Epoxy injection method is used to effectively repair which of the following types of cracks?

Question

Question

This question was previously asked in

RRB JE CBT 2 (Civil Engineering) ReExam Official Paper (Held On: 04 Jun, 2025)

Answer 1

Explanation:

Epoxy Injection Method

Epoxy injection is used to repair structural cracks by restoring monolithic behavior and strength.
It is ideal for narrow, dormant cracks in beams, slabs, columns, foundations, and walls where structural integrity is compromised.
The crack surface is first cleaned and sealed along its length to prevent leakage during injection.
Injection ports are installed at regular intervals, and low-viscosity epoxy resin is injected under pressure using manual or mechanical pumps.
The epoxy fills the crack completely and cures to form a rigid, high-strength bond.
Restores structural integrity without the need for surface replacement.
Penetrates fine cracks as small as 0.05 mm.
Provides excellent adhesion to concrete and steel, improving durability.

Additional InformationTypes of Cracks in Concrete Structures:

1. Dormant Cracks

Dormant cracks are inactive and stable, meaning they do not expand, close, or grow over time.
These cracks are often caused by initial shrinkage, temperature change during curing, or early settlement.
They are suitable for permanent sealing methods like epoxy injection, as no future movement is expected.

2. Active Cracks

Active cracks change in size or direction over time, due to ongoing structural stresses, thermal effects, or foundation movement.
Such cracks require flexible repair materials like polyurethane sealants or elastomeric compounds.
Epoxy is not recommended because it is rigid and can crack again under movement.

3. Expanding Cracks

These are cracks that widen progressively, often due to thermal expansion, corrosion of reinforcement, or chemical reactions like alkali-aggregate reaction.
Repair must include treatment of the underlying cause (e.g., corrosion inhibitors) and the use of flexible or movement-accommodating materials.

4. Moving Cracks

Moving cracks are a broader term that includes any crack experiencing periodic or continuous motion due to live loads, vibrations, or settlement.
These need repair systems that can accommodate movement, such as expansion joint systems or flexible sealing tapes.