Analysis of water droplet penetration in earth plasters using X-ray microtomography

• Published in: Construction & building materials Vol. 283; p. 122651
• Main Authors: Mauffré, T., Keita, E., Contraires, E., McGregor, F., Fabbri, A.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 10.05.2021; Elsevier
• Subjects: Drying rate; Earth plasters; Engineering Sciences; Surface topography; Water damping; Water penetration; X-ray microtomography; Drying rate; Water penetration; Water damping; Surface topography; Earth plasters; X-ray microtomography
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2021.122651

•Water damping droplet penetration followed by original X-ray microtomography.•Spread, depth and quantity of the droplet monitored inside the earthen plaster.•Surface topography has a direct link with the inertial water penetration.•After impact, water behavior is only influenced by bulk properties of the plaster.•A clayish plaster prevents water to penetrate too deeply but has a slow drying rate. Earth plasters are a very interesting solution for the coating of earthen construction, in terms of embodied energy, technical efficiency, while keeping the hygroscopic properties of the wall, unlike very little permeable coatings, as the cement-based ones. An experimental campaign has been conducted on several earth plasters which differs by their sand granulometry, earth origin and earth to sand ratio, leading to controlled surface topography and bulk properties. A novel X-ray microtomography technique adapted to such material has been relevant to observe directly the penetration of a water damping droplet inside the plaster with the 2D radiograph method, and enhance the understanding of the role of the surface and the bulk structure on it. A 3D scanning method was useful to understand the microstructure of the different samples and analyse their differences in terms of porosity. Two custom-made MATLAB codes have been developed in order to follow the droplet parameters inside the material, such as the spread, the penetration depth and the relative quantity of water along the time. Results show the consistent role of the surface topography on the water inertial penetration, while the penetration rate due to diffusion is directly linked to the bulk properties, and can be assimilated to a classic diffusion solution. The determination of the drying rate in the earth plasters highlights that the plasters which prevent the water to penetrate too deeply are also the ones which dry the slower, leading to a questioning on the role researched in an efficient coating material.