On-site testing of joint shear strength in masonry constructions: an experimental study in a traditional adobe building in Portugal

In the last decades, earthen constructions have long been debated in the civil engineering and architecture community. Two are the focal points at the center of this debate: on one hand, the rediscovery of earth as an eco-friendly and easily available material, which can be used for the design of new constructions; on the other hand, the recovery, restoration and structural reinforcement of the existing buildings, particularly sensitive to degradation phenomena and vulnerable to seismic actions. Portugal has a significant heritage of earthen constructions. Currently, many vernacular buildings, especially in the district of Aveiro, are still in use and some of them have historical and artistic value. However, many of them are in poor state of conservation and many of the incurred problems are due to the lack of in depth knowledge of the materials and construction systems traditionally used. In this contest, the present study aims to increase the knowledge of adobe constructions in Portugal concerning the characterization of the material and its mechanical properties, such as the uniaxial compressive stress in some adobe samples and the shear strength of masonry joints, to have valid instruments for the recovery and conservation. These data are achieved through the development of some diagnostic testing carried out on site on a vernacular building in Aveiro region, which were integrated with laboratory tests in order to reach a better reliability of the obtained results. This research aims to prove the importance of tiling several diagnostic tests to optimize the knowledge of properties and mechanical characteristics of the tested material. This study also has the objective to draw up some guidelines and recommendations for future researches and to provide a valid contribution for all the future interventions of restoration, conservation and rehabilitation of earthen constructions, because earth is a not standardized material and still little investigated.