What is bitumen? Types, properties, and applications

Bitumen is a product of crude oil distillation in a refinery. It is the heaviest and densest fraction that remains at the end of the distillation processes, following extraction of the lightest fractions such as gasoline, diesel, and kerosene. The typical ratio in a bituminous mixture is approximately 5% bitumen as opposed to 95% aggregates: a tiny percentage that belies an enormous responsibility in technical terms. 

Asphalt — or more precisely, bituminous mixtures — is the combination of bitumen and aggregates that construction companies manufacture and spread to form the road surface. Bitumen is just one of its vital components: this hydrocarbon binder that binds the aggregates gives them cohesion and allows the mixture to withstand the ongoing passage of traffic. Without bitumen, the asphalt would disintegrate. 

In Spain, we produce bitumen at our refineries located in A Coruña, Bilbao (Petronor), Cartagena, and Puertollano, as well as at the Asesa refinery, a 50% joint venture with Moeve that is located in the Tarragona Petrochemical Complex. We also produce it at the La Pampilla refinery, located in Peru. At each facility, careful selection of the crude oil reference basket ensures compliance with national and international specifications

In everyday language, "asphalt" and "bitumen" are often used synonymously, although they are not the same thing. 

• Bitumen, also called asphalt bitumen or bitumen, is the pure hydrocarbon binder: the black and viscous material obtained from the refining of petroleum. 
• Asphalt or bituminous mixture is the final product that is spread on the roads: a combination of bitumen (5%) and stone aggregates (95%). 

Like we've said, there's a huge technical responsibility behind this small percentage: the bitumen gives cohesion to the whole, waterproofs the mixture, and allows it to withstand the continuous passage of traffic.

All the polymer-modified bitumens that we sell meet CE marking requirements as required by the UNE EN 14023 standard.

The main challenge of conventional bitumen is temperature: it requires heat to be handled, which consumes energy throughout the chain, from transport to commissioning. 

It is important to understand what emulsion is: it is the means to make bitumen manageable without heat. The product that ultimately ends up on the road, once the emulsion has broken, is the bitumen itself.

Our ADVANCE and EFI-ADVANCE ranges cover a wide range of applications: primer sprays, adhesion sprays, curing sprays, cold microagglomerates, open grain blends, and surface treatments. 

An essential function, often less known, is the adhesion between the different layers that make up the surface. The EFI-ADVANCE TER range includes thermo-adherent emulsions designed specifically to guarantee that bond: they are not eliminated with the passage of work traffic and activate their adhesiveness when the hot mixture is extended, optimizing the behavior of the road surface in the long term. 

We have also developed specific emulsions for the recycling of aged pavements. The EFI-ADVANCE REC REJUV range incorporates rejuvenating agents that recover the properties of the original bitumen, allowing 100% of the road's aged material to be reused to make a new mixture without the need for new aggregate. 

Within in this range, we find specific products for specific needs: 

• Bitumens subjected to extreme stress: For stretches where heavy traffic is constant — truck lanes, bus stops, toll areas — there are formulations that increase the resistance of the pavement to deformation and extend its useful life. 
• Bitumens for improved adhesion: There are aggregates that do not adhere well to conventional bitumen. Activated bitumens (ACTIV) contain adhesion promoters which reinforce that chemical bond and prevent the mixture from losing cohesion. 
• Bitumens to rejuvenate aged binders: When a road reaches the end of its useful life, all that material shouldn't go to waste. Rejuvenating bitumens (REJUV) recover the properties of aged binders and allow the milled material itself to be added to the new mixture, thus reducing the consumption of new aggregate. 
• Bitumens to reduce manufacturing temperatures: Manufacturing asphalt requires temperatures above 160 °C. Low-temperature bitumens (ECOBET range) reduce that threshold between 20 and 40 degrees, which allows working at lower temperatures and improves on-site working conditions.
• Bitumen for demanding traffic: The tarmac at airports must support aircraft of hundreds of tons under extreme temperature gradients. High-modulus bitumens are formulated for that specific structural requirement. 
• Bitumens resistant to the action of organic compounds: In service stations, hangars, or fleet loading areas, frequent contact with fuel degrades conventional bitumen. Fuel-resistant bitumens maintain mixture cohesion despite this contact.

Synthetic binders are products with properties similar to bitumen, but which do not come from direct petroleum distillation. Instead, they are manufactured from blends of resins, oils, and polymers. Their differential feature is that they are colorless in thin film and can be pigmented in any shade. 

In practice, this means that the pavement can adopt the color of local aggregates or added pigments. Examples of these applications include separate bike lanes, pedestrian areas, splitter islands, and functional signage. Infrastructures integrate into the environment or communicate functions with visual clarity without the need for additional painting. 

There is also a relevant functional effect: black pavement absorbs solar radiation and increases the surface temperature. A lighter-toned binder reflects some of that radiation, helping to mitigate the heat island effect in urban environments. This is especially applicable in tunnels, where light pavements improve luminosity and reduce electricity consumption in lighting. 

Our range of RECOFAL binder bitumens is available in bulk, in drums, and in pellet format. RECOFAL S100 P COLOR, sold as pellets, is added directly to the mixer, which facilitates its use in small-volume works and its long-distance transport with minimal logistical needs. 

Bitumen isn't just for tires to drive on. It's also found on the building roofs, in the lining of underground infrastructure pipes, on the floors of industrial facilities, and in vehicles. 

Our ISOLATE bitumen line is made up of bitumens specifically formulated for non-road applications: 

• Waterproofing sheets in combination with polymers. 
• Waterproofing systems for roofs and façades. 
• Piping lining, joint sealing, and industrial paving mortars. 
• Acoustic sheets for the automotive sector. 
• Other applications: hydraulic works, dune stabilization, crop protection, and special adhesives. 

The same technology that defines the durability of a road also protects the roof of a building, the interior of a pipe, or the floor of an industrial building. Bitumen, in its different formulations, is a building material with a wide range of applications. 

Pavement durability has a direct impact on resource consumption and emission reductions across the entire infrastructure life cycle. The longer a road lasts, the less new material is needed and the fewer milling and resurfacing operations are performed. 

In this sense, bitumen can contribute to improving efficiency in the use of resources and reducing the environmental impact associated with the construction and maintenance of roads through different solutions:

• Recycling pavements with rejuvenating bitumens makes it possible to recover milled material, reducing the need for new aggregate and the transport of materials. 
• Low-temperature bitumens (ECOBET) reduce the manufacturing temperature of the mixtures between 20 and 40 °C, with the consequent saving of energy and reduction of emissions in the plant and on-site. 
• Bituminous emulsions eliminate the need for heat in multiple applications, significantly reducing energy consumption. One of these applications is on-site cold recycling with emulsion, which allows the reuse of 100% of the road's aged milled material.

Repsol has Environmental Product Declarations (EPDs) for conventional bitumens, polymer-modified bitumens, bitumens with rubber powder from end-of-life tires, and bituminous emulsions. EDPs allow the quantification and reporting of the environmental impacts of bituminous binders based on the life cycle analysis study.

The reason is that we understand that improving firm durability has a direct impact on resource consumption and emissions reductions across the entire infrastructure life cycle. 

Behind each type of bituminous binder is a research process that goes far beyond refinery production and manufacturing plants for emulsions and modified bitumens. 

Repsol Technology Lab is the center where bituminous binders are developed and researched, a national and international benchmark in the sector. The asphalt laboratory has the necessary equipment to characterize conventional bitumens, modified bitumens, emulsions, synthetic binders, and bituminous mixtures in real service conditions. 

The ability to formulate specific products for each work is one of the pillars of the laboratory. A concrete example is the design of a bitumen for use at low temperature and with the incorporation of rejuvenating additives for a road rehabilitation project with 30% milled material incorporated into the mixture. The binder has been custom-developed in such a way that the rejuvenating additive has made it possible to restore the chemical composition of the aged bitumen. No less, doing this with low-temperature additives has made it possible to manufacture the mixture at 140 °C, 20 °C less than a conventional mixture. Chemical tests of the end-product bitumen confirmed that the composition recovered to levels equivalent to that of a fresh bitumen, with less aging during the mixture's manufacturing process due to the lower working temperature and greater durability of the material put on site. 

In addition to laboratory work, we offer a Technical Assistance and Development service that covers prior advice, assistance in execution, design of customized products and training. In many special formulations, the design of the product is specific to each job. 

The regularity of a well-preserved highway, the integrity of an airport tarmac, or the durability of an industrial roof respond to the same chain of technical decisions: crude oil selection, laboratory formulation, and adjustment to the conditions of each job. Conventional bitumens, modified polymer bitumens, emulsions, synthetic binders: each variant responds to a specific requirement, a climate, a type of traffic, or a specific infrastructure. Bitumen is there in each link of that chain: that 5% of the mixture that holds it all together.