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
... [Show full abstract] 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, intermediate and high. 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.