How long before you can walk on it, drive on it, and load it? Set the average curing temperature and get estimated milestones — adjusted with the maturity method, because cold weather stretches every one of these out. These are planning estimates; engineered work must go by the specified strength.
Strength gain is logarithmic — fast early, then it flattens. 28 days is the reference for design strength.
Concrete doesn't "dry" — it cures through hydration, a chemical reaction that keeps building strength as long as moisture and warmth are present. At standard 70°F, it reaches about 70% of design strength in 7 days and its full design strength at 28 days. The curve is logarithmic: fast at first, then it flattens. That 28-day number is the reference used in specifications.
Hydration is temperature-driven. Warmer concrete cures faster; colder concrete much slower — what takes 7 days at 70°F can take 11–12 days at 50°F. Below 40°F you're in cold-weather concreting territory (ACI 306), and near freezing you must protect fresh concrete until it reaches about 500 psi or it can lose strength permanently. The opposite risk — hot weather — speeds hydration but raises the evaporation rate, which causes surface cracking. Read the full curing guide for methods that hold moisture in.
~70% of design strength in 7 days, full design strength at 28 days (at 70°F). It keeps gaining slowly for months, but 28 days is the spec reference. Cold weather stretches it out.
Usually 24–48 hours at normal temperatures — longer when it’s cold. Avoid dragging or heavy point loads until it has cured further.
Light vehicles after ~7 days (~70% strength). Wait the full 28 days for heavy vehicles, and defer to the specified strength on engineered work.
Yes — what takes 7 days at 70°F can take 11–12 days at 50°F. Below 40°F is ACI 306 cold-weather territory; near freezing, protect it until it reaches ~500 psi.
ACI 308: minimum 7 days for Type I concrete at ≥50°F (keep the surface wet/sealed). Type III high-early mixes need ~3 days. Longer is better for blended cements.