JP3181487B2 - Concrete mixing temperature control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for appropriately controlling the temperature at which concrete is cooled when a low-temperature liquefied gas such as liquid nitrogen is brought into contact with concrete during mixing to obtain a cooled concrete kneaded material. About.

[0002]

2. Description of the Related Art As a pre-cooling method for cooling concrete before casting, one of the concrete cooling techniques for preventing temperature cracking of mass concrete or the like, a low-temperature liquefied gas such as liquid nitrogen is brought into contact with concrete being kneaded. There is known a method for causing the same to occur, for example, in Japanese Patent Application Laid-Open No. 62-7460.
No. 3, JP-A-63-4169, Japanese Utility Model Application Laid-Open No. 2-5
Nos. 4506 to 7 disclose a precooling method for concrete using liquid nitrogen. It has also been proposed to use liquid carbon dioxide as a cooling medium instead of liquid nitrogen. In the specification of the present application, liquid nitrogen, liquid carbon dioxide, and the like used for such pre-cooling of concrete are simply referred to as “liquefied gas”.

Conventionally, when a liquefied gas is supplied to a mixer such as a batcher plant (usually, the liquid is charged into the mixer in a liquid state), the amount of the liquefied gas to be charged is determined as a tentative reference as follows. Cooling unit of liquefied gas required to cool concrete, that is, "1 m of concrete
The amount (weight) of liquefied gas necessary to cool ³ at 1 ° C was determined experimentally, and this cooling basic unit was determined by multiplying the kneading amount per batch and the required temperature drop amount. . Also,
The kneading temperature was measured as appropriate, and when the temperature deviated from the intended temperature, the next amount was empirically increased or decreased.

FIG. 1 shows actual measured values of a kneading temperature on a certain day when pre-cooling is performed by determining a liquid nitrogen input amount from a cooling unit unit in a batcher plant at a dam construction site. Things. Small fluctuations (waves) in the curves indicate changes in the batch temperature for each batch.
The type and amount of materials to be fed into the batcher plant are almost constant, but since the start of operation at 8:00 am, the kneading temperature gradually rises with the lapse of time, and the target kneading temperature decreases as the day approaches. It exceeds the value. The reason for this is that there are too many fluctuation factors based on environmental changes such as solar radiation, water temperature, air temperature, material temperature, equipment temperature, and waiting time.
Empirical methods show that it is difficult to control the kneading temperature accurately. In particular, changes in solar radiation are unpredictable, and the previous day's experience is often useless in this regard.

[0005]

In the pre-cooling of concrete using liquefied gas, as described above, the cooling unit varies depending on the temperature of each material and the temperature drop due to environmental changes on that day. Since it is necessary to constantly change the set value of the amount of liquefied gas to be supplied, the temperature control operation becomes very complicated. Also, it is difficult to pay attention only to these temperature controls at the concrete casting site, and it has been strongly desired to automate these adjustments.

In addition, the concrete temperature after cooling is measured, and the amount of liquefied gas is set while controlling the concrete kneading temperature while comparing with the target cooling temperature. There is also a problem that a batch to be kneaded must be delayed in order for the corrected input amount to be reflected in the control because of the correction.

[0007] The target of temperature control in concrete casting is the concrete temperature at the casting site. The temperature difference between the kneading site and the casting site in the batcher plant is sometimes measured at the casting site. There is a problem that the work becomes extremely complicated, such as comparing the concrete temperature with the temperature before being conveyed from the plant to make empirical corrections, or constantly measuring the concrete temperature at the site of pouring. Was.

Accordingly, the present invention solves the above-mentioned problems, and provides a method for automatically and accurately controlling a kneading temperature to a required temperature when kneading concrete cooled by using a liquefied gas in a batcher plant. Is to do.

[0009]

According to the present invention, as described in claim 1, liquefied gas is introduced into a mixer of a batcher plant, and cooled concrete is substantially quantitatively produced for each batch. When the resulting kneaded material was transported to a concrete casting site and cast sequentially,
First, the necessary liquefied gas input amount W ₀ (kg) is set using the equation (1) at the start of casting, and W ₀ = w × V × (T ₁ −T ₀ ) (1) W _0: liquefied gas input amount (kg) w: liquefied gas amount necessary to cool intensity (kg / m ³ ℃) ·· concrete 1 m ³ to 1 ℃ cooling (experimentally determined in advance value) V: each Amount of concrete kneaded in batch (m ³ ) T ₁ : Actual measured value of concrete kneading temperature without liquefied gas input (° C.) T ₀ : Target concrete kneading temperature (° C.) Then, this liquefied gas is injected W ₀ ( kneaded was charged in kg), and continues to measure the concrete mixing up temperature t _n for each batch, obtains a temperature difference Δt between the previous batch from the measured value, when the Δt exceeds a set range, (2) below
The correction amount ΔW (kg) of the liquefied gas input amount is calculated based on the equation, and ΔW = W ₀ × Δt / (T ₁ −T ₀ ) (2) This correction value ΔW is expressed by equation (3). liquefied by increasing or decreasing the gas input amount W ₀ set the next input amount _{W 1, W 1 = W 0} + ΔW ··· (3) Thereafter, the next time to increase or decrease the correction amount [Delta] W to the corrected W _n to The present invention provides a concrete kneading temperature control method, which comprises setting an input amount of concrete.

Here, Δt is the kneading temperature t of the n-th batch.
More accurate by calculating from the difference between the average temperature of the concrete mastication temperature (t _{n + 1,} t _{n + 2,} t _{n + 3} ...) of _n and subsequent two or more successive batches Control.

Further, according to the present invention, a liquefied gas is charged into a mixer of a batcher plant to produce cooled kneaded concrete for each batch, and the obtained kneaded material is transported to a concrete casting site. In order to put in
The temperature of the concrete compounding material immediately before being put into the mixer is measured for each batch, and from these measured values, the expected concrete mixing temperature Pt _n is calculated, and the mixing temperature t _n for each batch is measured _. First, the initial liquefied gas input amount W ₁ is determined by the equation (4), and W ₁ = w × V × (Pt ₁ −T ₀ ) (4) W ₁ : initial liquefied gas input amount (kg) ) w: basic unit of cooling (kg / m ³ ℃) ・ ・ Amount of liquefied gas required to cool 1 m ³ of concrete by 1 ℃ (value obtained beforehand experimentally) V: amount of concrete to be kneaded (m ³ ) T ₀ : Target concrete kneading temperature (° C) Pt ₁ : Expected kneading temperature (° C) In the subsequent batches, _the previous measured kneading temperature t
Set _n-1 is the target concrete mixing up temperature T ₀ range T ₀
When the temperature is within the range of ± x ° C (x is an allowable value), the following equation (5)
Calculates a correction value ΔW _n of the liquefied gas input amount according to the following equation: ΔW _n = W _n−1 × (Pt _n −Pt _n−1 ) / (Pt _n−1 −T ₀ ) (5) This correction amount From ΔW _n and previous liquefied gas input amount W _n-1
(6) setting the liquefied gas input amount W _n according _{formula, W n = W n-1} + ΔW n ··· (6) concrete mixing up temperature control method according to claim (claim 3), and

In the next and subsequent batches, _{when the} previous measured temperature of the mixing temperature t _n-1 is out of the range of the target concrete mixing temperature T ₀ set range T ₀ ± x ° C. (x is an allowable value), A correction value ΔW _n of the liquefied gas input amount according to the equation (7) is calculated, and ΔW _n = w × V × (t _n−1 −T ₀ ) (7) This correction amount ΔW _n and the previous liquefied gas From the input amount W _n-1
(6) setting the liquefied gas input amount W _n according to Formula provides _{W n = W n-1 +} ΔW n ··· (6) concrete mixing up temperature control method according to claim (claim 4).

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The contents of the present invention will be specifically described below.

The control of the concrete kneading temperature of the present invention is directed to a pre-cooling method in which liquefied gas is injected into a mixer to cool concrete, and in particular, the kneading is performed continuously in a batcher plant. It is suitably applied to a case where the material is transported to a site such as a dam construction and is driven. As a liquefied gas to be used, liquid nitrogen is practical, but in some cases, it can be applied when other low-temperature liquefied gas such as liquid carbon dioxide gas is used.

In the control according to the first aspect of the present invention, in such a pre-cooling method, the concrete kneading temperature t _n is measured for each batch as required, and the temperature difference Δt from the previous batch is calculated. A method for controlling the concrete kneading temperature by increasing or decreasing the amount of liquefied gas proportional to the ratio of the concrete temperature drop amount ΔT ₀ = (T ₁ −T ₀ ) set at the start of casting to the total liquefied gas amount In the mixer of the batcher plant, the concrete kneading temperature during or immediately after discharge from the mixer to the bogie is constantly measured by a temperature sensor, and this measured value is input to the computer, and the amount of liquefied gas charged for each batch is input. Is calculated, and a signal is output to the control panel as a set value of the liquefied gas input amount, thereby automatically controlling the control panel.

In the above equation (1), the initial determination of the liquefied gas input amount W ₀ is determined when concrete construction starts.
In that time zone, it starts by finding _the required temperature drop amount, that is, the difference (T ₁ −T ₀ ) from the target kneading temperature T ₀ , from the actual measurement value T ₁ of the concrete kneading temperature without adding liquefied gas. . Cooling intensity w, concrete 1
The amount of liquefied gas required to cool m ³ by 1 ° C. is previously determined experimentally in the formulation.

In this way, the necessary liquid nitrogen input amount W ₀ is set using the equation (1). Thereafter, if the kneading temperature after cooling has reached the target temperature, the amount of liquefied gas charged remains unchanged, but if the kneading temperature t _n changes, the measured value t _n− By comparing it with ₁ , a temperature change amount Δt _n = t _n −t _n−1 is obtained, and a ratio between the target temperature drop amount (T ₁ −T ₀ ) and the initially set input amount W _{0 is used.} calculated by the correction value [Delta] W (2) equation for, (3) setting the next input amount W ₁ by adding the correction value [Delta] W in input amount W ₀ of the first by type.

That is, by controlling to add the correction amount ΔW to the initially set liquefied gas input amount W ₀ , the concrete kneading can be performed even when the cooling unit consumption and the temperature of each compounding material of the concrete change. The temperature can be controlled to a target value. And, thereafter, it continues to control the addition of the next correction amount ΔW to the corrected W _n. This relationship is illustrated in FIG.

However, the upper limit of the correction amount of the liquefied gas is set in advance. As a result, a large change in the liquefied gas input amount can be suppressed when a temperature change in a range that cannot normally occur in one batch due to erroneous measurement occurs. In addition, when the correction of the liquefied gas input amount is performed not for each batch but for a plurality of batches (claim 2), a large change in the correction value due to a variation at the time of measurement in each batch is mitigated, and the stability is improved. Control can be performed. This relationship is illustrated in FIG.

In FIG. 3, the measured value of the kneading temperature for each batch is shown by a solid line. When the measurement result for each batch is used, the value of W to which the correction value has been added is shown by the broken line in the upper row. There are batches in which the temperature change becomes large in synergy with the change in the kneading temperature accompanying the temperature change of the compounding material for each batch. These will be corrected each time the batch is repeated, but this correction will take time. On the other hand, when making corrections between batches, the correction amount of liquefied gas ΔW
And the input amount W can be obtained by the following equation. ΔW = W ₀ × Δt / (T ₁ −T ₀ ) where Δt = (t ₁₁ + t ₁₂ + t ₁₃ ) / 3−t ₁₀ W = W ₀ + ΔW / 3

That is, the temperature change of the concrete is shown in FIG.
It can be seen as a change like the one-dot chain line in
This makes it possible to average variations and the like due to measurement for each batch, and to perform appropriate control.

The number of batches for performing the correction calculation may be the number of times of kneading. For example, the number of batches (concrete in the bogie) to be fed into a bogie for transporting concrete from a batcher plant to a casting site may be used. The temperature can be measured relatively easily and the measurement error is small). In this case, if the concrete temperature is regularly measured at the casting site, it is desirable to match the number of batches at the measurement interval. .

In the control of the third aspect, each temperature of the concrete compounding material immediately before the input of the mixer (actually, each temperature of the concrete compounding material immediately before the measurement in the batcher plant) is continuously measured for each batch. Of the concrete mixing temperature Pt _n is calculated from the measured values of the above, and the temperature difference ΔPt _n from the expected mixing temperature of the previous batch is calculated.
The liquefied gas supply amount is corrected by increasing or decreasing the amount of the liquefied gas in proportion to the ratio of Pt _n to the concrete temperature drop amount set at the start of the casting to control the concrete kneading temperature.

The concrete compounding material is mainly composed of aggregate, sand, cement and water. In addition, an admixture material is appropriately compounded, but the amount is small compared to the whole, and can be ignored because the change in heat capacity does not substantially affect the change in kneading temperature. These compounded ingredients are metered into the mixer from each batcher or water tank in the batcher plant, and the temperature at the time of charging is detected by a temperature sensor installed in each bottle or water tank, and this detected value is sent to the computer. Input.

[0025] That is, the temperature of each compounding materials just before turned measures First, the expectations kneading up temperature Pt _n concrete temperature after kneading in a mixer from the heat capacity of the measured values and the materials. The subscript n is the kneading batch number. W ₁ liquefied gas input amount of first when the set value of the kneading up temperature of the concrete to the target and T ₀ is given by equation (4). w and V are the basic unit of cooling and the kneading amount per batch as in the case of the formula (1). W ₁ = w × V × (Pt ₁ −T ₀ ) (4)

The actual measured value of the concrete kneading temperature after kneading is t _n , and the target setting range of the kneading temperature is T ₀ ±
x ° C. The liquefied gas input amount W _n of the n-th batch at this time, if the measured value t _n of the kneading up temperature of the concrete is setting range _i.e., when _{T 0 -x ≦ t n ≦ T} 0 + x, ( 5) Correction value of liquefied gas input amount ΔW according to equation
After calculating _n , this ΔW _n is calculated by adding the ΔW _n to the previous liquefied gas input amount W _n-1 according to the equation (6). ΔW _n = W _n−1 × (Pt _n −Pt _{n −1} ) / (Pt _n−1 −T ₀ ) (5) W _n = W _n−1 + ΔW _n (6)

That is, as shown in the equation (5), the expected kneading temperature Pt _{n is set} to the expected kneading temperature P of the previous n-1 batches.
t _n-1 , calculate the temperature difference, and calculate this temperature difference,
The ratio of the temperature difference between the previous predicted kneading temperature Pt _n-1 and the set value T ₀ is obtained, and the previous input amount W _n-1 is multiplied by this ratio to correct the liquefied gas input amount of the n-th batch. Find the value ΔW _n
, It sets the input amount W _n from the [Delta] W _n (claim 3).
This relationship is illustrated in FIG.

On the other hand, T ₀ −x> t _n or T ₀ +
If x <t _n , the actual measured value t _{n−1 of the} previous _n−1
Then, the correction value Δ of the liquefied gas input amount at the n-th time is obtained from the expression (7), and the liquefied gas input amount Wn is similarly set by the expression (6) (claim 4). ΔW _n = w × V × (t _n-1 −T ₀ ) (7) W _n = W _n-1 + ΔW _n (6)

According to the method of the third and fourth aspects, the temperature after the kneading is predicted from the temperature measurement value of the concrete compounding material before the kneading and is cooled to the target kneading temperature. As compared with the method of claim 1 in which the cooling temperature is controlled using the method, there is an advantage that the cooling temperature can be controlled without delay of the batch. Further, even if the expected value of the kneading temperature is different from the actual value due to various factors, a range of the allowable value x is provided for the target cooling temperature as described in claim 4, and only when the measured value deviates from this range. The deviation can be corrected by performing control using the actually measured value.
The tolerance x is measured in advance when the kneading temperature is measured, and a relatively stable control is possible by setting the range of the variation. The expected kneading temperature may be compared for each batch, but may be compared for a plurality of batches depending on the conditions of the plant at the site.

In the actual casting operation, even if concrete cooled to the target temperature is kneaded in the batcher plant, the concrete is transported to the site and cast when it is set between the kneading temperature and the casting temperature. Changes. The main factors are changes in waiting time and solar radiation. The waiting time can be made almost constant by managing the work procedure, but the change in the amount of solar radiation cannot be predicted.

Therefore, it is advantageous to measure the amount of solar radiation at all times, add the temperature rise due to the change in the amount of solar radiation to the kneading temperature in the plant, and reflect it in the setting of the liquefied gas input amount. Although the amount of temperature rise during transportation due to the amount of solar radiation varies depending on the transportation time and geographical conditions to the site, it is sufficient that the relationship between the two be experimentally grasped in advance.

Such control according to the present invention can be configured in an automatic control device by performing arithmetic processing on a commercially available personal computer or control device.

[0033]

As described above, according to the present invention,
In the pre-cooling method of concrete with liquefied gas, which has many fluctuation factors and is complicated to manage, the temperature of kneading can be controlled accurately, and by using this cooled concrete, the temperature crack of mass concrete can be reduced. It has an excellent effect that problems can be avoided.

[Brief description of the drawings]

FIG. 1 is a diagram showing actual measured values of a kneading temperature on a certain day when a pre-cooling is performed by determining a liquid nitrogen input amount from a cooling unit unit in a batcher plant at a certain dam construction site. .

FIG. 2 is an explanatory diagram for describing a mode of control according to the present invention.

FIG. 3 is an explanatory diagram for describing another mode of control according to the present invention.

FIG. 4 is an explanatory diagram for explaining still another mode of control according to the present invention.

Continuing on the front page (72) Inventor Keiichi Kobayashi Kashima Construction Co., Ltd. Kanto Branch, 6-3-2 Toyo, Koto-ku, Tokyo (72) Inventor Naoyuki Katayama 3-3 Mizue-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Toyo Oxygen Co., Ltd. (72) Inventor Yasushi Fukuda 3-3, Mizue-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Toyo Oxygen Co., Ltd. (72) Inventor Kazunobu Shibuya 3-3, Mizue-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture (58) Investigated field (Int. Cl. ⁷ , DB name) B28C 7/12 C04B 40/00

Claims (5)

(57) [Claims] 1. A liquefied gas is introduced into a mixer of a batcher plant to produce a cooled kneaded concrete in an almost constant amount for each batch, and the obtained kneaded material is conveyed to a concrete casting site and sequentially. When placing, first,
The required amount of liquefied gas input W using equation (1) at the start of casting
₀ (kg), W ₀ = w × V × (T ₁ −T ₀ ) (1) where W ₀ : Liquefied gas input (kg) w: Cooling unit (kg / m ³ ℃) ・ ・ Amount of liquefied gas required to cool 1 m ³ of concrete by 1 ° C. (value determined experimentally in advance) V: Amount of concrete kneaded in each batch (m ³ ) T ₁ : Concrete without liquefied gas Actual measured value of kneading temperature (° C.) T ₀ : target concrete kneading temperature (° C.) Next, this liquefied gas is charged at an input amount W ₀ (kg) and kneaded, and concrete kneading temperature t _{n is determined for} each batch. The temperature difference Δt from the previous batch is calculated from the measured value, and when this Δt exceeds the set range, the following (2)
The correction amount ΔW (kg) of the liquefied gas input amount is calculated based on the equation, and ΔW = W ₀ × Δt / (T ₁ −T ₀ ) (2) This correction value ΔW is expressed by equation (3). liquefied by increasing or decreasing the gas input amount W ₀ set the next input amount _{W 1, W 1 = W 0} + ΔW ··· (3) Thereafter, the next time to increase or decrease the correction amount [Delta] W to the corrected W _n to Concrete kneading temperature control method comprising setting the input amount of concrete. 2. The Δt is a kneading temperature t of the n-th batch.
_{2. The method according} to claim 1, wherein the difference is calculated from the difference between the average temperature of the concrete kneading temperature (tn _{+ 1,} tn _{+ 2,} tn _{+ 3} ...) of two or more successive batches. The control method described. 3. A liquefied gas is charged into a mixer of a batcher plant to produce cooled kneaded concrete for each batch, and the obtained kneaded material is transported to a concrete casting site and sequentially cast. In this case, the temperature of the concrete compounding material immediately before being charged into the mixer is measured for each batch, and the expected concrete mixing temperature Pt _n is calculated from these measured values, and the mixing temperature t _{n for} each batch is calculated.
The _measured, first, to determine the liquefied gas input amount W ₁ of the first through _{(4), W 1 = w × V ×} (Pt 1 -T 0) ···· (4) W 1: Initial liquefied gas Input amount (kg) w: Cooling basic unit (kg / m ³ ° C) ・ ・ Amount of liquefied gas required to cool 1 m ³ of concrete at 1 ° C (value obtained experimentally in advance) V: Amount of concrete to be kneaded (m ³ ) T ₀ : Target concrete kneading temperature (° C) Pt ₁ : Expected kneading temperature (° C) In the next batch and subsequent batches, _the previous measured kneading temperature t
Set _n-1 is the target concrete mixing up temperature T ₀ range T ₀
When the temperature is within the range of ± x ° C (x is an allowable value), the following equation (5)
Calculating a correction value [Delta] W _n of the liquefied gas input amount according _{to, ΔW n = W n-1} × (Pt n -Pt n-1) / (Pt n-1 -T 0) ··· (5) The correction amount From ΔW _n and previous liquefied gas input amount W _n-1
(6) liquefied gas input amount W _n to set _{a, W n = W n-1} + ΔW n ··· (6) concrete mixing up temperature control method according to claim according to formula. 4. A liquefied gas is charged into a mixer of a batcher plant to produce cooled kneaded concrete for each batch, and the obtained kneaded material is transported to a concrete casting site and sequentially cast. In this case, the temperature of the concrete compounding material immediately before being put into the mixer is measured for each batch, and from these measured values, the expected concrete mixing temperature Pt _n is calculated, and the mixing temperature t _{n for} each batch is calculated.
The _measured, first, to determine the liquefied gas input amount W ₁ of the first through _{(4), W 1 = w × V ×} (Pt 1 -T 0) ···· (4) W 1: Initial liquefied gas Input amount (kg) w: Cooling basic unit (kg / m ³ ° C) ・ ・ Amount of liquefied gas required to cool 1 m ³ of concrete by 1 ° C (value obtained experimentally in advance) V: Amount of concrete to be kneaded (m ³ ) T ₀ : Target concrete kneading temperature (° C) Pt ₁ : Expected kneading temperature (° C) In the next batch and subsequent batches, _the previous measured kneading temperature t
Set _n-1 is the target concrete mixing up temperature T ₀ range T ₀
When the value is out of the range of ± x ° C. (x is an allowable value), a correction value ΔW _n of the liquefied gas input amount according to the following equation (7) is calculated, and ΔW _n = w × V × (t _n−1 −T ₀ ) (7) from the correction amount [Delta] W _n and the previous liquefied gas input amount W _n-1
(6) liquefied gas input amount W _n to set _{a, W n = W n-1} + ΔW n ··· (6) concrete mixing up temperature control method according to claim according to formula. 5. The solar radiation of the day is continuously measured, and from this solar radiation, the temperature rise of the mashed concrete when transported from the batcher plant to the casting site is obtained by calculation, and this temperature rise is offset. Adding a liquefied gas input amount necessary for the correction to the ΔW _n as a correction amount.
5. The method for controlling the temperature of mixing concrete according to 2, 3, or 4.