What Is Spalling Concrete & How Do You Identify It?

What is spalling concrete, and how to identify it?

Scaling concrete is a common problem in which a portion of the concrete’s surface peels, chips or breaks away. When concrete spalls, it can damage the reinforcing steel in the building’s top layer. There are some spalls that are about 15 cm in diameter and 2.5 cm in depth. Spalling of concrete can affect a variety of buildings ranging from single landed property homes to large skyscrapers.

Concrete with spalling appears patchy and pitted while exposing the interior material. When spalling is spotted, it should be repaired promptly, otherwise, it can compromise the concrete surface’s integrity and compromise the structure’s capacity. Additionally, spalling can distort the aesthetic appearance of the building, making it unsightly.

Older buildings are typically affected by spalling concrete damage, which is characterized by flaking, chipping or large chunks disappearing from the surface. The rocky aggregate beneath the spalled concrete is also exposed as a result of concrete damage. However, visual inspections are only as good as the concrete itself, since concrete spalling is caused by both chemical and physical processes. To determine the type of damage and the steps that must be taken to repair the concrete, a professional inspection should be performed. It is important to repair concrete damage or spalling as soon as possible, especially on ceilings, since they can harm occupants. Residents of Singapore have been injured by spalling concrete on several occasions.

Hydro-seal Specialist Repairing Concrete

What causes spalling concrete?

There are several causes of spalling concrete. However, it is largely caused by carbonation, which is the natural deterioration process of concrete. Over time, water seeps into the concrete, which reacts with calcium compounds and carbon dioxide, causing cracks to develop and decreasing the concrete’s durability. This carbonation causes the steel bars embedded in the ceiling slab to corrode, which in turn causes the concrete cover to crack and bulge. Several other reasons cause spalling concrete, namely:

1. Corrosion of embedded reinforcing steel, and because the resulting rust occupies more volume than the original steel, the resultant pressure spalls the concrete.

2. Fire exposure causes water within the concrete to boil and stem, creating internal expansive pressure in the concrete, consequently causing spalling damage.

3. Expansive effects of Alkali-Silica Reaction whereby silica reacts with alkali hydroxide in concrete to form a gel that swells as it absorbs water from the surrounding cement paste or the environment.

4. Inadequate depth of cover over reinforcement.

5. Low-quality concrete cover over reinforcing steel.

6. Joint spalls are often caused by improperly constructed joints lead to joint spalling.

How to prevent spalling concrete

Although concrete spalling is common and may be part of the natural life cycle of concrete, there are several steps one can take to extend the lifespan of the concrete.

1. Paint Ceilings Frequently A coat of paint can help slow down the natural carbonation process of concrete by helping reduce the amount of moisture seeping into the concrete. It is recommended to paint your ceilings every three to five years and use anti-carbonation or good quality paint when doing so.

2. Seal Holes and Cracks Quickly Cracks and holes in concrete are dangerous as it allows moisture to enter the concrete surface. A simple visual inspection will reveal if concrete surfaces have any holes or cracks. Upon finding any cracks or holes in the concrete, immediately seal them with hydraulic cement to prevent further damage to the concrete. Similarly, drill holes that are no longer in use, such as holes left from fixtures, should be sealed up as well.

3. Ensure Sufficient Ventilation A humid environment speeds up concrete carbonation. Hence, when moisture-prone areas such as the kitchen and toilet are not in use, it is advisable to keep the windows, vents, or doors in the area open to provide proper ventilation.