Rain on Fresh Concrete: Pouring Concrete in Rain

Rain on Fresh Concrete

Rain on fresh concrete refers to precipitation that falls on newly poured and unset concrete. This can happen when concrete is exposed to rain or snowfall before it has had a chance to properly cure.

Rain on fresh concrete can have a number of negative effects on the finished product. If the concrete is not adequately protected, rainwater can seep into the surface of the concrete and alter its consistency, reducing its strength and durability.

Additionally, excess moisture can cause the surface of the concrete to become slick, making it more difficult to properly finish or texture the surface.

To prevent rain on fresh concrete, it is important to monitor weather conditions and take steps to protect the concrete from exposure to precipitation.

This can include using tarps or other coverings to shield the concrete from rain, as well as taking steps to improve drainage and minimize standing water in the area.

If rain does fall on fresh concrete, it is important to take steps to mitigate any potential damage. This may include carefully removing any standing water from the surface of the concrete, using drying agents or heaters to speed up the curing process, or consulting with a professional to determine the best course of action.

How Long After Pouring Concrete Can It Rain

If the concrete pouring is completed before 2-4 hours, It will be still fresh and unable to handle rain on it. So, Its surface must be covered to protect it from rain.

However, once the concrete has been finished and time elapsed between 4-8 hours after pouring and has been set hard enough to walk on it no footprint seen, then the effects of rain should be minimal.

How Can Rain Damaged Concrete?

One of the biggest problems occurred when pouring fresh concrete in the rain is that rainwater can potentially become mixed in the concrete, resulting in bleeding of concrete, laitance of concrete, and weaker overall finish of the concrete surface.

Water is an essential ingredient in the concrete mixing process and is carefully proportioned to guarantee the best result but adding more water than necessary will compromise the strength of the concrete mix, and means that your concrete is more at risk of cracking and also affects the ultimate strength of hardened concrete.

Ensuring that you’re ready to mix concrete is properly covered during the pouring process and afterward is therefore essential if you want to prevent permanent damage due to rainwater.

Rain can also affect the internal strength of the concrete. If there is constant heavy rain for a couple of days, the excess water on the concrete can slow down the curing process.

This can affect the internal bonds between the concrete particles and make the mixture weaker than intended.

Read More: Concrete To Water Ratio – Calculate Proper Amount Of Water For Concrete

How to Protect Concrete From Rain

It is important that you check the weather forecast before the placement of fresh concrete so that you aren’t caught short without the necessary equipment and are prepared to take precautions.

If another concrete is undertaking the installation of the ready-mix concrete on your behalf, you can ask them how they plan to prepare for the eventuality of rain.

1. If the weather is forecast for the day of the pour, you should cover your pour site effectively with plastic sheets and tarpaulin to ensure that the ground doesn’t become sodden.
2. Never pour concrete into water-filled cavities or onto very wet surfaces, as the concrete will absorb moisture and become compromised.
3. If you are pouring concrete following heavy rain, push any surface water off the edge of the slab.
4. If you are caught short, make sure you have plastic sheets and timber available to construct a temporary shelter to erect over the fresh concrete.

Effect of Rainwater on Concrete

We know very well that water is an important ingredient in concrete; however, it affects concrete strength if its quantity is used is more than that required, so the rainy season can be particularly hard because it brings water and wind.

Below mentioned are some bad effects of rain if the concrete is poured during the rainy season

1. Surface scaling

Due to rainfall, surface scaling on concrete surfaces can also happen. Surface scaling is a phenomenon where the surface of the concrete will become flaky.

Despite not being visible easily, it may break or crumble when you start putting significant weight by walking on it or storing your appliances and other goods.

This is something that must be restricted in order to keep the strength of the concrete last longer.

2. Segregation of Concrete Ingredients

Heavy rainfall can cause problems to freshly poured concrete as it can wash out some of the cement from the mix.

This can weaken the surface of the concrete, making it a sifter consistency and decreasing the strength of the concrete.

Read More: Honeycombing Of Concrete – Causes & Repair Methods

3. Higher Water/Cement Ratio

If the mix of the ingredients is unprotected, heavy rainfall will change the water-cement ratio in the mix.

This change in the ratio can cause the concrete to be easily poured but will damage the strength and durability of the concrete.

A mix like this will cause trouble in the future. It will be prone to cracks and can destroy all the effort put by you in making a mix and building up a strong building.

4. Lowering the Strength of Concrete

Rain falling on top of freshly laid concrete can damage the surface and compromise the level and floated finish of the concrete.

Even worse, if too much extra rainwater percolates into the concrete mix, this can result in weak concrete overall.

5. Affects on Curing of Concrete

Rainwater will affect concrete depending on the stage in the curing process that was reached before the rain set in.

if the concrete is still fresh (around 2-4 hrs after pouring), it’s important to cover the surface to protect it.

However, once the concrete has been finished (between 4-8 hrs after pouring), and has set enough for walking on, the effects of rain should be minimal. 

6. Deterioration of Concrete

Rainwater is composed of different chemicals from dissolved particulate materials in the atmosphere. Thus the composition of rain varies from place to place.

Human activities, industrial fission, local climate condition, and biome functions affect the type of particulates in the atmosphere, which in turn, affect the chemical composition of water.

When such rainwater gets in contact with concrete, it triggers a certain process (e.g., carbonation, acid, and sulfate reaction) that makes concrete vulnerable to deterioration.

Knowing this process and understanding the vulnerabilities of concrete will help you in detecting rain damage and minimize maintenance costs and repairs.

Read More: How To Make Concrete – Batching, Mixing, Transporting & Placing

How to Pour Concrete In Rain

Contractors need to keep an eye on their concrete structures during the rainy season. Rain might affect the surface appearance of the concrete as well as its internal strength.

When the concrete is between its initial setting time and final setting time, the rain can leave patch marks and pores in the wet concrete. This may be disturbing the uppermost layer of the concrete before it can cure properly.

Here are some points to be considered when pouring concrete in the rainy season.

1. Use Less Water in the Concrete Mixture During the Rainy Season

If you store your aggregates outside, the rain will make the sand and crushed stone wet. This will add extra water to the concrete mix, so remember to use less water when making a batch of concrete.

You will also need to keep an eye on your cement and ensure that no moisture gets into the bags while they are being stored. The cement needs to be stored in a dry environment at all times.

2. Use Waterproofing Admixtures in Your Concrete

During the rainy season, consider using hydrophilic crystalline admixtures in your concrete batch. These admixtures react with water and cement to form calcium silicate crystals.

The crystals block pores and micro-cracks in the concrete and prevent water from seeping into the structure. Essentially, they seal the concrete and protect it from excess water damage. 

3. Avoid Pouring Concrete During the Rainy Season

Make sure that the weather conditions are not too wet or windy before you decide to pour concrete. Keep an eye on the weather forecasts and try to find a gap of at least 12 hours where there is no rain. Fresh concrete needs about 12 hours to start the curing process and any rain could affect this.

The wind can also have a negative impact on the curing process. Strong winds can cause bleeding in the concrete and affect the evaporation rate of its internal moisture.

4. Weather Forecast Before Concreting

It is a well-known fact that rain can affect traffic on the road. This can create undesirable delays in the transportation and delivery of fresh concrete batches. Suppliers need to keep an eye on the weather and avoid making deliveries during the rain.

If this is not possible, then drivers should plan to use alternative routes with less traffic. Any delays in the placement of concrete reduce the workability which ultimately causes a reduction in the initial strength of the concrete. Delays in delivery will be costly to the project and will allow water to affect the construction site.

5. Use of Waterproof Covers to Protect Concrete from Rainwater

Plastic sheets and waterproofing canvas should be kept on-site during the rainy season. Once a concrete batch is poured, cover it with sheeting to shield the concrete from the rain. This will keep moisture in the concrete and keep excess water out.

Waterproof covers can also be used to protect aggregates and keep them dry. Using covers and traps will protect small slabs.

A self-leveling compound can be applied later if necessary to smoothen the surface. Tarps and covers can also be used for larger areas to good effect.

5. Good Drainage

This ensures no rainwater pools in trenches dug for footings, foundations, and slabs. This is important, as rainwater can bring with it contaminants. As long as it drains away there won’t be a problem with pouring concrete in the rain.

6. Perform Inspections After the Rain

Once the rain has subsided, asses the concrete and see if there is any damage or pools of water on the surface. A simple scratch test can be done to see if the surface of the concrete has been affected by the rain.

If there is any surface damage or dimples left by the rain on the concrete surface, contractors can use a float to remove excess pools of water and smooth the surface of the concrete at the same time.

The key to ensuring the success of a building during the rainy season is preparation. Be ready for heavy rains and have the right types of equipment and materials on hand to deal with the wind and water.

Pouring concrete in the rain is not advisable, rather stop and wait for the rain to pass and clear the atmosphere then remove the surface water in the foundations or on the already-poured concrete before completing the pouring concrete. 

Conclusion

In conclusion, rain on fresh concrete can have a number of negative effects on the finished product, including reduced strength and durability, altered consistency, and difficulty in finishing or texturing the surface.

Pouring concrete in the rain requires careful planning and preparation to ensure that the finished product meets the necessary standards of quality and safety.

To prevent rain on fresh concrete, it is important to monitor weather conditions and take steps to protect the concrete from exposure to precipitation.

This can include using tarps or other coverings to shield the concrete from rain, as well as taking steps to improve drainage and minimize standing water in the area.

If rain does fall on fresh concrete, it is important to take steps to mitigate any potential damage. This may include carefully removing any standing water from the surface of the concrete, using drying agents or heaters to speed up the curing process, or consulting with a professional to determine the best course of action.

Overall, pouring concrete in the rain requires careful attention to detail and adherence to best practices to ensure that the finished product meets the necessary standards of quality and durability.

By taking the appropriate precautions and responding quickly to any potential issues, it is possible to successfully pour concrete in a range of weather conditions and achieve a strong, durable finished product.

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