Installation Guidelines
A. FOUNDATION
The foundation is the firm strata that bears the load of the
paving. It is required to maintain its physical and mechanical
characteristics unaltered, and must be non-compressible. From
a functional viewpoint, its structure is aimed at creating
slope and, in the case of outdoor paving, for the draining of
surface water.
The choice of type of foundation is made in function of the
existing terrain and of the load to be borne by the pavement.
Two main types of foundation exist: ballast and the concrete
slab.
Ballast is a layer of compacted gravel at least 30cm thick,
consisting of chunks of larger size in contact with the ground
and smaller grain above to obtain effective surface compactness.
Concrete slab instead consists of a 10 to 15 cm thick layer of
concrete mixed at 250kg of cement per m3 of suitably graded insert
material, slightly reinforced against shrinkage.
B. SETTING BED
This is the actual paving bed, placed on top of the foundation.
It can vary according to whether the pavement is indoor or
outdoor.
Outdoor: The best bedding system in terms of quality consists
of crushed stone gravel (split type) 3-5mm, polyhedral in shape,
washed and sorted. This type of sand not only provides the
pavement with great stability after compacting, but also drains
water both during and after pavement setting.
As an alternative, another kind of bedding consists of 0-6mm
cleaned and soil-free coarse sand. The sand used for the bedding
layer can be mixed with dry cement added in the ratio of 150kg
per m3 of sand in order to prevent sinking. When setting binders
and cubes, a bedding of sand and cement is recommended.
Indoor: The bedding layer should consist of dry-mixed sand
and cement in the ratio of 400kg of cement per cubic meter of
sand. Considering that the thickness of the sand bed will
decrease by about 2cm because of installation operations, its
initial thickness should range from 6 to 8cm according to the
height of the building element. During the design phase, it will
always be necessary to remember that the finished pavement will
consist of the thickness of the product plus 4-5cm of pressed
sand.
C. COMPACTING
Once setting of stones is completed, special large brushes are used
to clean the surface. The spaces between elements are then filled
with sand or a mixture of sand and cement. At this point, compacting
is performed to press every single piece into final position in the
bedding layer and therefore obtain a perfectly even surface. The
pavement should receive at least two compacting treatments in two
directions.
When sand alone is used for setting, the surface is drenched with
water following the first round of compacting and before starting
the second one. When sand and cement is used, the quantity of water
used is less prior to the second compacting phase. After compacting,
the pavement is carefully rinsed in order to remove any surplus
cement.
D. GROUTING
The last phase is joint grouting between the stones. If possible,
this is done with a binding material. Among the various sealing
systems the most commonly used are sand and cement slurry.
1) Grouting using sand is done by distributing over the paving,
after compacting, a layer or fine sand, 0-4mm, by filling in all
of the joints using a large brush. The sand must be left on the
paving for at least 15 days so as to ensure complete packing of
the joints, after which the surplus sand can be removed. This
technique allows for the complete recovery of the stone in the
case of paving removal for excavation works, but requires greater
maintenance because sand is easily removed by the streaming surface
water.
2) In the case of joint sealing using cement slurry, first of all
it is necessary to verify that, during compacting, the depth of the
joints between one element and the next has increased by 1.5-2cm.
Then the slurry, obtained by mixing equal parts of fine sand (0-4mm),
water and cement, is applied and pushed into every joint using
rubber squeegees. As soon as the mortar starts to set, the surface
is cleaned by removing excess mortar with large brushes aided by
a flow of water.
To prevent cement from depositing on the surface of the porphyry,
it is possible to apply a non-stick product using special rollers,
so that the cement will remain only in the joints. Any remaining
cement residue can be removed by covering the surface with wet
sawdust that is then collected and removed. Any cement haloes can
be removed using sulphuric acid mixed with water or other acid
products commonly found on the market.
