The search for more sustainable and environmentally friendly asphalt mixtures is a global priority.

Emulcell project, driven by CETIM and led by Misturas, successfully develops a stretch of cold pavement additive with nanocellulose.

Due to the growing concern about global warming and climate change, one of the most important challenges we face today is the efficient and economical use of energy, as well as the need to reduce greenhouse gases. This concern has also reached the asphalt mix sector, where research is being carried out into the innovation and development of new road materials that are more environmentally friendly.

Bituminous asphalt mixes or asphalt agglomerates have clear advantages for road pavements since, thanks to their slip resistance and ease of laying, they provide surface evenness and road safety. However, their manufacture has a major environmental impact, as they are made using petroleum derivatives (bitumen). Specifically, more than 11 billion tonnes of bitumen are produced in Europe each year, which generates high pollutant emissions.

In order to reduce these figures, the search for more sustainable formulas with equal technical performance is therefore a priority for both private companies and public administrations. One example of this is sustainable roads (green roads or bio-asphalts), built with less polluting asphalt mixes, thanks to the incorporation of recycled materials or bio-based materials as substitutes for fossil-based raw materials.

Recycled materials for circular asphalts
The reuse of by-products in asphalts not only avoids the accumulation of waste in landfills, but also produces more sustainable asphalts with lower environmental impact and better properties.

In addition to the already consolidated reuse of deteriorated pavements in new asphalt mixes, waste of different origins, mainly industrial, is being adapted for use as physical fillers. This makes it possible to significantly reduce the quantities of virgin raw materials required for the manufacture of asphalts.

These by-products must meet the strength and durability needs of our roads, in many cases providing better mechanical properties for bituminous mixes.

There are already successful cases with years of history, in terms of its application, and they offer proven and contrasted results. In Spain, end-of-life tyre dust is present on more than 1,600 kilometers of asphalt roads in both urban and interurban areas. It is the most established circular solution, leading the way to solutions based on other materials.

Bio-based materials for sustainable pavements
Currently, one of the disruptive lines of research in the civil works sector is the search for renewable binders. In road pavements, the aim is to replace bitumen in asphalt mixes with materials of natural origin. An example of this is the use of derivatives of plant compounds as additives for asphalt mixes, such as lignin or nanocellulose.

In this way, natural and renewable materials are used in the manufacture of roads, replacing chemical compounds and materials of fossil origin, which have a larger environmental footprint and are also non-renewable.

Success story – Emulcell bioasphalt
In line with this trend, Emulcell was born, a project in which CETIM Technological Centre and the company Misturas, together with the Roads, Geotechnics and Materials Group (GCGM) of the University of A Coruña (UDC), developed a cold bituminous mixture as an alternative to conventional asphalt.

This material, a type of gravel-emulsion in which the asphalt agglomerate is added with nanocellulose, improves performance compared to conventional mixes. It also minimizes the environmental impacts associated with the production of this type of construction material by partially replacing the petroleum-derived bitumen content with natural products. It also encourages the use of cold mixes, which already have lower greenhouse gas emissions and are easier and safer for operators to lay.

The result of this research has been tested on a real scale in a test-prototype section in Allariz (Ourense). In addition, this project has won the I Galician Innovative Materials Competition, and a sample of the new product developed has been placed in the library of reference materials in Galicia (Materioteca de Galicia).

Thus, in addition to the ecological benefits of using bioasphalts, bioasphalted roads, manufactured with innovative mixtures, improve different functional aspects, such as water resistance, increasing their safety and durability.