JPH0548807B2 - - Google Patents

Description

Detailed Description of the Invention A. Purpose of the Invention (Field of Industrial Application) In recent years, in an asphalt plant set up outside a city, a small amount of asphalt (primary asphalt) and aggregate are mixed while being heated to produce heated asphalt mixture. The primary mixed material is made and stored in a storage facility located within the city while being heated or kept warm. When constructing pavement work, the stored mixed material is taken out and further mixed with stone powder and asphalt (secondary mixed material). An asphalt mixture supply method called the satellite method, in which asphalt (asphalt) is added and mixed and transported to a construction site for use, has come into use.

The present invention is an invention that can be used to effectively operate the apparatus of this method.

(Prior art) In the satellite-type asphalt mixture supply method, in asphalt plants set up outside cities, aggregates of appropriate particle size are mixed and
Heat to 180°C and add 1-3% (wt%) of the aggregate.
same as below. ) of primary asphalt is added and mixed to create a primary mixed material.

At this time, if the mixed primary asphalt is left at high temperatures for a long period of time, it will deteriorate and solidify, so while the primary mixed material is being filled into a silo at the storage facility and stored, the outlet of the silo is blocked and the primary mixed material is taken out. This has the disadvantage of inhibiting the

FIG. 2 shows an outline of an apparatus for carrying out such a conventional asphalt mixture supply method. A mixed material is prepared, loaded onto a transport vehicle 5 (for example, a dump truck), and stored in silos 6a and 6b provided with a heating device or a heat insulating device in a storage area 6 according to particle size.

At the time of use, the primary mixed material with the required particle size is taken out, the remaining secondary asphalt 3b of the total amount used is added using the pump 7, and the mixture is stirred by the stirrer 9 in the stirring chamber 8 to form an asphalt mixture, which is transported to the paving construction site by the transport vehicle 10. Construction.

If the amount of primary asphalt used in asphalt plant 1 is less than 1% of the aggregate, sufficient mixing will not be achieved and the effect of suppressing the generation of dust from the aggregate will be insufficient, so it will not be possible to use the primary asphalt inside the plant or on transport vehicles. This is not possible as a large amount of dust will be scattered during transportation. If it exceeds 3%, the adverse effects of deterioration will increase, the phenomenon of blocking the silo outlet will become stronger, and furthermore, sufficient properties as a mixture will not be ensured.

Therefore, the amount of primary asphalt mixed with the aggregate at the plant is set at 1 to 3%, but since this asphalt is still deteriorating even after being taken out of the silo, in order to fully demonstrate the performance of the mixture, It is necessary to add improving materials.

For example, reduce the total asphalt mixture to 6% of the mixture.
If the amount of primary asphalt mixed in plant 1 is 1.5%, then the amount of secondary asphalt mixed with the primary mixed material taken out from storage is 4.5%.
%, but in order to fully demonstrate its performance as an asphalt mixture, it has already deteriorated.
It is necessary to add a modifier to improve the 1.5% asphalt.

(Problem to be solved by the invention) However, it is wasteful to add improving materials as the primary asphalt, which is mixed into the primary mixed material with the main purpose of suppressing aggregate dust, deteriorates. Even if it does, it is desirable that this amount be small, and furthermore, it is desirable that the asphalt is resistant to deterioration.

B. Structure of the invention (means for solving the problem) This invention uses primary asphalt mixed with aggregate in an asphalt plant by foaming it with steam to which a foaming sustaining surfactant is added, The above-mentioned problems are solved by significantly reducing the amount of asphalt used in the primary mixture, and by covering the surface of aggregate particles with a thin asphalt layer to suppress the scattering of stone powder.

(Function) Foamed asphalt is produced, for example, by blowing water vapor into an outflow pipe of molten asphalt to mix it and inject it. When asphalt is foamed in this way, the volume increases by a factor of 5 to 10.

The effect of asphalt on suppressing aggregate dust is thought to be due to asphalt penetrating between aggregate particles and bonding them together. This permeation effect increases as the volume of asphalt increases, so if the volume of asphalt is increased by foaming, the effect of permeating asphalt between aggregate particles becomes stronger, and the amount of asphalt used increases accordingly. can be reduced.

The foaming duration required for the foamed asphalt to penetrate between the aggregate particles through mixing is generally about 5 to 10 seconds, but depending on the particle size of the aggregate, more time may be required. do. Therefore, when steam is mixed into the surfactant, the foaming duration of the asphalt is extended, and the effect of the asphalt permeating between the particles of the aggregate can be further improved.

Figure 1 shows an outline of a device that foams primary asphalt and mixes it with a primary mixed material.The primary asphalt 3a is passed through a pump 7 to a mixing section in the lower part of the plant through a pipe in which steam mixed with a surfactant is supplied from a boiler 11. is blown into the foam, foamed, and placed in the stirring section.

Since the volume of foamed asphalt is 5 to 10 times larger than that of normal asphalt, it is sufficient to produce a good primary mixed material even at a mixing ratio of less than 1%, which was conventionally considered inappropriate. If the amount of primary asphalt is too small even if it is foamed, the dust suppression effect will be insufficient, so the lower limit of the mixing ratio is 0.3.
It will be about %.

In addition, since primary asphalt permeates between aggregate particles in a foamed state, the thickness of the asphalt that binds aggregate particles is small and forms a thin film, but it does not have the effect of lightly adhering particles and preventing dust from scattering. It is large enough, and mixes well with stone powder.
Produces asphalt that is similar to natural asphalt and does not easily deteriorate. Further, even if this asphalt deteriorates, its effect of blocking the air outlet of the storage area is weak.

For example, if the expansion rate of foamed asphalt is 10 times, 0.3% foamed asphalt has almost the same volume as conventional 3% asphalt, and can have the same effect on suppressing aggregate dust. When a total of 5% asphalt is mixed with
Assuming that an effective asphalt mixture is obtained with 4.7% asphalt, and 0.3% asphalt has a 50% decrease in performance due to deterioration, the total
4.85% asphalt will work effectively.

Similarly, if a total amount of 5% asphalt is used, and if 3% primary asphalt is used as the primary mixture, the performance will decrease by 50%. The total effective amount is 3.5%. This also shows that even if the asphalt deterioration due to storage of the primary mixed material is the same, there will be a large difference in overall deterioration.

C. Effects of the invention (1) The amount of asphalt used in the primary mixture can be significantly reduced.

(2) The asphalt used as the primary mixture deteriorates in the silo of the storage facility, but foamed asphalt has a property that it does not deteriorate easily, and since the amount of asphalt is small, even if it deteriorates, there will be no problem of blocking the silo outlet.

(3) The amount of secondary asphalt mixed at the end can also be reduced by that amount, since the amount to compensate for the deteriorated amount of primary asphalt is small.

(4) By mixing a surfactant into the steam,
By extending the foaming duration of asphalt, it is possible to improve the permeation of asphalt between aggregate particles.

[Brief explanation of the drawing]

FIG. 1 is a side view schematically showing an apparatus for foaming primary asphalt and supplying it to an asphalt plant in the present invention, and FIG. 2 is a side view schematically showing a conventional asphalt mixture supply apparatus. 1: Asphalt plant, 2: Aggregate, 3a:
Primary asphalt, 3b: Secondary asphalt,
4: Stirrer, 5: Transport vehicle, 6: Storage area, 6a, 6
b: Silo, 7: Pump, 8: Stirring chamber, 9: Stirrer, 10: Transport vehicle, 11: Boiler.

Claims (1)

[Claims] 1. In an asphalt plant, a small amount of heated primary asphalt is mixed with aggregate to create a primary mixed material, which is stored in a storage facility under heating or heat retention, and when used, the primary mixed material taken out from the storage facility is mixed with a secondary material. In the asphalt mixture supply method in which asphalt is added and mixed to form a secondary mixture, the primary asphalt is 0.3% by weight or more and less than 1% by weight of the primary mixed material, and the foam sustaining surfactant is added in an amount of 5% by weight or less of the primary asphalt. A method for supplying an asphalt mixture, characterized in that the asphalt mixture is mixed into a primary mixture material as foamed asphalt using mixed steam.