Unpredictable heavy rains and thunderstorms can cause massive damage to freshly poured concrete. A new concrete structure becomes soft with poor abrasion resistance and strength if there is excess water on its surface.
The chances are that cracks may appear on the exterior after drying.
Properly preparing the concrete mix and timing the pour is essential to prevent damage on freshly laid concrete surfaces.
Some contractors build protective enclosures around the work site using plastic sheets and wood. This helps prevent rainwater from collecting on the concrete surface.
If there is not much protection, it’s best to direct the water off the concrete surface before finishing.
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The concrete structure is not wholly damaged even if it starts raining soon after the pour. It all depends on the timing and the curing stage of the concrete. If the rain begins 2 to 4 hours after pouring the concrete, the surface should not be damaged.
Similarly, if it rains soon after the finishing stage, rainwater will not cause much damage if it does not seep into the surface. In situations where the concrete is ready for grinding and grooving, the rain will not cause any damage to the structure.
Either way, concrete takes between 24 and 48 hours to set and another 7 to 10 days to cure.
Contractors must assess the damage left on the surface after heavy rains. Visually evaluating the structure helps in detecting any defects or cracks.
In addition, scratching the surface with a sharp tool helps understand the surface’s hardness compared to other good-quality sections.
If the exterior of the concrete structure shows imperfection, repairs should be performed immediately. For damages on a thin slab, it is best to replace the entire structure.
Small cracks on a thick slab can be repaired by applying some mortar to the damaged areas.
Light sprinkles of rain can cause no damage to freshly prepared concrete structures. However, heavy rain showers and thunderstorms cause the surface to become soft and flaky. In such situations, use a plastic sheet for covering the surface or structure.
Assessing The Damage Caused To A Concrete Slab After A Heavy Rainstorm
As discussed earlier, visual inspections can help find defects and cracks in the concrete structure. Scratch testing is another effective way to find out the hardness of the concrete.
In most work sites, contractors make the mistake of not covering a freshly laid concrete surface before it rains.
If the rainfall is heavy, it may wash off cement from portions of the concrete surface. It will weaken the structure and also reduce its durability. Unsealed concrete surfaces absorb water and crack due to freeze and thaw cycles.
The most damaging effect of water is the scaling of concrete surfaces. It results in flaky layers and a pitted surface.
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Steps To Take to Fix A Rain-Damaged Concrete Slab
There are multiple ways of fixing concrete slabs, and it primarily depends on the final finishing and application of the concrete structure. Builders use concrete grinders to take off the damaged surface.
Usually, the damage is seen in the top 14th inch of the concrete surface, and it can be easily fixed with some grinding.
Grinding the powdery top surface of the concrete down to the dense concrete leaves a polished floor-like finish. After the grinding process is over, rinse the surface with water.
Is It Safe To Pour Concrete Over Existing Rain-Damaged Concrete Surfaces?
Yes, concrete can be applied to fix rain-damaged concrete surfaces using the following steps:
- The most important thing is to create a surface for proper addition. Hence, cleaning the surface is crucial
- Use a hard-bristled broom to remove the dirt and then pressure wash the surface for cleaning cracks and depressions.
- Use de-greasing products for removing tough stains and grease on the concrete exteriors.
- Then prime the concrete surface and paint it with a bonding adhesive.
- Pour freshly prepared concrete on the damaged areas and use a trowel for a smooth finish.
- The newly laid surface will be ready for use after 12 hours. However, it will take 7-10 days to gain its maximum strength.
Method Of Fixing A Crack In A Concrete Slab
The most common technique for fixing cracks in concrete slabs is widening the crack with a grinder. Then it is filled with mortar and a sealing compound. It will completely seal the crack and prevent water leakage or other materials from damaging the concrete.
After the mortar hardens, apply a coat of sealant and fill it with polyurethane for a perfect finish.
Pouring concrete in the rain also has several benefits. It mainly aids in the curing process; however, heavy rains just after pouring concrete washes off the top layers and affect structural strength.
Concrete Structures Don’t Dry; They Go Through A Curing Process
Usually, people say that concrete structures will be ready for use after drying. However, it goes through a curing process that results in chemical changes within the structure. Concrete can even cure underwater if favorable conditions exist.
However, pouring concrete in the rain is an entirely different story. The relationship between concrete and moisture is vital in understanding if you can pour concrete in the rain.
Setting And Curing Time Of Concrete
As we mentioned above, concrete takes between 24 and 48 hours to set and then another 7 to 10 days to cure. During this phase, moderate application of the structure is permitted. Avoid putting any heavy equipment on the concrete surface during this time.
This prevents any damage and facilitates proper curing. Complete curing of concrete structures may take around 28 days.
How Concrete Layers Are Poured In The Rain
Drainage ensures that the water flows into the trenches dug for foundation, slabs, and footing. However, rainwater is full of contaminants, so it’s best to drain it out properly instead of pouring it on the concrete surface.
Covering The Top Surfaces
Using plastic covers and tarps can protect small concrete slabs from heavy splashes of rain. Likewise, large areas can be protected with the help of covers and tarps.
Rain can cause significant problems with freshly prepared concrete. It can also delay the curing process due to the presence of excess moisture. Therefore, always keep in mind the above discussed precautionary measures to ensure that the rain does not affect a newly laid concrete structure.