Described herein is the use of new cementitious mortars with a high degree of fluidity and short consolidation times in the production of cementitious products by means of pouring in foundry moulds. The mortars used contain water, a fast-setting cement, fluidifiers and/or superfluidifiers, setting regulators, and aggregates having a specific granulometric distribution. The aggregates are made up of two fractions with different grain size such that the ratio between the characteristic grain diameters of the two fractions is comprised between 2.2 and 3.2. The new mortars thus obtained have values of fluidity 2-3 times higher than those of mortars produced with traditional aggregates. The mortars thus produced are particularly suitable for filling, in a homogeneous way and without any application of vibration, foundry earth moulds; solidification in the moulds takes place in a short time and leads to the formation of products, including ones of a complex shape, with precise outlines and having good mechanical characteristics.