When pouring concrete forms on a job site, time is of the essence. If you need to get those forms to another site, you might wonder if there’s an issue with leaving them on for too short a period of time and compromising the build. On the other hand, you might also wonder if there are any issues with leaving concrete forms on too long. While the short answer is that, no, leaving concrete forms on for too long will not be an issue, there are things you want to consider about the whole process.
Concrete forms create a framework that supports the curing process, and the longer the forms stay in place, the more concrete will simply continue the curing process. If you are looking at concrete forms for sale, here’s what you need to know about the curing process and the length of time necessary.
When Should You Remove Concrete Forms?
Concrete forms are designed to provide structure and framework for concrete to cure. The curing process refers to the time period when concrete dries enough to become and remain solid. Concrete forms can also help make sure the concrete retains the appropriate amount of moisture during the curing process. You might be wondering how long to leave concrete forms in place and when you should remove them.
Concrete forms should only be removed once the concrete has dried enough so that it can support its own weight. The typical curing process for concrete takes between 24 and 48 hours, depending on the size and scope of the project. The type of concrete mixture and the area’s climate can also have an impact on how long you should leave concrete forms in place. The ideal time to remove concrete forms will depend on a variety of factors and will inform whether or not you leave concrete forms on for too long or remove them too early.
What Happens if Concrete Forms Stay Too Long or Removed Too Early?
Removing concrete forms is also referred to as strike-off or stripping the formwork. The removal process for concrete formwork should only take place once the concrete has gained sufficient strength. The determining factor for whether the concrete has gained sufficient strength is that the concrete should be able to handle twice the amount of stress that it would be subjected to once the forms have been stripped. The concrete framework provides temporary stability while the concrete cures, so if it is removed too soon, it can result in unstable concrete forms.
Important factors for concrete forms include both self-load and live-load features. Self-load for concrete forms refers to the pressure the concrete must maintain, while live load refers to the additional weight the concrete will support during both the construction and the finished project. If the concrete does not have sufficient time to cure, it can deflect that strength onto other places and compromise the integrity of the structure. If concrete forms are removed too early, the concrete may not gain enough strength sufficient for handling the required loads. However, you can’t leave concrete forms on too long in a way that would compromise the integrity of the structure and load-bearing process. When concrete forms stay on past the ideal curing process timeline, this simply allows more time for the concrete to cure. It is important to note that as you continue to pour more concrete, the concrete forms do deflect some load-bearing qualities during the curing process, so you must time those pours appropriately.
How Long Should Concrete Cure Before Removing Forms?
The standard timeframe for concrete curing is between 24 and 48 hours. The timeline will vary due to a variety of factors. Contractors can estimate the hardening of concrete and strength of concrete before removing the formwork through a testing process. You may choose to test on concrete cubes or cylinders before carrying out the process to help estimate the strength of concrete. Concrete cubes or cylinders used in the testing process should be prepared with the same exact mix of concrete as what will be used for the structural members and undergo the exact same curing process.
A test on concrete cubes or cylinders should also take place in the same circumstances as the upcoming curing process as much as possible. This should include the same circumstances around climate, including temperature and moisture, that will impact the structural member. Formworks should never be removed from the test product or the final product to ensure the structural members gain sufficient strength to withstand the intended load. While you can remove the concrete forms too early and impact the overall design, the concrete formworks can be left on even longer than originally intended and continue to help in the curing process.
Factors That Affect Concrete Form Removal Time
The striking time or stripping of the framework will depend on the strength of the structural member. There are many factors that will affect concrete form removal time and impact the strength and development of the concrete. Here are six factors that may be impacted by the concrete formwork striking times:
The temperature in the area will impact the timeline for concrete strengthening. In warmer weather and temperatures, the concrete is able to achieve higher strength in shorter periods of time. Conversely, in cold temperatures and winter months will prolong the strength gain time. Concrete forms help insulate the concrete from its surroundings, which can help support the rate of strength gain.
Concrete forms also help insulate the concrete curing process so that less moisture gets loss during the heat of hydration and evaporation. In extreme heat, there is a risk of excessive moisture loss, which can lead to cracking and spalling. Leaving on concrete forms for a longer time period can help prevent excess evaporation by trapping moisture while the concrete continues to cure at its intended strength.
The concrete mix will also have a significant impact on the formwork process, including drying and curing times. While some fast-setting concrete mixes are designed for load-bearing within hours, these mixes are typically ideal for small-scale projects. However, standard concrete mix will take much longer to dry and cure so it can support the necessary loads for a construction project.
The grade of concrete will also impact when the concrete gains its strength and during what time frame. For example, the higher the concrete grade, the shorter period of time it will take for the concrete to strengthen and cure.
The grade of cement impacts how much strength the cement can bear. The higher the cement grade, the shorter the time period it will take for the cement to achieve higher strength.
The size of the concrete member will also impact the gain of strength over time. Larger concrete sections will actually gain strength in a shorter period of time compared to smaller sections of concrete.
Final Thoughts: Why Should You Leave Formwork On & When to Strip It Off?
The longer you leave on the concrete forms, the more time you give the concrete to develop the sufficient strength necessary to support all types of loads that will be placed upon it. The general timeline runs from 24-48 hours, though you should take into consideration the factors listed above to ensure a strong final product. For both new and renovated concrete forms for sale, visit Forming America for a large inventory that allows for competitive pricing and quality customer service. Forming America offers concrete forms for sale and rent, and we can manage large quantity orders to help you meet your project’s deadlines. Visit us to address all your concrete forming equipment needs for your next project.