Can You Pour Concrete In Rain?

Can you concrete in the rain? That is the question… It can be challenging to predict the weather, but you or the concrete contractor can take steps to keep your newly poured concrete at the pour site from being ruined by rain. It is a time when every precaution should be made – it is time for the “do it once and do it well” approach because the alternative outcomes are difficult to manage.

The final surface strength of concrete can be compromised when it is poured in the rain, so pouring concrete in the rain is not only unpleasant for those doing it, but can also lead to surface cracking on the concrete, which is a much bigger problem. 

Water is a crucial component of concrete, hydrating and strengthening it as it mixes with cement. It is much more harmful to freshly mixed concrete to be soaked by rain after it has been placed. The strength of concrete can be compromised by pouring it in the rain, increasing the risk of dusting and scaling in the future.

It can be difficult to rectify damage after the fact, and the finished surface will often look ruined. You can prevent and solve rain-damaged concrete problems by following these tips.

Pour Concrete In The Rain?

Pouring concrete in rain is far from ideal and adds a load of complexity to the project. Obviously, rain is best avoided altogether, and this is where a good professional concrete contractor will put the quality of the final job over just getting paid. A rain shower can suddenly arise without warning despite modern weather forecasting technology and radar maps, but on the day of the pour, check the weather forecast for obvious bad weather and moisture.

Concrete pours should be postponed if rain is forecast. Plastic sheets and tarpaulin should always be used to cover concrete work even if rain isn’t forecast. To prevent rainwater from seeping under, make sure you seal the edge of the slab well. You must keep water off the edge because that is the entry point.

Be sure to check the jobsite for potential wet surfaces if it rains. Inspect for the location of gutters and downspouts before the work begins. If the slab is directly beneath the overflow from a downspout or roof without gutters, rainwater will cut a trench into wet concrete.

Never pour concrete into water-filled cavities, as the water will be absorbed by the concrete, thereby weakening and causing damage to the concrete.

Affect Of Rain On Fresh Concrete

In the case of concrete pours that are not yet finished and have not had enough time to cure, heavy rain can be concerning. 

If the concrete is not yet dry, the water can cause it to crack and crumble by affecting the concrete mix at the surface. It is important to protect concrete that is still curing from heavy rain, so that it can reach its full strength.

Tips For Pouring Concrete And Handling Rain 

As for what to do if it pours down on your newly placed concrete:

  • The biggest mistake you can make is to work the rainwater into the concrete surface.
  • You should not broadcast dry cement on the concrete as a way to soak up surface water. It will further weaken the top layer and impair the finish.
  • You do not want the water to mix into the concrete or the concrete to soak the rain into the surface. You should instead push the water off the slab’s edge using a float once the rain passes.

How Long Does Concrete Take to Dry Before It Is Safe From Rain?

The potential for damage may not be extreme even if rain begins to fall after a concrete pour. Rainwater may cause little damage if you had enough time to finish your concrete and it has had sufficient time to stiffen. This is typically 4 to 8 hours after initial mixing.

It is actually beneficial for concrete to have water on the surface after it sets, since it assists in hydration during the curing process. In order to assess the integrity of the surface and determine whether the rain had an impact, a scratch test can be performed using a screwdriver or Mohs concrete surface hardness scratch test kit.

Solutions for Rain-Damaged Concrete

During or shortly after the placement of concrete, rain can weaken the surface strength of the concrete, resulting in surface scaling or spalling.

The rain will wash some cement from freshly poured concrete at the surface if the worst happens and the skies open up on you.

This is likely to lead to problems such as:

  • Dusting
  • Scaling of the surface
  • Craze cracking – this is worsened by cycles of freeze-thaw
  • The pouring of integrally colored concrete can also cause streaking if rain washes out some of the color.

Resurfacing the concrete with an overlay after checking that the underlying concrete is structurally sound is the best alternative to ripping out the concrete and starting over. A concrete overlay is a thin layer of new concrete that is applied over existing concrete. This method can be used to repair cracks and surface damage caused by rain during the pour.

Additional Problems Caused by Rain

If rain oversaturates the subgrade and causes ponding, it can have a detrimental effect even before you place a concrete slab. Fresh concrete can absorb the additional water and change the water-cement ratio as a result.

Prevent the ground from becoming saturated by covering it with plastic sheeting a day or two before the pour.

Also, rain can cause bubbles and blisters in freshly sealed concrete. When applying the sealer, make sure it is rain-free for 24 hours after application.

Importance Of Concrete Mix Ratio

Even if you don’t end up with any rain at all and you have a perfect pour, it is vital to get the concrete mix ratio right. If you are mixing your own cement, this will be more of an issue because you can’t just rely on the cement company to deliver an appropreatly designed concrete mix. Check out our dedicated article on the subject of concrete mix ratios here. On the subject of getting things right other than watching out for rain when you’re doing your own pour, it is also important to understand the issue of making sure you have the right gravel under your concrete


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