Inoxidizable flexible fibres in amorphous iron and chrome alloy to be added to Mapegrout FMR to improve its ductility. Fibres FF are composed of a special amorphous iron and chrome alloy. The flexibility and high aspect ratio (length/diameter) of Fibres FF make mortars highly ductile and shock resistant. All the Mapegrout range mortars can be reinforced with the addition of 1.0-1.5% Fibres FF by weight (approximately 20-30 kg/m3 of prepared mortar) of the dry ready mix.