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Low Shrinkage Concrete Joint Spacing

Low Shrinkage Concrete Joint Spacing

(OP)
I am working on a project in which a large portion of the first floor area will have a floor finish consisting of an exposed polished concrete slab on grade (6" thick). The goal is to maximize the control joint spacing as much as possible while still providing for the typical isolation joints around the columns. It seems that the best approach would be to use low shrinkage concrete or shrinkage compensating concrete to achieve this goal. However, I haven't found much literature on how to determine joint spacing using low shrinkage concrete.

I reviewed ACI 223, but unless I missed something, I didn't find any guidance in there. The columns are spaced at approximately 25 to 30 feet on center. The architect realizes that there needs to be control joints, they just don't want them to be 12 foot on center each way. They are hoping for spacing more like 30 feet.

Any advice would be appreciated.

RE: Low Shrinkage Concrete Joint Spacing

Not sure what would be appropriate in this case as I haven't looked at it. But ACI 360 probably as more information on this that you might find helpful. I usually use the charts in ACI 360 to determine joint spacing.

RE: Low Shrinkage Concrete Joint Spacing

I agree. ACI 360, "Design of Slabs on Ground" would be your best resource. Typically, your construction joint spacing is dependent on multiple variable such as Subgrade modulus (k), Loading (such a uniform, wall, post or wheel), dowel size and spacing, and the slab's temperature range. For a k value of 100pci and low loads (non-industrial) you can get joint spacings of 30 feet if you use adjust your controllable variables. Also, go to excelcalcs.com and check out "GRDSLAB" excel spreadsheet. That spreadsheet is great for slab on grade design. Most of the website's resources are free if you create account. Good luck.

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