POMPAGE DES BETONS

Abstract : With recent progresses in concrete mix-design, a number of problems have been encountered in the area of pumping. In this context, the aims of this thesis were the following: - to analyse physical phenomena underlying the occurrence of blockages in pumping networks; - to develop a practical methodology, based on simple tests, leading to an evaluation of the pumpability of a given concrete in a given pumping system; - to develop an instrument capable of characterising the steel-concrete interface and to develop models for the calculation of the flow rate/pressure relationship; - to validate the proposed models with tests carried out at the industrial scale. For our tests we used a variety of sixty-eight different concrete mixtures. We developed two new instruments : the modified air-meter (to assess the bleeding rate of fresh concrete); the coaxial cylinder tribometer, a large-gap coaxial viscometer devoted to the test of steeVconcrete interface. Thanks to the analysis of test results, it was possible to understand that pumpability (as related to blockages) is not an intrinsic characteristics of the concrete mix alone, but is rather governed by severa! parameters among which the concrete mixture, the pumping system and the process are found. We established a classification of the blockages and we proposed models to exp lain their formation. The result was to reach a set of practical recommendations to !essen the risks ofblockages. The tests demonstrated the importance of the steel-concrete interface, where a slipping layer takes place. We proposed a predictive model for the pumping of concrete, based upon measurements of the interface and rheological parameters, measured with the new tribometer and the BTRHEOM rheometer, respectively. Finally, we have succeeded in characterising a concrete in the laboratory to predict the pumping parameters. This can reduce problems arising at the work site with new types of mixtures as high-performance or self-compacting concrete. Keywords : bleeding, blockage, concrete pumps, fresh
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Denis Kaplan. POMPAGE DES BETONS. Chemo-informatique. Ecole Nationale des Ponts et Chaussées, 1999. Français. ⟨NNT : 1999ENPC9928⟩. ⟨tel-01310219⟩

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