JPH0767690B2 - Crack-prevention concrete cooling system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial field of application" The present invention is used, for example, when performing a pre-cooling method in which the concrete temperature is lowered before pouring in order to prevent cracking of mass concrete members. The present invention relates to an aggregate cooling device.

"Conventional technology" When constructing so-called mass concrete members used for dams, bridge piers, nuclear reactor facilities, etc., because the temperature stress caused by the heat of hydration of cement easily causes cracks in these mass concrete members, Preventing this is an important issue in quality control of concrete.

In order to prevent cracking of the mass concrete member, the pre-cooling method is used to suppress the change amount and temperature difference of the concrete temperature in the member due to the heat of hydration of cement by lowering the kneading temperature of the concrete. The so-called construction method and a method of increasing resistance to cracking by increasing the strength of concrete by making the temperature rise due to heat of hydration the same.

In the pre-cooling method, each constituent material of concrete is pre-cooled with cold water, cold air, or ice before mixing, and the cooled material is mixed to lower the kneading temperature of concrete. It is a construction method that reduces cracks due to temperature stress by placing the concrete.

In recent years, by replacing the mixing water of concrete with fine particles of ice, it is possible to evenly disperse each concrete constituent material and increase the concrete strength, and the latent heat of ice allows the concrete to be kneaded in the same way as the pre-cooling. Construction methods that lower the temperature have been proposed and implemented.

[Problems to be Solved by the Invention] However, the conventional methods for preventing the cracking of mass concrete have the following problems. That is, in the pre-cooling method, cold water, cold air, or ice is used as a cooling medium for cooling each constituent material of concrete, but when cold water is used as the cooling medium, the temperature of the cooling medium itself is about 0 ° C. Can only go down by. Therefore, when increasing the decrease amount of the concrete kneading temperature, it may not be possible to sufficiently cool each concrete constituent material to a predetermined temperature.

Also, when the kneading water is replaced with ice, the ice may remain in the concrete after kneading, or the kneading time may be long, depending on the size and amount of the ice to be used, There is a limit to the amount used. Therefore,
As in the case of using cold water, the kneading temperature of concrete may not be lowered sufficiently.

This invention further develops the idea of replacing the mixing water of concrete with fine particles of ice, and by simultaneously realizing a decrease in the mixing temperature of concrete and an increase in concrete strength, cracking of concrete has hitherto been achieved. It is intended to provide an aggregate manufacturing apparatus for realizing concrete that can be reduced more than the method of construction and that has a constant effect even under severe construction conditions such as autumn-winter-spring.

"Means for Solving Problems" In order to solve the above problems, the present invention is one in which an aggregate, which is a constituent material of concrete, is cooled by liquefied gas to form an ice layer on its surface. Which is a freezing duct into which liquefied gas is blown, a transfer body that transfers the aggregate to be cooled and passes through the freezing duct, and a cooling that is introduced into the transfer body by vibrating the transfer body. A vibration mechanism for vibrating the target aggregate and a cooling source device for cooling the aggregate by blowing liquefied gas into the freezing duct and spraying the aggregate transferred by the transfer body to freeze the surface water of the aggregate. And a pre-cooling device for pre-cooling the liquefied gas blown to the aggregate by the cooling source device by collecting the liquefied gas from the inside of the freezing duct and blowing it to the aggregate before cooling put into the transfer body. It is characterized by being provided.

[Operation] In the present invention, while pre-cooling the aggregate to be cooled and then transferring it by the transfer body and passing it through the freezing duct, a liquefied gas such as liquefied nitrogen or liquefied helium is introduced into the freezing duct by the cooling source device. By blowing, the aggregate is rapidly cooled below zero, and the surface water held by the precooled aggregate is frozen to form an ice layer on the surface of the aggregate. At this time, the pre-cooled aggregate is vibrated by the vibrating mechanism to jump,
Since it is cooled to 0 ° C or less while rotating, all the aggregates are cooled uniformly and in a sufficiently short time to form an ice layer on the entire surface without fail, and the ice layer formed on each aggregate. It is also prevented that the aggregates are fused and the aggregates are attached to each other. Moreover, since the liquefied gas is collected by the pre-cooling device and sprayed on the aggregate before cooling, the aggregate to be cooled is pre-cooled, so that the liquefied gas can be reasonably effectively used without waste and excellent cooling efficiency can be achieved in a short time. Can be obtained at.

[Examples] Examples of the present invention will be described below with reference to the drawings.

1 and 2 are views showing an aggregate cooling device according to an embodiment of the present invention. This cooling device cools the sand as fine aggregate to below 0 ° C with liquefied nitrogen and freezes the surface water of the sand, thereby removing the frozen sand (fine aggregate) with an ice layer formed on the surface. This is a device for manufacturing, and in FIGS. 1 and 2, reference numeral A is a vibration shooter installed on a base G. The vibration shooter A includes a transfer body 1 having a substantially U-shaped cross section for transferring sand 4, a vibration mechanism 2 provided on a base G and supporting the transfer body 1 from below, and springs 3, 3 ,. Is roughly configured by. The transfer body 1 is entirely tilted so that its starting end is slightly upward, and is further vibrated in the vertical direction by the vibrating mechanism 2 and the springs 3, 3, .... The silos 5 and 6 for storing the sand 4 are arranged above the start end side and below the end end of the transfer body 1, respectively. At the bottom of these silos 5 and 6,
Openable lids 7 and 8 are provided. Further, of these silos 5 and 6, a lid 9 is provided at the upper end of the silo 6 located on the terminal side of the transfer body 1 to enhance the cold insulation effect. The lid 9 is opened by the weight of the sand 4 and automatically closed when the sand 4 is not supplied.
For example, it is preferably formed of hard rubber or the like. In addition,
The silo 6 is preferably a silo whose heat insulating effect is improved by, for example, applying a heat insulating material to its wall surface or the like.

The transfer body 1 is provided with a cylindrical freezing duct 16 that covers the whole of the transfer body 1 except for the start and end portions thereof, that is, the sand 4 transfer portion with the silos 5 and 6. In other words,
The transfer body 1 is provided so as to pass through the freezing duct 16. The terminating side of the transfer body 1 of the freezing duct 16 is connected to a cold air duct 18 via a connecting duct 17 bent upward. Blowers 19 and 19 are provided inside the cold air duct 18. The cold air duct 18 is branched in the middle thereof, one of which is connected as a branch pipe 20 to a silo (not shown) in which coarse aggregate is stored, and the other of which is located at the starting end side of the transfer body 1. Is directed downwards. The above-mentioned freezing duct 17, cold air duct 18, and blowers 19, 19 collect the liquefied nitrogen blown into the freezing duct 16 and transfer the body 1.
A pre-cooling device C for pre-cooling the sand 4 is formed by blowing the sand 4 onto the sand 4.

Further, the transfer body 1 is provided with a cooling source device B which blows liquefied nitrogen onto the sand 4 transferred on the upper surface thereof to cool it. This cooling source device B is a liquefied nitrogen storage tank 10 installed on a base G or another place, a control device 11 for controlling the supply amount of liquefied nitrogen supplied from this tank 10, and this control device 11. Supply pipe 12 for supplying liquefied nitrogen from the transfer body 1 to the transfer body 1, and a pipe which is connected to the supply pipe 12 through a flexible joint 13 and is laid along the longitudinal direction above the transfer body 1 of the freezing duct 16. 14, 14 and a spray nozzle which is provided at a predetermined interval in the longitudinal direction of these pipes 14, 14 and blows the liquefied nitrogen into the inside of the transfer body 1.
It is composed of 15, 15, and so on.

Next, a method of using the aggregate cooling device according to the embodiment of the present invention will be described.

First, the vibration mechanism 2 of the sliding shooter A is driven to vibrate the transfer body 1 in the vertical direction in advance. Here, the sliding number and stroke of the transfer body 1 are arbitrary, and the retention time of the sand 4 on the transfer body 1 can be adjusted by adjusting these appropriately.

Next, the sand 4 stored in the silo 5 is dropped onto the starting end portion of the transfer body 1 by opening the lid 7. As a result, the sand 4 dropped on the transfer body 1 is transferred on the transfer body 1 while vibrating, jumping, and rotating on its upper surface, and is thrown into the silo 6 from the end portion.

Then, while the sand 4 is being transferred on the transfer body 1,
The cooling source device B sprays liquefied nitrogen on the sand 4. Specifically, the control device 11 supplies liquefied nitrogen from the tank 10 to the pipes 14 and 14 via the supply pipe 12. As a result, liquefied nitrogen is sprayed onto the sand 4 through the spray nozzles 15 and 15, and the sand 4 is cooled to below zero. Therefore, the surface water on the surface of the sand 4 is frozen, and an ice layer is formed on the surface of the sand 4. Here, the sand 4 which is usually used for producing concrete has about 5 to 10% of surface water, but when it is considered that the surface water amount is insufficient, the sand 4 is previously prepared. It is preferable to adjust the amount of surface water by sprinkling water or the like. Further, the spray nozzles 15 and 1
The discharge amount of liquefied nitrogen by 5, ... Is arbitrary, but by appropriately selecting this discharge amount and the frequency and stroke of the transfer body 1, the residence time on the transfer body 1 is adjusted and cooled. The desired cooling temperature can be adjusted according to the type of material used.

At the same time, by driving the blowers 19 in the cold air duct 18, the direction of the arrow shown in FIG.
An airflow that flows from 16 toward the cool air duct 18 is generated. As a result, the low-temperature gas that has cooled the sand 4 circulates in the order of the freezing duct 16, the connecting duct 17, and the cold air duct 18, and a part of the low temperature gas passes through the branch pipe 20 to store the coarse aggregate. Is supplied to cool the coarse aggregate,
By supplying the rest below the silo 5, the sand 4 can be pre-cooled.

By the method described above, the sand 4 having the ice layer formed on its surface can be manufactured. Then, sand 4 is mixed with gravel (coarse aggregate), cement, water or ice fine particles, and if necessary, various admixtures are mixed to produce concrete. The method of mixing the constituent materials of each of these concretes is arbitrary, but as an example, the sand 4 is first charged into a kneader such as a concrete mixer, and then the fine particles of cement, gravel, water or ice are mixed in this order. A method in which concrete is produced by introducing the mixture into a kneading machine and kneading and mixing them is preferable. Of course, these may be put into the kneading machine at once. Further, a method in which the sand 4 is sprinkled with cement to uniformly disperse the cement particles on the surface of the ice layer of the sand 4, and the cement particles are put into the kneading machine together with fine particles of gravel, water or ice. Is also preferable. In this case, by replacing a part of the mixed water with fine particles of ice, it is possible to lower the kneading temperature of concrete and increase the concrete strength, as in the conventional method.

Therefore, according to the cooling apparatus for aggregates described above, by vibrating the transfer body 1 by the vibrating mechanism 2, the sand 4 transferred on the upper surface is vibrated and liquefied nitrogen is sprayed on the sand 4. Thus, the sand 4 can be cooled to below zero. Thereby, the surface water of the sand 4 can be frozen and an ice layer can be formed on the surface of the sand 4. Further, since the sand 4 is also cooled by using a liquid at a very low temperature called liquefied nitrogen, the sand 4 can be cooled in a short time while being vibrated, so that an ice layer can be formed easily and surely. You can Especially, since the sand 4 is rapidly cooled to the ultra-low temperature by the liquefied nitrogen, the sand 4 can be formed even after the ice layer is formed.
The particles do not fuse together.

Then, when the concrete is manufactured using the sand 4 having the ice layer formed on the surface thereof by the above-described aggregate cooling device, the effects such as the decrease of the concrete kneading temperature and the increase of the concrete strength can be obtained in the same step. Can be obtained at That is, as shown in FIG. 3, an ice layer is formed on the surface of the sand 4.
Due to the presence of 21, the cement particles 22 evenly adhere to the surface of the ice layer 21 when mixing a concrete constituent material such as cement. Therefore, due to the latent heat of ice and the cold heat of the aggregate, the kneading temperature of concrete is lowered and the cement particles are uniformly dispersed,
The unit water amount can be reduced, and the strength of the resulting concrete can be increased. further,
Since a dense cement paste is formed on the surface of the aggregate during kneading, the adhesive strength between the aggregates is increased, and the strength of the concrete can be increased also from this aspect. Therefore, if the concrete is manufactured using the sand 4 having the ice layer formed on the surface, the decrease of the kneading temperature of the concrete and the increase of the concrete strength can be realized at the same time.
The cracking of this concrete can be reduced more than the conventional method.

Further, by using this sand 4, the kneading temperature of concrete can be lowered and the strength of concrete can be increased without using ice for the kneading water, so that a part of the conventional kneading water can be obtained. Unlike the method of substituting ice with fine particles of ice, there is no possibility that ice remains in the obtained concrete even when the temperature of the concrete is not relatively high except during the heat. Therefore, even under severe construction conditions such as autumn-winter-spring, the above-mentioned effects are unchanged.

Here, the prediction result of the concrete kneading temperature decrease due to the sand produced by the cooling apparatus for aggregate of the present invention and having the ice layer formed on the surface, which has been performed by the present inventors, will be described. The concrete mixes studied are as shown in the table below.

For the prediction of the kneading temperature of concrete, the physical properties were selected assuming that the construction period is mainly summer. In the following prediction results, it was assumed that the cement temperature was 60 ° C, the water temperature was 20 ° C, the ice temperature was -10 ° C. The prediction result is shown in FIG. 4, in which the temperature of the fine aggregate (sand) is plotted on the horizontal axis and the kneading temperature of concrete is plotted on the vertical axis. The predicted value was calculated under the following four conditions.

Tg = 30 ° C, x = 0% (solid line 31 in the figure) Tg = 20 ° C, x = 0% (chain line 32 in the figure) Tg = 30 ° C, x = 30% (dotted line 33 in the diagram) Tg = 20 ° C , X = 30% (dashed-dotted line 34 in the figure) Tg: coarse aggregate temperature, x: replacement ratio of water with ice In all cases, the fine aggregate (sand) is cooled to below 0 ° C. By forming an ice layer on the surface of the aggregate, it is possible to obtain a marked decrease in the temperature at which the concrete rises. In particular, the effect is magnified by simultaneously cooling the coarse aggregate and substituting the kneading water with ice.

The aggregate cooling device of the present invention is not limited to the above embodiment. As an example, the low-temperature liquid or gas that cools the sand 4 is not limited to liquefied nitrogen as in the above-described embodiment. For example, if liquefied helium having a lower boiling point than liquefied nitrogen is used, the sand 4 can be cooled more efficiently. Is possible. Further, it goes without saying that the aggregate on which the ice layer is formed is not limited to the sand 4 and can be similarly applied to coarse aggregate such as gravel.

[Advantages of the Invention] As described in detail above, according to the present invention, the aggregate is vibrated and transported by the transport body and the vibrating mechanism to be passed through the freezing duct, while the liquefied gas is cooled by the cooling source device. Since the ice layer was formed on the surface of the aggregate by blowing it into the freezing duct to cool it to the freezing temperature, it is possible to rapidly freeze the surface water of the aggregate by the cryogenic liquefied gas. In addition to being able to easily and reliably form an ice layer on the surface of the aggregate, in particular, by vibrating the aggregate to cool it while jumping and rotating it, the ice layer is evenly distributed over the entire aggregate surface. In addition to the formation of ice, it is also possible to prevent the aggregates on which the ice layer is formed from freezing and adhering. Furthermore, the pre-cooling device collects the liquefied gas from the freezing duct and inputs it to the transfer body. Since the pre-cooled aggregate is pre-cooled, the liquefied gas can be reasonably and effectively utilized without waste, and excellent cooling efficiency can be obtained in a short time.

Therefore, by using the aggregate in which the ice layer is formed by the cooling device of the present invention, it is possible to sufficiently reduce the kneading temperature of the concrete and prevent cracks after hardening, and it is also possible to prevent the entire ice layer of each aggregate from occurring. Since the cement particles are evenly adhered to the cement particles, the cement particles are naturally dispersed evenly throughout the concrete, and the adhesion strength between the aggregates is increased, and as a result, the concrete strength can be increased. Furthermore, by using the aggregate produced by the cooling device of the present invention,
Even if ice is not used for the kneading water, the kneading temperature of the concrete can be lowered and the strength of the concrete can be increased, so that the effect is unchanged even under severe working conditions such as autumn-winter-spring.

[Brief description of drawings]

1 and 2 are views showing an aggregate cooling apparatus according to an embodiment of the present invention, in which FIG. 1 is a schematic view showing the entire structure, and FIG. 2 is a II- of FIG. A cross-sectional view taken along line II ', FIG. 3 is a cross-sectional view showing a state of sand produced by an aggregate cooling apparatus according to an embodiment of the present invention, and FIG. 4 is an aggregate produced by the same cooling apparatus. It is a figure which shows the result of having investigated the effect of the mixing-up temperature fall of the concrete by. B ... Cooling source device, C ... Precooling device, 1 ... Transport body, 2 ... Vibration mechanism, 4 ... Sand (aggregate), 6
...... Freezing duct, 17 ...... Connecting duct, 18 …… Cold air duct, 19 …… Blower, 21 …… Ice layer, 22 …… Cement particles.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuhiko Kimura 2-16-1 Kyobashi, Chuo-ku, Tokyo Within Shimizu Construction Co., Ltd. (72) Inventor Kazuya Kamezaki 2-16-1 Kyobashi, Chuo-ku, Tokyo Shimizu Construction Co., Ltd. Inspector Noriko Suzuki (56) References JP-A-61-201681 (JP, A) Latest powder and particle process technology compilation editorial board "Latest powder and particle process technology compilation <Basic technology section] > ”May 1, 1976, Industrial Technology Center Co., Ltd. 150-151 pages 181-182 pages

Claims (1)

[Claims] 1. A precooling construction method in which the concrete temperature is lowered before pouring to prevent cracking of concrete, and the aggregate, which is a constituent material of concrete, is cooled by liquefied gas. A cooling device for forming an ice layer on a surface, a freezing duct into which a liquefied gas is blown, a transfer body for transferring an aggregate to be cooled through the freezing duct, and a vibration of the transfer body. A vibrating mechanism that vibrates the aggregate to be cooled that has been introduced into the transfer body, and cools the aggregate by blowing liquefied gas into the freezing duct and spraying the aggregate transferred by the transfer body. A cooling source device that freezes the surface water, and the liquefied gas blown to the aggregate by the cooling source device is collected from the freezing duct and thrown to the transfer body. Cooling device Cracking concrete aggregate, characterized by comprising; and a pre-cooling device for precooling it by blowing to the bone material before cooling being.