Brief introduction of asphalt concrete mixing station

27 Jul 2019 09:00
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1.
Batch asphalt mixing station composition
Intermittent asphalt mixing station mainly consists of cold silo, cold material distribution system, cold material conveying system, combustion drying system, ventilation dust removal system, hot material hoist, vibrating screen, hot silo, powder conveying system and asphalt conveying. System, metering system, mixing tank, control system, finished material conveying and storage system, asphalt heating and insulation system, etc.

2. Discussion on the chain bin phenomenon of asphalt commercial concrete mixing station
2.
1 First introduce the structure and principle of the vibrating screen.

(ACP4000 forced intermittent asphalt commercial concrete mixing plant for example), the composition mainly includes: RetentionRubber, SupportTube, as well as vibrating screen drive system and supporting electrical components
The working principle is as follows: the hot aggregate is sent to the vibrating screen through the hot aggregate hoist, and the hot aggregate is vibrated and sieved through the vibrating screen. The stones of different specifications pass through the screen into the corresponding hot aggregate silos, which cannot pass through the screen. The super-size of the net enters the overflow bin.

2.
2 Introduction to the structure and principle of the hot silo
The composition mainly includes: SampleChute, HotStoneBinDoorOperatingCylinders, as well as the opening and closing of each hot silo, the positioner of each silo of the brass tube, the matching pneumatic components and the original electrical components.

The working principle is as follows: the hot silo is to classify and store the qualified hot aggregates, and convert them into weight according to the proportion set by the grading. Through the system control, after the coarse matching and the fine matching, the heat is opened and the heat is opened. The aggregate is said to have reached the right quality, stop the ingredients, and then enter the mixing pot, start the ingredients in the next pot, and continue to cycle.

2.
3 Introduction The reasons and treatment methods of the asphalt concrete concrete mixing station are mainly including the following aspects:
2.
3.
1 The phenomenon of string binning is caused by the leakage of the partition between the respective hot silos.

The separation of each hot silo is separated by iron plates. The iron plates have a certain use time. They have a certain wear resistance. After a long time of stone rubbing, the thickness of the iron plate is gradually thinned, just like dripping water. The iron plate is worn through, and more stones between adjacent hot silos will enter the less hot bin from the leaking place, thereby generating a string bin.

2.
3.
2 The breakage of various stones is caused by the breakage of various sieves of different specifications.

Various kinds of sieves of garbage boilers are made of steel bars of different diameters. Their quality is different, and their toughness, rigidity and wear resistance will be different. After a certain stage of use, the steel bars of the sieve will be gradually thinned and straightened. The diameter of the mesh hole becomes large, and the large stone that cannot pass this size will pass through the place where the diameter of the mesh hole becomes larger and enters the stone which has been sieved by the original sieve through the diameter without change, thereby generating a string bin phenomenon.

The solution is to re-weld the damaged area with wear-resistant steel.

2.
3.
3 The phenomenon of the binning caused by the poor blocking effect of the front and rear baffles of each layer of sieve.

The gap between the front and rear baffles and the side spacers of the vibrating screen is too large, causing stones that exceed the size of the screen in contact with the baffles to leak into their corresponding hot bins.

Thus, the phenomenon of the binning occurs.

To solve the problem is to deal with the front and rear baffle blocking effect, as long as there is a gap to fill all the places.

2.
3.
4Because the tension of each screen is not good and the contact between the sides is not tight, the gap between the screen and the side is caused by the vibration of the screen.

The isolated contact plates of each layer of the vibrating screen are arranged in a certain arc from top to bottom.

Therefore, if the sieve is to be in close contact with it, the tensioning tension must reach a certain degree to ensure that the screen will not have a gap with the side when the screen is vibrated, otherwise the string warehouse phenomenon will occur.

The solution is to adjust the tension of each screen to a suitable degree. Generally, the tension spring is tightened to the original length, and the toughness can be appropriately adjusted according to the length of the screen.

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3.
5 The plugging of the overflow pipe connected by the vibrating screen and the overflow bin causes the binning phenomenon.

When the overflow pipe connected to the vibrating screen and the overflow bin is blocked, the overflowing stones will not enter the overflow bin through the overflow pipe, and when the flash is more and more, the hot material from the flash will be blocked. In the warehouse, more than the flash will enter the adjacent hot bin with no flash or dissatisfaction, resulting in a binning phenomenon.

The solution is to take out the blockage that is blocked in the overflow pipe and dredge the overflow pipe so that the flash can be smoothly discharged into the overflow bin.

3.
Quality control of asphalt commercial concrete
The quality of asphalt commercial concrete is mainly reflected in the two indexes of stability and flow value. It reflects the high temperature stability and deformation resistance of asphalt commercial concrete, and is closely related to the quality of raw materials and the control of production process.

Therefore, the quality of the mixture should be controlled from the following aspects.

3.
1 Control of raw material quality
The raw materials of asphalt commercial concrete mainly include: coarse aggregate, fine aggregate, mineral powder, asphalt and so on.

3.
1.
1 coarse aggregate coarse aggregate refers to particle size greater than 2.
36mm gravel.

Forming a frame in asphalt commercial concrete to maintain stability.

Therefore its mechanical properties should meet the requirements and have a good shape.

The needle-like content is low, no weathering, no impurities, and the surface roughness has high internal friction.

3.
1.
2 fine aggregates Fine aggregate means the particle size is 0.
075~2.
Large sand, stone chips, etc. between 36.

It should be clean, free of weathering, free of impurities, and have suitable particle composition and possible angularities to increase the interlocking effect between the particles and reduce the inter-aggregate porosity.

3.
1.
3 Asphalt Asphalt should check whether the indicators such as penetration, ductility and softening point meet the technical requirements of transportation petroleum asphalt before use.

In the choice of asphalt, the high temperature stability and low temperature crack resistance of the asphalt pavement should be considered.

Due to the higher marking of asphalt, the greater the penetration, the lower the consistency. Therefore, different types of asphalt should be selected according to the different pavement levels. The surface layer should be made of thinner asphalt to improve the crack resistance of the surface layer. Thicker asphalt to improve rutting resistance.

The wax content should be controlled below 3%, and the wax content is too high, which has an effect on the high temperature stability and low temperature crack resistance of the road surface, and also affects the adhesion of the asphalt.

3.
1.
4 Filler The role of the filler is to form an asphalt cement with the asphalt to increase the adhesion of the asphalt mixture.

The correctness of the filler formulation is directly related to the free asphalt in the asphalt mixture.

If free asphalt is present, the adhesion of the asphalt mixture will be reduced and oil flooding will occur.

The filler should meet the fineness requirements and no impurities.

In the case of using bagged ore powder, there should be storage space, rainproof, moisture-proof, and ventilated and dry to prevent the mineral powder from getting wet.

Mineral powder that has been agglomerated and damp is strictly unusable.

Sometimes in order to improve the adhesion of asphalt, it is necessary to add additives such as slaked lime, and the slaked lime must be thoroughly eliminated, and the fineness meets the requirements.

Otherwise it will have the opposite effect, affecting the quality of the asphalt mixture.

3.
2 control of the primary distribution of cold materials
The primary material of the cold material is calculated according to the requirements of the mixing ratio, and the rotation speed of the batching motor of each cold storage bin and the height of the material door are calculated to determine the conveying amount of various materials to meet the needs of continuous production of the mixing station.

If the primary material of the cold material is not accurate, there will be a phenomenon of waiting and flashing, which will affect the productivity of the mixing station and the quality of the mixture.

The tester should keep abreast of the feeding situation of the material yard, sample and screen in time, and analyze relevant data.

The primary mix is ​​adjusted according to different raw materials to ensure the stability and continuity of the mixing production.

3.
3 weighing measurement control
The aggregate after heating and drying is sieved by a vibrating sieve and then enters a hot silo of different particle sizes.

The tester must sample and screen the aggregate after the sieve is sieved to determine the proportion of the materials of different sizes in each hot silo.

The hot silo screening must be carried out when the primary cooling material is stable to ensure the accuracy of the screening test.

The production mix ratio grading curve obtained by the screening test analysis should be within the allowable range of the target mix ratio grading curve and meet the technical standards.

3.
4 temperature control
For the batch asphalt mixing station, the asphalt heating temperature is controlled at 150-170 degrees, the aggregate temperature is 10-20 degrees higher than the asphalt temperature, and the factory temperature of the mixture is 140-165 degrees.

If the temperature is not enough, the flower will appear, and if the temperature is too high, the asphalt will burn.

The factory temperature of asphalt mixture directly affects the quality of paving and rolling.

The temperature of the mixture should be checked at any time during the production process and the operator should be notified to adjust it according to the actual situation.

3.
5 mixing of the mixture
After the mixture is uniformly mixed, all the mineral particles are required to be covered by the asphalt, without uneven wrapping, no white matter, no agglomeration or segregation.

Usually, the mixing time of the asphalt mixture is dry mixing for 5 seconds and wet mixing for 45 seconds.

The SMA mix requires dry mixing for 5 seconds and wet mixing for not less than 60 seconds.

It is not possible to reduce the mixing time at will in order to increase productivity.

The mixing blades and lining plates in the mixing tank should be replaced in time after wear to ensure the orderly flow and uniform mixing of the mixture in the mixing tank to improve the mixing quality of the mixture.

3.
6 monitoring of finished materials
The quality inspectors shall inspect each batch of finished materials, and the materials, flowers, segregation, insufficient temperature or over temperature shall be discarded.

The problem is found and feedback to the operator in time for targeted adjustment processing.

The tester conducts random sampling on the mixture every day, conducts experimental analysis according to the test procedure, and feeds the experimental data back to the operator, and finds the problem in time for analysis and resolution.

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