India has witnessed a tremendous spurt in construction over the last couple of decades. Residential, Commercial, Industrial and Infrastructure construction and expansion has been progressing at an all time high. RCC has been a material of choice in expanding our construction horizon and is the second most used resource in the world after water. RCC, a combination of concrete and reinforcing steel, is a resultant system that is quite vulnerable to damage considering the deterioration of concrete due to its porosity and the resultant deterioration of steel due to attack by water, carbonation, chlorides or a combination thereof. The system deteriorates further due to cyclic action of these mechanisms.
Coupled with accelerated construction schedules, it becomes difficult to cast the specified cover to the reinforcement in terms of quality or quantity. Therefore, the process of deterioration begins almost immediately after the casting. Since cover is the first line of defense to inhibit corrosion, repair and rehabilitation is the process of recreation of cover with the highest protection quotient. We, therefore, need to use the latest technologies like polymers, fibers, etc. to lower the permeability, minimize the cracks and provide adequate bonding, to stop further deterioration. Given actual working conditions, it is difficult to create a cover that will be resistant to carbonation or chloride ingress. To remove this lacuna from the system, it is preferable to provide a protective coating working on principles of equivalent cover to ensure durability of repairs.
Defects and damage occurring in concrete structures can be ascribed to varying causes, which frequently overlap. Table 1 taken from EN 1504 provides an excellent guideline summary of possible causes of concrete deterioration. Other factors, of course include higher mechanical, chemical, thermal and biological loads. Another area of concern is the durability of the repairs themselves. Generally, problems with the effectiveness of repairs have been as common as the repair materials themselves. In spite of several researches in the field, the need for common understanding of performance requirements for repair materials and suitable methodologies has been felt all along. Figure 1 shows the factors affecting the durability of repairs.
Internationally, over the past decades the understanding of technical performance requirements of concrete repair and protection products has increased significantly. The new European Standard EN 1504 represents the culmination of over 15 years of consultation and inputs by professionals from all sectors of the concrete repair industry. EN 1504 was an attempt to bring in specifications based on performance properties of repair materials and also suggests the repair methodologies for a variety of situations. This article enumerates the steps for concrete rehabilitation in accordance with proven international standards.