JP2001289840A - Method for evaluating fresh concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem of disabling of simple and accurate evaluations of a unit cement amount and a unit fine aggregate amount of a fresh concrete. SOLUTION: A method for evaluating the fresh concrete comprises the steps of converging an air amount contained in a mortar in which a rough aggregate is removed from the fresh concrete, then measuring a unit volume mass and a unit water amount of the mortar, and obtaining a unit cement amount and a unit fine aggregate based on the unit volume mass and the unit water amount of the measured mortar, thereby simply and accurately obtaining the unit cement amount and the unit fine aggregate of the fresh concrete.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of evaluating fresh concrete for evaluating unit cement and fine aggregate of unconsolidated concrete (hereinafter referred to as fresh concrete).

[0002]

2. Description of the Related Art For example, unit cement amount and unit fine aggregate amount of fresh concrete in a concrete batcher plant or a concrete casting site are important indicators for quality control of concrete. If the evaluation of the unit cement amount and the unit fine aggregate amount is not appropriate, the strength of the cast concrete will be insufficient, which may cause concrete collapse accidents. A method for evaluating the unit cement amount by using characteristics such as viscosity has been proposed.

[0003]

However, the method of evaluating the amount of unit cement using characteristics such as viscosity is complicated and is not suitable for implementation on site. In addition, accurate evaluation cannot be performed stably because of high temperature dependency. Also, there is no practical evaluation method for the unit fine aggregate amount of fresh concrete. In order to solve the problems in the conventional technology, the present invention has improved a method for evaluating fresh concrete, and converges the amount of air contained in mortar obtained by removing coarse aggregate from fresh concrete. By measuring the unit volume mass and the unit water amount of the mortar, based on the measured unit volume mass and the unit water amount of the mortar, a unit cement amount and a unit fine aggregate are obtained,
It is an object of the present invention to provide a method for evaluating fresh concrete, which can obtain a unit cement amount and a unit fine aggregate amount of fresh concrete simply and accurately.

[0004]

In order to achieve the above-mentioned object, the present invention converges the amount of air contained in mortar obtained by removing coarse aggregate from fresh concrete,
A unit volume mass and a unit water amount of the mortar are measured, and based on the measured unit volume mass and the unit water amount, one or both of a unit cement amount and a unit fine aggregate amount of fresh concrete are measured. It is configured as a method for evaluating fresh concrete. In the fresh concrete evaluation method according to the present invention, the unit cement amount and the unit fine aggregate amount of the fresh concrete are obtained based on the measured unit volume mass and unit water amount of the mortar. These relationships can be obtained in advance, and it is easy to obtain a unit cement amount and a unit fine aggregate amount of fresh concrete. However, the above relationship is affected by the fluctuation of the air amount and the bias of the coarse aggregate. Therefore, by removing the coarse aggregate in advance and converging the amount of air contained in the mortar from which the coarse aggregate has been removed from the fresh concrete, the influence is eliminated, so that accurate measurement can be performed stably. Becomes For measurement of the unit volume mass of the mortar, for example, a transmission type gamma ray density meter, or a balance and a container can be used. For measuring the unit water amount of the mortar, for example, a neutron moisture meter or a microwave moisture meter can be used. When a transmission type gamma ray density meter, neutron moisture meter, or microwave moisture meter is used, it is possible to easily measure a large number of samples. In addition, when these transmission-type measuring instruments are used, the need to transfer the mortar to another container is reduced, and the sampling error can be suppressed accordingly.

[0005]

Embodiments of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention.
The following embodiments are specific examples of the present invention and do not limit the technical scope of the present invention. FIG. 1 shows a schematic configuration of an apparatus used to execute a method for evaluating fresh concrete according to an embodiment of the present invention. In the present embodiment, mortar F obtained by removing coarse aggregate from fresh concrete is filled in a pressurizable pressure vessel 1 shown in FIG. This pressure vessel 1 includes a cylindrical vessel 11 and a lid 12. The mortar F is filled in the cylindrical container 11 of the pressure container 1. The lid 12 is provided with an air chamber 13. The mortar F in the cylindrical container 11 is pressurized by injecting air into the air chamber 13 by a pressurizing piston 14 for injecting air. The pressurizing pressure is operated using a pressure gauge 15 attached to the lid 12 as an index. The pressure vessel 1 has a mortar F
A measuring instrument 2 in which a transmission type gamma ray density meter and a neutron moisture meter used for measuring a unit volume mass and a unit water amount of the neutron moisture meter are attached. The measuring device 2 has a built-in arithmetic device, and the density measured by the transmission type gamma ray densitometer is converted into the unit volume mass of the mortar by the arithmetic device. What is obtained by a neutron moisture meter is the unit water volume. Based on the unit volume mass and unit water amount of the mortar measured by the measuring device 2,
The unit cement amount and unit fine aggregate amount of fresh concrete are determined. When the method for evaluating fresh concrete according to the present invention is carried out using the apparatus as described above, first, after removing coarse aggregate from fresh concrete, mortar F obtained by removing coarse aggregate from fresh concrete is subjected to JIS. The cylinder is filled in the cylindrical container 11 of the pressure vessel 1 while being pierced with a piercing rod according to a method such as that described above, so as to substantially fill the cylindrical container 11. Filled mortar F is, for example, the A-column-3 in the mixing list shown in FIG.
Coarse aggregate is removed from the fresh concrete.

Then, the lid 12 of the pressure vessel 1 is closed,
The inner space 16 of the cylindrical container 11 and the air chamber 13 are hermetically sealed in communication. When the lid 12 of the pressure vessel 1 is closed, air is injected into the air chamber 13 by moving the pressurizing piston 14 for injecting air, and an appropriate pressure of about 98 to 490 [Pa] is observed while watching the pressure gauge 15. By pressurizing with pressure, bubbles contained in the mortar F in the cylindrical container 11 are crushed. In this state, the measuring instrument 2 is operated, and the mortar F
Measure the density and the unit water volume. The density of the mortar F measured by the gamma ray densitometer of the measuring instrument 2 is converted into a unit volume mass of the mortar F by the arithmetic unit built in the measuring instrument 2 as described above. By using a transmission gamma ray density meter and a neutron moisture meter, it is possible to measure a large amount of samples, and if a stabilized scintillation detector method is used, very low drift measurements can be performed. It is. Furthermore, if a transmission-type measuring instrument is used, transfer of the mortar from the container is reduced, so that a sampling error can be suppressed. still,
When using a gamma ray density meter and a neutron moisture meter,
Radiation-specific statistical errors occur. Statistical errors can be suppressed by increasing the measurement integration time. For example, when a transmission type densitometer is used to measure a vessel with SGP100A piping, a statistical error of 2
is 0.005 [kg / l], the integration time is quadrupled to 960 seconds, and the statistical error 2σ is halved to 0.0025 [kg / l].
l]. The statistical error can be further reduced by increasing the source intensity. Such statistical errors are based on mathematical principles and do not originate from the present invention.

[0007] Between the unit volume mass and the unit water amount of the mortar F measured as described above and the unit cement amount and the unit fine aggregate amount of the mortar F to be obtained, for example, the air amount is 0%. In some cases, the following equations (1) and (2) are established. M = C + S + W (1) 1000 = (C / ρ _C ) + (S / ρ _s ) + (W / ρ _W ) (2) where M is the unit volume mass of mortar [kg / m ³ ],
C is mortar unit cement amount [kg / m ³ ], S is mortar unit fine aggregate amount [kg / m ³ ], W is mortar unit water amount [kg / m ³ ], ρ _C is cement density [kg] /
l], ρ _s is the fine aggregate density [kg / l], ρ _W is the water density [kg / l] (= 1.0) Using the above equations (1) and (2), the unit cement amount of mortar C is given by the following equation (3), and the unit fine aggregate amount S of the mortar is given by the following equation (4). _{C = (ρ C (M- ρ} s 1000) + W ρ C (ρ s -1)) / (ρ C - ρ s) (3) S = (ρ s (M- ρ C 1000) + W ρ s (ρ _C -1)) / (ρ _s -ρ _C ) (4) From the unit cement amount and the unit fine aggregate amount of the mortar represented by the above equations (3) and (4), The unit cement amount and the unit fine aggregate amount of fresh concrete can be obtained. To obtain the unit cement amount and the unit fine aggregate amount of fresh concrete from the unit cement amount and the unit fine aggregate amount of mortar, the mixed mortar volume or the mixed coarse aggregate volume or the mixed coarse aggregate amount and the coarse bone Using the density of the aggregate and the amount of air, or using the unit mass of fresh concrete and the amount of air measured before separation of coarse aggregate, the unit amount of coarse aggregate Can be calculated. From the obtained values, it is possible to calculate the estimated slump as well as the water-cement ratio. These calculations are performed by an arithmetic unit built in the measuring instrument 20 or by using a personal computer connected to the measuring instrument 20. When a plurality of types of cement and fine aggregate are used, the mixed cement density and the mixed fine aggregate density are used in the above formula (3) or (4). At this time, the unit mixed cement amount and the unit mixed fine aggregate amount are obtained.

As expressed by the above equations (3) and (4), the unit cement amount or the unit fine aggregate amount of the mortar is ρ _C , ρ
_{Since s} and ρ _W are given, they can be obtained if the unit volume mass and unit water amount of the mortar are determined. This relationship does not change even if the air amount is not 0% as long as it is stable. However, the smaller the air volume, the higher the accuracy. Shown in the formulation list in FIG. 2 are all the formulations of a typical Portland cement, a coarse aggregate size of 20 mm, and an air volume of 4.5% in the example plant. Here, the compounding system is a collective term for the same compounding group in which three of cement used / coarse aggregate size / air volume are the same. A compound group that differs in any one of cement used / coarse aggregate size / air amount is another compound system. Also,
Mixing columns A to H, which further classify one compounding system, are generic names of compounding groups having the same compounding strength and the same compounding system. Mixing groups having different mixing strengths form different mixing columns. FIG. 3 is a list of the mortar unit volume and water amount extracted from the mixture list of FIG. 2, and FIG. 4 is a graph plotting each combination of the mortar list. The straight line A1 shown in FIG.
It is determined by using the least squares method from the five compositions in the column, and is represented by the following equation (5). y = -1.2888x + 2572.5 (5) Further, the straight line A2 shown in FIG. 4 is determined by using the least square method from the five combinations in the H column, and is represented by the following equation (6). y = −1.3065x + 2600.7 (6) The inclinations of both straight lines A1 and A2 are almost the same. Generally, [density of coarse aggregate] and [mixed density of cement and sand] are close values. Even if the ratios of "coarse aggregate" and "cement + sand" change, water and solids have the same inclination and have a linear relationship because the density of solids in the composition is small as a whole. However, in this state, the solid content [coarse aggregate +
It is difficult to determine the unit cement amount in [sand + cement]. Therefore, in the present invention, only the mortar from which coarse aggregate has been removed is used to determine the unit cement amount by utilizing the density difference between fine aggregate and cement.

As shown in FIG. 4, a straight line A1 corresponding to the composition of row A represented by the above equation (5) is located at the lowest position and corresponds to the composition of row H represented by the above equation (6). The straight line A2 is located at the uppermost position. This means that the smaller the water-cement ratio, the higher it is located. In FIG. 4, points arranged vertically on a straight line mean that the composition is in accordance with the slump constant rule in the composition. A substantially parallelogram area corresponding to the water-cement ratio and the slump, which is constituted by the above-mentioned straight line and the vertically arranged points, appears in FIG. 4 with the unit volume mass and the unit water amount as axes. The unit cement amount and the unit fine aggregate amount can be determined depending on which position in the parallelogram area is plotted. Here, when the inclination of the straight lines A1 and A2 increases and the area expands vertically, the accuracy of the required unit cement amount and unit fine aggregate amount increases. The slopes of the straight lines A1 and A2 are related to the amount of air. For example, regarding the upper and lower area expansion, the density difference between the mortars of the blends A-1 and H-1 is A-1 (2.0565) when the air amount is 4.5%.
7), H-1 (2.07988), and the difference 0.023
A-1 (2.215
31), H-1 (2.224209) and the difference 0.02
678, and the difference in mass per unit volume becomes large, which facilitates measurement. Regarding the slope, the density difference between the mortars of the blends A-1 and A-5 is A-1 (2.0%) when the air amount is 4.5%.
5657) and A-5 (2.04728).
On the other hand, when the air amount is 0%, A-1 (2.
21153) and A-5 (2.11902), the difference is 0.02519, the difference in mass per unit volume is large, and measurement is easy. Fluctuations in the amount of air are determined by the straight line
Affect. Since the influence of the fluctuation of the air volume is quite large, in this evaluation method, the air volume is converged before the measurement of the unit volume mass. Further, by measuring the unit volume mass in a container in which the amount of air is suppressed, a sampling error is prevented from occurring. in this way,
In the method of evaluating fresh concrete according to the present embodiment, the unit cement amount and the unit fine aggregate amount of the fresh concrete are obtained based on the measured unit volume mass and unit water amount of the mortar. These relationships can be obtained in advance, and it is easy to obtain a unit cement amount and a unit fine aggregate amount of fresh concrete. However, the above relationship is affected by the fluctuation of the air amount and the bias of the coarse aggregate. Therefore, by removing the coarse aggregate in advance and converging the amount of air contained in the mortar from which the coarse aggregate has been removed from the fresh concrete, the influence is eliminated, so that accurate measurement can be performed stably. It is. In addition, since a transmission type gamma ray density meter, a neutron moisture meter, and a microwave moisture meter are used for measuring the unit volume mass and the unit water amount of the mortar, it is possible to easily measure a large number of samples. became. In addition, when these transmission-type measuring instruments are used, there is less need to transfer the mortar to another container, so that a sampling error can be suppressed accordingly. By converging the amount of air in advance, it is possible to measure the amount of air contained in concrete from the density before pressurization, the density after pressure release, and the density at the time of pressurization, and to apply vibration and the like together with pressurization. For example, it is possible to measure the state and influence of the void in the aggregate itself.

[0010]

In the above embodiment, if the fresh concrete has the property of crushing air bubbles by applying a pressure of about 98 [Pa], it is used for an air volume test without preparing a separate pressure vessel. It is also possible to use the container of the air chamber pressure method as it is, and attach the transmission type measuring device 2 to it or arrange it so as to sandwich it. In this way, the regular air amount test and the identification of the unit cement amount and the unit fine aggregate amount can be performed simultaneously. At this time, it is better to use an air volume tester that does not add water when pressurizing.
This is preferable since errors in handling after water addition hardly occur. Further, in the above-described embodiment, the pressure vessel 1 as shown in FIG. 1 is used, but a pressure vessel 41 as shown in FIG. 5 may be used instead. As shown in FIG. 5, the pressure vessel 51 is formed into a bag shape by attaching a blind lid 53 to one end of a cylindrical vessel 52 having flanges at both ends and attaching two disk-shaped towable membranes to the other end. A pressurized towable membrane 54 having an inlet and a lid 55 having a hole through which an oil inlet is inserted are attached. This pressure vessel 51
The transmission-type measuring device 2 is attached to the measuring device 2. The pressure vessel 5
When using No. 1, fresh mortar F obtained by removing coarse aggregates from fresh concrete of mix A-3, for example, is placed in the cylindrical container 52 in the same manner as in the above embodiment.
And fill it with a stick as needed. Next, after closing the lid 55 of the cylindrical container 52, oil is sent from the hydraulic pump 56 with a pressure gauge to the bag-like towable film 54 via a hose 57, and the bag-like towable film 54 is fed. The volume occupied by 54 is increased. Thereby, the fresh mortar F in the cylindrical container 52 is pressurized. The pressure at this time is also about 98 to 490 [Pa]. By this pressurization, bubbles in the fresh mortar F are crushed. In this state, the transmission type measuring device 2 is operated to measure the density (unit volume mass) and unit water amount of the fresh mortar F, as in the above embodiment. Based on the measured unit volume mass and unit water amount of the fresh mortar F, the unit cement amount and the unit fine aggregate amount of the fresh mortar F are obtained according to the above equations (3) and (4). The unit cement amount and the unit fine aggregate amount of concrete are obtained. The fresh mortar can be directly pressed by a plunger or the like. Direct pressurization using a plunger or the like is simple, but water may escape due to abrasion of the cylinder. As described above, it is preferable to pressurize the gas using the towable film to crush the bubbles, so that accurate measurement can be performed without leaking water.

Further, the unit volume mass can be obtained by using a scale 61 and a vibrating device 62 as shown in FIG. 6, for example, without using a transmission type gamma ray density meter. First, a cylindrical container 63 that transmits microwaves is placed on a scale 61 to measure the weight. Thereafter, mortar F obtained by removing coarse aggregate from fresh concrete is placed in the cylindrical container 63.
To about 2/3 of the volume of the container. Then,
As shown in FIG. 6A, the cylindrical container 63 and the mortar F
Is weighed with a scale 61, and then as shown in FIG.
The cylindrical container 63 into which the mortar F has been put is placed on the vibration device 62. When the cylindrical container 63 is vibrated by the vibration device 62 for several tens of seconds to several minutes,
The amount of air decreases and converges to a certain amount of, for example, about 1.8% regardless of the slump. The unit water amount is measured using the microwave moisture meter 64 as shown in FIG. 6C either before or after the excitation. When the amount of air converges, water is gently poured into the remaining portion of the cylindrical container 63 to fill the cylindrical container 63. The amount of water required to fill at this time is measured by a scale 61, and the volume of the filled water is subtracted from the volume of the cylindrical container 63, whereby the mortar F whose air amount has been reduced by vibration is reduced.
Of the mortar F after vibration and the mortar F
From the weight of the air and the value of the converged air amount, the planned air amount or the unit volume mass at the air amount 0 is calculated. From the unit volume mass and the unit water amount of the mortar thus obtained, the unit cement amount and the unit fine aggregate amount of the fresh concrete are obtained in the same manner as in the embodiment and the examples.
In this example, the vibrating device 62 is provided with the cylindrical container 63.
The vibration was applied to the mortar F by placing
For example, vibration is given by using ultrasonic waves,
Vibration may be applied to the mortar by applying vibration while rotating the mortar 3, or by inserting a vibrator inside the cylindrical container 63. When a vibrator is inserted inside, the amount of the sample adhering to the vibrator can be corrected by wiping it with a rag and weighing it with a weighing scale. When inserting the vibrating part inside the container, set the vibrating rod etc. in the container in advance or use a separate type vibrating rod etc. to supply energy by electromagnetic force etc. and vibrate. , Including a vibrating rod, etc., can be measured with a scale, thereby increasing the accuracy and shortening the time required for the entire measurement process.

In addition, in the above-described example, water was added and measured using a balance to determine the volume of the mortar F after the vibration.
The volume of fresh concrete may be obtained directly from the scale of the container, by using a graduated cylinder or the like. In this case, the use of a container with a smaller diameter at the top allows for more accurate water injection and a more accurate mortar volume after vibration than a cylindrical container with the same diameter in the vertical direction. It is preferable because it can be obtained. When the air amount is converged by vibrating as in the above example, the cement, aggregate, AE
It is conceivable that the proportional relationship may differ slightly from plant to plant due to the relationship between the agent and other additives. For example, an air amount of about 1.8% is determined for each plant or material used, and once determined based on this. After the calculation, the unit water amount may be measured. Further, when it is necessary to converge the amount of air to a smaller value, an antifoaming agent or a defoaming agent may be added to the mortar. It is also possible to use an air volume test device without separately preparing a pressure vessel. Weigh the weight of the mortar filled in a predetermined amount into the tube of the test equipment with a scale, measure the amount of air by a predetermined procedure such as JIS,
The unit volume mass at a predetermined air amount is calculated from the volume, weight, and air amount of the mortar, and the unit water amount is measured using a transmission neutron moisture meter separated from the container. The air volume is preferably measured by an air chamber pressure method. The reason is that the measurement can be performed in a short time, and the method can be combined with the method of the above-described embodiment by changing the pressing force in addition to the standard measurement by the same method. The method of weighing is not particularly limited, whether it is weighed including the lid of the air amount measuring device of the air amount test device or the container portion alone.

The unit for measuring the unit water amount may be one using neutrons, one using microwaves, or other means. It is desirable that neutrons can measure up to bound water, and that microwaves can be used because the measurement time is short. The means for measuring the unit mass is not limited to any of a method using a balance and a container, a method using a gamma ray densitometer, and a method for measuring other masses. The load cell is preferably of a load cell type because of its high performance and small size. Further, in the above-described embodiment, a measuring instrument in which a transmission type gamma ray density meter and a neutron moisture meter are integrated is used, but, of course, means for measuring a unit volume mass and means for measuring a unit water amount are separate. May be provided. The material of the container to be filled with mortar is not limited to any material such as iron, aluminum, vinyl chloride, PP, etc. When measuring the unit water volume using microwaves,
It is necessary to use a material that can transmit microwaves (eg, plastic or ceramic) at least partially. Further, the shape of the container is not limited to a cylinder or a square tube, but may be any shape. As the cylindrical container, a container having one end or both ends closed may be used, and a container whose diameter is enlarged or reduced may be used without any limitation. Further, it may be used as a curved tube or a curved tube. The arrangement of the gamma ray density meter, the neutron moisture meter, the microwave moisture meter and the container may be measured by directly attaching these transmission type measuring instruments to the container, or may be arranged separately from the container. Further, it does not matter which way the gamma ray or neutron beam or the microwave is passed in the height direction of the container, or whether the beam or the microwave is passed in the cross section direction of the container. Furthermore, the container of the air chamber pressure method used for the air volume test is used as it is,
A transmission type gamma ray density meter, neutron moisture meter, or microwave moisture meter may be attached to this. Towable curtains can be made of any material that can be deformed in response to pressure and cannot be broken.
A simple material such as plastic, nonwoven fabric, or woven fabric, or a composite material can be used. Furthermore, for opening and closing the pressure vessel,
An opening / closing method using a bolt, an opening / closing method using a Victoria joint, a method using a vise-shaped bracket, or another method may be adopted.

[0014]

As described above, according to the present invention, it is possible to easily and accurately obtain the unit cement amount and the unit fine aggregate amount of fresh concrete.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an apparatus used to execute a method for evaluating fresh concrete according to an embodiment of the present invention.

FIG. 2 is a view showing a mixing list of fresh concrete.

FIG. 3 is a diagram showing a unit volume mass and a unit water amount of mortar.

FIG. 4 is a graph showing a relationship between a unit volume of mortar and a unit water amount.

FIG. 5 is a diagram showing a schematic configuration of an apparatus used to execute a method for evaluating fresh concrete according to an embodiment of the present invention.

FIG. 6 is a view showing an apparatus used to carry out a method for evaluating fresh concrete according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Pressure vessel 2 ... Measuring instrument 11 ... Cylindrical vessel 12 ... Lid 13 ... Air chamber 14 ... Pressurizing piston 15 ... Pressure gauge F ... Mortar

Claims (2)

[Claims] 1. After converging the amount of air contained in a mortar obtained by removing coarse aggregate from fresh concrete, a unit volume mass and a unit water amount of the mortar are measured, and the measured unit volume mass and unit of the mortar are measured. A method for evaluating fresh concrete, wherein one or both of a unit cement amount and a unit fine aggregate amount of fresh concrete are obtained based on a water amount. 2. A unit weight of the mortar is measured using a transmission type gamma ray density meter or a balance and a container, and a unit water amount of the mortar is measured using a neutron moisture meter or a microwave moisture meter. The method for evaluating fresh concrete according to claim 1.