Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Useful Fundamentals of Shrinkage and Creep of Concrete
In this contribution selected fundamental properties of concrete are presented and discussed. Basic mechanisms of shrinkage are first described in some detail. With increasing age of concrete different mechanisms of shrinkage become activated. During the first hours after mixing dissolution of cement is the main shrinkage mechanism. Depending on the humidity of the surrounding air capillary pressure in the pore water may cause serious damage in the first hours. After this initial loss of water, the remaining aqueous solution is retreated in the free spaces between fine aggregates and first hydration products. The role of disjoining pressure is pointed out in detail. In this context it becomes clear that the influence of capillary pressure on shrinkage of hardened concrete can be neglected. In equilibrium with RH lower than 50 % the dominating mechanism is the increasing surface energy of the drying gel particles. Shrinkage of high strength concrete has a totally different time evolution as the time-dependent moisture distribution in aging high strength concrete is completely different. If high strength concrete is exposed to an environment with RH higher than 80% there will be no shrinkage at all but swelling. Creep of concrete can be described in a realistic way by means of rate theory. Elements of rate theory are briefly described in the last section. Prediction of creep can be significantly improved if these useful fundamentals are taken into consideration.
Useful Fundamentals of Shrinkage and Creep of Concrete
In this contribution selected fundamental properties of concrete are presented and discussed. Basic mechanisms of shrinkage are first described in some detail. With increasing age of concrete different mechanisms of shrinkage become activated. During the first hours after mixing dissolution of cement is the main shrinkage mechanism. Depending on the humidity of the surrounding air capillary pressure in the pore water may cause serious damage in the first hours. After this initial loss of water, the remaining aqueous solution is retreated in the free spaces between fine aggregates and first hydration products. The role of disjoining pressure is pointed out in detail. In this context it becomes clear that the influence of capillary pressure on shrinkage of hardened concrete can be neglected. In equilibrium with RH lower than 50 % the dominating mechanism is the increasing surface energy of the drying gel particles. Shrinkage of high strength concrete has a totally different time evolution as the time-dependent moisture distribution in aging high strength concrete is completely different. If high strength concrete is exposed to an environment with RH higher than 80% there will be no shrinkage at all but swelling. Creep of concrete can be described in a realistic way by means of rate theory. Elements of rate theory are briefly described in the last section. Prediction of creep can be significantly improved if these useful fundamentals are taken into consideration.
Useful Fundamentals of Shrinkage and Creep of Concrete
Wittmann, Folker H. (Autor:in)
10th International Conference on Mechanics and Physics of Creep, Shrinkage, and Durability of Concrete and Concrete Structures ; 2015 ; Vienna, Austria
CONCREEP 10 ; 84-93
18.09.2015
Aufsatz (Konferenz)
Elektronische Ressource
Englisch
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