When it comes to addressing damage in concrete structures, one effective approach is the replacement of damaged concrete members. This involves a meticulous process of demolition, removal, and substitution of existing structural elements with new ones. In this guide, we will delve into the considerations, methods, and practical aspects of executing such replacements.
The decision to replace damaged concrete members arises when other strengthening techniques prove insufficient. This method finds application not only in repairing deteriorated buildings but also in enhancing the lifespan of structures, especially in the case of bridges. It is particularly well-suited for fortifying buildings affected by seismic events.
Choosing the right repair materials is crucial for the success of the replacement process. Adhering to the specifications and recommendations of applicable codes is essential. For instance, reinforced masonry walls require open-ended masonry units, while concrete members must meet a minimum compressive strength of 21MPa.
The execution of damaged concrete member replacement involves several steps:
If the damaged member bears loads, adjacent shoring must be provided to support the loads during demolition.
Use proper tools, such as saws and chipping tools, for the careful demolition of the structural member.
Avoid damaging existing steel bars, as they may need to be spliced with new reinforcements for the replacement.
Prepare the surrounding structure’s surface to ensure a strong bond between existing and new materials, like roughening surfaces.
Splice new reinforcing bars with existing ones and, if needed, anchor new bars to the existing structure using epoxy.
Pour new concrete using suitable means, such as formworks or shotcrete, ensuring proper consolidation.
Implement a proper curing regime to ensure that the concrete achieves the designated strength.
Due to inevitable shrinkage in newly placed concrete, cracks may develop over time. Repairing these shrinkage cracks, typically after two to four months, is essential using epoxy or other suitable materials. Additionally, a percentage of epoxy-anchored dowels should undergo load-testing, and careful inspection of reinforcing steel layout and anchorage is crucial before concrete forming.
In conclusion, the replacement of damaged concrete members is a comprehensive process that demands attention to detail, adherence to standards, and consideration of practical aspects to ensure the longevity and stability of repaired structures.