An overview on contemporary rammed earth buildings: technological advances in production, construction and material characterization

Abstract

Raw earth is a traditional material used worldwide in vernacular architectures. For its wide availability, recyclability and low embodied energy in its life cycle, earth is acknowledged as one of the most environmentally sustainable material. Earth construction diffusion has been slowed by the lack of broadly accepted standards. Due to it, earth has been used as an artisanal material or adapted to existing technologies in combination with high embodied energy materials as steel, concrete and EPS or PU insulations (as in rammed earth technique, from now on RE). Aim of the research is to propose an innovative RE constructive technology, more coherent with the sustainable features of the base material, which can reach the high performances and the quality target required by the constructions sector using a low-tech prefabrication process. Prefabrication of RE elements can also reduce the construction times and the risks of technological faults, enhancing the quality of the entire building. The basic idea is to create manageable and transportable rammed earth panels with superior mechanical and thermal performances. The prefabrication under controlled conditions ensures a high-quality product which can be combined, on site, with a reinforcing timber structure with anti-seismic function. A characterization campaign on different local soils has been performed in order to implement the desired RE elements. The soils have been analysed with a set of geotechnical tests and qualitative assessments in order to detect their suitability for constructions. Once a suitable soil has been identified, a physical and / or chemical stabilization is needed to improve the physical features, mechanical characteristics and thermal properties of the natural soil. In the last section of the paper, the first results on natural local soil and engineered soil (an optimized mix of soil, sand and gravel) are presented and compared to identify a suitable material for the RE panel.