5 Most Common Concrete Defects (And How to Fix Them for Good)

1. Cracking

What it is: Fractures in concrete, either superficial or full-depth, typically caused by tensile stress.

Common Types:

• Shrinkage cracks (plastic or drying)

• Settlement cracks

• Thermal movement cracks

• Structural cracks (load-induced)

Causes:

• Poor curing practices

• Excessive water in the mix

• Inadequate reinforcement or cover

• Temperature fluctuations and restraint

• Excessive structural load

An example of a non-structural hairline crack being patched with a flexible sealant

Fix:

• Non-structural cracks: Use flexible sealants like polyurethane.

• Structural cracks: Combine epoxy injection for bonding and crack lock stitching for reinforcement.

Crack lock stitching being utilised to repair a structural crack. Highly effective at adding reinforcement across the span of the crack and preventing further movement

Visual Tip: Structural cracks often follow load paths (corners of windows, column heads) and may show step cracking in masonry.

Real-World Note: Cracking is a top complaint from strata managers in apartment building, as structural issues can have a severe impact on property valuations, the stability of the structure, and other issues that can follow such as concrete cancer and water ingress

2. Spalling

What it is: Surface layer flaking or disintegration, often exposing coarse aggregate or steel.

Causes:

• Corrosion of steel reinforcement

• Insufficient cover on reinforcement

• Chlorides penetrating the concrete (more common in environments situated close to the ocean

Fix:

• Break out loose concrete

• Clean reinforcement

• Apply corrosion-inhibiting primer

• Patch with polymer-modified repair mortar

Prevention: Adequate cover depth and water management.

Highly corroded reinforcement in a concrete beam

3. Honeycombing

What it is: Voids caused by incomplete filling of concrete around reinforcement or into corners.

Causes:

• Insufficient vibration

• Congested rebar

• Harsh or dry mix

Visual Tip: Appears as porous or “cratered” zones; common at bases of walls and columns if vibrator shaft was not dropped to the full depth of the concrete element.

Fix:

• Cut 20-30mm deep around the perimeter of the patch to eliminate feathered edges

• Jackhammer out loose material until sound concrete is reached

• Saturate surface and apply bonding agent

• Rebuild using low-shrinkage grout or structural mortar

4. Efflorescence

What it is: Concrete efflorescence is caused by water movement through concrete, which brings soluble salts to the surface. Once the water evaporates, these salts are left behind as a white, powdery deposit.

Causes:

• Presence of water-soluble salts

  • Typically found in cement, sand, aggregates, or even surrounding soil.

• Moisture ingress or movement

  • Rain, groundwater, or curing water enters the concrete and dissolves salts.

• Evaporation from the surface

  • As water migrates to the surface and evaporates, it deposits the salts.

Fix:

• Use of chemicals to clean the salts from the surface

• Products such as RadonSeal penetrates deep inside the concrete, stucco, and other cementitious substrates, to react chemically and bind the salts in place forever – effectively removing them from the equation.

• Eliminate or mitigate the source of the moisture as much as possible. Without moisture, there is no water to carry salts to the surface in the first place.

Prevention: Good use of moisture barriers, keeping water/cement ratios within spec when pouring and managing salt content prior to install of the concrete element

5. Delamination

What it is: In many cases of concrete delamination, the top 3–6 mm of the slab becomes overly dense due to premature or incorrect finishing. This dense surface layer often separates from the main body of the slab by a thin film of trapped air or moisture. These delaminated areas can vary significantly in size — from small patches to sections spanning multiple square metres. As the surface dries rapidly during curing, you might notice differences in colour or early hairline cracking. Over time, traffic loads can cause the surface to shear off in large sheets.

Although difficult to spot during finishing, delaminations usually become noticeable once the concrete has hardened and dried. A simple way to identify them is by tapping the surface with a hammer or dragging a heavy chain — a hollow/drummy sound typically indicates separation beneath the surface.

Causes:

• Finishing over bleed water

• Overworking the surface

• Long time intervals between concrete placement over a horizontal plane, forming a kind of horizontal cold joint

Fix:

• Grind/hammer off delaminated surface

• Apply bonding agent

• Resurface with polymer topping

6. Water Ingress

What it is: Moisture entering through concrete elements at the construction joints or through weak points in the concrete. To prevent water ingress, thorough planning and implementation of products must be carried out to manufacturer specs. For those in the new build stage, measures such as use of water stops at construction joints, waterproof membranes and correct admixtures can effectively prevent water ingress issues. For existing buildings, there are a variety of specialised remedial solutions that can halt water ingress.

Causes:

• Cold joints

• Honeycombing

• Tie holes and poor compaction/vibration of concrete

• Failure of waterproof membranes and vapour barriers

• Best practise products and systems not implemented during the new build stage

Fix:

• PU crack injection

• Negative side cementitious waterproof membrane

• Crystalline product application (Penetron range)

Real-World Note: Lift pits, retaining walls and basements are frequent problem areas.

How to Prevent Concrete Defects from the start

• Use proper compaction and vibration techniques

• Ensure adequate curing (7+ days moist curing recommended)

• Use quality formwork and consistent batching

• Protect pours from environmental extremes

• Integrate waterproofing early in design

• Ensure tight truck spacing when placing concrete to reduce risk of cold joints

• Plug coil ties properly

• Don’t add more than the recommended amount of water to concrete trucks

Preventative Technology: Consider admixtures like Penetron Admix for below-grade works.

When to Call a Professional

• Cracks appearing

• Signs of water seepage

• Exposed steel reinforcement

• Structural movement or tilting

• Rust stains coming through to surface

• Drummy or hollow section of concrete

TruBond Concrete Repairs offers:

• Free assessments

• Engineer-backed repair plans

• ITP documentation and reporting

• Specialisation in structural and strata works

Final Thoughts

Concrete doesn’t fail all at once—it fails gradually. The sooner you spot and fix common defects, the longer your structure lasts.

Whether you’re dealing with cracks, leaks, or concrete surface damage, TruBond Concrete Repairs can diagnose and resolve the problem for good.

Need expert advice? Book your free concrete defect inspection today and we’ll show you exactly what needs fixing—and how to fix it for good.