Citi-Con is a reputable concrete patch repair expert having deployed this capability for various applications. These include use of cementitious materials [cementitious material in concrete Topic] to repair damage caused by corrosion and other mechanisms. In addition to restoring structural integrity, our concrete patch repairs fill blowholes and other surface imperfections. In this way, it also fulfils an aesthetic role.
Corrosion of steel reinforcement usually manifests in delamination [Concrete Delamination- Causes, Effects, and Precautions – theconstructor.org]. Cracking or spalling [Spalling concrete: the causes, and control, repair & protection methods | Mapei] are also common signs of reinforcement corrosion. Corrosion incurs when concrete is exposed to chloride-ions and carbon. Refer to Chloride-induced corrosion on reinforcing steel: from the fundamentals to the monitoring techniques – ScienceDirect. Also reference Diagnosis of carbonation induced corrosion initiation and progression in reinforced concrete structures using piezo-impedance transducers – ScienceDirect. Corrosion remains the primary cause of structural failure. It currently costs the global economy over US$3-trillion.
To address this problem, we apply a specific concrete patch repair solution. Our teams break back to sound dense concrete at least 20mm behind the steel reinforcement. The steel reinforcement and concrete substrate is then primed with an appropriate steel primer before receiving a substrate bonding coat. We can then start rebuilding to the original surface profile.
Concrete can also be damaged due to accidental or physical loadings, temporary overloading, impact and other mechanical or uncontaminated damage. Excessive early shrinkage [Center for Transportation Research and Education:] or thermal stresses [diva-portal.org/smash/get/diva2:999744/FULLTEXT01.pdf] also damage concrete structures. This is in addition to low quality honeycombed or off-form voided concrete.
In these instances, we break out the damaged concrete to sound and dense material before rebuilding to the original profile. The depth of the removal of defective steel reinforcement is reviewed at the time concrete assessment.
Concrete patch repairs surface imperfections
Our concrete patch method repairs blowholes of no more than 15mm in diameter or 5mm in depth. They have been caused by the entrapment of air bubbles in the surface of concrete during placement and consolidation. Refer to Blow holes | Concrete Society.
These are filled with a scrape coat consisting of a single component polymer modified cementitious coat repair mortar. Such a coating may also be used as a primer for the application of a protective or decorative coating.
Quality concrete patch repair materials
Citi-Con only uses quality patch repair materials for reinstatement.
They are single component polymer modified cementitious non-shrink repair mortars or part of approved complete polymer modified cementitious repair systems. It is critical that the repair strength is always similar to the in-situ concrete strength. Repair – Euclid Chemical are good examples of the type of repair materials that we deploy on our projects.
We only source our materials from reputable manufacturers and suppliers and ensure that they are supported by relevant documentation. This includes relevant test certificates, as well as material data and safety data sheets. Refer to pds-express-repair-november-2024.pdf and GHS SDS as examples.
As an approved applicator of these systems, we are experienced in their use. This includes making sure that the cementitious material, steel primer and substrate bonding coats are thoroughly mixed. In this way, we ensure a uniform colour and consistency. Moreover, our materials are never thinned.
There are further steps that we take to ensure the integrity and long-term performance of patch repairs. This includes making sure that no cracking is allowed at the concrete repair interface with existing concrete. In addition, we only cure the compound according to the manufacturer’s specifications. When concrete repairs are greater than 500mm x 500mm, we supplement the curing compound with heavy duty polyethylene sheeting. It is fastened and sealed at the edges.
The correct use of repair materials enables us to guarantee our workmanship for the maximum available term. Extensive repairs, especially those involving proper bonding techniques, can last between 20 and 30 years.
Concrete patch repair processes
There are three main phases of Citi-Con’s concrete patch repair processes. They include halting the corrosion process, replacing concrete and applying protective treatment.
A critical component of a successful repair process entails successfully stopping the corrosion of reinforcing bar. We do not only focus on areas where rust is already visible but also where corrosion is likely to still occur. This is done by removing the rust and applying a suitable priming coat to protect steel against further corrosion. In other words, we re-passivate it. Refer to Steel Rebar Coatings for Concrete Structures for more information on this aspect of our concrete patch repair solutions.
By replacing deteriorated concrete, we maintain structural integrity. We provide adequate alkaline protection to the steel reinforcement. Furthermore, this intervention provides an even continuous surface for the application of a suitable protective coating system. This while also satisfying visual and aesthetic requirements.
The final protective coatings increase the durability of reinforced concrete structures. This is by providing additional protection against exposure to the environment and enhancing their aesthetic appearance. Coatings’ elastic properties bridge any fine cracks present in concrete or those which may appear later in the patched area.
Testing concrete patch repairs
We then finalise the project by testing the performance of our concrete patch repairs.
This includes testing for compression strength, adhesion, delamination, flatness and placement tolerance of the finished product.
Compressive strength of the cementitious repair material should be tested with test cube samples at a prescribed frequency. Bond strength testing is undertaken on partially cored direct pull-off tests of the fully cured in-situ repair material. This verifies the tensile bond between the in-situ repair material and the existing concrete substrate seven days after application. Refer to Guide to Pull-Off Adhesion Testing – Industrial Physics. A visual inspection of all repaired areas is always undertaken immediately prior to the application of any decorative/anti-carbonation coating. This also entails checking for delamination and other defects.
Learn more about Citi-Con. www.citicon.co.za