An Overview of Concrete Failure Analysis
Concrete is used extensively as a building material for floors, walls, foundations, and many other important structural components. Though concrete is known for its unwavering strength, it can easily crack, crumble, and collapse without adequate care. This is why it is an absolute necessity to find out the primary issues that may lead to concrete failure, and this process is referred to as concrete failure analysis.
Before deep diving into the analysis of concrete failure, it is important to discuss the factors that cause concrete failure.
Corrosion of steel within a concrete structure is one of the major factors responsible for concrete failure. This is an entirely natural process that can cause significant tensile stress, causing staining, cracking, and spalling. Corrosion issues are often triggered and exacerbated by certain unavoidable environmental issues.
Carbonation: Carbonation results in the loss of natural alkalinity of concrete due to the ingress of acidic gases from the atmosphere. When carbonation reaches the rebar, the steel starts to corrode in the presence of moisture and oxygen. The damage caused by carbonation depends on concrete quality, environmental conditions, and concrete cover depth over the rebar.
Chloride: Chloride attack is another major reason for reinforcement corrosion. It makes its way to concrete from a chloride-rich environment or via de-icing salts. Even if the concrete is alkaline, chloride in sufficient quantity can initiate corrosion. Chloride attack causes localised heavy pitting of steel and potential loss of structural integrity.
Concrete Failure Analysis
When a concrete structure fails, usually more than one factor contributes to the failure. Therefore, it really helps to consider the larger picture at the start, and gradually move to smaller details.
Before starting on-site analysis, the investigators must try to gather as much background information as they can in the form of project plans and specifications, test data, field notes, concrete batch tickets, change orders, meeting minutes, and weather data during, before, and immediately after the placement of concrete.
The first on-site task for the team is to perform a thorough visual examination. The investigators may also sound the surfaces to detect delaminations, create sketches of the cracks, extract cores, or perform non-destructive tests. All these activities and observations must be noted along with photographs.
In some instances, concrete failure may be entirely because of exceeding the load-bearing capacity of the structure. A thorough examination of the crack pattern will help find out whether the failure has resulted from compression, shear, or flexure. The location of the reinforcing bars can be determined by non-destructive testing. To find out concrete strength related information, some cores may be required.
Good concrete failure analysis demands a proper selection of coring locations. Instead of selecting randomly, visual observations or non-destructive testing can be used for locating the cores. During the process of extraction and shipping, it is important to ensure that the cores are not damaged.
If corrosion is suspected, microscopy specimens without water and chloride-containing epoxides should be prepared. On the other hand, if the investigators suspect a sulphur attack, the electron microscope specimens should be coated with carbon.
Coating Management Solutions is one of the most trusted Australian experts in concrete structure evaluation. Please contact our concrete structure specialists to find out more.