JP3843592B2 - Construction management method for cast concrete - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a construction management method for cast concrete, and more particularly to a construction management method for guaranteeing the quality of cast concrete based on objective data.
[0002]
[Prior art]
In order to guarantee the quality of a concrete structure designed according to the performance regulations, it is necessary to objectively prove that the individual performance of the structure satisfies the required performance.
[0003]
When such quality assurance is performed, a destructive test cannot be performed after the concrete is hardened. Therefore, construction management at the concrete placing stage is very important.
[0004]
In the construction management at the concrete placement stage, the following three items are necessary for quality assurance.
(1). Confirmation of driving material (identification of concrete and bleeding water, rainwater, oil, or no material)
(2). Concrete compaction degree (3). Presence or absence of occurrence of cold joints As a means of performing construction management of such items, for example, the degree of compaction of concrete placement is determined by the engineer in charge of compaction by checking the local placement state visually. This is done by observing.
[0005]
However, such a conventional construction management method has the following technical problems.
[0006]
[Problems to be solved by the invention]
That is, in visual observation by engineers, when placing a large amount of concrete at once, the engineer's eyes often do not reach every corner. Since it cannot be judged objectively, the quality assurance of the concrete structure was extremely insufficient.
[0007]
By the way, in recent years, high-fluidity concrete that has self-filling properties and does not need to be compacted has been developed and is beginning to spread. In high-fluidity concrete, compaction is not required, so it is not necessary to measure the degree of compaction in construction management, but grasping the filling status is an important requirement, so electrical resistance and capacitance sensors are used. The local filling situation is measured.
[0008]
However, even if such a sensor is used, there is a problem that quality assurance of the entire concrete structure cannot be guaranteed.
[0009]
The present invention has been made in view of such problems, and an object of the present invention is to provide a concrete placement construction management method capable of quality assurance based on data capable of objective judgment. There is to do.
[0010]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present invention provides a method for managing construction of cast concrete, in which a level sensor including a pair of electrode rods extending opposite to each other along the height direction of the cast concrete is installed. One level sensor checks the concrete placement material based on the capacitance between the electrode bars, and measures the height of the cast concrete based on the change in capacitance. The presence or absence of the possibility of the occurrence of cold joints is obtained by determining the degree of compaction of the concrete from the change in capacitance before and after compacting the placed concrete and measuring the change over time in the launch height. Judgment was made.
According to the construction management method for the cast concrete thus configured, the concrete placement material is confirmed based on the capacitance between the electrode rods of the level sensor, and the cast concrete is determined based on the change in the capacitance. By measuring the launch height of the concrete, determining the degree of compaction of the concrete from the change in capacitance before and after compaction of the placed concrete, and measuring the time-dependent change in the launch height, Since the presence or absence of occurrence is judged, a third party can objectively confirm the construction state.
Here, the confirmation of the placing material of the concrete of the present invention means the identification of the state where there is no concrete and bleeding water, rainwater, oil or material.
The cast concrete is high-fluidity concrete, and is placed from a plurality of openable / closable inlets provided in a pressure feed pipe arranged in a placement direction, and the electrode rods are arranged before and after the inlet. Thus, the launch height can be measured.
According to this structure, the flow distance of the high fluidity concrete can be managed.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows an embodiment of a construction management method for cast concrete according to the present invention.
[0012]
The construction management method shown in the figure shows a case where the present invention is applied to construction of a LNG tank breakwater. The breakwater has a cylindrical shape with a height of about 38m, an inner diameter of about 84m, and a wall thickness of about 80cm. The concrete is placed in a state of being divided into 9 lots along the line and divided into 6 lots along the circumferential direction.
[0013]
In the construction management method of the present embodiment, at least a pair of level sensors 10 are installed in the cast concrete, and a difference in residual voltage based on a change in capacitance between the level sensors 10 is measured.
[0014]
Here, the inventors of the present invention have a concrete filling sensor that has been put to practical use in high-fluidity concrete. Therefore, it was learned that there is no suitable sensor that can obtain measurement results at many points, and a level sensor 10 as shown in FIG.
[0015]
The level sensor 10 shown in FIG. 2 includes a pair of opposed electrode rods 10a and an electrode support plate 10b having a concave cross section. The electrode rod 10a has a length of 4.5 m in accordance with the work, and a lower end and an upper end side are fixed to the support plate 10b by a fixing member 10c for maintaining a gap.
[0016]
The upper end of the electrode rod 10a is connected to a relay terminal box 10d, and a cable 10e electrically connected to the electrode rod 10a is extended from the relay terminal box 10d.
[0017]
A switch box 12, a data logger 14, and a personal computer 16 shown in FIG. 6 are connected to the cable 10e. The switch box 12 applies a set voltage to the electrode rod 10a and takes out an output voltage between the electrode rods 10a by switching the switch.
[0018]
The data logger 14 collects data sent from the switch box 12. The personal computer 16 performs necessary arithmetic processing on the data collected by the data logger 14 and graphically displays the launch height and the like.
[0019]
In the preliminary experiment, mortar in which water: cement: fine aggregate was mixed at a mass ratio of 1: 1: 3 was increased by 10 cm from the lower end side every 15 minutes, and the launch height was increased at a rate of 40 cm per hour. The height was made higher.
[0020]
The measurement principle of the launch height of the level sensor 10 used in this preliminary test will be described as follows. A large number of ions are present in fresh concrete (mortar), and when concrete is interposed between the electrode bars 10a, a capacitor using concrete as an electrolyte is formed.
[0021]
Since this capacitor changes as concrete is launched, it is considered that the level sensor 10 has capacitors having a certain electric resistance (specific resistance) connected in parallel as shown in FIG.
[0022]
That is, as concrete is placed between the electrode rods 10a and the launch height increases, the number of capacitors connected in parallel increases and the capacitance increases.
[0023]
When such a change in capacitance is measured, the concrete launch height can be determined. Therefore, first, a constant voltage is applied between the electrode rods 10a for a certain period of time, an electric charge is applied to the electrode rods 10a, and the voltage between the electrode rods 10a is measured after a certain period of time has elapsed.
[0024]
A schematic diagram of this measurement circuit is shown in FIG. In this measurement circuit, the relationship Vin≈E (t) and Vout = E (t) / (R + 2r) × R is established. However, Vin: applied voltage, Vout: output voltage, E (t): charging voltage, R: fixed resistance, r: specific resistance Therefore, in the preliminary test, first, the electrode rod from the data logger 14 through the switch box 12 In this method, after applying a DC voltage of Vin = 2v for 10 msec for 10 msec and providing a non-application time of 80 msec, this was repeated 21 times per measurement.
[0025]
Then, using another channel, the output voltage Vout between the electrode rods 10a after 180 msec had elapsed from the end of voltage application was measured to the side. The measurement result at this time is shown in FIG.
[0026]
As is apparent from the results shown in FIG. 5, the output voltage Vout between the electrode rods 10a and the mortar launch height become a cubic curve having a substantially proportional relationship. It was confirmed that measurement was possible.
[0027]
Further, in the level sensor 10 based on the measurement principle described above, since the measurement principle depends on the charging characteristics of the material to be measured interposed between the electrode rods 10a, if calibration curves having different material types are prepared in advance. The material used for the concrete can be confirmed, and the height of the concrete rise can be measured more accurately.
[0028]
Based on the above preliminary tests, in the construction work on the breakwater, as shown in FIG. 1 ●, an electrode rod having a total length of about 7 m within a range of about 1/6 of the entire circumference and a circumference of 45 m. Nine L0 to L8) 10a were installed.
[0029]
As shown in FIG. 6, each electrode rod 10 a was disposed so as to be located on both sides of an openable / closable inlet 22 provided in the pressure feeding pipe 20 of the cast concrete.
[0030]
A switch box 12, a data logger 14, and a personal computer 16 are connected to the electrode rod 10a. Each charging port 22 is provided with an electric gate valve 24, and the degree of opening and closing of the electric gate valve 24 is controlled by a control signal sent from the personal computer 16.
[0031]
The cast concrete used in the construction is a high strength, high fluidity concrete having a self-filling property of a slump flow of 65 cm and a design standard strength of 60 N / mm ² using a combination of low heat Portland cement and an expansion material.
[0032]
The applied voltage and output voltage of each electrode rod 10a were measured by measuring the height of the cast concrete under the same conditions as in the preliminary test described above. FIG. 7 shows the average value of the measurement results of each electrode rod 10a.
[0033]
8 and 9 show an example of the monitor screen (PC 16) of the construction state in the measurement section. By performing such monitoring, the following control becomes possible.
[0034]
(1) From the monitor image, it is possible to grasp the general concrete placement condition when constructing the breakwater, and to confirm the average concrete rise speed in the formwork in real time. In the example shown in Fig. 9, it is possible to objectively determine that the concrete has been placed stably with an average launch speed of 1 m / h.
[0035]
(2) Looking at the monitor image, if a certain place is launched extremely fast or launches slowly, control is performed from the personal computer 16 to the electric gate valve 24 to avoid deformation of the formwork and uneven load. Such an inconvenience can be avoided by sending a signal and adjusting the opening of the valve 24.
[0036]
(3) In terms of the quality of the cast concrete, as shown in Fig. 8, by finding the amount of change per 30 minutes at a certain location, it is possible to find the location where the launch has stopped. Although the presence or absence of the occurrence cannot be confirmed directly, the occurrence can be avoided by controlling the insertion port 22.
[0037]
(4) Since the change of each flow gradient in the section where the electrode rod 10a is installed is obtained as shown in FIG. 10, it is possible to easily determine the degree of slump flow of the high-fluidity concrete being placed. it can.
[0038]
In the above example, since the present invention was applied to the construction of a breakwater using high-fluidity concrete, the degree of compaction was not measured, but when concrete that requires compaction was used. By measuring changes in capacitance and residual voltage before and after the compacting operation, it is possible to confirm the degree of compaction objectively.
[0041]
【The invention's effect】
As described above in detail, according to the construction management method for cast concrete according to the present invention, quality assurance can be performed based on data that can be objectively determined.
[Brief description of the drawings]
FIG. 1 is an explanatory plan view of a breakwater to which a construction management method for cast concrete according to the present invention is applied.
2A and 2B are a plan view and a side view showing an example of an electrode used in the construction management method according to the present invention.
FIG. 3 is an explanatory diagram showing the measurement principle of the same electrode.
FIG. 4 is an explanatory diagram of an electric circuit in a measurement state of the electrode.
FIG. 5 is a graph showing the measurement results of the mortar launch height using the same electrode.
6 is an overall layout view of devices used in the construction management method for the breakwater shown in FIG. 1. FIG.
7 is a graph showing a change with time of the height of cast concrete in the construction management method shown in FIG. 6. FIG.
8 is a diagram showing an example of a monitor screen for the height of cast concrete in the construction management method shown in FIG. 6. FIG.
FIG. 9 is a diagram showing another example of a monitor screen for the height of cast concrete that has been placed in the construction management method shown in FIG. 6;
10 is a graph showing the change with time of the gradient between electrode rods in the construction management method shown in FIG. 6. FIG.
[Explanation of symbols]
10 electrode 10a electrode rod 12 switch box 14 data logger 16 personal computer

Claims (2)

In the construction management method for cast concrete,
Installed a level sensor with a pair of electrode rods that face each other along the height direction of the concrete to be placed,
With one level sensor, the concrete placement material is confirmed based on the capacitance between the electrode bars, and the height of the cast concrete is measured based on the change in capacitance. Determining the degree of compaction of the concrete from the change in capacitance before and after compaction of the placed concrete;
A construction management method for placing concrete, wherein whether or not there is a possibility of occurrence of a cold joint is determined by measuring a change with time of the launch height.   The cast concrete is high-fluidity concrete, and is placed from a plurality of openable / closable inlets provided in a pressure feeding pipe arranged in a placement direction, and the electrode rods are arranged before and after the inlet. The method for managing construction of cast concrete according to claim 1, wherein the launch height is measured.

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