Concrete spalling, often referred to as "concrete cancer," is a widespread issue in aging concrete structures. It's a problem you want to tackle as soon as it's identified, but many building owners or strata companies may not fully grasp the extent of the issue or its severity. In simple terms, it is a problem that should not be underestimated.
So, what exactly is concrete spalling?
Concrete spalling arises when the steel reinforcement within a concrete slab begins to corrode. Corroded steel expands to nearly five times its original size, displacing the concrete and causing it to flake.
As the concrete deteriorates and flakes, it creates a vicious cycle; more water infiltrates the affected area, promoting further corrosion, and thereby escalating both the process and the damaged area.
Although various factors can contribute to concrete spalling, the primary cause is typically the corrosion of steel reinforcement bars embedded within the concrete. Other ferrous elements within the structure, whether fully or partially embedded, can also contribute to this problem.
Common culprits include steel frame window systems, handrails, structural I-beams, metal pipes, and conduits. However, corrosion of the reinforcing steel remains the most common cause of spalling and degradation in older concrete structures.
What Causes Concrete Spalling?
Concrete cancer can have various causes, depending on the specific circumstances of each case. However, the most common causes include:
- Inadequate Cover: When steel reinforcement is too close to the concrete surface, it allows water to come into contact with the steel, accelerating corrosion.
- Low-Quality Steel: The use of inferior quality steel reinforcement can hasten the corrosion process.
- Galvanic Corrosion: Incompatible metals positioned in close proximity to each other can create a galvanic reaction, causing corrosion.
- Concrete Damage: Any damage to the concrete that allows water to infiltrate the slab and reach the steel can trigger spalling.
How Do You Identify Concrete Spalling?
Typically, property owners become aware of concrete spalling only when visible symptoms appear or when delaminated concrete starts falling from the structure. However, visible concrete defects often indicate more extensive underlying issues.
The initial visible signs often include concrete staining and discoloration, which can be mistaken for weathering effects. Concrete flaking from the surface, combined with discoloration, typically indicates substantial structural problems.
The Stages of Spalling:
The development of corrosion within concrete usually progresses through several stages:
Depassivation: Corrosive substances penetrate the concrete, reaching the steel, and corrosion initiation begins.
Actual Corrosion: Corrosion occurs, with the rate dependent on moisture and oxygen levels. As the concrete cover cracks due to the tensile stresses resulting from corrosion, this phase reveals the first visible signs of corrosion, often appearing as rust stains on the concrete surface.
Expansion and Spalling: The expansion due to corrosion continues, leading to the complete detachment and spalling of concrete cover sections. This can pose risks to both the structure's users and the general public.
Severe Reinforcing Bar Loss: At this stage, the loss of reinforcing bar diameter is so significant that it approaches the minimum required for structural stability. In such cases, catastrophic structural failure becomes a real possibility.
The Cost of Concrete Spalling Repairs
Property owners often ask why contractors can't provide a more accurate estimate for spalling repair costs. While qualified estimates can be provided once the extent of the spalling is known, the full scope of the issue is often challenging to quantify until work begins, and the affected concrete is removed, exposing the amount of steel in need of repair.
While the timeframe and costs can vary significantly for each property, the fundamental principle remains constant: spalling will persist until it is thoroughly addressed and repaired.
Doing Nothing Is Not an Option
Ignoring spalling concrete exposes property owners to potential negligence claims, as the falling concrete pieces can harm people or property. Delaying repairs will only lead to higher costs as the problem escalates.
Merely covering affected areas with concrete or paint does not address the underlying issues. To effectively address the problem, spalled concrete must be removed, and any exposed steel must be either replaced or cleaned and treated.
While minor issues may only require cosmetic repairs, untreated spalling can escalate to a point where it affects the structural integrity of the building, potentially leading to catastrophic failure of the structure. Taking no action only results in further damage and substantially higher repair costs later on.
It’s important to contact a concrete spalling repair service such as MJ Engineering Projects in Sydney as soon as any concrete spalling issue is detected in the building.