Since the 1980s, in order to adapt to the modern heavy traffic on the pavement material performance requirements to improve the characteristics of a number of countries in Europe and the United States began a wide range of fiber-reinforced asphalt material application research, and thus the formation of a number of patented products. Germany through the asphalt mixture with fiber research and observation shows that the addition of fiber can improve the high temperature stability of asphalt mixture, fatigue durability, and has a low-temperature crack resistance and prevention of reflective cracking performance [1]. It is due to the above excellent qualities that fibers are also used in airport road surfaces, bridge deck paving, toll booths and other pavements. The United States, Canada, Germany and other countries have used lignin fiber concrete to build a large number of highways and other heavy traffic roads. The United States, Canada, Germany and other countries using lignin fiber concrete to build a large number of highways and other heavy traffic highway.

1, fiber moisture absorption, oil absorption:

The hygroscopicity of the fiber depends mainly on the material of the fiber. If the hygroscopicity of the fiber is very large, the outside world's moisture is easier to invade, will make the fiber asphalt interface erosion and wet swelling, reduce the water stability of the mixture, so the fiber hygroscopicity is not easy to be too large. Lignin fiber and mineral fiber hygroscopic volume expansion is obvious, you can pinch out the water, fiber color deepening, indicating that lignin fiber and mineral fiber easy to absorb water, should be stored before use to avoid rain.

Oil absorption index reflects the fiber adsorption capacity of asphalt [2]. The oil absorption rate comparison test was made between the wetting time of 5min and 60min. The results show that the infiltration time has almost no effect on the oil absorption rate, which indicates that in addition to the role of the interface such as adsorption, the fiber is not obvious on the absorption of mineral oil. Fiber absorption of mineral oil is not obvious.

2, fiber and asphalt adhesion:

Adhesion reflects the water stability of fiber asphalt mastic and fiber constraint crack expansion, constraint material loosening ability. Determination of the percentage of residual asphalt on the fiber after cooking in boiling water for 30min [3], lignin is 99%, mineral fiber is about 93%, while limestone is only about 85%, which shows that the fiber has a strong adhesion to asphalt ability to enhance the water stability of asphalt mixtures and resistance to stripping. Enhance the water stability and stripping resistance of asphalt mixture.

3, net blue precipitation dripping:

The effect of various fibers to absorb and hold asphalt is related to the ambient temperature. When the temperature is high, the asphalt film is thin, the viscosity is reduced, the fiber material absorption effect is significantly reduced. If the fiber at 140 ℃ when the asphalt absorption of 100%, 160 ℃ down to 75%, 170 ℃ only 70%. Lignin fiber absorption of asphalt ability to show good results, at 140 ℃, 1g lignin fiber can absorb 10g asphalt, in the temperature increased to 170 ℃ can still absorb 9g asphalt, mineral fiber than lignin fiber is slightly worse; at 140 ℃, mineral powder asphalt slurry all drops, indicating that although the surface area of the mineral powder is also larger, room temperature can be adhered to asphalt, but when the asphalt is in the hot melt flowing State, or can not hold asphalt, indicating that the fiber because of its chemical composition, structure and a large specific surface area, the adsorption capacity of asphalt is very strong, the fiber is significantly better than the role of asphalt adsorption of mineral powder.

4, water stability:

Lignin fiber texture loose, rough surface, into a porous, more lateral branching; asphalt in the acidic resin component is a surface-active substances, it is produced in the lignin fiber surface physical infiltration, adsorption and even chemical bonding, so that the asphalt was a single molecule arranged on the surface of the lignin fibers, the formation of a solid binding force of the "structure of the asphalt" film! It is more viscous than the film outside the free asphalt, good heat resistance; at the same time, due to the lignin fiber adsorption and absorption, the amount of asphalt blended material increased, can make the structural asphalt membrane thickened 65% to 113% [4]; lignin fibers and their surrounding structural asphalt wrapped together on the surface of the aggregate, so that the asphalt film thickness and nature of the asphalt film are changed than. Thicker asphalt membrane slows down the asphalt aging rate, which can maintain its adhesion for a long time, reduce the water on the asphalt and aggregate erosion damage, enhance the ability of asphalt mixtures to resist water damage, so that the mixture of water stability enhancement.

5, high temperature stability:

The distribution of lignin fibers within the asphalt matrix is three-dimensional random. Due to the slender cross-section, so that the lignin fiber doping is not large asphalt matrix within the number of lignin fibers is quite large, forming a longitudinal and transverse spatial network. On the one hand, wrapped in the lignin fibers on the "structural asphalt" network, increasing the proportion of structural asphalt, thinning the free asphalt film, so that the lignin fiber asphalt mortar viscosity increases, the softening point rises, high temperature stability is greatly improved; on the other hand, the longitudinal and transverse interweaving of the lignin fibers in the mixture of the non-directional distribution and each other.