| Summary: | The modifiers NTC (nano-TiO<sub>2</sub>/CaCO<sub>3</sub>) and BF (basalt fiber) were adopted to modify a base matrix asphalt mixture. The base matrix asphalt mixture and three kinds of modified asphalt mixture under F⁻T (freeze⁻thaw) cycles were scanned by computed tomography. The air voids and morphological changes of asphalt mixture were summarized by image processing technology, and the development process of F⁻T damage to asphalt mixture was explained from a micro-view. The porosity of NTC-modified asphalt mixture changed little, and the void distribution between base matrix asphalt mixture and NTC-BF (nano-TiO<sub>2</sub>/CaCO<sub>3</sub> and basalt fiber) composite modified asphalt mixture was more uniform. The macro-pores in the asphalt mixture under 15 F⁻T cycles began to connect gradually, and the pore characteristics also changed. The number and shape of the pores changed under 15 F⁻T cycles. According to the state characteristics, the change amplitude of the pore characteristics of matrix asphalt mixture and NTC-BF composite modified asphalt mixture were the most stable under F⁻T cycles.
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