Detail of a road surrounded by a forest

Asphalt FAQs

 Do you know what bitumen is? Here we answer questions you have probably asked yourself in a simple and straightforward way.

It is a black-colored binder that can take solid or viscous form at ambient temperature. This viscosity gradually disappears as the temperature decreases. One of its characteristics is that it is insensitive to water and, in addition to its other properties, this makes bitumen a highly suitable binder for use in road construction and waterproofing of surfaces.

The construction of this linear infrastructure, which enables wheeled vehicle traffic in optimum conditions of safety and comfort, is a complex task. Most road surfaces are manufactured from bituminous mixtures formed by a mixture of stones selected according to size and quality (aggregate) and bitumen or asphalt, which is the binder that holds said stones together. At a basic level of construction, a road consists of laying down successive layers of stone materials with different properties and resistances. At construction level, there will be differences depending on whether the road will be in a mountainous area or if terrain must be added (embankments). The greatest enemy of these infrastructures is the extremely heavy load of heavy vehicles and climatic elements. 

The surface or pavement is what is configured by the final road layers, those which are in direct contact with vehicle tires and suffer greater wear over time.

The continuous weathering of the bitumen making up road causes oxidation by UV rays from the sun and contact with the oxygen in the air. This situation makes the surface lose its lightest fractions, stiffening and therefore losing its flexibility and adhesion to the aggregates in the mixture. 

Additionally, the use of materials treated with cement in some surface layers can give rise to retraction, setting, or thermal cracks.

Road characteristics may vary according to the geographical area where cities are located. The different types of road surfaces vary depending on the climatic zone, due to which there are different types of mixtures with different gradings and types of binders. Therefore, the type of mixture used in the surface of a mountain road is not the same as that used in a freeway in hot area.

All three are black, viscous products with a very complex composition that can be grouped under the name hydrocarbon binders. The differences between them can be found in their origin since, while bitumen is a product derived from crude oil, pitches and tars are products derived from coal, and asphalt is a product of natural origin that can be found in a free state or impregnated with porous minerals (asphaltic rocks). 

Now that you know the differences between these products, it is important to highlight that the advantages of oil derivatives make them by far one of the most widely used elements worldwide.

The surface layer of some roads, i.e., the layer directly in contact with wheeled traffic, uses draining bituminous mixtures or discontinuous mixtures. These compositions are designed to have a large number of pores, eliminating or reducing some of the aggregate fractions therein. Rainwater seeps into these spaces in draining mixtures, or filters through them in the case of discontinuous mixtures, thereby preventing water from accumulating on the surface.

Repsol calls the techniques it uses to ensure more environmentally-friendly bitumens use "Green Asphalts." It is not a single product but rather a group of products such as bitumen, made from crumb rubber from scrap tires, bitumens and bituminous emulsions to recycle roads already worn out by use, bituminous binders that allow mixtures to be manufactured at a lower temperature than the one conventionally used. These techniques will allow us to reduce electricity consumption and atmospheric emissions.

As far as we know, the first time asphalts were recycled was in the 1920s. After World War Two their use became more common in the UK, and the same occurred in the US in the 1970s as a result of the oil crisis. In Spain, asphalt recycling became more common in the 1990s, incorporating a range of techniques aimed at achieving the same objective. Recycling is a road rehabilitation technique consisting of reusing materials from road layers that have already been in use: materials that have lost some of their initial properties due to wear and tear or age, but can be used for new road layers. 

At Repsol we have developed REJUV bitumens and emulsions to take full advantage of already degraded materials. They are specific designs that include all the current techniques: on-site cold recycling, or hot, warm, or cold recycling of bituminous mixtures at the manufacturing plant.

The EC Mark for binders is a mandatory requirement for the free sale of binders in the European Union. This responsibility of the manufacturer consists of a series of specifications and tests, in addition to production control requirements. The EC Mark encompasses the entire production process from the receipt of raw materials to the procurement of the final product, including factory operating conditions and laboratory tests, without forgetting the calibrations and maintenance plans for all the equipment involved in both the plant and laboratory. It has been mandatory for bitumen, hard bitumen and cationic bituminous emulsions since January 1, 2011. In the case of modified bitumen, the date was January 1, 2012. The EC mark symbol must comply with the general principles set out in Article 30 of Regulation (EC) No. 305/2011 and should be placed in a visible, legible and indelible place: 

  • Identification number of the certifying body 
  • Name and address of the manufacturer, clearly marked and legible 
  • The last two digits of the year in which the EC Mark was first placed 
  • Unique identification code for the product type 
  • Reference number of the Declaration of Performance 
  • Level or kind of declared performances 
  • The dated reference to the applicable harmonized technical specification 
  • Expected use as established in the applied harmonized technical specification 

The manufacturer will issue a declaration of performance for each product, assuming responsibility for the compliance of the product built with the declared characteristics.