Avaliação da autocura de materiais asfálticos com adição e fibras de ácido graxo da borra de óleo de soja.

Abstract

Asphalt pavement is subject to factors such as oxidation, solar radiation, thermal variations, repeated traffic, and humidity, which cause binder aging and the appearance of microcracks, which can evolve into macrocracks and reduce the pavement's lifespan. These cracks can regenerate automatically under suitable environmental conditions due to an inherent property of asphalt materials called self-healing. To enhance this phenomenon, methodologies such as the use of encapsulated rejuvenators have been studied, allowing for the controlled release of the healing agent within the asphalt matrix. Replacing capsules with fibers improves the distribution of rejuvenators in the asphalt matrix, in addition to eliminating the excessive reduction in stiffness associated with the addition of capsules in asphalt mixtures. In this context, fatty acid from soybean oil sludge is a sustainable, low-cost rejuvenator option capable of restoring the chemical and mechanical properties of aged binder. This research investigated the self-healing capacity of asphalt binders and mixtures with the addition of fatty acid fibers derived from soybean oil sludge, in different proportions between the casing material and the rejuvenator, namely: 1:1.5; 1:2.0; 1:2.5; 1:3.0 and 1:3.5. The methodology consisted of four stages. In the first stage, the chemical properties of the asphalt binder were studied using Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA). In the second stage, rheological tests were conducted on the binder, such as Rotational Viscosity, Performance Grade (PG), Multiple Stress Creep and Recovery (MSCR), and Linear Amplitude Sweep (LAS). In the third stage, the mechanical properties of the asphalt mixtures were evaluated through tensile strength (TS), moisture-induced damage, resilient modulus (MR), resistance to permanent deformation, and fatigue tests. In the fourth stage, the self-healing of the asphalt materials was studied: the binder was analyzed on a microscale using Optical Microscopy (OM), and for the mixtures, the Semi-Circular Bending (SCB) test was used for macroscale evaluation, in addition to Computed Tomography (CT) analyses to investigate self-healing on a microscale. The results indicated that the addition of fibers preserved the stiffness and structural integrity of the asphalt binder, even under progressive damage accumulation. The modified formulations showed greater resistance to oxidative aging with increasing deformation levels, as well as superior thermal stability. Improvements were also observed in resistance to permanent deformation and an increase of up to six times in resistance to fatigue cracking, compared to the unmodified binder. The modified binders exhibited significant Healing Index (HI) values, with an increase of 337.39% compared to the fiber-free formulation. In asphalt mixtures, the addition of fibers did not significantly alter tensile strength, stiffness, or retained tensile strength after moisture-induced damage. Improvements were also observed in resistance to permanent deformation, fatigue performance, crack propagation retardation, fracture resistance, and ductility under monotonic loading. Regarding curing, analyses obtained through MicroTC showed that the modified mixtures presented up to an 88.24% increase in HI compared to the reference mixture, highlighting the potential of fibers in intensifying self-healing in binders and asphalt mixtures. Conversely, analyses using the SCB assay proved inadequate for evaluating self-healing in asphalt mixtures due to methodological limitations. In general, fibers containing fatty acid derived from soybean oil sludge have shown effectiveness in promoting the self-healing of asphalt materials.