Adobe Bricks of the Champagne Region (France): Characterization of a Chalky Raw Earth Construction Material.

Raw earth bricks made from the soil of the Chalky Champagne region (France) have been used for at least two millennia in construction, a promising heritage in the context of reducing the carbon emissions of buildings. The present experimental study aims to measure the physical, mechanical, thermal, and hydric properties of adobes collected from a local village barn. The results show a high chalk content, estimated at 71%, and a clay content, acting as a binder, of 14%. Despite limited load-bearing capacity, these lightweight adobes are suitable for current single-story constructions, while their hydrothermal properties classify them as excellent moisture regulators for occupants. In association with other bio-sourced materials such as starch-beet pulp bricks, Chalky Champagne adobes yield promising insulating properties, and meet the criteria defined by current energy standards.

Use of micro-climatic monitoring to assess potential stone weathering on a monument: example of the Saint-Remi Basilica (Reims, France).

Temperature and humidity variations influence various weathering processes of historical building stones. The aim of this study is to define the possible micro-climates on a monument in order to identify the recurring stress events, allowing to assess the potential stone weathering. For this purpose, a sensor network was set up on the two towers of the Saint-Remi Basilica of Reims: fourteen i-Buttons recorded temperature and relative humidity for 2 years with a time step of 1 h or 2 min for short measurement campaigns. Two micro-climates were identified: the sunny micro-climate (areas oriented South and West) presenting higher temperatures and lower relative humidity than the shadowed micro-climate (areas oriented North, East, and other shadowed zones). On the micro-climates, three typical days (Sunny, Rainy, and Frost days) were determined and allowed to fragment 1 year in a succession of these days. Short temperature variations (1 ∘C/min) due to cloud cover were also identified during the sunny days, thanks to the shorter time step of 2 min. The stress generated during the typical days could then be estimated. Depending on the repartition of typical days for each micro-climate, some weathering processes could be favored: concentration of stress near the surface on the sunny micro-climate, development of biological colonization, and harsher frost events for the shadowed micro-climate. Taking into account the properties of the main limestones present on the basilica, the weathering on-site could be explained.

Laminar gypsum crust on lede stone: Microspatial characterization and laboratory acid weathering.

Gypsum crusts are typical decay forms on limestone in polluted urban environments. Their origin and relation to the stone facies have been thoroughly investigated in the past three decades. Here, we present the combined use of novel techniques for a microspatial structural, chemical and mechanical characterization of a laminar black gypsum crust on a sandy limestone. These techniques include i.a. X-ray computed microtomography, X-ray Fluorescence micromapping, permeability mapping and the scratch test. They reveal the typical architecture of a laminar gypsum crust, with an outer opaque layer, a subsurface gypsum crystallization layer and a deeper cracked zone passing irregularly into the sound stone. Gypsum crystallization is mostly restricted to an irregular outer zone with an average thickness of 500µm, while cracks are found deeper within the rock. These cracks decrease the rock strength to more than 27.5mm below the surface. Because of their surface parallel orientation and thickness of >10-100µm, they create the potential for surface scaling. This is shown by a laboratory acid test where the crack network extensively developed due to further exposure to an SO2 environment. The use of novel techniques opens potential for the study of different decay forms and can be used for stone diagnosis with regards to conservation studies.