The Impact of Concrete Cancer on Central Texas Pools

Concrete cancer sounds dramatic, and for a pool owner it can be. It describes what happens when the steel rebar that reinforces a gunite pool shell begins to rust. Steel expands as it corrodes, and that expansion cracks the concrete around it from the inside, eventually flaking off chunks of the surface in a process engineers call spalling.

Central Texas pools face a specific mix of conditions that make this worth understanding before it becomes an expensive repair.

Why Central Texas pools are especially at risk

• Expansive clay soils around Austin swell and shrink with moisture, stressing the shell and opening hairline cracks that let water in
• Hard, mineral-rich local water and high summer evaporation push chemistry out of balance quickly
• Low pH or high chloride levels strip the protective layer around the rebar and accelerate rust
• Long, hot swimming seasons mean more chemical demand and more chance for neglect between services

Warning signs to watch for

• Rust-colored stains bleeding through the plaster, often in streaks or spots
• Cracks that follow a straight line, hinting at the rebar grid underneath
• Bubbling, flaking, or chunks of surface lifting away (spalling)
• Exposed rusty steel visible in cracks or at the pool edge
• Rough, pitted patches that keep getting worse despite resurfacing

How to prevent it

Prevention is far cheaper than repair. The two biggest levers are water chemistry and construction quality.

• Keep pH, alkalinity, and calcium hardness balanced year round, not just in summer
• Address cracks and surface damage promptly instead of waiting for the next resurface
• Ensure proper drainage around the pool so clay soil stays as stable as possible
• Choose a builder who uses adequate rebar cover and quality gunite application from the start

Can concrete cancer be repaired?

Yes, when it is caught before the damage spreads. Repair involves removing the failed concrete, cleaning and treating or replacing the corroded steel, and rebuilding the shell with bonding agents and new gunite or specialized repair mortar before resurfacing.

The longer it goes unaddressed, the more of the shell is affected and the more the repair costs. A localized fix is manageable; a shell-wide failure can rival the cost of a partial rebuild. If you see rust bleed or spalling, have it assessed before another season passes.

How it differs from ordinary staining

Not every rust-colored mark means concrete cancer, and it's worth knowing the difference so you neither panic nor ignore a real problem. Surface stains from metals in the water or from a nearby iron object sit on top of the plaster and can often be treated chemically or polished out. Concrete cancer, by contrast, bleeds up through the surface from the steel inside and is usually accompanied by cracking or spalling that gets worse over time.

If a stain keeps returning after cleaning, follows a straight line, or comes with a rough patch that's lifting, treat it as a structural warning rather than a cosmetic one and have it looked at.

Buying a home with an older gunite pool?

If you're purchasing an Austin home with an existing gunite pool, it's wise to have the shell inspected as part of due diligence, the same way you would the roof or foundation. An older pool that's been neglected chemically can be developing rebar corrosion that isn't obvious at a glance, and catching it before you buy lets you budget for repair or negotiate accordingly. A pool professional can assess the surface, check for telltale rust bleed and cracking, and give you a realistic picture of the shell's condition.