Mechanical enhancement of casted and compacted earth-based materials by sand, flax fiber and woven fabric of flax

Abstract

Earth-based materials are commonly reinforced with bio-based materials such as straw. In this study, we use high performance bio-based flax fibers and fabrics. The aim of this work is to find reinforcements that are able to improve the mechanical strengths and the ductility of an earthbased matrix. We also try to describe the reinforcement mechanisms are also described. In a first step, a kaolinite-based clay soil is mixed with sand to design earth-based mortars with the highest density at the dry state. The sand dosage is found using mix-design method commonly used for concrete. We show that, at the same water content, the compressive strength at the dry state only depends on the dry density of the sample (and does not depend on forming process and use of dispersant). In a second strep, the mix-designs exhibiting the highest compressive strengths are chosen for both casting and compaction. Then, different amounts of fibers or fabrics are used to reinforce the studied mortars. We found that those reinforcements significantly increase the compressive strength of all tested samples. This result is very interesting because this is not always the case for other mineral matrix such as mortar and concrete. Such comparison with concrete helps us to understand the reinforcement mechanisms for fibers. This study shows that concrete mix-design methods are very helpful to increase the density at the dry state and the mechanical strength of earth-based materials. It also highlights that natural fibers and woven fabrics really enhance the mechanical behavior of earth even for compressive load.