Effect of the Fibre Type on the Rheological and Mechanical Properties of Cementitious Composites for Thin Overlays

Polypropylene (PP), nylon and polyvinyl alcohol (PVA) micro-fibres with different geometries were used at 1 vol. % dosage to investigate rheological and mechanical properties of cementitious composites to be used for thin overlays. Slump-flow and visual stability index methods were used to characterise the rheological properties. Single crack tension and bending studies were carried out to evaluate the tensile and bending strength, as well as the post-cracking behaviour. The results show that fibre geometry (L/d ratio and specific surface area) has a pronounced influence on the fresh state rheological properties of the cementitious composites. The results also surprisingly indicated that the nylon fibres are able to significantly increase the pre-cracking tensile and bending strength. All tested composites showed tensile strain softening and insignificant deflection hardening after cracking and a major strength loss. The results indicate single crack tension method to be the most appropriate for evaluation of mechanical properties of cementitious composites used for thin overlays.