What is the difference between R4 and R3 grade repair mortar?

R4 has higher performance requirements, including a minimum 28-day compressive strength of 45 MPa and bond strength of 2.0 MPa, compared to 30 MPa and 1.5 MPa for R3 respectively (Table 2).

Can I use these materials for overhead repairs?

Yes, but you must select a material specifically designed with thixotropic (non-sag) properties, which is a key requirement for vertical and overhead applications (Clause 5.2.1).

What is a 'PCC' class mortar?

PCC stands for Polymer Cement Concrete/Mortar. In this standard, PCC-I, II, and III are classes for non-structural repair mortars, typically used for cosmetic repairs or rendering (Table 3).

Is bond strength a mandatory test for structural repairs?

Yes, for structural repair mortars (R1 to R4), pull-off bond strength is a mandatory performance requirement as per Table 2.

IS 16595

: 2017

Performance specifications for micro-concrete and polymer-modified mortar for repair and rehabilitation of concrete structures

CurrentSpecializedSpecificationBIMMaterials Science · Admixtures and Chemical Products for Concrete

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This standard provides performance specifications for pre-packaged micro-concrete and polymer-modified mortars used in the repair of concrete structures. It classifies materials based on their intended use (structural or non-structural) and defines key properties like strength, bond, and durability to ensure quality and longevity of repairs.

Specifies performance requirements for micro-concrete and polymer-modified mortar used as chemical products in concrete repair and rehabilitation.

Quick Reference Values

Minimum 28-day Compressive Strength (Class R4)45 MPa

Minimum Pull-off Bond Strength (Class R4)2.0 MPa

Maximum Chloride Ion Content (All Classes)0.05 % by mass

Minimum 28-day Compressive Strength (Class R3)30 MPa

Minimum Pull-off Bond Strength (Class R3)1.5 MPa

Minimum 28-day Compressive Strength (Non-Structural PCC-I)10 MPa

Maximum Water Absorption (Class R4)< 5.0 %

Practical Notes

Always check the material's class (e.g., R3, R4) against the project specification. Using a non-structural mortar (PCC) for a structural repair is a critical error.

Surface preparation of the old concrete is as crucial as the repair material itself for achieving the specified bond strength.

Pay close attention to the pot life and curing requirements provided by the manufacturer, as these are critical for achieving the performance specified in this standard.