JP7512603B2 - Test specimen evaluation method - Google Patents

Description

The present invention relates to a method for evaluating a test specimen having a cement composition.

In general, when measuring the carbonation rate of a cement composition (e.g., concrete or mortar) in a short period of time, accelerated carbonation tests are performed on test specimens in environmental conditions with high carbon dioxide concentrations using a carbonation acceleration test device. In addition, in Patent Document 1, the carbonation rate is analytically estimated, taking into account the deterioration of the cement composition over time, and the progress of carbonation depth over time is predicted.

JP 2011-257212 A

However, there was a risk that the above-mentioned methods would not allow for an accurate evaluation of carbonation. For example, in cases where a surface finishing material is applied to the surface of the cement composition, the carbonation-inhibiting effect of the surface finishing material changes over time, and therefore accelerated carbonation tests alone could produce test results that differ significantly from those of exposure tests in the natural environment. This could lead to an inability to accurately predict the lifespan of a building. Furthermore, even in cases where a surface finishing material is not applied to the surface, there was a risk that test results would differ from those of exposure tests in the natural environment because accelerated carbonation tests were not conducted after accelerated weathering tests.

The present invention was made in consideration of these problems, and its purpose is to improve the accuracy of evaluation of neutralization rate.

The main invention to achieve the above object is:
A method for evaluating a test specimen having a cement composition, comprising:
A first step of subjecting the specimen to an accelerated weathering test;
A second step of performing an accelerated carbonation test using the test specimen after the first step;
having
The accelerated carbonation test is a predetermined period accelerated carbonation test for an accelerated material age of a predetermined period,
When the carbonation depth of the test specimen after the specified period is less than the thickness of the test specimen, a carbonation rate coefficient is calculated from the results of the specified period accelerated carbonation test;
The test specimen includes a first test specimen having a coating material provided on a predetermined surface of a substrate formed from the cement composition, or a second test specimen having no coating material provided on the predetermined surface,
predicting a period until the carbonation depth of the actual structure in the natural environment reaches a predetermined value from a coefficient based on the temperature in the natural environment in which the actual structure of the test specimen is installed, a coefficient based on humidity and the effect of moisture acting on the actual structure, a coefficient based on CO2 _{concentration} , and the carbonation rate coefficient;
The method for evaluating a test specimen is characterized by the following.
Other features of the present invention will become apparent from the following detailed description of the present invention and the accompanying drawings.

The present invention can improve the accuracy of evaluation of neutralization rate.

FIG. 2 is a schematic perspective view showing the shape of a mortar substrate 1 according to the present embodiment. 1 is a schematic perspective view showing a mortar test specimen 10. FIG. FIG. 2 is a diagram showing an outline of the process for producing a mortar test specimen 10. FIG. 1 is a diagram showing the outline of the process of an accelerated weathering test and an accelerated carbonation test. FIG. 2 is a diagram showing cut locations of a mortar test specimen 10 in an accelerated carbonation test. FIG. 1 is a graph showing the relationship between accelerated age and carbonation depth without an accelerated weathering test. FIG. 1 is a diagram showing the relationship between accelerated age and carbonation depth after an accelerated weathering test (1,500 hours). FIG. 1 is a graph showing the relationship between accelerated age and carbonation rate coefficient without accelerated weathering test. FIG. 1 is a diagram showing the relationship between accelerated age and carbonation rate coefficient after an accelerated weathering test (1,500 hours). FIG. 1 is a graph showing the transition of carbonation depth due to an accelerated weather resistance test. FIG. 1 is a graph showing the transition of the neutralization rate coefficient due to an accelerated weathering test. FIG. 1 is a graph showing the transition of the carbonation rate due to an accelerated weather resistance test. FIG. 1 is a flow diagram showing an example of a method for predicting a building lifespan. FIG. 1 is a graph showing the relationship between the accelerated time of a weather resistance test and the carbonation rate coefficient. FIG. 11 is a flow diagram showing another example of a method for predicting a building lifespan. FIG. 1 is a graph showing the relationship between the accelerated time of a weather resistance test and the carbonation rate.

The present specification and accompanying drawings make clear at least the following:

A method for evaluating a test specimen having a cement composition is disclosed, which is characterized by having a first step of conducting an accelerated weathering test on the test specimen, and a second step of conducting an accelerated carbonation test using the test specimen after the first step.

This method of evaluating test specimens makes it possible to obtain accurate carbonation rate test results that are closer to those of exposure tests. This makes it possible to improve the accuracy of the evaluation of carbonation rate.

In the method for evaluating such a test specimen, it is preferable that the test specimen is a substrate formed from the cement composition and a coating material is provided on a predetermined surface of the substrate.

This method of evaluating test specimens allows evaluation to be performed under conditions that are closer to the actual structure.

In such a method for evaluating a test specimen, it is desirable that the thickness of the test specimen be limited to approximately 20 mm.

This method of evaluating specimens allows them to be tested using accelerated weathering test equipment (e.g., the specimens do not fall out of the holder during testing), so accelerated carbonation tests can be performed using specimens that have been subjected to accelerated weathering tests.

In the method for evaluating such a test specimen, the accelerated carbonation test is a predetermined period accelerated carbonation test with an accelerated material age of a predetermined period, and if the carbonation depth of the test specimen after the predetermined period is less than the thickness of the test specimen, it is desirable to calculate the carbonation rate coefficient from the results of the predetermined period accelerated carbonation test.

By using this method of evaluating test specimens, it is possible to determine the carbonation rate coefficient when the accelerated age is at a specified period.

In the method for evaluating such a test specimen, the accelerated carbonation test is a predetermined period accelerated carbonation test with an accelerated material age of a predetermined period, and when the carbonation depth of the test specimen after the predetermined period is equal to or greater than the thickness of the test specimen, it is desirable to calculate the carbonation rate coefficient for the predetermined period using a predetermined calculation formula from the results of the accelerated carbonation test for multiple periods shorter than the predetermined period.

By using this method of evaluating test specimens, the carbonation rate coefficient can be determined even when the carbonation depth at a specified accelerated age is greater than or equal to the thickness of the test specimen.

In such a method for evaluating a test specimen, it is preferable that the specified period is 26 weeks.

Using this method of evaluating test specimens, it is possible to determine the carbonation rate coefficient at 26 weeks.

In the method for evaluating such a test specimen, the test specimen is a first test specimen having a coating material provided on a predetermined surface of a substrate formed from the cement composition, or a second test specimen having no coating material provided on the predetermined surface, and it is desirable to predict the period until the carbonation depth of the actual structure in the natural environment reaches a predetermined value from a coefficient based on the air temperature in the natural environment in which the actual structure of the test specimen is installed, a coefficient based on humidity and the effect of moisture acting on the actual structure, a coefficient based on the CO2 concentration, and the carbonation rate coefficient.

Using this method of evaluating test specimens, the carbonation rate coefficient can be used to predict the lifespan of actual structures (such as buildings).

In the method for evaluating such a test specimen, it is desirable to calculate the carbonation rate coefficient for each of a plurality of time periods, and use the plurality of carbonation rate coefficients to predict the time until the carbonation depth reaches the predetermined value.

This method of evaluating test specimens makes it possible to accurately predict the lifespan of actual structures.

In the method for evaluating such test specimens, the test specimens include a first test specimen having a coating material provided on a predetermined surface of a substrate formed from the cement composition, and a second test specimen having no coating material provided on the predetermined surface, and it is desirable to predict the period until the carbonation depth of the portion of the actual structure having the coating material in the natural environment reaches a predetermined value based on the carbonation rate, which is the ratio of the carbonation depth of the first test specimen to the carbonation depth of the second test specimen, the carbonation depth of the portion of the test specimen having the coating material in the natural environment in which the actual structure is installed, and the carbonation rate coefficient of the portion not having the coating material in the natural environment, which is calculated based on the compressive strength of a standard cured specimen of the actual structure at an age of 28 days.

Using this method of evaluating test specimens, the carbonation rate can be used to predict the lifespan of real structures (such as buildings). Furthermore, when using the carbonation rate coefficient, experiments are required to determine the coefficients due to temperature and the effects of moisture, whereas when using the carbonation rate, it is not necessary to determine the above coefficients (no experiments are required), making it possible to predict the lifespan easily.

In the method for evaluating such a test specimen, it is desirable to calculate the carbonation depth for each of a plurality of time periods, and use the plurality of carbonation depths to predict the period until the carbonation depth reaches the predetermined value.

This method of evaluating test specimens makes it possible to accurately predict the lifespan of actual structures.

== ...
Hereinafter, an embodiment of a structure according to the present invention will be described in detail with reference to the drawings.

Overview
Generally, to measure the carbonation rate of concrete, mortar, etc. in a short period of time, accelerated carbonation tests are conducted using a carbonation acceleration test device under environmental conditions with high carbon dioxide concentrations. Similar accelerated carbonation tests are also conducted for concrete (or mortar) that has been given a surface finish that has a carbonation suppressing effect.

However, accelerated carbonation tests alone may produce test results that are significantly different from those of exposure tests in a natural environment. For example, if the surface finishing material (hereinafter simply referred to as the finishing material) deteriorates faster than concrete due to ultraviolet rays from sunlight or rainfall, or if the carbonation suppression effect of the finishing material changes over time, accelerated carbonation tests alone may produce test results that are significantly different from those of exposure tests in a natural environment. Even if a surface finishing material is not used, the accelerated carbonation test may not produce test results that are significantly different from those of exposure tests in a natural environment because the accelerated weathering test is not performed after the accelerated weathering test. In addition, a finishing material may be applied to a thin plate (plastic plate or steel plate) and an accelerated weathering test is performed, and then the deteriorated finishing material is peeled off and attached to a concrete specimen to perform an accelerated carbonation test. Even in this case, there is a risk that an accurate evaluation cannot be performed because the finishing material and the concrete specimen do not completely adhere to each other (different from the actual state of the concrete surface).

Therefore, in this embodiment, an accelerated weathering test is performed using a mortar specimen with a finishing material, and then an accelerated carbonation test is performed. This makes it possible to obtain accurate carbonation test results that are closer to those of an exposure test in a short period of time.

<Preparation of mortar substrate>
1 is a schematic perspective view showing the shape of a mortar substrate 1 of this embodiment. The mortar substrate 1 was a flat plate specimen having a size of 150×70×20 mm (L in FIG. 1 is 150 mm, H is 70 mm, and W is 20 mm).

The materials used for the mortar substrate 1 of this embodiment are shown in Table 1, and the mortar mix is shown in Table 2. In this embodiment, the mortar substrate 1 uses ordinary Portland cement, and the mix is W/C=65%, 1:3.5 mortar. The surface of the fine aggregate is dry and saturated with water.

モルタルは、１バッチを10Lとし、２バッチ分を練り混ぜた。モルタルの練混ぜは、JIS R 5201：2015「セメントの物理試験方法」の「11.5.2練混ぜ方法」に準じて行った。具体的には、モルタルの練混ぜは、JIS R 5201に従って、公称容量20Lの機械式練混ぜ機により行った。

Two batches of mortar were mixed, each batch being 10 L. The mixing of the mortar was performed in accordance with "11.5.2 Mixing Method" of JIS R 5201:2015 "Physical Test Methods for Cement". Specifically, the mixing of the mortar was performed in accordance with JIS R 5201 using a mechanical mixer with a nominal capacity of 20 L.

First, the specified amount of water (containing chemical admixtures) was added to the mixing bowl, followed by the cement. The mixer was then started at low speed (rotation speed: 140±5 rpm, revolution speed: 62±5 rpm). 30 seconds after starting the paddle, the specified amount of fine aggregate was added over 30 seconds. Next, the speed was increased to high speed (rotation speed: 285±10 rpm, revolution speed: 125±10 rpm) and mixing was continued for another 30 seconds. Mixing was paused for 90 seconds, and scraping was performed during the first 15 seconds of the pause. After the pause, the mixer was started again at high speed and mixed for 60 seconds. After mixing was completed, the mixture was stirred 10 times with a spoon.

The first and second batches of mortar were placed in the mixing bowl of a mechanical mixer with a nominal capacity of 50 L and mixed at low speed for 30 seconds. After mixing, the mixture was stirred 10 times with a spoon and then a fresh property test was conducted.

Mortar substrate 1 was formed by packing mortar into a formwork having the pattern shown in Figure 1 in two layers. Compaction was performed using a ram and a mallet.

<Preparation of mortar test specimen>
Fig. 2 is a schematic perspective view showing the mortar test specimen 10. Fig. 3 is a diagram showing an outline of the steps for producing the mortar test specimen 10.

The mortar (mortar substrate 1) packed in the formwork was sealed and cured until it was 3 days old, and after the formwork was removed on the 3rd day, standard curing was performed until it was 7 days old. This enabled a thin (20 mm here) mortar substrate 1 to be produced without cracking. Note that sealing and curing is not limited to the 3rd day old. For example, sealing and curing may be performed until the 1st day old, and the formwork may be removed on the 1st day old. Furthermore, after the standard curing, air curing was performed in a constant temperature and humidity room at 20°C and 60% RH until it was 35 days old (i.e., 4 weeks). Note that the day after the standard curing was completed, cement paste with W/C=65% was rubbed into the specified surface of the mortar substrate 1 (hereinafter referred to as the coating surface 1A) to fill air bubbles on the surface of the test specimen. This allowed the air bubbles on the coating surface 1A to disappear. The coating surface 1A is the surface to which the clear paint 2 described below is applied, and is also the surface that will be exposed in the accelerated weather resistance test.

In addition, clear paint 2 (corresponding to a coating material) was applied over a period of three days starting two weeks after the air curing (specifically, on the 21st day of the material's life). A short-haired, foam-free roller was used to apply clear paint 2. In this embodiment, the foam-free roller used was a finishing roller with an outer diameter of 27 mm, a total length of 100 mm, a bristle length of 6 mm, and polyester bristle material.

The moisture content of the mortar substrate 1 immediately before application of the clear coating 2 was measured using a concrete/mortar moisture meter manufactured by Kett Electric Laboratory, and confirmed to be 8% or less, which does not impair the adhesion performance of the clear coating. In this embodiment, the measurement was performed in mortar mode, and the average value was 5.5% (8% or less). This allows the clear coating 2 to be applied reliably to the mortar substrate 1.

When applying, the mortar substrate 1 was placed so that the application surface 1A was horizontal, and the clear paint 2 was applied to the application surface 1A using a foamless roller. The remaining five surfaces to which the clear paint 2 was not applied (i.e., the surfaces other than the application surface 1A) were sealed by applying epoxy resin 3 between the 28th and 35th days of the material's age.

<Test items for mortar>
The test items of the mortar are shown in Table 3. The fresh property test was carried out by taking samples immediately after mixing. The test items were 0 hit flow, 15 hit flow, air volume, and mortar temperature as shown in the table.

Compressive strength tests were conducted to assess the hardening properties. The compressive strength specimens were demolded on the third day of age, similar to mortar substrate 1. Standard curing specimens were tested on the seventh and 28th day of age. Meanwhile, specimens that were cured in the same manner as the flat specimens were tested on the 35th day of age (the start date of the accelerated carbonation test or accelerated weathering test).

≪クリヤ塗料の構成と塗布量について≫
今回の実験で使用したクリヤ塗料の概要を表４に示す。いずれの銘柄も水系のクリヤ塗料である。Ａ社製の中塗り材は、顔料入りと顔料なしの２種類がある。Ｂ社製は、顔料入りの仕様のみであり、Ｃ社製は、顔料なしの仕様である。なお、上塗り材は、いずれも顔料なしの使用である。

<About the composition and application amount of clear paint>
Table 4 shows an overview of the clear paints used in this experiment. All brands are water-based clear paints. The undercoat materials made by Company A come in two types, one with pigment and one without. Company B only has the pigmented version, and Company C has the unpigmented version. All topcoat materials used are unpigmented.

モルタル基板１に塗布したクリヤ塗料２の材料構成と塗布量を表５および表６に示す。なお、表５は、促進耐候性試験を行わない場合の試験体を示し、表６は、促進耐候性試験を行なう場合の試験体を示している。各表に示すように、試験体Ｎｏ.１は、クリヤ塗料２を塗布しない試験体であり、試験体Ｎｏ.２～Ｎｏ.８は、クリヤ塗料２を塗布する試験体である。

The material composition and application amount of the clear paint 2 applied to the mortar substrate 1 are shown in Tables 5 and 6. Table 5 shows the test specimens when the accelerated weather resistance test was not performed, and Table 6 shows the test specimens when the accelerated weather resistance test was performed. As shown in each table, test specimen No. 1 is a test specimen that was not coated with the clear paint 2, and test specimens No. 2 to No. 8 are test specimens that were coated with the clear paint 2.

Test specimen No. 1b (Table 6) for the accelerated weathering test was completely covered with an aluminum bag and sealed to prevent water from being sprayed on the exposed surface of the mortar during the test. When the accelerated weathering test was completed and the accelerated carbonation test was performed, the aluminum bag was removed and the test was performed.

<Accelerated weathering test and accelerated carbonation test>
Figure 4 is a diagram showing the outline of the process of the accelerated weathering test and the accelerated carbonation test. As shown in the figure, an accelerated carbonation test was performed on a mortar specimen coated with a clear paint, and the influence of the material composition and the coating amount of the clear paint on the carbonation suppression effect of the mortar was quantitatively confirmed.

The accelerated carbonation test was carried out in two cases: after pouring the mortar, one week of standard curing and four weeks of air curing (Comparative Example), and after one week of standard curing, four weeks of air curing, and an accelerated weathering test (Example). The effect of deterioration of the clear paint 2 coating itself on the carbonation suppression effect was also confirmed. A sunshine carbon arc lamp type weathering tester was used for the accelerated weathering test. The accelerated weathering test was carried out for three test times: 1500 hours, 3000 hours, and 5000 hours. The test times correspond to 6, 12, and 20 years of outdoor exposure (see Structural Engineering Journal of the Architectural Institute of Japan, Vol. 584, pp. 15-21, October 2004).

<Accelerated weather resistance test>
The accelerated weathering test was carried out using a sunshine weather meter that meets the standard of JIS B 7753:2007 "Sunshine carbon arc lamp type light resistance tester and weather resistance tester". The outline of the sunshine weather meter is shown in Table 7. The test conditions were in accordance with JIS K 7350-4:2008 "Plastics - Exposure test method with laboratory light source - Part 4: Open flame carbon arc lamp" and JIS A 1415:1999 "Exposure test method with laboratory light source for polymeric building materials". The spray conditions are shown in Table 8. As shown in Table 8, the "spray cycle 1" of "6.3 Spray conditions" of JIS K 7350-4 was used. The test times were 1500 hours, 3000 hours, and 5000 hours, assuming exposure for 6, 12, and 20 years, as mentioned above.

In addition to the sunshine carbon arc lamp type (JIS B 7753:2007), the following accelerated weather resistance testers are JIS standards.
JIS B 7751: 2007 UV carbon arc light resistance tester and weather resistance tester
JIS B 7754: 1991 Xenon arc lamp type light resistance and weather resistance tester
In any of the testers, if the thickness of the test specimen is too large, the distance from the light source of the tester becomes too close, and the test specimen deteriorates quickly, so there is a limit to the thickness that can be tested. Specifically, in order to prevent the test specimen from falling from the holder during the test, the thickness limit needs to be about 2 cm (20 mm). In this embodiment, the thickness of the test specimen (mortar test specimen 10) is set to 20 mm, so that the accelerated weather resistance test can be performed with the above tester.

In addition, the test method is based on the following JIS standards.
JIS A 1415:2013 Exposure test method for polymeric building materials using laboratory light sources
JIS K 7350-1: 1995 Plastics - Exposure test method using laboratory light source Part 1: General rules
JIS K 7350-2: 2008
Plastics -- Exposure test methods using laboratory light sources -- Part 2: Xenon arc lamp
JIS K 7350-3: 2008
Plastics - Exposure test methods using laboratory light sources - Part 3: UV fluorescent lamps In addition, the following JIS standard exists as an accelerated weathering test method for paints.
JIS K 5600-7-7 Accelerated weather resistance and accelerated light resistance (xenon lamp method)
JIS K 5600-7-8 Accelerated weather resistance (ultraviolet fluorescent lamp method)

<Accelerated Neutralization Test>
The accelerated carbonation test of the mortar specimen 10 coated with the clear coating 2 was conducted in accordance with JIS A 1153. The test ages were 1 week, 4 weeks, 8 weeks, 13 weeks, and 26 weeks, and the mortar specimen 10 was cut at each age to measure the carbonation depth. Figure 5 shows the cut locations of the mortar specimen 10 in the accelerated carbonation test. Note that the clear coating 2 and the epoxy resin 3 are omitted (hatched) in Figure 5. Each cut surface of the mortar specimen 10 was sealed with epoxy resin.

<Test Results>
<Fresh properties>
The fresh property test was carried out immediately after the first batch was mixed and immediately after the first and second batches were combined. The results of the fresh property test are shown in Table 9. The air content satisfied the target value of 4.5±1.5%.

＜モルタルの硬度性状＞
モルタルの圧縮強度の試験結果を表１０，表１１に示す。モルタル平板試験体と同じ養生条件とした供試体の材齢35日の圧縮強度は22.6Ｎ/mm^２であった。なお、モルタル平板試験体の促進中性化試験および促進耐候性試験は、材齢35日より開始した。この結果より、圧縮強度には特に問題がないことを確認した。

<Hardness properties of mortar>
The test results of the compressive strength of the mortar are shown in Tables 10 and 11. The compressive strength of the specimen, which was cured under the same conditions as the mortar plate specimens, at an age of 35 days was 22.6 N/ ^mm2 . The accelerated carbonation test and accelerated weathering test of the mortar plate specimens were started at an age of 35 days. These results confirmed that there were no particular problems with the compressive strength.

<Neutralization depth>
Figures 6 and 7 show the relationship between accelerated age and carbonation depth. Figure 6 shows the results without accelerated weathering test (0 hours of weathering test), and Figure 7 shows the results with accelerated weathering test (1500 hours of weathering test). In Figure 6, the carbonation depth of the specimens coated with clear paint (specimens No. 2 to No. 8) is smaller than that of the specimen without clear paint (specimen No. 1) at the same age (carbonation suppression effect). At an accelerated age of 26 weeks, the carbonation depth of the specimen without clear paint almost reaches the thickness of the mortar specimen (20 mm), but that of the specimen coated with clear paint is 5 mm or less. A similar tendency is seen in Figure 7. In Figure 7, the carbonation depth of specimen No. 1b (sealed) without clear paint is smaller than that of specimen No. 1a (unsealed) without clear paint.

<Neutralization rate coefficient>
Figures 8 and 9 show the relationship between accelerated age and carbonation rate coefficient. Note that Figure 8 shows the results without accelerated weathering test (weathering test for 0 hours), and Figure 9 shows the results with accelerated weathering test (weathering test for 1500 hours). The carbonation rate coefficients of the specimens coated with clear paint (specimens No. 2 to No. 8) are smaller than that of the specimen without clear paint (specimen No. 1).

<Changes in carbonation depth, carbonation rate coefficient, and carbonation rate through accelerated weathering tests>
Fig. 10 shows the progress of carbonation depth in accelerated weathering test, Fig. 11 shows the progress of carbonation rate coefficient in accelerated weathering test, and Fig. 12 shows the progress of carbonation rate in accelerated weathering test. Note that carbonation rate is the ratio of carbonation depth of concrete with finishing material to that of concrete without finishing material (see formula 5 below) (from JASS5 reinforced concrete work, Architectural Institute of Japan: Standard Specifications for Building Construction and Commentary). The horizontal axis of each of these figures is the test time of the accelerated weathering test.

As shown in the figure, even after 3,000 hours of weather resistance testing (equivalent to 12 years of exposure), neutralization was suppressed in the test specimens coated with clear paint.

<<Prediction of Building Lifespan (Prediction Method 1)>>
13 is a flow diagram showing an example of a method for predicting the lifespan of a building, in which the lifespan of a building is predicted using a carbonation rate coefficient.

First, as shown in FIG. 13, a finished test specimen or an unfinished test specimen is prepared (S101). In this embodiment, the finished test specimens are mortar test specimens 10 (test specimens No. 2 to No. 8) in which clear paint 2 is applied to the application surface 1A of the mortar substrate 1, and the unfinished test specimen is a test specimen (test specimen No. 1) in which clear paint 2 is not applied to the mortar substrate 1.

Next, an accelerated weathering test is performed using the test specimen (corresponding to S102: first step). This accelerated weathering test deteriorates the concrete (mortar) surface of the test specimen or the finishing material (clear paint 2 in this case) on the surface of the test specimen. The deterioration period is multiple points (multiple periods). For example, when a test is performed using a sunshine carbon arc lamp weathering tester specified in JIS B 7753:2007 in accordance with JIS K 7350-4:2008 "Plastics - Exposure test methods using laboratory light sources - Part 4: Open flame carbon arc lamp" and JIS A 1415:2013 "Exposure test methods using laboratory light sources for polymeric building materials", it is known that 250 hours of accelerated testing is equivalent to one year of outdoor exposure in the Kanto region. Here, the accelerated weathering test is performed for three periods (1500 hours, 3000 hours, and 5000 hours) (corresponding to outdoor exposure for 6 years, 12 years, and 20 years, respectively).

Next, an accelerated carbonation test is conducted using the specimens that have undergone the accelerated weathering test (corresponding to S103: second step). In other words, an accelerated carbonation test is conducted on specimens whose concrete surface or finishing material has deteriorated due to the accelerated weathering test. The carbonation depth is measured at accelerated ages of 1, 4, 8, 13, and 26 weeks in accordance with JIS A 1153:2012 "Accelerated carbonation test method for concrete". Alternatively, measurements at other accelerated ages up to 26 weeks may be performed. If the carbonation depth reaches the thickness of the specimen (20 mm) or more at an accelerated age up to 26 weeks, the carbonation depth at 26 weeks can be estimated by the least squares method using the carbonation depth measurement values prior to 26 weeks.

In addition, the neutralization rate coefficient A, which changes over time, is calculated from the measured (or estimated) neutralization depth using the following (Equation 1) (S104).

C=A√t (Equation 1)
C: Carbonation depth (mm)
A: Carbonation rate coefficient (mm/√week)
t: Accelerated age (weeks)
(From the Architectural Institute of Japan: Standard Specifications for Building Construction and Commentary JASS5 Reinforced Concrete Construction (2018))
Specifically, from the relationship between the accelerated time (elapsed time of outdoor exposure) of the weathering test at multiple points and the carbonation rate coefficient A, a curve equation or a linear equation (a function with the material age T under natural environment as a variable) of the change over time of the carbonation rate coefficient is obtained by the least squares method. Fig. 14 is a diagram showing the relationship between the accelerated time of the weathering test and the carbonation rate coefficient. In Fig. 14, the carbonation rate coefficient is obtained for each of three accelerated times, and a regression curve or regression line is obtained by the least squares method from the data from multiple stores. This makes it possible to estimate the carbonation rate coefficient A at any material age.

The accelerated carbonation test is carried out in an environment with a temperature of 20°C, a relative humidity of 60%RH, and a _CO2 concentration of 5.0% (on the other hand, the _CO2 concentration in the natural environment is generally around 0.05% outdoors and around 0.10% to 0.20% indoors). In this way, the accelerated carbonation test is carried out in an environment with a high _CO2 concentration.

Next, a coefficient β ₁ depending on the temperature in the natural environment, a coefficient β ₂ depending on the humidity and the effect of moisture on the concrete, and a coefficient β ₃ depending on the CO ₂ concentration are calculated (S105).

Then, the age T (weeks) at which the neutralization depth C in the natural environment reaches the cover thickness of the rebar is calculated (S106).

First, the neutralization rate coefficient _A1 in actual exposure under a natural environment is calculated using the following (Equation 2).
_A1 = k _{α1 α2 α3 β1 β2 β3} (Equation 2)
_A1 : Neutralization rate coefficient in actual exposure under natural environment (mm/√year)
k: constant related to the carbonation rate (mm/√year)
_α1 : Coefficient due to type of concrete (type of aggregate) _α2 : Coefficient due to type of cement _α3 : Coefficient due to mix (water-cement ratio) _β1 : Coefficient due to temperature _β2 : Coefficient due to humidity and the effect of moisture on concrete _β3 : Coefficient due to _CO2 concentration (From the Architectural Institute of Japan: Guidelines and Commentary on Durability Design and Construction of Reinforced Concrete Buildings (2016))

The coefficient k relating to the carbonation rate, the coefficient α1 depending on the type of concrete (type of aggregate) _, the coefficient _{α2 depending on the type of cement, and} the coefficient _α3 depending on the mix (water-cement ratio) have already been reflected by the accelerated carbonation test. Note that the coefficient k relating to the carbonation rate also includes a coefficient due to the influence of finishing. Therefore, the carbonation rate coefficient A obtained by the accelerated carbonation test can be converted to the carbonation rate coefficient _A1 in actual exposure by the following (Equation 3).

Furthermore, when determining the neutralization depth under natural conditions using the neutralization rate coefficient obtained in the accelerated neutralization test, taking β _{1 ,} β _{2 , and} β ₃ into consideration, (Equation 4) is obtained.

C = A β ₁ β ₂ β ₃ √T (Equation 4)
C: Carbonation depth (mm)
A: Carbonation rate coefficient (mm/√week)
β ₁ : Coefficient due to temperature β ₂ : Coefficient due to humidity and the effect of moisture on concrete β ₃ : Coefficient due to CO ₂ concentration T: Age of material (weeks)

The carbonation depth C at multiple material ages T is calculated using (Equation 4) and plotted, for example, on a graph with material age T on the horizontal axis and carbonation depth C on the vertical axis. Then, a regression curve or regression line of the relationship between material age T and carbonation depth C is obtained using the least squares method or the like. This regression equation is used to determine the material age T at which carbonation depth C reaches the cover thickness of the rebar (S106). This makes it possible to predict the building's lifespan.

As explained above, this embodiment uses a mortar test specimen 10 with a clear coating 2 applied to the coating surface 1A of a mortar substrate 1, and includes step S102 (first step) of conducting an accelerated weathering test on the mortar test specimen 10, and step S103 (second step) of conducting an accelerated carbonation test using the mortar test specimen 10 after the accelerated weathering test. This makes it possible to obtain accurate carbonation rate test results that are closer to those of an exposure test, even when the clear coating 2 is applied. This makes it possible to improve the accuracy of evaluations of the carbonation rate (such as predictions of the building lifespan).

<<Prediction of Building Lifespan (Prediction Method 2)>>
15 is a flow diagram showing another example of a method for predicting the lifespan of a building, in which the lifespan of a building is predicted using a carbonation rate.

First, as shown in FIG. 15, a finished test specimen and an unfinished test specimen are prepared (S201). In this embodiment, the finished test specimens are mortar test specimens 10 (test specimens No. 2 to No. 8) in which clear paint 2 has been applied to the application surface 1A of the mortar substrate 1, and the unfinished test specimen is a test specimen (test specimen No. 1) in which clear paint 2 has not been applied to the mortar substrate 1.

Next, an accelerated weathering test is performed using each test specimen (S202). The accelerated weathering test is the same as step S102 in FIG. 13, so a description thereof is omitted.

Next, an accelerated carbonation test is performed using the test specimens that have been subjected to the accelerated weathering test (S203). The accelerated carbonation test is the same as step S103 in FIG. 13, so a description thereof is omitted.

Next, the carbonation rate that changes over time is calculated from the carbonation depth measurement (or estimated value) at 26 weeks using the following (Equation 5) (S203).

Neutralization rate= _c1 / _c2 (Equation 5)
_c1 : Carbonation depth of finished concrete _c2 : Carbonation depth of unfinished concrete From the relationship between the accelerated time (elapsed time of outdoor exposure) of the weathering test at multiple points and the carbonation rate, a curve equation or a linear equation (a function with the material age T under natural environment as a variable) of the change over time of the carbonation rate is obtained by the least squares method. Fig. 16 is a diagram showing the relationship between the accelerated time of the weathering test and the carbonation rate. Even in this case, the carbonation rate at any material age can be estimated from the data at multiple points.

Next, the carbonation rate is used to predict the lifespan of a building. First, the carbonation rate coefficient _A0 of unfinished concrete is calculated using (Equation 6) from a previous paper (Proceedings of the Japan Concrete Institute, Vol. 28, No. 1, 2006, pp. 665-670) (S204). Then, by multiplying the right-hand side of (Equation 7) by the carbonation rate ( _c1 / _c2 ) that changes over time, the carbonation depth _C1 of finished concrete can be calculated as shown in (Equation 8).

A ₀ =23.8(1/√f-0.13) ... (Equation 6)
C=A ₀ √T (Equation 7)
C: Carbonation depth of (unfinished) concrete exposed outdoors (mm)
A ₀ : Carbonation rate coefficient obtained from previous literature (mm/√year)
f: Compressive strength of standard cured specimen at 28 days (N/ ^mm2 )
T: Age (years)

_C1 = _c1 / _c2 × _A0√T (Equation 8)
_C1 : Carbonation depth of concrete with finish exposed outdoors (mm)
_c1 : Carbonation depth of finished concrete (measured value in accelerated carbonation test)
_c2 : Carbonation depth of unfinished concrete (measured value in accelerated carbonation test)
Here, the carbonation depth _C1 at multiple material ages is calculated using (Equation 8), and a regression curve or regression line of the relationship between the material age T and the carbonation depth _C1 is obtained. The material age T at which the carbonation depth _C1 reaches the cover thickness of the reinforcing bar is obtained using this regression equation (S206). This makes it possible to predict the lifespan of the building.

If the carbonation rate coefficient of unfinished concrete is already known, the right-hand side of the above formula (1) can be multiplied by the carbonation rate ( _c1 / _c2 ), which changes over time, to predict the age at which the carbonation depth will reach the reinforcing bars, i.e., the lifespan of the building.

Using the carbonation rate in this way can improve the accuracy of the evaluation of the carbonation rate (such as prediction of the life of a building) in the same way as using the carbonation rate coefficient. Furthermore, when using this carbonation rate, it is not necessary to calculate the coefficients (coefficient _β1 due to air temperature, coefficient β2 due to the influence of moisture on humidity and concrete _{, and} coefficient _β3 due to _CO2 concentration) used when using the carbonation rate coefficient, and evaluation can be simplified.

===Other embodiments===
The above-mentioned embodiment is for the purpose of facilitating understanding of the present invention, and is not intended to limit the present invention. The present invention can be modified or improved without departing from the spirit of the present invention, and it goes without saying that the present invention includes equivalents thereof.

In the above embodiment, a mortar substrate 1 was used, but the substrate may be made of other cement compositions (e.g., concrete).

In the above embodiment, the clear paint 2 is applied to the application surface 1A of the mortar substrate 1, but this is not limited to this and other coating materials may be applied. For example, resin paint, resin film, tiles, stone, or other finishing materials may be applied.

In addition, in the above embodiment, the surfaces (five surfaces) other than the application surface 1A of the mortar substrate 1 were sealed by applying epoxy resin, but this is not limited to this and other sealing materials may be applied.

1 Mortar substrate 1A Coating surface (predetermined surface)
2 Clear paint (coating material)
3 Epoxy resin 10 Mortar test specimen

Claims (8)

A method for evaluating a test specimen having a cement composition, comprising:
A first step of subjecting the specimen to an accelerated weathering test;
A second step of performing an accelerated carbonation test using the test specimen after the first step;
having
The accelerated carbonation test is a predetermined period accelerated carbonation test for an accelerated material age of a predetermined period,
When the carbonation depth of the test specimen after the specified period is less than the thickness of the test specimen, a carbonation rate coefficient is calculated from the results of the specified period accelerated carbonation test;
The test specimen includes a first test specimen having a coating material provided on a predetermined surface of a substrate formed from the cement composition, or a second test specimen having no coating material provided on the predetermined surface,
predicting a period until the carbonation depth of the actual structure in the natural environment reaches a predetermined value from a coefficient based on the temperature in the natural environment in which the actual structure of the test specimen is installed, a coefficient based on humidity and the effect of moisture acting on the actual structure, a coefficient based on _CO2 concentration, and the carbonation rate coefficient;
A method for evaluating a test specimen, comprising: A method for evaluating a test specimen having a cement composition, comprising:
A first step of subjecting the specimen to an accelerated weathering test;
A second step of performing an accelerated carbonation test using the test specimen after the first step;
having
The accelerated carbonation test is a predetermined period accelerated carbonation test for an accelerated material age of a predetermined period,
When the carbonation depth of the test specimen after the predetermined period is equal to or greater than the thickness of the test specimen, a carbonation rate coefficient for the predetermined period is calculated using a predetermined calculation formula from the results of the accelerated carbonation test for a plurality of periods shorter than the predetermined period;
The test specimen includes a first test specimen having a coating material provided on a predetermined surface of a substrate formed from the cement composition, or a second test specimen having no coating material provided on the predetermined surface,
predicting a period until the carbonation depth of the actual structure in the natural environment reaches a predetermined value from a coefficient based on the temperature in the natural environment in which the actual structure of the test specimen is installed, a coefficient based on humidity and the effect of moisture acting on the actual structure, a coefficient based on _CO2 concentration, and the carbonation rate coefficient;
A method for evaluating a test specimen, comprising: A method for evaluating a test specimen according to claim 1 or 2, comprising:
The test specimen is a substrate formed from the cement composition and a coating material provided on a predetermined surface of the substrate.
A method for evaluating a test specimen, comprising: A method for evaluating a test specimen according to any one of claims 1 to 3, comprising:
The thickness of the test specimen is limited to about 20 mm.
A method for evaluating a test specimen, comprising: A method for evaluating a test specimen according to any one of claims 1 to 4, comprising:
The predetermined period is 26 weeks.
A method for evaluating a test specimen, comprising: A method for evaluating a test specimen according to any one of claims 1 to 5, comprising:
Calculating the neutralization rate coefficient for each of a plurality of time periods;
predicting a period until the neutralization depth reaches the predetermined value using a plurality of the neutralization rate coefficients;
A method for evaluating a test specimen, comprising: A method for evaluating a test specimen having a cement composition, comprising:
A first step of subjecting the specimen to an accelerated weathering test;
A second step of performing an accelerated carbonation test using the test specimen after the first step;
having
The accelerated carbonation test is a predetermined period accelerated carbonation test for an accelerated material age of a predetermined period,
When the carbonation depth of the test specimen after the specified period is less than the thickness of the test specimen, a carbonation rate coefficient is calculated from the results of the specified period accelerated carbonation test;
The test specimens include a first test specimen having a coating material provided on a predetermined surface of a substrate formed from the cement composition, and a second test specimen having no coating material provided on the predetermined surface;
a carbonation rate, which is a ratio of the carbonation depth of the first test body to the carbonation depth of the second test body;
the carbonation depth of the portion where the covering material is provided in the natural environment in which the actual structure of the test specimen is installed; and
a carbonation rate coefficient of a portion where the covering material is not provided under the natural environment, which is obtained based on the compressive strength of a standard cured specimen of the actual structure at 28 days old; and
and predicting a period until the carbonation depth of the portion of the actual structure provided with the covering material in the natural environment reaches a predetermined value.
A method for evaluating a test specimen, comprising: A method for evaluating a test specimen having a cement composition, comprising:
A first step of subjecting the specimen to an accelerated weathering test;
A second step of performing an accelerated carbonation test using the test specimen after the first step;
having
The accelerated carbonation test is a predetermined period accelerated carbonation test for an accelerated material age of a predetermined period,
When the carbonation depth of the test specimen after the predetermined period is equal to or greater than the thickness of the test specimen, a carbonation rate coefficient for the predetermined period is calculated using a predetermined calculation formula from the results of the accelerated carbonation test for a plurality of periods shorter than the predetermined period;
The test specimens include a first test specimen having a coating material provided on a predetermined surface of a substrate formed from the cement composition, and a second test specimen having no coating material provided on the predetermined surface;
a carbonation rate, which is a ratio of the carbonation depth of the first test body to the carbonation depth of the second test body;
the carbonation depth of the portion where the covering material is provided in the natural environment in which the actual structure of the test specimen is installed; and
a carbonation rate coefficient of a portion where the covering material is not provided under the natural environment, which is obtained based on the compressive strength of a standard cured specimen of the actual structure at 28 days old; and
and predicting a period until the carbonation depth of the portion of the actual structure provided with the covering material in the natural environment reaches a predetermined value.
A method for evaluating a test specimen, comprising:

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