Abstract
Effective thermal conduction modification in asphalt binders is beneficial to reducing pavement surface temperature and relieving the urban heat island (UHI) effect in the utilization of solar harvesting and snow melting pavements. This study investigated the performance of two nanometer-sized modifiers, graphene (Gr) and carbon nanotubes (CNTs), on enhancing the thermal, physical and rheological properties of asphalt binders. Measurements depending on a transient plant source method proved that both Gr and CNTs linearly increased the thermal conductivity and thermal diffusivity of asphalt binders, and while 5% Gr by volume of matrix asphalt contributed to 300% increments, 5% CNTs increased the two parameters of asphalt binders by nearly 72% at 20 °C. Meanwhile, a series of empirical and rheological properties experiments were conducted. The results demonstrated the temperature susceptibility reduction and high-temperature properties promotion of asphalt binders by adding Gr or CNTs. The variation trends in the anti-cracking properties of asphalt binders modified by Gr and CNTs with the modifier content differed at low temperatures, which may be due to the unique nature of Gr. In conclusion, Gr, whose optimal content is 3% by volume of matrix asphalt, provides superior application potential for solar harvesting and snow melting pavements in comparison to CNTs due to its comprehensive contributions to thermal properties, construction feasibility, high-temperature performance and low-temperature performance of asphalt binders.
Highlights
Asphalt is a kind of viscoelastic material, which is widely applied in pavement construction
The black color of asphalt gives rise to high pavement surface temperatures due to the strong absorption of solar radiation, especially during the summer, which plays a crucial role in the urban heat island (UHI) effect and a number of pavement diseases including thermooxidative aging and rutting under traffic loads [3,4]
The results showed that multi-walled carbon nanotubes (MWCNTs) improved the rutting resistance as well as thermal cracking resistance of asphalt binders
Summary
Asphalt is a kind of viscoelastic material, which is widely applied in pavement construction. Feng et al [7] substituted crushed ceramic waste aggregates for a percentage of the coarse aggregates in asphalt concrete and reported the reduction of thermal conductivity and the narrowing of the pavement temperature gradient, resulting in the decrease of pavement temperature Another method is to employ asphalt pavement as a solar heat collector, which harvests solar energy at sunny days and carries the heat away by circulating fluid through deep embedded pipes to store for de-icing pavement or for heating inhabitant buildings at cold days [3,8,9]. The reasons always concentrate on the common traits of the “carbon family” including good thermal conductivity, strong corrosion resistance, general chemical inertia, and close density with mineral filler of asphalt concrete In this case, two well-known advance carbon nanomaterials, graphene (Gr) and carbon nanotubes (CNTs), deserve our anticipation for their application in solar harvesting and snow melting pavements. Their favorable contribution to the promotion of some other properties of asphalt composites has been demonstrated, few reports have emphasized a direct comparison of their effects on asphalt composites and further analyzed the differences
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