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What Is Spalling Concrete & How Do You Identify It?

Updated: Aug 3, 2021

What is spalling concrete, and how to identify it?

Spalling concrete, also known as scaling, is a common issue where a portion of the concrete's surface peels, chips or breaks away. Concrete spalling damage often extends to the top layers of the reinforcing steel within the building. Spalls may be 15 cm or more in diameter and 2.5cm or more in-depth. Spalling of concrete can affect a variety of buildings ranging from single landed property homes to large skyscrapers.

Spalling causes the concrete surface to appear patchy and pitted while exposing the material within. Once spalling is spotted, it should be quickly repaired; otherwise, it can compromise the concrete surface's integrity and jeopardise the capacity of the structure. Furthermore, spalling can distort the aesthetic appearance of the building, making it unsightly.

Spalling concrete damage is typically found in older buildings and presents itself as flaking, chipping or having large chunks missing from the concrete surface. Additionally, spalling concrete damage exposes the coarse rocky concrete aggregate below. However, visual inspections can only go so far as concrete spalling results from both chemical and physical processes within the concrete itself. A professional inspection should be carried out to ascertain the type of damage of steps required to repair the concrete. It is important to repair concrete damage or spalling quickly, especially on ceilings, as they can cause injury to inhabitants. Cases of spalling concrete hurting inhabitants are common in Singapore.

Spalling Concrete Repair
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.

Contact Hydro-seal Engineering

If you require a waterproofing contractor to inspect your property for spalling concrete, Hydro-seal Engineering is here to assist. Our experienced specialists have performed thousands of spalling concrete inspections since 1995 and will be able to solve your concrete damage issues. Contact us today at 6289 6811 or drop us an email at


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