JP2015180801A - Resistance value measurement formwork for placed concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an effective formwork to be used in a method to perform highly accurate management of quality determination, formwork removal timing determination, formwork removal timing setting, lifetime estimation, and construction information.SOLUTION: A resistance value measurement formwork for placed concrete includes: pairs of a plurality of electrodes arranged to be arrayed at specified equal intervals while being protruded into the formwork so that at least one end of each is embedded in the placed concrete; electrifying means; and measuring means for measuring values for currents flowing in the respective electrodes and potential differences between the plurality of electrodes. The electrodes each having a part embedded in the placed concrete, in which an electrifying part for electrifying the placed concrete is kept exposed and a portion other than the electrifying part is kept insulated by and covered with an insulating member. The surface of the electrode at its portion equivalent to a desired electrification depth is kept exposed, thus enabling an electrification depth to be set by properly changing the position of the electrifying part according to a set value for the electrification depth.

Description

  The present invention relates to a formwork for measuring resistance of cast concrete. Including concrete uses, it is effective to use for the concrete judgment method, the demolding time judgment method, the demolding time setting method, the concrete structure life estimation method, and the construction information management method. Regarding the concrete form for measuring the resistance value of concrete installed, in detail, it was placed by fitting the measurement data obtained during the curing of the concrete placed in the actual structure to the measurement data obtained by the specimen. The present invention relates to a formwork which is effective for use in a method of determining quality of concrete and setting, estimating and managing various conditions based on the determination.

  Curing of concrete is known to have a significant effect on long-term strength development and durability, and neglecting curing causes premature deterioration. Therefore, it is important to properly cure the placed concrete.

  In order to make concrete last a long time, not only strength but also durability against various types of deterioration is indispensable. It suppresses defects such as voids and cracks in concrete, and in particular makes the concrete surface dense and free of defects. This is very important. In this regard, it is known that concrete with insufficient curing generally has a rough void structure, and it is known that premature deterioration is likely to occur as compared to those with appropriate curing.

  And, as a criterion for judging the end time of the applied curing, the provision that the mold can be removed when the desired compressive strength is expressed, and the subsequent curing is performed with the cement type being kept in a wet state. Only the number of days required for curing is shown in relation to the ambient temperature, and the judgment of the current curing end time is not made for actual structures. To the extent that is being done.

  In particular, in the case of an actual structure, when the concrete is in the formwork, the time of strength development is unclear. Therefore, after demolding, the concrete is subjected to a non-destructive test and inspected or sealed on site separately from the structure A method is used in which a control specimen is prepared and subjected to a compression test, or the number of days until demolding is uniquely determined.

  In Patent Document 1, the temperature in the concrete in which the lining concrete which is an actual structure is placed is measured, and the specimen is cured under the same conditions as the measured temperature to perform a strength test. There has been proposed a technique for determining the demolding time by estimating the replacement of the strength of the specimen with the strength of the actual structure.

  Neither method actually captures the curing status of the actual structure, so it remains within the scope of estimation and cannot determine the curing status of the actual structure. Insufficient strength may be confirmed after molding, and in this case, it was necessary to carry out a corresponding prescription for ensuring strength. Therefore, it was necessary to ensure a high safety factor when determining the end of curing.

JP 2009-002721 A

Therefore, the first problem of the present invention is to directly measure the concrete in the mold during curing, which is an actual structure, so that it is possible to determine the quality with high accuracy, the determination of the demolding time, the setting of the demolding time, the life estimation. -To provide a method capable of managing construction information.
A second object of the present invention is to provide an effective formwork used in the quality determination method.

  The present invention for solving the second problem has the following configuration.

1. It is a formwork for measuring the resistance of cast concrete,
A set of a plurality of electrodes arranged so as to be juxtaposed at specific equal intervals in a state of protruding into the mold so that at least one end is buried in the placed concrete;
Energization means connected to each electrode so as to be energized;
Measuring means for energizing each electrode through the energizing means, and measuring a current value flowing through each electrode and a potential difference between the plurality of electrodes;
Have
Of the portion embedded in the placed concrete, the electrode is in a configuration in which the energized portion with the placed concrete is in an exposed state, and the portion other than the energized portion is in an insulating covering state with an insulating member,
When the electrode is insulated with the insulating member, the position of the energization portion is appropriately changed in accordance with the set value of the energization depth by exposing the surface of the electrode for the portion corresponding to the desired energization depth. It is a configuration that can set the energization depth by
A formwork for measuring the resistance value of concrete placed.

2. 2. The mold for measuring a resistance value of placed concrete according to the above 1, wherein the plurality of electrodes is a set of four electrodes arranged in parallel at a specific equal interval. frame.

3. The set of the electrodes has a configuration in which a current-carrying portion is provided with the concrete placed at a position where the cover is buried at a cover depth in the concrete placed from the inner surface of the mold. A formwork for measuring a resistance value of concrete placed according to 1 or 2.

4). The form for measuring the resistance value of the placed concrete according to any one of the above items 1 to 3, wherein the electrode is a wire.

  The invention for solving the first problem has the following configuration.

[1] Using the measurement data and performance test results obtained by the test specimen, and determining the quality of the placed concrete by fitting the measured data during curing of the placed concrete in the actual structure. There,
Using a test body in which at least a part of each electrode is buried in concrete with a set of a plurality of electrodes arranged in parallel at specific equal intervals,
The specimen is created for each condition in which the curing period (demolding time) is varied, and the transition of the resistance value during the curing of each specimen is measured and recorded by the electrode,
For each of the obtained specimens, at least one performance test selected from compressive strength, neutralization depth, vacuum water absorption area ratio, salt penetration depth, and air permeability coefficient is performed, and the performance test result is recorded.
The resistance value, the curing period (demolding time), the performance test result, the resistance value according to the progress of the hydration reaction of concrete, the curing period (demolding time), and the performance test result. Understand the correlation,
On the other hand, a set of a plurality of electrodes arranged in parallel at specific equal intervals is arranged so that at least a part of each electrode is embedded in a portion located in the concrete cover of the actual structure. Put concrete in the frame, measure the transition of the resistance value during curing of the concrete cover part by each electrode,
A method for determining the quality of placed concrete, wherein the measured resistance value is applied to the resistance value of the correlation to determine the quality of the concrete on which the actual structure is placed. .

[2] Based on the result of the correlation in the specimen described in [1] above, a resistance value at the time when the required demolding time strength in the actual structure is satisfied is obtained,
A set of electrodes arranged in parallel at specific equal intervals is arranged so that at least a part of each electrode is embedded in a portion of the actual structure located in the concrete cover, Concrete is placed on the surface, and each electrode is used to measure the transition of the resistance value during curing of the concrete cover portion.
This is a configuration in which the time point when the resistance value of the cast concrete covering portion in a state where the actual structure being cured is in the form during curing reaches the obtained resistance value is determined as the demolding time. A method for determining the demolding time of placed concrete.

[3] Set the required durability when demolding the concrete to be cast from the design life required for a concrete structure that is an actual structure,
By applying this set durability to the durability value in the result of the correlation in the specimen described in [1] above, the resistance value at the time when the set durability is satisfied is obtained,
It is the resistance value of the concrete covering part that is placed in the mold during the curing of the actual structure, and the resistance value measured by the measuring method of the following configuration satisfies the set durability. A method for setting the demolding time of placed concrete, characterized in that the time when the resistance value is reached is set as the demolding time.
[Configuration of resistance measurement method]
A set of electrodes arranged in parallel at specific equal intervals is arranged so that at least a part of each electrode is embedded in a portion of the actual structure located in the concrete cover, The concrete is placed in the concrete, and the transition of the resistance value during the hardening of the cover portion of the concrete is measured by the respective electrodes.

[4] A set of a plurality of electrodes arranged in parallel at specific equal intervals is arranged so that at least a part of each electrode is embedded in a portion of the actual structure located in the concrete cover, Placing concrete in the mold, measuring the transition of the resistance value during curing of the concrete cover portion by each electrode, and recording the resistance value at the time of demolding,
The recorded resistance value at the time of demolding is applied to the resistance value in the correlation result in the specimen described in [1] above, and the compressive strength and / or the correlation with the applied resistance value are correlated. Or seek neutralization depth,
Concrete characterized in that it is a configuration for estimating the life, which is the useful life (≈ rebar corrosion start time) of a concrete structure which is an actual structure from the value of the obtained compressive strength and / or neutralization depth. A method for estimating the lifetime of structures.

[5] Based on the result of the correlation in the specimen described in [1] above, obtain a resistance value at the time when the required demolding time strength in the actual structure is satisfied,
A set of electrodes arranged in parallel at specific equal intervals is arranged so that at least a part of each electrode is embedded in a portion of the actual structure located in the concrete cover, Concrete is placed on the surface, and each electrode is used to measure the transition of the resistance value during curing of the concrete cover portion.
Construction in which the resistance value of the cast concrete covering portion in the form during curing of the actual structure being measured reaches the resistance value determined as the demolding time and is demolded And
A method for managing construction information of a concrete structure, wherein the resistance value measured during the construction is recorded and stored together with the construction conditions.

[6] Configuration that enables transmission of resistance value data measured during construction together with construction condition data to a location remote from the construction site by wireless or wired, and confirmation of the construction status at the construction site at this remote location The method for managing construction information for a concrete structure according to [5] above, wherein

[7] The above-mentioned structure is characterized in that a database in which a plurality of pieces of construction information are accumulated is constructed by recording and saving resistance value data measured during construction at a plurality of construction sites together with construction condition data. [5] or [6], the construction information management method for concrete structures.

[8] It is characterized in that it is configured to predict the progress of deterioration of a concrete structure, which is an actual structure after construction, based on resistance value data and construction condition data measured during recording and storage. The construction information management method for a concrete structure according to any one of [5] to [7] above.

[9] When the deterioration of a concrete structure, which is an actual structure after construction, is discovered, the cause of deterioration is estimated based on the resistance value data and construction condition data measured during the recorded and stored construction. The method for managing construction information of a concrete structure according to any one of the above [5] to [7], wherein the method is provided.

  The inventions [1] to [9] are reference inventions of the present invention.

  In the present specification, the “resistance value” not only means the measured resistance value itself, but also within the scope of the present invention when the specific resistance value calculated from the measured resistance value is within the scope of the present invention, Select as appropriate according to various conditions such as concrete type and conditions, and specifications of measuring equipment. Further, “%” indicates “mass%” unless otherwise specified.

  According to the inventions shown in the above [1] to [9], high-accuracy quality determination / demolding time determination / demolding is performed by directly measuring concrete in a formwork in the middle of curing, which is an actual structure. It is possible to provide a method capable of performing time setting, life estimation, and construction information management.

According to the invention shown in the above [1], by grasping the progress of the hydration reaction of the specimen, it is possible to grasp the progress of the hydration reaction during curing of the cast concrete cover portion. The quality of the placed concrete can be determined.
In particular, according to the study by the present inventors, it has been found that the resistance value immediately before demolding is correlated with the performance (quality) of concrete such as compressive strength and neutralization depth. The compressive strength and the neutralization depth of the cover part, which are important for measuring durability and life, can be grasped by measuring the resistance value immediately before demolding. From this result, the actual structure was placed. It becomes possible to estimate the durability and life of concrete.

  According to the invention shown in the above [2], the cast concrete in a state where the actual structure is in the process of being cured can be removed at a very appropriate time without excess or deficiency. It is possible to obtain an excellent high-quality concrete structure without generating waste during the construction period.

  According to the invention shown in the above [3], from the service life required in the design stage, it is possible to ensure the required durability for the demolding time of the cast concrete of the actual structure, and waste the construction period. An appropriate time not to be generated can be set in advance as a design item.

  According to the invention shown in [4] above, from the data on the actual situation of construction of the actual structure, the service life of the concrete structure that is the actual structure (≈ rebar corrosion start time) is estimated. Can do. That is, the life of the cast concrete can be known at the stage of demolding.

  According to the invention shown in the above “5”, the construction information can be managed by recording and storing the information related to the curing of the constructed concrete structure as numerical data.

  According to the invention described in [6] above, it is possible to check the construction status at a location away from the construction site.

  According to the invention described in [7] above, past records can be referred to and confirmed by accumulating construction information in a database, and construction techniques can be improved and improved based on past records that have been referenced and confirmed. It can be effectively used when planning.

  According to the invention shown in the above [8], since the progress of the deterioration of the concrete structure after the construction is predicted, it is possible to prepare measures such as repairs corresponding to the deterioration in advance. Preventive measures can be taken.

  According to the invention shown in the above [9], when the constructed concrete structure is deteriorated, it is possible to perform appropriate repair / repair according to the deterioration by estimating the cause of the deterioration.

  According to the first aspect of the present invention, an effective formwork can be provided for use in the quality determination method.

  According to the present invention described in 2 above, since the resistance value can be measured more accurately, it is possible to further improve the accuracy of each method such as quality determination, demolding time determination / setting, and life estimation. it can.

  According to the present invention shown in 3 above, it is possible to more accurately measure the resistance value of the fogging part, which is an important part in judging the quality, durability, and life of the concrete structure.

  According to the present invention shown in 4 above, it is possible to measure an appropriate resistance value using a material that can be easily obtained at a very low cost.

  In particular, according to the present invention shown in 1 above, the measurement depth in the placed concrete can be set to a desired depth very easily by appropriately selecting the position of the energizing portion that exposes the electrode. be able to. Accordingly, various configurations such as a cover having a cover of about 25 mm, for example, a concrete structure of a general building, a cover having a cover of, for example, about 50 mm, such as a concrete structure for civil engineering, or an unreinforced concrete structure. It can be made to correspond to concrete.

The graph which shows the correlation with the measurement data of the specimen used for the quality judgment method of the placed concrete concerning this invention, and a performance test result (compressive strength, neutralization depth) (the upper figure is compressive strength) Correlation, below is the correlation with neutralization depth) Schematic 3-side view (front view, side view, plan view) showing an example of a specimen used in the present invention Schematic explanatory drawing (main part sectional view) showing the main part of the specimen shown in FIG. A graph showing the change over time in the specific resistance value at each energization depth of a specimen with a normal Portland cement curing period of 5 days The graph which shows the time-dependent change of the specific resistance value of two kinds of energization depths (5 mm and 70 mm) of each specimen in two kinds of sealing curing periods (7 days and 28 days) of two kinds of cement. The graph which shows the time-dependent change of the specific resistance value of the energization depth of 5 mm of each specimen during the curing period of five types of normal Portland cement (1, 3, 5, 7 and 28 days). The graph which shows the time-dependent change of the specific resistance value of the energization depth of 50 mm of each specimen during the curing period of five types of normal Portland cement (1 day, 3 days, 5 days, 7 days and 28 days). A graph showing the relationship between the vacuum water absorption area ratio of 10 specimens during each sealing curing period of two types of cement and the specific resistance value of each specimen immediately before demolding at an energization depth of 50 mm. Schematic explanatory drawing (side view) showing an example of the configuration for measuring the resistance value of the placed concrete according to the present invention Schematic explanatory view showing the main part of FIG. 9 (main part plan view) Schematic explanatory view showing the main part of FIG. 9 (side view of the main part) The schematic block diagram which shows an example of schematic structure of the management method of the construction information of the concrete structure based on this invention

  Hereinafter, the method for determining the quality of the placed concrete according to the present invention, the method for determining the demolding time, the method for setting the demolding time, the method for estimating the life of the concrete structure, the method for managing construction information, and the resistance of the cast concrete The value measurement mold will be described in detail with reference to the accompanying drawings.

The present invention
(1) A method for judging the quality of the placed concrete by fitting the measurement data during curing of the placed concrete in the actual structure using the measurement data and performance test results obtained by the specimen. ,
Based on the information obtained by the quality determination method of (1),
(2) A method for determining the demolding time of the placed concrete in a state where the actual structure is in the middle of curing,
(3) A method for preliminarily setting the demolding time of the cast concrete of the actual structure as a design matter from the service life required in the design stage,
(4) A method for estimating the life of a concrete structure, which is an actual structure, at the time of demolding, which is the service life of the concrete structure (≈ rebar corrosion start time),
(5) A method for recording and storing construction information related to the curing of a concrete structure that has been constructed as numerical data, and managing it.
And each technology,
(6) A formwork for measuring the resistance value of the placed concrete, which is an effective formwork used in the quality determination method of (1),
It consists of the technology.

  Hereinafter, the techniques of the present invention (1) to (6) will be further described.

  The technology of the present invention of (1) was obtained based on the results of finding the characteristics of concrete placed during curing as shown below and intensively studying the characteristics.

That is, the concrete in the middle of curing has a feature that it is easy to energize because it contains a large amount of water, and in the process of hardening, the water is consumed with the hydration reaction of the cement and the water content gradually decreases. .
The present inventors pay attention to the point that it becomes difficult to energize due to the water gap in the concrete being changed to voids due to this water reduction, and between the water content and the electric resistance value of the placed concrete. I found that there is a correlation.

  On the other hand, moisture in the concrete that has not yet solidified is required for the hydration reaction, so the dissipation of moisture inhibits the hydration reaction and causes the deterioration of concrete quality such as strength development and durability. I also grasped that.

  From the above, in order to obtain the required quality required for the placed concrete, the concrete quality is determined by measuring the electrical resistance value of the concrete still in the mold during curing, and this quality is determined. It was found that it is important to end the curing when it is determined that necessary and sufficient curing has been performed.

Therefore, in the present invention, first, specimens with varying curing periods (demolding times) are created for each condition, and the transition of the resistance value during curing of each specimen is measured and recorded by the electrodes,
For each of the obtained specimens, at least one performance test selected from compressive strength, neutralization depth, vacuum water absorption area ratio, salt penetration depth, and air permeability coefficient (Trent method) was performed. Record,
The resistance value, the curing period (demolding time), the performance test result, the resistance value according to the progress of the hydration reaction of concrete, the curing period (demolding time), and the performance test result. Know the correlation.

FIG. 1 is a graph showing an example of this correlation.
The example shown in the upper diagram of FIG. 1 uses ordinary Portland cement (N), which is a representative cement type, and the cement composition is three types of water cement ratio W / C: 45%, 55%, 65%, Unit water volume W: 174 kg / m ² , placement and curing are 5 types of sealing (curing period) on the 1st, 3rd, 5th, 7th, and 28th in the same environment of temperature 20 ° C and humidity 60% 5 is a graph showing the correlation between the resistance value and the compressive strength at the time of demolding of a test specimen obtained by performing demolding in the above and obtaining the period as a sealed curing without moisture dissipation.
Moreover, the lower figure of FIG. 1 shows the resistance value at the time of demolding and the neutralization depth (material age of 56 days) of the specimen with normal Portland cement (N) and 55% cement content. It is a graph which shows correlation.

  Table 1 shows the resistance value, specific resistance value, demolding strength (compressive strength during demolding), and neutralization depth (material age 28 days, material) of 55% test specimens containing ordinary Portland cement (N). Measurement results and performance test results for 56 days of age and 84 days of age) are shown.

  In the technique of the present invention of (1), during the curing of the concrete in which the actual structure is placed, the resistance value of the correlation of the specimen that best matches the construction conditions of the actual structure among the above-mentioned respective specimens. This is a technique for judging the quality of the concrete of this structure by fitting the measured resistance value.

  As a specific configuration example of the specimen, as shown in FIG. 2, the specimen 7 has a width of 1350 mm, a depth of 250 mm, and a thickness of 100 mm, and a composition according to the cement type and blending conditions employed in the actual structure. It is made of concrete, and has a configuration in which at least a part of each electrode 2 is buried in concrete with a set of a plurality of electrodes 2 arranged in parallel at specific equal intervals. FIG. 3 shows the specimen 7 and the electrode 2 in a state of being placed in the mold 8.

In the specimen 7 of this example, four pairs of electrodes 2 are provided, and six pairs of energization depths of, for example, 5 mm, 10 mm, 20 mm, 30 mm, 50 mm, and 70 mm are arranged, and each electrode 2 is energized (not shown). -Connected to the measuring means and energized, and the resistance value is measured for each group. The setting of the energization depth, which is the embedding depth of the electrode 2 in the specimen 7, corresponds to the distance from the inner surface of the mold 8 as shown in FIG. The electrode 2 disposed in the mold 8 is set by a configuration in which the energizing portion 21 with the cast concrete is exposed and the portion other than the energizing portion 21 is in an insulating covering state by an insulating member 22 such as an insulating vinyl film. be able to. That is, when the electrode 2 is insulatively covered with the insulating member 22, the energization depth (L) is set by exposing the surface of the electrode 2 to a portion corresponding to the desired energization depth (L). Accordingly, the position of the energizing portion 21 can be changed as appropriate by changing the position of the energizing portion 21 as appropriate. The interval between the energization portions 21 may be an interval that allows energization with necessary and sufficient contact with the placed concrete, and is preferably about 2 mm.
The actual energization depth of the specimen 7 is set according to the concrete cover setting of the actual structure.
In addition, it is sufficient that the distance between the electrodes 2 is about several centimeters, and specifically, about 5 cm is preferable.

  As the electrode 2 used for measurement, it is preferable to use a wire that is used at various sites such as architecture, landscaping, construction, and events, and is extremely easy to obtain and is a low-cost material. Examples of the wire that can be preferably used as the electrode 2 include those having conductivity such as iron, stainless steel, and copper, and particularly preferably a stainless steel wire having high rust resistance.

  As the performance test of the specimen 7, a publicly known type / method / means can be taken without any particular limitation as a performance test of this type of concrete specimen. In the present invention, the compressive strength / neutralization is performed as the performance test. Do at least one selected from depth, vacuum water absorption area ratio, salt penetration depth, air permeability coefficient (Trent method), especially compressive strength important in judging the durability and life of the resulting concrete structure And performance tests on neutralization depth are particularly important.

  As a means for measuring the resistance value of the specimen 7, any device having a configuration in which the electrode 2 is energized through the energizing means by connection and the current value flowing through the electrode 2 and the potential difference between the plurality of electrodes 2 is measured. A publicly known apparatus can be used without any particular limitation. The voltage may be applied by either direct current or alternating current, but it is preferable to use a pulse wave that is less charged compared to direct current, has a stable value, and can downsize the apparatus compared to alternating current. A measuring means for applying a voltage using a pulse wave facilitates carrying-in / carrying of equipment to the site and enables stable measurement.

  In measuring the resistance value, a current is passed between the two outer electrodes of each set of four electrodes 2, and the resistance value in the specimen 7 is calculated from the potential difference measured between the current amount and the inner two electrodes by the four-electrode method. Or a specific resistance value obtained from the measured value according to the following formula and used as the “resistance value” in the present invention. The measurement is performed from immediately after placing until the material age is 28 days, and it is desirable to use a pulse wave in order to suppress electrification when measuring with direct current upon energization.

Ｉ：４本の電極のうち、外側２本の電極を流れる電流（ｍＡ）
Ｖ：内側２本の電極間の電位差（Ｖ）
ａ：電極の間隔（ｃｍ）
ρ：比抵抗値

I: Current (mA) flowing through two outer electrodes of the four electrodes
V: Potential difference between the two inner electrodes (V)
a: Distance between electrodes (cm)
ρ: Specific resistance value

  Using the measurement data and performance test results obtained by the specimen 8 having the above configuration, the measurement data during the curing of the placed concrete in the actual structure is applied, so that the quality of the concrete in the actual structure Judgment can be made.

  Next, examples of measurement data and performance test results obtained by the specimen will be further described. In the examples shown below, the specific resistance value calculated using the above equation is used instead of the direct resistance value measured as the “resistance value of the present invention”.

Two types of specimens were used: normal portland cement (N) and blast furnace cement type B (BB), which are representative cement types. Cement blending is water-cement ratio W / C: 55%, unit water volume W: 174kg / m ² , casting and curing under the same environment of temperature 20 ° C and humidity 60% RH for 1, 3, 5 The mold was removed at 5 different ages (curing periods) on the 7th and 28th days, and the period was set as a sealed curing without moisture dissipation.

  Five specimens were prepared for each of the two types of cement, and demolding was performed at the five types of ages.

  In addition, the size of 10 specimens in total of 5 pieces was set to a length of 1350 mm, a height of 100 mm, and a thickness of 250 mm as shown in FIGS. 2 and 3.

  Further, each test specimen is configured as shown in FIGS. 2 and 3, and four electrodes arranged in parallel in the width direction at intervals of 50 mm and six sets in the width direction are arranged in parallel. did. The energization depth in the thickness direction of each set of six sets of electrodes was set to six types of 5 mm, 10 mm, 20 mm, 30 mm, 50 mm, and 70 mm. The electrode used was an iron wire, and the embedded portion other than the current-carrying portion having a length of 2 mm was insulated with a shrink vinyl tube.

  Using each electrode of each specimen, a current (30 mA) is applied to the outside of each group of four electrodes, a voltage (15 V) is applied to the inside, and the potential difference between the current flowing through the specimen and the inner electrode is measured. The specific resistance value was calculated using the above formula. The measurement was performed immediately after placing until the material age 28 days. Note that a pulse wave was used to suppress charging during energization.

  In order to compare and verify the relationship between the data of specific resistance values obtained and the durability of each specimen for two types of cement and a total of 10 specimens subjected to five different curing periods for each of the two types. In addition, after the 28-day age period, each specimen was dried in a drying furnace at 40 ° C. for 5 days, and a vacuum water absorption test was performed.

  In the vacuum water absorption test, the side of each specimen is sealed with aluminum tape, water is filled to half the height of the specimen, sucked with a vacuum pump for 3 hours, and after splitting, the cross-sectional area of the area where water is sucked up is measured. The water absorption area was calculated and used as the vacuum water absorption area ratio.

  Table 2 shows data on specific resistance values of concrete cast using normal Portland cement (N).

  Table 3 shows data of specific resistance values of concrete cast using blast furnace cement type B (BB).

Depending on the curing period and energization depth of the two types of placed concrete, “28 days resistivity”, “Resistant immediately before demolding”, “Vacuum water absorption area ratio”, “Salt penetration depth (W / C 60%) Table 4 shows the data of “)”, “Neutralization depth (W / C 55%)”, and “Air permeability coefficient (10 ⁻¹⁶ m ² )”.

  In Tables 2 to 4 and FIGS. 4 to 8 described later, N represents ordinary Portland cement, and BB represents blast furnace cement B type.

  In addition, N-1-5 to N-28-70 in Table 2 and BB-1-5 to BB-28-70 in Table 3 are the types of cement (N is normal Portland cement, BB is Blast furnace cement type B), the number in the middle indicates the type of curing period (days), and the last number indicates the type of energization depth (mm). For example, N-1-5 indicates the specific resistance value in the portion of the energization depth of 5 mm of the test specimen with a normal Portland cement curing period of 1 day, and N-28-7 indicates the test specimen with a normal Portland cement curing period of 28 days. BB-3-30 indicates the specific resistance value in the portion of the blast furnace cement B type curing period of 3 days, and the specific current value is 30 mm, BB-7- 50 shows the specific resistance value in the energization depth 50 mm portion of the specimen of the blast furnace cement type B curing period 7 days.

Based on the data obtained by measurement and described in Tables 2 to 4, the graphs shown in FIGS.
FIG. 4 is a graph showing the change over time in the specific resistance value for each energization depth of a specimen with a normal Portland cement curing period of 5 days, and FIG. 5 shows two curing periods (7 days and 28 days) of two types of cement. ) Is a graph showing the change over time in the specific resistance value of two kinds of energization depths (5 mm and 70 mm) of each specimen, FIG. 6 shows five types of normal Portland cement (1 day, 3 days, 5 days, 7 days, FIG. 7 is a graph showing the change over time of the specific resistance value at 5 mm in the energization depth of each specimen during the curing period of 28 days, and FIG. 7 shows five types of normal Portland cement (1, 3, 5, 7, 28 days). 8) is a graph showing the change over time of the specific resistance value of the energization depth of 50 mm of each specimen during the curing period, FIG. 8 is the vacuum water absorption area ratio of 10 specimens during each curing period of two types of cement and the respective specimens The graph which shows the relationship of the specific resistance value just before demolding of 50 mm of energization depth is shown, respectively.

  From the graph shown in FIG. 4, it can be seen that the specific resistance value for the five days after the end of curing is the same value at any depth, but after demolding, the specific resistance value increases as it approaches the concrete surface. That is, it can be seen that the energization depths of 5 mm, 10 mm, 20 mm, and 30 mm are affected by drying from the outside air, and the 50 mm and 70 mm are not affected by drying.

From the graph shown in FIG. 5, at the energization depth of 5 mm on the curing period of 7 days, the two types of cement show similar specific resistance values. However, after demolding, the specific resistance is influenced by drying from the concrete surface. It can be seen that the value has increased. In particular, Blast Furnace Cement B (BB) was mixed with blast furnace slag fine powder, so the hydration reaction was delayed and affected by drying, so the specific resistance value was higher than that of ordinary Portland cement (N). It has increased.
On the other hand, it can be seen that when the energization is 70 mm on the curing period 28, neither of the two types of cement shows a rapid increase in specific resistance value.
From the graph shown in FIG. 5, it can be determined that the specific resistance value increased by the hydration reaction is about 3 kΩ · m in the blend of this experimental example.

  From the graph shown in FIG. 6, the specific resistance value is shown until the demolding in each curing period from the time-dependent change of the specific resistance value in the portion of the normal Portland cement where the energization depth is 5 mm. After that, the shorter the curing period (especially, one day of curing), the specific resistance value increases rapidly immediately after demolding (the slope of the graph increases rapidly). The longer the curing period, the smaller the tendency of increase in the specific resistance value after demolding. It can be seen that the sum reaction proceeds and the hardened cementitious structure becomes dense. Therefore, by extending the curing period, the hydration reaction can proceed without being affected by drying even after demolding due to the completion of curing, and the quality of the surface part of the concrete can be improved. Since the penetration | invasion of the concrete deterioration factor from can be suppressed, durability of concrete can be improved.

  From the graph shown in FIG. 7 under the same conditions except that the energization depth was set to 50 mm with respect to FIG. From this, it can be seen that the specific resistance value is comparable after demolding in any curing period and that the specific resistance value does not increase rapidly.

  From the results of FIG. 6 and FIG. 7, it is understood that the influence of moisture dissipation from the concrete surface layer on the specific resistance value due to the difference in the energization depth is small during the placement of the mold, and when the curing end time is determined. It can be seen that this is possible by selecting at least one energization depth.

  From the graph shown in FIG. 8, there is a correlation between the specific resistance value and the vacuum water absorption area ratio, and the effect of drying from the concrete surface when the specific resistance value is less than 1 kΩ · m during curing. It turns out that it receives greatly.

  From the above results, the quality, which is the durability of the placed concrete, can be determined by using the specific resistance value of the placed concrete during curing. In particular, by setting various energization depths from the surface part of the concrete to the internal part, the quality of the placed concrete during curing at each set part can be determined at the time when it is in the mold during curing. Can do.

  In addition, since the specific resistance value immediately before demolding indicates the degree of hydration reaction during the period until demolding, the concrete structure is also required from the results of the specific resistance value and durability test. By calculating a specific resistance value that can satisfy the durability to be performed, it is possible to determine an appropriate curing end time.

  Furthermore, even after curing demolding, it is possible to determine the progress of the hydration reaction of the placed concrete after the end of curing by measuring the specific resistance value of the concrete placed according to the present invention. it can. In this case, the depth position at which the specific resistance value is measured is preferably measured at a depth position exceeding 45 mm, which is not easily affected by drying from the concrete surface layer.

  The techniques (2) to (5) of the present invention are respectively performed based on the information obtained by the quality determination method (1) having the above-described configuration described with reference to the examples.

The technology of the present invention of (2) is a method for determining the demolding time of concrete in which an actual structure is placed. As a specific configuration,
Based on the correlation result in the specimen of (1) above, the resistance value at the time when the required demolding time strength in the actual structure is satisfied is obtained,
As shown in FIG. 9 to FIG. 11, at least a part of each of the electrodes 2 is arranged on a portion of the actual structure 3 located on the cover of the concrete 3 with a plurality of electrodes 2 arranged in parallel at a specific equal interval. Is placed from the outside of the mold 1 so as to be embedded, and after placing the concrete 3 in the mold 1 and applying the curing 6, the resistance during the curing of the cover portion of the concrete 3 by the respective electrodes 2 The transition of the value is energized and measured by the measuring means 5 through the energizing means 4 connected to the electrode 2,
A configuration in which the time point at which the resistance value of the covering portion of the concrete 3 placed in the mold 1 in the middle of curing of the actual structure being measured reaches the obtained resistance value is determined as the demolding time. It is.

  As the means for measuring the resistance value of the concrete 3 on which the actual structure is placed, the electrode 2 is energized via the energizing means 4 by connection to the electrode 2 in the same manner as the resistance value measuring means of the specimen. Any publicly known device can be used without any particular limitation as long as the device has a configuration for measuring the value of the flowing current and the potential difference between the plurality of electrodes 2. In addition, it is preferable to use a pulse wave for applying a voltage, which is less likely to be charged than DC and stable in value, and can downsize the apparatus compared to AC.

  For measuring the resistance value, a current (for example, 30 mA in this embodiment) is applied to the outside of each set of four electrodes 2 and a voltage (for example, 15 V in this embodiment) is applied to the inside. The resistance value according to the four-electrode method in which the potential difference between the current flowing through the concrete 3 and the inner electrode 2 is measured may be used as the resistance value of the present invention, or the specific resistance value is calculated using the above formula, The specific resistance value by this four-electrode method may be used as the resistance value of the present invention. As in the case of the specimen, it is preferable to use a pulse wave in order to suppress charging during energization.

  The result of the correlation in the specimen of (1) used in the technique of the present invention of (2) is the result of the correlation of the specimen that best matches the construction conditions of the actual structure among the obtained specimens. Yes, when the measured resistance value is reached by applying the measured resistance value during curing of the concrete on which the actual structure is placed to the resistance value of the best match, demolding is performed. Is the demolding at the most appropriate timing.

Applying the correlation graph shown in the upper diagram of FIG. 1, according to the chart, the compressive strength at the time of demolding is required 10 kN / mm ^2, when the compressive strength of the 10 kN / mm ² is obtained The resistance value at is about 2.7 kΩ for ordinary Portland cement (N) and 55% cement concrete. Therefore, it can be determined that the most suitable timing for demolding is when the resistance value of the placed concrete during curing of the actual structure becomes about 2.7 kΩ. If demolding is performed at such timing, a high-quality concrete structure excellent in durability can be obtained without generating waste during the construction period.

Next, the technology of the present invention of (3) is a method of presetting the demolding time of the cast concrete of the actual structure as a design item from the service life required in the design stage, and as a specific configuration ,
Set the durability such as the neutralization depth and salt penetration depth required when demolding the concrete to be cast from the design life required for concrete structures that are actual structures,
The resistance at the time when the set durability is satisfied by applying the set durability to values such as the neutralization depth and the salt penetration depth in the result of the correlation in the specimen of (1) above. Find the value
Method of measuring the resistance value of the cast concrete covering portion in a state where the actual structure is in the process of being cured and having the same configuration as the above (2) (configuration shown in FIGS. 9 to 11) The time when the resistance value measured by (1) reaches the resistance value at the time when the set durability is satisfied is set as the demolding time.

  The result of the correlation in the specimen of (1) used in the technique of the present invention of (3) is the result of the correlation of the specimen that best matches the design conditions of the actual structure among the obtained specimens. Yes, the most appropriate timing is set in advance as the demolding time when the resistance value that will be measured during the curing of the concrete on which the actual structure has been placed reaches the most suitable resistance value. To do.

Applying the correlation graph shown in the upper diagram of FIG. 1, according to the graph, the compressive strength at the time of demolding is required 10 kN / mm ^2, when the compressive strength of the 10 kN / mm ² is obtained The resistance value at is about 2.7 kΩ for ordinary Portland cement (N) and 55% cement concrete. Therefore, it is possible to set the time when the resistance value of the placed concrete during the curing of the actual structure becomes about 2.7 kΩ as the most appropriate timing for demolding. And by setting to perform demolding at such timing, it is possible to ensure the required durability and the demolition time of the cast concrete of the actual structure from the service life required at the design stage and the construction period It is possible to set in advance an appropriate time that does not cause any waste as a design item.

Next, the technique of the present invention of (4) is a method of estimating the life, which is the useful life (≈ rebar corrosion start time) of a concrete structure, which is an actual structure, at the time of demolding. ,
As in the configuration of (2) above, that is, as shown in FIGS. 9 to 11, the electrode 2 having a set of a plurality of electrodes arranged in parallel at a specific equal interval is positioned on the cover of the concrete 3 of the actual structure. The electrode 2 is disposed from the outside of the mold 1 so that at least a part of each electrode 2 is embedded in the portion to be embedded, and the concrete 3 is placed in the mold 1 and subjected to curing 6. The transition of the resistance value during hardening of the cover part of the concrete 3 is measured by energizing the measuring means 5 through the energizing means 4 connected to the electrode 2, and the resistance value at the time of demolding is recorded.
The recorded resistance value at the time of demolding is applied to the resistance value in the correlation result in the specimen of (1) above, and the compressive strength and / or medium correlated with the applied resistance value. Seeking sexual depth,
From this calculated compressive strength and / or neutralization depth value, the life of the concrete structure, which is an actual structure, is estimated to be the useful life (≈rebar corrosion start time).

  The result of the correlation in the specimen of (1) used in the technique of the present invention of (4) is the result of the correlation of the specimen that best matches the design conditions of the actual structure among the obtained specimens. Yes, the resistance value measured most during the curing of the concrete in which the actual structure is placed is fitted to the resistance value of the best match, and at least the compressive strength or the neutralization depth correlated with this resistance value. The lifetime is estimated from one of the values.

  According to the technique of the present invention of (4), the life which is the useful life (≈ rebar corrosion start time) of the concrete structure which is the actual structure is estimated from the data of the placing situation at the time of construction of the actual structure. can do. That is, the life of the cast concrete can be known at the stage of demolding.

Next, the technique of the present invention of (5) is a management method in which construction information relating to the curing of a concrete structure that has been constructed is recorded and stored as digitized data. As a specific configuration,
Based on the result of the correlation in the specimen of (1) above, the actual structure is constructed, and the resistance value measured during the construction is recorded and stored together with the construction conditions.

  According to the technique of the present invention of (5), the construction information can be managed by recording and storing information relating to the curing of the constructed concrete structure as digitized data.

  Further, in the technique of the present invention of (5), as shown in FIG. 12, the resistance value data measured during the construction together with the construction condition data, for example, a LAN system or the like is constructed, and the construction site is wirelessly or wired. It can also be set as the structure which can transmit to the place away from and can confirm the construction condition of a construction site in this away place.

  Further, in the technique of the present invention of (5), the management by recording and storing the construction information described above is not limited to one construction site, but the resistance value data measured during construction at a plurality of construction sites is It is also possible to construct a database in which a plurality of construction information is accumulated by recording and saving together with data. According to such a configuration, it is possible to refer to and confirm past records by accumulating construction information in the database, and it is efficient to improve and improve construction technology based on past records that have been referenced and confirmed. Can be used effectively.

  Furthermore, according to the technique of the present invention of (5), the deterioration of the concrete structure which is an actual structure after construction based on the resistance value data and construction condition data measured during the recorded / stored construction. It can also be set as the structure which performs progress prediction. According to such a configuration, it is possible to prepare in advance countermeasures such as repairs according to deterioration by predicting the progress of deterioration of the concrete structure after construction, so take appropriate and effective measures to prevent deterioration. Can do.

  In addition, when the deterioration of a concrete structure, which is an actual structure after construction, is discovered, the cause of deterioration is estimated based on resistance value data and construction condition data recorded and stored during construction. You can also According to such a configuration, when the constructed concrete structure is deteriorated, it is possible to perform appropriate repair / repair according to the deterioration by estimating the cause of the deterioration.

  Next, it is effective to use the technique of (6) according to the present invention, the quality determination method of (1) above, and the technique of (2) to (5) based on the result of correlation in the specimen of (1). The formwork for measuring the resistance value of the placed concrete, which is a simple formwork, will be described.

  This resistance value measuring form has the configuration shown in FIGS. 9 to 11 as a specific configuration example, and will be described in further detail below. In addition, description of a structure is abbreviate | omitted about the part already demonstrated in the said Example.

  The number of the electrodes 2 that make a plurality of sets is not limited to the set of four in the embodiment, but the number of electrodes other than four can be set as one set, such as a set of two. In view of the above points and the measurement accuracy, the set of four shown in the above embodiment is most preferable.

  The distance a between the electrodes 2 may be about several centimeters, and specifically, about 5 cm can be mentioned as a preferable example. Moreover, in order to avoid the influence of a reinforcing bar, it is preferable that the space | interval a of each electrode 2 is smaller than the distance from the electricity supply part 21 of each electrode 2 to a reinforcing bar.

  The electrode 2 is disposed on the mold 1 such that the current-carrying portion 21 protrudes into the mold 1 and that the current-carrying means 4 can be connected from the outside of the mold 1 so that the dam plate, the supporting work, etc. The electrode 2 may be attached and fixed to a mounting frame or the like separate from the mold 1 so that the current-carrying portion 21 protrudes into the mold 1 through the mold 1. It is good also as a structure which attaches and fixes to what the mold 1 is, and the support structure etc. which were arrange | positioned outside the mold 1 so that the electricity supply part 21 might protrude in the mold 1 through the mold 1 It can also be set as the structure which attaches and fixes the electrode 2 to.

  As shown in FIG. 9 (4), the electrode 2 is cut off the protruding portion from the placed concrete 3 after the curing 6 and the form 1 are removed. Or it can also be set as the aspect kept without excising in order to perform measurement after aged.

DESCRIPTION OF SYMBOLS 1 Formwork 2 Electrode 3 Cast concrete 4 Current supply means 5 Measuring means 6 Curing sheet 7 Specimen 8 Formwork of specimen

Claims (4)

It is a formwork for measuring the resistance of cast concrete,
A set of a plurality of electrodes arranged so as to be juxtaposed at specific equal intervals in a state of protruding into the mold so that at least one end is buried in the placed concrete;
Energization means connected to each electrode so as to be energized;
Measuring means for energizing each electrode through the energizing means, and measuring a current value flowing through each electrode and a potential difference between the plurality of electrodes;
Have
Of the portion embedded in the placed concrete, the electrode is in a configuration in which the energized portion with the placed concrete is in an exposed state, and the portion other than the energized portion is in an insulating covering state with an insulating member,
When the electrode is insulated with the insulating member, the position of the energization portion is appropriately changed in accordance with the set value of the energization depth by exposing the surface of the electrode for the portion corresponding to the desired energization depth. It is a configuration that can set the energization depth by
A formwork for measuring the resistance value of concrete placed. 2. The resistance measurement of the placed concrete according to claim 1, wherein the plurality of electrodes is a set of four electrodes arranged in parallel at a specific equal interval. Formwork. The set of the electrodes has a configuration in which a current-carrying portion with concrete placed in a position embedded in a cover depth in concrete placed from the inner surface of the mold is provided. Item 3. A form for measuring resistance value of concrete placed according to Item 1 or 2. The said electrode is a wire, The formwork for resistance value measurement of the placed concrete in any one of Claims 1-3 characterized by the above-mentioned.

Images