Cracks! At the sight of a crack in concrete, most of us panic.

Is my house falling apart?

Does the foundation need replacement?

Lots of questions ? ? ? and few answers……….

Following information is intended to provide some basic reasons as to why concrete cracks and answer some of the questions.

However only a qualified technical engineer or an experienced contractor will be able to correctly analyse the cause and type of crack, and suggest the correct suitable remedy for it.

Why Does Concrete Crack?
Various forms and sizes of cracks can be seen in concrete structures.
It is important to realise that cracks as such are not necessarily defects needing repair.
Most cracks occur as a result of shrinkage of concrete.
Shrinkage is simply a reduction in the volume of concrete as it hardens.

If this reduction in volume were unrestricted, then a crack would not occur. However, in reality, ground friction and a number of things such as structural connections inhibit free shrinkage and thus cause cracks.

How much shrinkage is normal?
A 30 mtr-long regular-weight concrete slab normally would shrink by about 20 mm. In other words, you should expect cracks totaling in widths up to 20 mm in every 30 mtr of concrete.

It is important to note that concrete does crack and that this is normal. What is not normal is an unsightly and excessive amount of cracks.

Cracks can be broadly classified as either active or dormant.
If they are active, they show some movement in direction, width or depth over a measured period of time. If the cracks are dormant, they remain unchanged.

Some dormant cracks are of no danger, but if left unrepaired, cracks provide channels for moisture and water penetration, which can lead to future damage such as peeling of paint, corrosion of reinforcement etc.

Cracks can be more specifically classified based on three factors: 1) direction, 2) width, and 3) depth of the crack. They may be longitudinal, transverse, vertical, diagonal or random. They may range in size from less than 1 mm (fine) to between 1 and 2 mm (medium) to over 2 mm (wide).

A careful examination of the cracks, by a qualified engineer, will give valuable information about the cracks and will indicate their cause.