JP2011037248A - Ready-mixed concrete controlling method stabilizing kneading temperature - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To supply ready-mixed concrete of stable quality by preventing variations in slumps and the amount of unit water by suppressing the temperature variation of the ready-mixed concrete according to seasonal variation, daily variation, or a time zone. <P>SOLUTION: In a method for controlling the temperature of ready-mixed concrete, in a method for supplying the ready-mixed concrete at a constant target temperature by increasing a material temperature by heating water and aggregate, a steam jetting nozzle is installed in the lower part of each aggregate tank of the upper part of a metering tank, and a constant amount of steam is introduced synchronously with kneading to control the temperature to be the target ready-mixed concrete temperature. Steam is introduced directly into the aggregate immediately before the aggregate is weighed and kneaded, and heat exchange is carried out efficiently, to well respond to temperature control. By controlling the temperature of the ready mixed concrete to be constant, variations in slumps, the amount of unit water, etc., are eliminated, thus producing the ready-mixed concrete of the stable quality. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a manufacturing technique for stabilizing the quality of raw kon by stabilizing the kneading temperature of the raw kon.

Raw concrete is a basic construction material used in large quantities. It is a composite material consisting of cement, water, coarse aggregate, fine aggregate, other admixtures, admixtures, etc. The finished concrete is a composite that requires advanced performance based on chemical reaction between cement and water. Although it is a material, its manufacturing technology and management technology are also limited due to its low price. Above all, quality control methods are assembled on the premise that the temperature of raw concrete changes as a natural phenomenon.

It is a basic phenomenon that the amount of unit water for keeping the slump value, which is an index of ease of driving, changes when the raw concrete temperature changes. As the unit water amount changes, the strength also changes. Therefore, a method of correcting the cement amount is often used for the purpose of keeping the strength constant without changing the water / cement ratio (W / C). Alternatively, a method may be used in which the slump is kept constant by changing the admixture addition amount without changing the unit water amount. There is also a report that there was a difference of 15 kg / m ^ 3 in the unit water volume of the same composition in winter and summer when these appropriate measures were not taken. (See Non-Patent Document 1)

The curing reaction of cement and water is a chemical reaction accompanied by heat generation, and the higher the temperature, the faster the reaction speed. Therefore, the number of days required to obtain the required strength varies greatly depending on the season. In order to compensate for this, blending correction that increases the amount of cement may be performed in the low-temperature season. (See Non-Patent Document 2)

The temperature of raw cooking appliances varies not only during the season but also throughout the day, making quality control difficult.
At the start of the morning kneading, the temperature of the ingredients and the main body of the mixer are decreasing, the temperature of the raw kneading is low, and the temperature of the raw kkon rises as the temperature rises. As a result, the temperature of raw concrete changes during the day, and the slump and unit water volume also change.

As described above, the premise that the temperature change of the ready-mixed food is a natural phenomenon makes it inevitable that the quality control of the ready-made cooked food becomes complicated and the quality instability cannot be solved. There is an example in which a patent was filed that tried to automatically correct the composition by capturing the temperature change of the raw concrete, but the premise that the temperature of the raw concrete is changed has not changed. (See Patent Documents 1 and 2)

On the other hand, high-strength, high-durability concrete has been demanded, and quality requirements for ready-mixed foods have also become higher. The situation where the acceptance inspection of the unit water quantity of raw concrete becomes strict, the submission of the measurement record of raw concrete mixed with the revision of JIS standard of ready mixed concrete (JISA5308) becomes mandatory, and the burden of quality control records increases for manufacturers There is.

  JP-A-8-127020   JP 2003-103514 A

  Japan Concrete Institute 2004 Fresh Concrete Unit Water Volume Rapid Measurement and Management System Research Committee Report P14   Architectural Institute Japan Architectural Standard Specification JASS5 Reinforced Concrete Work Temperature Compensation

When manufacturing ready-mixed concrete, there are various factors that cause quality fluctuations, such as changes in temperature, unit water volume, and quality of the materials used, but the most important one is due to the chemical reaction between cement and water due to changes in ready-made temperature. Variable factors. Conventional concrete manufacturing technology has been managed on the premise of fluctuations, assuming that changes in the temperature of raw concrete are natural and unavoidable. On the other hand, quality requirements for concrete are gradually increasing in the times, and high strength and high durability concrete is required. These concretes were made possible by making concrete with a low water cement ratio by using various admixtures and admixtures such as high performance AE water reducing agents. The tolerance for fluctuations is extremely small, and its manufacturing requires strict quality control.

Generally, temperature management is the most important management item in the primary material manufacturing industry. As the performance required for concrete becomes higher, the acceptance inspection of raw concrete and the regulation of quality control become complicated, but the fundamental temperature management remains unchanged.
It is difficult to produce a stable quality ready-mixed product without keeping this temperature condition constant.

Although it is difficult to maintain a constant temperature throughout the year, it is possible to manage it at a constant temperature determined for each season. If the temperature condition is kept constant, the remaining fluctuation factor is only the material, which makes it easy to produce a stable quality raw control.

The present invention has been made in view of such conventional problems, and controls the temperature of raw concrete by preheating the material and the main body of the mixer in advance, and by controlling the temperature of raw concrete at a constant level such as slump and unit water amount. An object of the present invention is to provide a temperature control method for raw concrete that stabilizes quality.

The present invention has been made in order to solve the above-mentioned problems, and in order to eliminate the temperature change of the raw kon and stabilize the slump and the unit amount of water, the raw kon temperature management method according to claim 1, In addition, the temperature of the raw material is adjusted by adjusting the temperature of the steel material constituting the mixer and the temperature of the water and the aggregate, which are the materials, to stabilize the quality of the raw material.

Moreover, in the raw-corn management method of Claim 2, it preheats to the temperature which makes the steel material temperature which comprises a mixer the target temperature using warm water as kneading preparatory work, It is characterized by the above-mentioned.

Moreover, in the raw concrete management method according to claim 3, an appropriate amount of steam is blown in synchronization with the lower part of each aggregate tank for supplying the aggregate to the measuring tank, and the warmed aggregate is used for mixing. It is characterized by controlling the temperature of the raw material by controlling the temperature of the material, stabilizing the temperature of the raw material, and stabilizing the quality of the raw material.

The operation of the above solution is as follows. In other words, not only the materials but also the steel of the mixer itself is cold at the start of the day's kneading work, and the weight of the steel is 2-3 times the weight of the raw mix to be kneaded. As a result, preheating of the steel material is necessary. In addition, every time a batch is mixed, an appropriate amount of steam is injected into the aggregate part to be weighed the next time so that it can be corrected immediately if there is a difference between the measured temperature and the target temperature. It is made to be able to. Vapor is released from a nozzle with a large number of small holes on the surface of a cylindrical shape. Both coarse and fine aggregates have appropriate voids between particles, and their surface area is large relative to their weight. The heat quantity of the steam is absorbed by the aggregate in a short time, and the steam becomes condensate. For this reason, the surface water of the aggregate will increase, but the amount of steam for raising the aggregate temperature by 10 ° C. is about 0.3% with respect to the aggregate weight, and the surface water will increase accordingly. There is no problem if the amount of surface water is corrected.

As described above, when the raw control temperature control device of the present invention is used, it can be manufactured at a target constant temperature. For this reason, since the fluctuation | variation of the unit water quantity and slump which arise due to a temperature change are lose | eliminated, the quality of raw concrete becomes stable. There are other fluctuation factors of slump and unit water volume, such as fluctuation of surface water contained in aggregate and quality of material, but the fluctuation factor is simplified by managing constant fluctuation temperature on a daily basis, Much easier to deal with.

In addition, raising the temperature of ready-mixed concrete in the low-temperature season will increase the concrete's curing reaction speed, shorten the curing period after placing, increase work efficiency, and modify the composition by changing the temperature. This eliminates the need for quality management.

Furthermore, since the method of preheating the material immediately before mixing according to the present invention has a very high thermal efficiency, the curing is accelerated when compared with the conventional low temperature raw material curing when steam curing accelerated precast factory products or the like. Greatly reduces fuel costs.

In order to control the temperature of the ready-mixed food, it is premised that the temperature of the ready-made food can be accurately measured all the time while mixing. A method of measuring with a temperature sensor in which a liner plate mounting bolt in the mixer outer plate is drilled and embedded, or a method of attaching a temperature sensor to the mixer outer plate steel surface and backing up the back surface with a heat insulating material may be used.

The temperature gradient when there is a temperature difference between the raw concrete temperature and the outside air temperature is that there is almost no thermal resistance in the air layer on the surface of the steel plate, and the temperature difference occurs at this interface, so the temperature difference between the raw concrete temperature and the steel plate temperature is rare. Also, the ready-mixed steel and the steel plate are in close contact with each other, and the thermal conductivity of the steel plate is good, so that it can follow the temperature change.

The temperature of the ready-mixed concrete is determined by the amount of heat held by each material, the initial hydration reaction heat determined by the amount and quality of the cement, and the heat energy converted from the kinetic energy by mixing. Since it cannot be accurately estimated only by the material temperature, it is more reliable to control the heating amount of the material using the kneading temperature measured by the above method as data.

In addition, in order to improve control responsiveness, a steam nozzle is installed in the lower part of the aggregate tank at the upper part of the measuring tank, and a structure in which an appropriate amount of steam is injected in synchronization with mixing is heated. Ensure that the aggregate is used for the next weighing. The sprayed steam comes into contact with the cold aggregate and at the same time loses heat to the aggregate, and becomes self-condensed and raises the surface water ratio of the aggregate. However, the increase in the surface water ratio due to the steam that raises the aggregate temperature by 10 ° C. is about 0.3% with respect to the aggregate weight, and may be reflected in the surface water correction input when measuring the material.

A general batcher plant includes a plurality of aggregate tanks for coarse aggregate and fine aggregate, and has a structure in which a plurality of materials can be used together. Each aggregate tank is equipped with a steam spray nozzle and a temperature sensor. Steam is supplied through an electromagnetic valve, and the valve is opened for a time indicated by each batch by a signal from the controller to supply an appropriate amount of steam. The unused aggregate tank is designed to stop the signal, and only necessary parts are operated.

A temperature sensor is installed near the outlet of the aggregate silo to measure the aggregate temperature, but heating with steam does not uniformly heat the aggregate temperature, so accurate measurement cannot be performed. In order to capture the average temperature as much as possible, a sheath tube is installed and a temperature sensor is placed in it and measured.
It is considered that the measured temperature of each aggregate is easy to use, and is not used for direct control but is used as auxiliary data for judging the aggregate temperature.

The target temperature of the ready-mixed rice can be set to a temperature that is slightly higher than the fluctuation range of the ready-to-use temperature predicted for the season. The degree of heating is determined based on the difference between the kneading temperature predicted when the material is not preheated and the target temperature. The weather conditions and the degree of heating up to yesterday are important judgment materials. The controller incorporates a program in which the injection time is increased stepwise based on basic data that makes the temperature rise of each aggregate equal, and can be switched by a select switch. After the kneading operation is started, while monitoring the kneading temperature by the measuring means, the injection time is controlled by switching the select switch, and the kneading temperature is controlled by controlling the aggregate temperature.

Hereinafter, the present invention will be described in detail based on an embodiment. The batcher plant has a tower-like structure, and there is a storage tank for storing each used material on the top floor, and a measuring tank for each material on the lower floor. In addition, a mixer is installed on the lower floor. There is a hopper under the mixer, and after taking the ready-mixed raw mix, it is thrown into the live mix car.

The structure of the batcher plant is designed so that the mixer is fully operational and the productivity is increased, and the weighing process, mixing process, and loading process to the ready-mixed vehicle are performed simultaneously. The control panel of the batcher plant is controlled so that most of it automatically proceeds as long as necessary conditions are entered. However, since there was no idea of controlling the temperature in the conventional batcher plant, no temperature measuring device was installed.

The temperature control method according to the present invention stabilizes the quality of slump, unit water quantity, etc. by producing a temperature-controlled concrete by heating water and each aggregate using steam as a heat source. However, since this example was a precast product factory, there was already a boiler facility and it was sufficient to extend the steam piping to the batcher plant.

In order to control the temperature, the temperature measurement method is first used. However, in order to always measure the temperature of the raw material during operation, the temperature of the steel material constituting the mixer outer plate is measured to obtain the raw material temperature.
In the temperature distribution when there is a difference between the raw concrete temperature in the mixer and the outside air temperature, most of the thermal resistance is in a non-moving air layer in contact with the steel material surface, so the temperature difference occurs in the boundary layer. In addition, since the ready-mixed material and the steel material are in close contact with each other and the heat conduction of the steel material is good, the ready-made temperature and the steel material temperature are almost the same.

Regarding the water temperature, a temperature sensor is installed at a relatively upper part of the tank. The temperature sensor for each aggregate is installed near the aggregate outlet, but a sheath tube is installed and set in it to capture the averaged temperature as much as possible.

A nozzle having a large number of small holes is arranged at the bottom of the water tank via an electromagnetic valve, and the temperature is controlled by the water temperature measuring sensor. This warm water is used for premixing the steel material temperature of the mixer body to the target temperature as a preparatory work before the start of kneading and simultaneously for kneading.

The temperature control method of the present invention is to control the temperature of the raw concrete by raising the temperature of the raw concrete by warming the water, coarse aggregate, and fine aggregate that are the materials to be used. For this reason, steam is spouted for a certain period of time in synchronism with mixing from a nozzle with a large number of small holes in the cylindrical surface at the bottom of each aggregate tank where the aggregate to be weighed next time is stored. It preheats the aggregate. Steam is supplied to the nozzle via an electromagnetic valve, and the amount of steam is adjusted by controlling the time to open the electromagnetic valve by a signal from the controller.

The above heating operation is performed in synchronism with the kneading, but the kneading work cycle is about 60 seconds to 120 seconds, and is set so that the necessary amount of steam can be injected within this time. Vapor ejected from many small holes has 30-40% voids between particles, and when it comes into contact with an aggregate having a large surface area relative to its weight, it passes latent heat of vaporization to the aggregate in a short time and changes itself into condensate. To do. The amount of steam is about 0.3% of the aggregate weight when the aggregate temperature is raised by 10 ° C, and the surface water of the aggregate increases, but the surface water input value for measurement is corrected accordingly. No problem.

At this time, most of the thermal energy of the steam is absorbed by the aggregate part to be weighed next time, so that it can be corrected with good response when trying to correct the temperature of raw concrete by changing the amount of steam. The temperature control is based on basic data that raises the temperature of each aggregate evenly, so that the steam volume can be switched in stages with the select switch, and the setting level is determined from the data up to yesterday and the weather conditions of the day. Then start mixing and adjust the actual kneading temperature.

In the morning of starting the day's work, the temperature of the steel material constituting the mixer is decreasing, and in order to obtain a stable raw temperature, it is necessary to preheat the mixer body to the target temperature by adding and stirring hot water. . Since the weight of the steel material of the mixer main body is about 2 to 3 times the weight of the raw mix to be mixed, the heat capacity is large. Prior to the implementation of the present invention, a temperature change of 4 to 5 degrees was sometimes observed during the day. However, the quality of the ready-mixed rice was also stabilized by stabilizing the temperature of the ready-made rice.

The target temperature of the raw concrete temperature is determined by setting a target temperature that is slightly higher than the range of fluctuations that are expected to occur in the season, and appropriately preheating water and aggregates, which are the mixer body and materials, throughout the season. Fluctuations and time fluctuations can be eliminated, and the quality such as slump and unit water volume can be stabilized by stabilizing the temperature. In addition, over the period, there was no need to modify the composition due to temperature changes, and management effort was reduced.

Claims (3)

The temperature control method for raw concrete that stabilizes the quality of raw concrete by adjusting the temperature of the steel that constitutes the mixer and the temperature of the water and aggregates that are the ingredients before producing the raw concrete. In the said raw-corn temperature management method, the steel material temperature which comprises a mixer is preheated to target temperature using warm water as mixing preparation work, The raw-corn temperature management method of Claim 1 characterized by the above-mentioned. In the raw concrete temperature control method, an appropriate amount of steam is blown into the lower part of each aggregate tank that supplies aggregate to the measuring tank in synchronization with the mixing, and the material is mixed using the warmed aggregate to control the material temperature. 3. The method of controlling the temperature of raw food according to claim 1 or 2, wherein the temperature of the raw food is controlled to stabilize the quality of the raw food to stabilize the quality of the raw food.