Behaviour of rammed earth structures: Sustainable materials and strengthening techniques

Abstract

The research work focused on the possibility of building and modeling a structural system made with rammed earth strengthened with jute fabric. Earth is a natural building material used all over the world and. It has always been used in accordance with local traditions that are based on empirical knowledge. The preservation of traditional earthen masonry, as well as the practice of new construction, needs scientific knowledge of techniques and of physical and mechanical material properties. Acting with suitable devices, earthen buildings can be used even in seismic areas, guaranteeing acceptable safety. This research fits in the field of Fiber Reinforced Composites as reinforcement method for masonry structures with the aim to extend and adapt to natural fibers, test methods and data treatment procedures, useful to interpret the parameters that rule the materials behaviour and the interaction between parts. In order to design a reliable experimental technique to determine the necessary properties for the step of reinforcement system design, preliminary tests were necessary to assess the materials characteristics. Mineralogical, geotechnical and mechanical earth characteristics were investigated. Tensile tests on jute yarns and jute strips were carried out. The results were statistically analyzed in order to interpret the basic laws of scale effects. After materials characterization, the adhesion capacity of the reinforcement package composed by jute fabric and earth-gypsum matrix was investigated. The determination of the adhesion properties is considered a fundamental issue to produce specific rules that adequately support designers. An experimental campaign of adhesion tests of jute fabric strips applied on prismatic earth specimens was carried out to evaluate the adhesion properties of the strengthening system. The results are interpreted with existing analytical models. In order to improve the knowledge concerning this reinforcing technique and to verify the reinforcing ability of the jute fabric, an experimental program was carried out concerning the analysis of the mechanical behaviour of the reinforcement package applied to rammed earth arches subjected to asymmetric load condition increasing up to incipient collapse. The biocompatible reinforcement made with jute fabric and earthen matrix showed that it is possible to significantly increase the bearing capacity and the kinematical ductility of structural elements made with rammed earth.