The concrete lining of traffic tunnels is normally exposed to combined carbon dioxide (C02) and chloride environments. The ingress of CO2 and chloride ions into concrete in these environments could be different from that in I their independent effects, but relatively little is known about this, particularly for high performange concretes (HPCs) that are commonly used in tunnel linings. In this project, changes to hydrated cement pastes and concretes containing pulverised fuel ash (PF A) and microsilica (MS) during both independent and combined exposures to CO2 and chlorides were studied. Effects of these test regimes on the rate of carbonation and chloride ingress were quantified by analysing profiles of the consumed hydroxyl ions and chloride ions. The suitability of using Autoclam Permeability System, Permit Ion Migration Test and Covercrete electrode array for assessing the extent of carbonation and chloride ingress in normal and high performance concretes in the above exposure environments was explored. The results indicated that exposure to chlorides before subjecting to carbonation significantly slows down the progress of carbonation in concretes. However, the influence of carbonation on chloride ion ingress depends on concrete type and carbonation degree. It was found that this combination could severely compromise the tunnel lining durability, particularly for concretes containing PF A, due to the formation of microcracks in carbonated concretes. Autoclam and Permit enabled an assessment of the variations in permeation properties due to the test regimes, and the Covercrete electrode array could identify the carbonation depth and the extent of chloride ingress.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:677849 |
| Date | January 2014 |
| Creators | Wang, Y. |
| Publisher | Queen's University Belfast |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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