Concrete Repair and Structural Strengthening

Factors such as Excess concrete mix water, Faulty Design, Construction defect, Sulfate deterioration, Alkali aggregate reaction, Deterioration caused by cyclic freezing and thawing, abrasion-erosion damage, Corrosion of reinforcement steel and cracks are the causes of concrete damage. The process of replacement or correction deteriorated, damaged, or faulty materials, components, or elements of a concrete structure is called concrete repair. To perform meaningful evaluations and successful repairs the following seven steps shall be taken. Step 1: determine the cause of damage, Step 2: Evaluate the extent of damage, Step 3: determine the need to repair, Step 4: choose an appropriate repair system, Step 5: prepare the old concrete, Step 6: apply the repair systems, Step 7: cure the repair properly.

 The process of restoring the capacity of weakened components or elements to their original design capacity, or increasing the strength of components or elements of a structure, used for retrofitting or seismic rehabilitation of existing buildings, is called structural strengthening. Structural strengthening techniques are used  in local actions consisting of insertion of a new lateral force-resisting component (such as add new shear walls, braced frames, or moment frames to an existing building, …) or enhancement of the seismic resistance of an in-situ component (such as FRP Strengthening, steel or concrete jacket, interior or exterior reinforcing, … ) in an existing building. Techniques to reduce demand on the seismic system by modification of dynamic response of a structure are also included in this class.

The strengthening or retrofitting of existing concrete structures to resist higher design loads, correct strength loss due to deterioration, correct design or construction deficiencies, or increase ductility has traditionally been accomplished using conventional materials and construction techniques. Externally bonded steel plates, steel or concrete jackets and external post-tensioning are just some of the many traditional techniques available. Composite materials made of fibers in a polymeric resin, also known as fiber-reinforced polymers (FRPs), have emerged as an alternative to traditional materials for repair and Rehabilitation. FRP materials are lightweight, noncorrosive, and exhibit high tensile strength. The relatively thin profiles of cured FRP systems are often desirable in applications where aesthetics or access is a concern. FRP systems can be used to rehabilitate or restore the strength of a deteriorated structural member, retrofit or strengthen a sound structural member to resist increased loads due to changes in use of the structure, or address design or construction errors. The licensed design professional should determine if an FRP system is a suitable strengthening technique before selecting the type of FRP system.

With a wealth of experiences in concrete repair and structural strengthening, MSD is providing expertise the following services:

• Assisting owners and engineers in problem identification;
• Planning, designing and executing concrete repair based on related codes and standards such as ACI 546R-04, ACI 503.4, ASTM related standards, European Standards EN 1504 and …;
• Designing of the practical and effective structural strengthening techniques and feasibility studies for each type of building based on related codes and standards such as FEMA 547, Japan standards and …;
• Consulting, designing and executing FRP systems used to strengthen concrete structures based on ACI 440-08, ISIS design manuals and …