Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Cracking tendency of UHSC - influence of fibers and expansive admixtures
Ultra high strength concretes (UHSC) are new materials with high compressive and tensile strength. High performances are obtained by reducing drastically the water to cement ratio, increasing the cement content, increasing the packing density of solid components by using fine additions and high water reducing admixtures. These modifications have two important consequences: reducing the porosity and increasing the chemical shrinkage due to the high quantity of cement used. The autogenous shrinkage, which is a consequence of the paste self-desiccation, i.e. chemical shrinkage and capillary tension due to emptying porosity , begins as soon as cement and water are in contact. After setting, the rigidity of the material increases and autogenous shrinkage is more and more restrained. Tensile stresses are induced and if they are higher than the tensile strength, cracks occur. ln order to decrease the cracking tendency of UHSC, different solutions are said efficient: use of organic or metallic fibers, use of expansive admixtures. In order to assess the effectiveness of these solutions, the stress induced by autogenous shrinkage in restrained condition has been measured since the end of mixing. The modification on the compressive and flexural strength has been also assessed. The results show that the effectiveness of each investigated solution is quiet different and the more appropriate solution depends on the use aimed for the UHSC.
Cracking tendency of UHSC - influence of fibers and expansive admixtures
Ultra high strength concretes (UHSC) are new materials with high compressive and tensile strength. High performances are obtained by reducing drastically the water to cement ratio, increasing the cement content, increasing the packing density of solid components by using fine additions and high water reducing admixtures. These modifications have two important consequences: reducing the porosity and increasing the chemical shrinkage due to the high quantity of cement used. The autogenous shrinkage, which is a consequence of the paste self-desiccation, i.e. chemical shrinkage and capillary tension due to emptying porosity , begins as soon as cement and water are in contact. After setting, the rigidity of the material increases and autogenous shrinkage is more and more restrained. Tensile stresses are induced and if they are higher than the tensile strength, cracks occur. ln order to decrease the cracking tendency of UHSC, different solutions are said efficient: use of organic or metallic fibers, use of expansive admixtures. In order to assess the effectiveness of these solutions, the stress induced by autogenous shrinkage in restrained condition has been measured since the end of mixing. The modification on the compressive and flexural strength has been also assessed. The results show that the effectiveness of each investigated solution is quiet different and the more appropriate solution depends on the use aimed for the UHSC.
Cracking tendency of UHSC - influence of fibers and expansive admixtures
Rißbildungstendenz bei ultrahochfestem Beton - der Einfluß von Fasern und Expansivbeimischungen
Schwartzentruber, A. (Autor:in) / Philippe, M. (Autor:in) / Marchese, G. (Autor:in) / Laurence (Autor:in)
2002
15 Seiten, 10 Bilder, 6 Tabellen, 4 Quellen
Aufsatz (Konferenz)
Englisch
Cracking Tendency of UHSC - Influence of Fibers and Expansive Admixtures
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Influence of Mineral Admixtures on Expansive Cement Mortars
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