Concrete cracks can vary in severity and impact, ranging from cosmetic issues to serious threats to the structural integrity and safety of a building.
In this article, our primary focus is to shed light on the identification of cracks in concrete. We delve into the most prevalent types of concrete cracks and explore the underlying reasons for their occurrence.
Pre-hardening Cracks in Concrete: Plastic Shrinkage and Settlement Cracks
During the early stages of concrete placement and curing, certain types of cracks can develop before the concrete sets. These pre-hardening cracks include plastic shrinkage cracking and plastic settlement cracking.
Plastic shrinkage cracking occurs when the concrete surface dries too quickly, leading to rapid moisture loss. It can happen in various weather conditions, including hot and windy environments, as well as cooler low-humidity conditions. These cracks typically appear during the bleeding stage and the finishing process.
Plastic settlement cracking occurs when concrete settles due to insufficient compaction during placement. It is caused by the weight of the concrete itself, which leads to settlement and subsequent cracking.
Formwork-Related Cracking in Concrete
Cracks in concrete can also stem from formwork movement. When the formwork shifts after the concrete has started to harden but before it has acquired enough strength to support its own weight, cracks may develop. Unlike other types of cracks, formwork-related cracking does not follow a specific pattern.
Post-Setting Cracks: Understanding Cracking in Hardened Concrete
Cracks in hardened concrete that occur after setting can be a cause of concern and require attention. These cracks can be attributed to various factors, such as shrinkage, thermal stress, structural overloading, or external forces.
Long-term Drying Shrinkage Cracks:
Over time, concrete can shrink as it loses moisture, leading to these types of cracks. They often appear as hairline cracks running in random directions and are a result of the concrete’s natural drying process.
Crazing cracks are a network of fine, shallow cracks that resemble a spider’s web. They are caused by the surface layer of the concrete drying too quickly or by improper finishing techniques.
Corrosion of Reinforcement Cracks:
When the reinforcing steel within the concrete corrodes, it expands and can cause cracks to form. These cracks are typically wider and can occur near the reinforcement.
Certain aggregates containing non-crystalline silicon dioxide, also known as silica in a glassy form, can trigger a chemical reaction with alkali hydroxides present in concrete. This reaction occurs when alkalis from sources such as portland cement or environmental factors like sea spray or groundwater encounter the non-crystalline silicon dioxide. The result is the formation of an alkali-silicate gel that gradually swells upon absorbing moisture from the surrounding cement pore solution or environment. Over time, this expansion causes cracks to develop in the concrete. The process can take anywhere from 5 to 20 years before the accumulated cracking compromises the structural integrity of the concrete. It is imperative to be aware of this hidden danger and take proactive measures to prevent alkali-aggregate reaction-induced failures in concrete structures.
It is advisable to address cracks as soon as they are noticed to prevent further damage and ensure the long-term durability of the structure.
By consulting with a professional, you can ensure that the crack is properly evaluated and that appropriate measures are taken to address the issue. This will help to prevent further deterioration, maintain the structural integrity of the concrete, and ensure the safety and longevity of the building or structure. Professional restoration services can help identify the root causes, repair the concrete, and implement preventive measures to mitigate further damage. If you notice any of these signs in your parkade or building, it is crucial to take prompt action. Consulting with a professional building restoration company can help you assess the extent of the issues and develop a comprehensive plan for rehabilitation. Don’t wait, contact us today to learn more about our comprehensive services.