In recent years, with the rapid growth of traffic volume, the enlargement of vehicles, the increasing proportion of heavy-duty vehicles, the serious overloading of vehicles and the channelized driving of vehicles, the service performance of asphalt pavement has been severely tested. At the same time, the high temperature and low temperature in summer and winter and the rainy and snowy climate environment have also put forward higher requirements for the service performance of asphalt pavement. In many occasions, ordinary emulsified asphalt can’t meet the requirements of asphalt pavement, so the modification of emulsified asphalt has become an imperative trend. At present, there are three commonly used methods to modify emulsified asphalt, namely, modifying with water-soluble styrene-butadiene latex (SBR); Modification by direct emulsification of asphalt modified by thermoplastic rubber (SBS); Modified with water-soluble epoxy resin.
SBS modified asphalt has become the main modified variety at present, because it can significantly improve the rutting resistance at high temperature, cracking resistance at low temperature and aging resistance, and has been widely recognized and applied.
Brief introduction of modified emulsified asphalt
Broadly speaking, modified emulsified asphalt is to improve and enhance the performance of emulsified asphalt by various methods. Compared with common emulsified asphalt, the advantages of modified emulsified asphalt are as follows: the high-temperature stability of emulsified asphalt is significantly improved; The low-temperature crack resistance of emulsified asphalt is obviously improved; Improve the adhesion of emulsified asphalt; Promote the formation of the early strength of the project; Greatly improve the strength of the completed project; It is an ideal material for repairing ruts quickly; Further expanding the application range of emulsified asphalt; Further improving the anti-aging performance of emulsified asphalt; Effectively prolonging the service life of the pavement.
Emulsification of SBS modified emulsified asphalt and characteristics of corresponding emulsifier
Compared with the original base asphalt, SBS modified asphalt has higher viscosity and softening point at high temperature, which makes the emulsification process more difficult to some extent. To ensure the smooth emulsification of SBS modified asphalt, four key factors must be met: first, SBS modified asphalt with qualified quality should be made of materials; Second, there should be high-quality emulsifier; Third, the equipment has well-equipped emulsifying equipment; Fourthly, it is necessary to have appropriate production process parameters.
Requirements of SBS Emulsified Modified Asphalt on Emulsifier
For SBS modified asphalt, because of its high viscosity, it needs to be emulsified at a higher temperature and adopt a larger shear stress. Compared with general asphalt emulsifier, the emulsifier of emulsified SBS modified asphalt should have the following characteristics:
(1) It is hydrophilic to increase the phase transition temperature (PIT) of the emulsifier, so as to adapt to the higher emulsifying temperature;
(2) hydrophilic groups with higher charge density or larger volume to provide greater electrostatic stability or stronger steric hindrance effect to improve the settling stability of larger dispersed particles;
(3) Stronger surface activity to reduce the particle size of emulsified asphalt.
Equipment requirements of SBS emulsified modified asphalt
Emulsified SBS asphalt requires high equipment, and the colloid mill should have enough power and be able to bear back pressure. As the technological temperature of emulsified SBS asphalt is relatively high, the emulsified asphalt should pass through a heat exchanger before discharging, and the temperature of emulsified asphalt should be reduced to below 90℃ to prevent demulsification of emulsified asphalt when the temperature is too high.
Application scope of SBS modified emulsified asphalt
SBS modified emulsified asphalt has a wide range of applications. According to the nature of construction, it can be used in new construction, renovation and expansion projects. According to the nature of the project, it can be used in minor repair, medium repair and overhaul projects. Among them, the specific application projects include micro-surfacing, cold recycling, cold mixing and cold paving, adhesive layer, prime layer, slurry seal layer, crushed stone seal layer, fog seal layer, bridge deck waterproofing, SBS coiled material, pavement crack filling and other projects that can use emulsified asphalt.