Flashcards
Durability
Flashcards do conjunto (7)
- 1What are the 3 requirements of ASR? - TestMAS
-Sufficient moisture
-Sufficient alkaline
- Reactive silica - 2What are the issues/events that occur while concrete is in a fresh state? - Test- Bleeding or settlement - causes voids and channels
- Poor compaction - causes excessive voids
- Poor placing and handling - causes segregation - 3List 4 tests that could be performed as part of a condition assessment/investigation techniques ?1- Delamination Survey
2 - Cover Survey
3 - Rebar Potential
4 - Corrosion Rates - 4Explain - Delamination Survey- Delaminations are internal cracks or voids that run parallel to concrete surface - hard to detect
- Detected via chain drag, hammer or other acoustic method
- Causes of delaminations are bleed water rising, closely spaced reinforcing - chloride and ASR - 5Explain - Cover Survey- A cover meter sends an electromagnetic pulse to identify location of rebar and hence the cover concrete depth
- cover depth most important factor for durability
- usually reliable to within 5mm but should be calibrated regularly
- reliability decreased by closely spaced bars and reo at large depths - 6Explain - Rebar Potentials- Uses a CCS half cell connected to a voltmeter which is then connected to rebar (drill hole)
- measures thermodynamic risk of corrosion - quanitifies risk
-largely used for chloride induced issues
- can do potential mapping using empirical relationship between half cell and corrosion current
- limitations: plots take exp, delaminations may disrupt potential field and doesn't measure actual corrosion rate - 7Explain - Corrosion Rates- only reliable method of measuring corrosion rate in concrete
- Coulosatic or Galvanostatic LPR sends a pulse into steel and response is measured for 20-60 seconds
- determines corrosion rate from pulse response
- generally used once locations of corrosion activity identified already