The road to sustainable pavements: synergistic effect of nanoclay on the performance of crumb rubber-modified asphalt

ORTIZ DE ZÁRATE, FEDERICO I.; ZAPATA FERRERO, IGNACIO; HORMAIZTEGUI, M. E. VICTORIA; BONAZZOLA, MAXIMILIANO; REGENHARDT, SILVINA A.; BOTASSO, H. GERARDO; MEYER, CAMILO I.

Buenos Aires

Congreso; WCCE11 - 11th WORLD CONGRESS OF CHEMICAL ENGINEERING; 2023

Asociación Argentina de Ingenieros Químicos (AAIQ)

The use of crumb rubber recycled from scrap tires as an asphaltmodifier has many benefits, mainly, it improves the rutting and fatigueperformance of pavement, while eliminating environmental and economic problems.Nonetheless, this technology has some limitations, such as the phase separationconcern during storage and transportation, and the deterioration of itsperformance due to environmental aging. In recent years, nanomaterials haveattracted great interest in the pavement research community, as they can beconsidered ideal additives for the development of a new generation of pavingmaterials [1]. Specifically, nanoclay has shown potential as a complementaryadditive in polymer-modified asphalts, addressing its main shortcomings.However, there is still a lack of systematic investigations on the subject. Theobjective of this study is to evaluate the contribution of organo-modifiednanoclay on the rutting, fatigue and anti-aging performance of crumbrubber-modified asphalt.Organo-modified nanoclay (NC) was prepared through cation exchangebetween a natural montmorillonite and benzalkonium chloride. Two kinds ofasphalt (CA20 and CA30) were modified with 20% crumb rubber and 0, 3 and 5% NCusing a high-shear mixer. Rheological properties of the modified asphalts wereassessed by means of temperature and frequency sweeps, Multiple Stress Creepand Recovery (MSCR) and Linear Amplitude Sweep (LAS) tests. Phase separationwas evaluated after a lab-simulated storage process, as per ASTM D7173.Chemical properties were analyzed by Fourier Transform Infrared Spectroscopy(FTIR).As expected, 20%-crumb rubber-modified asphalt (CRMA) showed poorstorage stability. The addition of nanoclay alleviates substantially the phaseseparation problem, reducing the difference in softening point to less than2.5°C, which indicates satisfactory storage stability. Rutting resistance ofCRMA is improved by the addition of nanoclay, according to the results oftemperature sweeps. MSCR tests confirm this enhancement, as reflected by theincrement in elastic recovery and the decrease in non-recoverable compliance.In addition, LAS tests indicate that NC contributes to increasing the fatiguelife of CRMA by up to 260%. Rheological tests reveal that adding NC to CRMA canreduce by half the aging-induced hardening of the binder. Moreover, FTIRresults suggest that NC can be effectively dispersed into individual layers inthe asphalt matrix, forming asphalt nanocomposites, and thus hindering thevolatilization of light components from the binder.Overall, the results from this study show that organo-modifiednanoclay is a promising additive for CRMA, as it can i) solve the phaseseparation problem; ii) enhance the rutting and fatigue performance; and iii)delay the environmental aging process, extending the pavement’s service life.