Imagine a museum with exposed concrete walls up to 70-feet tall, a building skin made of locally-harvested rock and copper products, a roof growing nativeseeded plants and a parking lot designed to recharge water runoff and release it back into the ground. You’re not imagining things. Designed to match the unique landscape and culture of Utah, the 165,000 square-foot Utah Museum of Natural History perched on the 17-acre hillside of Red Butte Gardens on the University of Utah campus is a building as striking as its contents and surroundings.The very walls of the building feature large amounts of architecturally-exposed concrete, a testament to local scientific innovation and the recycling of Utah’s own local natural resources.
According to Lou Nicoletti, quality control manager for Jack B. Parson Companies, the initial project specifications called for slag cement due to its white color and recycled content value.
“We knew that the best choice for this project would be a mix not only with slag cement, but a self-consolidating mix,” says Nicoletti. But, no other ready-mix company in Utah had developed a self-consolidating mix that contained slag cement. The experts at Jack B. Parson Companies, one of the region’s largest suppliers of construction materials and services, stepped up to this challenge.
Jack B. Parson Companies, structural engineer Dunn Associates and general contractor Big-D Construction collaborated to design the innovative self-consolidating 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, with walls in excess of 65-feet tall and heavily congested reinforcing steel.
“There are many unique structural features that could not have been achieved using a conventional concrete mix,” Nicoletti says. “We enhanced the originally prescribed mix by incorporating slag cement and Class F fly ash to improve flowability and architectural appeal. The finished concrete mirrors the unique board forming system desired for this project. In the end, the self-consolidating mix was brighter, more aesthetically pleasing and became a vital component of the structural and architectural success of the building.”
Another challenge Big-D faced was how to consolidate the concrete. If consolidation of the concrete was to be achieved by using the standard vibration method, the architectural appearance of the concrete would have been compromised by showing pour lines, and the concrete would have ended up having a mottled or striped appearance. Staker Parson, in cooperation with Big-D Construction, decided a self-consolidating concrete mix would be the best concrete mix to use to meet the project specifications regarding LEED Gold Standard and architectural requirements of this project.
Ron Dunn, owner of Dunn Associates, reports that while the unique self-consolidating concrete mix presented many construction challenges, the results are incredible. “The concrete work is quite exquisite,” he says.
Despite containing only 300 pounds of Portland cement in the mix design, the concrete has proven its strength in hundreds of strength tests, boasting over a 9,000 PSI 28 day average. And while hydration stabilizers were used in combination with the slag cement which typically will prolong the set time of the concrete, the contractor was able to strip forms off within 12 hours after pouring in winter, spring, summer and fall. This was achieved by making slight adjustments to the superplasticizer and using small amounts of non-chloride accelerator in cold weather. All this was done without sacrificing the architectural color or appearance of the concrete.
The building will also include pervious concrete pavement in the parking lot, allowing the owner to take advantage of several additional LEED points.Using the pervious pavement system allows water to filter through the pavement and into a detention bed made of washed stone, placing water back into the ground or as the case is with this project, the water in the detention bed is being utilized to water the landscaping vegetation on site, as well as vegetation across the street at Red Butte Gardens.
The museum is divided into three main buildings.The North building houses administrative offices, lab space, high density storage for artifacts and other museum exhibits.The South building features the public exhibit space. Native Voices is a building dedicated to honoring the Native American tribes of the region.
The buildings are separated by an expansive feature called Canyon. Bridges connect the buildings at the third and fourth floor, spanning Canyon at up to 40-feet wide. It is while crossing Canyon that visitors forget they’re in a museum and truly feel the inspiration of nature. A large concrete boulder juts out while the exposed board-form faceted concrete mass cantilevers from the wall. Structural elements that are normally covered up are exposed in an artistically beautiful way.
Not only is the building striking, it’s sustainable. The museum will be one of the largest buildings in the Salt Lake Valley to receive the Gold LEED Designation.
“Aggressive and creative design and optimization of construction materials allowed the main superstructure to be designed utilizing less material,” says Dunn. “The building is sustainable: designed and built based on lasting performance.”
The team of professionals on the project agrees that team work has greatly contributed to the success of the project.
“Projects such as this demand collaboration and coordination between all professionals involved,” says Dunn. “We love architectural challenges and embrace the opportunity to show our talents. It is very rewarding to be aligned with a fun and professional design team.”
Senior project manager for Big-D Construction, Leon Nelson, adds, “One of the most significant aspects of the project is the team work involved. The main participants on this project are located across the country, and everyone has done a great job of establishing a cooperative, problemsolving culture. We’re honored to be a part of this project.”
The new museum will open in the fall of 2011 and will house the museum’s 1.2-million-piece collection of rocks, fossils and artifacts. Polshek Partnership designed the unique structure, the Utah firm Gillies Stransky Brems Smith is architect of record, Maltbie is exhibit fabricator, and Ralph Appelbaum Associates is exhibit designer.
Ronald Dunn is the founder of Dunn Associates, Inc., a consulting structural engineering firm with regional, national and international experience. Scott W. Parson is the president of Oldcastle Materials Mountain West Division, the nation’s leading integrated supplier of rock products, ready-mixed concrete, asphalt, paving and construction services.