Chip Plant Computes Waffle Slabs’ Structural, Aesthetic Advantages

Specifications for the 200,000-sq.-ft. clean room component of Texas Instruments’s new $3 billion semiconductor manufacturing facility in Richardson,

Specifications for the 200,000-sq.-ft. clean room component of Texas Instruments’s new $3 billion semiconductor manufacturing facility in Richardson, Texas, mandated strict indoor air quality and structural requirements. They were required to provide the demanding infrastructure to build the world’s most advanced semiconductors on 300-millimeter (12-in.-diameter) silicon wafers for a wide range of digital signal processing and analog-based system-on-chip devices for wireless, broadband and digital consumer applications.

With a late-2005 groundbreaking for the facility, the clean-zone architectural design Û by Alfonso Mercurio and Associates, Rome, Italy Û also raised the bar on aesthetic construction considerations. Key design elements had to be synergistically integrated within the massive design of the four-component manufacturing campus.

Since heavy equipment would be used in the structure, concrete flooring was necessary rather than the lighter-weight metal flooring specified for the administration building. Capform Construction Group of Carrollton, Texas, the projects’ concrete formwork subcontractor, specified fiberglass reinforced plastic (FRP) two-way joist system (i.e., waffle/pan/dome forms) to achieve the desired aesthetic and performance results required for the two concrete floor slabs on the main building’s clean-room design plan.

For the project, which was completed this spring, Capform rented approximately 8,000 waffle pans manufactured by Independence, Kan.-based Molded Fiber Glass Construction Products Co. (MFB), which reportedly maintains the world’s largest inventory of fiberglass-reinforced waffle forms. Each fiberglass-reinforced thermo-set composite form was 19 _ 19 in., 14 in. deep, and 24 in. center-to-center.

According to Lucky Gabriano, Capform’s field operations manager, MFG was selected because they could provide waffle pans that met the standard size, width and depth specifications for the job. Because we were able to rent standard forms and they were reusable, we were able to achieve substantial cost efficiencies when compared to custom forming.

Capform personnel built a deck frame treatment area and installed the two-way joist system according to the design plan. Steel rebar was then installed to sustain the concrete, which is then poured on top of a designated grid of waffle forms (i.e., domes, pans) and steel rebar joists. Ready mixed for the project was supplied by Irving, Texas-based Southern Star Concrete. Blow-holes built into the pan/joist grid system allow an air-compressor to pop or release the forms easily once the concrete sets. The result is a waffle effect.

Solid, closed-slab areas (covering the actual FRP waffle/pan forms) were poured in the main areas of the building where people would walk. Open-slab areas were poured in the middle of building where heavy equipment was placed, allowing air to flow from the first to second floors to facilitate circulation, which helps clean the wafers. The flooring is also raised on top of a grate so machines can efficiently move and clean air with no dirt getting into the wafers during production.

Juan Garza, Capform’s project superintendent, assesses the waffle effect, noting Once the pans are stripped from bottom, the pattern look provides the aesthetic benefit of having no crooked lines; they’re all parallel with the building design.

Adds Gabriano, The forms’ unique nature provided stronger structural deck, flexibility of open- and closed-area applications, and aesthetically pleasing results to complement the plant’s design.
Û Molded Fiber Glass Companies, 620/331-7366


Concrete slab area
500,000 sq. ft.

Waffle areas
150,000-sq.-ft. open waffle
120,000-sq.-ft. closed waffle

Number of pours
More than 57, with pours yielding 7,000 to 8,000 sq. ft. of slab area.

Mix set time
Two days to reach 75 percent of 4,000 psi design strength.

Approximately 30,000 sq. ft. of pans were used, with each pan used about 10 to 15 times throughout the project.

Construction window
Five months Û one month ahead of schedule.