When it comes to repairing damaged concrete elements, the typical solution is to replace them entirely. This involves demolishing and removing the existing structural elements and then replacing them with new members. Before the demolition process can take place, proper jacking must be applied to relieve any imposed loads on the damaged structural member. During the demolition process, it’s crucial to exercise great care to avoid damaging any existing steel bars that may be present. In cases where existing steel bars are present, splicing them with newer ones is considered a viable option.
For severely damaged structural members, a complete replacement is often the most cost-effective method of repair. This approach has been widely used in the repair of structures that have suffered from earthquakes. It’s important to ensure that the newly constructed structural member possesses similar strength to the previous element, or in some cases, even improves upon it. It’s worth noting that all types of damaged concrete structural members such as beams, columns, braces, and walls can be replaced using this method.
When is Damaged Concrete Members Replacement Required?
When other methods of strengthening a structure are deemed insufficient, there is a repair technique that can be utilized. This technique not only repairs buildings that have deteriorated but also serves to extend the lifespan of structures, particularly bridges. It is especially useful for buildings that have been damaged by earthquakes, as it provides the necessary reinforcement to withstand seismic activity.
Specification of Repair Materials
The selection of repair materials for construction should be done in accordance with the specifications and recommendations of applicable codes. To illustrate, when it comes to reinforced masonry walls, the use of open-ended masonry units is necessary. Additionally, the masonry units, grouts, and mortar employed must meet the requirements outlined in ACI530/ASCE 6.
Similarly, for reinforced concrete members, it is essential to ensure that the minimum compressive strength of the concrete is 21 megapascals. This requirement is crucial to guarantee the structural integrity and durability of the concrete member. Therefore, it is imperative to carefully consider the applicable codes and specifications when selecting repair materials for construction purposes. Doing so can help ensure the safety and longevity of the structure being repaired.
Replacement Execution
When dealing with a damaged load-bearing structural member, it is necessary to provide shoring adjacent to it in order to support the loads while the member is being demolished. Proper tools such as saws and chipping tools must be used in the careful demolition of the structural member. If steel bars are present, they should not be damaged as they will be spliced with new steel reinforcements to be installed for the new structural member. The surrounding structure’s surface must be prepared to ensure adequate bond between the existing and new materials by roughening surfaces. New reinforcing bars are spliced to existing bars and, if required, anchored to the existing structure by setting them into holes with epoxy. It is advised to consult the epoxy manufacturer for the proper depth of the bar and instructions for installing the epoxy. The new concrete can be poured using suitable means such as formworks or shotcrete. In the case of formworks, fresh concrete is poured through an access hole near the top, and extra holes may be required to provide access for vibrators to consolidate concrete. Finally, a proper curing regime is employed to ensure that the concrete achieves the designated strength.
Practical Consideration
When constructing new members with concrete, it is inevitable that the newly placed concrete will experience shrinkage while existing concrete will not undergo any movement. As a result, cracks will develop in the concrete of newly constructed members. These cracks will need to be repaired after a significant amount of shrinkage has occurred, typically two to four months after the initial construction.
To repair these shrinkage cracks, epoxy or other suitable repair materials should be used. Additionally, it is recommended that a percentage of the epoxy-anchored dowels be load-tested to at least 50 percent of the yield strength of the bar. During installation of the epoxy, a special inspector familiar with the process should observe to ensure proper installation.
Before forming the concrete, it is also important to inspect the layout and anchorage of the reinforcing steel to ensure it meets the necessary standards. By taking these measures, the integrity and safety of the concrete construction can be maintained.