The past and present in concrete repair Members response: Consultant s perspective

Transcription

1 The past and present in concrete repair Members response: Consultant s perspective Geir Horrigmoe Norut Technology, Norway geir@tek.norut.no CONREPNET Members Workshop, Prague, 22 June 2005

2 Performances of concrete repairs The performance of repairs is disappointing but not surprising. Similar results were found in a study of repairs of reinforced concrete highway bridges in Norway.

3 What is concrete repair? What is the objective or the expected future performance of a specific action? Suggested classification system: Protection Repair Strengthening Will facilitate performance evaluation, which otherwise may be confusing.

4 Protection of concrete structures Protection methods seek to limit the intrusion of moisture, chlorides, carbon dioxide, etc. by either surface treatments or through use of electrochemical principles. Sealers, membranes, overlays Inhibitors Cathodic protection systems

5 Repair of concrete structures The objective of repair methods is to restore the reinforced concrete structure to its initial design conditions and to reduce or remove the actual cause of deterioration. Removal of contaminated concrete, followed by sandblasting of corroded steel bars and application of a (cement-based) repair material, often referred to as patch repair. Electrochemical treatments (chloride extraction, realkalization).

6 Strengthening of concrete structures The objective of strengthening procedures is to improve the structural performance by increasing stiffness and strength. Increased concrete and steel bar section External post tensioning FRP composites externally bonded to the concrete surface

7 Performance of current methods for concrete repair Current methods of concrete repair are unsatisfactory: - They are often inefficient in preventing further deterioration - The restoration of structural stiffness and strength is not easily achieved The relatively high costs of repair often cause delayed or inadequate actions and thus permitting deterioration to continue.

8 Concrete repairs Simple and straightforward? Repair and rehabilitation of concrete structures have evolved into a complex, inter-disciplinary science where it is necessary to master and combine knowledge from a number of different fields such as concrete material technology, environmental loadings, transport mechanisms, electrochemistry, structural mechanics, and composite materials.

9 The way forward There exists a gap between research and current industry practice. In many cases, inadequate methods with unsatisfactory performance are selected, despite available documentation. There is a need for improvements and innovations in concrete repair to meet future requirements regarding performance and costs.

10 Challenges in the 21 st century The major challenge for the concrete industry in the 21st century is to combine the increasing need for repair and renewal of infrastructure with shrinking public budgets. We must develop technology which provides cheaper and more efficient concrete repairs. ( We must do more and better for less ). Management of infrastructure should meet the requirements of sustainable development.