Why is it convenient to asphalt the streets of summer? How asphalting takes place from a technical point of view

Many of us, during the summer months, will have met road construction sites along the highways. Often these construction sites are put in place to carry out road maintenance activities, in particular for Spread the asphalt. The asphalt, whose technical name is Bituminous conglomerateis a material used to pave roads, highways and squares. Is mainly composed of bitumen, A viscose substance derived from oil, which is mixed with sand, gravel and stone.

This mix is heated at high temperatures to become one dense pasta which is easily spread on the road surface, and then compacted with rollers to create a smooth and uniform surface. Once the asphalt cools down, it forms a solid and resistant surface. But why do the roads preferably asphalted in summer? Here is explained the reasons for this technical choice.

How the asphalt is spread

The drafting of the asphalt takes place through several five distinct phases.

1. Preparation of the background and the base

Before spreading the asphalt, it is essential to adequately prepare the surface below. This includes:

• Demolition and removal (if present): If there is an old damaged pavement, it is removed through road milling machines (which “screw” the existing asphalt layer) or pneumatic hammers for concrete. The removed material can often be recycled.
• Ground leveling: The surface is leveled with machines such as motalivellatrics to ensure adequate slope for water drainage. A good drainage is crucial to prevent future damage such as holes and cracks.
• Compaction of the background: The ground is compacted with compressors (crushing) rollers to create a stable and uniform base.
• Drafting and compaction of the basic layer: A layer of granular materials is laid (such as Pietrisco, Ghiaia or sand) or, in some cases, a “bituminated mixed” (aggregates tied with bitumen) that acts as a load -bearing base. This layer is also accurately compacted .ù

2. Spray of bituminous emulsion (attacking hand)

Before drafting the real asphalt layer, a thin layer of bituminous emulsion (called “attack hand”). This acts as a sticker, ensuring a strong link between the new layer of asphalt and the one below (whether it is the granular base or an old layer of asphalt). It is sprayed by a tank truck equipped with splashing bar.

3. Drafting of the bituminous conglomerate (asphalt)

This is the central phase of asphalting and usually takes place with the use of a road finishes (or asphalting):

• The first phase is that of loading, in which the hot bituminous conglomerate (produced in specialized systems and transported to the construction site by means of “insulated” trucks to maintain the temperature) is downloaded to the front hopper of the fining.
• We then have the phase of distribution and drafting, in which the road to the road finishes distributes the asphalt uniformly on the desired width. Inside the machine, the cochleans (endless screws) push the material sideways, while a “vibrophical bar” or “spread” (a heated and vibrant plate) level and pre-set the asphalt to the required thickness.

As for the thickness of the layers, We can say that modern roads are usually built with multiple layers of asphalt, each with specific functions:

• Binder layer (or connection): An intermediate layer more often, with larger aggregates, which distributes loads and provides structural robustness.

• Wear layer (or wear carpet): The superficial layer, thinner and with finer aggregates, designed to resist the wear and tear of traffic, to the atmospheric agents and guarantee good grip (weaving).

4. Final compaction

Immediately after the drafting, when the asphalt is still hot and malleable, the compaction phase intervenes, performed with compressors rollers. This step is essential for:

• Increase density: Eliminate the air voids inside the conglomerate, making it more dense and resistant.
• Improve stability: Ensure that asphalt can bear traffic loads without deformations.
• Ensure the planarity: Create a smooth and uniform surface for driving comfort and drainage.
• Promote the adhesion between layers: Ensure that the various layers of asphalt are well glued together.

Compact usually takes place for later passages, starting from the edges and proceeding towards the center of the roadway, often with also diagonal passages to standardize everything.

5. Cooling and traffic opening

Once compacted, the asphalt must cool down to reach its full resistance. This process may take several hours, depending on the ambient temperature and the thickness of the layer. Only after complete cooling, the road is reopened to traffic. In summary, the drafting of the asphalt is an operation that combines mechanical precision, control of temperatures and optimal execution times to create a lasting and safe road surface.

Why is it convenient to asphalt the streets of summer?

The reasons why you choose to asphalt the street streets are technical, on the one hand, and logistics on the other. The highest temperatures, in fact, make the bitumen more easily working, while the summer holiday period involves a minor volume of traffic conveying, making it easier for workers to work on the roads.

Workability and adhesion of the bitumen

First of all there is the problem of bitumen temperature and workability. The asphalt, or rather the bituminous conglomerate, is mainly composed of aggregates (gravel, sand) together with a bituminous binder. Bitumen is a viscoelastic material that increases its fluidity and is therefore more easily working at high temperatures. During the summer, the high temperatures help to maintain bitumen at the optimal vesa temperature (which can vary from 130 to 150 ° C), ensuring better compaction and adhesion to the road substrate. If the bitumen cooled too quickly, it would become more rigid and difficult to spread uniformly, compromising the final quality of the flooring.

We then have greater adherence and compaction of the materials used. The heat, in fact, promotes and makes a better one Adhesion of bitumen to the aggregates and the underlying layer of the road. Good adhesion is essential for the durability of the road surface and for preventing the asphalt enhancement. The high temperatures also allow one better compaction of the material through the use of rollers, reducing the voids and increasing the density and resistance of the asphalt.

Limit humidity

The second technical reason why you prefer asphalting in summer is related to the possibility of avoiding an excessive humidity rate given that the water is an enemy of the asphalt just posed. Excessive humidity can compromise the adhesion of bitumen and the stability of the conglomerate, leading to structural defects. Summer, especially in many regions, is characterized by periods of drought and lower rainfall, reducing the risk of ruining the work just done.

Less traffic

Among the logistical reasons we find, instead, less traffic. In many areas, in fact, summer coincides with the holiday period, which can lead to a minor volume of traffic vehicular, especially in cities. This facilitates work, reducing the inconvenience for citizens and allowing teams to work more efficiently and safely.

More hours of light

Then we have one greater availability of time. The summer days are longer, offering more hours of light to work. This allows you to complete larger projects and to reduce execution times, optimizing resources.