Effect of wetting/drying cycles on the durability of flax fibers reinforced earth concrete

Earth concrete is composed of fine particles which make them very sensitive to humidity and affects their longterm durability. In this study, the effect of wetting/drying cycles on earth concrete according to ASTM D559 was studied by measuring the weight loss, pH, and Electrical Conductivity (EC). The effect of different percentages of flax fibers was investigated. The residual properties of reference specimens and earth concrete specimens subjected to wetting/drying cycles were evaluated by conducting compressive tests at the end of the 25 cycles. Ultrasound, Acoustic Emission (AE), and Digital Image Correlation (DIC) techniques were applied to estimate the concrete progressive deterioration during and at the end of the 25 wetting/drying cycles. The results showed that earth concrete degradation begins during the first cycle with visible cracks on the surface of the specimens. The mechanical tests showed a considerable loss of earth concrete mechanical properties after 25 cycles. The ultrasonic test showed that the degradation rate was more important for specimens without flax fibers. The cumulative acoustic activity was effectively used to assess the different damage progression phases and crack propagation. The signal parameters (energy, amplitude, etc.) evolution indicates premature damage for earth concrete specimens subjected to wetting drying cycles.