Structural lightweight concrete offers many benefits, including better fire ratings, thinner slabs, smaller size structural members, improved seismic structural response, and lower foundations costs. The most obvious, however, may be reduced dead load. Structural lightweight concrete has strengths comparable to normalweight concrete, yet is typically 25% to 30% lighter. By utilizing structural lightweight concrete, designers have added more levels to buildings and parking structures at approximately the same loads.
The first major commercial project that made use of structural lightweight concrete was undertaken in 1928. The Southwestern Bell Telephone Company office in Kansas City, MO, was originally designed as a 14-story structure. Structural engineers determined that the foundation would support an additional eight floors, taking into account the additional dead load of conventional normalweight concrete. Structural analysis indicated that by using lightweight concrete rather than ordinary normalweight concrete, 14 floors could be safely added rather than eight, nearly doubling the above-ground height of the building and producing a skyscraper with a total of 28 floors. For almost 100 years, the reduced dead load of structural cast-in-place concrete and precast concrete made with rotary kiln expanded lightweight aggregate has made it possible to add additional levels to existing buildings and parking structures.
The original structure for the Union Station parking garage in Washington, D.C., was designed for a four-level vertical expansion. By utilizing lightweight concrete, the designer, THA Consulting, provided five levels at approximately the same vertical loads (Historic Union Station Garage Expansion – THA Consulting Website).
More recently, Sacred Heart Hospital in Pensacola, FL, added five new floors of patient care units with 112 private rooms. This vertical addition was constructed on top of the hospital’s existing three-story Heart and Vascular Institute raising the building to eight stories at a height of 220 feet. The structural engineer analyzed the existing steel-framed building and determined that it could support an additional five floors using structural lightweight concrete made with rotary kiln-produced structural lightweight aggregate (https://www.escsi.org/e-newsletter/sacred-heart-hospital-expansion/).
Build bigger projects without dramatically increasing the dead load when you use structural lightweight concrete. Connect with a producer to learn more about the benefits of this material for your next project.