How long after concrete pouring is it appropriate to remove the formwork?

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Removing formwork isn’t based on the calendar; it depends on the strength of the structure. Removing it too early can cause the floor slabs to collapse, while removing it too late slows down the work process. Removal of the formwork: the span determines the timing, while strength is a critical factor. The formwork (at the bottom of beams and slabs) bears the load; removing it too early can be fatal. **Standard GB50204 provides clear regulations regarding the removal of formwork, with two key factors: span and strength. Span ≤ 2 meters: The structure can be dismantled once the concrete strength reaches 50% of the designed strength. Generally, it takes about 7 days at room temperature. 2 meters < span ≤ 8 meters: Strength must reach 75%. It takes about 14 days at room temperature, and the time increases in winter. Span > 8 meters: Strength must reach 100%. For such long-span structures, at least 28 days are required, and it is necessary for the test blocks cured under identical conditions to yield satisfactory results. Cantilevered components (balconies, canopies): Regardless of the span, they must reach 100% of their design strength before they can be removed. If something goes wrong with a cantilevered structure, it’s a serious issue – nothing can be done ahead of time. No need to remind: this “strength” is not estimated; it is determined through actual measurements of test blocks cured under the same conditions. The construction site should prepare several sets of test blocks in advance, place them together for natural curing, and then take them for compressive testing when the time is right; the resulting compression strength should be determined based on actual tests, rather than guessing. Removal of formwork on the sides: Since these elements do not bear weight, the formwork on the sides of columns, walls, and beams – which is not load-bearing – can be removed earlier. However, this cannot be done arbitrarily. Principle: The concrete surface and edges must not be damaged as a result of form removal. Under normal room temperature conditions, the side formwork can be removed 12–24 hours after pouring. But if the weather is cold, or the concrete takes longer to gain strength, wait a bit longer. In winter, sometimes it takes 48 hours. When removing the side formwork, touch it with your hand; if the edges are hard enough and won’t fall off, then it can be removed ； Dig a hole, and wait a bit more. Seasonal impact: In winter, it takes a few more days of keeping the structure covered; for a beam with a length of 8 meters, 15 days may be sufficient in summer, but over 20 days might be needed in winter. Because cement hydration is slow at low temperatures, the strength does not increase. The specifications do not specify how many extra days to add in winter; the correct approach is to use the strength of test blocks under identical conditions as a reference. Do an extra set in summer, and another extra set in winter; remove it once the intensity is reached, regardless of how many days have passed. Order of form removal: Remove the forms that were installed first before those installed later; those installed later should not be removed and then discarded carelessly. There are also rules for the sequence of formwork removal: remove the side formwork first, then the bottom formwork; remove the non-load-bearing elements first, and later the supports of the load-bearing beams. Start removing the formwork from the middle of the span before moving on to the ends. If the order is incorrect, the stress on the beams and slabs will change suddenly, which can lead to cracking or even collapse. ENDING form removal is not about rushing the schedule; it’s about ensuring safety. The formwork was removed too early, the floor collapsed, and all the hard work went to waste ； The formwork was removed too early, causing one corner of the column to get damaged; the cost of repairing it would be enough to buy several sets of formwork. What the project manager and supervisor need to do is not to urge the workers to \"hurry up and dismantle it\", but to control the strength of the test blocks. The strength report isn’t ready yet; no one is allowed to touch the formwork. Follow the rules when removing formwork to ensure structural safety.