Concrete Spalling: Causes and How It Can Be Prevented

Concrete spalling is one of the most serious issues affecting the durability of reinforced concrete constructions. It occurs for a variety of reasons, which we will explore in the last section of this article.


The spalling usually occurs in older buildings. Typically, it begins when the structure is between ten and twenty years old. There are additional signs of spalling, such as concrete cracking and concrete that is increasing in volume.

What is Spalling?

Spalling of concrete refers to the process of chipping, cracking, or breaking off of small pieces or flakes from the surface of a concrete structure. It is a common problem that occurs when the outermost layer of concrete deteriorates or separates from the underlying layers.

Effects of Concrete Spalling

Spalling concrete can have several negative effects on both the appearance and functionality of a structure. Some of the common effects of spalling concrete include:

Durability of the Structure

The design life of the structures is impacted when the concrete and reinforcements deteriorate. As a result, the structure’s durability decreases.

Reduction in the Structure Strength

The structural member’s strength is not significantly affected by damage to the concrete’s cover zone. However, the structural strength of a components could be significantly impacted by the concrete’s determination and reinforcing corrosion.

Structural Failures

If the structural members’ strength has become weakened, it could lead to the failure of the structure if the issue is not fixed immediately and the spalling concrete repair is not finished on time.

Spalling at Expansion Joints

Failures of expansion or movement joints may occur.

Aesthetic Appearance

Spalling concrete has an effect on the aesthetics of the construction.

What Causes Spalling Concrete, and How Can It Be Prevented?

Spalling of concrete occurs due to various causes, and preventive measures can help mitigate the risk. Here are some common causes of spalling concrete and methods to prevent it:

Freeze-thaw cycles

In areas with cold climates, seeping water will form ice, which has a larger volume than water.

To prevent spalling caused by freeze-thaw cycles, use air-entrained concrete that contains small air bubbles to accommodate the expansion of water when it freezes. Proper curing and sealing of the concrete can also help minimize water absorption and prevent freeze-thaw damage.

Poor construction practices

Inadequate compaction during concrete placement, improper curing techniques, or incorrect mix proportions can result in a weak surface layer prone to spalling. To prevent this, follow proper construction practices, ensure adequate compaction, provide appropriate curing, and use high-quality concrete mixes.

Corrosion of reinforcing steel

When the steel reinforcement within the concrete corrodes, it expands and exerts pressure on the surrounding concrete, leading to spalling. To prevent this, ensure proper concrete cover over the reinforcing steel, use corrosion-resistant materials for reinforcement, and employ techniques such as cathodic protection or epoxy-coated rebar.

Chemical exposure

Certain chemicals, such as de-icing salts, chloride ions, and acidic solutions, can react with the concrete and weaken its surface, causing spalling. To prevent this, minimize exposure to chemicals, use concrete with low permeability, and apply protective coatings or sealants.

Moisture infiltration

When moisture penetrates the concrete, it can cause damage and spalling over time. To prevent this, properly seal or waterproof the concrete surface, repair any cracks or joints that allow water infiltration, and ensure effective drainage systems around the structure.

Mechanical stress and impact

Heavy loads, excessive vibration, or impact from vehicles, machinery, or construction activities can cause spalling. To prevent this, design structures to handle anticipated loads, avoid excessive vibration during construction, and protect concrete surfaces from impact damage.

To prevent concrete spalling, regular maintenance and inspection are essential. Implementing preventive measures like applying protective coatings, sealants, or waterproofing systems can help prolong the life of the concrete and minimize the risk of spalling. It is also important to promptly repair any cracks or damage to prevent water infiltration and mitigate further deterioration. Following proper construction practices, using high-quality materials, and considering environmental factors during design can also contribute to preventing spalling concrete.

How to Repair Spalling Concrete

Repairing spalling concrete involves several steps to restore the damaged surface and prevent further deterioration. Here is a general guideline for repairing spalling concrete:

Step 1

Carefully remove the loosely attached concrete blocks. For enhanced safety, an extra two inches of concrete are usually removed around the affected area.

Step 2

In order to further improve safety, sounding equipment may be employed to identify any unevenness that may exist near the spalled-affected area. To avoid issues in the future, any area of concern can also be treated.

Step 3

To get rid of any steel rust, the reinforcement can be cleaned with a wire brush.

Step 4

Clean the exposed area with compressed air, and then paint or coat the reinforcements with an anti-rust polymer.

Step 5

To achieve proper bonding, the existing concrete surface may be made rough or bonding agents may be applied to assure adherence.

Step 6

Normal or polymer-based concrete will be used to fill the damaged area. Make sure that the new filler material and the old concrete have the same thermal expansion coefficient. This eliminates any inconsistencies caused by uneven heating and cooling.

Step 7

The surface must be polished smoothly to reduce water accumulation on the surface.

Step 8

To avoid water seepage, the surface should be coated with water-repellent paints.

Concrete spalling is common in cold-weather areas. Proper supervision, the addition of air-entraining agents, and the application of a water-repellent coat can considerably reduce it.

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