September 8, 2015
An 80 lb bag of QUIKRETE® Concrete Mix yields 0.6 cubic feet of concrete when placed. For a slab that is 12 ft x 18 ft x 0.33 ft (4 inch), 72 cubic feet of concrete, or 120 80 lb bags of Concrete Mix will be required. For a slab that is 12 ft x 16 ft x 0.33 ft (4 inch), 64 cubic feet of concrete, or 107 80 lb bags of Concrete Mix will be required. If the 12 ft x 18 ft slab is actually intended to be 4 ft thick as described, it would require 864 cubic feet of concrete, or 1440 80 lb bags of Concrete Mix. If the slab is 12 ft x 16 and intended to be 4 ft thick as described, it would require 768 cubic feet of concrete, or 1280 80 lb bags of Concrete Mix. Yields will vary based upon waste, uneven subgrade, etc. For a job of this size, it will be crucial that you have sufficient equipment and man power to allow you to pour the entire application, or sections that are separated by expansion joints, before any of the material in that section has set. If some of the material sets before subsequent bags are poured, a cold joint will form. A cold joint is caused by the inability of the product to intermix between bags, and prevents the slab from being a single, solid mass. A cold joint may cause problems ranging from a simple aesthetic issue, to as serious as potentially allowing for water intrusion into the cold joint, which may eventually lead to concrete degradation. Be sure to check local building codes to ensure compliance. If you would like to discuss, please call the QUIKRETE® Technical Center directly at 1-800-282-5828.
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