JP2016037014A - Method for producing concrete molding and production management method for concrete molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an efficient method for producing a concrete molding and a production management method for the concrete molding, which enable initial strength upon demolding and long-term strength of the concrete molding to be predicted.SOLUTION: The method for producing a concrete molding comprises the steps of: (A) determining initial compression strength of a concrete molding; (B) setting a water-binder ratio of a concrete composition based on long-term compression strength; (C) charging concrete compositions selected in the set water-binder ratio into a form and heat-curing the concrete compositions under a plurality of heat curing conditions thereby obtaining integrated temperature or an effective material age, substituting integrated temperature or the effective material age upon production of the concrete molding into a compression strength estimation expression constructed based on a relationship between the integrated temperature or the effective material age and actually measured compression strength of the concrete molding, thereby calculating compression strength of the concrete molding; and (D) determining the water-binder ratio or the heat curing condition so that the calculated compression strength becomes equal to the initial compression strength set in the step (A) or more.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a concrete molded body obtained by performing heat curing using a mold, and a method for managing the production of a concrete molded body.

In recent years, a concrete molded body called a precast member is formed by using a plurality of molds and applied to various fields such as wall materials, structural materials, and decorative materials.
By preparing the concrete molded body in advance, the frequency of use of the concrete composition at a construction site or the like is reduced, which is useful for shortening the construction period.
The concrete compact is manufactured in a precast concrete factory. In general, in the manufacturing method, first, after curing a precast member in which a concrete composition is placed in a mold, the mold is removed the next day and the mold is cleaned. After cleaning, attach the reinforcing bars, formwork, and driving hardware of the precast member to be manufactured next, confirm that there are no problems in the pre-inspection, put the concrete composition into the formwork, and perform curing. The manufacturing method was performed.

The composition of the concrete composition used for the concrete molded body and the water binder ratio satisfy both the strength required at the time of demolding, the strength required at the time of shipment, and the design standard strength (long-term strength) as the final product. To be determined. On the other hand, the compressive strength at the time of demolding of the concrete molded body varies depending on the composition of the concrete composition, the water binder ratio, the temperature history that the concrete composition has undergone by heat curing in the mold, and the like. However, it is difficult to accurately measure the strength even if the core is taken from the concrete compact immediately after curing.
For this reason, conventionally, it is common to predict and evaluate the compressive strength with a concrete specimen of a fixed shape cured under the same conditions as the concrete compact. The concrete molded body to be produced and the specimen have different cross-sectional dimensions. Therefore, even if they are heated under the same conditions, the temperature history of the concrete is greatly different, and thus the compressive strength that is expressed is also different. Since the temperature history that the concrete composition receives in the mold varies greatly depending on the shape of the mold and the heat curing conditions, the compressive strength of the concrete molded body formed with an arbitrary mold can be determined by evaluating the compressive strength of the specimen. It was difficult to predict accurately.
For this reason, when determining the manufacturing conditions of a concrete molded body as a precast member, from the viewpoint of ensuring a certain quality, the water binder ratio of the concrete composition is reduced, the curing temperature is increased, The blending conditions and manufacturing conditions had to be set on the safe side, such as increasing the time.
In particular, when manufacturing several times a day using the same formwork, there is a strong tendency that the strength cannot be accurately grasped, and it must be set to a safer side, from the viewpoint of manufacturing efficiency and energy saving. In concrete molded bodies, there has been a demand for a method for predicting accurate initial strength and long-term strength regardless of the shape of the formwork.

As an efficient manufacturing method for precast members, a planar heating element that conducts heat via an electric heating material is provided on the lower surface of a heat-conducting formwork for placing concrete, and a plurality of heating maximum temperatures and heating rates are set in advance. Specimens were prepared for each specimen, the compressive strength of each specimen was determined, and the required compressive strength was determined during actual production using the relational expression derived from the relative relationship between the accumulated temperature and compressive strength. There has been proposed a method of performing energization control on a planar heating element so as to obtain the integrated temperature obtained by substituting it into the relational expression (for example, see Patent Document 1).
In addition, a method for producing a cured body using a hardening accelerator for hydraulic materials that exhibits a compressive strength that can be removed in a short time and then develops sufficient strength over time has been proposed (for example, patents). Reference 2).

JP 09-174532 A JP 2014-19618 A

However, in the manufacturing method described in Patent Document 1, although attention is paid to the integrated temperature during actual manufacturing, the shape of the formwork is limited, and the relational expression is also a logarithmic function. However, it has not yet been possible to set conditions for expressing the initial strength of a concrete compact.
In addition, although the manufacturing method described in Patent Document 2 achieves a certain degree of efficiency, there is a problem that the blending of the hydraulic material is defined and the versatility is low. Moreover, the method described in Patent Document 2 does not predict conditions for expressing desired initial strength and long-term strength in a concrete molded body, and does not take into account optimization according to the purpose.

An object of the present invention is to accurately predict the initial compressive strength and long-term compressive strength of a concrete molded body required at the time of demolding in a concrete molded body produced by heat curing, regardless of the shape of the formwork. An object of the present invention is to provide an efficient method for producing a concrete molded body under optimum production conditions.
Another object of the present invention is to provide a highly productive concrete molded body by accurately predicting the initial compressive strength and long-term compressive strength of the concrete molded body required at the time of demolding regardless of the shape of the formwork. It is to provide a manufacturing management method.

Hereinafter, the present invention will be described in detail.
In this specification, the numerical range indicated using “to” indicates a range including the numerical values described before and after “to” as the minimum value and the maximum value, respectively.
In the present specification, the amount of each component in the composition is the total amount of the plurality of substances present in the composition unless there is a specific indication when there are a plurality of substances corresponding to each component in the composition. means.
In this specification, the word “process” is included in this term as long as the intended purpose of this process is achieved even when the process is not clearly distinguished from other processes.
In this specification, the wording of a concrete molded object and a concrete composition includes the mortar molded object and mortar composition which contain only a fine aggregate, and the cement molded object and cement composition which do not contain an aggregate. Used in meaning.

  As a result of intensive studies, the present inventors have determined "demolding and long-term compressive strength" from the shape of the mold of the concrete molded body and the desired compressive strength, and from the internal temperature history received by the concrete composition A compression strength prediction formula that is a formula for predicting the initial compressive strength from the calculated integrated temperature and the water binder ratio that is the blending condition is created in advance, and using the obtained compressive strength prediction formula, Estimate the internal temperature history of the concrete composition from the heat curing temperature, and put the concrete composition with the prescribed blending conditions that satisfy both the initial compressive strength and the long-term compressive strength at the time of demolding into the formwork, or heat The inventors have found that the above problems can be solved by determining curing conditions, and have completed the present invention.

The configuration of the present invention is as follows.
<1> A method for producing a concrete molded body in which a concrete composition is molded in a mold, wherein the compression strength necessary for demolding is determined in consideration of the shape of the concrete molded body to be produced (A) From the long-term compressive strength required for the concrete molded body, the step (B) of setting the range of the water binder ratio of the concrete composition, selected within the range of the water binder ratio set in the step (B), A plurality of concrete compositions having different water binder ratios are put into molds of respective assumed dimensions, and heat-cured under a plurality of heat-curing conditions. The accumulated temperature obtained from the temperature time history, the effective age, or (b) the temperature obtained by unsteady heat conduction analysis using at least one of the heating curing condition and the measured curing temperature. Each concrete with an integrated temperature or effective age determined from the time history of the internal temperature of the clay composition, and (a) a temperature history obtained by actual measurement or (b) a temperature history obtained by unsteady heat conduction analysis A concrete specimen made of the composition is produced, the compressive strength of the produced concrete specimen is obtained, and the compressive strength prediction formula constructed from the relationship between the integrated temperature or effective age and the water binder ratio of the concrete composition is used. The concrete molded body is obtained by substituting the integrated temperature or effective age obtained by the heat curing temperature and the heat curing time, which are the heat curing conditions actually performed at the time of manufacturing the concrete molded body, into the compressive strength prediction formula. The step (C) for calculating the compressive strength of the concrete assembly so that the compressive strength calculated in the step (C) is equal to or higher than the compressive strength set in the step (A). The step of determining at least one of water binder ratio and heating curing conditions of the object (D), a method for producing a concrete molded body containing.

<2> In the unsteady heat conduction analysis in the step (C), using the coefficient related to the heat insulation temperature rise rate of the concrete composition corrected according to the amount of heat transferred to the concrete composition by the heat curing conditions, the concrete in the mold Estimating the temperature distribution of the composition, determining the heat curing conditions, depending on the coefficient of the heat insulation temperature rise rate of the concrete composition corrected according to the amount of heat transferred to the concrete composition by the heat curing conditions and the distance from the surface Estimating the temperature distribution of the concrete composition in the mold using the corrected specific heat, determining the heat curing conditions, and heat insulation of the concrete composition corrected according to the amount of heat transferred to the concrete composition by the heat curing conditions Using the coefficient for the rate of temperature rise, the temperature distribution and strength distribution of the concrete composition in the formwork Estimated, timing removal of appropriate formwork of the concrete molded body is a method for producing a concrete molded body according to <1> includes at least one of determining the timing lifting.

<3> To compare the compressive strength set in step (A) with the result of compressive strength calculated by the compressive strength prediction formula obtained in step (C) to obtain the required compressive strength when demolding the concrete compact. The water composition ratio of the concrete composition and the heat curing conditions so that the total cost of the material cost determined from the water binder ratio of the concrete composition and the energy cost for outputting the integrated temperature is minimized. It is the manufacturing method of the concrete molded object as described in <1> or <2> which further includes the process (E) which determines these.

<4> A method for manufacturing and controlling a concrete molded body in which a concrete composition is molded in a mold, and determining a compressive strength necessary for demolding in consideration of the shape of the concrete molded body to be manufactured (A2) A plurality of concrete compositions having different water binder ratios selected within the range of the water binder ratio set in the step (B2) are put into the molds of the assumed dimensions, (A) the accumulated temperature obtained from the time history of the internal temperature of each concrete composition measured, or the effective age, or (b) at least the heat curing conditions or the measured curing temperature. The accumulated temperature or effective age obtained from the time history of the internal temperature of the concrete composition obtained by unsteady heat conduction analysis using either, and (a) obtained by actual measurement. Or, (b) a concrete specimen made of each concrete composition is manufactured with the temperature history obtained by unsteady heat conduction analysis, the compressive strength of the produced concrete specimen is obtained, and the integrated temperature or effective material is obtained. Using the compressive strength prediction formula constructed from the relationship between the age and the water binder ratio of the concrete composition, it is obtained at the heating curing temperature and heating curing time, which are the heating curing conditions that are actually implemented at the time of manufacturing the concrete molded body. The step (C2) of calculating the compressive strength of the concrete molded body by substituting the integrated temperature or effective age into the compressive strength prediction formula, and the compressive strength set in the step (A2), and the step (C2) The result of the compressive strength calculated in step (C2) is the same or greater than the compressive strength set in step (A2). Is a manufacturing management method for a concrete molded body, which includes a step (D2) of confirming that the concrete molded body can be demolded.

<5> In the step (C2), the temperature history of the concrete composition in the mold is driven into the mold using the concrete composition, heat curing is performed, and the temperature of the concrete composition inside the mold This is a method for manufacturing and controlling a concrete molded body according to <4>, which is obtained by actually measuring.

According to the present invention, in a concrete molded body produced by heat curing, the initial compressive strength and long-term compressive strength of the concrete molded body required at the time of demolding can be accurately predicted regardless of the shape of the mold. Therefore, it is possible to provide an efficient method for producing a concrete molded body under optimum production conditions.
In addition, according to the present invention, regardless of the shape of the formwork, the initial compressive strength of the concrete molded body required at the time of demolding and the long-term compressive strength are accurately predicted, so that the highly productive concrete molded body A manufacturing management method can be provided.

According to the production method and the production management method of the present invention, in the concrete composition in the mold, it is possible to accurately estimate the thermal history and strength distribution for each part of the compressive strength, This is useful for optimizing the construction cycle.
In addition, the concrete molded body produced under appropriate heat curing conditions exhibits optimum strength, and according to the present invention, the optimum blending conditions and heat curing conditions are determined regardless of the shape of the concrete molded body. It is possible to provide an efficient method for producing a concrete molded body and a production management method.

It is the graph which described the temperature distribution after the heat curing for 3 hours according to the distance from a heating surface supposing the heat curing temperature of 5 steps | paragraphs of 20-95 degreeC. It is the graph which identified the alpha value of the concrete composition based on the experimental result, and plotted by the distance from a heating surface. It is a graph which shows the relationship between the correction coefficient of (alpha) value obtained in FIG. 2, and temperature. It is a graph which shows three kinds of curing patterns (curing pattern A: thin member center, curing pattern B: thick member center, curing pattern C: thick member surface layer) in the first example of constructing the compressive strength prediction formula. (A)-(C) are graphs which show the relationship between the age rating scale of various concrete compositions used for evaluation and compressive strength. It is a graph which shows the relationship between each coefficient a and b of each regression equation shown in Drawing 5 (A)-Drawing 5 (C), and binder water ratio. It is a graph which shows the correspondence of the compressive strength obtained by the member strength experiment and the compressive strength estimated value of material age 3 hours and 4.5 hours calculated | required from the compressive strength prediction formula. It is a graph which shows three kinds of curing patterns (curing pattern A: thin member center, curing pattern B: thick member center, curing pattern C: thick member surface layer) in the second example of the compression strength prediction formula construction. It is the approximate curve calculated | required by the least squares method from the relationship between the integrated temperature (40 degreeC reference | standard) and the compressive strength of the concrete molded object in the 2nd example of compression strength prediction type | formula construction. It is a graph which shows the relationship between the estimated value of the compressive strength calculated | required using the compressive strength prediction formula constructed | assembled from the approximate curve in FIG. 9, and the measured value of compressive strength. It is a graph which shows two patterns of the heat curing temperature applied in the Example.

<Method for producing concrete compact>
Hereinafter, the manufacturing method of this invention is demonstrated in order of a process.
[Step (A): A step of determining the compressive strength required at the time of demolding in consideration of the shape of the concrete compact to be produced]
First, the compressive strength required at the time of demolding is determined from the weight and usage of the concrete molded body in consideration of the shape of the concrete molded body to be manufactured. Specifically, the hook attachment position at the time of demolding, the compressive strength at the hook attachment position where the concrete molded body can be held by the hook, and the initial compressive strength to withstand suspension are set.

[Step (B): Setting the range of the water binder ratio of the concrete composition from the long-term compressive strength required for the concrete compact]
Determine the long-term compressive strength of the concrete compact in consideration of the purpose of use, shape, etc. of the concrete compact, mix the concrete composition for forming the concrete compact that can achieve the determined long-term compressive strength, water binder ratio Set the range. Since the long-term compressive strength of the concrete molded body depends on the composition of the concrete composition, particularly the water binder ratio, the water binder ratio necessary for the expression of the long-term compressive strength is set. In the present invention, it is assumed that the concrete is heat-cured, and the long-term compressive strength is evaluated with a concrete composition subjected to heat-curing. Usually, the highest water binder ratio that can develop long-term strength is set.

[Step (C): A plurality of concrete compositions having different water binder ratios selected within the range of the water binder ratio set in step (B) are placed in the molds of the assumed dimensions. And heat curing under a plurality of heat curing conditions, (a) the integrated temperature obtained from the time history of the internal temperature of each concrete composition measured, or the effective age, or (b) the heat curing conditions or The accumulated temperature or effective age obtained from the time history of the internal temperature of the concrete composition obtained by unsteady heat conduction analysis using at least one of the measured curing temperatures, and (a) obtained by actual measurement, or ( b) With the temperature history obtained by unsteady heat conduction analysis, concrete specimens made of each concrete composition were produced, and the compressive strength of the produced concrete specimens was determined. Therefore, using the compressive strength prediction formula constructed from the relationship between the accumulated temperature or effective age and the water binder ratio of the concrete composition, the heat curing temperature that is the heat curing condition that is actually implemented during the production of the concrete compact And calculating the compressive strength of the concrete compact by substituting the accumulated temperature or effective age obtained in the heat curing time into the compressive strength prediction formula]
In step (C), a predetermined heat curing history is determined using the concrete composition of the determined composition, and the history of heat curing conditions and the time history of the measured internal temperature of the concrete composition are determined. Or the manufacturing conditions of a concrete molded object are determined using the compression strength prediction formula which calculated | required and constructed | assembled the compressive strength of the concrete molded object using the integrated temperature calculated | required from the temperature history calculated by unsteady heat conduction analysis.
In step (C), in order to build a highly accurate compressive strength prediction formula, ideally, the water binder ratio of the concrete composition should be evaluated as 3 levels, the curing history temperature as 3 levels, and the age as 2 levels. Each is preferably performed. Based on these measured or estimated values, consider the upper limit of the heating temperature condition and the upper limit of the heating time determined from manufacturing and quality constraints, and combine the integrated temperature and water binder ratio for the required strength. This can be used to determine at least one of the water binder ratio of the concrete composition and the heat curing conditions that are optimal for the production of the concrete compact.

Here, the effective age is obtained by evaluating the difference in reaction rate due to the difference in temperature by the Arrhenius rule, and obtaining the equivalent age from the total reaction amount based on the reaction amount per day at a constant 20 ° C. Using the Arrhenius prediction formula for the chemical reaction rate depending on the temperature, k = A · exp (−E / (R · T)), the ratio of the reaction rate at 20 ° C. at X ° C. is as follows:
_{k X / k 20 = exp (} E / (R · 293) -E / (R · T))
= Exp (13.65-4000 / T)
In the above formula, k represents a reaction rate constant, A represents a constant (frequency factor) independent of temperature, and E represents activation energy (also called Arrhenius parameter). R is a gas constant and T represents an absolute temperature [K].
By multiplying the reaction rate ratio by the temperature duration time and taking the total, an effective age considering the amount of reaction for a constant 20 ° C. can be obtained.
In the following formulas, t _e is the effective ages (day), Delta] t _i is the time (days) for the temperature T continues, T (Delta] t _i) is the concrete continues for Delta] t _i Temperature (℃) , T ₀ is a value that makes the material age dimensionless and represents one day.

  The characteristic value of the adiabatic temperature rise amount of the reference concrete composition can be obtained by the coefficient of thermal insulation temperature rise test represented by the following formula (1). Moreover, it can also determine based on the well-known literature etc. regarding a reliable concrete composition.

Formula (1)

In said formula (1), T (t) represents the temperature (degreeC) in the age t, and K represents the ultimate value (degreeC) of the heat insulation temperature rise. α represents a constant (1 / day) related to the rate of increase in adiabatic temperature, and t ₀ represents a setting time (heat generation start time) (day).

Next, the characteristic value (α value) obtained in (1) is corrected according to the heat curing conditions.
Ignoring the hydration heat of concrete, it is possible to calculate how heat is transferred from the outside to the concrete by heat curing.
FIG. 1 shows the temperature distribution after heating curing for 3 hours, arranged in terms of the distance from the heating surface, assuming five stages of heating curing temperature of 20 to 95 ° C. It can be said that the heat supply from the outside is about 20 cm from the surface at a material age of about 3 hours. That is, heat is not transmitted at a position 20 cm or more away from the heating surface. From this, the concrete located deeper than 20cm shows the heat generation characteristics of normal concrete without heat curing, and since the surface side receives a high temperature history before setting, the characteristic value of the concrete may change greatly. is assumed.
In addition, at the age of 3 hours, the concrete before the setting and the target concrete has a lot of free water, and the specific heat is assumed to be close to “water”. As a result of performing and evaluating the experiment several times by these inventors, the specific heat of the concrete from the heating surface to 5 cm is treated as 4.0 to 5.2 kJ / kg ° C., and the measured values are reproduced. I found out that I can. In a general-purpose concrete composition, the specific heat of the concrete from the heating surface to 5 cm is preferably estimated as 4.0 to 5.2 kJ / kg ° C, and more preferably estimated as 4.6 kJ / kg ° C. By using such an estimated value, evaluation can be performed more simply.

The coefficient α value related to the rate of increase in adiabatic temperature of a concrete composition that is subjected to heat curing before setting is different from that of general concrete.
FIG. 2 identifies the α value of the concrete composition based on the experimental results and arranges them according to the distance from the heating surface. The closer to the surface and the higher the heating temperature, the greater the α value. Since this relationship shows the same tendency as the temperature distribution excluding the hydration heat generation shown in FIG. 1, the correction value of the α value can be made into a function by arranging both.
In general, in the one-dimensional heat conduction equation, when the density of a substance is ρ, the specific heat is c, and the thermal conductivity is λ, the elapsed time t and the temperature T of the substance at the position x are expressed by the following formula (2). .
If the internal temperature of the concrete is Ti and the surface temperature is Ts as boundary conditions, the following equation (2) can be corrected to the following equation (3) using an error function.
The concrete surface temperature Ts and the heating temperature Ta in the following formula (3) can be simply calculated from the following formula (4) and the following formula (5) by linearly approximating the analysis result by the finite element method.
FIG. 3 is obtained by plotting the relationship between T in the following formula (3) and the α value in FIG.
The α value correction coefficient η is expressed as a multiplier of the α value that is not corrected. When the corrected α value is α _c , the following expression (6) is obtained.

Formula (2)

Formula (3)

Formula (4)

Formula (5)

Formula (6)

  With the above procedure, the temperature history of the target concrete composition can be estimated by unsteady heat conduction analysis. If the result does not satisfy the required performance, it is possible to review and optimize the mixing condition of the concrete composition and the heat curing condition in consideration of the shape of the concrete compact. In this method, in order to correct the characteristic value of the adiabatic temperature rise, the characteristic value of the adiabatic temperature rise of the concrete composition may be obtained in advance. It also has the advantage that it is not specified by type.

Next, using the estimated temperature history of the concrete composition and the integrated temperature estimated in consideration of the size and shape of the concrete compact, that is, the formwork, the compressive strength of the concrete compact at the time of demolding is calculated. Build the desired compression strength prediction formula.
In step (C), the compressive strength of the concrete compact can be calculated using the constructed compressive strength prediction formula.

  In addition, the integrated temperature Di (° C./hour) of the age of material i is the temperature T (° C.) and the time t (hour) when the heating period t (hour) is heated as the heat curing. Is a value generally represented by the following formula (D). In addition, +10 in the formula is based on the knowledge that a hydration reaction occurs if concrete is −10 ° C. or higher, and this value is generally used, but depending on the literature, it is −5 ° C. Some have 0 ° C.

Formula (D)

  The compressive strength prediction formula is constructed in consideration of the blending conditions of the concrete composition, the water binder ratio, and the shape of the formwork.

An example (hereinafter referred to as the first example) of the construction of the compressive strength prediction formula is shown below.
First, assuming a thin member (thickness: 200 mm) and a thick member (thickness: 1000 mm) as the mold, the center of the thin member (100 mm from the surface) and the center of the thick member (500 mm from the surface) are used as the heat curing pattern. And the temperature at the time of heat curing was examined on the assumption of 100 mm from the surface of the thick member. The kneading temperature of the concrete composition was set to 35 ° C.
The temperature history given to the concrete specimen (center part) is shown in FIG. 4 based on the temperature measurement result of the simulated member (curing pattern A: center of thin member, curing pattern B: center of thick member, curing pattern C) : 100 mm from the surface of the thick member).

In concrete molded bodies such as precast members, heat curing is performed from the beginning in order to improve workability. On the other hand, according to the study by the present inventors, when the temperature reaches 40 ° C. after 3 hours of heating, the concrete composition having a standard water binder ratio of about 30 to 50 has a compressive strength of 1.5 N / mm. It has been confirmed that it is ² or more and is cured. From this examination result, in the present invention, it is assumed that the time when the temperature of the concrete composition has increased to 40 ° C. is the curing start time, and 40 ° C. is the reference integrated temperature (the area of the temperature history exceeding 40 ° C.) Was examined as an age rating scale.
Then, based on the experimental data, the compression strength prediction formula of the initial age was obtained from the evaluation scale of each age and the water binder ratio by the least square method. The compressive strength was estimated from the temperature history and the water binder ratio of the same specimen and member temperature following specimens in the actual machine manufacturing experiment. Moreover, the compressive strength was measured and the estimated result of the estimated compressive strength was verified.

FIG. 5A to FIG. 5C show the relationship between various age rating scales and compressive strength. The approximate curves are also shown in the figure. The logarithmic expression was obtained when the accumulated temperature based on −10 ° C. and the effective age were used as the material age evaluation scale.
6 (A) and 6 (B), the regression equations Y = a · ln (X) + b and Y = a · ^Xb shown in FIGS. 5 (A) to 5 (C) are shown. The relationship between the coefficients a and b and the binder water ratio is shown. Both coefficients are close to the linear relationship with the binder water ratio.
Based on these results, the coefficient was determined by the least square method with respect to the relationship between the water binder ratio, various age rating scales, and compressive strength in the form of the following formula (7) or formula (8). The determined coefficients are shown in Table 1.

  The compression strength prediction formula is shown below.

Formula (7)
Formula (8)

In said Formula (7) and Formula (8), (sigma) represents compressive strength (N / mm < ² >) and C / W represents the binder water ratio of a concrete composition. X represents an integrated temperature [temperature (° C.) · time (hr)] or effective age (days). α, β, γ, and δ are coefficients.

FIG. 7 shows the correspondence relationship between the compression strength estimated values obtained at the age of 3 hours and 4.5 hours obtained from the compression strength prediction formula using the effective age and the compression strength obtained in the member manufacturing experiment.
When the water binder ratio was 30%, the variation was large regardless of which scale was used. In the region where the water binder ratio is small, it is considered that the difference in strength expression due to the difference in temperature history is very large. In the case of the water binder ratio of 40% and 50%, any of the compressive strength prediction formulas corresponds well with the actual measurement value.

Next, another example (hereinafter referred to as a second example) of constructing a compressive strength prediction formula will be shown.
The mold is assumed to be a thin member (thickness 200 mm) and a thick member (thickness 1000 mm), and the heat curing pattern is a thin member that is expected to have a relatively rapid temperature rise in consideration of the production of a precast member. Center (100mm from the surface: Center temperature when two-stage curing of 45 ° C → 80 ° C is performed on a thin member of 200mm thickness) and 100mm from the surface of the thick member (thick member surface layer: 90 ° C curing on a thick member of 1000mm thickness) The temperature at the time of heat curing was examined assuming a temperature of 100 mm from the surface layer in the case of carrying out the above. The kneading temperature of the concrete composition was set to 20 ° C.
Similar to the first example, the concrete composition was evaluated at a water binder ratio of 30, 40, and 50.
In the second example, the temperature history given to the concrete specimen (center) is shown in FIG. 8 based on the temperature measurement result of the simulated member (curing pattern A: center of thin member, curing pattern B: thick member) Center (the center temperature when 90 ° C. curing is applied to a 1000 mm thick member), curing pattern C: 100 mm from the surface of the thick member), but in the second example, as described above, The example of temperature rise was assumed and the subsequent examination was performed only about curing pattern A (thin member center) and curing pattern C (thick member surface layer).
Temperature follow-up curing was performed using the temperature history of the center of the thin member and the surface of the thick member obtained in a previous experiment.

After the follow-up curing was completed (3 hours after water injection), the specimen was taken out from the curing tank, transferred to a simple thermal insulation curing tank, and cured to a predetermined test material age.
The temperature obtained from the thermocouple installed inside the specimen was measured to detect the temperature history, and the compressive strength of each specimen at a predetermined age was measured until the specimen age.
From the initial compressive strength test result of the specimen subjected to follow-up curing and the temperature history, the relationship between the integrated temperature D _{40 based on} 40 ° C. and the compressive strength was plotted, and the graph shown in FIG. 9 was obtained.
From the graph shown in FIG. 9, it can be seen that the strength changes depending on the water binder ratio.

  With respect to the graph shown in FIG. 9, the relationship between the water ratio of the binder, the integrated temperature, and the compressive strength is expressed by the following formula (logistic formula used for estimating the strength of concrete at the time of mold removal, that is, initial strength: 9).

In the curing pattern A and curing pattern C in which the temperature rise is relatively rapid, and in the curing pattern B in which the temperature rise is relatively moderate, it is expected that the strength expression is different even if the same temperature history is received. If the coefficients a to f are determined by the least square method so that the error between the experimental value and the estimated value is determined as a compression strength prediction formula for the curing pattern A and the curing pattern C, the curing patterns A and C are determined. The compression strength prediction formula is as shown in the following formula (10 _AC ).

The approximate curve obtained from the above equation (10 _AC ) is shown in FIG.
FIG. 10 shows the relationship between the estimated value of the compressive strength expected from this approximate expression and the actually measured value obtained by actually measuring the compressive strength. From the graph shown in FIG. 10, it can be seen that the compressive strength predicted by the compressive strength prediction formula agrees well with the actually measured value.

From these results, in the first example, when the water binder ratio is 40% and 50%, the temperature history in the concrete member can be predicted by this process when the integrated temperature based on 40 ° C. is used. I understand. In addition, in the second example, when the integrated temperature based on 40 ° C. is used in any of the water binder ratios of 30%, 40%, and 50%, this process allows the temperature history and expression in the concrete member. It can be seen that the compressive strength can be predicted.
For this reason, it is possible to accurately estimate the compressive strength of a concrete molded body at an arbitrary position. As a result, setting of the water binder ratio to obtain the required demolding strength, actual measurement or estimation of the temperature history in the molded body. Therefore, it is considered possible to manage the strength during demolding and lifting.

[Step (D): Determine at least one of the water binder ratio and the heat curing condition of the concrete composition so that the compressive strength calculated in the step (C) is equal to or higher than the compressive strength set in the step (A). Process)
As a result of the verification, it can be seen that the compressive strength calculated using the compressive strength prediction formula constructed in the step (C) is in good agreement with the actual measurement value in consideration of the blending conditions of the concrete composition.
For this reason, the compression strength set in step (A) and the compression strength result calculated by the compression strength prediction formula in step (C) are compared, and the compression strength result calculated in step (C) is the step (A). It is possible to determine at least one of the water binder ratio and the heat curing condition, which are the blending conditions of the concrete composition to be evaluated, so as to exceed the set value. Further, by using a concrete composition with a determined water binder ratio, or by producing a concrete molded body by performing at least one of applying the determined heat curing conditions to the production of a concrete molded body, It can be confirmed that the demolding strength is achieved. For this reason, for example, it is possible to produce concrete molded bodies under conditions set according to various requirements such as demolding in a short time, heating at a low temperature, and keeping the water binder ratio of the concrete composition low. Highly implemented.

  According to the method for producing a concrete molded body of the present invention, since the initial strength of a concrete molded body that can be demolded in a short time can be estimated accurately, the mixing condition of the concrete composition optimal for mass production of the concrete molded body, heating The suitability of the curing conditions can be confirmed, and an efficient concrete molded body can be produced.

The method for producing a concrete molded body of the present invention may further include an optional step in addition to the steps (A) to (D) described above.
For example, in the step (D), when the compressive strength set in the step (A) exceeds the result of the compressive strength calculated in the step (C), at least one of the blending condition of the concrete composition and the heat curing condition However, in this case, the optimum condition can be easily found by performing the above step (C) again while changing the condition.

[Step (E): a concrete composition for comparing the compressive strength set in step (A) with the compressive strength calculated in step (C) to obtain the required compressive strength when demolding the concrete compact The water binder ratio of the concrete composition and the heat curing conditions are determined so that the total cost of the material cost determined from the water binder ratio and the energy cost for outputting the integrated temperature is minimized. Process)
In the production method of the present invention, the step (E) can be performed for the purpose of further minimizing the cost.
In the step (E), the range of material costs determined from the range of the composition of the concrete composition for obtaining the compressive strength required at the time of demolding of the concrete molded body determined from the water binder ratio, Calculate the energy cost range for outputting the integrated temperature necessary to obtain the required compressive strength at the time of demolding, and the water binder ratio of the concrete composition and heat curing so that these costs are minimized. Conditions can be determined. By taking this into consideration, such as the type of material used in the concrete composition, the water binder ratio, the energy of the heating device used for heating, the integration of the heating temperature and the heating time, etc., the demolding set in step (A) The cost for achieving the necessary compressive strength can be minimized, the optimum range can be estimated not only for the efficiency in the production method but also for the cost, and the optimum method for producing a concrete compact can be selected.

(Concrete composition)
There is no restriction | limiting in particular in the mixing | blending of the concrete composition applied to the manufacturing method of the concrete molding of this invention, All can be applied to the mixing conditions of a general concrete composition.
Considering efficient production of the precast member, the effect of the present invention is remarkably applied to a concrete composition having a high initial strength.
From such a viewpoint, water containing 10% by mass to 30% by mass of inorganic sulfate, 10% by mass to 70% by mass of calcium sulfoaluminate, and 10% by mass to 30% by mass of inorganic hydroxide. It is preferable to use a concrete composition containing a hardening accelerator for a hard material.
More specifically, a hydraulic material containing 10% by mass to 30% by mass of inorganic sulfate, 10% by mass to 70% by mass of calcium sulfoaluminate, and 10% by mass to 30% by mass of inorganic hydroxide. The effect of this invention is remarkable by using the concrete composition which contains 2-10 mass parts of hardening accelerators for hydraulic materials with respect to the curing accelerator for hydraulic materials and 100 mass parts of hydraulic materials. The concrete composition using the specific curing accelerator for a hydraulic material that is preferably used in the present invention is described in detail in Japanese Patent Application Laid-Open No. 2014-19618 previously proposed by the present applicants, The hydraulic composition described herein can be suitably used in the production method of the present invention and the production management method of the concrete molded body of the present invention described later.

<Manufacturing management method of concrete compact>
The production control method for a concrete molded body of the present invention is a method for manufacturing a concrete molded body in which a concrete composition is molded in a mold, and is necessary at the time of demolding in consideration of the shape of the concrete molded body to be manufactured. A plurality of concrete compositions having different water binder ratios selected within the range of the water binder ratio set in the step (A2) and the step (B2) of determining the appropriate compressive strength and (A) the integrated temperature obtained from the time history of the internal temperature of the concrete composition measured, or the effective age, or ( b) Integration obtained from the time history of the internal temperature of the concrete composition obtained by unsteady heat conduction analysis using at least one of the heat curing conditions and the measured curing temperature The concrete specimens made of the respective concrete compositions were manufactured with the temperature or the effective age and (a) the actual measurement or (b) the temperature history obtained by the unsteady heat conduction analysis. Obtain the compressive strength of the concrete specimen, and use the compressive strength prediction formula built from the relationship between the accumulated temperature or effective age and the water binder ratio of the concrete composition, and the actual heating performed during the production of the concrete compact Step (C2) of calculating the compressive strength of the concrete molded body by substituting the integrated temperature or effective age obtained in the heat curing temperature and the heat curing time as curing conditions into the compression strength prediction formula The compression strength calculated in step (C2) is compared with the compression strength set in step (A2) by comparing the compression strength set in (A2) with the result of compression strength calculated in step (C2). If the result is the same, or by greater than, the step of confirming that the concrete molded body can be demolded (D2), a production control method of the concrete molded body containing.

In the production management method of the present invention, the temperature history in the mold of the concrete composition necessary for constructing a compression strength prediction formula for obtaining the compression strength of the concrete molded body at the time of demolding in the step (C2) is calculated. Alternatively, it may be obtained by driving into a mold using a concrete composition, performing heat curing, and actually measuring the temperature of the concrete composition inside the mold.
By further including the step of obtaining the temperature history by actually measuring the temperature in the mold, it is possible to accurately predict the temperature history by measuring the temperature once, and the present invention is applied to a concrete composition having similar blending conditions. When the manufacturing management method is applied, more accurate manufacturing management can be performed.

  Specifically, the step (A2), the step (B2), and the step (C2) in the production management method of the present invention are specifically the steps described in detail in the method for producing a concrete molded body of the present invention described above ( It can carry out similarly to A), a process (B), and a process (C).

  According to the method for manufacturing and controlling a concrete molded body of the present invention, the initial strength of a concrete molded body that can be demolded in a short time can be estimated with high accuracy using a concrete composition having a predetermined blending condition. It is possible to confirm the suitability of the heat curing conditions of the concrete composition that is optimal for mass production of molded products, without the need for excessive blending conditions and heat curing conditions, and the production of defective products due to defective demolding, etc. is suppressed, producing It is possible to manage the production of highly compacted concrete bodies.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not restrict | limited to these description.
Example 1
A formwork of length 4100 mm × width 1300 mm × thickness 140 mm was prepared. The compressive strength required at the time of demolding the mold was determined to be 10 N / mm ² in consideration of the mass of the concrete compact [step (A)].
The mold was covered with a heat insulating material other than the heating surface by heat curing.

In consideration of the long-term compressive strength of the concrete compact, a concrete composition having the following composition was used [step (B)].
(Concrete composition mix)
165kg / m ^{3 of} water
Cement 413kg / m ³ (Early strength Portland cement, Taiheiyo Cement)
Fine aggregate 757kg / m ³ (crushed sand from Ugawa river and Fujiwara mine)
Coarse aggregate 979kg / m ³ Hokusei-cho crushed stone)
Water reducing agent 1.239 kg / m ³ (High performance water reducing agent, Takemoto Yushi Co., Ltd., Tupole NV-G5: trade name)
Water binder ratio: 38.0%

  A concrete composition having the above-mentioned composition was prepared, placed in a mold covered with a heat insulating material other than the heated surface by heat curing, heating was started, and the temperature inside the concrete was measured with a thermocouple.

<Heating conditions>
Heat curing starts 30 minutes after hydration and allows the maximum temperature to be reached. The maximum temperature is maintained for 3 hours after the addition of water, and then the heat curing is terminated. The maximum temperature was 95 ° C for pattern 1 and 65 ° C for pattern 2. FIG. 11 shows two patterns of the heat curing temperature applied in this embodiment.

Estimate the temperature of the concrete composition in the formwork at the position of a depth of 100 mm from the surface using the formulas (1) to (5) by the method described in the step (C). Calculated. Furthermore, the calculation of the estimated value with higher accuracy was attempted by using the correction value (6).
This estimated value was compared with the actual value measured with the thermocouple.

  First, in the concrete composition heated by the heat curing pattern 1, in Example 1 in which the α value of the characteristic value of the adiabatic temperature rise is corrected based on the step (C) in the production method of the present invention, the distance from the heating surface is 100 mm. The accumulated temperature up to 3 hours of age was calculated as 135.8 ° C · h. The measured value was 143.6 ° C. · h, and the error of the integrated temperature was −5.4%, which was within 10%, and the measured value was accurately reproduced. Furthermore, when the formula (6) constructed to correct the α value of the characteristic value of the adiabatic temperature rise and the specific heat based on the present invention is applied, the obtained value is 139.1 ° C. · h. The measurement error was -3.1%, the error of the integrated temperature was within 5%, and the actual measurement value was accurately reproduced.

(Example 2)
Next, the integrated temperature was estimated and the integrated temperature was compared with the experimental value (actually measured value) in the same manner as in Example 1 except that heat curing was performed in Pattern 2.
In Example 2 in which the α value of the characteristic value of the adiabatic temperature rise was corrected based on the present invention, the integrated temperature up to 3 hours of age was calculated to be 123.1 ° C. at a distance of 100 mm from the heating surface. The measured value was 121.9 ° C., the error of the integrated temperature was 1.0%, and the error was within 5%, and the measured value was accurately reproduced. Furthermore, when the formula (6) in which the α value of the characteristic value of the adiabatic temperature rise and the specific heat are corrected based on the present invention is applied, the obtained value is 122.7 ° C., and the measurement error is 0.7. % And the error of the integrated temperature was within 1%, and the measured value was accurately reproduced.
In the present invention, the integrated temperature can be estimated with high accuracy regardless of the pattern of heat curing, and the result is in good agreement with the actually measured value.

Next, a compression strength prediction formula for determining the compression strength of the concrete molded body at the time of demolding is constructed from the integrated temperature estimated in the step (C), using the integrated temperature obtained from the detected temperature history.
In this method, as described in detail in the step (C), it is assumed that the time when the temperature of the concrete composition has increased to 40 ° C. is the curing start time, and 40 ° C. is the reference integrated temperature (40 ° C. of the temperature history). (The area of the part exceeding) was examined as an age evaluation scale.
Then, based on the experimental data, the compression strength prediction formula of the initial age was obtained from the evaluation scale of each age and the water binder ratio by the least square method. The compressive strength was estimated from the temperature history and the water binder ratio of the same-curing specimen and member-temperature-following curing specimen in the actual machine manufacturing experiment.
6A and 6B, the following regression equations Y = a · ln (X) + b and Y = a · shown in FIG. 5A to FIG. each coefficient of X ^b a, according to the relation b and a binder water ratio, since any coefficient has been determined to be close to a linear relationship with binder water ratio, based on these results, the water binding agent ratio Coefficients were determined by the method of least squares, with the relationship between various age rating scales and compressive strength being in the form of the following formula (11) depending on the 40 ° C. reference integrated temperature. The determined coefficients were α: 1.670, β: -2.339, γ: 0.030, and δ: 0.547.

Formula (11)

The integrated temperature based on 40 ° C. received at a position of 100 mm from the concrete surface is 27 ° C. · h, and the initial compressive strength when the water binding material ratio of the concrete molded body estimated from this compressive strength prediction formula is 40% is respectively It was 14.3 N / mm < ² > [process (C)].
When the obtained compressive strength is compared with the compressive strength determined in the step (A): 10 N / mm ² , the compressive strength [set in the step (A)] <compressive strength [estimated in the step (C)], Using the mixing conditions of the concrete composition determined in Example 1, it was confirmed that the initial strength capable of demolding was achieved by heating and curing under the heating and curing conditions (Pattern 2) [Step (D)]. .
Moreover, it has already been confirmed in the step (B) that, under the blending conditions of the concrete composition, the water binder ratio is 38.0% and sufficient long-term compressive strength can be expressed.

  Thus, according to the production method of the present invention, in the concrete molded body produced by heat curing, the initial compressive strength and long-term strength of the concrete molded body required at the time of demolding regardless of the shape of the formwork. Can be accurately predicted, and an efficient method for producing a concrete molded body under optimum production conditions can be provided.

Claims (5)

A method for producing a concrete molded body in which a concrete composition is molded in a mold,
In consideration of the shape of the concrete molded body to be produced, the step of determining the compressive strength required at the time of demolding (A),
From the long-term compressive strength required for the concrete molded body, a step (B) of setting a range of the water binder ratio of the concrete composition,
A plurality of concrete compositions having different water binder ratios selected within the range of the water binder ratio set in the step (B) are put into a mold having an assumed size, Heat curing under heat curing conditions, (a) integrated temperature obtained from the time history of the internal temperature of each concrete composition measured, or effective age, or (b) at least one of heat curing conditions or measured curing temperature The integrated temperature or effective age obtained from the time history of the internal temperature of the concrete composition obtained by unsteady heat conduction analysis using the above, (a) obtained by actual measurement, or (b) unsteady heat conduction Based on the temperature history obtained from the analysis, concrete specimens made of each concrete composition were produced, the compressive strength of the produced concrete specimen was obtained, and the integrated temperature Is the heat curing temperature and the heat curing time, which are the heat curing conditions that are actually implemented during the production of concrete moldings, using the compressive strength prediction formula constructed from the relationship between the effective age and the water binder ratio of the concrete composition. (C) calculating the compressive strength of the concrete compact by substituting the integrated temperature or effective age obtained in step 1 into the compressive strength prediction formula
And the process (D which determines at least one of the water binder ratio of a concrete composition, and heat curing conditions so that the compressive strength calculated at the process (C) may become more than the compressive strength set at the process (A) (D) ),
A method for producing a concrete compact including   In the unsteady heat conduction analysis in the step (C), the coefficient of the adiabatic temperature rise rate of the concrete composition corrected according to the amount of heat transferred to the concrete composition by the heat curing condition is used to calculate the concrete composition in the mold. A process for estimating the temperature distribution and determining the heat curing conditions, a specific heat coefficient corrected according to the coefficient of heat insulation temperature rise rate of the concrete composition corrected according to the amount of heat transferred to the concrete composition by the heat curing condition and the distance from the surface Estimating the temperature distribution of the concrete composition in the mold using the step, determining the heat curing conditions, and the adiabatic temperature rise rate of the concrete composition corrected according to the amount of heat transferred to the concrete composition by the heat curing conditions The temperature distribution and strength distribution of the concrete composition in the formwork. Suitable mold time removal of the concrete moldings, the production method of the concrete molded body according to claim 1 comprising at least one of determining the lifting time. Compare the compression strength set in step (A) with the result of compression strength calculated by the compression strength prediction formula used in step (C),
The total cost of the material cost determined from the water binder ratio of the concrete composition to obtain the required compressive strength when demolding the concrete compact and the energy cost to output the integrated temperature is minimized. The method for producing a concrete molded body according to claim 1 or 2, further comprising a step (E) of determining a water binder ratio of the concrete composition and heat curing conditions. A method for manufacturing management of a concrete molded body in which a concrete composition is molded in a mold,
In consideration of the shape of the concrete molded body to be manufactured, the step of determining the compressive strength required at the time of demolding (A2),
A step (B2) of setting the range of the water binder ratio of the concrete composition from the long-term compressive strength necessary for the concrete molded body,
Concrete compositions having different water binder ratios selected within the range of the water binder ratio set in the step (B2) are put into molds having respective assumed dimensions, and a plurality of heat curings are performed. Heat curing under conditions, (a) the accumulated temperature obtained from the time history of the internal temperature of each concrete composition measured, or the effective age, or (b) at least one of the heat curing conditions or the measured curing temperature The accumulated temperature or effective age obtained from the time history of the internal temperature of the concrete composition obtained by unsteady heat conduction analysis and (a) obtained by actual measurement, or (b) by unsteady heat conduction analysis Based on the obtained temperature history, concrete specimens made of the respective concrete compositions were produced, and the compressive strength of the produced concrete specimens was obtained. Using the compressive strength prediction formula built from the relationship between the age of the effect material and the water binder ratio of the concrete composition, the heat curing temperature and the heat curing time, which are the heat curing conditions that are actually implemented at the time of manufacturing the concrete molded body, The obtained integrated temperature or effective age is substituted into the compressive strength prediction formula to calculate the compressive strength of the concrete compact (C2),
The compression strength set in step (A2) is compared with the compression strength result calculated in step (C2), and the compression strength result calculated in step (C2) is compared with the compression strength set in step (A2). A step (D2) of confirming that the concrete molded body can be demolded by being the same or larger.
Manufacturing control method for concrete compacts including   In the step (C2), the temperature history of the concrete composition in the mold is driven into the mold using the concrete composition, heat curing is performed, and the temperature of the concrete composition inside the mold is measured. The manufacturing control method of the concrete molded object of Claim 4 calculated | required by this.