The invention relates to a cementitious composition suitable to be moulded, in particular injection-moulded, to make a manufactured product with arithmetic average surface roughness Ra not higher than 500 nm and flexural tensile strength not lower than 5 MPa, measured after 28 days of curing, the fluidity of the composition, measured according to the method of standard UNI 7044, being not lower than 185 mm, characterised in that it comprises at least: I. a hydraulic binder II. one or more aggregates III. an anti-shrinkage agent IV. a superplasticiser agent V. fibres VI. water, wherein said fibres are made of an amorphous metal material consisting of an alloy with composition (Fe, Cr) 80 (P, C, Si) 20 in form of flexible lamellae of length equal to at least 10 mm and elastic modulus equal to at least 80000 MPa, present in the composition in amounts by weight of less than 4% with respect to the weight of the composition.