Complete Guide to Concrete Repair: Cracks, Spalling & Corrosion

Concrete is the most widely used construction material in India, yet concrete repair is one of the most misunderstood areas. Many repairs fail within a year because the wrong product was chosen, or the cause of damage was not addressed. This guide explains the most common concrete damage types and how to repair them correctly.

Step 1: Diagnose the Cause First

Before buying any repair product, understand why the concrete is damaged:

Step 2: Crack Repair — Injection Grouting

For structural and non-structural cracks, injection grouting is the most effective method:

1. Mark the crack and drill injection ports at 150–300mm spacing along the crack.
2. Install injection nipples (packers) at drilled holes.
3. Seal the crack surface with epoxy paste, leaving ports open.
4. Inject Fosroc Nitofill ER (low-viscosity epoxy) or Sika Injection-451 (polyurethane for active water leaks) using a hand pump.
5. Inject from the lowest port upward. Stop when material emerges from the next port. Cap and move on.
6. Allow 24 hours for full cure before removal of nipples.

Step 3: Spalling Repair — The Right Way

Spalling is caused by corroding rebar expanding inside the concrete. Simply patching the surface will fail within months. The correct process:

1. Remove all loose, carbonated and delaminated concrete by chipping. Minimum 20mm behind exposed rebar.
2. Clean rebar with wire brush or abrasive blasting to remove all rust. Apply rust remover: Fosroc Reebaklens RR.
3. Apply corrosion-inhibiting coating to rebar: Fosroc Nitoproof 31 or Sika FerroGard 903 (penetrating inhibitor).
4. Apply bonding agent to the concrete substrate: Fosroc Nitobond EP or Sika Armatec 110 EpoCem.
5. While bonding agent is still tacky, apply repair mortar: Fosroc Nitomortar FC, Sika MonoTop 612 or BASF Emaco S150.
6. Finish and cure with wet hessian or curing compound for 7 days.

Step 4: Honeycombing Repair

For shallow honeycombs (less than 25mm deep): clean the cavity, apply Fosroc Nitobond SBR as a bonding slurry, then fill with Fosroc Renderoc GP or Sika MonoTop 612. For deep voids (>50mm), use a flowable micro-concrete or precision grout like Fosroc Conbextra GP2.

Recommended Products