Durability Repairs are Carried out to structures which show deterioration to non-structural area of concrete. Some of the findings of structure signifying requirement of durability repairs are:

• Cover Concrete is spalled in Columns, Beams, Slabs, other elements
• Chajjas / Pardi’s and other non-structural members exhibit damages
• Core Concrete (concrete inside rebar) is sound and intact.
• Façade needs to be replaced – New plasters and coating
• Tiles & other Finishes need replacement / repairs
• Cover concrete is rebuilt using PMM / Shotcrete
• Chajjas / Pardi’s are replaced with new members or are repaired using variety of materials

Structural Repairs are Carried-out to structures which exhibit structural damage in the core section of the concrete. Some of the findings of structure signifying requirement of Structural repairs are:

• Reduction in rebar > 20% Loss
• Spalling/damage/buckling of core concrete
• Main structural members such as columns, beams and slabs which form an integral part of the framework are damaged in core zone
• Core Concrete needs replacement including addition of new rebars
• Jacketing of foundations/Columns/Beams and Slabs
• Micro-concrete / Self-compacting concrete / Polymer modified Concrete/ FRP’s / Structural Steel / Ground Improvement / Micro Piles etc.

Structural Strengthening is carried out in situations wherein there is a change in user requirements e.g. residential structure getting converted to commercial premise. New vertical loads being added, such as addition of floors, new loads such as chillers, cooling towers, Antenna’s being added on top of existing premises

• Usual strengthening practices involve strengthening by section enlargement using micro-concrete, Polymer modified Concrete, SCC, Steel plates / Sections and FRP’s
• Involves detailed redesign of the existing framework using strength of various elements.

Seismic Retrofitting Buildings designed prior to 2002 may-not comply to Codal provisions of revised IS codes. To protect the old structures, from the effect of seismic forces, Specialized retrofitting process for to counter seismic forces involves:

• Addition of Shear Walls
• Introduction of Lateral Ties
• Jacketing of Columns / Beams
• Strengthening of Column / Beam junctions

Corrosion in concrete occurs when the protective layer in concrete steel reinforcement is deteriorated. Steel in concrete is usually protected against corrosion by the high pH of the surrounding portland-cement paste. Cement paste has a minimum pH of 12.5, and steel will not corrode at that pH. If the pH is lowered (to pH 10 or less), corrosion will start occuring if moisture, oxygen, and chloride ions are present in the environment. Chloride ions destroy the protective layer on the steel reinforcement, making it prone to corrosion. The signs of corrosion present in concrete are:

• spalling of concrete and exposed corroded reinforcement
• uniform cracks development in the RCC members
• chloride content in excess of 0.6 as limit specified in per IS456:2000

Corrosion mitigation of concrete structures is essential to restrict the deterioration of structure by taking up following:

• repairs of existing damaged structure by using anti-corrosive treatment
• providing corrosion inhibiting coatings to new and old reinforcement
• repairs with polymer / epoxy mortar application
• provide corrosion inhibiting caplets / galvanic anodes to restrict corrosion