If you want a lifetime job, it could be painting the Sydney Harbour Bridge – once you finish you probably have to start at the other end again. The painting continues in order to stop the steel from corroding, and steel corrosion is what causes concrete decay, otherwise called concrete cancer or spalling.
How does concrete ‘decay’ ?
Concrete is used in most commercial and residential buildings in a large number of applications such as slabs, stairways, post and columns, sustain beams, balconies and verandahs, walls, pathways and pools. Huge volumes of concrete are involved in structures like bridges, wharves and high-rise towers. The concrete is generally strengthened using steel bars or mesh and in the larger developments meaningful amounts of steel are required for additional strength.
The enemies of strengthened concrete are water and air. If these elements gain access to the steel enclosed within the concrete it can corrode – the steel expands as it breaks down and fractures the surrounding concrete. As the concrete fractures and crumbles, there is already greater opportunity for water and air to contact the reinforcing steel and the time of action intensifies. There are obvious safety issues as the structural integrity of the concrete is reduced.
How to clarify concrete decay
It can be happening unseen within the concrete but as it continues it becomes more apparent. You may notice rust marks running down the concrete, or the concrete flaking, cracking or crumbling. In extreme situations, large sections of the concrete will fall away, exposing the rusted reinforcing steel. Remedial treatment can include substantial and expensive corrective measures.
A specialized building inspection can clarify the problem or warn of possible for future trouble. It can be water pooling somewhere, small fractures in the concrete or reinforcing too close to the concrete surface. Prevention is certainly better than cure with concrete decay – it may simply be a matter of improving drainage, painting a surface or sealing fractures with some sort of mortar or epoxy filler. If you have any concerns about concrete decay, it pays to get some expert advice.
I do like to be beside the seaside
Well yes, most of us do but it’s here that concrete decay can be already more common as chlorides in the moist, salty air react more aggressively with the reinforcing steel. Concrete decay is an ever-present issue in locations close to the sea and character owners need to be regularly on the lookout for any signs of decline and to ensure that protective measures are maintained.
The same can be said for chlorides associated with swimming-pool chlorine or saltwater pools.
Also, there is often moisture close to the ground surface in beachfront blocks and water can soak up into the structure. Large buildings with basement or underground car parks can experience the same problem with groundwater seepage.
In summary, concrete decay is a shared problem. It can rule to meaningful structural damage which may be difficult and expensive to repair. It is not always easy to detect, it can consequence in serious safety implications and it can be avoided by getting expert advice and using the right materials and appropriate construction guidelines.