# Comparison of Field and Laboratory Tests for Soil Suitability Assessment in Raw Earth Construction
## 1 Introduction
Understanding these relationships is crucial for predicting how different materials will behave and for selecting the right soils for specific construction methods. However, [PERSON] et al. [32] emphasized that these criteria should be viewed as guidelines rather than absolute rules, as successful earth construction has been achieved with soils that fall outside these recommended ranges, providing that appropriate modification or stabilization techniques are applied. Even though the market for new-build earthen structures is growing, the lack of design code is limiting their construction [33]. In addition, the different guidelines can sometimes give contradictory soil assessments, and, in some cases, the assessments might be questionable [34]. Many techniques exist and can be adapted to locally available soils, climates, and social factors (esthetic and local construction culture) [35]. [PERSON] et al. [8] developed a systematic assessment framework for earth construction that evaluates soil suitability based on multiple criteria. Their methodology considers not only technical aspects but also environmental, economic, and cultural factors. [PERSON] et al. [36] showed that there is also variability between laboratory and in situ mixes and thus, the need for correction factors and on-site tests to test the performance and homogeneity. [PERSON] et al. [37] proposeda novel methodology to identify soil characteristics to be employed in vernacular earth buildings based on the cross-referencing of pedological and heritage data. [PERSON] et al. [38] implemented a decision support tool for soil analysis to assist archeologists in dealing with soils and documenting information about an excavation. [PERSON] et [PERSON] [28] analyzed soil suitability of unsterilized earth considering different approaches and recommendations based on 20 technical and normative documents and standards. They showed that the particle size distribution was the most mentioned followed by the OM and salts content. However, the other properties such as compactibility, plasticity, shrinkage, presence of cracks, and binding force were imprecise and variable. Thus, there is a need to unify the work for soil selection as a construction material. In the Nouvelle-Aquitaine region, a growing demand for raw earth construction is observed, and one of the difficulties in implementing this type of construction is the lack of knowledge about the potential of local earth resources. The historical earth constructions known today in this region do not allow us to affirm that the territory is more conducive to one technique than another. Several projects, such as the [des terres] project, are underway to disseminate knowledge about the particularities of earth construction through designers, construction companies, tools, and methods. Within this project's framework, this study seeks to answer the following questions about the local resource: What earth resources are available in the Nouvelle-Aquitaine region? And for which construction technique are they adapted? By evaluating the variability related to the nature of the earth considering the soil location and history, the choice of the construction techniques can be better determined. Two approaches have been considered regarding earth construction: the raw earth mason with simple, artisanal, and sensitive tests for characterizing the earth; and a geotechnical approach, based on the standards for earth characterization tests, used today by geotechnicians and researchers. It aims to bridge the gap between practical field experience and scientific understanding of earth construction while providing guidelines for preliminary soil assessment. A comprehensive experimental program was implemented on 39 soils from the Nouvelle-Aquitaine region, combining both field and laboratory testing methods. The field assessment included different tests commonly used by earth construction practitioners, such as sensory evaluations, plasticity tests, and cohesion assessments.