JPH01141845A - Method and apparatus for cooling concrete aggregate - Google Patents

Abstract

PURPOSE:To improve the quality of concrete after casing by charging the (fine) aggregate contg. specified amount of water in a vacuum vessel provided with plural evacuation chambers and evacuating the vessel through the cambers. CONSTITUTION:The (fine) aggregate S of about 15% surface water content is charged through an aggregate supply vacuum-proof valve 1 to a longitudinal high tower type vacuum vessel 3, and required plural number of evacuation chambers 5 having evacuating openings 4 is longitudinally provided on the outer periphery of the vacuum vessel 3 from the upper part to the lower part by required stages so as to overhang to the outside, and evacuating pipes are connected to the upper side of the chamber to be evacuated by a vacuum pump 8, and then water vapor evacuated and sucked is condensed on the surface of a cold trap 7 into water by the trap 7 and a brine chiller 9, and the water is discharged to the outside through a check valve 10 and a drain pump 11. The (fine) aggregate S is cooled by the evaporation of the surface water.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for cooling concrete aggregates, particularly fine aggregates, for concrete structures with large cross sections such as dams and bridge piers.

[Prior art]

Traditionally, Portland cement has been mixed with aggregates such as sand and gravel and used as concrete in civil engineering, construction work, and the manufacture of concrete products.

Among them, concrete using a cement called early-early strength Portland cement has a relatively high early-stage strength and has been used mainly for construction work that needs to be completed in a hurry.
Since the amounts of 3S, C3A, etc. are large, a large amount of heat of hydration is generated after kneading, and its removal is difficult, resulting in problems such as the occurrence of cracks and poor long-term strength.

Therefore, when pouring concrete for concrete structures with large cross sections such as dams and bridge piers, C3S, C3
Moderate heat Portland cement and blast furnace cement, which have less A and more C2S, have been developed, and efforts have been made to reduce the accumulation of hydration heat inside concrete.

However, since it is theoretically impossible to ensure that the heat of hydration is completely eliminated, various methods are used, such as choosing a time when the environmental temperature is low to pour concrete, or removing the heat of hydration accumulated in the concrete. Therefore, methods such as burying cooling pipes in concrete have been taken.

As mentioned above, various methods have been tried to remove the heat of hydration after mixing cement, but in recent years, in a society where economic efficiency is particularly important, it is necessary to use a period when the environmental temperature is low. By waiting or by burying cooling pipes, it is not economically possible to pour concrete at any time or place, which is extremely uneconomical.
In addition, there was a problem in that there could be many losses in terms of time.

On the other hand, in a method of cooling concrete aggregates in which concrete aggregates are cooled in advance before mixing and pouring concrete materials, a vacuum is created in the atmosphere in which aggregates containing water on the surface are stored. There has also been an invention disclosed in JP-A-57-188317 relating to a method and apparatus for cooling concrete aggregate, which is characterized in that the aggregate is cooled by latent heat of evaporation due to evaporation.

In such concrete aggregate cooling equipment, the amount of aggregate to be cooled is usually several tens of cubic meters, and in order to cool such an amount, a vertically long It has to be cylindrical.

For example, to cool 70 rrr of aggregate at once, two containers with a diameter of 2 m and a height of 1 m are required.If the aggregate is placed in these containers and evacuated, the water attached to the aggregate will evaporate. However, the latent heat of vaporization for self-evaporation is taken away and the aggregate is cooled.

However, as the tower length becomes longer as mentioned above, the effect of the degree of vacuum becomes less effective the lower it goes, and the self-evaporated water is obstructed by the aggregates and cannot be exhausted smoothly. However, there is a problem in that a uniform vacuum state cannot be obtained at the top and bottom of the tower, and a difference in cooling temperature occurs between the top and bottom, making it difficult to achieve uniform cooling as expected.

This is because the vacuum is evacuated from one place at the top of the tower, and we focused on the fact that if the degree of vacuum is applied evenly to all the aggregates, the entire tower storing aggregates can be cooled uniformly. What has been accomplished is the present invention.

On the other hand, when evacuating the inside of the vertically cylindrical vacuum tower as described above, if the exhaust port is provided on the outer periphery of the vacuum tower,
There is a possibility that the effect of vacuum evacuation will not reach the center of the vacuum tower sufficiently and uniform cooling will not be possible.Also, if vacuum evacuation is performed from those exhaust ports, there will be damage caused by aggregates etc. at the exhaust ports. There is a risk of clogging or aggregates being sucked into the exhaust port.

Furthermore, if aggregates, etc. pile up in a compacted state within the vacuum tower, it may become impossible to discharge if they freeze completely, and the discharge port may become clogged if they partially freeze. , solutions to these problems are desired.

[Purpose of the invention]

The present invention has been made in order to solve the above-mentioned conventional problems and meet the demands, and enables concrete to be poured at any time or place, and also reduces the temperature rise of concrete due to heat of hydration. The object of the present invention is to provide a method and a cooling device for cooling aggregate for concrete, which can keep the temperature within a certain range and can uniformly and efficiently cool and discharge the aggregate.

[Structure of the invention]

In order to achieve the above object, the method of cooling aggregate for concrete according to the present invention is to cool fine aggregate, coarse aggregate, or a mixture of these before mixing concrete in a vacuum chamber at a predetermined moisture content. The aggregate supply port and the aggregate discharge valve are closed while the aggregate is stored in the chamber, and the aggregate is passed through a vacuum exhaust port provided in multiple stages in the vertical direction of this vacuum chamber, or at least near the aggregate discharge valve.
This method is characterized by lowering the temperature of the aggregate by evacuating the vacuum chamber and depriving the aggregate of the heat of vaporization of the water that evaporates at that time. As mentioned above, a vacuum chamber is installed outside the outer periphery of the vacuum chamber, which can be loaded and stored at a predetermined moisture content in a vacuum chamber, and which has an aggregate supply valve and an aggregate exhaust valve, and is capable of evacuation from the vacuum chamber. It is constructed by arranging exhaust chambers in multiple stages or at least in the vicinity of the aggregate discharge valve.

As mentioned above, the aggregate is pre-cooled before being mixed with concrete, and then mixed with cement. By suppressing the temperature rise of the concrete due to the heat of hydration and keeping the temperature at an average of around 20℃, for example, good quality concrete can be produced. Pouring will be done.

Furthermore, in the concrete aggregate cooling device having the above structure, a cylindrical body having a large number of holes is installed vertically or horizontally in the vacuum chamber so that the vacuum chamber can be discharged. It is preferable that one or more rods be inserted, so that the aggregate at the center of the vacuum chamber is sufficiently vacuumed and the cooling effect is exerted, and the vacuum evacuation chamber and the cylindrical body are , or any of these,
If a filter that only allows gas to pass through is installed, the vacuum evacuation chamber and the aggregates in the cylindrical body will not be clogged or sucked in, and smooth vacuum evacuation will occur.Furthermore, An umbrella-shaped member capable of forming a gap between the aggregates in the vacuum chamber is
It is desirable to provide one or more in the vacuum chamber, thereby preventing the aggregate from being unable to be discharged due to compaction of the aggregates.

〔Example〕

Embodiments of the concrete aggregate cooling method of the present invention and a cooling device to which the method is applied will be described below with reference to the drawings. 2 is a sectional view of the arrangement of the device; FIG. 3 is a sectional view of the arrangement of Embodiment 3; FIG. 4 is a sectional view taken along the line A-A in FIG. 3; FIG. 4 is a sectional view of the arrangement of Example 4, in which the same parts in each of the above-mentioned Examples are indicated by the same part numbers.

First, Example 1 in FIG. 1 shows a vacuum chamber 3 in the form of a vertically long base, in which aggregate S having a surface moisture of about 15% is passed through a hopper (not shown) into vacuum-resistant aggregate. Aggregates can be fed into this vacuum tank 3 through a supply valve 1, and a vacuum-resistant aggregate discharge valve 2 is provided at the bottom of the vacuum tank 3.

Next, the evacuation chamber 5 is placed on the circumference of the vacuum chamber 3 in such a manner that it extends outward from the tower wall by a plurality of required stages from the top to the bottom of the outer periphery of the vacuum chamber 3 in the vertical direction. A vacuum exhaust pipe 6 is connected to the upper side of the vacuum exhaust chamber 5.

In this case, if the tower wall is made long so as to fit into the evacuation chamber 5 a little so that the evacuation chamber 5 is not filled with aggregate S, an evacuation window 4 can be formed in the evacuation chamber 5 on the circumference of the vacuum chamber 3. is formed.

In general, aggregate S for concrete, such as sand or pebbles, does not have natural flow deformability. Therefore, even when the aggregate S is filled, the evacuation chamber 5 remains empty.

If vacuum evacuation is not performed in this way, each evacuation chamber 5 will affect the upper and lower evacuation chambers 5 in the vertical direction.
up to the middle of a certain position, and the pitch of the evacuation chamber 5 is small (the more easily and evenly the vacuum can be applied to the aggregate S, and the longer the length of the vacuum chamber 3 is The aggregate S can be cooled uniformly regardless of the temperature.

The water vapor produced by evacuating the aggregate S passes through the vacuum exhaust pipe 6 and reaches the cold trap 7, where it condenses on the surface of the cold trap 7 cooled by the brine chiller 9 and becomes water. 10, and is discharged to the outside through a drain discharge pump 11.

Here, 8 in the figure is a vacuum pump.

It should be noted that before the aggregate S cooled in the above embodiment is supplied into the vacuum chamber 3 via a hopper or the like, its surface is already coated with a predetermined moisture content, for example 1.
It contains about 5% moisture, but this moisture is removed from the vacuum chamber 3.
The water may be applied to the aggregate S by an appropriate means such as a water spray nozzle.

Further, if the gas discharge is sufficient, it is sufficient to provide the evacuation chamber 5 only in the vicinity of the discharge port of the vacuum chamber 3.

Next, Embodiment 2 shown in FIG. 2 has almost the same structure and function as Embodiment 1, but the vacuum chamber 3 has a perforated pipe-like cylinder having a large number of holes 20 in the longitudinal direction at the center. shape body 2
1 is inserted, and the inside of the vacuum chamber 3 is evacuated with an evacuation pipe 6. Furthermore, the exhaust window 4 of each evacuation chamber 5 on the outer periphery of the vacuum chamber 3, and the exhaust window 4 of the cylindrical body 21 are inserted. A filter 22 that allows only gas to pass through is provided in each portion of the guard dog 2o.

Note that the filter 22 may be provided only on either the evacuation chamber 5 side or the hole 2o side of the cylindrical body 21.

By inserting the cylindrical body 21 as described above, the aggregate S in the center of the vacuum chamber 3 can be sufficiently cooled by vacuum evacuation. Since the inside of the body 21 can be completely prevented from being clogged with aggregates S, etc., and the suction of aggregates S can also be completely prevented, smooth vacuum evacuation can be performed.

In addition, in the third embodiment shown in FIGS. 3 and 4, this vacuum chamber 3
A large number of cylindrical bodies 21A in the form of perforated pipes having a large number of holes 20 are inserted in the upper and lower sides of the body, and each evacuation pipe 6 performs evacuation. It has the same function and effect as the cylindrical body 21.

Furthermore, in the fourth embodiment shown in FIG. 5, a large number of umbrella-shaped members 23 are used in which a large number of voids P are formed between the aggregates S in the vacuum chamber 3, similar to the first embodiment shown in FIG. This is installed in the vacuum chamber 3, which prevents the aggregate S from becoming impossible to discharge when frozen or clogging the discharge port due to the compaction of the aggregate S, and ensures smooth discharge of the aggregate S. can do.

Note that this umbrella-shaped member 23 may be one or more depending on the size and shape of the vacuum chamber 3, and is not particularly limited.

Further, in this fourth embodiment, a filter 22 is provided in the exhaust window of each vacuum exhaust chamber 5 to allow only gas to pass through.

〔Effect of the invention〕

As explained above, if a device for cooling concrete aggregate using the cooling method of the present invention is installed near the concrete placement site, good concrete placement without cranking can be achieved at any time or place. This method has the effect that the temperature rise of concrete due to the heat of hydration of concrete can be easily kept within a certain range.

In particular, in the present invention, the aggregate to be cooled can be easily and uniformly and efficiently cooled from the upper part to the lower part when the aggregate to be cooled is put and stored in a stationary vacuum tank with a base shape that does not take up much space. The cooling temperature within the vacuum chamber can be easily controlled, and as a result, the quality of concrete after pouring can be improved.

Further, if the degree of vacuum is sufficient, the evacuation chamber may be provided only in the vicinity of the aggregate discharge valve of the vacuum chamber.

Furthermore, the apparatus of the present invention has the advantage that it requires less floor space, and since the aggregate in the vacuum chamber falls by gravity, no power is required to carry out the aggregate.

Furthermore, if a cylindrical body is inserted into the vacuum chamber and the vacuum is discharged through the cylindrical body, as in the apparatus of the present invention, the aggregate in the center of the vacuum chamber will be sufficiently cooled, and the The advantage is that the aggregate inside is cooled evenly from the center to the surrounding area, allowing for homogeneous concrete placement.

Furthermore, by installing a filter in the vacuum chamber and the cylindrical body, troubles such as aggregate clogging and suction are completely prevented, and smooth vacuum discharge is achieved. Since voids are formed in the tank, problems such as inability to discharge aggregates due to compaction of aggregates, especially when frozen, and aggregates clogging at the discharge port are eliminated, and aggregates can be discharged smoothly. There is also the advantage of being wet.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a cross-sectional view of the arrangement of a cooling device for concrete aggregate in Embodiment 1 of the present invention, Fig. 2 is a sectional view of the arrangement of a cooling device for concrete aggregate in Embodiment 2, and Fig. 3 is a sectional view of the arrangement of a cooling device for concrete aggregate in Embodiment 3 of the present invention. FIG. 4 is a cross-sectional view taken along the line A-A in FIG. 3, and FIG. 5 is a cross-sectional view of the layout of Example 4. DESCRIPTION OF SYMBOLS 1... Aggregate supply valve, 2... Aggregate discharge valve, 3... Vacuum chamber, 5... Vacuum exhaust chamber, 6... Vacuum exhaust pipe, 8...
...Vacuum pump, 20...Hole, 21.21A...Cylindrical body, 22...Filter, P...Gap, S...
aggregate. Agent Patent Attorney Nobuo Ogawa −

Claims (1)

[Claims] 1. While the aggregate before mixing concrete is stored in a vacuum tank at a predetermined moisture content, gas is discharged from at least an exhaust port provided near the aggregate discharge port. A method for cooling aggregates for concrete, in which the temperature of the aggregate is lowered by sucking and discharging it to the outside to create a vacuum in the vacuum chamber, and removing the heat of vaporization of the water that evaporates from the aggregate. 2. At least in the vicinity of the aggregate discharge valve on the outer periphery of a vacuum tank that can store aggregate at a predetermined moisture content before mixing concrete and has an aggregate supply valve and an aggregate discharge valve. A concrete aggregate cooling device equipped with a vacuum evacuation chamber that can perform vacuum evacuation. 3. The concrete aggregate cooling device according to claim 2, wherein a cylindrical body capable of evacuation of the vacuum chamber having an evacuation chamber arranged around the outer periphery is inserted into the vacuum chamber. 4. Cooling of aggregate for concrete according to claim 2 or 3, wherein a filter that allows only gas to pass is installed in the vacuum evacuation chamber and/or the cylindrical body capable of evacuation within the vacuum chamber. Device. 5. The aggregate for concrete according to claim 2, 3 or 4, wherein an umbrella-shaped member capable of forming a gap between the aggregates in the vacuum tank is disposed in the vacuum tank. Cooling system.