What Happens When It Rains on Wet Concrete?

When it comes to pouring concrete, unpredictable weather conditions can pose a significant challenge. One of the most common weather-related concerns is rain. The sudden downpour on freshly placed concrete can harm its strength and appearance.

In this article, we will explore the effects of rain on freshly placed concrete and provide tips on mitigating potential damage.

Understanding the Role of Water in Concrete

Before we delve into the impact of rain on freshly placed concrete, it’s essential to understand the role of water in the concrete mixing process. Water is a crucial component in concrete as it hydrates the cement, allowing it to gain strength and form a solid structure. However, additional water, such as rainwater, can have adverse effects once the concrete is placed.


The Negative Impact of Rain on Concrete

Rainfall during the curing process of concrete can compromise its strength and durability. Here are some of the potential negative effects of rain on freshly placed concrete:

  1. Reduced Surface Strength: Heavy rain can wash away the cement paste on the surface of the concrete, leading to a weaker top layer. This can result in decreased abrasion resistance and increased susceptibility to cracking and dusting.
  2. Surface Defects: Rainwater can cause surface defects such as scaling and spalling, where the top layer of the concrete starts to flake off. These defects not only compromise the appearance of the concrete but also its structural integrity.

  3. Extended Curing Time: Excessive rain can prolong the curing time of concrete. The constant exposure to moisture inhibits the drying process, delaying the attainment of full strength. This can lead to project delays and increased costs.

  4. Poor Finish Quality: Rain can disrupt the finishing process of concrete, making it challenging to achieve a smooth and uniform surface. The water can cause the aggregate to displace, resulting in an uneven finish.

Tips for Dealing with Rain During Concrete Pouring

While it’s ideal to avoid pouring concrete during rainy weather, sometimes it’s unavoidable. Here are some tips to minimize the negative impact of rain on freshly placed concrete:

  1. Weather Forecasting: Stay updated with weather forecasts to anticipate rain. Plan your concrete pouring schedule accordingly, avoiding days with a high chance of precipitation.

  2. Cover the Work Area: If rain is expected, cover the freshly placed concrete with waterproof tarps or plastic sheeting. Ensure that the edges are sealed to prevent rainwater from seeping underneath.
  3. Extra Preparation: Before pouring concrete, inspect the jobsite for proper drainage. Ensure that gutters and downspouts are directing water away from the work area to prevent excessive water accumulation.

  4. Monitor the Weather: During the concrete pouring process, constantly monitor the weather conditions. If rain starts to fall, take immediate action to protect the concrete, such as covering it with tarps or pausing the pouring process temporarily.
  5. Finishing after Rain: If rain occurs during the finishing process, avoid working the rainwater into the concrete surface. Instead, use a float to push the water off the edge of the slab before continuing with the finishing.

Assessing Rain Damage and Remediation

In the unfortunate event that rain has caused damage to freshly placed concrete, it’s crucial to assess the extent of the damage and take appropriate remedial measures. Here’s what you need to do:

  1. Surface Inspection: Examine the concrete surface for defects such as scaling, spalling, or cracking. Take note of the severity and location of the damage.
  2. Consult a Professional: If the damage is significant, consult a concrete professional or structural engineer to assess the structural integrity of the concrete and provide guidance on necessary repairs.

  3. Repair Options: Depending on the extent of the damage, various repair options may be considered, such as patching, resurfacing, or applying protective coatings. Consult with a professional to determine the most suitable repair method.

  4. Prevent Future Damage: Once the repairs are complete, take preventive measures to avoid future rain damage. This can include improving drainage systems, applying sealants or waterproof coatings, and implementing proper maintenance practices.


Rain can have a significant impact on freshly placed concrete, compromising its strength, durability, and appearance. It’s crucial to plan concrete pouring around favorable weather conditions to minimize the risk of rain damage. However, if rain is unavoidable, taking proactive measures to protect the concrete and addressing any damage promptly can help mitigate the negative effects. By understanding the potential risks and implementing appropriate strategies, you can ensure the longevity and integrity of your concrete projects.