Decarbonizing roads with mycelium: studying interactions with road materials

Road materials are essential for the construction and maintenance of transportation infrastructure. Granular materials—whether fine or coarse, natural or synthetic—form the base of all road components. Depending on their properties and intended use, they can be used as-is (Unbound Granular Materials, UGM) or treated (Bound Granular Materials, BGM) with hydraulic binders like cement or hydrocarbon binders like bitumen. However, these materials have a significant environmental impact. Indeed, the production, transport, and implementation of these products, whether treated or not, generate substantial greenhouse gas emissions and consume large amounts of energy and natural resources [1-3]. Furthermore, their degradation over time can release harmful substances into the surrounding natural environments [4]. It is therefore necessary to evolve these materials to minimize their environmental footprint while ensuring the durability and safety of infrastructure.

In nature, it has been demonstrated that filamentous fungi possess considerable potential for improving erosion resistance and the strength of natural soils. This stabilization is made possible through the formation of mycelium—a three-dimensional network of hyphae responsible for nutrient absorption—and the secretion of extracellular polymers into the soil. Longer hyphae increase soil aggregation and improve stability. Additionally, it has been observed that incorporating fungi into the soil significantly reduces its permeability [5].

These properties could be advantageously used to enhance the environmental performance of road materials. Regarding UGM, one could consider the valorization of in-situ soils as an alternative to quarry materials, thereby protecting natural resources and reducing the nuisances resulting from aggregate transport. For BGM, a reduction in the percentage of hydraulic or hydrocarbon binders used could be envisioned, leading to a reduced environmental impact.

The objective of this thesis will be to determine whether filamentous fungi can be beneficial in the preparation of road materials. Drawing on the biochemical characterization tools of the CPDM laboratory and the mechanical tests available at the MIT laboratory, we will seek to answer the following questions:

What are the surface exchanges between the mycelium and road materials?

For UGM, we will specifically study the mycelium's ability to adhere to mineral particles and develop within the material's interstices. This interaction will depend on several factors such as grain size, mineralogical nature, porosity, and water content. The goal will be to understand how these parameters influence mycelium growth and its ability to form a cohesive network that can modify the mechanical or environmental properties of the road material.

For BGM with hydraulic binders, it is already known that mycelium development within a cementitious matrix can promote the creation of micro-channels. It is also known that certain fungal species are capable of precipitating calcium carbonate during their growth [6,7]. Collectively, these properties could help promote the development of cementitious phases in the early stages of the material and contribute to a self-healing phenomenon for cracks.

How does the presence of mycelium influence performance?

For UGM, particular attention will be paid to the influence of density during specimen preparation. Ideally, mycelium treatment should allow for lower densification levels while achieving equivalent mechanical (shear strength) and hydraulic (permeability) performance.

For BGM, the primary focus will be on the amount of binder. Ideally, mycelium treatment should allow for a reduction in the quantities of hydraulic or hydrocarbon binders while maintaining equivalent mechanical (compressive strength) and hydraulic (permeability) performance levels. Secondary focus may also be placed on density.

How does the presence of mycelium influence durability?

While an improvement in intergranular cohesion is expected in the short term with mycelium development, undesirable phenomena could appear in the long term. Certain fungal species have shown an ability to colonize hydrocarbon-rich surfaces through the production of specific enzymes, such as laccases and peroxidases, which are capable of partially degrading the complex organic compounds in bituminous binders [8]. If confirmed, this phenomenon could be advantageously exploited to accelerate the biodegradation of asphalt mixes at the end of their life cycle, thereby promoting recycling.

Refrences

[1] Vijerathne, D.; Wahala, S.; Illankoon, C. Impact of Crushed Natural Aggregate on Environmental Footprint of the Construction Industry: Enhancing Sustainability in Aggregate Production. Buildings 2024, 14, 2770. https://doi.org/10.3390/buildings14092770
[2] Andrew, R. M.: Global CO2 emissions from cement production, Earth Syst. Sci. Data 2018, 10, 195–217. https://doi.org/10.5194/essd-10-195-2018
[3] Perri, G.; De Rose, M.; Domitrović, J.; Vaiana, R. CO2 Impact Analysis for Road Embankment Construction: Comparison of Lignin and Lime Soil Stabilization Treatments. Sustainability 2023, 15, 1912. https://doi.org/10.3390/su15031912
[4] Jandová, V., Bucková, M., Huzlík, J. et al. Release of PAHs from reclaimed asphalt mixtures into the water environment after passivation by cold in-place recycling technology. Environ Sci Pollut Res 2025, 32, 2455–2466. https://doi.org/10.1007/s11356-024-35875-2
[5] Gou, L., Zhang, X., Gao, H.et al. Fungus-induced sand stabilization: Strength and erosion resistance properties, Eng Geol 2025, 354, 108156,ISSN 0013-7952. https://doi.org/10.1016/j.enggeo.2025.108156
[6] Khushnood, R.A., Ali, A.M., Bhatti, M.F. et al. Self-healing fungi concrete using potential strains Rhizopus oryzae and Trichoderma longibrachiatum, J Build Eng 2022, 50, 104155. https://doi.org/10.1016/j.jobe.2022.104155.
[7] Zhang, X., Fan, X., Li, M. et al. Study on the behaviors of fungi-concrete surface interactions and theoretical assessment of its potentials for durable concrete with fungal-mediated self-healing, J Clean Prod 2021, 292, 125870. https://doi.org/10.1016/j.jclepro.2021.125870.
[8] Torres-Farradá, G.; Thijs, S.; Rineau, F.; Guerra, G.; Vangronsveld, J. White Rot Fungi as Tools for the Bioremediation of Xenobiotics: A Review. J. Fungi 2024, 10, 167. https://doi.org/10.3390/jof10030167

Gustave Eiffel University is a national public multidisciplinary institution for higher education and research. Its primary missions are education (initial and continuing), research and innovation, support for public policies, and community outreach.

It has several sites across the country, including the Nantes campus located in the town of Bouguenais.

The PhD will be carried out within the CPDM (https://cpdm.univ-gustave-eiffel.fr/) and MIT (https://mit.univ-gustave-eiffel.fr/en/) laboratories of Université Gustave Eiffel (Nantes campus), with supervision covering all the issues addressed in the thesis. The MIT laboratory focuses on the characterization of road materials and the
development of innovative materials to improve the durability and resilience of road infrastructures and to reduce their carbon footprint. The activities of the CPDM laboratory focuse on the chemistry and physicochemistry of construction materials.

We are seeking outstanding and motivated candidates with a Master’s degree in relevant biological or materials science disciplines. The candidate should demonstrate motivation, scientific curiosity, and a strong interest in  laboratory testing. A strong command of the English language (written and spoken) is required.