Effect of fiber treatments on the sisal fiber properties and fiber–matrix bond in cement based systems

•Significant improvements in the fiber–matrix interface were verified by the used treatments.•The polymer coating resulted in a better frictional mechanism and in a slip-hardening behavior.•The alkali treatment removed the amorphous constituents of the fiber and increased its crystallinity.•The hornification increased the elastic and frictional fiber–matrix bond.

This experimental research investigation aims to explain the influence of several treatments on the sisal fiber properties and bonding strength with a cement based matrix free of calcium hydroxide. Four different treatments were studied: hornification, alkali treatment with calcium hydroxide, polymer impregnation with styrene butadiene and a combination of hornification and polymer impregnation. Modifications in the sisal fiber structure were investigated by X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infra-red spectroscopy (FTIR) and scanning electron microscopy (SEM). Water absorption and direct tensile tests were performed on the fibers to determine the influence of the treatments on their physical and mechanical properties. In order to study the sisal fiber–matrix bond, pullout tests were performed in fiber embedment lengths of 5, 10, 25 and 50 mm. All applied treatments resulted in a reduction of the water absorption capacity and increase in tensile strength and stiffness. Significant improvements in the fiber–matrix interface were verified through the pullout test for the several used treatments. The hornification treatment increased the elastic and frictional bond, whereas the polymer and hybrid treatments resulted in a fiber slip-hardening behavior.