Eliminating Swirls in Precast Panels Massena NY

What can we do to eliminate swirls in precast panels? Sid Freedman of the Precast/Prestressed Concrete Institute says such swirls are signs of segregation caused by the placing method. Read on to know more.

Local Companies

Lowe's of Potsdam
315-268-6960
61 Country Lane Potsdam, NY, 13676
Potsdam, NY
Triple A Building Center
315-764-0596
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Massena, NY
W.l. Smith Hardware Corporation
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50 E Orvis St
Massena, NY
The Home Depot
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Massena, NY
Potsdam - Auth Hometown
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6586 State Highway 56
Potsdam, NY
Fastenal- Massena
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166 Harte Haven Plaza Massena, NY, 13662
Massena, NY
Evans & White Ace
(315) 265-4350
1 Maple St, opposite Trinity Episcopal Church on Fall Island
Potsdam, NY
Triple A Building Center
315-265-2350
6588 State Hwy 56
Potsdam, NY
Caswell True Value
(315) 388-5914
126 St Lawrence Avenue
Waddington, NY
Lowe's
(315) 268-6960
61 Country Lane
Potsdam, NY

Source: THE CONCRETE PRODUCER/CONCRETE JOURNAL MAGAZINE
Publication date: December 1, 1998

We produce precast exposed-aggregate sandwich panels using concrete made with Type III cement, a 0.38 water-cementitious materials ratio and enough superplasticizer to achieve a 7- to 8-inch slump. The forming bed is made of wood. Using a bucket that passes down the center of the bed, we pour enough concrete for a 3-inch-thick layer and rake the concrete to the edges. We consolidate that layer with an immersion vibrator, then screed it off before adding a 2-inch-thick insulation board and 3 more inches of concrete.When we sandblast the formed panel surface to expose the 1/2-inch limestone, the limestone particles appear in groups or swirls. What can we do to eliminate this problem?

Sid Freedman of the Precast/Prestressed Concrete Institute says such swirls are signs of segregation caused by the placing method. You should place concrete on top of concrete in successive bucket passes because blending separate puddles or passes of concrete creates areas that are heavy in mortar. Raking can cause a similar problem.Ed Boyle, plant manager at Lombard Architectural Precast, Alsip, Ill., suggests using a placing bucket with a wider-than-normal gate, then overlapping each successive pass to eliminate paste streaks.He also suggests using a vibrating screed that hangs off of the form side rails at the correct depth to consolidate your first layer of concrete.

Click here to read full article from The Concrete Producer