February 23, 2022 | Granger’s Self-Perform Construction Services division was honored to receive a 2022 Special Innovative – Structural Award from the Michigan Concrete Association for implementation of Michigan’s first-ever BubbleDeck™ Technology at the Western Michigan University (WMU) Student Center and Dining Facility. Director of Construction Services Jerrod Pung accepted this award on behalf of the team during a ceremony last week. Granger teams were partnered under Walbridge on this innovative project, and the new facility was designed by CannonDesign.
Western Michigan University’s vibrant and distinctive new Student Center and Dining Facility in Kalamazoo, MI is truly a unique structure combining state-of-the-art design with cutting edge construction techniques. The three-story, 165,000 SF building, located in the heart of campus, will open in Fall 2022 and offer a number of amenities, services and gathering spaces. The first two floors will contain most of the student-focused functions, while the third floor includes administrative office space and a full-service Dining Center.
Concrete Packages: Granger was selected by Wallbridge (CM) & WMU through a competitive bid process to perform both the structural and site concrete packages for this three-story building. The structural concrete package involved:
- Complex foundation design
- Over 10,000 cubic yards of concrete placed in 11 months
- 1,400 tons of rebar
- 90,000 SF of bubbles installed for the BubbleDeck™
- 115,000 SF of supported slabs
- 215,000 SF of flatwork placed and finished
This all occurred while maintaining an aggressive schedule despite poor soils that ended up getting undercut and replaced.
BubbleDeck Firsts: This project was the first building in Michigan and only the third in the U.S. to utilize the innovative BubbleDeck™ Technology for elevated concrete decks. This patented technique of linking air, steel and concrete in a two-way structural slab creates voids in the slab by using 12” hollow plastic balls in a grid formation. Each wire mesh grid section is prefabricated offsite and, once delivered to the project, put together like an intricate puzzle to construct the concrete decks.
Being the first-ever BubbleDeck project in Michigan and a rare technique industrywide meant the team had to overcome a pretty significant learning curve. Through extensive research, including visiting similar project sites and consulting with those teams, meticulous planning and spot-on execution, Granger crews were able to deliver this concrete package safely, on time and with excellent quality.
As a result of this alternative approach, which drastically reduces structural dead weight, WMU was able to incorporate more expansive, open interior spaces and greater column bay spacing into the design of this new, welcoming and engaging facility.
This project involved the use of a unique system or process to create concrete voided slabs or “bubble decks” supported by high-strength cast-in-place columns and walls. This BubbleDeck™ Technology is a patented system that makes floor slabs lighter and stronger by incorporating large, hollow plastic balls in a lattice of steel.
The process for this alternative approach starts with extensive upfront planning to sequence not only the concrete pours but also the procurement, fabrication, delivery and placement of the BubbleDeck panels and coordination of the various trade-to-trade handoffs.
A very brief description of the construction process for the BubbleDeck portion of the project includes:
- Shoring and forming of the supported decks.
- Installing the bottom mat of resteel on the plywood deck top.
- Using a crane to swing the prefabricated BubbleDeck panels into position on top of the resteel.
- Installing the top mat of resteel on top of the panels.
- Coordinating the installation of the inslab mechanical and electrical components.
- Resteel is inspected and a 3D scan is completed for record documenting as-built location of bubbles, rebar and MEP elements.
- Placing the bottom layer of concrete, consolidating it around and underneath the plastic balls and waiting for it to get hard before placing and finishing the top layer of concrete.
- Complete post-pour analyzer looking at metrics of the pour, which is then compared to the pre-pour analyzer.
Granger utilized two crawler cranes to lift the panels into place. Once in place and correctly positioned on the bottom layer of rebar, the panels are tied down and another layer of reinforcing rebar is installed on top. Deck pours began by placing the first of two layers of concrete – a unique and challenging aspect of this alternative technique. The initial 4” to 5” pass is referred to as a “duster slab” which is placed and allowed to set in order to keep the bubbles from floating to the slab surface. Then the balance of the slab was poured, creating elevated decks that were 15” thick.
Correctly consolidating the concrete around and underneath the plastic balls during the first layer was a major challenge on this project. Unfortunately, there is no “How-To” guide to follow because this is a fairly new technique in the U.S. If the right concrete mixture is not used and the right amount of vibration applied, it can create quality issues related to the aesthetics or finished look of the bottom of the deck. Meeting the specifications of the mix is also impacted depending on how it is being placed. Our team used a pump truck to place the concrete, which, due to the pressure needed, adds moisture into the aggregate and reduces slump.
The first pour had some minor issues that needed to be repaired, but the team learned from this and corrected the issues by working with the concrete supplier to test and slightly change the concrete mixture and also by creating a more detailed consolidation plan. As you would expect, each of these first layer pours were better than the last, resulting in excellent overall quality.
The WMU Student Center and Dining Hall project totaled 112,659 SF or 4,619 cubic yards of concrete, with 90,000 SF of that encompassing the BubbleDeck portion of the project.