Your initial thought when you notice a crack in your concrete slab or wall is that something has gone wrong, but this isn’t always the case. Different types of concrete cracks are fairly common, and some of them are unavoidable.
Various types of concrete cracks may emerge on the building during construction or even after completion due to various circumstances. Concrete fractures occur when the tension exceeds the strength of the material.
External loads and forces are the most common causes of stress. R.C.C columns develop cracks of various forms depending on the stress and exposure circumstances to which they are exposed.
Columns are prone to cracking because of their improper design and construction, overloading, corrosion exposure, foundation settlement, creep, and shrinkage concerns.
Cracks in reinforced concrete can arise owing to insufficient section size or reinforcing steel, as well as reinforcement corrosion. This article aims to discuss the various most common types of concrete cracks.
Types of Cracks In Concrete
Here are some of the types of cracks in concrete.
1. Diagonal Cracks
Diagonal cracks can appear anywhere along with the reinforced concrete’s height. These types of cracks always affect the entire concrete column face.
Insufficient cross-section, insufficient load-carrying capabilities, and insufficient reinforcement steel are the most common causes of diagonal cracks in concrete columns.
Diagonal cracks must be repaired immediately since they might weaken the entire structure in a short period of time.
2. Splitting Cracks
Split cracking appears as short parallel vertical cracks with non-uniform width on the concrete column face.
The insufficient load-bearing capacity of the column, an inadequate cross-section of the column to withstand the load action, insufficient steel reinforcing, and poor concrete quality can cause splitting fractures into concrete columns.
3. Corrosion Cracks
Corrosion cracks form primarily along the course of the concrete column reinforcement. Corrosion cracks are mostly the same width and usually get wider as they age.
The main cause of corrosion reinforcement in concrete columns is insufficient bonding between concrete and steel bars, as well as possible reinforcement corrosion.
4. Plastic Shrinkage Cracks
Concrete is full of water when it is still in its plastic condition (before hardening). When the water gradually evaporates from the slab, it leaves enormous holes between the solid particles.
These voids weaken the concrete and make it more prone to breaking. This type of breaking is known as plastic shrinkage cracking and occurs often.
Plastic shrinkage cracks are the most common type of concrete crack. It can occur anywhere in a slab or wall, although they usually always occur at reentrant corners (corners that point into the slab) or in the centre of a slab with circular objects (pipes, plumbing fixtures, drains, and maintenance holes).
5. Expansion Concrete Cracks
Concrete expands and pushes against anything that gets in its way when heated. The force created by the inability to bend or flex cracks the concrete.
Expansion joints are always employed as points of isolation from any other static objects to reduce these types of cracks in concrete.
Expansion joints are formed of a compressible material such as asphalt, rubber, or timber and serve as shock absorbers to relieve tension generated by expansion.
6. Concrete Fissures Induced By Slab Overload
Although concrete is a relatively robust building material, it is not without limitations.
The excessive weight placed on top of a concrete slab can cause cracking. A PSI of 2000, 3000, 4000, or 5000+ refers to the pounds per square inch necessary to crush a concrete slab.
Overloading of the actual slab is not very prevalent in residential concrete slabs. Instead, undue overload on the ground beneath the slab is more likely.
Excessive weight on the slab after heavy rain or snowmelt when the earth below is soft and moist might press the concrete down and result in cracks.
7. Settling Concrete Cracks
Ground settling beneath a concrete slab, on the other hand, can produce cracks. Settling cracks often occur when a void in the earth underneath the concrete surface forms.
Consider when a large tree is removed from a nearby area, and the roots begin to degrade, or when a utility company digs a trench for their lines, pipes, etc., and does not compact the soil when refilling it. All these are examples of situations where settling cracks are likely to occur.
8. Concrete Cracks As a Result of Premature Drying
There are two types of cracks caused by early drying- crazing cracks and crusting cracks. Crazing cracks are surface cracks that look like spider webs or shattered glass.
Crazing cracks are prone to form when the top of a concrete slab loses moisture too quickly. Crazing cracks, while ugly, do not pose a structural risk.
During the concrete stamping process, which imparts texture or pattern to concrete surfaces, crusting fractures are frequent.
The top of the concrete surface might become crusty on bright or windy days when the top of the slab dries out faster than the bottom.
When the stamp is pressed into the stone, it pushes the surface apart at the printed joints, causing minute fissures.
Again, while they don’t look good, crusting cracks are not a structural concern that needs to be addressed.
9. Horizontal Concrete Cracks
Horizontal cracks are most commonly encountered at beam and column junctions, as well as at the column face, where tensile stress is high.
Horizontal cracks in columns are caused by the following factors: insufficient moment resistance capacity, insufficient reinforcement, the effect of shear force, direct load, and uniaxial bending, and the placement of installed reinforcement.
If allowed to persist, horizontal cracks would reduce the shear strength of the column, posing a significant danger of structural failure. As a result, it demands prompt attention.
Heaving Concrete Cracks
When the ground freezes, it can rise several inches before thawing and falling back down. The ground movement caused by the freezing and thawing cycle is a significant contributor to concrete cracking.
The slab will crack if it is not allowed to move with the ground. Large tree roots can have the same effect on a slab as small tree roots.
Growing roots can lift and shatter the concrete surface if a tree is planted too close to a slab. When laying a slab, it is important to keep this in mind at all times.
Due to the expansion of each slab in opposite directions, cracks are likely to form in walls where lengthy roofs at various levels are installed. It is frequently difficult to pinpoint what produced a specific crack. Proper site preparation, a high-quality mix, and good concrete finishing techniques can help reduce the appearance of cracks and produce a more aesthetically pleasing concrete structure.
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