Some explanations about modified asphalt

Release Time:2018-08-09

I would like to make a very common explanation for the problems of colloid mill rotation speed and modifier dosage proposed by experts in the production of modified asphalt. If there is a logical explanation, then there is still some truth.

First, the colloid mill speed

At least so far, the literature we have contacted has not specified the colloid mill speed in detail, and there is no relevant technical standard for this. So 4000rpm is still 3000rpm, even 6000rpm is good, not at all, but in line speed, the following simple example should be easy to explain this problem. Assuming that the A colloid mill speed is 3000 rpm, the average rotor diameter is 600 mm; the B colloid mill is 4000 rpm, and the stator rotor has an average diameter of 400 mm. Then the average linear velocity of A is: 600÷1000×3.14×3000÷60=94.2m/s The average linear velocity of B is: 400÷1000×3.14×4000÷60=83.73m/s The data size is easy to compare. Not much explanation. The following explains why the famous imported brands such as German Sefer or Dalworth in the United States, or the largest domestic grinding machine, set the rotational speed to 3000 rpm, because the rated speed of the pole motor is just like this. If the speed is increased, the shifting device must be used, and the structure will become complicated. In addition, the higher the rotational speed, the larger the heat generation and the shorter the bearing life. Not only does it consume more energy, but it also reduces life.

Second, the role of colloid mill

We are doing colloid mills. From the perspective of interests, we are more willing to promote the use of colloid mills, but with the scientific conscience, it must be said that colloid mills do not determine the performance of modified asphalt. It simply refines SBS, promotes dispersion and dissolution, but does not determine the final indicator of modified asphalt. To give a simple example, just like dissolving the sugar pieces in water, we can use three ways: one is to grind the sugar pieces, which is equivalent to over-grinding; the other is to stir with chopsticks; the third is to throw into the water naturally. Dissolved. The sweetness and sweetness of the syrup should not matter with the method. Let's explain why we choose SBS as a modifier in large quantities instead of latex or resin. SBS is a block copolymerization of butadiene and styrene. The glassy temperature of butadiene is about -40 ° C, and the glass temperature of styrene is about +90 ° C. Because of this, the modified asphalt is at high temperature or low temperature. In order to maintain its original state, that is, the high temperature does not deform and the low temperature does not crack. Other polymers do not have such properties. It should be well understood now that even if the SBS is finely ground, if it is not well developed and degraded, it will not exhibit the above properties, just like if the candy is ground into a powder, if it is not dissolved into the water, You can't drink sweet water. The role of grinding is to grind the sugar pieces into powder, let us drink the sweet water as soon as possible.

Third, on the non-grinding production

Through the above explanation, you should be able to feel that no grinding can be produced, just as sugar cubes are thrown into the water and the water will become sweet. The actual situation is that many companies in the United States, Japan and other countries still use non-grinding production. The domestic Zhejiang Jiayue and Qingdao Ji Ritong are also produced by the non-grinding method. We have milled production, but we can't deny that we can't produce without grinding. If you say the advantages and disadvantages, there are mill production efficiency and energy saving. The non-grinding production is more stable, which explains why the modified asphalt has a softening point attenuation. After SBS is over-grinded, the specific surface area is increased, the surface development and degradation rate are faster, and the early high softening point is exhibited. However, as the modifier further develops and degrades, it eventually matches its true softening point and attenuates. This phenomenon does not occur in millless production because it takes a long and long development time, and the softening point is a reflection of the true state. Therefore, as the owner of the unit, it is a big deal to mention that there is no grinding production. It was just on-site production, and I didn’t wait so long. Fourth, the modifier content and indicators First of all, we know that the existing asphalt index system and road performance have little to do with. Different asphalts, different modifier types, modifier content and indicators also have different relationships, and it is not certain that below a certain level, the indicator requirements are not met. Therefore, good design documents require modifier content in addition to the index requirements. Since the content is not required, as long as the indicators are qualified, it is justified.

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