Tannic acid/ethanolamine modification of PE fiber surfaces for improved interactions with cementitious matrices

The paper at hand deals with the surface functionalization of polyethylene (PE) fibers by using tannic acid/ethanolamine (TA/EA) as an affordable and highly effective approach in enhancing the bonding characteristics in cement-based matrices. Surface morphology, charge formation, wetting behavior, and thermal properties of the fibers were investigated using environmental scanning electron microscopy (ESEM), electrokinetic measurements, water contact angle tests, and thermogravimetric analysis (TGA). Both one-sided and two-sided, single-fiber pullout tests were carried out to shed light on the effect of TA/EA deposition on the interactions between the cementitious matrix and the modified fibers as regards various EA concentrations and treatment durations. For the samples with the modified PE fibers notable enhancements were observed in interfacial shear strength, pullout energy, crack-bridging force, and crack-bridging energy when compared to the samples containing raw PE fiber. This is explained by the effective surface activation of PE fibers by TA/EA through introducing amino and hydroxyl groups onto the fiber surfaces, thus providing more reactive groups with the cement hydrates and yielding improved bonding in the fiber-matrix interfaces. Moreover, the TA/EA coatings not only showed no negative impact on the mechanical behavior of the fibers but even slightly enhanced their tensile strengths and moduli of elasticity.