How & Why Concrete Structures Deteriorate

Concrete is a relatively durable and robust building material but it can be severely weakened by poor manufacture or a very aggresive environment. Concrete degredation can be a cause for concern on its own, or in reinforced concrete structures it may lead to decreased protection to the steel. This in turn encourages corrosion of the steel, often followed by cracking and spalling of the concrete which can lead to structural damage.

 

Deterioration of concrete is due to:

  • Chemical degredation
  • Corrosion of the reinforcement steel
  • Mechanical attack
  • Physical damage

 

Underylying contributors to deterioration:

  • Poor construction
  • Lack of maintenance
  • Design faults

Repair & Protection Methods

The successful repair and protection of concrete structures which have been damaged or which have deteriorated requires professional assessment, then design, supervision and execution of technically correct principles – in accordance with the Principles and Methods defined in the European Standard EN 1504.

 

The 11 best practice principles and methods of repair and protection in accordance with EN 1504 are:

  1. Protection against ingress
  2. Moisture control
  3. Concrete restoration
  4. Structural strengthening
  5. Physical resistance
  6. Resistance to chemicals
  7. Preserving or restoring passivity
  8. Increasing resistivity
  9. Cathodic control
  10. Cathodic protection
  11. Control of anodic areas

 

Sika has been associated with concrete refurbishment since the company was founded over 100 years ago. We have developed fundamental procedures and pioneering products for the permanent repair and protection of decaying and damaged concrete. To assist owners, engineers and contractors with the correct selection of repair products, Sika has developed a schematic system of approach designed to meet the individual requirements of a structure, its exposure and use.

 

Sika‘s concrete repair and protection solutions are designed to rehabilitate and restore concrete surfaces back to their original quality and include the following:

  • Concrete repair mortars
  • Anti-corrosion coatings
  • Corrosion inhibitors
  • Reinforcement corrosion protectors
  • Embedded galvanic anodes

Diagnosis Methodology

The key stages in the repair and protection process

Assessment of the Structure from the Condition Survey

The assessment of a damaged or deteriorated reinforced concrete structure from the condition survey should only be made by qualified and experienced people. This process of assessment must always include the following aspects:

 

  • The condition of the structure including visible, non-visible and potential defects
  • Review of the past, current and future exposure

 

Identification and Diagnosis of the Root Causes of Deterioration

Following review of the original design, construction methods and programme, and the assessment from the condition survey, it is possible to identify the “root
causes”of each different type and area of damage:

 

  • Identify defects and mechanical, chemical or physical damage to the concrete
  • Identify concrete damage due to reinforcement corrosion

 

Determine the Repair and Protection Options and Objectives

With most damaged or deteriorated structures, the owner has a number of options which will effectively decide the appropriate repair and protection strategy to meet the future requirements of the structure.

 

These options include:

  • Do nothing
  • Downgrade the structure or its capacity
  • Prevent or reduce further damage with no or minimal repair
  • Improve, refurbish or strengthen all or part of the structure
  • Demolition

 

Selection of the Appropriate Repair Principles and Methods

To meet the owner’s future requirements, the appropriate Repair and Protection Principles must be selected, and then the best method of achieving each principle must be decided.