TYPES OF CONCRETE CRACKS

Concrete Cracks

Concrete cracks are occur due to several reason like due to constructional movement, shrinkage etc.After hardening, cracks occur due to chemical reactions and thermal changes. 

The main reason of concrete cracks are as fallows:

1. Excess water in  water-concrete mixture

Due to the adding of excess amount of water in concrete mix it increases the w/c ratio, the strength of the concrete also will reduce.During summer the extra water present in the concrete evaporates which causes shrinkage.Due to the shrinkage cracking can take place in concrete.

2. Rapid Drying Concrete

The actual amount of water is required to be added in the concrete mix to complete the chemical reaction.If the concrete dries before completion of the reaction  it causes cracking.

3. Lack of Control Joints

Lack of control joint leads cracking in the concrete if the area is large.Some time it is also seen that if the dimension of the control joint i.e, thickness of joint is not proper causes cracking.

4. Freezing and Thawing

When excess amount of water freezes in winter, the volume expands and cracking occurs.

Types of Cracks in Concrete

1. Shrinkage Cracks

When concrete is in plastic state, it is full of water.When that water leaves the concrete, it leaves behind large large voids between the solid particles.These empty spaces make the concrete weaker and more prone to cracking.This type of cracking happens frequently and is referred to as "shrinkage cracking".

Shrinkage cracks can happen anywhere in a slab or wall.In a poured concrete cracks can be diagonal or vertical and are usually uniform in width.Sometimes these cracks have a V-shape with top portion of cracks are large and the lower portion of cracks are smaller.

2. Vertical Cracks

Vertical cracks often appear in multiples (multiple cracks in one or more areas). Vertical foundation cracks in poured concrete foundations that tend to appear nearly straight or to wander,normally even in width, intermittent or more often straight is caused by shrinkage/thermal and are usually low risk.

When there is significant vertical dislocation or signs of ongoing movement, you should consult a structural engineer.If the cause is shrinkage, it is probably less of a concern that if due to settlement.

A vertical foundation cracks because of earth loading, or frost could be unusual.A more massive vertical cracks may occur when the construction contractors incorrectly prepare a concrete foooting,and when the wall had poor steel reinforcement as the workers poured the concret to the wall. Cracks may also occur during the footing settlement.

3. Diagonal Cracks

Settlement usually causes diagonal cracks that are almost the full height of foundation wall.When there's a settlement problem with the footing on one side of the wall, this settlement can also cause a diagonal crack.In this type of case, a structural engineer should be consulted.If the diagonal cracks is wider at the top than at the bottom,then it may be caused by expansion clay soil or frost damage.If the crack is wider at the bottom than the top, there is likely a problem with the settlement beneath. 

Some uniform diagonal cracks are merely caused by shrinkage and will only cause water leakage problems.

4. Horizontal Cracks

Horizontal cracks found in the center of the wall are most likely caused by an applied load such as backfill around foundation compacted improperlyor too soon, earth compacting as it settles, hydrostatic pressure against foundation due to high water table and poor drainage against the foundation wall, or heavy equipment operated too soon or too close to the foundation wall.Horizontal cracks found high up on the wall are most likely caused by frost damage.Sometimes these fine cracks are not noticed for years.In a case like this, a structural engineer should be consulted.

5. Structural Cracks

Structural cracks in residential foundations usually result from horizontal loading or settlement.Most structural cracks resulting from an applied load are nearly horizontal and appear 16" to 48" from the top of the wall.They are more common in block foundation walls.

6. Floor Cracks

Floor cracks in concrete slabs are relatively common and usually not worrisome on a structural level.They should be repaired to prevent common issues like moisture, insects and damage from seeping through.When floor cracks leak, it is usually caused by hydrostatic pressure or a high water table.Therefore, sealing the crack will  redirect those issue elsewhere, so fixing the source of those problems beforehand is recommended.

7. Hairline Cracks

Hairline cracks may develop in concrete foundations as the concrete cures.Hairline cracks do not cause problem with the stability of the foundation but do cause leakage problems.If the cracks appear shortly after pouring the concrete foundation, concrete may have been mixed poorly or poured too quickly.In poured concrete foundations, hairline crack frequently appear in the centre of the walls because the wall corners have greater stability.

8. Temperature and Shrinkage Cracks

Horizontal cracks found in the center of the wall are most likely caused by an load such backfill around foundation compacted improperly or too soon, earth compacting as it settles, hydrostatic pressure against foundation due to high water table and poor drainage against the foundation wall, or heavy equipment operated too soon or too close to the foundation wall.Horizontal cracks found high up on the wall are most likely caused by frost damage.Sometimes these fine cracks are notr noticed for years.In a case like this, a structural engineer should be consulted.

9. Settlement Cracks

Settlement cracks may appear when the underlaying ground has not been compacted or appropriately prepared or if the subsoil was not was of the proper consistency.A settlement crack may also appear as a random crack above area where the soil of the subgrade was uneven after the concrete was poured.Settlement cracks are usually more extensive at the top of the crack than the bottom as the foundation "bend" over a single point, allowing differential settlement.This type of cracks is usually continous and may occur multiple times in a wall.