This paper presents the results of an experimental research aimed at assessing the material performance of adobe bricks in compression for a wide range of induced strain rates, from statics to high velocity impact. Adobe connotes a traditional masonry whose bricks are made of sundried soil mixtures possibly reinforced with natural fibres and joined together using mud mortar. The inclusion of fibre and the presence of water in the mixture have a dominant effect on the mechanical performance of adobe bricks and masonry. Their influence on the dynamic behaviour of this material is quantified and interpreted in this study at high strain rates also with data produced through Hopkinson bar testing. Appropriate dynamic increase factors and constitutive equations for adobe materials in dynamics are also investigated. The paper presents the experimental campaign, shows the main results and offers qualitative and quantitative interpretations for the principal damage patterns observed.@en

Adobe is one of the most ancient forms of masonry. Adobe bricks are sundried mixtures of clay, silt, sand and natural fibres locally available joined together using mud mortar. Adobe structures are largely spread in areas of the world prone to earthquakes or involved in military conflicts. Unfortunately, almost no literature concerns the dynamic assessment of soil-based masonry components. From earlier research, it was derived that the mechanical behaviour of adobe in statics fits in the class of quasi brittle materials. Its resemblance with cementitious materials concerns the main failure modes and the constitutive models in compression. This study deals with the experimental characterization of adobe components response in dynamics. It is aimed to study and quantify the rate sensitivity of adobe material from bricks at a wide range of strain rates, from statics up to impact conditions. In particular, the influence of fiber reinforcement in the mixture on the mechanical behaviour of the material has been addressed. Adobe bricks are commonly mixed using organic content locally available in the field, from straw to chopped wood. Fibres are added to prevent shrinkage cracks during the air drying process. In modern materials such as concrete, inclusion of artificial fibres is originally meant to enhance the mechanical performance of the material, benefiting from the selective properties of reinforcement and binder. An experimental campaign was carried out in a collaboration between Delft University of Technology, Dutch Ministry of Defence, TNO and the Joint Research Centre (JRC) of the European Commission. Two types of bricks were tested. They both had the same soil composition in terms of mineralogical family and soil elements proportions but only one was mixed using straw and wood. Cylindrical samples were subjected to compression tests at different rates of loadings in compression: low ( _ 1 = 3 104 s1), intermediate ( _ 2 = 3 s1) and high ( _ 3 = 120 s1). High strain rate tests were performed using the split Hopkinson bar of the Elsa-HopLab (JRC). For each test, high resolution videos registered the failure process and force-displacement plots were recorded. Elaboration of results revealed clear trends in the dynamic material behaviour. Adobe, as concrete, is sensitive to the loading rate. The rate effects on the main properties of the material in strength and deformation are also analytically and numerically quantified. Rate sensitivity and failure mode are significantly influenced by the inclusion of fibers in the mixture. These effects are quantified, interpreted and compared with modern SFRC. This paper presents the experimental campaign and the obtained results. Moreover, physical interpretations for the observed trends are discussed. Finally, new formulations for the assessment of the dynamic increase factor of the compressive strength of adobe are proposed.@en