###### Abstract  
Moisture damage and low-temperature cracking are common distresses experienced by road pavement. Different types of modifiers, such as fibers, can be used to improve the quality of asphalt pavements. In this paper, lignin and glass fiber were selected as additives to enhance the water- and low-temperature stability of the asphalt mixtures. The main objective of this study was to evaluate the composite effects of adding lignin fiber and glass fiber to a bituminous mix using experimental methods. The Marshall immersion, freeze-thaw splitting, and three-point bending tests were applied to evaluate the efficiency of lignin fiber (and/or) glass fiber modified asphalt mixes with regard to moisture damage and low temperature. Four kinds of asphalt mixtures, namely, the control asphalt mix (C), lignin fiber modified asphalt mix (L), glass fiber modified asphalt mix (G), and a composite of lignin fiber and glass fiber modified asphalt mix (LG) were evaluated. The experimental results showed that with the addition of 0.30% lignin fiber and 0.30% glass fiber the water stability, low-temperature stability, and quality of bituminous mix were improved significantly. With lignin fiber, the asphalt mixtures showed better resistance to thermal cracking, while glass fiber resulted in greater moisture susceptibility. The composite admixture was more effective than either lignin or glass fiber in modifying the asphalt performance. This clarifies the great beneficial effect of using the composite mixture in the asphalt mixtures industry. asphalt mixture; moisture susceptibility; low-temperature stability; composite mixture; lignin fiber; glass fiber +
Footnote †: journal: Medical  
Several tests have been employed to estimate the water stability performance of bituminous mixes [10]. In this study, two test methods, Marshall immersion and freeze-thaw splitting, were carried out to assess the moisture susceptibility of bituminous mixes. Low-temperature thermal cracking is common form of distress in pavement structures [11], as low temperatures induce thermal tensile stresses in cold winter climates [12]. Transverse cracks are the most common mode of failure in asphalt pavements, as low temperatures have an undesirable effect on the integrity and continuity of the pavement, and reduce the adhesion force between the asphalt and aggregate. They begin in the upper layer of the asphalt pavement and then spread and expand downwards with time, allowing water penetration in the asphalt layer to fill these cracks [13]. Several previous studies evaluated the low-temperature properties of a bitumen mix [14; 15; 16]. In this study, the three-point bending test was selected to evaluate the behavior of bituminous mixes at low temperature. Placing additives such as rubber powder, polyethylene, and basalt fiber in bituminous mixes is one of the most popular techniques used in past studies to extend the lifetime of asphalt pavements, improving their performance and resulting in a good economic advantage. The authors of these studies proved that these additives had a very good effect on the rutting performance of bituminous mix, although the improvement was not significant with respect to low-temperature and water stability, and it is very difficult to improve all properties of bituminous mixes at the same time using a single additive [17; 18]. Therefore, researchers began to consider double-adding admixture technology [19; 20]. Hence, a number of studies have recognized the effect of fibers to modify the water stability and thermal cracking resistance of bituminous mixes [5; 8; 21]. There are different kinds of fibers and in this paper, two kinds of fibers, namely, lignin fiber and glass fiber, were selected to enhance the characteristics of a bituminous mix under different moisture and climate conditions. This study aimed to explore the compound effects of adding lignin and glass fiber simultaneously on performance with regard to the water and low-temperature stability of the asphalt mix.