What is Curing?
Curing is a crucial process in concrete treatment that aims to prevent the concrete from losing water too quickly and to maintain its moisture and temperature after the finishing process is completed. This is important to ensure that the concrete hardens properly and reaches the desired strength.
Why is Curing Important?
Curing is performed to allow the hydration reaction within the concrete mixture to occur optimally. This reaction is essential for achieving the expected strength and quality of the concrete. Additionally, curing prevents excessive shrinkage of the concrete due to rapid moisture loss, which can lead to surface cracks. The quality and duration of curing will affect several important aspects of concrete, such as:
- Concrete Strength: Better curing leads to stronger concrete.
- Structural Durability: Concrete becomes more durable.
- Water Tightness: Concrete becomes more water-resistant.
- Surface Resistance: Concrete becomes more resistant to wear.
- Volume Stability: Prevents concrete from shrinking or expanding excessively.
When is Curing Performed?
Curing is carried out immediately after the concrete enters the hardening phase, especially on exposed surfaces. For cast concrete, curing begins after the formwork is removed. The duration of curing varies depending on factors such as the type of cement used, weather conditions, and project specifications.
Curing Duration and Methods
The duration and method of curing depend on several factors, including:
- Type of Cement and Concrete: Including any additives used.
- Type and Size of Structure: The size of the structural elements being made.
- Weather Conditions: Temperature and humidity at the job site.
- Project Specifications: Expected time frame and compressive strength.
Several standards regulate the curing process:
- SNI 03-2847-2002: 7 days for normal concrete and 3 days for early high-strength concrete.
- ACI 318: Until at least 70% of the required compressive strength is achieved.
- ASTM C-150: Varies depending on the type of cement, for example:some text
- Type I Cement: 7 days
- Type II Cement: 10 days
- Type III Cement: 3 days
- Type IV or V Cement: 14 days
Common Curing Methods Used in the Field Include:
- Wetting the Concrete Surface: Periodically with water to keep it moist.
- Submerging the Concrete: By flooding the surface.
- Wrapping the Concrete: With materials that retain moisture, such as plastic.
- Covering the Concrete Surface: With materials that reduce water evaporation and are periodically moistened.
- Using Curing Compounds: Special materials for concrete care.
- In areas with low temperatures, curing is usually done using hot steam or heating blankets.
In addition to the standard curing duration and methods mentioned above, you should pay attention to the following do’s and don’ts:
- Maintain the concrete temperature during the curing process within the range of 10°C (50°F) minimum and 28°C (80°F) maximum.
- Ensure the curing process continues until at least 70% of the concrete’s compressive strength is achieved, which is typically recommended as the most common rule for various conditions and types of concrete by Planning/Design Consultants (i.e., the characteristic compressive strength, fc’).
- Ensure the concrete is regularly moistened. Inconsistent wet-dry cycles can reduce the quality of the concrete and increase the potential for cracks and decreased compressive strength.
By applying the correct methods and duration, your building structure will achieve maximum strength and stand firm for a long time.
