KR101741137B1 - Test Method of Self-healing in Concrete Paste - Google Patents
Test Method of Self-healing in Concrete Paste Download PDFInfo
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- KR101741137B1 KR101741137B1 KR1020160027187A KR20160027187A KR101741137B1 KR 101741137 B1 KR101741137 B1 KR 101741137B1 KR 1020160027187 A KR1020160027187 A KR 1020160027187A KR 20160027187 A KR20160027187 A KR 20160027187A KR 101741137 B1 KR101741137 B1 KR 101741137B1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N5/00—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid
- G01N5/02—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid by absorbing or adsorbing components of a material and determining change of weight of the adsorbent, e.g. determining moisture content
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
- C04B40/06—Inhibiting the setting, e.g. mortars of the deferred action type containing water in breakable containers ; Inhibiting the action of active ingredients
- C04B40/0675—Mortars activated by rain, percolating or sucked-up water; Self-healing mortars or concrete
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/286—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q involving mechanical work, e.g. chopping, disintegrating, compacting, homogenising
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Abstract
In the present invention, a first step of forming a single crack in the cement paste; A second step of measuring an absorption rate of a cement paste having a single crack; And a third step of evaluating self-healing performance using the measured change in absorption rate; The present invention also provides a method for evaluating the self-healing performance of a cement paste including the cement paste. The evaluation method according to the present invention evaluates the self-healing performance of the cement paste from the change in absorption rate with time proportional to the crack area. Therefore, the self-healing performance of the cement paste can be more accurately evaluated as a whole without being disturbed by partial crack-filling.
Description
The present invention relates to a method of evaluating the self-healing performance of a cement paste, more particularly, to a method of evaluating the self-healing performance of a cement paste from a change in water absorption rate with time proportional to a crack area, And more particularly to a method of evaluating the self-healing performance of a cement paste which can evaluate the self-healing performance of the cement paste as a whole without being disturbed.
The cement paste has self-healing properties in which water penetrates into the microcracks due to the unreacted reactant present therein, and the cracks are compensated by the hydration reaction of the unreacted reactant. The self-healing property of cement paste depends on the type and composition ratio of cement, SCM, water, swelling agent, gypsum, etc. constituting it. The self-healing properties of these pastes are also affected by the surrounding environment (relative humidity, temperature) and are also affected by age. The self-healing properties of cement pastes have been studied only a few years ago and most of them use water flow test as a method to evaluate self-healing performance. The shake test is an experimental method to measure the change of the water flow with time after generating the water flow in the concrete / mortar specimen in which the crack exists. As the experiment progresses, the self-healing hydrate is generated in the crack and the water flow decreases (Fig. 1 (a)).
Water flow testing is the most widely used test method, but it does not accurately reflect crack-filling due to self-healing in cracks. In a water flow test, the water flow is greatly reduced if only one portion of the total crack is filled with self-healing hydrate (FIG. 1B). Therefore, it is difficult to accurately evaluate the self-healing performance of the entire crack. In addition, it is difficult to generate cracks of a certain size, which makes it difficult to compare the water streams between the blends.
Many experts predict that it will be necessary to review the self-healing performance of the concrete structure to improve the durability of the concrete structure, as the life expectancy of the concrete structure increases and the importance of maintenance is increasing. Also, in developed countries such as Japan and Netherlands, a concrete product maximizing self-healing performance is manufactured and applied to actual structures, and a test method for evaluating performance of self-healing is needed. However, it is difficult to evaluate the self-healing performance by using only the water flow test. In order to evaluate the quality of the self-healing concrete product, a new experimental method that can accurately evaluate the self-healing performance is needed.
It is an object of the present invention to provide a method for evaluating the self-healing performance of a new cement paste which can accurately evaluate the self-healing performance in order to evaluate the quality of the self-healing concrete product.
According to an aspect of the present invention, there is provided a cement paste comprising: a first step of forming a single crack in a cement paste; A second step of measuring an absorption rate of a cement paste having a single crack; And a third step of evaluating self-healing performance using the measured change in absorption rate; The present invention also provides a method for evaluating the self-healing performance of a cement paste including the cement paste.
The single crack may be a crack formed by performing three-point loading after notch formation.
The single crack may be an artificial crack generated by attaching two cement pastes.
And the step of waterproofing the region other than the single crack after the first step.
The evaluation method according to the present invention evaluates the self-healing performance of the cement paste from the change in absorption rate with time proportional to the crack area. Therefore, the self-healing performance of the cement paste can be more accurately evaluated as a whole without being disturbed by partial crack-filling.
1 is a schematic diagram illustrating a conventional water flow test method.
Fig. 2 is a schematic view of a method for forming a single crack by performing three-point loading.
3 is a schematic diagram illustrating a method of generating a single crack through paste specimen attachment.
Fig. 4 is a schematic diagram for explaining the difference in the water absorption rate between the case where cracks exist in the specimen and the case where there is no crack.
Fig. 5 is a schematic view for explaining a phenomenon in which the absorption area decreases due to self-healing after moisture absorption in the presence of cracks in the specimen.
6 is a graph for explaining the change of the initial absorption rate and the secondary absorption rate.
Fig. 7 is a schematic diagram for explaining a method of performing absorption rate measurement on a specimen in which cracks exist. Fig.
Fig. 8 is a schematic view for explaining a water-absorbable area in a specimen in which cracks exist. Fig.
FIG. 9 is a graph summarizing the water absorption test results of the embodiment of the present invention.
According to the present invention, there is provided a cement paste comprising: a first step of forming a single crack in a cement paste; A second step of measuring an absorption rate of the cement paste in which a single crack is generated; And a third step of evaluating the self-healing performance by using the change in the measured absorption rate. The present invention also provides a method for evaluating the self-healing performance of a cement paste.
In the first step of the method of the present invention, a single cracked cement paste is prepared.
In the case of general bending test, it is very difficult to consider the effect of cracks because there is a high possibility of multi cracks rather than single cracks. In addition, in order to focus on the effect of cracks, it is necessary to take into consideration the moisture absorption of parts other than cracks. In order to solve such a problem, the present invention has developed a single crack generation method in which the crack width is controlled.
For example, in one embodiment of the present invention, the single crack may be a crack formed by performing three-point loading after notch formation. The creation of a single crack using a notch can be performed, for example, according to the following sequence a1) to a8) or a modified method thereof (see Fig. 2).
a1) A notch forming film wire of 3 mm height is attached to the center bottom of the paste mold (Fig. 2, a1).
a2) Two lines of steel wire serving as reinforcing bars at a height of 5 mm from the bottom of the paste mold are installed (Fig. 2, a2).
a3) The uncured paste blended through a paste mixer is put into a mold and subjected to vibration compaction (Fig. 2, a3).
a4) After completion of compaction, curing is carried out for 24 hours in a chamber at a temperature of 20 ± 3 ° C and a relative humidity of 100%.
a5) Remove the sample after 24 hours, demold it and cure for 6 days at 20 ± 3 ℃ and 80 ± 3% relative humidity.
a6) The cured specimen is cured at the notched portion (Fig. 2, a6).
a7) Creates a crack in the form of a three-point load method. At this time, the target crack width can be generated through the displacement control roll using the measurement result of the crack gauge. Care should be taken not to cause a hydration reaction by carbonation and moisture contact due to penetration of carbon dioxide in the crack plane (Fig. 2, a7).
a8) Measure the exact crack width on both sides of the specimen using a microscope and record.
In another embodiment of the present invention, the single crack may be an artificial crack generated by attaching two cement pastes to the single crack. Creation of artificial cracks through paste specimen attachment can be performed, for example, according to the following sequence of b1) to b6) or a modified method thereof (see Fig. 3):
b1) Uncured paste blended through a paste mixer is put into a mold and vibration compaction is performed (Fig. 3, b1).
b2) After completion of compaction, cure for 24 hours in a chamber at 20 ± 3 ° C and 100% relative humidity.
b3) Remove the sample after 24 hours, demold it and cure for 6 days at 20 ± 3 ℃ and 80 ± 3% relative humidity.
b4) Polishing the surface to be contacted of the cured specimen. At this time, be careful not to cause hydration reaction by carbonation and water contact by the penetration of carbon dioxide on the polished surface.
b5) Contact the polished surface of the two specimens and insert the prepared OHP film to form artificial cracks. Use a plastic clamp to fix the specimen on both sides. At this time, the clamp used should be a size that can fit into the water absorption test container (Fig. 3, b5).
b6) Measure the exact crack width on both sides of the specimen using a microscope and record.
In the second step, the absorption rate of the above-mentioned single cracked cement paste is measured. When the water absorption test is performed using the cement paste specimen with cracks, the water penetrates into the paste specimen along with the crack due to capillary suction, and the moisture penetrating along the cracks is absorbed into the concrete from the crack face . Therefore, the area of water absorption becomes larger than that of a crack-free specimen, so that the water absorption rate increases (FIG. 4).
However, as the water absorption proceeds, the unreacted reactant present in the crack causes hydration reaction, causing self-healing of cracks and reducing the crack area (FIG. 5).
In the third step, the self-healing performance is evaluated using the absorption rate change measured based on the measured sorptivity.
In the water uptake experiment, the water uptake is divided into initial sorptivity and secondary sorptivity. The initial water uptake is calculated using the change in mass before 6 hours, and the secondary water uptake is calculated using the results after 6 hours. . This graph is shown in the graph of FIG.
The absorption rate of the cement paste without cracks from the graph can be calculated by the following equation.
here,
The absorption rate can be calculated by the following equation. In expression
Initial absorption rate:
Secondary Absorption Rate:
The absorption rate of the cement paste in which the cracks exist from the graph changes by the self healing, so the absorption rate can be calculated by dividing by the following two equations. The initial absorption rate can be assumed to be up to 6 hours after the start of the absorption rate test and therefore before the crack healing occurs. Therefore, the following equation is used for the absorption rate and absorption rate.
here,
The secondary absorption rate is the result from 6 hours after the absorption rate experiment, so it can be assumed that self-healing has occurred. Therefore, the following equation is used for the absorption rate and absorption rate.
here,
In the present invention, the self-healing performance of cracks is determined by comparing the initial absorption rate in the presence of cracks without cracks and the absorption rate by cracks and comparing the respective secondary absorption rates to calculate the healing area of cracks due to self- Evaluation method.
Assuming that the specimens made from the same material have the same water absorption rate, the mass of water absorbed is proportional to the contact area. Therefore, I c and I c 'have the same value. Therefore, the absorption rates S i and S ci also have the same value.
The relationship between these two equations can be used to calculate the area of the crack.
In the calculation of the secondary absorption rate of a specimen with cracks, a healed crack face is used. In this case, the area of the crack can be calculated by comparing the absorption rate and absorption rate with the specimen without crack. Therefore, the healing area of the crack can be calculated by comparing the crack area before healing calculated from the initial absorption rate and the crack area calculated from the secondary absorption rate.
Hereinafter, the structure and effect of the present invention will be described in more detail with reference to examples and comparative examples. The following examples serve to illustrate the present invention in more detail, and the scope of the present invention is not limited to these examples.
[Psalter preparation]
The specimens were prepared using cement paste. At this time, the cement paste is prepared by appropriately mixing water and binder (cement, fly ash, slag, etc.) and promoting materials (CaSO 4 , Na 2 CO 3, etc.) and the ratio of water to binder and promoting material 0.35. The specimens with cracks and cracks were the same, and specimens were prepared using the method of KS L 5109.
In the case of specimens which generate cracks through loading, 30 mm ⅹ 40 mm ⅹ 200 mm molds are used to place them in the bending test equipment for mortar. In order to create notches, notches with a height of 2 mm x
The specimens were fabricated by using 50 mm ⅹ 50 mm ⅹ 50 mm molds in which the artificial cracks were formed by grinding and pasting one side of two specimens made with cubic molds. Since two specimens are attached to one specimen, the size of the specimen used in the experiment is 50 mm × 50 mm × 100 mm. The area of the crack was 50 mm × 50 mm, and the width of the crack was controlled to 100 ㎛ by using OHP film. The specimens without cracks for comparison were fabricated using 50 mm × 50 mm × 100 mm molds.
[Absorption rate measurement]
The absorption rate measurement was performed in the following order.
Fig. 7 is a schematic diagram for explaining a method of performing absorption rate measurement on a specimen in which cracks exist. Fig.
1. Attach a waterproofing adhesive to the rest of the prepared specimen, except for 10mm on both sides of the crack.
2. Using a vernier caliper, measure the length of the unattached part (± 0.1 mm).
3. The prepared specimen is weighed to the nearest 0.01 g through the balance.
4. Place the spacer in the polyethylene container and fill the bottom of the specimen with 2 ± 1 mm of water. At this time, the temperature of the chamber to be tested is maintained at 20 ± 3 ° C and the relative humidity is 80 ± 3%.
5. Install the specimen so that the mass of the specimen is immersed in the polyethene storage container by 2 ± 1 mm at the bottom. The first mass measurement is 60 ± 2 seconds, the second is 5 minutes ± 10 seconds, and then the mass is measured at 10 minutes, 20 minutes, 30 minutes, and 60 minutes ± 2 minutes. Thereafter, measurements are taken every hour up to 6 hours and daily until 3 days. Three measurements should be taken between 4 and 7 days and the last measurement should be taken after a minimum of 24 hours after 7 days. Record the actual time at which the mass measurement was made.
6. If mass is not more than 10 minutes after immersion, stop the watch and measure. Measure the mass after wiping the specimen with paper towel at each measurement. After 10 minutes, the mass was measured without stopping the watch.
8 is a schematic diagram illustrating the water-absorbing area in a specimen in which cracks are present. In the schematic view, moisture absorption in the crack-free cement paste specimen is via the A surface . On the other hand, moisture absorption in a cracked cement paste specimen occurs at A surface + A crack . Therefore, initial water absorption occurs rapidly in cracked specimens due to the difference in absorbable area. In the experiments carried out by applying the present invention, the absorption areas of the A surface and the A crack of 18 cm 2 and 18 cm 2 , respectively, are as follows.
Absorbable area of specimen without crack (A surface ): 12 cm 2
Absorbable surface area (A surface + A crack ) of cracked specimen: 30 cm 2
In the experiment, two specimens with cracks and two specimens with cracks were used.
FIG. 9 is a graph summarizing the experimental results of the water absorption rate. In the graph, it can be seen that the initial absorption rate and the final absorption rate are lowest when there is no crack. In the case of Mix A and Mix B specimens with cracks, the initial absorption rate is low, while the final absorption rate is low. Based on this, it can be judged that the self-healing effect of Mix B is better. From the experimental results, we have calculated the absorption rate of the cracks in relation to the absorption area. The absorptivity of the crack-free specimen and the existing specimen was calculated as follows. The calculated results are summarized in the table below.
Crack-free specimen: Absorption ÷ A surface
Specimen with crack: Absorption ÷ (A surface + A crack )
The calculated initial absorption rate and secondary absorption rate were compared and it was examined whether the cracks were healed by mixing. As a result, it was confirmed that the cracks were almost healed in 97% of Mix A, whereas 22.2% of Mix B showed almost no cracks. Therefore, it was confirmed that the self-healing effect of Mix A was better through the present invention.
(Initial: 18 cm 2 )
Psalter
Claims (5)
A second step of measuring an absorption rate of the single cracked cement paste specimen; And
Evaluating the self-healing performance using the measured absorption rate change,
The initial absorption rate of the cracked cement paste specimen and the initial absorption rate of the crack-free cement paste specimen are analyzed and the influence of the absorption rate by the crack is analyzed and the initial absorption rate is calculated using the mass change at the initial stage of the absorption rate experiment. And a third step of calculating and evaluating the healing area of the crack due to self-healing by comparing the secondary absorptions of the respective specimens when calculating the secondary absorption rate using the results after 6 hours, to evaluate the self-healing performance of the cement paste How to.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109374870A (en) * | 2018-12-27 | 2019-02-22 | 中交武汉港湾工程设计研究院有限公司 | A kind of evaluation method and device of cement base self-repair material repairing performance |
| KR20190028898A (en) | 2017-09-11 | 2019-03-20 | 가천대학교 산학협력단 | Method for evaluating durability recovery performance of self-healing concrete by measuring change of chloride ion concentration in solution |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002508514A (en) | 1997-12-12 | 2002-03-19 | オスメテック パブリック リミテッド カンパニー | Conductive organic polymer |
| KR101453312B1 (en) * | 2014-03-14 | 2014-10-22 | 한국건설기술연구원 | Permeability Test Method and Apparatus for Self Healing Concrete |
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- 2016-03-07 KR KR1020160027187A patent/KR101741137B1/en active IP Right Grant
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002508514A (en) | 1997-12-12 | 2002-03-19 | オスメテック パブリック リミテッド カンパニー | Conductive organic polymer |
| KR101453312B1 (en) * | 2014-03-14 | 2014-10-22 | 한국건설기술연구원 | Permeability Test Method and Apparatus for Self Healing Concrete |
Non-Patent Citations (2)
| Title |
|---|
| J. Feiteira 외 2명. Self-healing of moving cracks in concrete by means of encapsulated polymer precursors. Construction and Building Materials. 2015년 11월, pp.671~678* |
| 고흡수율 폴리머 종류 및 함량에 따른 시멘트계 재료의 셀프실링 거동(2016.02) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20190028898A (en) | 2017-09-11 | 2019-03-20 | 가천대학교 산학협력단 | Method for evaluating durability recovery performance of self-healing concrete by measuring change of chloride ion concentration in solution |
| CN109374870A (en) * | 2018-12-27 | 2019-02-22 | 中交武汉港湾工程设计研究院有限公司 | A kind of evaluation method and device of cement base self-repair material repairing performance |
| CN109374870B (en) * | 2018-12-27 | 2024-03-29 | 中交武汉港湾工程设计研究院有限公司 | Method and device for evaluating repairing performance of cement-based self-repairing material |
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