Emulsified asphalt

I. Production process flow of emulsified asphalt: Liquid asphalt and emulsifier are mixed in a proportion controlled to determine the amount used, thereby producing emulsified asphalt. This is the most basic process flow for the production of emulsified asphalt. The equipment used for large-scale production of emulsified asphalt is also designed and manufactured based on this process and principles. For ordinary emulsified asphalt, the requirements for such equipment are not very high; however, for special types of emulsified asphalt or special base asphalts, in addition to process control, specific requirements are also placed on the equipment. II. Control of matrix asphalt temperature and viscosity: As we know, the viscosity of asphalt decreases as the temperature rises; for every 12°C increase, its dynamic viscosity roughly halves. From the above process flow and emulsification principles, it can be seen that during production, the matrix asphalt must first be heated to a liquid state before emulsification can take place. To match the emulsification capabilities of the colloid mill, the dynamic viscosity of the matrix asphalt is generally kept at around 200 cst. The lower the temperature, the higher the viscosity, which increases the load on the asphalt pump and the colloid mill, making emulsification more difficult ； On the other hand, to prevent demulsification caused by excessive vaporization of water in the final product during the production of emulsified asphalt, it is also not possible to raise the temperature of the base asphalt too high ； Excessively high temperatures have another negative effect: since acid is added in the production of emulsified asphalt, stainless steel must be used as the material for colloid mills. However, stainless steel becomes sticky at high temperatures, the cutting edges lose their sharpness, and thus the shearing efficiency decreases. The material and design of the colloid mill are crucial elements of the equipment, and only a very few manufacturers possess the technology to produce such materials ； Taking all the above factors into account, the outlet temperature of the finished product from the colloid mill should generally be kept below 85℃ ； Taking the AH-70 as an example, the matrix asphalt is generally heated to about 140°C, while the soap solution is heated to about 35°C℃ ； Assuming an asphalt content of 60% in the finished emulsified asphalt, the temperature of the product at the outlet of the colloid mill is: T = (0.5×60×140 + 40×35) / (0.5×60 + 40) = 80°C. Since the asphalt content in ordinary emulsified asphalt used in China is usually around 50%, the temperature during production will be much lower than this value. Additionally, the base asphalt used is often of grade 70 or even higher, and its dynamic viscosity is not very high; therefore, with standard emulsified asphalt production equipment, there is no need to worry about these issues. However, for some special types of emulsified asphalt, an asphalt content of over 65% is required; base asphalt of grade 30–50 or SBS-modified asphalt is used for emulsification. The dynamic viscosity of this asphalt is approximately 3–10 times that of the commonly used AH-70 asphalt. Due to this increased viscosity and content, the colloid mill used in conventional emulsified asphalt production may not be able to function properly. To accommodate the capabilities of the colloid mill, it is necessary to raise the temperature of the base asphalt to around 160°C and the temperature of the soapy solution to around 55°C. At this point, the temperature of the finished product exiting the colloid mill is: T = (0.5×65×160 + 35×55) / (0.5×65 + 35) = 105.6°C. The emulsified asphalt at this stage is in a boiling state, and special processes are required to prevent its demulsification; such products should be produced using equipment designed for modified emulsified asphalt. III. Control of emulsified asphalt temperature and pressure: As can be seen from the above, if the asphalt temperature is too low, it will cause excessive load on the colloid mill, preventing emulsification; on the other hand, if the temperature is too high, vaporization will occur leading to demulsification. Therefore, a cooling device is necessary to keep the outlet temperature below 85°C ； Furthermore, based on the principle that boiling point increases with rising pressure, an appropriate pressure must also be maintained throughout the system to prevent the emulsified asphalt from vaporizing and breaking into separate phases before it reaches the cooling device ； According to the Venturi effect, 90° bends should be avoided as much as possible throughout the entire system, in order to prevent vaporization and demulsification in the negative pressure area at the back. IV. Using ordinary emulsified asphalt production equipment through the addition of additives: We can add diluents and similar substances to the base asphalt in order to reduce its viscosity, thereby enabling production using ordinary emulsified asphalt equipment. At a rate of 5% of the base asphalt, with a cost of 7,500 yuan per ton, this adds approximately 125 yuan to the material cost per ton of emulsified asphalt. Moreover, it introduces a range of issues related to procurement, transportation, safety, and regulatory requirements, so it should be used with caution.

It’s quite complicated. I’ve been working on emulsified asphalt lately, and it’s hard to choose the right emulsifier

If you’re in the Northeast, you could check out Jilin Hengsheng Chemicals; they produce emulsifiers there. I’ve done experiments with their products, and the results were quite good. The medium-split instant type has good effects.