Concrete Problems & Maintenance

Context

Concrete in Australian Conditions

Australia's climate extremes place unique demands on concrete — from temperature swings of -5°C to 45°C+, intense UV, coastal salt, reactive clay soils, and bushfire exposure.

🌡️ Climate Challenges

Temperature swings cause expansion/contraction
Intense UV exposure in northern regions
High humidity in tropical areas promotes mold
Freeze-thaw cycles in southern regions

🌏 Environmental Factors

Coastal salt exposure accelerates deterioration
Clay soils expand and contract with moisture
Bushfire exposure in rural/semi-rural areas
Heavy rainfall and flooding events

Diagnosis

Common Concrete Problems

1. Concrete Cracking

Cracking is the most common concrete problem. While some hairline cracks are normal, understanding crack types helps you know when to worry.

Low Concern

Plastic Shrinkage Cracks

Fine, shallow cracks appearing within first few hours. Caused by rapid moisture evaporation during curing. Prevent with proper curing and wind protection.

Low Concern

Drying Shrinkage Cracks

Random pattern, shallow cracks in first weeks–months. Normal concrete shrinkage as it cures. Prevent with control joints and proper mix.

Cosmetic

Map Cracking (Crazing)

Fine spider web pattern on surface only. Caused by rapid surface drying or poor finishing. Purely cosmetic — no structural concern.

Medium Concern

Thermal Cracks

Long, straight cracks from temperature differentials. Prevent with temperature control during pour and adequate expansion joints.

High Concern

Settlement Cracks

Wide cracks with step patterns appearing months–years later. Indicates poor soil compaction or erosion — structural issues.

Very High

Structural Cracks

Wide (>3mm), worsening cracks from overloading or inadequate reinforcement. Immediate professional attention required.

Crack Width	Action	Urgency	DIY?
Hairline (<0.5mm)	Monitor, seal if desired	Low	Yes
Minor (0.5–2mm)	Seal to prevent water ingress	Low–Medium	Yes
Moderate (2–5mm)	Professional assessment	Medium	Professional preferred
Major (>5mm)	Immediate professional assessment	High	No
Active (widening)	Immediate professional assessment	Very High	No

2. Concrete Spalling

Surface breaking away or flaking off, exposing aggregate or reinforcement. Most commonly caused by reinforcement corrosion (especially coastal areas), freeze-thaw cycles, poor-quality concrete, and chemical exposure.

🔧 Small Area Repair (<1m²)

Remove all loose concrete, clean exposed reinforcement
Apply rust converter/primer to any exposed steel
Apply bonding agent, patch with repair mortar
Feather edges, keep moist 7 days
Cost: $150–$400/m² (DIY materials ~$40–$80/m²)

⚠️ Large Area (>1m²)

Professional assessment required
May need concrete removal and replacement
Structural reinforcement may be necessary
Cost: $200–$600+/m²

3. Surface Discoloration & Staining

⬜

Efflorescence

White powdery deposits from salts migrating with moisture. Brush off when dry and seal concrete to prevent recurrence.

🟤

Rust Stains

Brown/orange streaks from metal objects or reinforcement corrosion. Use oxalic acid solutions or commercial rust removers.

⬛

Oil Stains

Dark patches from vehicle leaks. Absorb fresh spills with cat litter, then degrease. Seal concrete and clean spills immediately.

🟢

Mold & Mildew

Green/black patches in shaded, moist areas. Clean with diluted bleach (1:3) or mold killers. Improve drainage and seal.

4. Surface Deterioration

Includes scaling (rough surface from freeze-thaw; fix with overlay at $35–$80/m²), dusting (powdery surface; apply concrete hardener at $20–$40/m²), and pop-outs (cone-shaped holes from reactive aggregate; fill with repair mortar).

5. Slab Settlement & Movement

Signs include uneven surfaces, edge cracking, doors/windows sticking, and water pooling in new areas. Caused by poor soil compaction, erosion, tree roots, or reactive clay soils.

💉

Slab Jacking

Inject grout mixture beneath slab to lift sunken areas. Best for settlement <50mm with intact slab.

$800–$2,500 per area

🧪

Polyurethane Foam

Expanding foam injection — lighter and faster setting than mud jacking. Suitable for any settlement level.

$1,200–$3,500 per area

🔨

Full Replacement

Remove and re-pour concrete, addressing underlying soil issues. For extensive cracking or settlement >75mm.

$90–$180/m²

6. Colour Fading (Decorative Concrete)

UV exposure, weather, and poor-quality pigments cause fading in coloured, exposed aggregate, and stamped concrete. Prevent with UV-stable pigments and quality sealers. Restore with concrete stain and re-seal ($30–$60/m²).

Repairs

Repair Methods

DIY Repairs (Minor Issues)

Hairline Crack Repair

$10–$30 materials • 30–60 min

Clean crack with wire brush, vacuum dust, apply crack filler with caulking gun, smooth with putty knife, cure per instructions.

Small Spall Repair

$25–$60 materials • 1–2 hours

Remove loose concrete, clean area, apply bonding agent, press repair mortar firmly into hole, feather edges, keep moist 24–48 hrs.

Clean & Seal (40m² Driveway)

$80–$150 materials • 4–6 hours

Remove debris, apply cleaner, pressure wash, dry 24–48 hrs, apply sealer in thin even coats with roller or sprayer.

Professional Repairs (Major)

Epoxy Injection (Structural)

$200–$800 per crack

For cracks >3mm, structural concerns, or active water ingress. Restores structural integrity with permanent, warranted repair.

Concrete Resurfacing

$40–$120/m²

Spray-on ($60–$100/m²), micro-topping ($70–$120/m²), or epoxy coating ($40–$90/m²). Covers imperfections with a new decorative surface.

Full Slab Replacement

$90–$180/m²

When cracks cover >50%, settlement is severe, or multiple repairs have failed. Addresses underlying soil/drainage issues.

Schedule

Preventative Maintenance Schedule

Every 3 Months

Visual Inspection & Basic Clean

Check for new cracks and surface damage
Inspect for water pooling and expansion joints
Sweep debris, remove weeds from joints
Clean any stains promptly, rinse with hose

⏱️ 15–30 minutes

Every 6 Months

Thorough Clean & Assessment

Pressure wash entire surface
Remove oil stains, clean drainage areas
Measure existing cracks and note widening
Photograph for records, seal new hairline cracks

⏱️ 2–3 hours

Annually

Deep Clean, Seal & Joint Check

Professional-grade pressure washing
Repair minor cracks, apply concrete sealer
Ensure proper drainage and water flow
Inspect and reseal expansion joints

⏱️ Full day • $200–$500 DIY

Every 2–3 Years

Re-Sealing & Professional Check

Strip old sealer if needed, deep clean
Apply 2 coats quality sealer (UV-resistant for decorative)
Professional structural assessment if concerns

Pro: $8–$15/m² • DIY: $3–$6/m²

Every 5–10 Years

Major Maintenance

Consider resurfacing if worn
Repair all accumulated damage
Re-grind and seal polished concrete
Restore colour to decorative finishes

$2,000–$10,000+ depending on scope

By Type

Maintenance by Concrete Type

Concrete Type	Key Tasks	Re-Seal	Annual Cost (40m²)
Plain Grey	Pressure wash, seal with penetrating sealer, repair cracks	2–3 yrs	$150–$400 DIY
Exposed Aggregate	Pressure wash (moderate), pH-neutral cleaner, wet-look or matte sealer	2–3 yrs	$250–$500
Stamped/Coloured	Gentle clean, UV-resistant sealer, colour touch-ups	2–3 yrs	$300–$600
Polished (100m²)	Weekly dust mop, damp mop neutral pH, annual deep clean	2–3 yrs	$200–$400

Seasonal

Seasonal Maintenance Tips

☀️ Summer

Water concrete in extreme heat (>35°C)
Seal before summer to protect colour
Check expansion joints for thermal movement
Monitor for thermal cracking

🍂 Autumn

Clean and seal before winter
Repair all cracks (water in winter worsens damage)
Clear leaves and debris, ensure drainage is clear
Clean gutters to prevent overflow onto concrete

❄️ Winter

Keep surface clean and dry when possible
Avoid de-icing salts (use sand for traction)
Remove snow/ice with plastic shovel, not metal
Monitor for new cracks, ensure drainage works

🌱 Spring

Thorough inspection for winter damage
Pressure wash and clean entire surface
Repair cracks, re-seal if needed
Remove weeds, check for settlement

Special Cases

Special Maintenance Situations

🌊

Coastal Areas

Salt accelerates corrosion and spalling. Rinse with fresh water monthly (weekly near ocean), seal every 1–2 years with marine-grade sealers, and ensure 75mm+ concrete cover over reinforcement.

🏜️

Clay Soil Areas

Reactive soils cause seasonal movement and cracking. Monitor cracks closely, maintain consistent soil moisture with soaker hoses, ensure excellent drainage, and get professional inspections every 2–3 years.

🚗

High-Traffic Areas

Accelerated wear demands weekly sweeping, annual sealing (not 2–3 yearly), immediate stain treatment, and re-finishing high-wear areas every 5–7 years. Consider hardener for garage floors.

Decision Guide

When to Call a Professional

✅ DIY Appropriate

Hairline cracks (<1mm)
Minor surface stains
Regular cleaning and sealing
Small spall repairs (<100mm diameter)
Cosmetic improvements
Routine maintenance tasks

⚠️ Professional Required

Structural cracks (>3mm or widening)
Extensive spalling (>1m² or deep)
Settlement or levelling issues
Water infiltration problems
Reinforcement corrosion
Cracks in house slabs or foundations

Products

Recommended Products for Australian Conditions

🛡️

Penetrating Sealers

Best for driveways and functional areas. Natural appearance, breathable, re-seal every 3–5 years.

Brands: Chemtech CT7, Aqua Mix Sealers Choice Gold

✨

Topical Sealers

Best for decorative concrete — enhances colour, water-resistant. Re-seal every 2–3 years.

Brands: Euclid Chemical, Boral Sealers

💪

High-Performance

Epoxy/polyurethane for garages and commercial. Extremely durable, chemical resistant. Re-seal every 5–7 years.

Brands: Crommelin, Gripset

🔧

Repair Materials

Flexible polyurethane sealants (moving cracks), rigid epoxy (dormant structural), quick-setting patching compound.

Brands: Sika, Dunlop, Gripset, Ardex

FAQ

Frequently Asked Questions

Plain concrete: every 3–5 years. Decorative concrete: every 2–3 years. High-traffic areas: annually. Coastal areas: every 1–2 years. Use quality sealers for longer intervals.

Yes, for hairline to minor cracks (<2mm). Use flexible concrete crack filler. For cracks >2mm or structural concerns, professional assessment is recommended. Active (widening) cracks always need professional evaluation.

Minor hairline cracks are normal from shrinkage as concrete cures. Excessive cracking may indicate inadequate control joints, poor curing, rapid drying, insufficient reinforcement, or soil settlement. Monitor crack width and consult your concreter if concerned.

Fresh stains: absorb with cat litter, then degrease. Old stains: apply commercial concrete degreaser, scrub vigorously, pressure wash. Stubborn stains may require repeated treatments or professional cleaning.

Yes. Spalling indicates concrete deterioration and often reinforcement corrosion. Small areas can be patched, but extensive spalling may require professional repair or replacement. Untreated spalling worsens rapidly, especially in coastal areas.

Consider replacement when cracks cover >50% of surface, settlement is severe (>75mm), extensive spalling throughout, multiple failed repairs, or structural failure. Professional assessment helps determine the best option.

Yes, but use moderate pressure (1500–2000 PSI) and keep nozzle at least 300mm from surface. Too much pressure can dislodge aggregate stones. Clean in sweeping motions, not concentrated on one spot.

UV exposure, weather, and wear cause fading. Quality UV-resistant sealers slow this process. Restore colour with concrete stains or colour-enhancing sealers. Re-seal regularly to protect from further fading.

Resources

Explore More Concreting Resources

📘

Types of Concreting ServicesComplete guide to all services

💰

Concreting Costs GuideDetailed pricing by state

📋

Licensing & RegulationsState-by-state requirements

🎨

Design & Finishes GuideExplore all finish options

🏠

Main Concreters HubComplete concreting resource