in the UAE before being sent to Japan, where blocks went through further strength and rigidity tests. In addition, an algorithm was developed to calculate how safe the blocks would be if used in construction, Mika Araki, a structural designer at the University of Tokyo, told CNN.

Precast blocks could be used to construct a single-story building “tomorrow,” says Al Awar, but he and Teramoto hope to develop the product further for use in multi-story buildings.

Al Awar claims their magnesium-based cement can “perform to the equivalent of Portland cement,” which uses calcium carbonate as a raw ingredient and is the most commonly used cement in concrete manufacture.

However, the magnesium cement has its limitations. As a salt-based product, it is liable to corrode steel reinforcement, he says, although reinforcement with other materials is possible.

Precast blocks of brine-based cement created by Al Awar, Teramoto and their academic collaborators.

Precast blocks of brine-based cement created by Al Awar, Teramoto and their academic collaborators. Credit: Courtesy National Pavilion UAE La Biennale di Venezia, photography by Sahil Abdul Latheef

Precast blocks are cured in a carbon dioxide chamber, as the cement requires a higher percentage of carbon dioxide to sufficiently harden than is contained in the atmosphere.

Precast blocks are cured in a carbon dioxide chamber, as the cement requires a higher percentage of carbon dioxide to sufficiently harden than is contained in the atmosphere. Credit: Courtesy National Pavilion UAE La Biennale di Venezia, photography by Dina Al Khatib

Professor John Provis is deputy head of the Department of Materials Science and Engineering at the UK’s University of Sheffield, and is unaffiliated with the project. He says the salt-based cement is “a really good idea,” explaining globally only a third of cement is used in reinforced concrete.

“These brines are a pain to dispose,” he adds. “They’re taking a local waste and doing cool things with it. I think it’s a really nice synergy there.”

Al Awar says he and Teramoto are motivated by a desire to construct more sustainable and ecologically friendly architecture. “Given CO2 emissions in the world and global warming, and all these alarms that have been ringing for many years, it’s our duty — it’s our responsibility — to take action,” he says.

Cement production is often energy-intensive and has a large carbon footprint. According to the International Energy Agency, the cement sector is the third-largest industrial energy consumer in the world and responsible for 7% of global carbon dioxide emissions. Celik says establishing their magnesium cement’s carbon footprint is part of an ongoing lifecycle study, which will compare it to ordinary Portland cement and other materials.
Kenichi Teramoto and Wael Al Awar, co-curators of the UAE National Pavilion at the Venice Biennale of Architecture.

Kenichi Teramoto and Wael Al Awar, co-curators of the UAE National Pavilion at the Venice Biennale of Architecture. Credit: Courtesy National Pavilion UAE

In May 2021, Al Awar and Teramoto will curate the UAE National Pavilion at the Venice Biennale of Architecture, where the alternative cement will go on display in their “Wetland” exhibition. The pavilion will be made from magnesium-based cement, although Celik says the cement will not be brine-based because they are not yet ready to scale-up production.

“The research is still early,” says Al Awar. “It should go through the natural process of experiments and trial and error to get somewhere. But we are very optimistic.”

Read the full article at: cnn.com