Concrete Repairs

Concrete repair

Concrete is widely used in modern construction and it’s not hard to understand why. It is easy to make from low-cost and readily available ingredients.

What is concrete made from?

  • Coarse and fine aggregates such as sand, gravel, stones, larger bits of crushed rock (60–75%)
  • Cement (10-15%)
  • Water (15-20%)

Mixed together these ingredients form a composite material that is hard, durable and extremely strong in compression, making it highly suitable for use as columns. Concrete’s one big drawback is that it is about 10 times weaker in tension than in compression. That means it easily cracks if it is subjected to bending or tension loads, making it less suitable for use as beams or lintels. This weakness is easily resolved by casting the concrete around a cage made of steel reinforcing bars. Steel-reinforced concrete provides improved flexural and tensile strength.

Why does concrete degrade?

Degradation and cracking of concrete can be caused by a number of factors including:

  • Moisture ingress
  • Overloading or movement
  • Chemical changes (carbonation, loss of alkalinity, corrosion of reinforcement)

Modern concrete most often fails through three interrelated problems that cause a cycle of degeneration:

  1. Alkalis from the cement react with silica in the aggregates, making the concrete crack from the inside or to spall away from the surface
  2. Cracked concrete allows ingress of CO2 and moisture, which causes steel reinforcing bars to corrode. The build-up or iron oxide layers causes the rebar to expand and further crack the concrete
  3. Water that has seeped inside porous or cracked concrete and go through freeze and thaw cycles, causing ever widening cracks

Repairing Concrete Structures

The Association has manufacturing members and contractor members who are expert in modern concrete repair materials and technologies. Their expertise covers an array of repair solutions that range from simple concrete patching and coating systems to strengthening cracked concrete and cathodic protection of reinforcing steels. Find a contractor who specialises in concrete repair.