JOINTLESS FEAT: MEGASLAB DEVELOPER SINCLAIR CONSTRUCTION SUBTRACTS SAW CUTS, ADDS VALUE.
Built adjacent to the manufacturer's Lawrenceville, Ga., home office, the warehouse harbors one of the largest slabs on grade--free of saw-cut control joints and expansive cement specs--to date. The 45,000-sq.-ft. facility and companion 12,000-sq.-ft. loading dock pavement mark commercial launch of the Megaslab Jointless Concrete System from Sinclair Construction Group, Marietta, Ga. The foundation, pavement and wall contractor credits the proprietary system's performance in large commercial projects to groundbreaking concrete technology; premium admixtures and fibers; plus, finishing methods that net dense, impermeable slabs. An absence of saw-cut control joints in the Megaslab template eliminates the prospects for spalling and perimeter curling common in conventional, maintenance-prone concrete slabs on grade.
"This a complete system of base preparation, mix design, slab engineering and finishing," says Sinclair CEO Jason Adams. "Megaslab has a very broad market potential considering the function of large slab on grade facilities, whose owners place a premium on low maintenance floors. As we have demonstrated on our first commercial installation of scale, Megaslab is even more unique among slabs promoted as 'jointless' due to its suitability for tilt-up concrete."
He cites a low maintenance, joint-optimized slab's value proposition for a variety of commercial or industrial facilities. In a typical warehouse, forklift tire traffic compromises joint integrity and spawns routine floor patching and repairs. In a food processing and packaging facility, on the other hand, sanitation is paramount; floor joint elimination reduces bacteria-supporting areas plus dust contamination attending maintenance schedules. Conventional reinforced, jointed concrete slabs also limit rack and robotic configurations in advanced distribution or manufacturing facilities' automated storage and retrieval systems (ASRS).
The Megaslab Jointless Concrete System signature version is designed for purpose with 4-in. topping slabs up to 22-in. depth for ASRS installations. The Megaslab EL (Elevated) version suits placement on metal decks plus elevated slabs with conventional rebar and post tensioning. Sinclair has begun promoting the value-added system for its own contract work and under licensing terms with peers who can demonstrate competence in precise slab placement and finishing methods, and source ready mixed concrete with requisite quality assurance and control. Measured against conventional concrete slab practice, Megaslab mixes and surface-hardening techniques yield a robust surface much less prone to dusting--a condition receiving greater scrutiny in light of crystalline silica exposure monitoring in workplaces. The mix design is formulated to account for local material variety from coast to coast. In comparison to common conventional slab on grade mixes, it exhibits higher compressive, flexural and tensile strength properties.
PILOT SITE CONDITIONS: CHALLENGING BY DESIGN
Leading into Megaslab commercialization efforts this year, Sinclair placed a test section at the Warren CAT Lubbock repair shop. The West Texas Caterpillar dealer subjected the slab to an aggressive, 87,000-lb. load: A D8T dozer continually running on a zero radius turn pattern to test surface integrity. While the machine made removable scuff marks, it did not chip or spall the concrete.
The Foundation Technologies site presented less aggressive surface, but more critical placement and site condition testing. A late-2018 schedule for the loading dock pavement enabled crews to measure concrete mix properties and finishing potential under less than optimal conditions. The larger warehouse slab placement three months later offered up similar damp, cool weather to prove mix design and placement adaptability.
The latter slab has a single transverse construction joint dividing 182-ft. and 166-ft. sections, each 130-ft. wide. It uses Sinclair's optional Armor joint, shaped like a sine wave and formed with two pieces of 1/8-in. thick steel, 6 inches deep. The Armor joint wave pattern eliminates the potential for slab damage associated with conventional straight joint cuts, which are subject to impact at 90-degree angles from wheels or attachments on forklifts or other industrial vehicles.
During Concrete Products' mid-Spring visit to the Foundation Technologies warehouse, more than a month ahead of the standing seam metal roof installation, the Armor joint conveyed slab thermal mechanics by opening widest at points least exposed to the sun. Subsequently, Jason Adams recalls, "We found that the entire joint would open at night due to cooler temperatures-cooler than the 'memory' temperature when the concrete set the day it was placed. Then it would close during the day when exposed to the sun. And when it would close, we measured only 1/8 inch of actual shrinkage over 348 feet. So when the joint was open, it was all due to lower temperature and not shrinkage."
The Megaslab Jointless Concrete System is equal to significantly more demanding conditions than its premier commercial installation. The Foundation Technologies site, however, affords Sinclair a good case for use with tilt-up concrete construction, where the slab on grade must be finished before the enclosure is erected. Projects involving precast concrete or concrete masonry walls, or metal building systems, typically see post-enclosure slab construction--the shelter affording a better concrete placing and finishing environment, plus greater schedule flexibility.
"The conditions at the Lawrenceville site were not ideal," Adams affirms. "We had very measurable rainfall leading into the spring season and were testing slab placement in an exposed setting. Many Megaslab candidate projects will have better conditions than what we encountered with Foundation Technologies."
The 6-in. thick warehouse and loading dock Megaslabs were placed with Somero 22EZ laser screeds and Whiteman riding trowels. Crews used bullfloats on early sections, but found the laser screed results alone sufficient for power troweling. Ready mixed concrete for the warehouse and dock pours was supplied from the Thomas Concrete Lawrenceville plant, where a small shop enabled Sinclair to stage Megaslab additive vessels and dosing. Beyond the Foundation Technologies warehouse, Sinclair has conferred with slab on grade practitioners and owners outside the Southeast, including state department of transportation representatives.
Teaming with Adams on Megaslab mix design and field practice guideline development is Sylvester Schmidt, a veteran of (pre-Cemex) RMC Industries, Atlanta, plus HeidelbergCement operations in North America and Europe. "I have always found joints and cracks, as well as other shrinkage related problems, to be a serious concern for industrial and commercial concrete floors," he says. "It's not only a cosmetic problem since joint maintenance and repairs are continuous cost factors for a facility owner. Megaslab presents a true, solid technical solution to these problems along with other substantial quality improvements."--Sinclair Construction Group, Marietta, Ga., www.megaslab.com
Caption: Jason Adams formed Sinclair Construction in 2012 as the Atlanta market showed strong signs of recovery. It was a natural step after nearly 15 years with one major and one smaller general contractor.
Caption: Sylvester Schmidt serves as Megaslab head of Technology, bringing the new venture a wealth of insight on cement and admixture technology, along with concrete practice.
Caption: The Foundation Technologies warehouse and loading dock made a good proving ground for the Megaslab constructability and performance. Sinclair Construction placed the loading dock pavement in late 2018 and the single-joint warehouse slab three months later. The ultra-smooth warehouse Megaslab, coupled with Nox-Crete bond breaker and curing compounds, fostered ideal wall casting and finishing conditions for T&M Tilt-Up Inc. The Bethlehem, Ga., contractor fabricated the 32-ft. high, 7.25-in. thick walls--totaling 27,200 square feet--over an early-2019 schedule.
Caption: STEALTH: A SURFACE IN SPACE
After establishing Sinclair Construction Group in the post-recession Atlanta market, founder Jason Adams sought a departure from commercial concrete work. He oversaw the principal casting elements--mainly hyperbolic paraboloid shells--of Stealth, a 36-ft. high monolithic sculpture in downtown Atlanta. The structure features precise edges, lustrous surfaces, and twisted forms, and is made of a black polished conventionally reinforced concrete with macro fibers. Stealth earned the American Concrete Institute Atlanta Chapter second place recognition in the Decorative category of ACI's 2016 Excellence in Concrete Construction Awards.
Caption: The warehouse nears a lengthy operating phase during which owner Foundation Technologies is assured of few if any disruptions tied to slab maintenance. Sinclair Construction has engineered the Armor joint as a Mega-slab option, demonstrating it along the full width of the 346--x 130-ft. warehouse enclosure. The Armor joint is shown here at a perimeter extension that ties the building slab and loading dock pavement. Sinclair Construction enlisted Atlanta market mainstay, Thomas Concrete, to supply proprietary Megaslab mixes. The producer's nearby Lawrenceville plant handled the Foundation Technologies slab and pavement pours.
Please Note: Illustration(s) are not available due to copyright restrictions.
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|Article Type:||Cover story|
|Date:||Jul 1, 2019|
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