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Concrete Pools

Most in ground pools in Australia are made of concrete. They age well but overtime can be subject to a range of issues.  The pool will generally have a concrete shell (with steel reinforcement) with a smooth render on top.

The general effects of aging concrete pools are: (mild to worse)

  • Some hair line cracking
  • Worn areas
  • Stains
  • Rust stains
  • Lifting or drummy areas
  • Algae difficult to control
  • Concrete cancer
  • Major cracks and leakage

As with all structures they need looking after so they continue to perform as designed and not fail catastrophically. By keeping the maintenance up this will go a long way to keeping it all together for the long run.

One of the worst things is to ignore minor issues and then let them become major ones which may then cost a lot to repair.

So if you see signs of:

  • Cracking,
  • Worn surfaces
  • Algae attack
  • Rust stains
  • Drummy areas

Seek good advice as to how to deal with the matters at hand.

Generally cracking (minor) is the result of age or maybe settlement and may well allow water to penetrate into the concrete structure. If your pool is salt water this is of greater concern as there is the prospect of the water causing fast rusting of the reinforcement steel buried within the concrete. The outcome is at best some concrete cancer and at worst, a major structural issue. So don’t ignore minor crack as they can lead onto major issues.

Worn areas may occur where the render is thin and is subject to much foot traffic like on edges of steps, swim outs and maybe around some fittings.

Stains are the usually the result of mineralisation (from pool water), pools chemicals, leaves, bottle tops and algae growth. The algae growth is indicative of the cement surface becoming worn, porous and harbouring deep ingrained algae roots which are hard to kill.

Rust stains are a concern in that below the surface of the concrete the reinforcing steel is likely corroding away and becoming weakened in the process. Depending on the extent of this, the design of your pool and the rate of corrosion (which one cannot see readily from the surface) it may pose a significant issue. Best to have it attended promptly as any delay will usually result in greater expense.

Lifting or Drummy areas are where the render (or smooth concrete surface) has become detached from the underlying structure. It can happen in older pools and the cause is quite varied but may generally be considered something to do with age, water ingress (concrete is not water proof) and poor construction techniques. In order to protect the pool such areas should be investigated thoroughly and repaired with the correct materials, sooner than later.

Algae that is difficult to control is a result of poor water management and may often also be the result of a porous, rough, absorbent surface as with aged concrete. Even if the pool surface was smooth at the time of construction, pool water chemicals (Acid especially) eat away at the cement surface. They create a pitted, creviced surface which is the ideal home for algae in all forms to take hold and thrive. Simply pouring chemicals into your pool will only knock the algae back, but not kill it as the roots are deeply imbedded in the concrete.

Concrete cancer is a severe form of attack and is the result of the corrosion of the steel within the concrete, its expands as it does so and the fact it pushes the concrete further apart allowing more water in and increasing the rate of failure. Ultimately it can lead to structural failure and as most pools hold anywhere from 40 – 80 tonnes of water, it’s not a good idea to leave unattended.

Major cracks and leakage can be the result of some of the above factors but also of pool settlement or movement. This is often observed in clay soils which when normally moist, then go through a drought, and thus compact (shrink back) and maybe take part of the pool with them. Also it can show up after the drought is broken when the soils swell unevenly causing stresses on the pool which it cannot resist as a whole and cracks in some places. We often see two vertical cracks in the long walls about where the deep end changes to the mid depth and the cracks are opposite each other. They are often wider at the top…2 – 10 mm and fade to zero near the bottom.

The issues raised above can be difficult to understand or see when the pool is full, however if by careful observation you see some or all of these items seek good advice rather than leave them to fester.

Once any (or all) of the issues have been attended to then it would be a good idea to resurface your pool and a way to do this is using Epotec hi build epoxy coating. This will provide a smooth, long lasting, easy clean surface that will resist algae attack and be attractive for years.

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