Important factors affecting the stability of emulsified asphalt

In order to meet the needs of transportation, storage and reprocessing of emulsified asphalt, how to produce higher quality emulsified asphalt has become an urgent problem. Generally speaking, the factors affecting the stability of emulsified asphalt are closely related to raw materials, equipment and production technology, such as asphalt, emulsifier, water quality, equipment, stabilizer, defoamer, production temperature and storage temperature.

1. The dosage of emulsifier: Generally, within a proper dosage range, the larger the dosage of emulsifier, the smaller the particle size of emulsified asphalt. It is generally believed that before the optimal dosage is reached, with the increase of dosage, the micelle concentration increases, the more monomer is compatibilized in the micelle, the less free monomer liquid is, and the smaller monomer droplets are. When the dosage continues to increase beyond the optimum dosage, a large number of free micelles agglomerate, which leads to the increase of particle size and the decrease of stability.

2. Selection and dosage of stabilizer: The traditional single stabilizer, such as cellulose, has poor compatibility with the system, which mainly shows that it is difficult to break the emulsion quickly and achieve long-term stability, which may be related to the shortcomings of cellulose itself, such as poor mildew resistance, poor temperature resistance and poor PH tolerance. It is necessary to adopt multiple combinations to achieve synergy to solve such problems. In the dosage test, it was found that when the dosage of stabilizer was too low and asphalt particles and water were close to each other, the surface tension was too high, which led to oil-water separation, that is, demulsification. When the dosage of stabilizer was too high, the viscosity change of soap solution would lead to shear difficulty and stability decline. The data show that the content of stabilizer in the system should not be higher than 3‰.

3. Selection and output of defoamer: The selection of defoamer should follow the varieties suitable for adding in the formula, with high concentration and low addition. Excessive dosage will seriously affect the storage stability, even if it does not affect the storage stability, it may make the surface of the finished product honeycomb, thus affecting the dispersion and fluidity of emulsified asphalt.

4. Storage temperature: Emulsified asphalt is a thermodynamically unstable system. When the internal solution is at a higher temperature, the Brownian motion of particles is accelerated, the collision probability between particles is increased, some emulsions are demulsified, and oil and water are separated. After the preparation of emulsified asphalt, the discharge temperature can reach 90℃, which has a large temperature difference with the outside world and is easy to crust. It should be slightly stirred and cooled to the ambient temperature to eliminate and reduce the crust phenomenon and sealed for storage.