JP2015055574A - Method for analyzing deterioration state of cement hardened body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for analyzing a deterioration state of a cement hardened body capable of easily analyzing a deterioration state of a cement hardened body.SOLUTION: The method includes a water supply step for supplying a cement hardened body with water until the cement hardened body becomes a wet state, a dry step for drying the cement hardened body in the wet state for a predetermined period of time, a measurement step for measuring a moisture content at a plurality of points inside the dried cement hardened body, and a determination step for determining a deterioration state of the cement hardened body by comparing the moisture content at a plurality of points inside the measured cement hardened body.

Description

  The present invention relates to an analysis method for analyzing a deteriorated state of a hardened cement body.

  A hardened cement body such as a concrete structure may deteriorate due to, for example, a fine crack inside when a long period of time elapses after construction. The deterioration state inside the hardened cement body is analyzed, for example, by cutting out a part of the hardened cement body as a test piece and measuring physical properties such as compressive strength of the test piece. ing.

For example, in Non-Patent Documents 1 and 2, a comparatively small cylindrical test piece (small-diameter core) having a diameter of about 20 mm to 25 mm is taken from a hardened cement body, and the compressive strength of the core is measured. It describes that the degradation state is analyzed. In such an analysis method using a small-diameter core, for example, damage to the hardened cement body is less than when a relatively large core having a diameter of 100 mm or more is used, and repair work of the hardened cement body can be easily performed after sampling. .
However, in the method of analyzing the deterioration state from the compressive strength, it is necessary to measure the compressive strength of the test piece in a test room or the like after cutting the test piece, which takes time and labor for the analysis.

Alternatively, as a method for non-destructive analysis of a hardened cement body, a rebound hardness method, a method for measuring surface temperature by thermography, a method using elastic waves such as ultrasonic waves, impact elastic waves, percussion sounds, acoustic emission (AE) Laws can be considered.
However, any of these non-destructive methods of analyzing the deterioration state requires measurement and analysis by a skilled engineer using a special apparatus, and it is difficult to easily analyze the deterioration state.

"Estimation of compressive strength of concrete structures with small-diameter cores" Fumonori Sato et al. September 2003 The 58th Annual Conference of the Japan Society of Civil Engineers "Fundamental study on compressive strength estimation of concrete structures by drilling test" Chikako Kondo et al. Proceedings of Japan Earthquake Engineering Society Vol.8 No.1 2008

  In view of the above problems, an object of the present invention is to provide a method for analyzing a deterioration state of a hardened cement body, which can easily analyze the deterioration state of the hardened cement body.

The degradation state analysis method of the hardened cement body of the present invention is as follows.
A water supply process for supplying water until the hardened cement body is wet;
A drying step of drying the hardened cement cured body for a predetermined time;
A measuring step for measuring the amount of water in a plurality of locations inside the dried cement cured body,
And a determination step of determining the deterioration state of the cement hardened body by comparing the moisture content inside the hardened cement body at a plurality of measured locations.

In the deterioration analysis method of the hardened cement body according to the present invention, there was a portion where cracks occurred inside the hardened cement body by performing a water supply process for supplying water until the hardened cement body was wet. In some cases, water can be retained within the crack. Next, by carrying out a drying process for drying the cement hardened body in a wet state for a predetermined time, the cement hardened body is dried, causing a difference in water content between the cracked hardened body and the other parts of the cement hardened body. be able to.
Furthermore, by carrying out a measurement step of measuring the moisture content at a plurality of locations inside the dried cement cured body, and further comparing the moisture content inside the cement cured body at the measured multiple locations, Due to the difference in water content, it is possible to analyze the deterioration state of the hardened cement body when the portion with a high water content is a portion where cracks are progressing more than the portion with a small amount of water, that is, where deterioration is progressing.

  In the present invention, the predetermined time in the drying step may be not less than 0.1 hours and not more than 26 hours.

  By drying for the predetermined time, the deterioration state can be analyzed more accurately.

  According to the present invention, it is possible to easily analyze the deterioration state of a hardened cement body.

The graph which shows the difference in moisture content. The graph which shows the difference in moisture content. The graph which shows the difference in moisture content. The graph which shows the relationship between the ratio with respect to the moisture content of a healthy part, and compressive strength.

Hereinafter, an example of the analysis method of the deterioration state of the hardened cement body according to the present invention will be described.
The analysis method of the present embodiment includes a water supply process for supplying water until the cement hardened body is wet, a drying process for drying the wet cement hardened body for a predetermined time, and the inside of the dried cement hardened body The measurement process which measures the moisture content in multiple places of this, and the determination process which determines the deterioration state of a cement cured body by comparing the moisture content inside the cement cured body in the measured multiple places.

(Hardened cement)
The cement cured body to be analyzed in the present embodiment is not particularly limited as long as it is a cement cured body such as concrete or mortar. Examples thereof include concrete parts such as roads, bridges, tunnels, buildings, and mortar parts.
In particular, the concrete floor slabs of roads and bridges may deteriorate due to cracks inside due to alkali silica reaction, freezing, salt damage, etc. in addition to fatigue damage due to vehicle running, but this deterioration is analyzed. If you stop using it for a long time, traffic will be hindered. Therefore, the analysis method of the present embodiment that can easily analyze the deterioration state after a short period of stoppage of use is suitable.

(Water supply process)
The analysis method of this embodiment includes a water supply step of supplying water until the hardened cement body is wet.
In this embodiment, the “wet state” means that the cement cured body contains water to such an extent that the surface of the cement cured body can be visually observed to be discolored.
For example, when the hardened cement body is concrete, the wet state can be obtained by supplying about 1 to 3 liters of water per 1 m ^{2 of the} hardened cement body area.

(Drying process)
The analysis method of the present embodiment includes a drying step of drying the hardened cement cured body for a predetermined time.

In the drying step, the moisture content can be changed inside the hardened cement body by drying the wet hardened cement body for a predetermined time.
That is, in the vicinity of a crack inside the hardened cement body, when water is sufficiently supplied, the water is retained in the crack, and then the water in the hardened cement body is reduced by performing a drying process. Since there is more water in the crack than in other parts, it takes time to completely disappear.
Therefore, once a sufficient amount of water is present in the crack and then dried to some extent, the hardened cement body around the crack will be supplied with water from the crack for a long time. The amount of water increases compared to the location where it does not occur.

In the drying process of the present embodiment, the predetermined time for drying the hardened cement body means a time during which the hardened cement body can be dried to such an extent that the water in the cracks is not completely dried.
The predetermined time is, for example, about 0.1 hour to 26 hours, preferably about 1 hour to 25 hours, and more preferably about 23 hours to 25 hours.
By drying the cement hardened body for the predetermined time, it is possible to reliably change the amount of water between the cracked vicinity of the cement hardened body and other places, and the deterioration state can be analyzed accurately.

  In the drying step of the present embodiment, the conditions for drying the hardened cement body are normal ambient temperature, for example, 15 ° C. to 30 ° C., and normal ambient humidity, for example, relative humidity of about 40% to 70%. It is preferable to dry. In addition, when the cement hardened body is an outdoor structure such as a road or a bridge, it is preferably dried in a state where rainwater is not directly applied to a location to be measured.

(Measurement process)
The analysis method of the present embodiment includes a measurement step of measuring the moisture content at a plurality of locations inside the dried cement hardened body.

In the present embodiment, as a method for measuring the moisture content at a plurality of locations inside the hardened cement body, for example, holes are formed at a plurality of locations on the surface of the dried cement hardened body, and the moisture content of the cement hardened body at the holes. The method etc. which measure are mentioned.
The diameter of the hole is not particularly limited as long as the hole has a diameter that allows the moisture content inside the hardened cement body to be measured. For example, when the moisture content during cement hardening is measured with an electric resistance moisture meter or the like as will be described later, a hole having a diameter that can be inserted into a sensor portion or the like of these devices, for example, a hole having a diameter of about 6 mm. Is preferably formed.

The depth of the hole is, for example, a depth of about 0.35 or more of the thickness of the cement cured body from the surface of the cement cured body (when the thickness of the cement cured body is 200 mm, a depth of 70 mm or more from the surface), Preferably, the depth is about 0.45 or more (when the thickness of the hardened cement body is 200 mm, the depth is 90 mm or more from the surface).
By forming a hole having such a depth and measuring the moisture content inside the hardened cement body at the depth, the presence or absence of cracks and the degree of cracking can be analyzed with high accuracy.

  The method for forming the hole is not particularly limited, and for example, a known drilling means such as a drill or a commercially available electric concrete drill can be used.

The location where the hole is formed is not particularly limited as long as it is a plurality of locations of 2 or more, and can be appropriately set according to the confirmation of the area of the member to be measured and the degree of deterioration visually, for example, It is preferable that a location where holes are formed at one or more locations per 10 m ² of the surface of the hardened cement body is set.
By forming a hole in the above-mentioned location and measuring the moisture content of the hardened cement body in the hole, it is possible to accurately analyze whether or not there is a crack.

  In the measurement process to be described later, when the moisture content is measured using an electric resistance moisture meter, two holes are measured at intervals of about 30 mm per measurement in order to measure the electrical resistance between the two electrodes. It is necessary to form with. Therefore, the number of holes in this case is twice the number of measurement points.

Any location of the hardened cement body can be selected as the position where the hole is formed. For example, it may be a position having a uniform interval on the surface of the hardened cement body, and a hole may be formed in a place where the degree of deterioration is expected to be different from the installation state of the hardened cement body.
In this case, for example, it is preferable to select a portion that is predicted not to be clearly degraded and a portion other than that.
By comparing such a reference with the moisture content at a plurality of locations on the basis of the moisture content at a location that is not clearly degraded, the degree of degradation can be analyzed with higher accuracy.

Next, the moisture content inside the hardened cement body at the depth of the hole is measured.
The method for measuring the water content of the hardened cement body is not particularly limited, and a known method for measuring the water content of the hardened cement body can be employed. For example, a method of using a device that can measure the moisture content of the cement cured body in the vicinity of the contact point by bringing a sensor into contact with the inner wall or bottom surface of the hole of the cement cured body, such as an electrical resistance moisture meter, etc. .
Thus, when the amount of moisture is measured using a device capable of measuring moisture by contacting a sensor or the like, it is preferable because it can be easily measured without requiring a special device or skill. Also, when a sensor such as a needle sensor or a brush sensor is used as the sensor, the diameter of the hole can be set to a diameter that allows the sensor to be inserted, and it is not necessary to cut the hardened cement body greatly, which is preferable.

When measuring the moisture content in the hardened cement body, the hole is formed to a certain depth, and after measuring the moisture content of the hardened cement body at that depth, the depth of the hole is further increased, You may measure the moisture content of the cement hardening body of depth. In this case, in the same hole, the amount of water inside the hardened cement body at different depths is measured.
In such a case, since the moisture content of the hardened cement body at each depth position can be compared in the determination step described later, the deterioration state can be analyzed more accurately.

Moreover, when measuring the water content of several places on the surface of the cement hardening body dried in the said drying process, it is preferable that the measurement of the water content of each place is performed as simultaneously as possible.
If the time for measuring the amount of water at each location varies, the amount of water in the hardened cement body will change even after the drying process is completed, and therefore there is a possibility that the amount of water cannot be measured accurately. Therefore, it is preferable to measure a plurality of locations in a short time from the end of the drying process as much as possible.

(Judgment process)
The analysis method of this embodiment includes a determination step of determining the deterioration state of the cement hardened body by comparing the moisture content inside the cement hardened body measured at a plurality of locations.
The amount of water measured in the measurement step shows the following tendency.
If there is a crack inside the hardened cement body, water will enter the crack when sufficient moisture is supplied to the hardened cement body. Normally, when water is present in the hardened cementitious body, water is present in the fine voids of the hardened cementitious body, but the voids due to cracks have a larger volume than these fine voids, that is, there are many in the cracks. Of water will exist together.
When the hardened cement body is dried for the predetermined time in such a state, the moisture inside the hardened cement body evaporates and the amount of water in the hardened cement body decreases, but the water in the crack is completely removed. Until it is dried, water is supplied to the hardened cement body around the crack from the inside of the crack, so that the moisture content is higher than that of other portions.
In other words, if a sufficient amount of water is supplied to penetrate the hardened cement to the inside, and then the drying is stopped after a certain amount of time, the water content of the hardened cement near the crack will be More than

Also, even in places where cracks are present, in places where there are many cracks or where deterioration is progressing such as where there are large cracks, the amount of water present in the cracks increases, The amount of water after the drying process is larger than that of a portion having few cracks or a portion having small cracks, and a state where the amount of moisture is large for a long time is maintained.
Therefore, by comparing the water content of the hardened cement body after the drying process, the size and degree of cracks can be analyzed from the difference in water content.

  In the analysis method of the present embodiment, when the determination step is performed, the relationship between the presence / absence, number, size, and moisture content of cracks may be measured in advance, and the determination may be performed based on the measurement result. .

In the determination step of the present embodiment, the criterion for determining the deterioration state of the hardened cement body can be appropriately set. For example, the deterioration state may be determined based on the following criteria.
Comparing the moisture content inside the hardened cement body at a plurality of locations measured in the measurement process, a reference value of 130% to 320% is determined with respect to the moisture content at the location with the lowest moisture content, and the moisture above the reference value A portion that is a quantity may be determined to be deteriorated.
As the reference value, for example, a reference value that can accurately measure the deterioration state using a sample or the like may be set in advance.

  In addition, although the deterioration state analysis method of the cement hardened body concerning this embodiment is as above, it should be thought that embodiment disclosed this time is an illustration and restrictive at all points. is there. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples of the method for analyzing a deterioration state of a cement cured body according to the present invention. However, the present invention is not limited to the following examples.

  Sponge mats were laid on the surface of a concrete floor slab (thickness 200 mm, length 900 mm, width 900 mm) prepared with the composition shown in Table 1, and water was applied up to about 2 liters. .

Then, direct sunlight and rainwater were shielded by a waterproof sheet above the concrete floor slab and allowed to dry naturally for 24 hours.
During drying, the temperature and relative humidity were measured every hour. The average temperature was 25 ° C. and the average relative humidity was 65%.
After drying, 10 locations on the surface of the concrete slab were randomly selected.
Two holes with a diameter of 6 mm and a depth of 100 mm are formed in adjacent positions for each part by dry drilling, and after the shavings are cleaned with a vacuum cleaner, the moisture content is measured immediately using the electric resistance moisture meter. did.
After measuring the moisture content, a cylindrical core having a diameter of about 100 mm and a height of about 200 mm was collected at a position 50 mm away from each hole, and the compressive strength was measured using the core according to JIS A1127.
The results are shown in Table 2.

  As shown in Table 2, it can be seen that the portions 9 and 10 have considerably less water content at any depth than the portions 1 to 8. That is, it can be judged that the parts 9 and 10 are healthy parts (healthy parts) with less or no cracks than the other parts, and the other parts are relatively cracked more than the healthy parts. It can be judged that it is a degraded part (degraded part).

Comparing the value of the compressive strength of each part and the amount of water to support the analysis result based on the amount of water, it is clear that the parts 9 and 10 have higher compressive strength than the parts 1 to 8.
That is, it is clear that the deterioration state of concrete can be analyzed with high accuracy by comparing the amount of water.

The relationship between the moisture content of the healthy part and the deteriorated part analyzed by the method described above is shown in FIGS.
As shown in FIGS. 1 to 3, it can be seen that the moisture content of the healthy part is significantly smaller than the moisture content of the deteriorated part at any depth.

In addition, the ratio of the moisture content of each deteriorated portion at a depth of 70 mm and 90 mm to the moisture content of the healthy portion (average of two locations) and the ratio of the compressive strength of each deteriorated portion to the compressive strength of the healthy portion (average of two locations). FIG. 4 is a graph showing the relationship between the
Moreover, the line which shows the design reference | standard intensity | strength (24 N / mm < ² >) of the said concrete was each shown with the dotted line.

As shown in FIG. 4 (a), at a depth of 70 mm, the compressive strength is lower than the design reference strength in the deteriorated portion having a moisture amount 1.4 times the moisture amount in the healthy portion.
Further, as shown in FIG. 4B, at a depth of 90 mm, the compressive strength is lower than the design reference strength in the deteriorated portion having a water content of 1.25 times the water content of the healthy portion.
That is, it can be seen that the ratio of the moisture content to the moisture content of the healthy part has a correlation with the compressive strength.
From this, a concrete specimen was prepared in advance with the same composition as the concrete to be analyzed, and the relationship between the compressive strength and the moisture content was obtained with the concrete specimen, and the graph shown in FIG. If it is prepared every time, the moisture content of the sound part of the concrete to be analyzed is measured, and the moisture content in each part of the concrete is calculated to calculate the ratio of the moisture content of the sound part. However, it can be easily analyzed whether it is a deteriorated part below the design standard strength of the concrete.

(Experiment 2)
The distribution of the moisture content in the concrete in the depth direction was measured by two types of moisture content measurement methods.
Concrete floor slabs (thickness 200 mm, length 900 mm, width 900 mm) were prepared with the formulation shown in Table 3 and exposed outdoors for 3 years. A sponge mat was laid on the surface of the concrete slab, and water was poured up to about 2 liters, and further covered with a blue sheet to be in a wet state for 24 hours or more. Then, direct sunlight and rainwater were shielded by a waterproof sheet above the concrete floor slab and allowed to dry naturally for 24 hours.

<Measurement of water content by core weight>
A small core having a length (concrete depth direction) of about 100 mm was collected from the concrete floor slab by a core machine equipped with a core bit having an outer diameter of 32 mm and an inner diameter of 25.6 mm. The small-diameter core was dry-cut in 20 mm increments in the length direction, and immediately after cutting, the weight was measured with a non-automatic scale (weighing 100 g, scale 0.02 g) as a specific measuring instrument to obtain a wet weight. Then, it was dried to a constant weight with a constant temperature dryer at 105 ° C., and the weight was measured to obtain a dry weight. The value obtained by subtracting the dry weight from the wet weight and dividing by the dry weight was defined as the amount of water by the weight of the core.

<Measurement of moisture content in the hole>
Two holes with a diameter of 6 mm are formed at intervals of 30 mm using a commercially available electric concrete drill on the surface adjacent to the location where the core of the concrete floor slab is collected, and each hole has a depth of 12.5 mm to 10 mm. The water content was measured at the position of the depth of the part. The moisture meter was an electric resistance moisture meter (device name: HI-800, manufactured by Kett Science Laboratory Co., Ltd.), and a sensor was inserted into each of the two holes to measure the moisture content.
The results are shown in Table 4.

  As shown in Table 4, almost the same results were obtained in any of the moisture content measurement methods. However, the amount of moisture by the weight of the core is considered to be that the evaporation of the outermost surface is progressing in the portion of 0 to 20 mm including the outermost surface, and the amount of moisture in the core is not uniform. It is considered that there was a difference from the results obtained with the electric resistance moisture meter.

(Experiment 3)
The same concrete slab used in Experiment 2 was exposed outdoors for 3 and a half years. A sponge mat was laid on the surface of the concrete slab, and water was poured up to about 2 liters, and further covered with a blue sheet to be in a wet state for 24 hours or more. Then, direct sunlight and rainwater were shielded by a waterproof sheet above the concrete floor slab and allowed to dry naturally for 24 hours.
After such pretreatment, the diameter of 6 mm and the depth of 100 mm are adjacent to each other at an interval of about 30 mm at four locations on the surface of the concrete floor slab (four positions separated by 300 mm in the vertical and horizontal directions from the center point). Two holes were formed, and the water content was measured at each depth position shown in Table 4 using the same electrical resistance moisture meter used in Experiment 1.
The four holes were measured immediately after drilling, after 1 hour, after 3 hours, and after 17 hours.
In the case where the moisture content was not measured immediately after drilling, the hole was closed with a cork stopper, and the stopper was removed immediately before the measurement.
The results are shown in Table 5.

  As shown in Table 5, it can be seen that when the time has elapsed since the hole was formed, the amount of water changes even if the stopper is plugged.

Claims (2)

A water supply process for supplying water until the hardened cement body is wet;
A drying step of drying the hardened cement cured body for a predetermined time;
A measuring step for measuring the amount of water in a plurality of locations inside the dried cement cured body,
A deterioration state analysis method for a hardened cement body, comprising: a determination step for determining a deterioration state of the hardened cement body by comparing the moisture content inside the hardened cement body at a plurality of measured locations.   The method for analyzing a deterioration state of a hardened cement body according to claim 1, wherein the predetermined time in the drying step is 0.1 hour or more and 26 hours or less.

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