# Field Trial and Performance Evaluation of Soybean-Based Bio-Fog Seals for Asphalt Rejuvenation
###### Abstract
In addition to cost, a proactive investment in preventive maintenance can also reduce environmental pollution, resource demand, and energy consumption over the life cycle of the pavement [9; 10]. To minimize aging effects on the pavement surface, particularly on the top layer, which experiences the most aging, two approaches can be employed: physical and physiological [11]. The physical strategy consists of sealing the pavement and forming a protective barrier that mitigates the penetration of water. A common technique is fog sealing, where a thin layer of diluted asphalt emulsion is applied to the surface of roads in good condition, ideally under 3 years old [12; 13], closing interconnected voids, filling small cracks, and preventing moisture damage [14; 15]. However, it can initially reduce pavement friction by over 50% [16]. To mitigate this short-term safety concern, loose aggregate (sand) is often applied after fog sealing, improving initial friction. The physiological approach focuses on healing existing damage and restoring the asphalt binder's properties [17]. Rejuvenator seals combine both physical and physiological approaches. They seal the surface and rebalance the asphalt fractions, decreasing its viscosity and stiffness, and counteract aging damage, minimizing the need for extensive rehabilitation [18]. Traditional rejuvenators in fog seals are typically petroleum-based, but the need for sustainable alternatives has led to an increased interest in bio-fog seals [19; 20]. These seals utilize bio-based rejuvenators derived from vegetable oils, wood oils, or other organic compounds formulated into emulsions that are sprayed on the pavement. During application, the bio-rejuvenator emulsion penetrates the asphalt matrix through diffusion, as illustrated in Figure 2a,b. The rejuvenator molecules then soften and reduce the viscosity of the aged binder. This allows the rejuvenated binder to flow through open microcracks, facilitating a self-healing and sealing process under optimal temperatures and sufficient time (Figure 2c,d) [21]. Figure 1: PCI progression over the pavement life. Optimal allocation of dollars obtained by investing in preservation offsetting the need for major interventions, such as rehabilitation and reconstruction. Various bio-based rejuvenator products are currently available in the market. Soybean-derived additives have demonstrated effectiveness as rejuvenators, reducing the stiffness and viscosity of aged and brittle asphalt binders [22]. Iowa State University (ISU) has developed soy-based biotechnologies showing promise in rejuvenating aged asphalt [23; 24]. Among them are partially epoxidized soybean oil (SESO) and BioMag. BioMag is a balanced combination of SESO and the biopolymer poly(acrylated epoxidized high oleic soybean oil) (PAEHOSO) in a 50/50 ratio. Beyond the immediate benefits of pavement rejuvenation, these soy-based bio-fog seals offer significant environmental advantages, including carbon capture during production leading to a negative global warming potential, and minimizing the environmental footprint of pavement maintenance [25]. Despite the growing interest in sustainable pavement maintenance solutions, a critical knowledge gap exists regarding the field performance of bio-based rejuvenators. This research aims to bridge this gap by evaluating the effectiveness of soy-based bio-fog seals in restoring pavement properties crucial for longevity without sacrificing safety in real roads. To examine whether these materials meet the expectation of a fog seal and provide value to the pavement, we will evaluate their impact on pavement stiffness, flexibility, and permeability. Furthermore, a particular focus will be placed on safety, investigating the effect of the treatments on pavement friction, pavement markings, and traffic disruption. By addressing these objectives, this study holds significant value by contributing to developing sustainable preventive maintenance strategies for asphalt pavements.