JUNE 2024CONSTRUCTIONBUSINESSREVIEW.COM9Collaborating with the designers, structural engineers, and concrete suppliers, we can change how the industry specifies lightweight concrete slabs to better interact with the down-line tradesIt is easy to overlook the finishing needs and flatness requirements with this sequence of specified materials and understand the consequences of the installation techniques required to achieve what is specified for installation. If we had finished the concrete as specified, with an FF35, we likely would create a path for floor failure.Offering Additional InsightsWe seldom see the consequences of how one trade affects another with regard to concrete finishing and floor installation. As a result, it is critical that this be one of the items reviewed during our quality pre-installation meetings.Through our quality program, associated processes, and coordination meetings, we have developed several strategies to address these concerns with the designer and installer. We now recommend the following changes to the specifications, which help to avoid the potential for a multi-million-dollar flooring disaster:1. Use normal-weight concrete if the structure and building fire design allow.2. If lightweight concrete is required (as noted in #1), reduce the floor flatness (FF) specifications to FF20, which could be achieved with a lighter finishing technique that will not create a weak top surface. The remainder of the flatness that is required for the flooring would be made up of a thin engineered floor topping.3. If lightweight concrete is required (as noted in #1), reduce the allowed air content in the concrete slab mix design. A concrete design of a 3 percent air content maximum will increase the overall weight of the concrete to about 2 PSF (pounds per square foot) for a 6" slab and maintain a 114 PCF (pounds per cubic foot) design rather than 110 PCF.Collaborating with the designers, structural engineers, and concrete suppliers, we can change how the industry specifies lightweight concrete slabs to better interact with the down-line trades. Going through the entire construction process, including discussing the next step of construction with the stakeholders, will educate and provide a better set of job-specific specifications that work for the initial to final installations. Putting together the down-line scenario and catching issues such as these before they become concerns is critical to a successful project. Having a quality program in place with an experienced team that can review the work before it commences benefits the project and all companies involved.
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