Before the Installation of a Concrete Layer, High -quality Preparation of the Base from the so soil is recept. For this, it is Necessary to Scatter on Top of the Earthen Surface with One Layer of Gravel Or Crushed Stone. Sprinking Material FRACTIONS SHOULD Be in the RANGE of 40 — 60 MM. Crushed Stone (Gravel) Scatted Over. When Preparing a Concrete Surface for Applying Waterproofing Layers, A Bitumen -BASED VAPOR BARRIER OR ANTI -CORROSION Protective AGENTS, IS Necessary to Monator and Check The CONCRE TE Surface for the Absence of Chips and the Possible Present of Ribbed Elements.