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Concrete Repair and Maintenance System

Concrete structures viewed as a durable structure. Proper design of concrete structures along with the appropriate placing of concrete will result in durable structures. Periodic maintenance will increase the concrete structure service life.

Old structures were built using old technology. At the time of construction, the methods of construction were old. The expected service life of these structures will be less than modern structures. Therefore periodic inspection and maintenance should be conducted to ensure and increase the service life of these structures.

New concrete technology enabled the using of concrete in an extremely aggressive environment. The life of structure can be increased by developing and following a maintenance program. The maintenance of a structure is economical than taking no action. Structure in figure no:1 required expensive repairing or replacement. The preventive maintenance of the structure in figure no:1 could reduce the cost of repairing and extend the service life of the structure.

Figure 1

Reclamation and maintenance system consists of seven steps:
1. Determine the cause(s) of damage
2. Evaluate the extent of damage
3. Evaluate the need to repair
4. Select the repair method and material
5. Prepare the existing concrete for repair
6. Apply the repair method
7. Cure the repair properly

A good maintenance program should involve periodic inspections. Monitoring the suspected area. Taking and storing photos and notes of the damaged area to monitor the progression of the damages such as a change in cracks and movement of slab and walls. Those notes and photos will be used later to assess the damage and propose a suitable repairing method.

Many of Reclamation’s maintenance activities concentrating on keeping the aggressive chemical away from concrete, especially for old structures. Old structures can be affected significantly by the aggressive chemical and the freeze-thaw process. Concrete in old structures may not have air-entrained admixtures. Chlorides, carbon dioxide, sulfates, and other contaminants can damage concrete, depending on concrete quality and service exposure.  

Reclamation experience has shown that certain portions of a structure are more vulnerable to deterioration than others. These include exposed surfaces of the top of walls, piers, posts, handrails, and parapets; all of the curbs, sills, ledges, copings, cornices, and corners; and surfaces in contact with spray or water at frequently changing levels during freezing weather. The service life of these portions of structure can be extended by protective measures such as weatherproofing using concrete sealing compounds. 

Penetrating sealers such as silanes, siloxanes, and blended products, are considered a cost-effective product that can be used to protect concrete from aggressive chemicals. These compounds can be applied for existing and new structures. These will serve as chloride screens and dampproofing. The proper using of these sealers will protect the reinforcement damage caused by corrosion and the concrete deterioration due to freeze and thaw process.

High molecular weight methacrylate (HMWM) and suitable low viscosity epoxies are Reclamation's choice for sealing concrete that has small cracks on its surface (von Fay and Pepin, 2013). Low viscosities are needed for these products to be effective, and viscosities should be below 200 centipoise (cps). Suitable epoxies are available that have viscosities below 100 cps, and many HMWMs have viscosities below 50 cps. Epoxies will tend to work better than HMWMs in damp cracks, but the mixture proportions must be closely followed. HWMWs can be mixed at somewhat different ratios, which can be used to adjust the set time. These materials are very useful in “gluing” the small cracks together and keeping water out of the concrete. For the existing structures, applying of sealers or repairing of cracks using HMWM or epoxies shall be performed at an early stage before the deterioration advanced. Early signs of structure deterioration such as fine cracks parallel to corner and edge of structures. The need for protection may also be indicated by pattern cracking, surface scaling or spalling, and shrinkage cracking.

Another maintenance action is the change of the facility operation to protect the concrete structure. For example,, if the structure is exposed to repeated freeze and thaw cycles. The concrete can be protected by insulation of concrete surface or by keeping the critical part of concrete underwater in cold weather knowing that concrete underwater doesn't freeze or by varying the depth of water to avoid the concentration of freeze and thaw cycle in one elevation of concrete. The damage of the structure in figure no:2 could be reduced if the level of water varied.
Figure 2

Concrete in contact with high-velocity water will experience a different mood of damage. Holes and joint offset will tend to widen and create cavities in the concrete surface. Holes and joint offset should be repaired and eliminated. Also, any observed cavity should be repaired before it enlarged. No material will stand up to cavitation indefinitely; therefore, the long-term solution is to manage the flow to avoid conditions that will cause cavitation.

Another form of damage resulting from flowing water is abrasion erosion. Flowing water, even at velocities too low for cavitation damage, can wear away or also destroy concrete structures by the impact and grinding action of silt, sand, and rock carried in the water.


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