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  <doc>
    <id>4429</id>
    <completedYear/>
    <publishedYear>2014</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst>217</pageFirst>
    <pageLast>221</pageLast>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>conferenceobject</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation>Fédération International du Béton (fib)</creatingCorporation>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Accelerated carbonation: changes in water transport, porosity and phases of mortar due to different CO 2 pressures</title>
    <abstract language="eng">Currently, the carbonation resistance of concrete is assessed on the basis of accelerated tests performed with high (unrealistic) CO2 concentrations. It remains unclear whether these high concentrations reflect the processes occurring under natural conditions and enable the accurate prediction of field behaviour. To develop future test procedures with higher reliability, it is necessary to deepen the knowledge on the mechanisms of carbonation. Thin slices of mortar were stored in a gaseous mixture of 2 % CO2 and 98 % N2 at atmospheric pressure or 5 bar. IH-NMR equipment was used to detennine moisture profiles with aresolution of 0.2 mm. At 5 bar a drying front at the near-surface region of the mortar discs severely inhibited the progression of the carbonation reactions. This effect was prevented by exposure to altemating cycles of pressure and storage at atmospheric pressure (65%RH) which significantly increased the rate of carbonation, but was too severe to resolve the effect of cement type on carbonation resistance. Furthermore , the evolution of water beyond the carbonation front of mortar sampies under accelerated concentration and at atmospheric pressure was clearly visible. This may lead to an overestimation of carbonation resistance of sampies tested under accelerated conditions at the optimal relative humidity for natural carbonation (50-70% RH).</abstract>
    <parentTitle language="eng">Proceedings of the 10th fib International PhD Symposium in Civil Engineering, July 21 to 23, 2014, Québec, Canada</parentTitle>
    <identifier type="url">https://mediatum.ub.tum.de/doc/1230854/1230854.pdf</identifier>
    <enrichment key="opus.import.date">2022-06-18T22:00:09+00:00</enrichment>
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    <licence>Keine Lizenz - Es gilt das deutsche Urheberrecht: § 53 UrhG</licence>
    <author>Charlotte Thiel</author>
    <author>Robin E. Beddoe</author>
    <author>Dirk Lowke</author>
    <author>Christoph Gehlen</author>
    <collection role="institutes" number="FakBau">Fakultät Bauingenieurwesen</collection>
    <collection role="othpublikationsherkunft" number="">Externe Publikationen</collection>
    <collection role="othforschungsschwerpunkt" number="16313">Gebäude und Infrastruktur</collection>
    <collection role="institutes" number="">Labor für Baustoffe</collection>
  </doc>
  <doc>
    <id>4427</id>
    <completedYear/>
    <publishedYear>2016</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst>261</pageFirst>
    <pageLast>268</pageLast>
    <pageNumber/>
    <edition/>
    <issue/>
    <volume/>
    <type>conferenceobject</type>
    <publisherName>RILEM Publications S.A.R.L.</publisherName>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Investigating the role of moisture on concrete carbonation using single-sided H-NMR</title>
    <abstract language="eng">Accelerated test methods are commonly used in order to predict concrete carbonation in natural concentrations. Here, specimens are carbonated at high CO 2 concentrations at a specified temperature and relative humidity. However, the transfer of laboratory results to field behaviour remains difficult because CO 2 transport is affected by the original moisture content of the specimens and additional moisture formed by the carbonation reaction. Therefore knowledge on moisture transport and content during carbonation is required. Specimens made with Ordinary Portland cement and a water/cement ratio 0.50 were exposed to 0.05, 2 and 10 vol.% CO 2 for 28 days. Single-sided NMR moisture profiles were determined before, during and after carbonation. It is shown that moisture content increases due to carbonation at high CO 2 10 %) in the beginning of the exposure. An increase in capillary pore water in front and behind the carbonation front could be observed even after 28d. During natural carbonation moisture changes are mainly due to the change in porosity produced by the carbonation reactions. It is shown that changes in phase composition and thus porosity dominate the carbonation process in cement-based materials. Therefore, the suitability of high CO 2 concentrations is limited for an accelerated test that reflects field condition. Single-sided 1 H NMR proved to be a valuable tool to investigate moisture transport in concrete non-destructively.</abstract>
    <parentTitle language="eng">International RILEM Conference on Materials, Systems and Structures in Civil Engineering 2016 - Conference segment on Moisture in Materials and Structures, 22-24 August 2016, Lyngby, Denmark</parentTitle>
    <identifier type="isbn">978-2-35158-171-1</identifier>
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    <licence>Keine Lizenz - Es gilt das deutsche Urheberrecht: § 53 UrhG</licence>
    <author>Charlotte Thiel</author>
    <author>Robin E. Beddoe</author>
    <collection role="institutes" number="FakBau">Fakultät Bauingenieurwesen</collection>
    <collection role="othpublikationsherkunft" number="">Externe Publikationen</collection>
    <collection role="othforschungsschwerpunkt" number="16313">Gebäude und Infrastruktur</collection>
    <collection role="institutes" number="">Labor für Baustoffe</collection>
  </doc>
</export-example>
