Smart Self-Healing Capability of Asphalt Material Using Bionic Microvascular Containing Oily Rejuvenator

Abstract

It has become one of the research directions of intelligent materials for self-healing asphalt pavements to use a bionic microvascular containing oily rejuvenator. The rejuvenator in a microvascular can carry out the healing of asphalt micro-cracks, thus reducing the damage to and prolonging the life of asphalt pavement. The aim of this work was to investigate the smart self-healing capability of an asphalt/microvascular material through its microstructure and mechanical properties. Microstructure observation indicated no interface separation between the microvasculars and bitumen matrix. Micro-CT images showed that microvasculars dispersed in asphalt samples without accumulation or tangles. The phenomenon of microcracks healing without intervention was observed, which proved that the fractured asphalt sample carried out the self-healing process with the help of rejuvenator diffusing out from the broken microvasculars. The self-healing efficiency of asphalt samples was also evaluated through a tensile test considering the factors of microvasculars content, healing time and healing temperature. It was found that the tensile strength of the asphalt samples was greatly enhanced by the addition of microvasculars under a set test condition. Self-healing efficiency was enhanced with more broken microvasculars in the rupture interface of the asphalt sample. During two self-healing cycles, the self-healing efficiency of the asphalt sample with three microvascular per 1 cm2 of a broken interface were able to reach 80% and 86%. This proves that microvasculars containing rejuvenator play a practical role in the self-healing process of asphalt. With an increase in temperature from 0 to 30 °C, the self-healing capability of the asphalt samples increased dramatically. An increase in time increased the self-healing capability of the bitumen samples. At last, a preliminary mathematical model also deduced that the self-healing efficiency was determined by the individual healing steps, including release, penetration and diffusion of the rejuvenator agent.

Multiscale Mathematical Analysis of Influencing Factors and Experimental Verification of Microcrack Self-Healing Efficiency of Bitumen Composites Using Microcapsules

“…In addition, we can see from this relationship that temperature ( T ) is another crucial factor affecting E SH value. In previous work [ 19 ], the movement of bituminous molecules depends on the time–temperature superposition principle. The E SH model of bitumen can be described by the time–temperature superposition principle, as shown in Equations (8) and (9), where α T is the time–temperature superimposed displacement factor, β and δ are model parameters, Δ E a is the apparent activation energy (unit: J/mol), and R is the general gas constant (8.314 J/(mol · K)).…”

“…Therefore, accurately calculating the stress intensity factor is crucial when using fracture mechanics to study the crack growth problem. It has been reported that Griffith’s theory has been applied to analyze the condition of microcrack propagation from the energy perspective [ 19 , 20 ]. When the coarse elastic strain reduction in the object is more significant than or equal to the surface required for the crack to form two new apertures, the crack will expand.…”

“…In addition, we can see from this relationship that temperature (T) is another crucial factor affecting E SH value. In previous work [19], the movement of bituminous molecules depends on the time-temperature superposition principle. The E SH model of bitumen can be described by the time-temperature superposition principle, as shown in Equations ( 8) and ( 9),…”

“…Therefore, when using fracture mechanics to study the crack growth problem, accurate assessment of the stress intensity of the material is essential. According to Griffith's crack fracture mechanics theory [20], the critical stress of microcrack propagation (σ c ) can be expressed as Equation (19),…”