Introduction to Concrete Repair & Protection
Billions are wasted every year demolishing and re-building structures that deteriorate or are deemed no longer fit for purpose. The energy and resources that are spent in waste management and re-construction has an immense impact on our planet.
Concrete should be built to last and that the application of high-quality protective systems and repair materials can prolong the life of a structure well beyond its original design life.
Protective systems can dramatically inhibit the impact of aggressive elements on the concrete. Repair systems can make damaged concrete as good as new. Not only does this have a positive environmental impact, but structure owners see the benefits of improved management costs over the life of the structure. Every dollar spent on improved concrete quality, protection and enhancement pays off in long term durability.
Root Causes of Concrete Damage and Deterioration
For many years, the different types of damage and the root causes of concrete damage have been well known and equally the correct repair and protection methods have also been established. All of this knowledge and expertise is now summarised and clearly set out within the European Standards EN 1504. This consists of 10 parts and provides a systematic approach to rehabilitating concrete.
Part 9 of EN 1504 outlines 11 principles that defines the general use of products and systems, for the repair and protection of concrete. These allow engineers to correctly repair and protect all of the potential damage that can occur in reinforced concrete structures. Principles 1 to 6 relate to defects in the concrete itself, Principles 7 to 11 relate to damage due to reinforcement corrosion.
1. Concrete Defects & Damage
- Mechanical Attack - from impact, overloading, movement, vibration & explosion.
- Chemical Attack - from AAR alkali aggregate reactions, aggressive chemical exposure, bacterial or biological action, efflorescence and leaching
- Physical Attack - from freeze-thaw action, thermal movement, salt crystal expansion, shrinkage, erosion, abrasion & wear
2. Concrete Damage Due to Steel Reinforcement Corrosion
- Chemical Attack - Carbon dioxide (CO2) in the atmosphere reacting with calcium hydroxide in the concrete pore liquid.
- Corrosive Contaminants - Chlorides accelerate the corrosion process and can also cause dangerous “pitting” corrosion. At above 0.2 – 0.4% concentration in the concrete chlorides can break down the passive oxide protective layer on the steel surface. Chlorides are typically from marine/ salt water exposure and/or the use of de-icing salts.
- Stray Electrical Current - Metals of different electro-potential are connected to each other in the concrete and corrosion occurs. Corrosion can also be due to stray electrical currents from power supply and transmission networks.
The European Union fully introduced all of the European Standards 1504 in January 2009. These Standards define the assessment and diagnostic work required, the necessary products and systems including their performance, the alternative procedures and application methods, together with the quality control of the materials and the works on site.