Understanding Cracks in Concrete: Causes, Types, and Prevention Methods

Concrete cracks. Yes, it might surprise you, but it does. Most of us grow up thinking concrete is permanent. You pour it once and forget about it. But anyone who has spent time around buildings, roads, or construction sites knows that cracks are almost unavoidable. Walk around any structure that’s a few years old, and you will find them. These cracks in concrete do not all mean the same thing, though. Some are harmless. Some are early warnings. The trouble is that they often look similar at first glance.

So instead of panicking or ignoring them completely, it helps to understand why concrete cracks and what those cracks usually tell us. Read this comprehensive guide to learn it all. 

Why Concrete Cracks?  

Concrete is strong when you press it. It’s weak when you pull it. This simple fact explains most cracking.

• One very common cause of cracks in concrete is water leaving the mix. Concrete always contains more water than it actually needs. As time passes, that extra water escapes. When it does, the concrete shrinks slightly. If it can’t move freely, it cracks. This is normal behaviour

• Temperature is another cause of cracks in concrete. Concrete expands in heat and contracts in cold. When one part of a slab heats up faster than another, stress builds up. Eventually, thermal cracks in concrete appear. This happens a lot in large slabs and thick walls.

• Then there’s workmanship. Too much water, poor curing, bad finishing and incorrect placement of concrete reinforcement bars can cause cracks in foundation. None of these causes immediate collapse, but they quietly increase the chances of cracking later.

• Also, don’t forget the ground. Soil moves. It settles unevenly. Concrete sitting on it has no choice but to react.

Structural Cracks vs Non-Structural Cracks 

This is where most confusion starts. Below is a detailed explanation of structural and non-structural cracks. 

Structural Cracks in Concrete 

Structural cracks in concrete affect how a building carries a load. These usually come from foundation movement, design problems, or overloading. They tend to change over time. These cracks should never be ignored.

Non-Structural Cracks  

These cracks mainly affect the surface. Most shrinkage cracks fall into this category. They don’t weaken the structure immediately, but they allow moisture to enter. Over time, that moisture can lead to corrosion of reinforcement, which is when real damage starts.

Small Cracks: Should You Worry?  

Honestly? Sometimes yes. Sometimes no.

Hairline cracks are extremely common. Indoors, many of them never change. Outdoors, things are different. Rain, humidity, pollution, and temperature cycles slowly make cracks worse. This slow damage is how concrete durability reduces without anyone noticing until repairs become expensive.

So, small cracks should not cause panic, but they should not be ignored either.

Common Types of Concrete Cracks  

Concrete cracks can be categorised into different types. Below are the types of concrete cracks you must know about. 

Plastic Settlement Cracks 

These appear early, when concrete is still soft. Heavy particles settle downward, and cracks appear above steel bars. This is common in columns and beams. They are often linked to inadequate vibration or improper mix consistency during placement.

Plastic Shrinkage Cracks 

These show up when the surface dries too quickly. Wind and sunlight make this worse. Usually seen on slabs. Proper curing and surface protection during the early hours can significantly reduce their formation.

Drying Shrinkage Cracks  

Concrete keeps losing moisture for a long time. If movement is restrained, shrinkage cracks in concrete form, often near corners and joints. These cracks usually develop weeks or months after construction is completed.

Thermal Cracks 

Heat from cement hydration causes expansion. Uneven cooling later creates internal stress. That’s when cracks form in thick concrete sections. They are more common in mass concrete, where temperature control is difficult.

Settlement Cracks in Concrete  

When soil settles unevenly, cracks appear diagonally. Settlement cracks in concrete are often seen near doors, windows, and foundations. Poor soil compaction or changes in moisture content below the structure can worsen this issue. 

Crazing  

Looks like a spider web. Very fine surface cracks. Mostly cosmetic, but not great for long-term surface quality. Although shallow, they may allow surface wear to increase over time if left untreated.

Cracks Due to Steel Corrosion  

Water reaches steel, rust forms, rust expands and concrete cracks outward. This is classic corrosion of reinforcement damage. This type of cracking often leads to spalling and loss of bond between steel and concrete.

Concrete Crack Repair   

There is no universal fix. Good concrete crack repair depends on the reason behind the crack.

• If strength needs to be restored, injection methods are used. Epoxy bonds cracked sections. Flexible materials are used when movement continues.

• Surface cracks are often treated with patching materials or overlays. These protect the concrete rather than strengthen it.

• Cracks caused by soil movement often need grouting or slab lifting. Fixing the crack without fixing the base doesn’t work.

How to Prevent Concrete Cracking?  

How to prevent concrete cracking? You cannot stop all the cracks. But you can control them.

• Good mix design matters.

• Proper curing matters more than people admit.

• Correct placement of concrete reinforcement bars matters every time.

• Material quality matters too. Steel from a reliable TMT manufacturer resists corrosion better and bonds properly with concrete.

Why Does Reinforcement Quality Matter?  

Reinforcement doesn’t stop cracks. It controls crack width. Poor-quality steel corrodes faster and bonds poorly. This leads to wider cracks and faster damage.

Choosing a dependable TMT manufacturer like Sree Metaliks Limited improves consistency, bonding, and long-term performance. This is not a theory. This is what actually happens on site.

Also Read: Different Types of Concrete Mixing Ratio

Conclusion  

Concrete cracking is normal. Ignoring cracks is not. Some cracks are harmless. Some are warnings. Knowing the types of concrete cracks, understanding their causes, and choosing the right repair approach keeps structures safe and usable.

Good workmanship, proper curing, and reliable materials make a real difference. This is why Sree Metaliks Limited supports durable construction by supplying quality steel suitable for reinforced concrete structures.

For more information, please reach out to us at: Sales@sreemetaliks.com