TYPES OF CRACKS IN CONCRETE

TYPES OF CRACKS IN CONCRETE COLUMNS

TYPES

}  1. Cracks due to eccentricity in concrete columns

}  2. Cracks due to corrosion of reinforcement in concrete columns

}  3. Cracks due to increased column load

crack due to eccentricity in concrete columns

Cracks due to corrosion of reinforcement in concrete columns

Cracks due to increased column load

TYPES OF CRACKS IN CONCRETE BEAMS

}  1. Cracks in concrete beams due to increased shear stress

}  2. Cracks in concrete beams due to corrosion or insufficient concrete cover

}  3. Cracks parallel to main steel in case of corrosion in beams

}  4. Cracks due to increased bending stress in beams

}  5. Cracks due to compression failure in beams

Cracks in concrete beams due to increased shear stress

Cracks in concrete beams due to corrosion or insufficient concrete cover

Cracks parallel to main steel in case of corrosion in beams

Cracks due to increased bending stress in beams

Cracks due to compression failure in beams

TYPES OF CRACKS IN REINFORCED CONCRETE SLABS

}  1. Cracks in reinforced concrete Slab due to Steel Corrosion (cracks parallel to steel bars)

}  2. Cracks in reinforced concrete Slab due to shrinkage of concrete

}  3. Cracks in reinforced concrete Slab due to increased load on the slab

}  4. Cracks in reinforced concrete slab due to sulphate attack

}  5. Cracks in reinforced concrete slab due to alkaline aggregates

Cracks in reinforced concrete slab due to Steel Corrosion (cracks parallel to steel bars)

Cracks in reinforced concrete slab due to shrinkage of concrete

Cracks in reinforced concrete slabs due to increased load on the slab

Cracks in reinforced concrete slab due to sulphate attack

Cracks in reinforced concrete slab due to alkaline aggregates

CRACKING IN WALLS

Causes of cracks in wall

Types of cracks in wall

1. EXPANSION CRACKS
2. CRACKS ABOVE OPENINGS
3. WALL TIE FAILURE
4. SUBSIDENCE GROUND HEAVE

1. EXPANSION CRACKS

}  Cause

                Walls are affected by temperature and moisture change. Materials can suffer from initial shrinkage and/or subsequent expansion and contraction. This movement gives rise to the cracks.

2.      CRACKS ABOVE OPENINGS

Cause

Four causes are:

◦       (a) Removal of windows or doors with inadequate propping,

◦       (b) Inadequate bearings,

◦       (c) Loads applied directly over the opening,

◦       (d) No lintels.

3.      WALL TIE FAILURE

}       Cause

}       Wall ties are metal ties that are built into both solid and cavity walls built in stretcher bond to hold the outside skin of brickwork to the inside. Failure normally occurs when the ties rust. When the metal ties rust they expand causing the cracking normally seen every sixth course horizontally in the mortar joints.

4. SUBSIDENCE

}  Cause

}  The worst and most serious type of cracking and consequently the most difficult to repair.

}  Subsidence can occur due to a variety of reasons:

–   1. Mining activity

–   2. Leaking underground drainage

–   3. Tree root activity

–   4. Peak subsoil

–   5. Clay subsoil

–   6. Running sand

GROUND HEAVE

}  The pattern is similar to subsidence cracks; however, the crack will be widest at the base of the wall. The most common cause of ground heave is expansion of clay subsoils. On older properties with shallow foundations the clay can expand and contract dependent upon the weather conditions. If the clay becomes waterlogged it can expand and push the foundations upwards causing the cracks.

}  The removal of trees can also cause ground heave, which is why trees that are too close to the property should be taken down in stages, slowly over a number of years to allow gradual ground movement (the problem of trees and tree roots will also be dealt with in a later article).