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

ORTIZ DE ZÁRATE, F.I.; ZAPATA FERRERO, I.; HORMAIZTEGUI, M.E.V.; BONAZZOLA, M.; REGENHARDT, S.A.; BOTASSO, H.G.; MEYER, C.I.

Buenos Aires

Congreso; WCCE 11th World Congress of Chemical Engineering; 2023

Asociación Argentina de Ingenieros Químicos

The use of crumb rubber recycled from scrap tires as an asphalt modifier has many benefits, mainly, it improves the rutting and fatigue performance of pavement, while eliminating environmental and economic problems. Nonetheless, this technology has some limitations, such as the phase separation concern during storage and transportation, and the deterioration of its performance due to environmental aging. In recent years, nanomaterials have attracted great interest in the pavement research community, as they can be considered ideal additives for the development of a new generation of paving materials[1]. Specifically, nanoclay has shown potential as a complementary additive in polymermodified asphalts, addressing its main shortcomings. However, there is still a lack of systematic investigations on the subject. The objective of this study is to evaluate the contribution of organo-modified nanoclay on the rutting, fatigue and anti-aging performance of crumb rubber-modified asphalt. Organo-modified nanoclay (NC) was prepared through cation exchange between a natural montmorillonite and benzalkonium chloride. Two kinds of asphalt (CA20 and CA30) were modified with 20% crumb rubber and 0, 3 and 5% NC using a high-shear mixer. Rheological properties of the modified asphalts were assessed by means of temperature and frequency sweeps, Multiple Stress Creep and Recovery (MSCR) and Linear Amplitude Sweep (LAS) tests. Phase separation was 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 poor storage stability. The addition of nanoclay alleviates substantially the phase separation problem, reducing the difference in softening point to less than 2.5°C, which indicates satisfactory storage stability. Rutting resistance of CRMA is improved by the addition of nanoclay, according to the results of temperature sweeps. MSCR tests confirm this enhancement, as reflected by the increment in elastic recovery and the decrease in non-recoverable compliance. In addition, LAS tests indicate that NC contributes to increasing the fatigue life of CRMA by up to 260%. Rheological tests reveal that adding NC to CRMA can reduce by half the aging-induced hardening of the binder. Moreover, FTIR results suggest that NC can be effectively dispersed into individual layers in the asphalt matrix, forming asphalt nanocomposites, and thus hindering the volatilization of light components from the binder. Overall, the results from this study show that organo-modified nanoclay is a promising additive for CRMA, as it can i) solve the phase separation problem; ii) enhance the rutting and fatigue performance; and iii) delay the environmental aging process, extending the pavement’s service life.