Professionals gather to focus on concrete
They are focusing on reconstruction work in the wake of natural disasters like the recent earthquake in Chile. They are using the Cement Trust, founded by Bruce Christensen of McMinnville’s Cart-Away Concrete Systems, as their vehicle.
Luke Snell, a senior materials engineer at Western Technologies in Phoenix and chair of the American Concrete Institute, served as keynote speaker at the two-day gathering. He is considered one of the nation’s leading experts on concrete.
Snell said concrete is one of the most widely used building materials in the world. He said about 85 percent of new construction around the world features concrete, an amalgam of cement, sand, gravel and water.
But he said, “Around the world, nobody is inspecting the work. That’s especially true in housing.”
As a result, numerous shoddy buildings may get thrown up in the wake of a disaster — building that simply won’t hold up, rendering them unsafe. To address that, he has founded new ACI chapters in Mongolia, Algeria and Ethiopia, and new concrete certification programs in India, China, Taiwan and Saudi Arabia.
Snell said cement is widely used as a binding agent because it can be economically produced almost anywhere. He described how limestone and clay are combined and subjected to a heating process, the result being a heavy gray powder.
“We start to add water to cement, and there’s a magical process,” he said. “When water and cement react, they start to grow fingers. That’s what is gluing everything together.” The fingers that are grown through the process are what is providing the structure to give the concrete its strength.
However, the mix that would produce the maximum strength would be too thick to ever get out of the truck. Additional water must be introduced to make it workable.
But too much water has detrimental effects. That’s especially true in colder climates, where it could take a year for the resulting concrete to fully cure, and still produce a product lacking in strength.
“The amount of water we add determines what we do in the curing process,” Snell said. When enough water is introduced to create a soup-like mixture, structural strength will be very low.
In addition to bad mixes, theft and corruption can pose big problems. If five bags of cement are provided for a rebuilding effort, but three of them are diverted to the black market, it produces the same kind of unsafe and sub-standard result, he said.
Tom Vail, president and co-owner of Cart-Away, said that a century ago, the U.S. was making concrete structure the way the Third World is today — by hand, without scientific quality-assurance controls. “It’s going to take a team effort to make a difference,” he said.
“I see the Concrete Trust as a way to somehow focus attention on a complete solution,” Christensen said. “Start with rock and end with a successful disaster-resistant structure.”
Vail said the symposium went very well, producing a lot of good discussion. “I think we have some very good starting points,” he said.
But he said, “The end result is, nothing is as simple as it looks on the surface. To accomplish what we want to accomplish, it’s going to take a lot of time and effort.”
Vail said the group sees opportunities to test its theories in practice in Haiti and Nigeria. But he said their are lots of barriers, particularly when it comes to language and culture.
He said the Cement Trust will probably have to develop a picture-based manual for concrete-mixing to address the language problem. In Ethiopia alone, he said, more than 80 languages are spoken.