Voided concrete slabs enable new building to fit right in.
PROJECT VOIDED SLAB ACHIEVEMENTS:
Matched existing building with low floor-to-floor heights
Concrete Reduction: 639 cubic yards
Slab Reduction: 14” to 10”
F.A. Wilhelm Construction introduced an innovative voided concrete slab to create efficiency, both in construction and over the long-term in Seymour, Indiana’s new Schneck Medical Office Building.
The approach to pouring concrete foundations has, traditionally, been solidly set in stone. Not anymore – now its air. At the new Schneck Medical Office Building (Schneck MOB) in Seymour, IN, F.A. Wilhelm Construction (Wilhelm) is using a CobiaxUSA system, a revolutionary way to mold concrete around void forming modules cast from recyclable material and filled with air. The result is an eco-friendly, budget-friendly foundation with the same stability and stiffness gleaned from traditional methods, all while using less material and time to construct.
Designed by architect arcDESIGN and engineer Lynch, Harrison & Brumleve, Inc., Schneck MOB is set to be a five-floor structure requiring open space within the completed building. The use of a voided concrete slab enabled engineers to create a platform that utilizes fewer columns, yet still provides the amount of support needed to construct a sustainable building with more open space and larger spans between columns. As the first building in Indiana to use this technology, a few challenges were anticipated but Wilhelm counteracted with solutions. Prior to the Schneck MOB project, Wilhelm team members traveled to the Kennedy Center in Washington D.C. where Lane Construction employed the technology. The initial research on Wilhelm’s end led to seamless delivery at the Schneck MOB project.
The difference is in the pour
CobiaxUSA void systems differ from flat concrete, post-tensioned, and waffle slab decks and/or other deck variety pours in a multitude of ways. When pouring for this method, a mat of rebar is laid down followed by a cage of the voids, topped with another mat of rebar. Concrete is filled to just above the bottom wires of the cages that contain the voids and begins to harden around the bottom of the cages before the rest of the concrete, covering the void forms and the top layer of rebar, is poured. The first layer of concrete serves the purpose of holding the cages, preventing them from floating to the top while the remainder of the concrete is applied. The second layer forms around the voids without penetrating, breaking, or filling them.
Benefits and savings
The main benefit of this system is the smaller carbon footprint. The process of making cement emits carbon dioxide. With voided concrete slab technology, less cement and concrete (fewer concrete trucks) are used generating less carbon. Furthermore, the slabs are typically thinner than those structures that use alternate methods making the entire slab lighter. This allows for a decreased amount of support beams and more floor spaces.
In this application, the voided concrete slab is comparatively thinner than structures utilizing steel beams or beam and slab decks. These alternate methods result in greater depth due to the steel within the concrete. Where you might have a 10-inch slab with a CobiaxUSA system, other methods could have a 14- or 16-inch depth, resulting in a taller building. The shorter building enables owners to save on heating and cooling costs over the lifespan of the building. Further savings can be realized as there are no long-term maintenance issues with this system.
The voids are in the concrete, and they’re there forever, or until you take the building down. Then it’s just like anything else. There’s nothing different after the concrete is poured. There’s no maintenance issue, it’s a concrete slab. One of the benefits of concrete – it’s not going to rust on you. It’s pretty long lasting, or in today’s terminology, sustainable.
Lynch, Harrison & Brumleve, Inc.
F.A. Wilhelm Construction
Void area approximately 75% of each 16,500 square foot slab