Effect of flax fibers on early age shrinkage and cracking of earth concrete

•Study of the mechanical and early age properties of an ecological earth concrete.•Evaluation of the effect of flax fibers on plastic shrinkage and early age cracking.•Coupled analysis to distinguish plastic shrinkage mechanisms.•Monitoring of plastic shrinkage cracking with the digital image correlation. Earth concrete or concrete based on soil materials presents a high percentage of fine particles (clay) which makes it susceptible to plastic shrinkage cracking in its fresh state that affects its durability. In this study, natural flax fibers with different mass percentages (0%, 0.3% and 0.6%) and lengths (12 mm, 24 mm, 50 mm) have been added to earth concrete in order to study their effect on plastic shrinkage and cracking at early age. The effect of flax fibers on the mechanical properties of hardened earth concrete has been first investigated. Free horizontal plastic shrinkage has also been measured in parallel with the evaporation rate, the capillary pressure and the temperature of earth concrete at early age. Furthermore, restrained plastic shrinkage tests have been conducted according to ASTM C1579-13 standard. The Digital Image Correlation technique have been used to monitor the strain distribution and crack width during the first 24 h after casting. The results show a reduction of the total free plastic shrinkage at early age with the addition of flax fibers. In addition, flax fibers reduce the strain localization of restrained shrinkage and the plastic shrinkage cracking.