“Concrete cancer”, technically called spalling, or alkali-silica reaction (ASR) in its chemical form, is a problem that affects a significant portion of older in-ground concrete pools across Newcastle and Lake Macquarie. The Hunter’s coastal climate, salt air, and historically variable concrete mix quality have made concrete cancer a very common diagnosis in pools built between the 1960s and 1990s. When a pool inspector or builder tells you your pool has concrete cancer, the first question is: repair or remove? This guide helps you make that call with clear, locally-specific information. For the broader repair vs removal decision, see our guide on cracked and leaking pools: repair or remove?
Quick answer (BLUF)
Minor to moderate concrete cancer (surface spalling, isolated areas) can be repaired at a cost of $3,000 to $12,000 depending on extent. Severe or structurally compromised concrete cancer, where rebar is exposed and corroding throughout the shell, typically makes repair uneconomical, and removal at $8,000 to $18,000 is the better long-term decision. The key question is: how deep does it go?
What is concrete cancer in a pool context?
In a swimming pool, “concrete cancer” typically refers to one or more of:
Rebar corrosion and spalling: The steel reinforcement inside the pool shell corrodes (from water intrusion through cracks, poor cover depth at original construction, or chloride ingress). Corroding steel expands, cracking and lifting the surrounding concrete (“spalling”). You see chunks of concrete falling off walls and the base, with rusty stains and exposed steel.
Alkali-silica reaction (ASR): A chemical reaction between certain aggregates in the concrete and the alkaline pore water. It forms a gel that absorbs water and expands, cracking the concrete from within. ASR-affected concrete has a characteristic map-cracking or crazing pattern.
General deterioration: Poor original mix design, inadequate water-cement ratio, or insufficient curing creates concrete that degrades faster in a wet, chemically active environment. This is common in pools built by owner-builders or budget contractors in the 1970s, 80s Hunter market.
Diagnosing the severity: what to look for
An experienced pool inspector or concrete technologist can assess severity:
Surface-only spalling: Concrete is lifting or pitting in isolated areas, but the rebar is not yet exposed or is just barely visible. The pool structure is still sound. This is repairable.
Exposed rebar with localised corrosion: In specific areas (often the waterline band, the deep end floor, or around inlets and returns) the rebar is exposed and staining the concrete with rust. Still repairable but with more extensive prep work.
Widespread rebar exposure and loss of cover: Corrosion is evident across a large proportion of the shell. The concrete cover has completely lost integrity in multiple locations. Structural testing would show reduced load capacity. Repair is technically possible but very expensive and uncertain in outcome.
Through-wall cracking: The shell has cracked through its full thickness, allowing water to seep through. The pool is actively leaking at the structural level. For concrete cancer cases with through-wall cracking, repair viability drops significantly.
What does concrete cancer repair actually involve?
For repairable cases, the process is:
- Drain the pool completely
- Wire brush, grind or hydrodemolish all affected areas to remove all deteriorated and contaminated concrete
- Treat exposed rebar with corrosion inhibitor and, where severely corroded, replace or supplement the rebar
- Apply a patching mortar with steel reinforcement fibres or polymer-modified concrete to restore the section
- Apply a waterproofing membrane over the full interior
- Retile or apply a new surface finish (pebblecrete, marble plaster, glass bead finish)
This is specialist work. Concrete repair in a pool environment must use the correct products, standard render or patch mortars are not adequate for a permanently wet, chemically active environment. The Hunter has several pool renovation specialists who understand this; get multiple quotes and check product specifications.
Cost comparison: repair vs removal
| Scenario | Concrete Cancer Repair | Full Pool Removal |
|---|---|---|
| Minor spalling (< 10% of surface) | $3,000 to $6,000 | $8,000 to $18,000 |
| Moderate (10-30% of surface) | $6,000 to $12,000 | $8,000 to $18,000 |
| Severe (>30% or through-wall) | $12,000 to $25,000+ | $8,000 to $18,000 |
| Expected service life after repair | 5-15 years | N/A, permanent solution |
In severe cases, the repair cost exceeds removal cost, and even after repair, the underlying concrete quality issue hasn’t been resolved. Another round of spalling in 5-10 years is common if the root cause (water ingress, inadequate cover, ASR) is not fully addressed.
Hunter Valley-specific factors
Newcastle and the Lake Macquarie foreshore are high-humidity, coastal environments. Salt-laden air accelerates chloride ingress into concrete, which accelerates rebar corrosion. Pools within 1km of the coastline, Merewether, Bar Beach, Redhead, Swansea, are particularly prone to early concrete cancer compared to inland suburbs.
Pools built in the 1970s, 80s often had shallower concrete cover (15-25mm over rebar, rather than the 40-50mm now specified) and used higher water-cement ratios, making them more permeable. These structural characteristics mean a higher proportion of pools from this era show significant concrete cancer symptoms.
The financial decision
The key financial question is: what is the total cost of repair vs removal, adjusted for the likely service life of each option?
- Repair minor concrete cancer at $5,000 now → pool may last another 10-15 years before the next intervention
- Remove pool at $12,000 now → permanent solution, backyard reclaimed, ongoing costs eliminated
For owners who love their pool and want to continue using it, well-executed repair is a valid choice for minor-moderate cases. For owners who are already ambivalent about the pool, severe concrete cancer is often the final push toward removal, the economics clearly favour it.
FAQs
Can I DIY repair concrete cancer in my pool?
Not effectively. Concrete cancer repair in a pool environment requires correct product selection, surface preparation to bare sound concrete, and rebar treatment. Incorrect repairs using standard cement products will fail within 1-3 years in the wet-pool environment. Always use a qualified pool renovation or concrete repair specialist.
How do I know if my pool’s concrete cancer will get worse quickly?
The rate of deterioration depends on the severity of water ingress and rebar corrosion. An inspector with a rebound hammer or ground-penetrating radar can give you a more precise picture. As a rough guide: if you’re seeing new spalling each season, or if the pool has been leaking for more than 2 years, deterioration is likely accelerating.
Does pool removal cost more if the concrete is in a very deteriorated state?
Not necessarily. Severely deteriorated concrete is actually easier to break than sound concrete, a hydraulic breaker works faster on compromised material. Pool size, site access and volume of material are more important cost factors than concrete quality.