Towards a microalgae-based road binder
Résumé
Asphalt is a sticky viscoelastic petroleum industry by-product, used in sealing surface but mostly as aggregates binder in road pavement. For about seven years, the worldwide petroleum production didn’t increase anymore. In that context, refining strategies are changing: for example, high molecular fractions can be cracked into lighter fuel fractions and consequently, in the future, it could be difficult to answer to the worldwide needs in asphalt. To avoid this problem, some biomass-based binders have been developed. They are generally based on a mixture between a vegetable oil, like rapeseed one, a natural or modified vegetable resin and a synthetic polymer in order to adjust the rheological properties. The weak point of those alternative binders is that an edible oil is used. Therefore, it has been decided to investigate the potential of a new promising biomass, microalgae, which doesn’t compete with human feeding. Microalgae are already studied for bioenergy, cosmetics, nutraceuticals or animal feeding. For economic and ecological reasons, the by-products resulting from the microalgae industries have to be valorised. Consequently, we propose to study the potential of using those by-products as binder for aggregates. To achieve this goal, two processes have been studied. In a first time, extraction steps have been performed. Extracts have been characterized from a chemical and a mechanical point of view, and showed an interesting asphalt-like behavior. The comparison of rheological and chemical analyses allows to highlight a relationship between the thermo-dependent behaviour of the extracts and the presence of some specific chemical species. We also took in consideration low energy consumption and environmentally friendly process, performing some thermochemical modifications of the biomass.