Concrete curing is the process of maintaining adequate moisture in concrete within a proper temperature range in order to aid cement hydration at early ages. Hydration is the chemical reaction between cement and water that results in the formation of various chemicals contributing to setting and hardening. The hydration process is affected by the initial concrete temperature, the ambient air temperature, the dimensions of the concrete, and mix design. Therefore, for this process to progress well, in-situ concrete must have sufficient moisture and a temperature that favours this chemical reaction at a rapid and continuous rate.
The American Concrete Institute (ACI) recommends a minimum curing period corresponding to attaining 70% of the compressive strength of concrete. It is often specified that this can be achieved after seven days of curing.
Why Concrete Curing Is Important
Careful control of moisture and temperature of your in-situ concrete during curing is an essential part of quality control and quality assurance of your concrete structure. Proper curing techniques will prevent in-situ concrete from drying, shrinking, and/or cracking, and ultimately affecting the performance of your structure, particularly at the cover zone. Curing of concrete should occur as soon as it has been placed. It is also essential that continuous monitoring of concrete curing conditions be carried out for seven days. If water evaporates from the concrete before it has attained its maximum strength, there will not be enough water remaining in the concrete to fully hydrate the cement and achieve maximum compressive strength. This is especially true during extreme weather conditions, when your concrete slab is subjected to various environmental elements and strength development of your concrete can be compromised.
3 Techniques for Efficient Concrete Curing
Many factors affect the rate at which water evaporates from freshly placed concrete. This includes air temperature, humidity, concrete temperature, and wind speed. As a result, many techniques have been developed to help concrete retain moisture at the early ages. These methods are used to:
- Maintain the presence of water in the concrete during the early hardening period,
- Reduce the loss of water from the surface of the concrete, and
- Accelerate concrete strength gain by supplying heat and additional moisture.
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