JP6914039B2 - Strength estimation method for mixed cement, strength estimation device and concrete manufacturing method - Google Patents

Description

The present invention relates to a method for estimating the strength of mixed cement, an apparatus for estimating strength, and a method for producing concrete.

Generally, in the case of concrete using mixed cement, the strength characteristics differ depending on the replacement rate of the mixed material. Especially when looking overseas, this mixture is often mixed with Portland cement. Figure 7 shows the current status of the use of mixed cement in Europe. From this figure, it can be seen that the mixed cement of CEM II to CEM V is often used. Table 1 shows EN197-1, which is a European cement standard. This standard has a very wide range of replacement amounts of mixed materials for Portland cement. Next, the data of the amount of the mixed material mixed with the cement of each country in the world is shown in FIG. 8 (Source: Non-Patent Document 1). It can be confirmed that the amount of mixed materials used except Gypsum is increasing year by year, and it is expected that the opportunities for use will increase in the future.

-Type of cement (mass%) in EN197-1: 2011

For the above reasons, in some countries, most of the cement on the market is mixed cement, and mixed cement is often used when performing construction work overseas. As reference examples, Table 2, FIGS. 9 to 11 show examples of material composition and physical property values of cement actually sold overseas. R is ordinary Portland cement containing no mixture. It can be confirmed that the mineral composition and material composition in the cement are different, and that the fluidity, coagulation characteristics, and strength characteristics of the concrete developed are different from each other. Since such mixed cement has little experience in use in Japan, there is a problem that the conventional empirical formula does not apply and it is difficult to estimate the performance as concrete.

・ Mineral composition of cement produced overseas

In practice, when using a binder or admixture different from the usual one for concrete, the performance is confirmed in advance by test kneading. However, while there are various combinations of materials including aggregates, the preparation period for construction is limited, so the minimum confirmation is often performed, and when the lot of materials or the temperature changes, test kneading is performed. There is also a problem that the performance of concrete is different from that of.

Japanese Unexamined Patent Publication No. 2015-135257 Japanese Unexamined Patent Publication No. 2014-167467

GNR Project Reporting CO2, [online], [Search December 12, 2016], Internet <URL: http://www.wbcsdcement.org/GNR-2012/geo/GNR-Indicator#3219-geo.html> Yuya Yoda, Yutaka Aikawa, Shindaikei, Etsuro Sakai: Relationship between calorific value of hydration and compressive strength of mixed cement, Cement / Concrete Papers, Vol. 69, pp.191-198 (2015) T.C.Powers: Structure and physical properties of hardened Portland cement, Journal of the American Ceramic Society, Vol.41, No.1, pp.1-6 (1958) Kiyoshi Hagiwara, Kazue Asaga: Various calorimeters used for cement and concrete, Journal of the Society of Inorganic Materials, Japan 14, 451-458 (2007)

In order to solve the above-mentioned problems, it has been desired to develop a technique that enables as many studies as possible with simple measurement when confirming the performance of the mixed cement. On the other hand, the present inventor has conducted intensive research on the hydration reaction of the binder with the aim of constructing a technique capable of easily evaluating the performance such as the strength characteristics of the mixed cement at many points in time. As a result, the following invention focusing on the use of the calorimeter has been reached.

The present invention has been made in view of the above, and is a method for estimating the strength of a mixed cement, a strength estimation device, and a device for estimating the strength of a mixed cement, which can easily and at many times evaluate the strength characteristics of a hydrated solidified product using the mixed cement. It is an object of the present invention to provide a method for producing concrete.

In order to solve the above-mentioned problems and achieve the object, the method for estimating the strength of the mixed cement according to the present invention is a method for estimating the strength of a hydrated solidified product using a mixed cement composed of a cement and a mixed material. Then, the mixed cement and water are kneaded at a predetermined water powder ratio to prepare a sample, and the step of measuring the cumulative calorific value of this sample at a predetermined age, the measured cumulative calorific value, and the final calorific value It is characterized by comprising a step of estimating the strength based on the volume ratio of the cement and the mixed material in the mixed cement and the material constant set according to the type of the mixed material.

Further, the device for estimating the strength of the mixed cement according to the present invention is an device for estimating the strength of a hydrated solidified product using a mixed cement composed of a cement and a mixed material, and the mixed cement and water are mixed with predetermined water powder. A measuring means for measuring the cumulative calorific value at a predetermined age of a sample mixed by body ratio, the measured cumulative calorific value, the final calorific value, the volume ratio of cement and the mixed material in the mixed cement, and the mixed material. It is characterized by providing an estimation means for estimating the strength based on the material constant set according to the type of.

Further, in the method for producing concrete according to the present invention, a mixed cement corresponding to a predetermined strength is selected based on the estimation by the above-mentioned method for estimating the strength of the mixed cement, and concrete is produced using the selected mixed cement. It is characterized by.

According to the method for estimating the strength of mixed cement according to the present invention, it is a method for estimating the strength of a hydrated solidified product using mixed cement composed of cement and a mixed material, in which the mixed cement and water are mixed with predetermined water powder. A step of kneading at a body ratio to prepare a sample and measuring the cumulative calorific value at a predetermined age of this sample, the measured cumulative calorific value, the final calorific value, and the volume ratio of cement and mixed material in the mixed cement. And, since the step of estimating the strength based on the material constant set according to the type of the mixed material is provided, the strength characteristics of the hydrated solidified product using the mixed cement should be evaluated easily and at many times. It has the effect of being able to.

Further, according to the mixed cement strength estimation device according to the present invention, it is an device for estimating the strength of a hydrated solidified product using a mixed cement composed of a cement and a mixed material, and the mixed cement and water are predetermined. A measuring means for measuring the cumulative calorific value of a sample mixed with a water powder ratio at a predetermined age, the measured cumulative calorific value, the final calorific value, and the volume ratio of cement and mixed material in the mixed cement. Since it is provided with an estimation means for estimating the strength based on the material constant set according to the type of the mixed material, it is possible to easily and at many times evaluate the strength characteristics of the hydrated solidified product using the mixed cement. It has the effect of being able to do it.

Further, according to the method for producing concrete according to the present invention, a mixed cement corresponding to a predetermined strength is selected based on the estimation by the above-mentioned method for estimating the strength of the mixed cement, and concrete is produced using the selected mixed cement. Therefore, by using an appropriate mixed cement from the mixed cements whose strength is estimated, for example, concrete having excellent strength development can be produced.

FIG. 1 is a flow chart showing an embodiment of a strength estimation method and a strength estimation device for a mixed cement according to the present invention. FIG. 2 is an explanatory view of the conduction calorimeter used in the confirmation experiment, (1) is a top view of the conduction calorimeter, (2) is a side sectional view, and (3) is a conceptual diagram of the measurement mechanism. FIG. 3 is a diagram showing the relationship between the existing strength evaluation formula and the compressive strength. FIG. 4 is a diagram showing the compressive strength obtained by the strength evaluation formula of the present embodiment. FIG. 5 is a diagram showing the relationship between the estimated value of the compressive strength and the actually measured value. FIG. 6 is a diagram showing a conventional flow. FIG. 7 is a diagram showing the production amount of each cement type in Europe. FIG. 8 is a diagram showing the ratio of the mixed material to the mixed cement. FIG. 9 is a diagram showing a mortar flow of cement produced overseas. FIG. 10 is a diagram showing the coagulation characteristics of cement produced overseas. FIG. 11 is a diagram showing the strength characteristics of cement produced overseas.

Hereinafter, embodiments of a mixed cement strength estimation method, a strength estimation device, and a concrete manufacturing method according to the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment.

As described above, the present invention focuses on the use of a calorimeter so that the strength characteristics of the mixed cement can be easily evaluated at many time points (material age). In particular, the measurement of heat of reaction with a conduction calorimeter has good reproducibility, multi-point measurement and curing temperature control are possible, and there is little difference between measurers, so the temperature is different from Japan, and there is a shortage of engineers. Overseas, which tends to be very effective, it can be an extremely effective means.

(Method of estimating strength of mixed cement)
First, an embodiment of the method for estimating the strength of the mixed cement according to the present invention will be described. The present invention is carried out in the flow as shown in FIG.

First, in step S1, about 5 to 20 g of mixed cement composed of cement and a mixed material is accurately measured, and the mixed cement and water are kneaded at a predetermined water powder ratio to prepare a cement paste (sample). .. Here, when, for example, about 15 g of mixed cement is used for one test piece, about 30 g of cement is sufficient for testing with two test pieces in order to reduce variations in the components of the mixed cement.

Next, in step S2, the prepared cement paste is set in a conduction calorimeter set to a predetermined curing temperature (constant temperature). The characteristics of the conduction calorimeter will be described later.

Subsequently, in step S3, the heat of reaction (cumulative calorific value) up to a predetermined material age (for example, material age X days) of the cement paste is measured with a conduction calorimeter.

Next, in step S4, the compressive strength at a predetermined material age (for example, material age X days) is obtained by substituting the information on the preparation of the mixed cement and the measured reaction heat into the strength evaluation formula [9] described later. .. This compressive strength can be determined many times in a non-destructive manner at any material age (for example, 1 day, 3 days, 7 days, 28 days, etc.) using the strength evaluation formula [9]. The information regarding the preparation of the mixed cement refers to the initial volume ratio of the cement and the mixed material in the mixed cement, the final calorific value, and the material constants preset according to the type of the mixed material. The initial volume ratio of the cement and the mixed material can be determined from the replacement rate or the mixed ratio of the mixed material and the physical property values of the cement and the mixed material.

As described above, according to the present embodiment, the strength characteristics of the cement paste at a predetermined age using the mixed cement can be easily evaluated at many times. This makes it easy to estimate the strength characteristics of concrete using this mixed cement.

Further, according to the present embodiment, it is possible to estimate the strength characteristics of many consecutive ages with a mixed cement of several g. It is not necessary to prepare a huge number of test specimens as in the conventional method, and a small amount of mixed cement is required. Further, as will be described later, by setting a constant correction coefficient depending on the type of mixed material, evaluation can be performed on the same evaluation axis as the reference cement. Further, it can be evaluated by setting a constant correction coefficient according to the curing temperature. Furthermore, it is possible to handle a wide range of mixed cements around the world with the parameters of Portland cement type, mixed material type, powderiness, chemical composition, and mixed material amount.

(About strength evaluation formula)
With ordinary Portland cement, the strength can be estimated if the amount of hydrate produced and the amount of voids are known. The integrated calorific value obtained by the conduction calorimeter can be converted into the reaction rate by the final calorific value in Table 3 and the formulas [1] and [2].

α _C = H _C / H _C ∞ Equation [1]
α _B = H _B / H _B ∞ Equation [2]
Here, α _C : Reaction rate of Portland cement
H _C : Cumulative calorific value of Portland cement
H _C ∞: Ultimate calorific value of Portland cement
α _B : Reaction rate of mixed material
H _B : Cumulative calorific value of the mixed material
H _B ∞: Ultimate calorific value of the mixture

・ Ultimate calorific value for each cement type and material (H∞) (J / g)

On the other hand, when a mixed material is added, the filling rate of voids per unit reaction rate is different. Therefore, the hydrate formation volume ratio per unit reaction rate of ordinary Portland cement is generally about 2.0 (here, it is set to 2.2), but the mixed cement system is the mixture of the mixed materials in Table 4. By multiplying the material constant (γ) determined by the type, the amount of hydrate produced (V _hyd-C , V _hyd-B ) can be obtained. One of the features of the present invention is that γ is set for each mixed material. Here, V _C0 and V _B0 are the volume ratios of the initial cement and the mixed material obtained from the formulation, and the influence of the water-cement ratio is taken into consideration.

V _hyd-C = 2.2 × α _C × V _C0 formula [3]
V _hyd-B = 2.2 × γ × α _B × V _B0 formula [4]

-Value of material constant γ (Source: Non-Patent Document 2)

Residual cement content (V _C, V _B) is determined from the volume of the initial cement and admixture with unreacted rate.

V _C = (1-α _C ) × V _C0 formula [5]
V _B = (1-α _B ) × V _B0 formula [6]

Using the above formula, the capillary porosity is calculated by the following formula [7].

V _pore = 1-V _C −V _B −V _hyd-C −V _hyd-B equation [7]

By using the above formulas [3] [4] [7], the strength can be obtained by the following strength evaluation formula [9] (Source: Non-Patent Document 3).

X = (V _hyd-C + V _hyd-B ) / (V _hyd-C + V _hyd-B + V _pore ) Equation [8]
σ ＝ σ ₀ X ^N equation [9]
Here, X: gel / space ratio (vol./vol.)
σ: Strength (N / mm ² )
σ ₀ : Ultimate strength (N / mm ² )
N: Constant

(Confirmation experiment)
Next, a confirmation experiment conducted to confirm the action and effect of the present invention will be described.

-Materials used The materials used are a mixture of four types of Portland cement (C: normal, H: early strength, M: moderate heat, L: low heat) and limestone fine powder (LSP) shown in Tables 5 to 7. Blast furnace slag fine powder (BFS) with different powderiness, type and replacement rate, fly ash (FA) with different type and mixing ratio, curing temperatures of 10 and 30 ° C for each, Various mixed cements, such as those with different water-cement ratios, were sampled and prepared.

Regarding the blast furnace slag fine powder, those with symbols 3000, 4000, and 6000 use Japanese JIS standards, and those with other symbols have different chemical compositions from overseas. For fly ash, three types from different countries and production areas were used.

・ Portland cement-based study level

・ Examination level of the system mixed with blast furnace slag

・ Examination level of the system mixed with fly ash

-Compressive strength test The strength test piece was made into a paste, and each cement was kneaded with a Hobart mixer at a water-cement ratio of 0.5 for 3 minutes and placed in a cylindrical frame of φ50 × 100 mm to be in a sealed state. The kneading and curing of the test piece were carried out in a constant temperature room at 20 ° C. At a predetermined age (1, 3, 7, 14, 28 days), the mold was removed immediately before the compressive strength test, and the upper and lower surfaces of the test piece were polished and then subjected to the compressive strength test. The compressive strength was the average value of the three test pieces.

-Measurement of cumulative calorific value with a conduction calorimeter Weigh 15 g of each cement, knead it by hand at a predetermined water-cement ratio for 3 minutes, and then use the conduction calorimeter CHC-OM6R (Tokyo Co., Ltd.) as shown in Fig. 2. It was set in (manufactured by Riko), and the calorific value of hydration was measured continuously until the age of 28 days. For the analysis of the data, due to the characteristics of the outer kneading device, the data of the calorific value of hydration from 1 hour of age was used.

FIG. 2 illustrates the device configuration of the conduction calorimeter used in this experiment. As shown in FIGS. 2 (1) to 2 (3), the conduction calorimeter is symmetrical to two calorimeters 2 manufactured under the same physical, mechanical and electrical conditions on one constant temperature body 1 (heat sink). The output of the heat good conductor 3 (or thermo module), which also serves as a heat sensitive body, is differentially connected. This conduction calorimeter has one comparison side R and six sample sides S. A comparison side container 4 is arranged on the comparison side R, and a dedicated container 5 which is a sample side container is arranged on the sample side S.

FIG. 2 (3) shows the measurement principle of the twin type conduction calorimeter as an example of the measurement principle of the conduction calorimeter. As shown in this figure, when one of the two calorimeters 2 is the sample side S and the other one is the comparison side R, if a thermal change occurs in the sample side S, the comparison side R is used as a reference. A signal proportional to the thermal change is generated. In this conduction calorimeter, this output signal is measured in time and compared with a known calorimeter to obtain the calorific value.

The advantages of such a twin-type conduction calorimeter are very large, such as baseline drift due to changes in room temperature on the calorimeter, frictional heat when the inside of the sample side container (dedicated container 5) is agitated, and sample side container (dedicated container). All unnecessary heat such as latent heat of evaporation of the liquid generated in 5) is canceled, and it is an excellent calorimeter capable of measuring only the target calorimeter (Source: Non-Patent Document 4).

-Results First, BFS (blast furnace slag fine powder) is mixed with the relationship between the cumulative calorific value (gel / space ratio) and compressive strength evaluated by the strength evaluation formula when the material constant γ is not used, which is the conventional evaluation method. The system is shown in a list in FIG. 3 as an example.

Here, "C" in FIGS. 3 (a) to 3 (c) is a character string separated by hyphens such as ordinary Portland cement (LSP mixing ratio of zero) and "BFS-20", and the first character is BFS. Type 4000, the second number indicates the replacement rate. In both cases, the water-cement ratio is 50%. In addition, in the character string separated by hyphens such as "BFS6000-50-50%" in Fig. (D), the first character is the BFS type, the second number is the replacement rate, and the third number is water cement. Shows the ratio. In both cases, the curing temperature is 20 ° C. Further, in a character string separated by a hyphen such as "BFS-L-20" in FIG. (E), the second character indicates the BFS type, and the third number indicates the replacement rate. In both cases, the water-cement ratio is 50%. In addition, in the character string separated by hyphens such as "BFS4000-50-60%" in the figure (f), the first character is the BFS type, the second number is the replacement rate, and the third number is water cement. Shows the ratio. In both cases, the curing temperature is 20 ° C.

As shown in FIG. 3, in the conventional evaluation method, it can be seen that the larger the mixing ratio of BFS (mixing material), the greater the difference between the strength evaluation formula and the compressive strength.

Next, the relationship between the cumulative calorific value (gel / space ratio) and the compressive strength evaluated by the strength evaluation formula [9] using the material constant γ for all levels is shown in FIG. 4, and the estimated value and the measured value of the compressive strength. The relationship between the above is shown in FIG. As shown in these figures, by using the strength evaluation formula [9], it is possible to evaluate the strength characteristics of the mixed cement in a considerably wide range by the simple method of the present invention by calorific value measurement. Understand.

By the way, conventionally, in order to confirm the strength of a hydrated solidified product using cement in accordance with JIS standards, as shown in FIG. 6, a plurality of columnar mortar test specimens are prepared and cured at a constant temperature. , It was necessary to perform a compression test (compressive strength test) at each predetermined age. The mortar test piece destroyed in each test was discarded, and the amount of cement used in the standard test was required to be, for example, about 3 kg. In addition, it was impossible to test more than the number of prepared mortar test specimens, which required a large amount of cement, labor and cost.

However, according to the present embodiment, the amount of cement used is smaller than that in the conventional case as shown in the flow of FIG. The compressive strength can also be determined by the degree. In spite of such a very simple process, this embodiment has a fairly wide range in the world, with parameters of Portland cement type, mixed material type, powderiness, chemical composition, and mixed material amount. The compressive strength of the hydrated solidified product using mixed cement can be estimated.

(Mixed cement strength estimation device)
Next, an embodiment of the mixed cement strength estimation device according to the present invention will be described.

The device for estimating the strength of mixed cement according to the present invention is an device for estimating the strength of a hydrated solidified product using mixed cement composed of cement and a mixed material, and includes measuring means and estimating means. Here, since the measuring means and the estimating means correspond to each step of the strength estimation method of the mixed cement according to the present invention, the following description overlaps with the contents described in the above-mentioned strength estimation method of the mixed cement. The description of the contents will be omitted.

The measuring means measures the cumulative calorific value at a predetermined age of a sample obtained by mixing mixed cement and water at a predetermined water powder ratio. This measuring means can be configured by a conduction calorimeter.

The estimation means estimates the strength based on the measured cumulative calorific value, the final calorific value, the volume ratio of cement and the mixed material in the mixed cement, and the material constant set according to the type of the mixed material. be. Examples of this estimation means include a database or memory storing information representing the above-mentioned cumulative calorific value, ultimate calorific value, volume ratio of cement and mixed material in mixed cement, and material constants set according to the type of mixed material. , The information stored in this database or memory can be read out, and the computer can be configured by a computer having an arithmetic processing unit for estimating the strength of the mixed cement at a predetermined age by the strength evaluation formula [9].

According to the strength estimation device of the mixed cement configured in this way, the strength characteristics of the hydrated solidified material such as concrete using the mixed cement can be easily and at many times evaluated in the same manner as the above-mentioned strength estimation method. can.

(Concrete manufacturing method)
Next, an embodiment of the concrete manufacturing method according to the present invention will be described.

The method for producing concrete according to the present invention is to select a mixed cement corresponding to a predetermined strength based on the estimation by the above-mentioned method for estimating the strength of the mixed cement, and to produce concrete using the selected mixed cement. .. In this way, for example, concrete having excellent strength development can be produced by using an appropriate mixed cement from the mixed cement whose strength is estimated when it is made into a hydrated solidified body.

As described above, the method for estimating the strength of mixed cement according to the present invention is a method for estimating the strength of a hydrated solidified product using a mixed cement composed of cement and a mixed material, wherein the mixed cement and water are used. To prepare a sample by kneading with a predetermined water powder ratio, and to measure the cumulative calorific value of this sample at a predetermined age, the measured cumulative calorific value, the final calorific value, and the cement in the mixed cement. Since the step of estimating the strength based on the volume ratio of the mixed material and the material constant set according to the type of the mixed material is provided, the strength characteristics of the hydrated solidified product using the mixed cement can be easily and easily increased. It can be evaluated at the time of.

Further, according to the mixed cement strength estimation device according to the present invention, it is an device for estimating the strength of a hydrated solidified product using a mixed cement composed of a cement and a mixed material, and the mixed cement and water are predetermined. A measuring means for measuring the cumulative calorific value at a predetermined age of a sample mixed with a water powder ratio, the measured cumulative calorific value, the final calorific value, and the volume ratio of cement and mixed material in the mixed cement. Since it is provided with an estimation means for estimating the strength based on the material constant set according to the type of the mixed material, it is possible to easily and at many times evaluate the strength characteristics of the hydrated solidified product using the mixed cement. can.

Further, according to the method for producing concrete according to the present invention, a mixed cement corresponding to a predetermined strength is selected based on the estimation by the above-mentioned method for estimating the strength of the mixed cement, and concrete is produced using the selected mixed cement. Therefore, by using an appropriate mixed cement from the mixed cements whose strength has been estimated, for example, concrete having excellent strength development can be produced.

As described above, the method for estimating the strength of mixed cement, the strength estimation device, and the method for producing concrete according to the present invention are useful for estimating the strength of a hydrated solidified product using mixed cement composed of cement and a mixed material. In particular, it is suitable for easily and at many times evaluating the strength characteristics of concrete using mixed cement.

1 Constant temperature body (heat sink)
2 Calorimeter 3 Thermal conductor (or thermo module)
4 Comparison side container 5 Dedicated container S Sample side R Comparison side

Claims (3)

It is a method of estimating the strength of a hydrated solidified product using a mixed cement composed of a cement and a mixed material.
A step of kneading mixed cement and water at a predetermined water powder ratio to prepare a sample, and measuring the cumulative calorific value of this sample at a predetermined age.
Hydrate of cement and mixed material based on the measured ratio of cumulative calorific value and final calorific value, the volume ratio of cement and mixed material in mixed cement, and the material constant set according to the type of mixed material. determine the product quantity and capillary porosity, obtained on the basis of the amount and capillary porosity of hydrates, intensity estimating method of mixing cement, characterized in that it comprises a step of estimating the strength. A device for estimating the strength of a hydrated solidified product using mixed cement consisting of cement and a mixed material.
A measuring means for measuring the cumulative calorific value at a predetermined age of a sample obtained by mixing mixed cement and water at a predetermined water powder ratio, and
Based on the measured cumulative calorific value-final calorific value ratio, the volume ratio of cement and mixed material in the mixed cement, and the material constant set according to the type of mixed material, the hydrate of cement and mixed material determine the product quantity and capillary porosity, obtained on the basis of the amount and capillary porosity of hydrates, intensity estimating device of the mixed cement, characterized in that it comprises an estimation means for estimating the strength. A method for producing concrete, which comprises selecting a mixed cement corresponding to a predetermined strength based on an estimation by the method for estimating the strength of the mixed cement according to claim 1, and producing concrete using the selected mixed cement. ..

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