Rheological performance investigation and sustainability evaluation of asphalt binder with thermochromic powders under solar radiation

Significance 

Advanced paving materials have been recently developed to meet the increasing need for high-performance pavements. In particular, asphalt binder has attracted the attention of researchers for enhancing the performance of pavements due to its adhesive nature. Unfortunately, the black exterior found on most of the asphalt binders is highly disadvantageous as it increases the solar radiation absorption rate. This results in high pavement temperatures, aging-related distress, and permanent pavement deformation.

Presently, several approaches have been employed to address the aforementioned challenges. For instance, the addition of modifiers to asphalt binders to increase the aging resistances and reducing solar absorption rate are among the solution measures for enhancing the performance and durability of pavements. This is very familiar with cool paving materials, which are most suitable for reducing the pavement temperatures during summer and ineffective during winter seasons.

Development of innovative thermochromic materials is a promising solution to these challenges. These materials can adjust their appearance colors in relation to the temperature thus suitable for both summer and winter. Consequently, they exhibit dynamic optical and thermal properties that raise a lot of questions on their ability to control pavement surface temperature when used together with asphalt binder. Recent studies have shown that asphalt binder added with thermochromic materials can reduce surface pavement temperature during summer and increase the temperatures during winter. In addition, the high reflectivity especially within the near-infrared range can help resist the thermal and photo-oxidation aging that may also affect the performance of the pavement. On the other hand, indoor artificial simulations have been used to determine the durability of these materials under the effects of the natural environment. However, due to its limitations, it is also necessary to explore the aging behavior of thermochromic asphalt binder in real weathering conditions.

Recently, Hunan University scientists: Zihao Chen (PhD candidate), Dr. Henglong Zhang, Professor Caijun Shi and Chuanwen Wei (Msc candidate) cross-examined the weathering aging effects on the rheological and chemical evolutions of thermochromic asphalt binder materials. Fundamentally, the work was based on dynamic shear rheometer tests and Fourier transform infrared spectroscopy analysis. On the other hand, characterization of the rheological properties was completed using complex modulus master curve, crossover frequency among others. Chemical changes during the weathering aging process were monitored by application of carboxylic and sulfoxide indexes. Eventually, the weathering mechanisms of the thermochromic asphalt binder were evaluated. The work is published in the journal, Solar Energy Materials and Solar Cells.

The authors observed that unlike in the case of the control sample, rheological indexes of the thermochromic binders did not show any increasing or decreasing trends with weathering aging time. Furthermore, growth rates and amplitudes of carbonyl and sulfoxide indexes of thermochromic binders were much lower than those of control sample as weathering aging time increased, which indicated the less weathering aging susceptibility of thermochromic asphalt binder. Altogether, the study by Hunan University researchers will advance the development of high-performance materials for pavement construction.

Rheological performance investigation and sustainability evaluation of asphalt binder with thermochromic powders under solar radiation - Advances in Engineering
Fig. 1. The color of thermochromic powders below and above their transition temperature: the left is below 31 ºC, the right is above 31 ºC.
Rheological performance investigation and sustainability evaluation of asphalt binder with thermochromic powders under solar radiation - Advances in Engineering
Fig. 2. Carbonyl index (CI) at different indoor accelerated UV aging time for base asphalt binder (70#) and thermochromic asphalt binder (TAB).
Rheological performance investigation and sustainability evaluation of asphalt binder with thermochromic powders under solar radiation - Advances in Engineering
Fig. 3. ESEM images (magnified by 5000 times) of thermochromic microcapsules after different aging conditions: (a) Origin, (b) TFOT, (c) UV 15day, (d) UV 20day, (e) UV 25day and (f) UV 30day.

About the author

Henglong Zhang is an associate professor of Road Engineering at Key Laboratory for Green & Advanced Civil Engineering Materials and Application Technology of Hunan Province, Hunan University. He received his PhD in the field of asphalt materials from the Wuhan University of Technology, China, in 2012. He was granted by Huxiang Youth Talents Program of Hunan Province of China. He is the Editorial Board Member of “Journal of Testing & Evaluation” (SCI indexed), “International Journal of Pavement Research & Technology” (EI indexed), “Case Studies in Construction Materials” (EI indexed), “Heliyon”.

His main research interests include development and application of new pavement materials, durability theory and technology of pavement materials, recycling technology of waste pavement materials.

ResearchGate

About the author

Zihao Chen is a Ph.D. candidate in the College of Civil Engineering at Hunan University. He obtained his bachelor degree in Civil Engineering from Changsha University of Science and Technology in 2015. His research interests mainly focus on aging mechanism and characterization of asphalt materials and investigation of thermochromic asphalt materials. So far, he is the author of about 12 papers published in the high quality international (SCI) journals.

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About the author

Caijun Shi is currently a Chair Professor of College of civil Engineering, Hunan University and China Academy of Building Materials Academy. He is the head of Key Laboratory for Green & Advanced Civil Engineering Materials and Application Technology of Hunan Province. He is an Editor-in-Chief of “Journal of Sustainable Cement-based Materials”, associate editor of “Journal of Materials in Civil Engineering”, and an editorial board member of “Cement and Concrete Research”, “Cement and Concrete Composites”, “Journal of Chinese Ceramic Society” and “Journal of Building Materials”.

His research interests include characterization and utilization of industrial by-products and waste materials, design and testing of cement and concrete materials, development and evaluation of cement additives and concrete admixtures, and solid and hazardous waste management.

ResearchGate 

About the author

Chanwen Wei is a M.S. candidate in the College of Civil Engineering at Hunan University. He obtained his bachelor degree in Civil Engineering from Ludong University in 2017. His research interests mainly focus on aging mechanism and characterization of SBS modified asphalt and rejuvenation of aged SBS modified asphalt.

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Reference

Chen, Z., Zhang, H., Shi, C., & Wei, C. (2019). Rheological performance investigation and sustainability evaluation of asphalt binder with thermochromic powders under solar radiation. Solar Energy Materials and Solar Cells, 191, 175-182.

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