The key to success to any new-build or renovation project is preparation, as according to the well-worn saying, ‘fail to prepare; prepare to fail’. It’s a motto that is particularly pertinent to concrete refurbishment – good quality surface preparation goes hand-in-hand with safe, effective and long-term repair.

Making a start

By getting the basics right, the first step to successful concrete repair has been taken. Before any work is carried out, it’s essential to check the right tools and products are available to do the job. This means ensuring said tools are in excellent condition – clean and well-maintained. In terms of concrete removal, only defective areas highlighted by a supervising officer or qualified engineer should be removed, and as with any repair project, only use clean, potable water when required.

It’s essential to avoid contaminating mixture with other chemicals or mixing powders from different products. It’s also not advisable to add  more water than recommended. In addition, mixing and applying product in direct sunlight should be avoided.   

Clean break

For the all-important substrate preparation, defective concrete should be marked and removed accordingly. For small patch repairs, a hammer and chisel will likely suffice. A hammer drill should be used on larger areas, whilst even larger sites might best be treated with a high-pressure water jetting.  

Concrete should be removed to a minimum of 15mm behind the reinforcing bars. Cut the sides to a minimum of 90° to avoid undercutting and maximum of 135° to reduce de-bonding around edges. The substrate should be sound and devoid of loose material before repairs continue. If the substrate appears cracked, immediately inform a supervisor.

Reinforcement Preparation

For the reinforcement preparation, remove all tie wires, mortar/concrete, rust/scale and any other loose material using one of the following techniques:

  • Steel wire brush or hand/power tools – this technique is applicable only in carbonated concrete and under environmental constraints where techniques 2 and 3 cannot be used.  
  • Abrasive blast cleaning – if chlorides are present reinforcement should be cleaned with water afterwards
  • High pressure water jetting – 1,100 bar minimum

Good preparation in lieu of installation of Sika’s proven, high-performance total control management system is vital for the restoration of concrete structures of all types – bridges, car parks, tunnels, quaysides, etc; infrastructure that must be relied upon to remain strong and stable for the long-term benefit of the built environment and those living within it.