The invention concerns a method and a grouting composition for filling cracks in stone and concrete structures. According to the method, the cracks are filled with a composition containing a binder which achieves setting of the composition under the influence of water, whereby the cracks are filled. The grout contains a latent hydraulic binder, an alkaline component for activating the binder, additives and aggregate having a particle size of less than 1.6 mm. The grout is easily formulated to a suitable viscosity determined by the intended use by varying the relative amounts of binder, activator and aggregate. The grouting composition has good anti-wash-out properties, enabling its use for filling even cracks where strong water flow occurs.