Materials and Structures

, Volume 40, Issue 8, pp 813–825 | Cite as

Drying induced moisture losses from mortar to the environment. Part II: numerical implementation

Original Article

Abstract

This paper presents a novel methodology to appropriately account for boundary conditions in numerical analyses of moisture fields in cementitious materials. The proposed methodology consists of using experimentally obtained moisture emissivity coefficients together with the vapour pressure difference between the environment and the exposed surface (based on the average surface humidity content). The performance of such methodology (implemented on DuCOM, a computational code suitable for calculation of moisture/temperature fields in cementitious materials) is evaluated by comparing the numerical predictions with the experimental results presented in the Part I companion paper. Influences of the many environmental conditions reported in Part I are investigated for validation of the proposed numerical methodology: temperature, relative humidity, wind speed and age of exposure of specimens. Furthermore, an additional numerical formulation for inclusion of the effect of evaporative cooling, based on the computation of additional heat fluxes induced by evaporative moisture losses, is presented, together with a validation example. Finally, two numerical sensitivity analyses are put forward for clarification of the relative importance of the parameters involved in moisture loss from cementitious materials, as well as the relevance of the evaporative cooling.

Keywords

Cement Moisture Evaporation Evaporative cooling Numerical simulation Boundary conditions 

Résumé

Cet article présente une nouvelle méthodologie afin de mieux tenir compte des conditions limites lors d’analyses numériques des champs d’humidité dans les matériaux cimentaires. La méthodologie proposée consiste à utiliser des coefficients d’émissivité d’humidité obtenus expérimentalement associés avec la différence de pression de vapeur entre l’environnement extérieur et la surface exposée du béton (basée sur le contenu moyen de l’humidité à la surface). La validité de cette méthodologie (intégrée dans un logiciel de calcul des champs d’humidité et de température des matériaux cimentaires—appelé DuCOM) est évaluée en comparant les prédictions aux résultats expérimentaux rapportés dans l’article précédant (partie 1). Les influences des nombreuses conditions environnementales rapportées dans la partie 1 y sont vérifiées et validées, notamment: la température, l’humidité relative, la vitesse du vent et la durée d’exposition des spécimens. En outre, une formulation numérique additionnelle pour inclure l’effet du refroidissement par évaporation (basée sur le calcul des flux de chaleur additionnels induits par évaporation) est présentée et validée avec un exemple. En conclusion, deux analyses de sensibilité sont présentées pour clarifier l’importance relative des paramètres impliqués dans la perte d’humidité des matériaux cimentaires et pour démontrer la pertinence de l’influence du refroidissement par évaporation.

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Copyright information

© RILEM has copyright 2007

Authors and Affiliations

  1. 1.Faculty of EngineeringUniversity of PortoPortoPortugal
  2. 2.School of EngineeringUniversity of TokyoTokyoJapan
  3. 3.Civil Engineering DepartmentFaculty of Engineering of the University of PortoPortoPortugal

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