Wetting new concrete is a common practice in construction that has been around for decades. Contractors often spray water over freshly poured concrete or cover it with wet burlap. The belief is that this extra moisture helps concrete fully hydrate and strengthen. But does wet curing new concrete really make it stronger compared to other curing methods? Let’s take a closer look at the evidence.
Why Concrete Needs to be Cured
After concrete is poured, it goes through a chemical process called hydration where the cement particles react with water to form calcium-silicate-hydrates, which provides strength and durability. Hydration is crucial for concrete to reach its full design strength. However, the hydration process won’t take place properly if the concrete dries out too quickly after pouring. This is why some method of curing is necessary to retain moisture in the concrete while it hydrates.
Benefits of Wet Curing
Wet curing provides concrete with a constant supply of external water. This keeps the concrete saturated so hydration can continue uninhibed. Some key benefits of wet curing include:
- Maximizes hydration since concrete has abundant moisture
- Reduces plastic shrinkage cracking
- Improves surface strength and abrasion resistance
Research has shown that wet-cured concrete often achieves higher compressive and flexural strengths compared to concrete cured by other methods. One study found 28-day compressive strengths were up to 18% higher for wet-cured cylinders compared to similar concrete cured with plastic sheeting.
Potential Drawbacks of Wet Curing
While wet curing has benefits, it also comes with some potential drawbacks:
- Can cool concrete temperature, slowing strength gain
- May lead to uneven moisture levels
- Can leach calcium hydroxide from surface
- Labor intensive for large projects
- Requires ready water supply
If water is applied unevenly or allowed to pool on the slab, it can create variable strength and increased shrinkage. And if the water temperature is too low, it may cool the concrete and slow the hydration reaction and setting. Proper wet curing requires monitoring to ensure even water distribution.
How Other Curing Methods Compare
Other common concrete curing methods include:
- Plastic sheets – Retain moisture but provide no additional curing water
- Curing compounds – Create a membrane to reduce moisture loss from surface
- Saturated mats – Absorb and retain water like wet burlap
Research suggests these methods generally provide good curing, but may not increase strength as much as wet curing in some cases. However, they are often more practical and controllable in the field.
| Curing Method | 28-day Strength | Cracking | Convenience |
|---|---|---|---|
| Wet Curing | Highest | Low | Labor intensive |
| Plastic Sheets | Slightly lower | Low | Convenient |
| Curing Compounds | Slightly lower | Moderate | Very convenient |
Conclusion
Based on a review of the evidence, wet curing generally provides a small increase in concrete strength and durability compared to other standard curing methods. However, the difference is often not substantial, and other techniques are typically more convenient and practical for construction sites. While wet curing has benefits, it may not be worth the extra effort and cost unless maximum strength is needed. Proper curing by any method is the most important factor for achieving good concrete quality.