In a method for manufacturing slabs which are thin (10-30 mm) and broad, a cement mix comprising water, cement and a fluidizer is mixed with inert stone aggregate having a controlled particle size. The resultant mix is deposited in a predetermined thickness onto a temporary support and subjected to vacuum vibrocompression. The slab thus formed is subjected to the steps of setting and hardening by means of curing, enclosing it between two thin sheets of plastic impermeable to water vapor which are hermetically sealed along their edges. The method envisages specific measures as regards the method of mixing performed during the steps of preparation of the cement mix and mixing of the cement paste with the stone aggregrate. Other improvements concern the components of the cement paste as well as the order of introduction of the aggregate during mixing with the latter.