Shrinkage Cracks In Concrete Walls

Shrinkage restraint cracking resulting from shrinkage can occur in concrete masonry walls because of drying shrinkage temperature fluctuations and carbonation.

Shrinkage cracks in concrete walls.

Concrete slabs can shrink as much as 1 2 inch per 100 feet. Hairline cracks are commonly observed in freshly placed concrete and their occurrence is owed to the phenomenon of plastic shrinkage. They expand when they absorb the moisture and shrink when they dry. These empty spaces make the concrete weaker and more prone to cracking.

Shrinkage cracks in concrete occur due to change in moisture of concrete. Concrete and mortar are porous in their structure in the form of inter molecular space. These are very common and unless they leak or show signifi cant lateral displacement are of no structural concern. Jagged cracks stair step cracks and 45 degree angle cracks generally signify structural movement or settling issues that are occasionally serious but usually harmless.

Shrinkage cracks such as shown in our photograph above are found in poured concrete are easily recognizable and can be distinguished from other types of cracks that occur later in the life of a foundation wall or floor slab as we explain here. Shrinkage and temperature cracks are most often vertical to diagonal. Hairline cracks in concrete. This is the main cause of concrete shrinkage cracks on drying.

This shrinkage causes forces in the concrete which literally pull the slab apart. Cracks are the end result of these forces. They typically emanate from a corner of a window beam pocket or other opening. These cracks are usually considered normal and generally not a great concern however they can be a warning sign of problems.

If a diagonal crack appears near a door or window you can blame it on concrete shrinkage as with vertical cracks. Vertical and horizontal cracks in drywall or plaster walls typically indicate drying and shrinkage which is normal after construction. Plastic shrinkage concrete cracks when concrete is still in its plastic state before hardening it is full of water. As the name implies these cracks are very small about 0 003 inches 0 08mm in width and can be very shallow.

Diagonal diagonal cracks can form for the same reasons vertical cracks do. Cracks of this type are called reentrant cracks. If you notice a diagonal crack in addition to wall bowing you likely have split supports in your walls. The bottom line is a low water to cement ratio is the number one issue effecting concrete quality and excess water reduces this ratio.