Why concrete cracks? Reasons and solutions explained!

Most buildings nowadays are constructed with concrete. And you might have noticed cracks here and there, be it inside your house or in commercial buildings. These concrete cracks don’t just look unsightly but can also impact the integrity of the building.

We can categorize the types of cracks in concrete into two types: non-structural cracks and structural cracks. While the first one doesn’t pose serious problems to the building’s structural integrity, the latter is more severe. Hence, it needs serious attention.

So, when should you worry about a craving? Why does it happen? And is there a way to stop it? This article shares insights on your concerns:

What is a concrete crack and what are the reasons behind them?

Concrete is one of the greatest innovations in the construction industry. It is a mixture of cement, water, and aggregates, like sand and gravel or crushed stone.

When mixed in the right ratio, concrete becomes hard, durable, and versatile. This texture makes it the perfect material for modern-day construction, including residential, commercial, and industrial projects.

However, even when you mix and apply concrete carefully, cracks can still occur, because of various reasons. Let’s take a look at the concrete cracks’ causes:

1. Shrinkage cracks

Shrinkage is one of the most common causes of cracking on the surface. It is a natural process. When the concrete dries, hardens, and loses its moisture, it starts to shrink.

However, concrete is inherently weaker in tension than in compression, which creates tensile stress. If the stress exceeds the tensile strength, it leads to cracks also known as plastic shrinkage cracks.

Even though these cracks are superficial and do not impact structural integrity, they need proper attention. It’s because these cracks allow moisture ingress and other environmental agents to penetrate the concrete, which can accelerate degradation.

2. Settlement and foundation-related cracks

These cracks appear when the soil can’t support the weight of the building. When the underlying soil shifts or consolidates unevenly after using the concrete, it leads to uneven support. Hence, the slab or foundation moves differently from one another, inducing tensile stress and cracking. These cracks are much larger and need immediate attention, or they may evolve into significant structural issues.

3. Temperature-induced cracks

Concrete is sensitive to temperature. Therefore, its properties and performance are significantly impacted by temperature variations. For instance, in hot weather, the concrete expands, and in cold conditions, it contracts. However, if there is no room to accommodate these dimensional changes, the material may crack.

For regions that experience snowfall, there is also another symptom—heaving cracks may occur. Frost heaving occurs when water enters the concrete or subbase may freeze and expand. It lifts the concrete and causes cracking when it thaws and resettles.

4. Re-entrant corner cracks

Did you ever notice concrete cracks at the inside corner of fixed objects like columns, manholes, or irregular geometries? These are known as re-entrant corner cracks, which occur when concrete shrinks at different rates in these areas. The stress due to shrinking tends to concentrate at these re-entrant corners, causing cracks. These cracks don’t just look bad but can also lead to material failure.

5. Excessive load cracks

As mentioned previously, concrete has high compressive strength which makes it able to bear higher loads. However, the material still has a load-bearing limit, and exceeding will cause cracks in the concrete. This phenomenon is quite common in industrial settings, loading docks, or areas with heavy vehicular traffic.

How to prevent structural cracks in concrete

As we all know, prevention is always a better solution than cure. So, it’s better to be cautious and save your maintenance costs than regret later. Here’s how you can stop concrete from cracking:

• Try to control the water ratio in the concrete mixture: Using excessive water dilutes the mixture and impacts the strength of the concrete. Plus, during the drying process, high water content leads to greater shrinkage and concrete cracks.
• Use appropriate reinforcement: If you want to avoid settlement or foundation-related cracks, consider thorough subgrade compaction. It’s better to avoid pouring concrete over soil that doesn’t have enough density. Using the right reinforcement also helps to handle minor differential movement.
• Provide expansion joints: For extreme environments, using compressible fillers can help with thermal expansion and contraction. Ask your builder to install proper drainage around the structure for water draining.
• Use high-quality cement sealer: Applying cement sealer on concrete surfaces regularly helps to increase its durability and longevity. The sealers don’t let water penetrate which is essential to avoid cracking caused by moisture.

You May Read: How Concrete and TMT Bars Create Strong, Durable Structures?

How to repair concrete cracks?

Whether it’s the driveway, walkways, or commercial buildings, concrete cracks are quite common. However, the width of the crack matters. Hairline cracks or those under ¼ inch wide are generally not structural threats. But cracks wider than ¼ inch or deeper may cause problems such as subgrade instability or excessive load stress. While you can still repair these types of cracks, it’s often a temporary solution. In many cases, a full removal and replacement of the damaged section may be necessary to restore long-term integrity.

Let’s take a look at how to repair narrow and wider cracks:

Repairing narrow cracks:

Before you start the repair process, please make sure you are working in dry weather to avoid moisture damage. When repairing, first clean the crack using a chisel or slotted screwdriver to remove loose debris, grass, or weeds. If you’re using a pressure washer, then let the concrete dry off completely.

For narrow cracks, a concrete crack filler or masonry crack sealant is ideal. These are specifically formulated for flexibility which helps the filler to stay intact when concrete expands and contracts with changing temperatures.

Repairing wider cracks

Wider cracks need more preparation. Hence, it is better to take assistance from experts. For deep cracks, using a concrete backer rod helps to feel the void. This foam rod acts as a filler base and helps control the depth of the patch. It makes sure the repair is both economical and uniform.

Final thoughts

For modern structures, structural integrity is very essential. However, concrete cracks can weaken it leading to major damage. So, it is important to take proper precautions to avoid spending thousands of rupees on maintenance.