What is concrete? It is a mix of cement, sand, water and small stones. In coastal cities such as Sydney it used to include seashells, but 100 years on, we know better than to use anything dredged from the sea as it's likely to retain a salty, alkaline component.
Concrete deteriorates as it ages, and if the cement mix is too alkaline, star-like cracks form that allow water to penetrate. This is 'concrete cancer' or spalling. And if left unchecked, it can jeopardise a building’s structure.
This was the frightening case at 1 Beach Rd overlooking Bondi Beach. As it was one of the first ever Sydney buildings to use concrete reinforcement there were mistakes made in the technique. When we began to break out the original 1920s concrete we uncovered large seashell particles. The aggregate was too large for getting a tight fit around reinforcement. MAX Build also observed an unevenness in the material that would have benefited from more mixing and a stir once poured into the formwork.
Signs of spalling include crumbling concrete and rust stains. Once the steel reinforcement bar is visible, this exposure to air speeds the deterioration.
Concrete spalling must be removed and any exposed steel replaced or treated. The area is then repaired to the original concrete profile using cement mortar, epoxy mortar or concrete. Or for minor cracks, MAX Build uses a suitable epoxy resin, special mortars and filler injection techniques.
To ensure transparency we photographically document all work performed.
MAX Build services include:
- Concrete spalling to slab edges, overhead balcony soffits or large structural beams
- Form and pour new or add-on structures
- Installation of sacrificial anodes
- Welding or splicing reinforcement