To ensure proper curing and retain moisture, concrete should be covered with plastic sheeting immediately after the concrete pour.
Covering newly poured concrete with plastic is a crucial step in the curing process. This method, often referred to as moist curing, helps prevent the rapid evaporation of water from the concrete mix. Maintaining adequate moisture is essential for the cement to fully hydrate and develop its intended strength and durability.
Timing is Key
As highlighted by the reference, the timing of applying plastic sheeting is critical:
- Immediately after the concrete pour: This is the primary recommendation to prevent the surface from drying out prematurely.
- The goal is to trap the existing moisture within the concrete.
Applying the plastic too late can result in surface cracking or reduced strength due to insufficient hydration.
Preparing the Surface
Before you lay down the plastic sheeting, it's important to prepare the concrete surface. The reference notes that you should:
- Ensure the surface is clean.
- Verify it is free from debris.
- Remove any excess water.
- Clear away any loose material.
A clean and properly prepared surface allows the plastic to sit correctly and effectively seal in the moisture.
Why Use Plastic Sheeting?
Using plastic sheeting for concrete curing offers several benefits:
- Moisture Retention: It acts as a barrier, preventing water from escaping the concrete, which is vital for continuous hydration.
- Consistent Temperature: It can help moderate temperature fluctuations, which is beneficial in various weather conditions.
- Protection: It protects the surface from external factors like rain, wind, and debris.
How to Apply Plastic Sheeting
Follow these general steps when covering concrete with plastic:
- Prepare the surface: Ensure it's clean and free of debris immediately after finishing the pour (as mentioned above).
- Unroll the plastic: Use durable, waterproof plastic sheeting (typically polyethylene).
- Cover completely: Ensure the entire concrete surface is covered, including the edges.
- Seal the edges: Secure the edges of the plastic sheeting using weights (like boards, rocks, or sand) to prevent wind from lifting it and allowing moisture to escape. Overlap seams by at least 6-12 inches if multiple sheets are needed.
Summary of Key Actions
Here's a quick look at the process:
| Action | Timing/Condition |
|---|---|
| Prepare the Surface | Immediately after finishing the pour |
| Cover with Plastic | Immediately after the concrete pour |
| Secure Edges & Overlaps | Immediately after covering the surface |
| Maintain Coverage | For the recommended curing period (e.g., 7 days) |
By covering the concrete with plastic sheeting immediately after pouring and ensuring the surface is properly prepared beforehand, you significantly enhance the concrete's ability to cure correctly, leading to a stronger and more durable finish.
