Experimental Study on a Mortar. Temperature Effects on Porosity and Permeability. Residual Properties or Direct Measurements Under Temperature

Civil engineers sometimes submit materials, including cement-based materials, to high temperature levels, and it is thus of interest to evaluate the changes in permeability and diffusivity properties of such heated materials. The primary objective of the present experimental study was to evaluate the effect of high-level temperatures on the gas permeability of a mortar. The first part of this article presents results of experiments conducted on mortars that have been heated up to either 150 or 250 degrees centigrade. The second part examines the permeability measurements that were done on mortars that were continuously heated along with gas injection. Initial gas permeability and porosity values of the used material, a normalized mortar with a water-cement ratio of 0.5, clearly showed the material homogeneity after a drying phase at 60 degrees centigrade. The initial permeability was shown to be insensitive to confining pressure variation, evidencing the absence of significant initial micro-cracking in which the flow could occur. Residual properties, at room temperature, were measured after thermal treatments at 150 or 250 degrees centigrade. These heating phases led to an increase in porosity and permeability being sevenfold its initial value after a 250 degrees centigrade treatment. This increase in permeability comes from two distinct effects that can be experimentally described: A pore widening observed with the Klinkenberg effect being lower, and a micro-crack closure occurring with the increase in confining pressure. Permeability was also measured with gas injection in samples submitted to thermal loading and slightly confined. Three levels of temperatures were used: 25, 105 and 200 degrees centigrade, and in a first stage, the permeability remained nearly constant to finally significantly increased at 200 degrees centigrade. At 105 degrees centigrade, there was a widening of pores observed with the Klinkenberg effect but not sufficient to vary the permeability. At 200 degrees centigrade, micro-cracks did occur, but their influence upon permeability was lower than for the treated material, an effect of the confining pressure applied on the material during heating. This study was part of a larger experimental program that characterized the effects of increasing temperature upon the hydraulic properties of cement-based materials.

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  • Authors:
    • Lion, M
    • Skoczylas, F
    • Lafhaj, Z
    • Sersar, M
  • Publication Date: 2005-10

Language

  • English

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Filing Info

  • Accession Number: 01011036
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Nov 23 2005 1:20AM