Une meilleure compréhension du gel des matériaux cimentaires en présence de sel pour un béton durable

Ce texte présente les méthodes d'essais de caractérisation de résistance au gel actuellement applicables en France. Ces essais en place depuis 10 à 20 ans ont largement contribué à l'amélioration de la prescription et de la durabilité des bétons face à la résistance au gel en présence de sels. Dans une deuxième partie, la distribution et la répétabilité ainsi que la méthode d'analyse du résultat de l'essai d'écaillage XP P18-420 sont évalués au travers d'un nombre significatif d'essais sur des bétons composés d'un ciment de Portland avec un agent entraîneur d'air

MARKET EXPECTATIONS AND THE VALUATION EFFECTS OF EQUITY ISSUANCE

We examine how the wealth effects of equity offers are influenced by investors' expectation of the equity type (public or private) to be issued. Firms deviating to the public market may be issuing when information asymmetry or agency costs are high, and their wealth effects are more negative than for firms that are anticipated to issue equity publicly. Firms deviating to the private market, however, may signal firm undervaluation or monitoring benefits and experience more positive wealth effects than firms that are expected to issue equity privately. For the private issues, public market accessibility appears to influence the wealth effects. 2006 The Southern Finance Association and the Southwestern Finance Association.

Penetration of chlorides in hardened concrete during frost salt scaling cycles

Sixty samples from three concrete mixes (same components) were prepared and subjected to frost salt scaling cycles. A set of 20 samples from the same mix was tested according to the French standard XP P18-420. Another set was exposed to different chloride concentrations. Different numbers of freeze/thaw cycles were applied to the last set. The mass of scaled-off particles follows a lognormal distribution. Despite high standard deviation, this scaling test enables to separate high resistant from very low resistant concrete. A combined analysis reveals that the scaling and the chloride penetration front are independent from a phenomenological point of view and that the chloride concentration on the exposed surface directly influences the amount of scaled mass according to the typical pessimum effect. These results raise two main questions: is the amount of chloride on the surface solution a direct or indirect parameter and what happens to this pessimum effect if we take into account the scaling test dispersion

Les calcaires de Lorraine dans l’architecture et la sculpture gothiques de la région mosane. Origine, utilisation et diffusion d’un matériau au Moyen Âge

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