Concrete strength gain

Question: I just poured footings for a retaining/stem wall. The footings are 1' deep, 3' wide, and 36' long. How long should I leave the footing forms in place, and when can I put up the forms for the stem wall and pour it?? Thanks, B. Astoria, OR

In most cases, concrete is strong enough to maintain its shape after 24 hours. That means that an element supported by ground like the footings can be stripped after 24-48 hours. However, most people use low strength concrete for footings (2000 psi) and that may require a longer period to gain the strength you want. As a rule of thumb, concrete gains about 70% of design strength in 7 days (1400 psi for a 2000 psi concrete). That is strong enough to carry its own weight and more than enough for stripping. Bottom line: 48 hours should be ok. 7 days is long enough for any application.