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Concrete curing never actually stops, and the development of concrete strength continues over time. However, site engineers and contractors must know about the milestones of concrete strength development to understand when and how to proceed with the next construction stage.
The curing process is controlled by factors like ambient temperature, humidity, and moisture in the concrete. Nonetheless, the curing process should yield adequate strength within 2-3 days to withstand walking loads without showing footprints.
The design strength of concrete is usually attained after 28 days. Next, the curing process will continue, leading to increased concrete strength but at a slower pace.
How Long Does Concrete Take to Cure?
- The concrete curing process never stops, and the strength of concrete increases over time.
- It is safe to walk on concrete after 2-3 days from its placement, but it is recommended to use it after at least one week to avoid any possible damages due to loads of pedestrians or workers.
- The compressive strength of concrete increases quickly for 3-7 days but becomes gradual for the next three weeks.
- Concrete achieves about 70% of its compressive strength at the age of seven days.
- After one week from the initial concrete placement and under normal weather conditions, the concrete element can withstand construction loads of labor and machinery used for construction works.
- Concrete is considered to have reached its full strength at 28 days after placement. Nonetheless, the compressive strength increases afterward, but the rate of strength development decreases substantially.
- The strength developed roughly after one month does not necessarily benefit the structure because the required strength is already attained at 28 days.
- So, contractors can treat concrete as fully hardened after 28 days, and the concrete element serves its designated purpose.
- Environmental conditions influence the curing and strength development of concrete. For instance, hot weather conditions increase curing speed, whereas cold weather situations reduce the rate of the curing process.
- The hydration of cement slows down substantially or stops when the concrete temperature is below 5°C.
- Moisture in concrete plays a significant role in concrete strength development. Too much water may reduce concrete strength, and very little water makes concrete unworkable and difficult to place.
- Mix design of concrete is another factor that influences the curing process and strength development of concrete. If a contractor wants to cure concrete faster, they can introduce accelerated admixture to the concrete mix. However, the full strength of concrete may be slightly lesser than the concrete permitted to cure normally. For more information on how to increase the speed of concrete curing, please click here.
Fresh concrete sets after around 24 to 48 hours.
The concrete gains about 40% of its design strength after three days.
Concrete achieves around 65-70% of its designed compressive strength after seven days.
Improper curing of concrete leads to the reduction of compressive strength and durability. In addition, improper curing leads to the initiation of plastic shrinkage cracks and thermal cracks. To know more about improper concrete curing, please click here.