Laying paving stone: laying porphyry tiles in mortar with cement dusting

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This laying paving stone system is used for porphyry tiles of constant thickness. The laying in mortar with cement dusting consists of:

  • Builders sand with grain size of 0-4 mm:it must be very clean (without organic, earthy or clayey substances, or oxides or salts);
  • Water:clean, preferably mains water (without oxides, salts, organic substances and any other substance that can affect the quality of the mortar or cause efflorescence
  • Portland 325 cement:in quantity of 300 kg per cubic metre of sand.

The mixture must be mixed until a semi-dry consistency is obtained, very similar to damp earth, trying to avoid puddles. To increase the workability of the mortar, hydrated lime in the correct quantity may be added.

Then the foundation must be cleaned of any impurities and dust, and it is necessary to wet it thoroughly without causing puddles. Once strips have been arranged for ease of levelling of the surface, the bedding mortar is laid with a thickness of at least 3 cm and not more than 6 cm.

The mortar is then compacted and levelled with an aluminium pole until the bedding layer is uniform. The surface is abundantly sprinkled with cement in order to completely cover the part where the laying is going to be done and the underside of the tile is wetted and laid, tapping it with a rubber hammer, until it is placed in the required position and level.

During all these laying paving stone operations the surface of the tiles must be kept clean from the spattering of the mortar and should not be walked on, or at least only if necessary and then with great care, in order to avoid damaging and dirtying the elements just laid. If possible, it is better not to touch the paving for some days in order to permit the initial, rapid drying of the bedding mortar.

Laying paving stone: laying porphyry tiles in mortar with cement dusting

Next comes the operations of sealing. After having wet the surface, it must be sprinkled with liquid cement “boiacca”, obtained by mixing cement and clean water. The boiacca has to fill all the interstices between one paving stone and another. Large rubber spatulas, angled at 45 degrees to the gaps, must pass more than once over the paving.

Finally it is important to clean the surface using big rubber spatulas, damp sponges and sawdust. If the paving has to be polished, it is better to leave a very thin layer of boiacca on the surface, without forming undulations or rough changes in height.

Usually a surface can be used about a week after this laying paving stone is finished, but with regards to the operations of smoothing and polishing it is best not to begin them until 15 days after the end of the laying.