Materials and Structures

, Volume 31, Issue 10, pp 651–661 | Cite as

On strength of porous material: Simple systems and densified systems

  • Lauge Fuglsang Nielsen
Scientific Reports

Abstract

The question of non-destructive testing of porous materials has always been of interest for the engineering profession. A number of empirically based relations between stiffness (modulus of elasticity) and strength (modulus of rupture) of materials have been established in order to control quality without damaging or destroying the material or the building component considered. The efficiency of modulus of elasticity-modulus of rupture relations for this purpose depends very much on the homogeneity of the porous material considered. For building materials like wood and concrete of normal or lower quality with a number of irregularities, only scattered modulus of elasticity-modulus of rupture relations (clouds) can be established, from which no really reliable results can be read.

For homogeneously produced porous materials, however, like modern ceramics and high performance concretes, modulus of elasticity-modulus of rupture relations can be presented which are reliable. The present paper contributes to the theoretical research on nondestructive testing of such materials relating strength to stiffness and pore geometry.

It is demonstrated that solutions for stiffness, tensile strength, and pore strength (damaging pore pressure, frost, fire) for some ideal porous materials can be determined theoretically only from knowing about pore geometry, solid phase stiffness, and zero-porosity strength. Pore geometry is the very important common denominator which controls both stiffness and strength.

The accurate results obtained are finally used to suggest generalizations with respect to strength in general (tensile, compression, flexural), pore strength, and stiffness versus more realistic pore systems. The expressions suggested are positively evaluated against a number of experimental data reproduced from the literature.

Résumé

La question des essais non destructifs des matériaux poreux a toujours été d'un intérêt pour les ingénieurs. Un certain nombre de relations empiriquement basées sur la relation entre la rigidité (module d'élasticité) et la résistance (module de rupture) des matériaux ont été établies afin de contrôler la qualité sans endommager ou détruire le matériau ou le composant de la structure étudiée. L'efficacité de ces relations à cet égard dépend énormément de l'homogénéité du matŕiau poreux considéré. Pour des matériaux de construction comme le bois et le béton d'une qualité moyenne ou inférieure présentant un certain nombre d'irrégularités, seules des relations module d'élasticité-module de rupture dispersées (nuages) peuvent être établies à partir desquelles aucun résultat fiable ne peut réellement être observé.

Cependant, pour les matériaux poreux produits d'une manière homogène, tels que des céramiques contemporaines ou des bétons à haute performance, les relations module d'élasticité-module de rupture fiables peuvent être présentées. Cet article contribue à la recherche théorique sur les essais non destructifs de tels matériaux associat la résistance, la rigidité et la géométrie des pores.

On démontre que des solutions pour la rigidité, la résistance à la traction et la résistance des pores (pression des pores, gel, feu) pour quelques matériaux poreux idéaux peuvent être déterminées thóriquement en ne connaissant que la rigidité de la face solide et la résistance pour une porosité nulle, la géométrie des pores est le dénominateur commun très important qui contrôle la rigidité et la résistance.

Les résultats précis obtenus sont finalement utilisés afin de suggérer des généralisations vis-à-vis de la résistance (de traction, de compression, de flexion), la résistance des pores et la rigidité contre des systèmes plus réalistes des pores. Les expressions générées sont alors mesurées en comparaison avec un nombre de données expérimentales trouvées dans la littérature.

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Copyright information

© RILEM 1998

Authors and Affiliations

  • Lauge Fuglsang Nielsen
    • 1
  1. 1.Department of Structural Engineering and MaterialsTechnical University of DenmarkDenmark

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