Effect of the addition of soybean fatty acid on asphalt binders using Fourier-Transform Infrared Spectroscopy

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Abstract

The use of residual materials as rejuvenating agents for recovered asphalt binder is gaining attention for its environmental and economic benefits. Soybean oil soapstock fatty acid (SSFA), a byproduct from soybean oil refining, was evaluated as a rejuvenator through Fourier-transform infrared spectroscopy (FTIR) analysis. PG 64-XX asphalt binder was modified with SSFA at 1%, 3%, 5%, 6%, and 7% by weight. Additionally, SSFA was incorporated into recovered asphalt binder (from Reclaimed Asphalt Pavement) at 5%, 7%, 10%, 15%, and 20%. Results showed that SSFA addition increased carbonyl group peaks, indicating the restoration of light fractions lost during asphalt service life. Samples with higher SSFA content displayed prominent peaks around 1745 and 1715 cm⁻¹ and significant stiffness reduction. This demonstrates SSFA's potential to rejuvenate both virgin and recovered asphalt binders. Utilizing SSFA aligns with circular economy principles, enhancing performance while reducing the use of virgin materials and mitigating hazardous waste issues.