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Influence of pre-cracking over water desorption in cement pastes and mortars

type de publication      communication internationale avec actes publiés
date de publication 2009
auteur(s) Rougelot Thomas; Burlion Nicolas; Skoczylas Frédéric
  
conférence NUCPERF 2009
     dates de 30-03-2009 à 02-04-2009
     lieu Cadarche, France
     nom des actes NUCPERF 2009 - Long Term Performance of Cementitious Barriers and Reinforced Concrete in Nuclear Power Plants and Waste Management
  
pages 125 – 133
ISBN / ISSN 978-2-35158-072-1
résumé Concrete structures are generally submitted to stresses and strains that can lead to cracks and durability issues. The aim of this paper is to propose an experimental set-up to determine to what extent the kind of pre-cracking influences the water desorption of cement pastes and mortars. Two methods to generate cracks are used. The first one consists in damaging prismatic specimens by three-point bending. This leads to a so called localized macrocrack, whose average opening varies between 10 and 80 micrometers. Four states of damage are studied: sound, 1, 3 and 7 macrocracks. The second method generates a more diffuse microcracking by submitting samples to a quick thermal shock.
The obtained results tend to show that localized macrocracking is not sufficient to influence neither the water desorption isotherm, nor drying kinetics. On the contrary, the microcracking has two main effects: an increase in desorption kinetics for high relative humidity, and a slight change in the water desorption isotherms. These observations are attributed to a more connected porous network thanks to these microcracks, which accelerate the drying process and allow to remove water from masked pores (due to ink-bottle -pores with narrow neck- configuration) by increasing paths where water can migrate from the pore to the exterior of the specimen.
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