JP4451732B2 - Unit water volume measuring device for ready-mixed concrete - Google Patents

Description

  The present invention relates to a unit water amount measuring apparatus for ready-mixed concrete, and more particularly to a unit water amount measuring apparatus for ready-mixed concrete by a neutron moisture meter method that enables quick and easy unit water amount measurement with high accuracy.

  Conventionally, for quality control of ready-mixed concrete, the amount of air was measured at the concrete placement site based on a test using fresh air pressure (JIS A 1128-1999). And for further thorough quality control, it is necessary to measure not only the amount of air but also the unit water volume of ready-mixed concrete.

  For measuring the unit water content of ready-mixed concrete, the measurement sample can be heated and dried with a microwave oven, etc., and the amount of water evaporated can be measured (high-frequency heat drying method) or the specific capacitance of the substance can vary with the amount of water. A method (capacitance method) for estimating the unit water amount from the electrostatic capacity by using it has been used. However, these methods take time to measure and the measurement work is troublesome.

  In view of this, the present inventor has proposed a unit water content measuring method and measuring apparatus for ready-mixed concrete that can be measured quickly and can be easily measured (see Patent Document 1). In this proposal, fast water neutrons with large kinetic energy collide with moisture (strictly hydrogen atoms) in ready-mixed concrete, and the number of neutrons (thermal neutrons) that lost energy due to the collision is detected to measure the unit water volume. Is. This is a measurement method using a so-called neutron moisture meter method based on the principle that the amount of thermal neutrons generated increases as the amount of moisture (hydrogen atoms) in the substance increases.

  In this proposal, after measuring the air volume (JIS A 1128-1999), the sample vessel used for this measurement is used as it is, and a rod-shaped thermal neutron detector with a neutron source attached at the center of the sample vessel is placed. By detecting the number of thermal neutrons, the unit amount of water is quickly and accurately calculated from the relationship between the number of thermal neutrons obtained in advance and the amount of water in the sample container.

As a result of conducting research on the measurement of water content by the neutron moisture meter method, the present inventor can pass fast sample neutrons from the neutron source through the sample container. It was discovered that the amount of water could not be measured accurately because it also detected thermal neutrons by colliding with hydrogen atoms such as moisture on the ground or floor surface, resulting in thermal neutrons. This knowledge has led to the completion of a measuring apparatus with higher measurement accuracy.
JP 2004-330898 A

  An object of the present invention is to provide an apparatus for measuring the unit water content of ready-mixed concrete, which can measure the unit water amount of ready-mixed concrete quickly and easily and can improve the measurement accuracy.

In order to achieve the above object, a unit water amount measuring apparatus for ready-mixed concrete according to the present invention is a sample container used for an air amount test defined by JIS A 1128, containing ready-mixed concrete on a top plate placed on a support. And a thermal neutron detector for detecting the amount of thermal neutrons generated by changing the fast neutrons are installed in the ready-mixed concrete in the sample container. In the measuring apparatus for measuring the unit water amount of ready-mixed concrete by immersing a rod-shaped sensor and installing it in the center of the sample container, the height from the lower end of the support to the top plate is 40 cm or more, and the sample A disc-shaped upper lid mounted on the upper part of the container is provided, the upper lid has a preliminary accommodating portion formed by being recessed upward, and a through hole in the central portion and an insertion erected upward from the through hole With the guide tube To, is characterized in that to allow insertion of the sensor.

According to the unit water amount measuring apparatus for ready- mixed concrete of the present invention, since the sample container for storing ready-mixed concrete used for the air amount test specified in JIS A 1128 is used as it is, preparation for measurement can be facilitated.

  Also, a top plate is placed on the support, the height from the lower end of the support to the top plate is set to 40 cm or more, and the sample container is placed on this top plate and measured by a sensor. It is possible to reduce the influence of hydrogen atoms such as moisture on the ground or floor surface and to make accurate measurement quickly and easily.

  Hereinafter, the unit water amount measuring apparatus of the ready-mixed concrete of this invention is demonstrated based on embodiment of FIG. A disc-shaped upper lid 2 having a through-hole 5 in the center is covered with the upper part of the sample container 1 that accommodates the ready-mixed concrete P used in the air quantity test of fresh concrete (JIS A 1128-1999). A rod-shaped sensor 8 is inserted into the through-hole 5 and arranged at the center of the sample container 1. The sample container 1 is placed on a top plate 12 installed on the upper surface of a box-like support 13. The leg portion of the top plate 12 has a screw type structure that can be expanded and contracted, and the top surface of the top plate 12 can be set horizontally.

  The height H from the support leg 17 to the top 12 is set to 40 cm or more. That is, when the measuring device is placed directly on the ground, the height from the ground 19 to the top surface of the top plate 12 is 40 cm or more. In this embodiment, the independent top plate 12 is arranged on the upper surface of the support 13. However, the support 13 and the top 12 may be integrated.

  An operation / display panel 14 constituting the measurement information processing apparatus is arranged on the front surface of the support 13, and an arithmetic device and a storage device (both not shown) as other components of the measurement information processing apparatus are attached to the support 13. It is installed inside. A printer 15 for outputting the measurement results and an upper lid housing portion 16 for housing the upper lid 2 are also arranged on the front surface of the support 13. Although a rechargeable battery (not shown) serving as a power supply device is installed in the support 13, for example, a DC power supply device that receives a DC power supply from the outside may be provided. A sensor holder 18 that can hold the sensor 8 when the measurement is not performed is provided on the side surface of the support 13. In addition, you may make it provide a measurement information processing apparatus etc. and the support body 13 separately.

  As shown in FIG. 2, the upper lid 2 covering the upper part of the bottomed cylindrical sample container 1 is a disc shape having an outer collar portion 4, and is provided with a preliminary accommodating portion 6 formed by being recessed in a columnar shape upward. Yes. A through hole 5 is provided at the center in the plane direction, and a cylindrical insertion guide tube 3 is erected from the through hole 5 upward. The diameter of the through-hole 5 and the inner diameter of the insertion guide cylinder 3 are slightly larger than the outer diameter of the sensor 8, and the sensor 8 can be inserted vertically. In addition, on the lower surface of the outer brim portion 4 of the upper lid 2, three center alignment projections 7 that protrude downward and come into contact with the inner peripheral surface of the sample container 1 are provided.

  As shown in FIG. 3, the sensor 8 is a cylindrical body having a conical tip, and the neutron source 10 and the thermal neutron detector 9 are installed in a central position in a sealed state. The tip angle T of the sensor 8 is set to 30 to 60 degrees on both sides of the perpendicular line, that is, the tip angle T is set to 60 to 120 degrees.

  As the neutron source 10, a radioactive isotope calfonium (Cf-252) having a radiation dose of 3.7 MBq or less is used, and a helium 3 (He-3) proportional counter is used for the thermal neutron detector 9. Yes.

  From the rear end of the sensor 8, the neutron source 10, the thermal neutron detector 9 and each device provided on the support 13 are connected, and a necessary voltage is applied to the helium 3 (He-3) proportional counter. The sensor connection cable 11 is extended.

  The procedure for measuring the unit water amount of the ready-mixed concrete P will be described below with reference to FIGS. In order to improve the water measurement accuracy by the neutron moisture meter method, the neutron source 10 is positioned at the center in the plane direction and the vertical direction of the sample container 1, and the thermal neutron detector 9 is positioned at the center in the plane direction of the sample container 1. It is necessary to extend in the vertical direction.

  After the test by air pressure (JIS A 1118-1999) is completed, the upper lid part (not shown) of the sample container 1 in which the ready-mixed concrete P is accommodated is removed, and the upper lid 2 according to the present invention is attached. The upper lid 2 is made of, for example, stainless steel, has a weight of about 2 to 3 kg, and is fixed to the sample container 1 by its own weight. Since the center alignment protrusion 7 of the upper lid 2 abuts along the inner peripheral surface of the sample container 1 during mounting, the through hole 5 provided in the central portion of the upper lid 2 is positioned at the horizontal center of the sample container 1. Can do.

  The support 13 is usually used by being placed directly on the ground of the concrete placing site. As preparation for measurement, material data of the ready-mixed concrete P is input.

  Next, the sample container 1 is placed on the central portion of the top plate 12, and the sensor 8 is inserted from the insertion guide tube 3 of the upper lid 2 into the through hole 5 and inserted until the tip comes into contact with the bottom surface of the sample container 1. Since the sensor 8 is guided vertically by the insertion guide cylinder 3, the neutron beam source 10 and the thermal neutron detector 9 can be easily arranged at the center in the plane direction of the sample container 1.

  In addition, since the tip of the sensor 8 has a conical shape, the tip is surely brought into contact with the bottom without a coarse aggregate of raw concrete P being interposed between the tip and the bottom of the sample container 1. be able to. The tip angle T is preferably 60 to 120 degrees. If the tip angle T is less than 60 degrees, the durability of the tip is inferior. If the tip angle T exceeds 120 degrees, the performance of removing coarse aggregates decreases. The neutron source 10 is attached to the sensor 8 so as to be positioned at the center in the vertical direction of the sample container 1 when the tip of the sensor 8 comes into contact with the bottom surface of the sample container 1. The sample container 1 can be positioned at the center in the vertical direction, and the measurement accuracy can be improved.

  When the tip of the sensor 8 comes into contact with the bottom surface of the sample container 1, if the insertion position confirmation mark is attached to the surface of the sensor 8 located at the upper end of the insertion guide tube 3 of the upper lid 2, the tip is visually observed. It can be confirmed that it is in contact with the bottom surface of the container 1.

  Since the sample container 1 is filled with the ready-mixed concrete P, when the sensor 8 is inserted, the ready-mixed concrete P corresponding to the inserted volume moves upward, but the preliminary accommodating portion 6 provided in the upper lid 2 has this volume. Therefore, the moved ready-mixed concrete P is accommodated in the preliminary accommodating portion 6. Therefore, the ready-mixed concrete P does not leak out from the insertion guide cylinder 3, and the volume of the ready-mixed concrete to be measured is not reduced, and the outside is not soiled.

  When measurement is started in this state, fast neutrons with large kinetic energy emitted from the neutron source 10 collide with hydrogen atoms in the raw concrete P in the sample vessel 1 to become thermal neutrons that have lost energy. By detecting the amount of thermal neutrons by the thermal neutron detector 9, the amount of moisture in the substance can be indirectly measured.

  If the height from the ground surface 19 to the lower surface of the sample container 1 is 40 cm or more as shown in an example to be described later, the influence of hydrogen atoms such as moisture on the ground surface 19 is hardly affected. Since it was found that the measurement can be performed without receiving, the present measurement apparatus in which the height H from the support leg 17 to the top plate 12 is 40 cm or more can perform a measurement with high accuracy.

  Since this height H is 40 cm or more from the viewpoint of measurement accuracy, it is determined in consideration of the workability of placing the sample container 1 on the top plate 12 under these conditions. Since the weight of the sample container 1 containing the ready-mixed concrete P is about 20 kg, it is preferably as low as possible, for example, 40 to 100 cm, and more preferably about 40 to 60 cm.

  The amount of thermal neutrons detected here is affected by the moisture contained in the ready-mixed concrete P and aggregates. The unit water amount of the concrete P can be obtained. For example, the measurement for 10 seconds is repeated 7 times, and the average value of 5 times data excluding the highest value and the lowest value is set as the unit water amount of the ready-mixed concrete P.

  As described above, in the measurement apparatus of the present invention, the measurement is completed in about 70 seconds from the start of measurement, and the measurement result is displayed on the operation / display panel 14 and output by the printer 15, so that it can be measured quickly and easily. Can do. Also, troublesome work is not required for measurement preparation.

  Even if this measuring apparatus is directly installed on the ground 19, the height from the ground 19 to the top plate 12 is 40 cm or more. Therefore, it is possible to accurately measure the unit water amount without being affected by hydrogen atoms such as moisture on the ground 19. Is possible. In the embodiment, the place where the measurement device is installed is the ground 19. However, when measurement is performed indoors or the like, accurate measurement can be performed without being affected by moisture (hydrogen atoms) on the floor surface of the measurement place. can do.

In addition, by integrating the measurement information processing apparatus, the printer 15, and the rechargeable battery into the support body 13, space can be used without waste and a compact measurement apparatus can be obtained.
Calfornium as the neutron source 10 has a half-life of 2.65 years, and the dose decreases with time, but the number of days of use of calfornium is stored in the storage device, so that changes in dose with time can be grasped. Therefore, accurate measurement can be performed by calibration.

  The same ready-mixed concrete whose unit water volume is known in advance is squeezed into a sample container used for the air volume test (JIS A 1128) and accommodated in a weight of about 16 kg. A bar-shaped sensor using elemental calfornium (Cf-252) and a helium 3 (He-3) proportional counter as a thermal neutron detector is immersed in the ready-mixed concrete of the sample container and placed in the center of the sample container. Under the common condition of installation, after measuring the air volume in advance, we measured the unit water volume of ready-mixed concrete.

  As shown in Table 1, six types of supports having different heights were prepared, and measurements (six different height conditions) with the sample container placed on the top plate of these supports, and the support In addition to the measurement with the sample placed directly on the ground, the measurement was performed under seven different height conditions. The support was a rectangular parallelepiped frame made of stainless steel, and the top plate was a stainless steel flat plate having a thickness of about 0.4 cm.

  Under these respective height conditions, the influence of hydrogen atoms such as moisture on the floor surface due to the measured height was confirmed with three floor surfaces (floor surface A, floor surface B, and floor surface C) on which the measuring device is installed. The measurement for 10 seconds was repeated 7 times under each condition, and the average value of 5 measurement results excluding the highest value and the lowest value was taken as the measurement value under that condition. The measurement results are as shown in Table 1.

  The support height h in the table is the height from the lower end of the support to the top surface of the top plate. Table 1 shows the dispersion V representing variation in measured values as an index indicating the influence of hydrogen atoms such as moisture on the floor surface at each support height h.

  From the dispersion V shown in FIG. 4, the support height h is 40 cm or more, that is, the height from the ground to the lower surface of the sample container is 40 cm or more, thereby reducing the influence of hydrogen atoms such as moisture on the floor surface with high accuracy. It was confirmed that measurement was possible.

It is a partial cross section front view which shows an example of the unit water amount measuring apparatus of the ready-mixed concrete of this invention. It is a longitudinal cross-sectional view which shows the shape of the upper cover which concerns on this invention. It is a longitudinal cross-sectional view which shows the state which installed the sensor in the sample container in this invention. It is a graph which shows dispersion | distribution of the measured value of the unit amount of water measured by changing height conditions.

Explanation of symbols

1 (for measuring the amount of fresh concrete air) Sample container 2 Upper lid 3 Insertion guide 4 Outer flange 5 Through hole 6 Preliminary storage 7 Center alignment protrusion 8 Sensor 9 Thermal neutron detection unit 10 Neutron beam source 11 Sensor connection code 12 Top plate 13 Support body 14 Operation / display panel 15 Printer 16 Upper lid storage part 17 Support body leg part 18 Sensor holder 19 Ground

Claims (3)

A sample container used for an air amount test specified in JIS A 1128 containing fresh concrete is placed on a top plate placed on a support, and fast neutrons are placed in the ready concrete in the sample container. A neutron beam source that emits and a thermal neutron detector that detects the amount of thermal neutrons generated by the change of fast neutrons is inserted in the center of the sample vessel by immersing a rod-shaped sensor, In the measuring apparatus for measuring the unit water content of ready-mixed concrete, the height from the lower end of the support to the top plate is 40 cm or more, and a disc-like upper lid is provided on the upper part of the sample container, Of the ready-mixed concrete that has a preliminary accommodating portion formed by being recessed and has a through hole in the center portion and an insertion guide cylinder standing upward from the through hole so that the sensor can be inserted therethrough . Unit water volume measuring device .   The said concrete support body is box-shaped, The measurement information processing apparatus, the output device, and the power supply device were integrally provided in this support body, The unit water amount measuring apparatus of the ready-mixed concrete of Claim 1. The unit water amount measuring apparatus for ready-mixed concrete according to claim 1 or 2 , wherein the tip of the sensor has a conical shape with a tip angle of 60 to 120 degrees.

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