Award: ADALAC—Acoustically Diffuse & Absorbent Lightweight Aerated Concrete

“The researchers took a thorough approach in exploring the relationship between material and geometry in order to think about utilizing concrete differently in the industry.” —Juror Mónica Ponce de León, AIA

Anyone working in a minimalist, industrial office will likely attest that spaces filled with hard surfaces can quickly become echo chambers. Currently, concrete—planar, dense, and highly reflective of sound waves—is not the material of choice for acoustical mitigation. However, along with its inherent structural and thermal properties, concrete can be quite porous, not to mention amenable to experimentation with form. To test its noise-control capabilities, researchers at the University of Oklahoma (OU) are developing sawtooth panels made of acoustically diffuse and absorbent lightweight aerated concrete.

Designed for use on walls and ceilings, ADALAC panels can reflect, diffuse, and absorb sound frequencies related to everyday speech. Designers and manufacturers often address acoustical needs with materials that provide either absorption or diffusion, but not both, says Daniel Butko, AIA, associate professor of architecture at OU’s Christopher C. Gibbs College of Architecture. To enhance the porosity of the 20-inch-square, 6-inch-thick panels, Butko and his collaborators, which include Zachary Maggia, AIA, added a powdered aluminum admixture that reacts with the cement during hydration to create hydrogen gas bubbles. The sawtooth structure of the panels, with a subtle convex or concave geometry, was optimized through computational design with the aim of creating an economical, modular solution.

The team measured the panels’ sound absorption, reverberation times, and noise reduction capabilities in the laboratory. Covering 20% to 37% of a room’s wall or ceiling with ADALAC panels yields a 40% to 55% reduction in reverberation times in speech frequencies—at least double the performance of existing aerated precast wall panels on the market.

“Future research will explore utilizing recycled aluminum powder to reduce dependence upon new aluminum, replacing approximately 40% of the cement with fly ash, and developing a method of capturing or exchanging the excess heat created during hydration,” Butko says. He is currently pursuing additional grants and partnerships to further explore the panels’ viability in commercial markets.

Project Credits
Project: Acoustically Diffuse & Absorbent Lightweight Aerated Concrete (ADALAC), Norman, Okla.
Client/Owner: Daniel Butko, AIA (principal investigator, associate professor and Gibbs Research Fellow, The University of Oklahoma Gibbs College of Architecture)
Architect/Architect of Record: Daniel Butko
Acoustic Laboratories: Riverbank Acoustical Laboratories, Geneva, Ill. . Eric Wolfram, Malcolm Kelly, Marc Sciaky; Chesapeake Acoustic Research Institute, Upper Marlboro, Md. . Peter D’Antonio
Structural Engineer and Concrete Mix Consultant and Collaborator: Shideh Shadravan, OU Gibbs College of Architecture
Test Facilities and Materials: OU College of Engineering Fears Lab
General Contractor/Industry Partner (including collaborative fabrication and material supplier): Coreslab Structures, Inc., Oklahoma City . Coleman Harrison, Robert Shade, Stephen Breece, Brent Cosby (partnership and prototype fabrication)
Research Assistants: Zachary Maggia, AIA (acoustic measurements, modeling, and prototype development), Trevor Looney (concrete mix designs), Beau Buesing (concrete mix testing), Collin Abdallah (literature review and data collection), Lindsey Trout (modeling)
Acoustic Research Mentor: Robert Coffeen
Funding: OU Office of the Vice President for Research and Partnerships; OU Gibbs College of Architecture; Coreslab Structures; U.S. Formliner/Reckli, Athens, Ga.; Ashgrove Cement
Size (prototype panel): 20-inch-square by 6 inches

Materials and Sources
Cement: Ash Grove (Type I/II gray cement); Lehigh Hanson (Type I/II white cement)
Forms: U.S. Formliner/Reckli
Additives: BASF (MasterSet Delvo retarder and MasterGlenium 7500); Alpha Chemicals (30-micron aluminum)

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