Floating concrete? UNLV engineering students craft the perfect recipe

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They mixed the ingredients from scratch.

A little aggregate here, a little cement there, and just the right amount of H2O to craft a recipe to keep their boat afloat.

A concrete sea vessel, that is. The canoe – designed and built by UNLV civil engineering students – debuted and stayed above the waves of Lake Mead on April 15 at the 2022 American Society of Civil Engineers (ASCE) Symposium. Intermountain Southwest.

“Competition really puts our engineering skills to the ultimate test,” said Faith Greene, recent UNLV civil engineering graduate and captain of the concrete canoe team. “There are a lot of problems to solve in order to make the concrete light enough to mold the canoe into a shape that can float on water.”

UNLV students carry a concrete canoe out of Lake Mead during the competition. (Yasmina Chavez)

On a recent Friday morning at the lake, members of the UNLV concrete canoe team stood side by side with Greene to haul their boat out of its resting place on the beach and into the water for the first event of the day – the Women’s Slalom – a timed race through a series of buoys that tested the UNLV canoe against teams from nine other schools.

The regional conference, hosted by UNLV this year, brought together engineering students from the universities of Nevada, Arizona, Utah and Idaho to participate in a series of engineering-related events and attend career-focused workshops. The Concrete Canoe Races – a one-day affair at Lake Mead with both men’s and women’s rounds – was a highlight event and gave teams a chance to qualify for a national championship spot.

Moments before Greene and fellow paddler Kayla De Soto entered the water to compete, the team had worked tirelessly – with a bit of heavy-duty tape and Flex Seal – to repair two cracks that had appeared in the boat the day before the race.

Not only that, but the team trailer ran into technical difficulties on the way from UNLV to Lake Mead and a tire burst as well.

“All of this experience has shown us that we have to keep moving forward,” Greene said. “Just because something bad happened doesn’t mean it’s over.”

She was right.

As De Soto and other team members carried the canoe through the water alongside Greene, they took the lead from their captain.

“When I say ‘UN’, you shout ‘LV’,” Greene told his teammates.
“UN-LV, UN-LV,” they chanted as Greene and De Soto got into the water.

And then they did the same as Greene and De Soto rounded the last buoy and headed straight for shore.

UNLV’s participation in the annual symposium – outside of a hiatus due to the COVID-19 pandemic – goes back decades. The 2022 event, however, is the first time that some schools have competed in a new configuration of Mountain West universities, and the first time in over 10 years that UNLV has hosted the conference.

For the UNLV concrete canoe team, the postponement actually gave them half a canoe and a head start on this year’s competition. Before the pandemic put an end to the 2020 competition, the UNLV students had built half of their canoe, and this summer Greene and his fellow team members finished it and took it to the lake to test it.

“It was our practice round,” Greene said.

When the team received the competition rules last September for the 2022 symposium, they were a bit ahead of the ins and outs of making a lightweight concrete, but the canoe was no longer valid.

“We had to build an entirely new canoe from scratch,” said Tanner Richardson, co-captain and undergraduate civil engineering student. “That’s where the real challenge started.”

Teams were allowed three concrete mix designs and their canoe had to be built to certain dimensions. The UNLV team used only two concrete mix designs and additional flotation devices in the decks of the canoe for added buoyancy.

“Usually schools fill these sections with foam, bubble wrap, or just empty air just to help with flotation,” Greene said. “We probably didn’t need it, but we wanted to be safe. We didn’t want to fish it in Lake Mead.

The typical unit weight of concrete – the concrete that makes up sidewalks and roads – is 150 pounds per cubic foot. For water, it’s 62.4 pounds per cubic foot.

The UNLV team during the ASCE Concrete Canoe competition at Lake Mead. (Yasmina Chavez)

The UNLV team thought they had found the middle ground. Over several months, testing different configurations of coarse and finished aggregate, or rock, Portland cement, and water, they made a 60-pound-per-cubic-foot canoe.

“It’s just under the weight of the water – so it should be able to float,” Greene said Thursday, the day before the canoe’s trial.

And it worked.

That day, the concrete canoe team at UNLV – after facing unforeseen difficulties – persevered. They got into the water and kept their boat afloat.

“It was really good being on the water,” Greene said. “Overall, I think it was quite successful.”

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