The general consensus among experts is that putting a curing blanket on set concrete may not be necessary or beneficial. By the time concrete sets, which typically occurs within 24 hours after placement, the hydration process is already well underway, and the concrete has developed sufficient strength to resist damage from drying out.
Benefits of Using Curing Blankets on Fresh Concrete
Using curing blankets on fresh concrete provides several advantages, including:
- Enhanced hydration: Curing blankets help to retain moisture within the concrete, allowing a more complete hydration process and ensuring optimal strength development.
- Reduced cracking: By preventing rapid moisture evaporation, curing blankets minimize the risk of surface cracking and ensure a more uniform and stable curing process.
- Improved durability: Proper curing with the help of blankets can increase the durability and long-term performance of the concrete, reducing the likelihood of future issues such as scaling or spalling.
- Accelerated strength gain: Maintaining a consistent temperature with curing blankets can expedite the concrete’s strength gain, allowing for earlier removal of formwork or reduced construction time.
Risks and Considerations
While the benefits of using curing blankets on fresh concrete are well-documented, there are potential risks and considerations associated with using them on set or hardened concrete. These include:
- Moisture retention: Applying a curing blanket to set concrete may result in excessive moisture being trapped within the concrete, leading to potential issues such as surface softening, reduced strength, or the development of efflorescence.
- Thermal stress: Placing a curing blanket on set concrete might cause an increase in temperature, leading to thermal stress and potential cracking. Hardened concrete has a lower resistance to thermal expansion, and sudden temperature changes can compromise its integrity.
- Oxygenation: Curing blankets restrict the airflow, which is necessary for the carbonation process to occur. Carbonation helps concrete gain additional strength and can be limited by the continuous use of curing blankets on set concrete.
Using a curing blanket on set or hardened concrete may not be necessary or advisable. Curing blankets are primarily designed for use on fresh concrete immediately after placement to enhance hydration and promote optimal strength development. While they provide significant benefits for fresh concrete, applying curing blankets to set or partially set concrete can lead to potential risks such as excessive moisture retention, thermal stress, and limitations on carbonation. It is crucial to consult with experts in concrete construction to determine the most appropriate curing method based on the concrete’s state and project requirements.