T3-7: Investigation and Inspection Flashcards
What is something that accelerates chloride-induced corrosion?
De-icing salts
[NAQ] bulk costs of de-icers commonly used in the UK
The ‘best ones’ are more expensive - likewise with material considerations (e.g. stainless steel more expensive)
Why might a concrete/ reinforcement investigation be needed (x4)?
- Structures not meeting original design life
- Structures required a longer than originally planned service life
- Combining existing structures with new construction
- Change of use (e.g. higher loading)
Describe the primary (stage 1) investigation objectives
- Find out if the structure is worth investigating further (original structural capacity, current/future operating requirements)
- If not (requirements exceed original structural capacity, strengthening not feasible), consider removal and replacement
- If so (original capacity adequate for current and future use, strengthening is feasible) move to investigation stage (stage 2)
Name the three secondary (stage 2) investigation objectives
- Check the current structural capacity in the deteriorated state
- Check the cause of deterioration
- Check the possible repair approach and considerations
What checks (x3) will occur as part of the current structural capacity in the deteriorated state assessment?
- Gross dimensional check
- Specialist dimensional checks (RC); exposing reinforcement (identifying type, diameter, spacing)
- Cracking, spalling and delamination
- Tensile and compressive testing of concrete and steel
What checks (x6) will occur as part of the cause of deterioration assessment?
- Concrete cover surveys
- Chloride and carbonation sampling
- Concrete core samples and petrographic analysis
- Specialist surveys for post-tensioned tendon ducts
- Electrical continuity testing
- Half cell potential surveys
If cathodic protection is considered, what checks (x5) will occur as part of the repair approach and considereations assessment?
- Check on the electrical continuity of existing reinforcement
- Weldability of existing reinforcement (carbon equivalent)
- Impact of increase in dead load - (mesh and overlay)
- Availability of AC power (needed for impressed current CP)
- Access for future monitoring (high risk motorway or military base)
Describe the difference between an inspection and an investigation
Inspections are typically used to monitor an issues (e.g. bridges have principal inspections every five years)
Investigations are used to identify the issue or problem (e.g. problem is due to chloride-induced corrosion)
What are two examples of special inspections, that may be more frequent?
- Post-tensioning
- Half joints
Name three potential issues with inspections and repairs?
- Accessibility can be limited
- For conventional repair options, may need to close the road/…
- Regular patch repairs are impossible and not sustainable
How can deterioration to half-joints and bearing shelves occur?
- Carriageways are contaminated with chloride ions due to de-icing salts
- Chloride laden water leaks through defective joints
How do leaking joints develop?
- The use of chloride based de-icing salts continues
- Joints leak and can be expected to continue to leak
What are the impacts of half-joint deterioration?
- The corrosion products create an internal pressure in the concrete cover
- This leads to cracking, delamination and spalling of the concrete cover
- There is an exponential increase in corrosion and concrete deterioation, due to cracked concrete
What things (x3) can be done to use the most economical resources for construction and maintenance?
- Use mild steel for construction
- Use salt for de-icing
- Use the lowest cover to meet life
What is an example of a component that often fails?
Elastomeric joints - there are inaccessible/hidden steel members in the middle
