The process of laying small cubes in floorings is composed of four phases : foundation, bed setting, compacting and grouting.

Foundation

The foundation is the most resistant part, on which the pavement lays, therefore it must keep its physical and mechanical features unchanged in the years. From a functional point of view its conformation allows the constitution of slopes which enable the outpouring of rain water, in case the pavement is outdoor.

The choice of the foundation type depends therefore on the soil and on the load the pavement will have to undertake. The most frequently used typologies are ballast and concrete pier.

The ballast is a bringing back of 30cm thick compact gravel, consisting of bigger gravel in contact with the soil and completed in the higher level by finer gravel in order to obtain a good superficial obstruction.

The concrete pier consists of a 10-15cm cemented conglomerate layer with appropriate gravel thickness slightly reinforced for shrinkage.

Sometimes these two foundation typologies can be matched together and their thickness will vary according to the needs.

Bed setting

It is the pavement’s bed, lying on the foundation and it can be of different types, being the pavement internal or external.

For external pavements the bed setting system, of a higher quality, consists of 3-6mm diameter washed and selected pulverized stone grain (split), with a polyhedral shape. This kind of sand, other than giving balance to the pavement after compacting, enables a draining effect in presence of water both during and after the laying.

As an alternative to this sort of pulverized stone, it is possible to use sand of 0-6mm diameter, clean and free from earthy elements. The sand used for bed layer can be dry-mixed with cement (150 kg per m3 of sand) in order to avoid shrinkage.

For internal pavements, especially for cubes to be polished during setting, the bed layer must consist of a mixture of sand and cement dry-mixed (400kg of cement per m3 of sand). Considering the fact that the thickness of the sand layer will suffer a decrease of about 2 cm, due to the effect of the laying operations (bathing and compacting), its thickness will be between 6 and 8 cm depending on the height of the construction element. In the table below you will find the optimal values of thickness after compacting, depending on cubes’ size.

During the project phase, it shall be considered that at the end of the process the pavement will consist of 4-5cm of compressed sand in addition to the thickness of the product used.

Compacting

Once the laying operations are completed, the surface will be cleaned with special brushes and all the gaps between the elements will be filled up with sand (possibly chalky) or with a mixture of sand and cement. It is then possible to go ahead with the compacting process, in order to compress all the single pieces in the setting bed until their final position and a perfect layer’s levelling is reached. This process phase is manually made by using a particular iron pestle or through vibrating flagstones.

Pavement will have to undertake at least two compacting phases, in perpendicular directions, after a controlled water jet in order to make the bed setting easier to tamp and to help the final pavement settlement.

In laying made only with sand, the surface is profusely watered after the first compacting phase and before the second one. In mixed laying (sand and cement), it is necessary to limit water quantity to continue with the second compacting phase. At the end of the process the pavement must be accurately cleaned up by removing cement residues. During this phase it is still possible to adjust possible flaws and replace broken or deteriorated pieces.

Grouting

The last working stage is represented by the grouting of elements joints, which is made using bending material, in certain cases even waterproof, to avoid damages due to water infiltration (frost, sand removal).

Among the different grouting methods, the most common are: with sand, with cement slurry, with slurry mixed to indoor glue.

Grouting using sand is obtained by scattering on the pavement - after the compacting process - fine sand 0-4 mm diameter, possibly chalky, trying to fill up all the gaps with brushes. Sand will have to lay down for at least fifteen days in order to enable the complete obstruction of escapes. After that, it will be possible to remove sand residues. This technique allows a complete recover of the utilised product in case of pavement removal for digging works, but it requests more care during maintenance works because simple sand can be removed by the effect of streaming waters.

For grouting using cement slurry, first of all it is necessary to verify that during the compacting process the escapes between the elements are at least 1,5-2 cm lower than before. Then it is possible to go ahead with the laying of slurry, obtained by mixing in equal parts fine sand (0-3 mm diameter), water and cement. Every escape must be completely tamped by using rubber brushes. As soon as the cement’s setting begins, the surface must be cleaned up, by removing with brushes all slurry residues, using water jets if needed.

To prevent cement from deposing on the porphyry surface, it is possible to lay down an anti-clinging product through apposite rollers. So doing, the cement sticks only onto the escapes. Possible cement residues can be removed by scattering the surface with fine-grained wet sawdust that will be picked up afterwards. Possible cement halos can be removed using sulphuric acid mixed with water or other products that can be easily found on sale.

Grouting of small cubes laid for inner use, to be polished during the laying process, is performed with a slurry composed by a part of quartz sand, 5 parts of cement and water and adding glue Vinavil type in the following quantities: 6 Kg glue every 100 Kg cement in summer and 3-4 Kg glue for the same weight of cement in winter. After checking that all escapes after compacting are lower of at least 2 cm, so that they can contain a good quantity of slurry, cover the pavement with the above-descripted mix, accurately filling in all interstices.

After slurry has performed its shrinkage the pavement must not be cleaned with water. It is enough to scrap only the upper layer of the slurry and to let the pavement dry as slow as possible for at least 15-20 days before starting the polishing operations.

If the slurry dries too rapidly during the first days, it is necessary to keep the surface wet spraying water 2-3 times a day in order to avoid the formation of small rifts between the joints. During the first phase of polishing (roughing) the slurry will be removed by surface polishing machines until the stone comes to light.