JP2001249123A - Method for evaluating water absorption characteristic of artificial lightweight aggregate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method allowing a great reduction in measuring time and accurate evaluation of the water absorption characteristic of artificial lightweight aggregate. SOLUTION: A sample of known mass before water absorption is put in a vacuum container and suction is carried out for at least two minutes at a degree of vacuum of 80 kPa or higher, after which water is injected until the sample is completely immersed therein. Thereafter, the inside of the container is immediately restored to atmospheric pressure and the sample with water absorbed therein is taken out; after water on the surface of the sample is wiped away to dry the surface, the mass of the sample is measured. The water absorption characteristic of the sample is evaluated on the basis of the difference between the mass of the sample when its surface is dry and the mass of the sample before it absorbs water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for easily evaluating the water absorption properties of artificial lightweight aggregates, and more particularly to a method for absorbing artificial lightweight aggregates immediately after they are manufactured at a site where artificial lightweight aggregates are manufactured. The present invention relates to a method for evaluating the water absorption properties of an artificial lightweight aggregate, which can be suitably used for easily evaluating the properties on the spot.

[0002]

2. Description of the Related Art In recent years, artificial lightweight aggregates have been actively developed due to the depletion of natural lightweight aggregate resources such as pumice, coral and diatomaceous earth. However, artificial lightweight aggregates generally have more open voids and tend to have higher water absorption rates than naturally occurring aggregates.

[0003] When pumping is performed on fresh concrete using artificial lightweight aggregate having many open cavities, the water content decreases, the viscosity of the fresh concrete increases, and there is a high risk of clogging in the pipe. this is,
This is because the air in the open space is compressed by the pressure at the time of pumping, and water enters. Even with artificial lightweight aggregates with many open voids, if artificial lightweight aggregates after sufficient water absorption are used, the open voids are filled with water, and the above-mentioned troubles occur even if pumping is performed. Absent. However, in this case, there is a problem that the freeze-thaw resistance of the cured body is reduced at a later date due to moisture absorbed by the artificial lightweight aggregate. Therefore, in any case, it is desired that the manufactured artificial lightweight aggregate be an aggregate having a small open space and a low water absorption.

[0004] Here, the measurement of the water absorption of the conventional artificial lightweight aggregate has been performed in accordance with JIS A 1135 "Test method for density and water absorption of lightweight structural coarse aggregate".

[0005] In the test method for water absorption specified in JIS A 1135, a washed sample is dried at 105 ± 5 ° C until a constant weight is reached. The dried sample is cooled to room temperature, and absorbed in still water at 20 ± 5 ° C. for 24 hours or more. After water absorption, the sample is rolled on a water-absorbing cloth to wipe off the visible water film on the surface to make the surface dry. Measure the mass (M1) of the sample in the surface dry state to 0.1 g. The sample is dried at 105 ± 5 ° C. until it has a constant mass, cooled to room temperature in a desiccator, and then cooled to a mass (M2).
Up to 0.1 g. Then, the water absorption is calculated by the following equation 1.

[0006]

(Equation 1)

[0007] It is.

[0008]

However, the amount of the open space of the above-mentioned artificial lightweight aggregate is greatly affected by subtle changes in manufacturing conditions and the like, and increases or decreases. In particular, it is necessary to manage the water absorption characteristics on site and to promptly take measures such as correction of manufacturing conditions. However, in the above-described water absorption rate test method specified in JIS,
Since it required a very long measurement time, such as absorption of water for 24 hours or more in still water and subsequent drying to a constant mass, the artificial lightweight aggregate produced at the manufacturing site of the artificial lightweight aggregate This method was not a method that could be used to quickly evaluate the water absorption properties of the product on the spot and to modify the manufacturing conditions. Therefore, there has been a strong demand for the development of a quick and accurate method for evaluating water absorption properties that can be used when on-site management of the quality of artificial lightweight aggregate during production.
In addition, even in the method of measuring the water absorption rate specified in JIS described above, even after the sample is actually absorbed for 24 hours,
Since the water absorption of the sample continued, it was only one guide when evaluating the water absorption characteristics of the sample.

SUMMARY OF THE INVENTION The present invention has been made in order to cope with the strong demands of the above-mentioned artificial lightweight aggregate manufacturing site, and an object of the present invention is to significantly reduce the measuring time and to further reduce the artificial lightweight aggregate. It is an object of the present invention to provide a method capable of accurately evaluating the water absorption characteristics of a liquid crystal.

[0010]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above-mentioned object. As a result, if a sample is absorbed under reduced pressure, it is required to comply with JIS regulations in a very short time. The present inventors have found that a sample can be made to absorb water up to a water absorption amount equal to or more than water absorption for more than an hour, and completed the present invention.

That is, according to the present invention, a sample having a known mass before water absorption is placed in a vacuum container, and the sample is sucked at a vacuum degree of 80 kPa or more for at least 2 minutes, and then water is injected until the sample is completely immersed. Is returned to the atmospheric pressure, the sample that has absorbed water is taken out, the surface water of the sample is wiped to make the surface dry, and then the mass of the sample is measured, and the mass of the sample in the surface dry state and the mass of the sample before water absorption are measured. From the difference, the water absorption characteristics of the sample were evaluated. The degree of vacuum indicates the degree of vacuum as a difference from the standard atmospheric pressure.
A complete vacuum is obtained at 1.3 kPa.

In the above-described method for evaluating the water absorption properties of the artificial lightweight aggregate according to the present invention, water is injected at atmospheric pressure after the air in the open space existing in the artificial lightweight aggregate is sufficiently eliminated. Therefore, water enters in a state where it is sucked into the open space of the artificial lightweight aggregate, and the open space that can enter under the atmospheric pressure is instantly filled with water. Therefore, it becomes possible in a very short time to absorb the artificial lightweight aggregate up to a water absorption equivalent to or more than 24 hours in still water specified by JIS in an extremely short time.
This is a method that can be used when on-site management of the water absorption properties of the artificial lightweight aggregate during manufacturing.

Here, in the present invention, the sample is placed in a vacuum vessel, and at least
The suction for at least 2 minutes was performed at a vacuum of 80 kPa or more for at least 2 minutes, so that air in the open space of the sample could be sufficiently eliminated, and the sample was subjected to 24 hours or more in still water specified by JIS. The artificial lightweight aggregate can be instantaneously absorbed to a water absorption equal to or greater than that of water absorption. Was found by the test.

Preferably, the sample is sucked at a vacuum degree of 90 kPa or more for about 5 minutes. This means that even if the degree of vacuum exceeds 90 kPa,
In addition, even if the suction time exceeds 5 minutes, the measured values of the subsequent samples do not change much as much as the difference, and in consideration of the power consumption and the shortening of the measurement time, such vacuum suction conditions are appropriate. Was found by the test.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the above-described method for evaluating the water absorption properties of the artificial lightweight aggregate according to the present invention will be described, but the present invention is not limited to such an embodiment. .

First, a sample whose water absorption is to be measured is placed in a drier and dried at 105 ± 5 ° C. until it has a constant mass. The dried sample is then cooled to room temperature and a known mass of about 50
A sample is placed in a 0 ml transparent container to about 80%, and the sample mass (Ws) is measured to 0.1 g.

Subsequently, the volume shown in FIG.
In a vacuum vessel (inner diameter 150 mm, height 200 mm)
The sample whose mass has been measured is placed in a transparent container, and the clamp is closed to close the vacuum container.
Then, the valve A is opened to the vacuum pump side, and the air in the vacuum container is sucked by operating the vacuum pump (evacuation capacity 50 l / min, ultimate vacuum degree of 99.9 kPa or more), and the vacuum degree is 90 kPa or more for about 5 minutes. Suction. Then, the valve B is opened, water is poured to the upper part of the sample, and then the valve B is closed and the valve A is operated to return the inside of the vacuum vessel to the atmospheric pressure. If the specific gravity of the measurement sample is smaller than 1, a part of the sample floats on the water surface, so it is necessary to take measures such as putting the sample in a net so that the sample does not float. is there.

Immediately thereafter, the clamp is removed, the sample is taken out of the transparent container, and water droplets on the sample surface are quickly wiped off with a damp cloth or the like, and the sample weight (W1) is measured to 0.1 g.

The water absorption (q) of the sample is calculated by the following equation (2).
Is calculated.

[0020]

(Equation 2)

With the above operation, the water absorption of the sample is measured. Note that the measurement of the water absorption rate was performed when the sample volume was 200
In the case of about ml, it can be completed in about 7 minutes.

[0022]

Test Examples Hereinafter, test examples in which a method for evaluating the water absorption characteristics of the artificial lightweight aggregate according to the present invention described above will be described.

-Artificial lightweight aggregate sample used for test-Sample A: particle size range: 10 mm to 15 mm, density: 0.58 kg / l water absorption; 5.4% Sample B: particle size range: 10 mm to 15 mm Density: 0.60 kg / l Water absorption: 3.2% Sample C particle size range: 10 mm to 15 mm, density: 0.59 kg / l Water absorption: 1.9% Sample D: Particle size range: 10 mm to 15 mm, density 0.62 kg / l water absorption; 6.8% Sample E: particle size range; 10 mm to 15 mm, density; 0.68 kg / l water absorption; 2.7% Sample F: particle size range: 10 mm to 15 mm, density 0.67 kg / l water absorption; 1.6% ・ Sample G: particle size range; 10 mm to 15 mm, density; 0.70 kg / l water absorption; 1.1% ・ Sample H particle size range: 10 mm to 15 mm, density; 0.59 kg l water absorption; 3.4% Sample I: particle size range; 10 mm to 15 mm, density: 0.56 kg / l water absorption; 3.9% The density and the water absorption of the sample, JIS A 11
It is a value of the density and the water absorption of each sample when performed based on 35 "Density and water absorption test method of structural lightweight coarse aggregate".

-Relationship Between Degree of Vacuum and Water Absorption Rate- For each of Samples A, B and C from which about 100 g were arbitrarily extracted, the capacity of the vacuum pump described in the above embodiment was variously changed, and the degree of vacuum was changed. Only 40kP
a, 60 kPa, 70 kPa, 75 kPa, 80 kP
a, 90 kPa and 99 kPa (sample B,
In C, there was a degree of vacuum that was not performed. ), When the suction time was 5 minutes and the underwater curing time was 1 minute, the water absorption calculated by Equation 2 shown in the above embodiment was measured. The results are shown in FIGS. 2 (a), (b) and (c). Since the change in the degree of vacuum is considered to greatly affect the initial water absorption of the sample, that is, the water absorption immediately after injecting water, the water is poured to the upper part of the sample, and then valve B is closed and valve A is operated. Then, the inside of the vacuum container was returned to the atmospheric pressure, and the clamp was immediately removed to take out the sample from the transparent container. However, it took about 1 minute until the sample was taken out. And In addition, the reason why the suction time is set to 5 minutes is that the purpose of the present invention is to provide a method for quickly evaluating the water absorption characteristics, and therefore, it is desired to obtain an effect with such a suction time.

From FIG. 2, it can be seen that the relationship between the degree of vacuum and the water absorption is linear, and that the degree of vacuum in the vacuum container is about 80% or more of the vacuum condition of 99 kPa if the degree of vacuum is 80 kPa or more. In other words, when the water absorption property of the artificial lightweight aggregate at the time of manufacturing is used for on-site management or the like, if the degree of vacuum is set to 80 kPa or more, it is found that there is no error as much as the difference and no inconvenience occurs.

-Relationship Between Suction Time and Water Absorption Rate- For each of Samples A, B and C from which about 100 g were arbitrarily extracted, the degree of vacuum shown in the above embodiment was set to 99 kPa, and only the suction time was set to 1 kPa. Minutes, 2 minutes, 5
, 10 minutes, and 30 minutes, and when the underwater curing time is 1 minute, the expression 2 shown in the above embodiment is used.
Was calculated. The result is shown in FIG. The underwater curing time is set to 1 for the same reason as described above.
Minutes.

From FIG. 3, the suction time may be about 2 minutes.
Further, it was found that even if the suction time exceeded 5 minutes, the measured values thereafter did not change as much as the difference.

-Relationship between Underwater Curing Time and Water Absorption Rate- For each of Samples D, E and F obtained by arbitrarily extracting about 100 g, the degree of vacuum shown in the above embodiment is 99 kPa and the suction time is 5 minutes. When only the underwater curing time was changed to 1 minute, 5 minutes, 10 minutes, and 30 minutes, the water absorption calculated by Expression 2 shown in the above embodiment was measured. FIG. 4 shows the results. The underwater curing time is at least 1 minute for the above reasons, and the underwater curing time is 5 minutes when the sample is allowed to stand still in the container for 4 minutes after injecting water, and then the sample is removed from the container. is there.

From FIG. 4, it can be seen that the water absorption of the sample increases as the curing time in water becomes longer. Even so, it was found that there was still a considerable space through which water could enter. This is thought to be due to the surface tension between the void interface and water, the capillary pressure, or the physicochemical phenomenon of the gas adsorbed and remaining in the voids. Pressing in proved impossible. However, similarly from FIG. 4, when the sample was taken out immediately after the water was injected, that is, when the underwater curing time was 1 minute, the value of the water absorption was far higher than the value of the water absorption according to JIS. If the sample is absorbed under a predetermined reduced pressure, the JIS
It is possible to absorb the sample up to the water absorption equal to or more than the water absorption for 24 hours or more specified in
The degree of voids where water can easily enter is determined according to JIS 24
Because it is considered to show better than water absorption over time, when used to evaluate the water absorption properties of artificial lightweight aggregates,
It was found that even if the sample was taken out immediately after water was injected under reduced pressure, no inconvenience occurred in the evaluation.

-Relationship Between Sample Amount and Suction Time- For each of the samples G, H, and I from which about 100 g and about 400 g were arbitrarily extracted, the degree of vacuum shown in the above embodiment was set to 99 kPa, and suction was performed. When only the time was changed to 5 minutes, 10 minutes, and 30 minutes, and when the underwater curing time was 1 minute, the water absorption calculated by Equation 2 shown in the above embodiment was measured. The results are shown in FIGS. 5 (a), 5 (b) and 5 (c).

FIG. 5 shows that it is not necessary to increase the vacuum suction time even when the sample amount increases.

From the above test results, regardless of the size of the sample, if the sample is sucked at a vacuum degree of 80 kPa or more for at least 2 minutes, the air in the open space of the sample can be sufficiently eliminated, and it is specified in JIS. It has been found that the sample can be instantaneously absorbed to a water absorption amount equal to or greater than the water absorption for 24 hours or more in still water. Further, it was found that even if the vacuum suction condition of the sample was a degree of vacuum exceeding 90 kPa or a suction time exceeding 5 minutes, the measured values of the sample thereafter did not change as much as the difference.

-Reliability test of the method for evaluating water absorption properties according to the present invention-Water absorption (JIS water absorption) when performed in accordance with JIS
The water absorption (the water absorption of the present invention) was measured for a large number of samples for which the values were known by the methods described in the above embodiments. FIG. 6 shows the result.

FIG. 6 shows that the water absorption of the present invention and the JIS water absorption show a strong correlation with artificial lightweight aggregate samples having various water absorption characteristics (water absorption). The evaluation method was found to be a method capable of evaluating the water absorption characteristics of the artificial lightweight aggregate with approximately the same accuracy as the method of measuring the water absorption specified in JIS. In addition, from this figure, the JIS water absorption can be estimated from the water absorption of the present invention, so that the method for evaluating the water absorption characteristics according to the present invention can be one of the simple measurement methods for obtaining the JIS water absorption. It turned out to be.

[0035]

As described above, the method for evaluating the water absorbing property of the artificial lightweight aggregate according to the present invention described above is capable of evaluating the water absorbing property of the artificial lightweight aggregate in a very short time with high accuracy. At the manufacturing site of artificial lightweight aggregate, the water absorption characteristics of the manufactured artificial lightweight aggregate can be quickly evaluated on the spot, and it can be used to modify the manufacturing conditions. Therefore, the economical effect is very large because it is possible to prevent the manufacture of the product.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a measuring device used in a method for evaluating the water absorption characteristics of an artificial lightweight aggregate according to the present invention.

FIG. 2 is a diagram showing the relationship between the degree of vacuum and the water absorption,
(A) is about sample A, (b) is about sample B,
(C) is a diagram showing each of the samples C.

FIG. 3 is a diagram showing the relationship between the suction time and the water absorption for each of Sample A, Sample B, and Sample C.

FIG. 4 is a diagram showing the relationship between the curing time in water and the water absorption for each of Sample D, Sample E, and Sample F.

FIG. 5 is a diagram showing a relationship between a sample amount and a suction time;
(A) is for sample G, (b) is for sample H,
(C) is a diagram showing each of the samples I.

FIG. 6 is a diagram showing the relationship between the water absorption of the present invention and JIS water absorption.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuo Izawa 1-2-23 Kiyosumi, Koto-ku, Tokyo Within Pacific Research Center Co., Ltd. (72) Inventor Akiko Umeki 1-2-23 Kiyosumi, Koto-ku, Tokyo Pacific Inside Research Center, Cement Corporation (72) Haruka Takahashi 1-2-23 Kiyosumi, Koto-ku, Tokyo Inside Pacific Research Center (72) Yasufumi Terumitsu 1-2-23, Kiyosumi, Koto-ku, Tokyo Pacific Cement Co., Ltd. Research Division

Claims (1)

[Claims] 1. A sample having a known mass before water absorption is placed in a vacuum container, aspirated at a degree of vacuum of 80 kPa or more for at least 2 minutes, water is injected until the sample is completely immersed, and then the container is immediately brought to atmospheric pressure. Remove the sample that has returned and absorbed water, wipe the surface water of the sample to make it dry, and measure the weight of the sample.From the difference between the weight of the sample in this dry state and the weight of the sample before water absorption, A method for evaluating the water absorption properties of an artificial lightweight aggregate, characterized by evaluating the water absorption properties of the artificial lightweight aggregate.