## 1 Introduction
[24] evaluated the water stability performance of stone mastic asphalt mixes, which showed that Marshall residual stability was improved with the addition of lignin fiber. Diatomite powder is an inorganic filler that has obtained a great interest due to its low density, low cost, low thermal conductivity, light weight [25; 26], and plentiful storage. The reserve of diatomite in China exceeds 300 million tons, ranking second after the United States [27]. Diatomite has been widely used to modify the asphalt pavement with the objective of reducing environmental pollution and producing asphalt mixes with high mechanical properties [28]. Various researchers studied the performance of asphalt mixes modified with diatomite [29; 30; 31; 32; 33; 34; 35; 36]. [PERSON] et al. [29] showed that diatomite has little enhancement on the resistance of cracking of asphalt mixes, although the water stability values of diatomite modified asphalt mix were significantly increased compared to that of the unmodified mix. [PERSON] [30] observed that the use of diatomite in pavement had a small influence on the asphalt mixes at low temperatures. [PERSON] et al. [31] revealed that the use of diatomite in sand asphalt mixes improved the low-temperature performance with increased bending tensile strength. [PERSON] et al. [32] conducted a study on modifying asphalt mix by using a combination of diatomite and basalt fibers, which showed an improvement in the anti-cracking property of mixes. However, it also reported that the diatomite had small effects on the low-temperature behavior, since it improved the tensile strength but reduced the failure strain. [PERSON] et al. [33] investigated the effect of diatomite on the anti-cracking property of asphalt mixes. Results displayed improvement in the low-temperature property of asphalt mixes. Another study was carried out by [PERSON] et al. [34] on a compound of diatomite and glass fiber used to modify the asphalt mix. Their results demonstrated that the bad effect of diatomite on the low-temperature property of asphalt mix was overcome by using glass fiber. [PERSON] et al. [35] and [PERSON] et al. [36] investigated the property of asphalt mix modified with diatomite under freeze-thaw cycle effects. It reported that the moisture damage resistance was clearly improved by using diatomite. According to the aforementioned research and the previous review [17], it is clear that using diatomite or lignin fiber can improve the asphalt mixes but in different degrees. As the performance of asphalt mixes modified by diatomite or lignin fiber is similar in some effects and different in another, the utilization of double-adding technology into mixes may be more useful on the resistance of asphalt pavement to distress than the single adding. In addition, based on the literature, the optimal content of diatomite varies from 12% to 14%, while the optimal dosage of lignin fiber is between 0.2% and 0.4%. Thus, in the present study, diatomite was selected to be 13% of the weight of asphalt binder, and lignin fiber was chosen to be 0.3% of the weight of the asphalt mix. The aim of this study to assess the performance of the asphalt mix modified with a novel composite of diatomite and lignin fiber, where the effects of the new composite on the properties of asphalt mix are still unknown. Therefore, if diatomite powder and lignin fiber are used to modify asphalt mix simultaneously, a new type of asphalt mix which has good low-temperature resistance and water stability performance may be obtained. Additionally, it will provide decision-makers with a reference for the design of composite asphalt mixes. In this paper, three points bending, Marshall immersion, and freeze-thaw splitting tests were carried out on different types of asphalt mixes including control asphalt mix (CAM), diatomite modified asphalt mix (DMAM), lignin fiber modified asphalt mix (LFMAM), and diatomite-lignin fiber composite modified asphalt mix (DLFMAM).