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Utilization of waste corn stalks (CS) has seized extensive attention due to high annual output and hazardous impact of piling aside or direct combustion on environment. However, previously there has been a lot of emphasis on improvement of its energy efficiency as solid fuel while limited investigations are available which explore the possibility of applying corn stalks as performance enhancer in asphalt binder. The purpose of this study is to examine the potential of employing hydrochar as modifiers in asphalt binder by a series of experimental tests. In this study, two hydrochar were produced from corn stalks by a novel process called hydrothermal carbonization at a different reaction temperature. The two hydrochar and their responding hydrochar-modified asphalt (HCMA) were tested by chemical and rheological tests. Chemical analysis detected the interaction between hydrochar and binder factions, resulting in poor compatibility but satisfying anti-aging property. Even though hydrochar increased the viscosity of bitumen, implying worse workability, and caused poor storage stability, ameliorated performance of asphalt binder at high temperature by incorporating hydrochar was verified by various criteria such as higher performance grade (PG) failure temperature and lower non-recoverable creep compliance (Jnr). Moreover, higher reaction temperature makes hydrochar's particles smaller and more homogeneous, which results in slightly lower enhanced high temperature performance, more satisfying workability, better storage stability, and greater anti-aging effect of hydrochar-modified asphalt. Eventually, this study provided a promising win-win solution to environment problems concerning corn stalk treatment and shortage of asphalt binder. Further exploration of methods to improve HCMA's storage stability, real-scale corroboration on trial section and life cycle assessment of asphalt pavement containing hydrochar modifiers will be followed in the future. [ABSTRACT FROM AUTHOR]

As a good asphalt modifier, natural asphalt has been the focus of more attention because of its low price and ability to improve the performance of modified asphalt. In this paper, the incorporation of a natural asphalt binder in the production of bituminous materials for pavement application in China was experimentally investigated to evaluate the feasibility of such a process and its potential benefits in terms of performance. For this purpose, an asphalt binder conventionally used in the south of China was blended with various percentages of a hard natural binder obtained from the region of Selenice in Albania. The content of Selenice natural bitumen (SNB) was 80.5%, having high molecular weight and the advantages of good stability and compatibility with virgin asphalt. The physical, rheological, and mechanical properties, as well as the modification mechanism of the binder and corresponding asphalt mixture, were evaluated in the laboratory. It was observed that the hard binder improved the response of the binder blend at high and intermediate temperature; this reflected a better stability, improved moisture susceptibility, and enhanced rutting resistance of the mixture. Fluorescence microscopy showed that after dissolving, the size of the SNB modifier became smaller and its distribution was uneven, presenting three forms, granular, agglomerated, and flocculent properties. Chemical test results showed that the modification mechanism of SNB was mainly related to the enhancement of hydrogen bonds and Van der Waals forces caused by sulfoxide and carbonyl along with the stress concentration caused by silica particles. Molecular composition revealed that the proportion of middle molecules has reduced while the proportion of large molecules has increased. It is considered that SNB is a promising low-priced natural modifier with excellent rutting resistance properties. Future research will be focused on the economic analysis, pavement life cycle assessment of SNB modified asphalt, and its application in perpetual pavements. [ABSTRACT FROM AUTHOR]