Pinnacle Cast Concrete, in Brownstown, Penn., completed initial load testing of a post tensioned concrete countertop. Born out of necessity, the project was created when a customer requested a 2 foot wide x 6 feet long x 2 inch thick clear span countertop that could hold a live load of 100 lbs. per square-foot without sagging or cracking.
Slab: 2 foot wide x 6 feet long x 2 inch thick. Initial camber = 1/8
According to Pinnacle Cast Concretes general manager Mark Celebuski, If we would have used conventional reinforcement the countertop would have deflected under load possibly cracking. There would also have been some long term creep issues as the slab sagged over time.
Final load: (3) drums, 1,395 lbs, 116.25 lbs/sq. ft. Measured deflection = 1/8
By using 10,000 psi concrete and high strength threaded rods we were able to introduce 18,000 lbs of force to the slab just below the center of gravity. We chose to post tension with treaded rods rather than cable so we could control initial camber and adjust the amount of force on the fly if necessary, Celebuski explained.
Additional load (3) drums, 1,395 lbs. + 400 lbs. additional live load in the form of 2 men jumping up and down. This opened several cracks in the slab which closed back up once the entire load was removed.
We were very satisfied with the results and are planning on testing post tensioned cantilevered countertops next, he said.
Test Specifics:
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Concrete: 28 day cylinder average = 10,500psi
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Slab: 2 foot wide x 6 feet long x 2 inch thick. Initial camber = 1/8
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Post Tension force applied: 9,000 lbs x (2) rods = 18,000 lbs. We lubricated the treads and used a torque wrench to establish the load on each bolt.
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Initial Load: (2) drums, 930 lbs, 77.5 lbs/sq. ft. Measured camber = 0
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Final load: (3) drums, 1,395 lbs, 116.25 lbs/sq. ft. Measured deflection = 1/8
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Additional load (3) drums, 1,395 lbs. + 400 lbs. additional live load in the form of 2 men jumping up and down. This opened several cracks in the slab which closed back up once the entire load was removed.
Pinnacle Cast Concrete
Mark Celebuski
Box 877
43 Industrial Dr
Brownstown, PA 17508
(717) 823-7408 Office
(717) 823-7409 Cell
(717) 859-4834 Fax
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