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Kingston,Mi | When I inspected USDA funded conservation practices, I would have reviewed Michigan construction practice std. 158, reinforced concrete. It has all of the items that I would observe and check of as having been completed correctly or need rework. Item 11 on the last page allows you to place or use heavy loads on concrete once it has reached 65% of design strength, 2 methods of determining this are allowed. The first is by breaking a cylinder of concrete prepared according to the appropriate ASTM testing standard and the second by observing the internal temp for a specified number of days.
Ed Boysun attached or included a graph of a typical strength curve and it shows the curve very near 65% at 7 days and above 80% at 14 days. We normally specified 3500 psi concrete with air for any job might experience freezing during its life span. We made cylinders at each of the training sessions we conducted as engineers and engineering technicians while training field office staff. Our results would fall along that general curve and most of our cylinders would break above 5000 psi with a 3500 specification at 28 days.
With good quality sub base, concrete and placement, I myself would not be afraid to start loading it at 14 days, light loads at 7 days. Attached is a link to the reinforced concrete construction specification, it has to meet American Concrete Association and Portland Concrete Association requirements or the Federal Government could not cost share. I am a trained and now retired NRCS civil engineering technician with specific training in concrete construction, inspection and had,when employed, approval authority equal to many licensed civil engineers.
www.nrcs.usda.gov/internet/FSE_DOCUMENTS/nrcs141p2_023436.pdf , this should open a search page in your browser , then open the pdf. | |
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How long to let concrete cure?
