Optimization of Mechanical Performance and Sustainability of Asphalt Mixtures through the Incorporation of Recycled Rubber Crumb

Abstract

Road infrastructure is a key indicator of a country's development. Traditionally, hot dense asphalt mixtures (HMA) have been used due to their ability to withstand traffic loads and adverse weather conditions. However, a growing emphasis on sustainability in road construction drives the search for technologies that reduce environmental impact without compromising durability and safety. One solution is the incorporation of recycled rubber crumb (RRC) into asphalt mixtures, reusing tire waste and enhancing performance.

This study evaluates the impact of RRC on HMA through an experimental process developed in four phases. In Phase 1, the materials used (aggregates, asphalt binder, and RRC) were collected and characterized according to INVIAS 2022 specifications. Tests were conducted on the aggregates to assess hardness, durability, cleanliness, and gradation; the asphalt binder was evaluated in terms of viscosity, penetration, and softening point. The RRC was characterized based on particle size distribution, and moisture, and fiber content. In Phase 2, conventional and RRC-modified asphalt mixture briquettes were designed and fabricated with RRC proportions of 1%, 2%, and 3% (dry process), compacted according to current regulations. Phase 3 involved the characterization of the briquettes testing rutting (INV E 756-13), moisture susceptibility (INV E 725-13), the resilient modulus (INV E 749-13), and fatigue resistance. Finally, in Phase 4, a technical and statistical analysis of the results was conducted, comparing the mechanical and functional performance of the mixtures in terms of durability, structural resistance, and behavior under environmental and load-related factors.

The results indicate that the addition of 1% RRC significantly improves fatigue resistance, structural stability, and safety under wet conditions, surpassing the performance of conventional mixtures. The environmental and economic impact assessment demonstrates that the use of RRC not only extends pavement service life but also reduces tire waste and CO₂ emissions associated with virgin asphalt production, contributing to the circular economy and sustainable development.

It is important to recognize some limitations in this study. The tests were carried out under controlled conditions which do not fully replicate the real conditions of the variables already mentioned. The granular material used was obtained from a quarry in the region of Tunja, Boyacá, which limits the applicability compared to material obtained from other regions with different climatic, geotechnical, or traffic characteristics. Other modification techniques besides RRC, which could offer variations in the mechanical and environmental performance of the mixtures, were not evaluated. This research did not directly quantify the environmental impact of the use of RRC through each stage of the life cycle of an asphalt pavement: it does not include an experimental or quantitative environmental evaluation. Finally, the sustainability component was developed through a referential review of updated scientific literature. This study provides scientific and applied evidence for the implementation of more sustainable technologies in road construction, establishing RRC as an effective and environmentally responsible modifier. Its alignment with international standards and its potential to optimize waste management position it as a viable strategy for modernizing flexible pavements on a global scale.