How do I choose between an epoxy and a cementitious repair mortar?

Use epoxy for high-strength structural bonding like crack injection where moisture is controlled. Use cementitious mortars for general spall repair as they are more compatible with concrete and easier to apply. See Table 1 for guidance.

What is the most important property for a repair material?

Good bond strength to the parent concrete and dimensional compatibility (low shrinkage and similar thermal expansion) are the most critical properties for a durable repair, as outlined in Clause 5.

Does this code provide a list of approved products?

No, this is a performance-based guideline. It specifies the required properties a material should have for a given application, but does not endorse or list specific commercial products.

What is the first step in any concrete repair project according to this standard?

The first and most crucial step is the diagnosis of the cause and extent of the damage, as detailed in Clause 4 and Annex B. Without a correct diagnosis, the selected repair may not be effective.

IS 13642

: 1993

Recommendations for Selection of Repair Materials for Concrete Structures

CurrentSpecializedGuidelinesStructural Engineering · Demolition, Renovation and Repair of Structures

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This standard provides guidelines for the diagnosis of damage in concrete structures and the selection of appropriate repair materials. It details the desirable properties for repair materials, such as bond strength, compatibility, and durability, and offers a framework for choosing the correct material and system for various types of defects.

Provides recommendations for the selection of appropriate repair materials for different types of concrete structures and defects.

Quick Reference Values

Minimum bond strength (pull-off test)1.5 N/mm²

Coefficient of thermal expansion compatibilityShould be within 5 x 10⁻⁶ /°C of the parent concrete

Drying shrinkage limit for cementitious mortars< 0.1 %

Water permeability requirementShould be significantly lower than parent concrete

Chloride ion permeabilityShould be 'Very Low' as per standard test methods for durable repairs

Practical Notes

A thorough diagnosis of the root cause of deterioration is critical before selecting a repair material. Simply patching a spall without addressing active corrosion will lead to recurring failures.

Compatibility of the repair material with the parent concrete (in terms of thermal expansion, elastic modulus, and electrochemical properties) is paramount to ensure long-term performance.

Proper surface preparation, including removal of all unsound concrete and cleaning of reinforcement, is as important as the repair material itself for achieving a durable bond.