Global warming, energy savings, and life cycle analysis issues are factors that have contributed to the rapid expansion of plant-based materials for buildings, which can be qualified as environmental-friendly, sustainable and efficient multifunctional materials. This review presents an overview on the several possibilities developed worldwide about the use of plant aggregate to design bio-based building materials. The use of crushed vegetal aggregates such as hemp (shiv), flax, coconut shells and other plants associated to mineral binder represents the most popular solution adopted in the beginning of this revolution in building materials. Vegetal aggregates are generally highly porous with a low apparent density and a complex architecture marked by a multi-scale porosity. These geometrical characteristics result in a high capacity to absorb sounds and have hygro-thermal transfer ability. This is one of the essential characteristics which differ of vegetal concrete compared to the tradition mineral-based concretes. In addition, the high flexibility of the aggregates leads to a non-fragile elasto-plastic behavior and a high deformability under stress, lack of fracturing and marked ductility with absorbance of the strains ever after having reached the maximum mechanical strength. Due to the sensitivity to moisture, the assessment of the durability of vegetal concrete constitutes one of the next scientific challenging of bio-based building materials.

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In this study, we investigated the influence of the addition of sisal and glass fibres on the mechanical properties of polymer concrete (PC). These types of concrete are used in many modern civil engineering applications. The prismatic specimens sized according to ASTM C580-02 were elaborated with a PC constituted by 14% constant mass of polyester resin matrix, a granular skeleton based on sand and powder marble. The reinforcement with 60% sand and 26% marble powder adopted in this investigation is the best formulation found in previous authors work. This composition was reinforced by 1 and 2% of sisal and glass fibres, the first one having lengths of 6 mm or 12 mm, however, the second unidirectional cut into bands. These specimens were subjected to 3-point bending monotonic loading. The results obtained were discussed and compared with those obtained for control beams without fibres reinforcement. It is important to note that the incorporation of the glass fibre contributes to an increase of the ultimate load of the polymer composite material produced, however, the addition of the sisal fibre lead to its decreases. In addition, the incorporation of 2% of sisal fibre having 6 mm length leads to a reduction of 26% of the mass of the specimens.