Sustainable consumption of geomaterials and production of asphalt pavements in sensitive environments: low energy asphalt with waste materials from volcanic islands

Abstract

The manufacture of hot mix asphalt (HMA) for paving is one of the most energy-intensive and emission-intensive activities in the construction industry, whose annual global production is estimated at nearly 1.2 billion tonnes. Low-energy asphalt technologies, such as Warm Mix Asphalt (WMA), would allow these fundamental materials for transport infrastructures to be used sustainably in the long term. In asphalt mixtures, aggregates account for around 90% of their mass, which represents an economic and ecological problem, given the impact of extraction and the limited territory in volcanic islands. A significant portion of volcanic rocks is discarded because of the unsuitable mechanical properties for structural materials, due to their extreme porosity. Therefore, the use of residual aggregates is also vital for the sustainability of the construction industry. Furthermore, end-of-life tires (ELT) are also a major environmental problem. However, reclaimed granulated rubber from waste ELT can improve the mechanical performance of asphalt (rubberized asphalt, RA), although increasing the asphalt viscosity. Thus, coupling RA with WMA technologies is crucial. The combination of these three technologies enable cleaner and more sustainable asphalt mixtures for paving and even with increased durability. For this purpose, the main technological properties of these rubberized warm asphalt mixtures (manufactured at different low temperatures by using a chemical surfactant additive composed of renewable components) with waste aggregates are analysed in the laboratory and compared with conventional mixtures. The results show that it is possible to produce these warm asphalt mixtures with rubber and highly porous residual volcanic aggregates in compliance with the specifications for pavements, while improving the performance of certain properties such as the resistance to water action and to plastic deformations. The analysis using eco-efficiency indicators concludes that the energy consumption can be reduced by nearly 25%, reducing emissions by 20% and using waste materials by more than 95% by weight.