PSI - Issue 64

Laurena De Brabandere et al. / Procedia Structural Integrity 64 (2024) 97–104 Laurena De Brabandere et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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4.4. Torrent permeability

Fig. 6 shows the Torrent gas permeability coefficient k T for concrete with CEM I, CEM II and CEM III and w/c 0.4 and 0.7. With this method, the same trend in performance for both 0.4 and 0.7 was noticed. CEM III has an inferior performance in comparison to CEM I and CEM II. For concrete with w/c 0.4, CEM II performed slightly better in comparison to CEM I, while for a w/c of 0.7, CEM I had the lowest Torrent gas permeability coefficient and thus the best performance.

Fig. 6. Torrent gas permeability coefficient k T for concrete with a w/c of 0.4 and 0.7 and CEM I, CEM II and CEM III as a binder. Error bars represent the standard error.

4.5. General assessment

Overall, the 4 different test methods gave similar results for the concrete with a w/c of 0.4. However, for the 0.7 mix, the measured performance depends on the used test method. For both capillary imbibition and water vapour diffusion, CEM III had the best performance, while for the gas permeability (CEMBUREAU method) and Torrent permeability, CEM III had the worst performance. This could be explained by the fact that during the first two tests water is available for further hydration and therefore densification of the pore structure. For the gas permeability, the specimens were dried after 28 days of curing, resulting in less to no water available for further hydration of the cement. Furthermore, during the gas permeability tests, the gas is forced through the concrete by applying an external pressure, which was not the case for the capillary imbibition and water vapour diffusion. Future research will involve the measurement of the pore size distribution of the 6 different mix design to determine which pore size range is affected by each performed test. Furthermore, it will be checked whether a correlation can be found between the results of the different test methods. 5. Conclusions In this research, concrete with three different binders (CEM I 52.5 N, CEM II/A-LL 42.5 R and CEM III/A 42.5 R) and two different water-to-cement ratios (0.4 and 0.7) were tested. Their performance was investigated via 2 unsaturated flow methods (imbibition and diffusion) and 2 gas permeability tests (CEMBUREAU and Torrent method). It was found that for a concrete with a w/c of 0.4, CEM III had the worst performance in all tests. However, for the concrete with a w/c of 0.7, there was no overall trend for the 4 tests. According to the capillary imbibition and water vapour diffusion test, CEM III had a superior performance in comparison to CEM I and CEM II, while according to the gas permeability tests, CEM III performed the worst. The performance of the different binder types is thus dependent on the w/c of the concrete and the used test method. The difference in performance between the unsaturated flow methods and the gas permeability tests can possibly be explained by the fact that in the first two test, water or moisture was available to continue the hydration reaction which can lead to pore refinement.