Earth as a building material is increasingly being studied for its low environmental impact and its availability. Plant aggregates and fibers have been incorporated into the earth matrix in the aim of enhancing performance for thousands of years but scientific studies began quite recently. The present paper reviews the state of the art of research on the influence of these various natural and renewable resources in unfired earth materials such as compressed earth blocks, plasters, and extruded and stabilized blocks. This review, based on 50 major studies, includes characterization of the particles and treatments, and recapitulative tables of the material compositions, and the physical, mechanical, hygrothermal and durability performances of earth-based materials. A lack of references on hygroscopic and durability properties was observed. Future research orientations are thus suggested to promote and develop this type of sustainable material, which provides a solution for saving energy and natural resources. Highlights Earth-based products with plant aggregates as a sustainable material are reviewed.  Physicochemical and mechanical properties of plant aggregates or fibers are reviewed.  Mechanical, hygrothermal and durability performances of the composites are reviewed.  Further investigations are needed to promote these materials.

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. From the experimental characterization of the hygrothermal properties of straw-clay mixtures to the numerical assessment of their buffering potential. Building and Environment, Elsevier, 2016, 97, pp.69 -81. 10.1016/j.buildenv.2015 1 From the experimental characterization of the hygrothermal properties of straw-clay mixtures to the numerical assessment of their buffering potential ABSTRACTThe development of innovative materials has to respond to both environmental and energy concerns. Bio-based materials are relevant because they are made from renewable raw materials and are carbon neutral. Similarly, unprocessed earth has a very low embodied energy. In this paper, the basic hygrothermal properties of straw-clay samples provided by two French companies were determined. Mixes with densities lower than 450 kg.m -3 would be suitable for use as self-insulating material in current construction. In addition, the material showed a high sorption capacity and very high water vapour permeability. The measurements were then implemented in a numerical model in order to simulate the hygric response of a small room. The straw-clay mixture was found to have a moisture buffering effect of the same magnitude as walls made of hemp concrete and largely higher than conventional walls. The influence of various indoor finishing materials was investigated through additional simulations.

There is an increasing demand for earth construction in the world today but there is no consensus on the procedure to be used to measure the compressive strength of earth bricks. The study presented in this paper aims to propose a test procedure specific to earth bricks that would give the most realistic value of compressive strength while remaining as simple as possible. This study focused on four different bricks and consisted of measuring the compressive strength of these specimens by varying several parameters: specimen size, orientation, use of Teflon capping or not, and tests on dry sawn specimens, on half-bricks or on entire bricks. The results of the study show that the best compromise to achieve a simple and representative compressive strength test for earth bricks is to transform the bricks as little as possible before the test and thus to test entire bricks.