Howe much postage to send a postcard from US to Canada? As of September 2014, it costs $1.15 to ship a post card  internationally. If it exceeds 4 3/4 inches high or 9 1/4 inches  long, you will be charged the First Class Mail In â¦ ternational price. + 3 others found this useful.
Concrete is never truly done curing, but the minimum wait time should be 28 days. A slab typically cures at least 80% during that time. I suspect the manufacturer is asking you to proceed cautiously to avoid a lawsuit. If you (or your client) can wait that long, then wait the 120 (or more) days. But I wouldn't put any flooring on it inside a month.
Concrete will never fully cure; it continually hardens forever, although for all practical purposes, it reaches a point where further hardening will be so slow as to unnoticeable. Unless the mix has retarder (or some cement replacement material) in it, it will generally be hard enough to walk on in less than 24 hours. Mixes are usually specified with a design strength - the compressive strength that the concrete will reach in a period of time, typically 28 days. As a general rule, at 7 days it will have reached around two thirds to three quarters of the design strength. Don't worry about the water on the new concrete - it will help the concrete cure if it is kept damp after the initial set. The early stages of concrete curing is the hydration of the cement in the concrete.