Concrete that Floats – UNLV NewsCenter

Regional competition challenges schools to engineer concrete canoes, test them at Lake Mead.
UNLV engineering students compete in concrete canoe challege in Lake Mead during 2022 ASCE student competition. (Yasmina Chavez)
They mixed up the ingredients from scratch.
A little bit of aggregate here, a dash of cement there, and just the right amount of H2O to engineer a recipe to keep their boat afloat. 
A concrete, seafaring vessel, that is. The canoe — designed and built by UNLV civil engineering students — made its debut and stayed on top of the waves at Lake Mead on April 15 during the 2022 American Society of Civil Engineers (ASCE) Intermountain Southwest Symposium.
“The 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’s a lot of problem solving that goes into making concrete light enough, and molding the canoe into a shape that can be buoyant on the water.”
On a recent Friday morning out at the lake, members of the UNLV concrete canoe team stood shoulder-to-shoulder with Greene to lift their boat out of its resting spot 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 UNLV’s canoe against teams from nine other schools.
The regional conference, hosted by UNLV this year, brought together student engineers from Nevada, Arizona, Utah, and Idaho universities to compete in a series of engineering-related events and attend career-focused workshops. The concrete canoe races — an all-day affair at Lake Mead featuring both men’s and women’s heats — was a signature event, and gave teams a chance to qualify for a national championship berth.
Moments before Greene and fellow paddler Kayla De Soto got into the water to compete, the team had been working tirelessly — with a bit of heavy duty duct tape and Flex Seal — to mend two cracks that had appeared in the boat the evening prior to the race.
Not only that, but the team’s trailer encountered technical difficulties on the drive from UNLV to Lake Mead and a tire blew out, too.
“This whole experience has shown us to keep pushing along,” Greene said. “Just because something bad happened, doesn’t mean it’s done.”
She was right.
As De Soto and other members of the team carried the canoe into the water alongside Greene, they took their captain’s lead.
“When I say ‘UN,’ you scream, ‘LV,’” Greene told her teammates.
“UN-LV, UN-LV,” they chanted as Greene and De Soto got into the water.
And then they did the same when Greene and De Soto rounded the final buoy and made a beeline for the shore.
UNLV’s participation in the annual symposium – apart from a break due to the COVID-19 pandemic – goes back decades. The 2022 event, however, is the first time some of the schools have competed against each other in a new configuration of Mountain West universities, and the first time in more than 10 years that UNLV has hosted the conference.
For UNLV’s concrete canoe team, the postponement actually gave them half a canoe and a head start on this year’s competition. Before the pandemic put a halt on the 2020 competition, UNLV students had built half of their canoe, and this summer, Greene and her fellow team members finished it and took it out to the lake to test it out.
“That was our practice round,” Greene said.
When the team received the competition rules this past September for the 2022 symposium, they had a bit of a head start on the ins and outs of how to make a lightweight concrete, but the canoe was no longer valid.
“We had to make a full, brand-new canoe from scratch,” said Tanner Richardson, co-captain and a civil engineering undergrad. “That’s where the real challenge began.”
Teams were allowed three concrete mix designs and their canoe had to be constructed within certain dimensions. UNLV’s team used only two concrete mix designs, and additional flotation devices within the decks of the canoe for added buoyancy.
“Usually schools will fill those sections with foam, bubble wrap, or just empty air just to help with flotation,” Greene said. “We probably didn’t need to, but we wanted to be safe. We didn’t want to fish it out of Lake Mead.”
The unit weight for typical 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.
UNLV’s team thought they found the sweet spot. Over the course of several months, testing different configurations of coarse and finite aggregates, or rocks, portland cement, and water, they crafted a canoe that is 60 pounds per cubic foot.
“It’s right under the weight for water – so it should be able to float,” Greene said Thursday, the day before they put the canoe to the test.
And it worked.
On this day, UNLV’s concrete canoe team – after facing unforeseen difficulties – persevered. They took to the water and kept their boat afloat.
“It felt really good being out on the water,” Greene said. “All in all, I think this was pretty successful.”
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