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Slabs on Grade

Extended Joints for Slabs on Grade.

Concrete slabs poured on a graded subgrade experience friction. Control joints are the industry standard to allow for expansion and contraction of the concrete slab. However, these joints can lead to an increase in curling, resulting in failure of the joint and unnecessary and expensive maintenance costs.   

The concrete industry continues to develop many practices and tools that reduce concrete shrinkage and the resulting cracks, but it still remains a challenge and a potential liability. Concrete joints and curling-related failure and damage are dramatically increased by forklift traffic in warehouses. They also create a tripping hazard for workers. Failed or “spalled” joints can also harbor bacteria and mold which is not tolerated in food or pharmaceutical environments.   

PREVent-C® is one of the only concrete admixtures that can provide volume stability to the concrete to defend against cracks. This allows contractors to extend the spacing between joints without the risk of dominant joints or the need for armor joints. Depending on the specific project, the joints can sometimes be eliminated altogether. In applications where jointing is difficult or poses other challenges – such as structural slab on grade construction or elevated concrete on metal decks – PREVent-C has been used as a solution. PREVent-C technology blends expansive components with pore water surface tension reduction. It has been proven to reduce shrinkage cracking by 90 to 100 percent, depending on the mix design and amount utilized.   

Fewer joints means less curling, cracking, maintenance, downtime, and costs. It also means an increased life expectancy for the structure. In a warehouse application, extending the joint spacing greatly reduces the impact from heavy equipment traffic. If a floor is being placed over the slab, joint elimination reduces shrinking and curling, which saves time needed for repairs and grinding if the slab experiences curling or high shrinkage. If the slab is exposed to exterior conditions, PREVent-C has the added benefits of reduced corrosion, and reduced water infiltration.  
Cracks are no longer an inevitable result when PREVent-C is chosen for a concrete slab. The following project stories show how.   

Control Joint Flat Slab Flow with Zero Cracking 
Intertape Polymer Group Inc. is one of the largest packaging industry companies in the world, creating protective solutions for industrial and retail use. In 2018, their manufacturing and distribution center in Danville, Virginia, undertook an expansion project that included the addition of a 120,000 square-foot 6” concrete slab. The original design had a standard 15’ x 15’ joint spacing with a 50’ x 60’ column line. Industry design standards with conventional materials require a joint every 15′ in each direction.   

Blair Construction proposed an extended joint spacing design that would match the column line. The concrete mix was optimized with PREVent-C Shrinkage Reducing/Compensating admixture and steel fiber allowing the concrete mix to extend further. The result was a 50’ x 60’ control joint design with zero cracking.   

Variable Joint Spacing with No Dominant Joints  
Blue Ridge Beverage Company, Inc., is one of the largest, full-service wholesale beverage distributors in Virginia. When the company built a 40,000 square-foot warehouse expansion at its Salem headquarters, the goal was to extend the joint spacing beyond the traditional 15’ to match the column lines. The columns had variable spacing, which resulted in joint spacing of 30’, 60’, and 70’.   

PREVent-C was selected as part of the solution because of its proven track record in extended joint applications. A 1-year site inspection after completion showed very good performance with no dominant joints.    

Flat and Level Continuous Pour with no Joints  
The University of Utah built a new basketball practice facility to house two basketball courts. Among other amenities, the basketball courts were to be high-quality wood flooring on top of a concrete slab on grade.   

With PREVent-C and 4 lbs/CY macro fibers, the entire 14,000 square-foot concrete slab was able to be poured continuously with no joints. The floor flatness (FF) and floor levelness (FL) numbers exceeded those required by specifications and no grinding was needed. Rick Hutchings, the Concrete Superintendent with Okland Construction, stated that throughout his 35+ years and many wood floors over concrete slabs, he had never had the flatness and absence of complaints from the wood floor installers like he experienced on this project.   

Put it to the Test 

Order a sample of PREVent-C, and schedule a trial mixture to evaluate its effectiveness on shrinkage cracking, as well as its effects on other fresh and hardened concrete properties. Or, send us your general questions about extending or eliminating joints. Contact PREVent-C experts today

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