Characteristics of Asphalt Modifiers

Although there are many kinds of polymers that can be used for asphalt modification, the polymers used in practical engineering are mainly SBS, SBR, EVA and PE.

SBS can be divided into star structure and linear structure according to the structure type. The relative molecular weight of SBS with star structure is very high, and the compatibility with the base asphalt is very poor, but the performance of the asphalt is greatly improved; the compatibility between SBS with linear structure and the base asphalt is better than that of SBS with star structure, but its modification effect is not as good as that of star structure SBS.SBS The main advantages of modified asphalt can significantly improve the high temperature and low temperature performance of the base asphalt, improve the rutting resistance of the pavement, reduce the low temperature cracking temperature, and have good fatigue resistance and adhesion properties. It is a kind of asphalt modifier with good performance. SBS modified asphalt generally requires strong mechanical dispersion in the preparation process, and it is easy to segregate when stored in liquid conditions. Therefore, suitable stabilizers must be added when it is produced by premixing method.

EVA is a copolymer of ethylene and vinyl acetate, which is a typical random copolymer. When the vinyl acetate content is low and the melt index is small, it helps to improve the high temperature performance of the matrix asphalt; on the contrary, it is beneficial to improve the flexibility and low temperature crack resistance of the matrix asphalt. EVA has good compatibility with asphalt and is easy to disperse in asphalt. In hot mix asphalt, it only needs to be mixed with a convection stirring machine, but it will still be isolated when stored under static conditions, and it must be fully stirred before use. EVA can improve the high temperature stability, low temperature flexibility and elasticity of asphalt, and is suitable for the maintenance of high-grade highway pavement.

PE can be divided into two categories: high density (HDPE) and low density (LDPE). Only LDPE can be used for asphalt modification. PE has poor compatibility with asphalt. After it is mixed with hot asphalt, some flexible and curled PE branches are combined with each other to form a network cross-linked structure, which can significantly improve the high temperature stability and low temperature adhesion of asphalt. However, with the increase of its dosage, the low temperature ductility of modified asphalt decreases and the low temperature performance deteriorates. PE can improve the adhesion of matrix asphalt. Taking acidic minerals as an example, its adhesion can be improved by 2 to 3 grades.

SBR modified asphalt also has segregation problems, but its compatibility with asphalt is better than that of SBS. SBR can improve the rheological properties of asphalt, greatly improve the viscoelasticity and low temperature ductility of asphalt; at the same time, it can also improve the adhesion and viscosity of asphalt. Toughness, reducing its temperature sensing performance. SBR modified asphalt has good impact resistance, cracking resistance, wear resistance and waterproof ability, prolonging the service life of roads.