A review of non-destructive testing methods for structural health monitoring of earthen constructions

Earthen construction techniques possess without any doubt a rich historical legacy, being able to assess an efficient combination of structural stability, thermal mass properties, and low environmental impact, which leads to their current renewed interest as key direction for sustainable building practices. Additionally, earthen buildings and the associated techniques, related to material, structural design, building solutions, etc., represent key testimonies related to the cultural local and traditional legacies all over the world. Earthen buildings, vernacular or developed by using qualified personnel such as craftsmen and traditional masons, use different techniques and construction technologies (rammed and poured, load-bearing walls, adobe, mixed wood-earth structures, etc.), and were developed differently with respect to the region where they were used. Generally, due to superposition of many factors, the interest towards the earthen materials and techniques in construction areas are gaining popularity. In this context, the aim of this research is to provide an overview of the nondestructive methods used for analysing earthen constructions in terms of structural integrity and overall performance, considering a major focus on rammed and poured earth-building techniques. The current research intends to identify and consider the advantages, limitations, and applications of NDT techniques in the context of earthen construction, also promoting potential further research and development in the field of non-destructive evaluation for earthen materials. Throughout the study, various non-destructive testing methods will be reviewed from the perspective of their actual suitability in the area of materials, element and structure analysis. Case studies demonstrating the practical applications of NDT in earthen structures are emphasised, together with identified challenges in non-destructive testing applied in the considered topic of use.