Sustainable asphalt mixtures by partial replacement of fine aggregates with low-grade magnesium carbonate by-product

The utilisation of large quantities of raw materials for asphalt mixtures manufacturing, such as aggregates, is an environmental issue that must be addressed. This concern has led to valorising waste and by-products as more sustainable alternative raw materials. This research is aimed at evaluating the use of a low-grade magnesium carbonate (LG-MC) by-product as a partial replacement of fine aggregates and as a filler of asphalt mixtures. A mechanical analysis has been performed studying the effect of this by-product on the moisture sensitivity, cracking resistance and cohesion loss resistance of asphalt mixtures. Cracking resistance was assessed under different temperatures (20, 5 and -5 ºC) and conditions (unconditioned and aged). Results indicated that moisture sensitivity and cohesion loss resistance of asphalt mixtures with LG-MC by-product were not affected, obtaining similar results to those of the reference mixture. A protective effect in the mixture cracking resistance was observed using LG-MC. At low temperatures or after ageing, this by-product tends to maintain ductility to a greater extent. The study indicates that LG-MC is suitable as a partial substitute for the fine fraction of aggregates, as well as for the total amount of filler in asphalt mixtures manufacturing for road pavements. The authors would like to thank the Catalan Government for the quality accreditation given to their research group DIOPMA (2017 SGR 118). DIOPMA is a certified agent TECNIO in the category of technology developers from the Government of Catalonia. The authors are grateful to the company Magnesitas Navarras, S.A. for supplying the low-grade magnesium carbonate by-product. Mr. Jofre Mañosa is grateful to the Catalan Government for his research Grant, FI-DGR 2020.