Role of the capillary fringe on the dilatation of a low porosity limestone submitted to unidirectional freezing

• Main Authors: Celine Thomachot-Schneider, Emilie Huby, Kevin Chalons, Xavier Drothière, Patricia Vazquez
• Format: Article
• Language: English
• Published: SpringerOpen 2018-11-01
• Series: Progress in Earth and Planetary Science
• Subjects: Frost weathering; Capillary fringe; Unidirectional freezing; Strain gages; Limestone
• Online Access: http://link.springer.com/article/10.1186/s40645-018-0213-6

Abstract As a rule, usually only one face of the building stones of a monument is exposed to climatic variations. Penetration of temperature and humidity stress is unidirectional from the external surface while capillary absorption comes from the bottom part of the accumulation zones such as soil or cornice band. This configuration has to be taken into account in the setting of frost weathering tests in the laboratory. Formation of ice is accompanied by changed volumes and by movements of liquid water due to cryosuction. These phenomena lead to the dilatation of the porous network as assessed by strain gage monitoring. In this study, an experimental setting was developed to simulate the condition of a building stone submitted to frost and water supply by capillary absorption. Strain gages and thermocouples were attached to a limestone sample in order to assess thermal penetration and dilatation changes. Two types of saturation conditions were applied to the sample: water supply only by capillarity and water supply by capillarity after immersion during 48 h. Freeze-thaw cycles of 24-h freezing at − 15 °C and 24-h thawing at + 10 °C were performed. Results showed that deformation perpendicular to the freezing direction was negligible except for the fringe zone where it could reach 6 × 10−4. In contrast, on both sides of the wet fringe, a deformation parallel to the freezing direction occurred, corresponding to an expansion upon freezing and a contraction upon thawing, with an intensity correlated in both cases to saturation. This original test also showed the importance of the capillary fringe in the frost action on building stones that is not taken into account in classical frost weathering tests. And it is to be noted that the strain gages allowed to measure immediate damage before it reached the inside of the stone and before it could be visually perceived.