Remove the forms before the concrete has completely dried. To guarantee that the concrete is entirely dry, the forms, or "molding," that hold the concrete in place while it cures, should be left alone for at least two days. Any wet concrete can become moldy if it's not removed within a few days.
Here are some reasons why you might want to remove the forms before the concrete sets fully:
If you plan to add color or texture to the surface of the concrete, you will need to do so while the concrete is still soft. The forms provide a barrier between the colored powder and the hardening concrete that would otherwise wear away the pigment or absorb the dye.
Concrete that has been formed into shapes requires time to cure before it can be painted or stained. The forms keep the concrete tight against the ground, preventing it from drying out and cracking.
If you want to add rebar or other elements before the concrete sets, you will need to do so while it's still soft. Rebar can be added to the mold before the concrete is poured to save time once the forms are taken down.
Finally, if you want to add heat to accelerate the curing process or move away from direct sunlight, you can use forms as shelter until the concrete is ready for more advanced treatment.
Keep the following timeframes in mind while waiting for concrete to dry: Forms may be deleted after the first set, and people can walk over the surface. Traffic from automobiles and equipment is safe 7 days after partial cure. The concrete should be entirely cured at this stage. At 10 days, you can walk on the surface, but it's best not to drive vehicles or conduct heavy machinery over it because these actions could damage the material.
At 14 days, the concrete is fully cured and durable. It can also be painted at this point without affecting its durability.
Concrete that is used inside buildings must completely cure before any hazardous materials are removed from it. This is so any residuals don't cause injury when workers enter those rooms. Curing takes about 28 days, depending on the temperature of the room and the type of cement used. Concrete that is exposed to direct sunlight requires more time to cure than that used in interior spaces.
The curing process will begin immediately if water is added to the mix. This occurs whenever concrete is poured into forms or onto a sub-base rather than being placed in a plastic bucket with no water allowed to enter the mixture. Curing slows down as soon as the water has been washed away because there are no longer any particles to keep the mixture active. Any moisture that does make it way into the concrete during this phase will cause it to go soft quickly.
Concrete normally takes 24 to 48 hours to dry sufficiently for walking or driving on. Concrete, on the other hand, dries in a continuous and fluid process, reaching full effective strength after roughly 28 days. Here are some fundamental facts about the drying period of concrete.
The amount of time it takes concrete to reach its maximum strength depends on several factors such as the type of cement used, its water content, temperature, and the size of the aggregate particles. Concrete that is mixed properly will be able to withstand traffic loads while it continues to harden. However, because this process can vary depending on the mix of your concrete, we recommend allowing samples of the concrete you plan to use for strength tests to cure for at least 7 days before testing.
Concrete sets within an hour under normal conditions. If it's raining when you pour the concrete, that will slow down the setting process significantly. At low temperatures, the concrete setting process may require more than one day to complete.
Concrete needs to reach its maximum strength as quickly as possible since over-mixed or under-mixed concrete tends to be weak areas in a structure. Structures with high levels of humidity will need additional time between batches to allow for proper drying between mixes.
Curing concrete also prevents the spread of disease via wet surfaces.
The water content of concrete at the end of this period is about 3% maximum.
The setting time will increase as more heat is applied to the mixture. Concrete sets when the hydration reaction reaches equilibrium. The overall rate of reaction can be increased by using an accelerator such as calcium chloride. The setting time can also be reduced by adding more water to the mix. However, this may not be possible due to limitations on the available water supply.
Concrete continues to harden as it cures, so work should be stopped as soon as it is feasible to do so. Concrete needs to cure for at least 24 hours before it is safe to walk on. Curing can continue for several more weeks after that.
When concrete has cured enough to be handled easily, it begins to shrink.
After the concrete is laid, the strength of the concrete grows rapidly over 3–7 days. Moist-cured concrete that has been moist-cured for seven days is about 50% stronger than uncured concrete. The growth in strength occurs because of a process called autogenous hardening. As the cement paste sets into a hardened mass, it produces small bubbles of carbon dioxide, which cause the concrete to swell and thus develop its strength.
Concrete's strength can be further increased by adding steel fibers or foam as additives. Steel fiber-reinforced concrete can reach a strength of 25 MPa after only three days, while normal concrete reaches its peak strength after one month.
The growth in strength comes at a price: The more moisture there is in the concrete, the faster it will grow. If the concrete is going to be used within seven days, it should be tested frequently to make sure it is still suitable. Concrete that is too weak to bear any weight becomes brittle and is likely to break when exposed to heat or cold temperatures.
Concrete's strength decreases over time as water moves into the concrete through cracks or pores in the surface. This water dissolves some of the calcium hydroxide in the cement, which reduces the concrete's ability to resist acid attacks.