Applicability of micro-fibre reinforced cementitious composites for thin overlays in construction : effect of fibre type and dosage
2018
Lukasenoks, A., Riga Technical Univ. (Latvia) | Cepuritis, R., Norwegian Univ. of Science and Technology, Trondheim (Norway)
Nylon and polyvinyl alcohol (PVA) micro-fibres with different geometries were used in 1 vol. % dosage and polypropylene (PP) micro-fibres were used in 1, 1.5 and 2 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. Coupon samples (100 x 50 x 25 mm) were manufactured with a small notch (2 mm deep and 0.7 mm wide) for single crack tension tests and beam samples (40 x 40 x 160 mm) with a notch (5 mm deep and 0.7 mm wide) for bending tests. The results show that fibre geometry (Length/diameter (L/d) ratio and specific surface area) and fibre dosage have a pronounced influence on the fresh state rheological properties of the cementitious composites. Tested composites with 1 vol. % dosage showed tensile strain softening and insignificant deflection hardening after cracking and a major residual strength loss. Composite with 1.5 vol. % dosage shows only deflection hardening, but composite with 2 vol. % dosage shows both tensile strain and deflection hardening. Composite with 2 vol. % dosage reachesthe significant tensile strength of 1.77 MPa and bending strength of 12.47 MPa. The tests also indicated that fibres with L/d ratio is less than 120 can be practically used in mixes for the production of cementitious composites. By using this kind of fibres, it is possible to overcome technological problems that are associated with real production-introduction and dispersion large amounts of fibres, ensuring the stability of the mixture and casting a thin layer of the cementitious composite. Mechanical and rheological properties of the developed cementitious composites show great potential to be used in construction as thin overlays.
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