CAST-IN-PLACE REINFORCED CONCRETE
the typical foundation for outdoor paving
The importance of the foundation is significant for outdoor stone pavings, especially when intended for the transit of vehicles, as it is commonly identified with the same load-bearing layer, thus including in itself both the structural function and the guarantee of stability and solidity of the entire construction.
In ancient times the presence of the foundation was replaced by the use of heavy solid ashlars laid and beaten manually on layers of selected aggregates, the "Macadam" foundation, still used today for the construction of driveways, derives from this practice.
The foundation which is undoubtedly more use today, both for public and private constructions, is however the reinforced concrete foundation: a mixture of sand or gravel, water, cement in the minimum dosage of 200 kg/m3 cast-in-place by embedding sheets of electrowelded iron mesh having cross-section of min. 6 mm and 20x20 cm or 10x10 cm mesh. The thickness of a reinforced concrete foundation is commonly between 10 and 15 cm for light and occasional transit (for example foundations for private homes) or higher thickness for public roads according to precise design calculations.The construction of this kind of foundation is absolutely the most suitable for outdoor natural stone paving.
The possibility of obtaining a state-of-the-art paving depends on its correct construction, after the preparation of a sufficient and effective slope for the disposal of surface waters: slope of at least 1.5 cm for each linear meter (1.5 % or higher)
, with an adequate amount of water collection and disposal points in suitable positions.
The foundation is almost always the main responsible for localized fractures on the surface of the stone paving, it is therefore advisable to adequately compact the underlying layer before performing the casting operation, avoiding as far as possible successive casting operations and respecting its drying and settling period (28 days) before starting the installation of the stone elements.
Useful installation thickness
The construction of a foundation must necessarily take into consideration an adequate useful thickness for the installation of Natural Stone.
Paving in cubes and in pebbles require:
- a useful thickness for installation equal to 10 cm for the 4/6 cm type
- a useful thickness for installation equal to 12 cm for the 6/8 cm type
- a useful thickness for installation equal to 14 cm for the 8/10 cm type
Square slab or opus incertum paving need:
- a useful thickness for installation equal to 6 cm for stones with thickness between 1 and 3 cm
- a useful thickness for installation equal to 8 cm for stones with thickness between 3 and 5 cm
- a useful thickness for installation equal to 10 cm for stones with thickness between 5 and 7 cm