Cementitious materials are hard but very brittle. They need reinforcement to improve their low crack resistance. A promising solution for lightweight applications is the addition of short fibres that are able to bridge small cracks. The fibre-reinforcement is able to produce strain-hardening cementitious composites (SHCCs) if the interaction between fibres and matrix is well-balanced. The study presented in this poster introduces the use of more sustainable materials for the preparation of SHCCs: novel Limestone Calcined Clay Cements (LC3) matrices and fibres made of recycleable polymers as polyethylene, polypropylene and polyethylene terephthalate. The fibre-matrix adhesion is adjusted by coating with polydopamine (PDA), a bio-molecule used e.g. by mussels to adhere to various surfaces. Thanks to various functional groups, PDA is able to promote adhesion between various materials but the layer lacks stability in alkaline media as fresh cement. Addition of alkaline and acidic polyelectrolytes or cross-linking agents after DA modification was performed to improve the chemical stability of fibres and coatings and to introduce different acidic and alkaline surface groups to tailor the interaction with the cement matrix. The effect of the modification has been investigated by surface-sensitive techniques, as scanning force microscopy (AFM), X-ray photoelectron spectroscopy, and zeta potential measurements. Fibre characterization after long-term storage in alkaline solutions revealed differences in the chemical stability of the modified fibres. The interaction with cement was evaluated by single-fibre pullout tests.