Thursday, 25th february 2021 | Technical information
Marco Arezio - Consulente materie plastiche - Sustainable Road Paving with Recycled PVC Blocks

Road pavements are a flexible construction system made up of different load-bearing, draining and finishing elements, which make up the vehicular and parking system for circulating vehicles.

Depending on the geographical position of the roads, the prevailing meteorology and the construction habit, three construction systems are mainly used that can perform the task of accommodating the traffic of heavy and light vehicles:

• Asphalt pavements

• Concrete floors

• Solid wood flooring

Of the three constituent elements, the asphalt one, from the point of view of the kilometers of roads built, is certainly the most used in the world, probably due to its ease of laying, even if the maintenance of a covering with bitumen presents many critical issues due to the temperatures, the salt to melt the ice and the abrasion of the final mat.

The concrete flooring, which is also simple to lay, involves the creation of regular expansion joints, their maintenance, and greater noise in the rolling of the wheel compared to asphalt, the problems of durability in the cycles of freezing and thawing imposed by the climate and by the laying of salt to avoid the formation of ice. Furthermore, the stiffness of the road covering is in contrast with the elasticity of the underlying supporting structure.

The self-locking concrete block is a construction system that can have numerous advantages compared to the previous two, in particular it is possible to create an elastic flooring, durable to direct abrasion of vehicular traffic, draining as water percolation is possible between the joints, easy to maintain.

Although it has a number of advantages, there are also some negative characteristics to consider, such as greater noise compared to asphalt roofing, a higher installation cost and a poor resistance to salt in winter.

From the point of view of sustainability, the two construction systems in which concrete is used are certainly not among the best flooring solutions, in view of a circular economy, while that characterized with asphalt could be included in those sustainable structures, if compounds were used in which they include the waste of recycled tires and the waste of previously milled road surfaces.

There is also another sustainable flooring solution, consisting of self-locking blocks in recycled PVC, consisting of the waste of the sheaths of electrical cables, which allows to respond to many problems expressed by the three floors mentioned above. Let's see the advantages:

• Maintaining a roadway or elastic parking

• Allows water drainage

• Easy to lay as it has an interlocking shape

• It does not have problems with the durability of the element given by road salt

• During maintenance we only intervene on individual pieces

• Greater dynamic range compared to a self-locking concrete and longer life

• Ecological as it is made 100% with waste coming from cable recycling

• Creates an electrically insulated surface as PVC is an insulating material

• Resistant to oils and acids

• It washes and degreases easily with jets of water and detergent

• Non-slip and can be colored with acrylic paints for plastics

• Suitable for heavy traffic

As we have seen, the self-locking block in recycled PVC is suitable for both parking areas, even in the presence of heavy vehicles, that on the roads where it can be seen how the element made of PVC solves, especially in areas with cold climates, the age-old problem of the durability of road surfaces when the salt must be spread.

Furthermore, being made with recycled material and, being able to be recyclable when it was decided to replace the structure, the road construction intervention can be considered as sustainable in area of the circular economy.

The solid recycled PVC enjoys a series of product certifications listed below:

• Abrasion resistance

• Flexural strength

• Compressive strength with reduction of thickness

• Penetration value of the artefact at different times

• Slipperiness with BCRA method

• Dimensional stability

• Remaining footprint

• Apparent thermal conductivity

• Electrical resistance: surface insulation

• Electrical resistance: insulation through the thickness of the material

• Resistance to cigarette burn

• Reaction to fire

• Eluate analysis

Installation of self-locking blocks in recycled PVC

The operation of element flooring is based on the concept of "meshing" which we can define as the impossibility of movement of an element with respect to the adjacent ones, the goal to be achieved with the design of the block itself and the installation is therefore the hindrance of the laid solid wood to perform three movements: vertical, horizontal and rotational.

Vertical meshing is achieved by transferring the shear load to the surrounding blocks through the sand in the connecting joints. The rotational locking is delegated to the thickness while the locking with respect to the horizontal forces takes place through the correct use of assembly schemes, which disperse the forces due to the braking and acceleration of the vehicles and the tangential forces of the tires when cornering.

As regards the laying, we begin with the compaction of the sub-base soil by means of suitable means, particular attention must be paid in the areas adjacent to the edges, wells, drains in the filling areas of the excavations of pipes and systems.

If the minimum guaranteed in the design phase is not respected, the soil must be replaced with more suitable materials.

The slope of the laying surface must be verified, since it must be considered that it is not possible to derive the slopes from the base layers or from the bedding one.

To facilitate the flow of water and avoid premature subsidence of the pavement, they must never be built with a slope of less than 1.5%.

It is advisable to use suitable geosynthetics during the laying of the flooring, these perform the function of separation between the layers and distribution of loads.

The bedding layer must maintain a constant thickness considering a reduction in thickness between 20% and 30% in the settling phase, also due to compaction, depending on the particle size used.

Scoring can be done in two ways:

• Pre-compaction

• Classic method

The first is carried out in several steps: after having spread the sand with a suitable thickness, it is vibrocompacted with a vibrating plate, a new thickness of about 1.5cm is spread and leveled.

With this method it is possible to guarantee lower settlements in pavements that have to bear high loads, moreover it is possible in this way to better control the final settlement of the pavement.

In the classic method The sand is spread and leveled, the compaction takes place in the next phase after installing the screeds using suitable equipment.

It is important not to disturb the laying surface after smoothing, if this is damaged even in small portions it is necessary to arrange it before finishing with the blocks, it is also important never to perform these operations in case of temperatures below 1 ° C to avoid the formation of ice.

At this point, the recycled PVC blocks can be laid, making the edge of one element coincide with another, without leaving room for sand joints.

At the end of this operation, a vibrated rolling of putto will be carried out on the laid floor and a painting of the preferred color can be pre-arranged through the use of specific acrylic paints for plastic.

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Automatic translation. We apologize for any inaccuracies. Original article in Italian.

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