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Knowledge of indoor air quality (IAQ) in cob buildings during the first few months following their delivery is of vital importance in preventing occupants' health problems. The present research focuses on evaluating IAQ in cob buildings through a prototype built in Normandy, France. To achieve this, the prototype was equipped with a set of sensors to monitor various parameters that determine indoor and outdoor air quality. These parameters include relative humidity (RH), carbon dioxide (CO2), nitrogen dioxide (NO2), ozone (O3), particulate matter (PM1 and PM10), and volatile organic compounds (VOCs). The obtained experimental results indicate that, overall, there is good indoor air quality in the prototype building. However, there are some noteworthy findings, including high indoor RH and occasional spikes in CO2, PM1, PM10, and VOCs concentrations. The high RH is believed to be a result of the ongoing drying process of the cob walls, while the peaks in pollutants are likely to be attributed to human presence and the earthen floor deterioration. To ensure consistent good air quality, this study recommends the use of a properly sized Controlled Mechanical Ventilation system. Additionally, this study explored IAQ in the cob building from a numerical perspective. A Long Short-Term Memory (LSTM) model was developed and trained to predict pollutant concentrations inside the building. A validation test was conducted on the CO2 concentration data collected on-site, and the results indicated that the LSTM model has accurately predicted the evolution of CO2 concentration within the prototype building over an extended period. [ABSTRACT FROM AUTHOR]

The suitability criteria for soils used in earth construction is investigated. Four soils collected from earth heritage buildings sites were studied. Cylindrical fibred and non-fibred specimen were produced using cob and adobe techniques. An experiment campaign was carried out to after drying and conditioning the specimen to study the implementation process effect, geotechnical properties and mineralogical composition influence on the hydromechanical and microstructural behavior of the specimens. The hydromechanical parameters like dry bulk density, unconfined compressive strength (UCS), Young's modulus (E) and suction of the specimen produced were studied. The pore volume and specific surface area were also determined using the BET technique. The collective impact of implementation process, geotechnical properties and mineralogical composition of the soils on the hydromechanical strength (UCS and Suction) and microstructure (pore volume, Specific surface area (SSA)) of laboratory produced cob and adobe specimens was studied. A statistical analysis was conducted using the principal component analysis to analyse the complexity of the interactions among the parameters. The analysis showed that aside the geotechnical properties of a soil, the implementation process and mineralogical composition of a soil also have high influence on the hydromechanical strength and microstructure of the earth specimen produced. • Suitability of soils for earth construction is studied for cob and adobe technique. • Fibred and non-fibred cob and adobe specimens are produced using 4 soils from earth heritage sites in France. • Aside geotechnical properties, the implementation technique and mineralogical composition affect strength. • The type and quantity of clay affects the intensity of mesopores present in earth specimen. • Clay is not the main mineral present in soil used in earth construction. [ABSTRACT FROM AUTHOR]

• There is no common agreement on how to assess soil suitability for earth building. • A large sampling campaign was achieved on rammed earth heritage buildings in France. • The samples were analysed through laboratory tests. • The tests included water content, dry density, sieving, hydrometer tests, MBV, PI. • Current classification systems relying only on granularity appeared inappropriate. • A classification system based on granularity and clay activity is recommended. In the European Union, most of the wastes from the building sector are composed of earths. Earth construction may be an interesting outlet for the re-use of these wastes, while meeting the challenge of circular economy: in particular, it involves low-embodied energy processes and earth material can be re-used for building by end-of-life. Nonetheless, the identification of suitable earths for construction remains an issue. To overcome this problem, an option may be to analyse earth building heritage, which is at least one-century old in Europe: indeed, earth employed in these buildings can be regarded as "time-tested", and thus suitable for construction. In this paper, more than 20 different earths collected in rammed earth heritage building in France are presented. The results are confronted both to literature and to several classifications employed in soil sciences. A classification system based on granularity and clay activity will be relevant to address the convenience of earth for building purposes. [ABSTRACT FROM AUTHOR]