Evaporation process and tensile behavior of fiber-reinforced rammed earth

The rammed earth is an environmental-friendly building material. Its mechanical properties draw lots of attention among researchers and engineers in recent years. In order to improve the tensile performance of the rammed earth, the fiber-reinforcement is applied to better modify its properties. A series of compacted rammed earth samples with different fiber contents (0~0.2%), initial water contents (16.5%~20.5%) and dry densities (1.5~1.7 g/cm³) are prepared by simulating the natural air-drying process of rammed earthmaking. The splitting tensile tests are carried out on the air-dried rammed earth samples. The effects of fiber content and initial state on the evaporation process and tensile strength of rammed earth are analyzed. The results show that: (1) The fiber content has few influences on the evaporation rate of the reinforced rammed earth. But with the increase of the fiber content, the residual moisture content of the reinforced rammed earth decreases first and then increases. (2) The fiber inclusion can significantly improve the tensile strength of the rammed earth, but the contribution of fiber reinforcement to strength increment will be reduced beyond a certain fiber content. The optimum fiber content for Xiashu soil in Nanjing area is observed at 0.1%. The fiber inclusion can also modify the brittle failure mode of the rammed earth to ductile one so as to improve the residual tensile strength and toughness of the rammed earth. (3) Increase of the initial water content and the initial dry density can significantly improve the tensile strength and the fiber reinforcement benefit. (4) The micromechanical interaction of the fiber-soil interface and the "bridging" effect of the fiber are the key factors controlling the overall tensile behavior of the fiber-reinforced rammed earth.