Influence of Diffuse Damage on the Water Vapour Permeability of Fibre-Reinforced Mortar

Abstract

The study of moisture transfer inside building materials is an important issue in building physics. The hygric characterization of such materials has become a common practice for the estimation of the hygrothermal performance of buildings. However, their aging caused by mechanical loading and environmental factors inevitably affects their permeability to moisture ingress, and the knowledge of how this permeability is affected by damage and cracks is still incomplete.The effects of diffuse damage caused by mechanical loading on the water vapour permeability of fibre-reinforced mortar were studied. A full experimental setup is presented including observation of the porous structure, mechanical, and hygric characterization. Uniaxial tensile loading was applied on prismatic samples while their damage level was measured. Then, the moisture content of damaged and undamaged samples was monitored during variations of ambient relative humidity. Two numerical methods are presented and used for the comparison of the water vapour permeability of multiple samples presenting various levels of damage. By this methodology, diffuse damage caused by mechanical loading is shown to have an impact on the water vapour transfer inside the material.

Digital Image Correlation

“…The camera Figure 1: Experimental setup for tensile loading and damage monitoring was used as an optical extensometer to monitor the macroscopic strain in the direction of loading. The material presents some ductility before the peak of loading [27], followed by a strain-softening behaviour during which crack propagation is slowed by the presence of fibres. This behaviour facilitated the process of progressive damage monitoring by acoustic and optical measurements.…”

Coupled hygro-mechanical multiscale analysis of masonry walls

“…As regards the reverse coupling, that is the modification of moisture diffusion due to mechanical effects, it should be noted that the mechanical degradation of a brittle composite material like the masonry can be subdivided in two phases [25]: a first phase where diffuse micro-cracking appears, followed by a second phase where macroscopic cracks exert. In both the cases, cracks have been shown to have a significant impact on transport processes in general, and on moisture diffusion in particular (see for example [26][27][28]). Focusing the attention on the first step of mechanical degradation, which is characterized by diffuse micro-cracking and allows the description of the mechanical behavior through the classical damage mechanics, a commonly used approach to take into account for the effects of the mechanical damage on moisture diffusion process is to modify coefficients C g h and C l h through a correction function depending on the mechanical damage variable b:…”

“…As regards the correction functions g g d and g l d , experimental results available in the literature for fiber reinforced mortar [28] and for concrete [27] show a different behavior of water vapor permeability and liquid water permeability with respect to the damage variable. As regards the vapor water permeability, it increases up to intermediate damage values and then decreases for large values of damage.…”

Influence of concrete fracture on the rain infiltration and thermal performance of building facades

“…1 for the prediction of moisture flow requires the knowledge of the material's equilibrium moisture content w = f p c , as well as its unsaturated moisture permeability. Simulations performed in the present work involve five different materials, two of which have undergone hygric characterisation in previous papers [31,29], while the properties of the three other materials have been extracted from the literature. The geometries of the simulation cases, along with the corresponding references for material properties, are defined in Sec.…”

“…The moisture transport and storage properties of concrete and mortar have been previously characterised [31,29]. Their thermal properties, were taken from databases or from the literature concerning similar materials [15].…”