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Thin films of polydopamine (PDA) were applied successfully as bio-inspired adhesion promoters in strain-hardening cementitious composites (SHCC) reinforced by polyethylene fibers. In the present study, this technique was used to produce SHCC with a more sustainable matrix based on Limestone Calcined Clay Cement (LC 3 ) providing a lower CO 2 footprint. Furthermore, PDA was combined with polyelectrolytes in order to tailor the fiber-matrix interaction by introducing additional reactive groups and to improve the chemical stability of the adhesive fiber coating. In a first step, PDA was co-deposited with poly(ethylene imine) (PEI) to increase the number of alkaline amino groups and thus intensify the alkaline character of the fiber surface. In a second step, a layer of poly(ethylene-alt-maleic acid) was adsorbed onto the PDA-PEI layer to create acidic functionalities. To test their stability in alkaline media, the fibers were stored in alkaline solutions (pH 13) for 14 d. The effect of the coating and the alkaline treatment on the topography and surface properties of the fibers was investigated by scanning force microscopy, zeta potential, and contact angle measurements. Single fiber tensile and pullout tests show enhanced mechanical properties and better adhesion of selected modified fibers in the LC 3 cement matrix.
Frenzel et al. (Sun,) studied this question.