Green is Keen: Utah Museum of Natural History includes innovative green concrete mix
The new building under construction for the Utah Museum of Natural History on the University of Utah campus in Salt Lake City is a green work in progress.
The 165,000-sq-ft museum, nestled in the hillside of a 17-acre lot bisected by the Bonneville Shoreline Trail, has a host of environmentally conscious building initiatives, including a pervious concrete parking lot and sidewalks, a building skin made of locally harvested copper and rock products, a wind turbine, and a roof with sections of native-seeded plants. The project is designed to inspire an appreciation for science and represent Utah’s magnificent natural history, landscape and future.
The walls of the building are being constructed with a one-of-a kind concrete that’s a testament to local scientific innovation and the recycling of Utah’s own local natural resources.
According to Will Hopkins, a principal for general contractor Big-D Construction of Salt Lake City, the initial project specifications called for slag cement due to its white color and recycled content value. The problem initially was no ready-mix company in Utah had developed a self-consolidating mix that contained slag cement. But experts at Jack B. Parson Cos. of Ogden stepped up to the challenge, designing an innovative, self-consolidating concrete mix that combines Portland cement, slag and Class F fly ash (a product recycled from coal-fired power plants).
Slag is a recycled material that comes as a byproduct from iron manufacturing. Its particle shape is more jagged than Portland cement particles, resulting in a less flowable mix. A fluid and flowable mix was especially important for the museum project because of the unique architecture of the building, which features walls more than 30 ft tall with high and congested reinforcing.
“We had to be innovative in our mix design,” says Lou Nicoletti, quality control manager for Jack B. Parson Companies. “We knew that the best choice for this project would be a self-consolidating mix. We enhanced the originally prescribed mix by incorporating Class F fly ash to improve flowability and architectural appeal. The finished concrete mirrors the unique board forming system required for this project. In the end, adding fly ash made the concrete lighter, brighter, and more aesthetically pleasing.”
Nicoletti reported that despite containing only 300 lb. of Portland cement in the mix design, the concrete has greatly exceeded its specified strength achieving a 10,000 PSI average. And, while hydration stabilizers – which typically prolong the set time of cement in concrete – have been added to the mix, workers have been able to strip forms in less than 12 hours after pouring.
Senior project manager for Big-D Construction, Leon Nelson, adds, “One of the most significant aspects of the project is the teamwork involved. The main participants on this project are located across the country and everyone has done a great job of establishing a cooperative, problem-solving culture.”
The new building for the museum, to be called The Rio Tinto Center, is scheduled to be one of the largest buildings in the Salt Lake Valley to receive LEED-Gold certification.
The building will be completed in fall 2011 and will house the museum’s 1.2-million-piece collection of rocks, fossils, and artifacts. Polshek Partnership designed the unique structure. Salt Lake-based GSBS Architects is the architect-of-record.