JP3451617B2 - Deterioration quantitative evaluation method of steam cured lightweight cellular concrete - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for quantitatively evaluating the degree of deterioration by sampling steam-cured lightweight cellular concrete used as a building material.

[0002]

2. Description of the Related Art Steam-cured lightweight aerated concrete (lightweight aerated concrete: ALC) is a lightweight concrete material having an absolute dry bulk specific gravity of about 0.5, and has fire resistance, heat insulation,
Because of its excellent workability, it is widely used as a panel for walls, roofs, or floors of buildings.

Generally, steam-cured lightweight cellular concrete panels are manufactured by the following procedure.

Silicic materials such as silica stones and silica sand and calcareous materials such as cement and quick lime are used as main materials, and if necessary, repeated materials, gypsum, calcium carbonate, surfactants, water repellent performance-imparting agents, etc. Additives, an appropriate amount of water, and aluminum powder as a foaming agent are added and kneaded to form a slurry. This slurry is poured into a mold in which reinforcing bars have been set in advance. At the same time as the foaming of the foaming agent, hardening due to a hydration reaction gradually occurs, and a semi-plastic material containing bubbles is obtained.

Depending on the manufacturing method, blast furnace slag, fly ash, lime charcoal, etc. are used as the siliceous raw material,
As a substitute for the foaming agent, there is a case where a preform system in which bubbles prepared in advance are kneaded with a slurry is adopted.

After a lapse of a desired time, the semi-plastic material hardened to an appropriate hardness is taken out of the mold, cut into a desired size with a piano wire or a blade, and then cured by high temperature and high pressure steam in an autoclave to obtain a main component. Tobermorite-1
1A (11A means 11 angstrom,
It means a repeating unit in the thickness direction of the layer of tobermorite which is a layered mineral. ) Is a steam-cured lightweight cellular concrete panel.

As described above, the steam-cured lightweight cellular concrete is mainly composed of silicate and calcium,
By steam-curing, calcium silicate hydrate, tobermorite-11A, is produced. This Tobermorite-11A
Then, the raw material silicate that remains as an unreacted substance becomes the main substance constituting the steam-cured lightweight cellular concrete.

When such steam-cured lightweight aerated concrete is used as a building material, the steam-cured lightweight aerated concrete itself takes in moisture and reacts with carbon dioxide gas in the atmosphere, and tobermorite-11A becomes amorphous silicate (silica gel). ) And calcium carbonate, a so-called carbonation reaction occurs. Decomposition degree of Tobermorite-11A varies depending on atmospheric humidity and carbon dioxide gas concentration, and progresses rapidly, especially when the relative humidity of the atmosphere is high. Therefore, depending on the condition of the building, the degree of carbonation may vary. different. It is difficult to completely suppress the progress of carbonation even by the surface finishing material.

The steam-cured lightweight aerated concrete shrinks by carbonation, and the carbonated steam-cured lightweight aerated concrete has a drying shrinkage factor of 2 to several times that of the non-carbonated steam-cured lightweight aerated concrete. Therefore, the length changes depending on the change in the relative humidity of the atmosphere. Due to these changes in length,
The steam-cured lightweight aerated concrete has network-like cracks and cracks.

The cracks generated on the surface or inside of such steam-cured lightweight cellular concrete in a building which has been continuously used for many years spoils the appearance of the building.
This is a major problem because it causes rainwater to enter, strength of the building to be reduced, bending, deterioration of appearance, and falling debris.

[0011] Therefore, in order to improve the durability of steam-cured lightweight cellular concrete, manufacturers make a clear indication of the selection of a finishing material and a repair time, a method of repairing a deteriorated steam-cured lightweight cellular concrete panel, and further, a carbon dioxide resistant method. We are working on the development of a computerized panel. However, since a method for quantitatively evaluating carbonation of steam-cured lightweight cellular concrete has not been established, comparing various experimental data,
There is a problem that it is difficult to examine and consider the above-mentioned repair method and development of carbonation-resistant panel, and the results of each research are not efficiently applied to development and application to products.

The deterioration of steam-cured lightweight cellular concrete used in buildings is evaluated mainly by a method of visually observing the degree of cracking. However, since accurate quantitative evaluation of deterioration is not possible with this method, a method is conceivable in which fragments of steam-cured lightweight cellular concrete that are actually used are collected and quantitatively measured by chemical analysis or the like.

However, calcium is tobermorite-1.
1A and calcium carbonate produced by carbonation, silicon is contained in tobermorite-11A, amorphous silicate decomposed and produced by carbonation, and unreacted raw material silicate. Therefore, from elemental analysis such as chemical analysis, it is impossible to quantitatively measure the remaining tobermorite-11A without decomposition, the amorphous silicate formed by carbonation, and the calcium carbonate.

As a method for quantitatively measuring a crystalline substance, not a method for quantitatively measuring an element, there is a powder X-ray diffraction method. When the collected fragments are analyzed by an X-ray diffractometer, amorphous silicate is not detected, but the presence or absence of tobermorite-11A and calcium carbonate can be determined, and quantitative analysis of crystalline substances can be performed. . However, since steam-cured lightweight aerated concrete contains by-products in the manufacturing process, additives when additives are added, and many new substances that are generated by the reaction due to deterioration, there are many cases in which X-ray diffraction It is difficult to make accurate quantitative measurements with a device.

Therefore, it is conceivable to compare the detected peak intensities, but in the X-ray diffractometer, since there is no correlation between the peak intensity and the content, only comparison based on a normal product can be performed and water vapor When judging the degree of deterioration (deterioration degree) of cured light-weight cellular concrete, it was impossible to grasp it as a numerical value, that is, quantitative evaluation.

[0016]

SUMMARY OF THE INVENTION The problem to be solved by the present invention is tobermorite-11 when deteriorated by using steam-cured lightweight cellular concrete as a building.
An object of the present invention is to provide a method for quantitatively accurately evaluating the degree of deterioration of steam-cured lightweight cellular concrete by quantitatively measuring the calcium carbonate produced by decomposition of A accurately.

[0017]

In order to solve the above-mentioned problems, the method of the present invention is a method for measuring the amount of calcium carbonate in a test sample of steam-cured lightweight aerated concrete by thermal analysis. A calcium oxide conversion amount C and a calcium oxide conversion amount Cmax of total calcium obtained by quantitatively measuring the total calcium content are obtained, and C
The deterioration degree of the test sample is quantitatively evaluated by the carbonation degree Dc1 (%) of the formula / Cmax × 100.

The amount of calcium oxide, calcium hydroxide, and the amount of calcium in the cement used in the manufacturing process of steam-cured lightweight aerated concrete is converted to the amount of calcium oxide to calculate the calcium oxide equivalent of the total calcium. Cmax may be obtained.

Alternatively, with respect to a test sample of steam-cured lightweight cellular concrete, the calcium carbonate equivalent amount C (wt%) of calcium carbonate obtained by quantitatively measuring the calcium carbonate content by a thermal analysis method and the total calcium content are quantitatively measured. Calcium oxide equivalent Cmax of total calcium obtained by
(Wt%), a calcium oxide equivalent Cs (wt%) of calcium sulfate obtained by quantitatively measuring the total sulfur content, and a thermal analysis of an uncarbonated sample produced by the same production method as the test sample. To obtain a calcium oxide equivalent amount C0 (% by weight) of calcium carbonate, which is obtained by quantitatively measuring the calcium carbonate content by the method of (C-C0) / (Cmax-Cs-C
0) × 100 The degree of carbonation Dc2 (%) is used to quantitatively evaluate the degree of deterioration of the test sample.

The thermal analysis method for quantitatively measuring the calcium carbonate content uses a thermogravimetric-differential thermal analyzer (TG-DTA) to measure the weight loss of carbon dioxide corresponding to the endothermic peak at 600 ° C to 900 ° C. It is preferable that the method is

The test sample having a carbonation degree of 50% or more is diagnosed as having deteriorated durability.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION As a first embodiment of the method of the present invention, when calcium carbonate is decomposed at around 600 to 900 ° C. by a thermal analysis method with respect to a test sample of steam-cured lightweight cellular concrete. The amount of weight loss corresponding to the generated carbon dioxide gas is quantitatively measured, the calcium carbonate content in the test sample is calculated from this amount of weight loss, and the amount C converted into the amount of calcium oxide and the total calcium content in the chemical analysis are calculated. Quantitative measurement is performed to obtain the amount Cmax converted into the amount of calcium oxide, and the carbonation degree, that is, C / Cmax × 100 is calculated to quantitatively evaluate the deterioration degree of the test sample by the carbonation degree. Is the way to do it. To measure the carbonation degree of ALC,
It is necessary to measure the binding amount of carbon dioxide and the calcium content.

In the second embodiment of the method of the present invention, the carbonation degree Dc of the steam-cured lightweight cellular concrete is [(C-C
0) / (Cmax-Cs-C0) × 100].

The symbols in the formula are as described above, and C is
It is a calcium oxide conversion amount (wt%) obtained by quantitatively measuring a calcium carbonate content by a thermal analysis method, Cmax is a calcium oxide conversion amount (wt%) obtained by quantitatively measuring a total calcium content, and Cs is a calcium sulfate content. It is a quantitatively measured calcium oxide equivalent (% by weight). C0 is the amount of calcium oxide equivalent (% by weight) in the uncarbonated sample (standard sample) manufactured by the same manufacturing method as the test sample, that is, the calcium carbonate content other than tobermorite is quantitatively measured by thermal analysis. Is. By calculating the carbonation degree Dc, it is possible to compare the carbonation degrees of all the various types of steam-cured lightweight cellular concretes on the same basis.

(1) Thermal Analysis Method As the measuring apparatus of the thermal analysis method used in the present invention, a thermogravimetric analysis measuring apparatus is used so that the amount of weight loss accompanying the decomposition of calcium carbonate can be seen. For the sake of clarity, a thermogravimetric-differential thermal analyzer (TG-DTA) is desirable that allows simultaneous differential thermal analysis measurements.

As a method for analyzing the amount of carbon dioxide bound, carbon dioxide generated by combustion (for example, combustion IR spectrum method) or carbon dioxide separated by acid is quantified (for example, hydrochloric acid decomposition). Coulometry), but a thermal analysis method capable of analyzing only carbon dioxide gas in calcium carbonate is preferable.

(2) Calcium carbonate There are some calcium carbonates having different crystal structures, but when all are heated, they decompose into calcium oxide and carbon dioxide at around 600 to 900 ° C., so Tobermorite-11A in the deterioration. The amount of calcium carbonate can be quantitatively measured by a thermal analysis method regardless of the crystal form of calcium carbonate generated by the decomposition of.

(3) Chemical Analysis Chemical analysis can be carried out by any method as long as it can quantitatively measure calcium, but the ICP method which can accurately quantitatively measure calcium is preferable.

(4) Calcium content Steam curing In the manufacturing process of lightweight aerated concrete, a calcium compound that does not participate in the reaction of forming tobermorite-11A may be added as an additive. For example, calcium sulfate or the like. If the content of this calcium compound is added to the calculation of the degree of deterioration of steam-cured lightweight cellular concrete, 100% deterioration does not occur, and therefore it must be excluded from the calculation of the degree of deterioration. For calcium compounds that do not participate in the tobermorite formation reaction, the degree of deterioration can be accurately calculated by quantitatively measuring the elements that form salts by chemical analysis, converting them to the amount of calcium oxide, and subtracting from the total calcium content. it can.

Generally, steam-cured lightweight cellular concrete has Ca / Ca lower than the theoretical composition of Tobermorite-11A.
It is manufactured with a Si ratio, and it is considered that all the calcium components are contained in Tobermorite-11A except the calcium component in the gypsum added to the raw materials for autoclave curing. Therefore, as shown in the first embodiment, the amount of carbon dioxide gas that chemically binds to the calcium component in tobermorite-11A to become calcium carbonate is quantitatively measured to obtain the carbonation degree, which is referred to as the deterioration degree. The method of doing is a rational and suitable method. However, as shown in the second aspect, the effect of adding calcium carbonate to the raw material and the effect of chemically bonding the semi-plastic material before curing the autoclave with carbon dioxide gas are eliminated, and the calcium content of the carbon dioxide gas is It is desirable to limit the binding of the above after autoclave curing.

Further, it is not known so far how much of the calcium content contained in tobermorite-11A is decomposed into calcium carbonate when carbonized tobermorite-11A under various conditions. . That is, it is not known whether or not the amount of carbon dioxide gas obtained by chemically binding carbon dioxide gas to the calcium component contained in tobermorite-11A and saturating the bond can be uniquely determined.

In addition, since the raw materials and compositions of steam-cured lightweight cellular concrete produced all over the world are various, the chemical compositions are also various.

Therefore, it is considered that the total amount of calcium quantitatively measured by the chemical analysis can be calcium carbonate, and the total amount of calcium at the time of maximum carbonation is defined as Cmax, which is the calcium oxide equivalent amount, and the calcium content other than tobermorite is removed. A calcium oxide equivalent C0 obtained by quantitatively measuring the calcium carbonate content of the uncarbonated sample and a calcium oxide equivalent Cs obtained by quantitatively analyzing the elemental components that make up the calcium compound of the additive are calculated as calcium oxide of the total calcium of the test sample. It is desirable to subtract from the converted amount Cmax.

(Example) [Example 1] As a test sample,
The degree of deterioration of steam-cured lightweight cellular concrete that had been used for buildings for 10 years was analyzed by chemical analysis and thermal analysis. Further, it was confirmed by a powder X-ray diffraction method whether or not there was a calcium compound which is an inhibitory component for the quantitative evaluation of the degree of deterioration.

The total calcium content quantitatively measured by chemical analysis was 18.00% by weight, and 25.20% by weight which was 56/40 times the molecular weight ratio was the calcium oxide equivalent Cma.
x.

On the other hand, in the thermal analysis method, calcium carbonate is decomposed by a thermogravimetric-differential thermal analyzer, and the amount of weight loss due to carbon dioxide gas generated is quantitatively measured. Since this amount of weight loss is the amount of carbon dioxide gas, when a weight loss of 7.0% by weight occurs, it is 8.9% by weight, which is 56/44 times the molecular weight ratio.
Is the calcium oxide equivalent C of calcium carbonate estimated to be caused by the decomposition of tobermorite.

Calcium oxide equivalent Cm of total calcium
35.3% calculated as the ratio of the calcium oxide conversion amount C (8.9% by weight) of calcium carbonate to ax (25.20% by weight) was the carbonation degree of the test sample of this Example, that is, Degree of deterioration.

[Example 2] As a sample to be tested, calcium sulfate (anhydrous salt, hemihydrate, dihydrate) was added in the manufacturing process, and steam-cured lightweight aerated concrete used in a building 10 years old The deterioration degree was analyzed by chemical analysis and thermal analysis. Further, it was confirmed by a powder X-ray diffraction method whether or not there was a calcium compound which is an inhibitory component for the quantitative evaluation of the degree of deterioration.

The total calcium quantitatively measured by chemical analysis was 18.00% by weight, which was 56/40 times the molecular weight ratio.
5.20% by weight becomes the calcium oxide equivalent Cmax of the total calcium. In addition, quantitatively measured sulfur is 0.5
At 0% by weight, 0.88% by weight, which is 56/32 times the molecular weight ratio, becomes the calcium oxide equivalent Cs of calcium sulfate. Calcium oxide equivalent Cs of calcium sulfate
(0.88% by weight) was subtracted from the calcium oxide equivalent Cmax (25.20% by weight) of total calcium 2
4.32% by weight can be the amount of calcium that contributed to the tobermorite formation reaction.

On the other hand, in the thermal analysis method, calcium carbonate is decomposed by a thermogravimetric-differential thermal analyzer, and the amount of weight loss due to carbon dioxide gas generated is quantitatively measured. Since this amount of weight loss is the amount of carbon dioxide gas, when a weight loss of 7.0% by weight occurs, it is 8.9% by weight, which is 56/44 times the molecular weight ratio.
Is the calcium oxide conversion amount C of calcium carbonate, which is estimated to be generated by the deterioration of tobermorite.

Ratio of the calcium oxide equivalent amount C (8.9% by weight) of calcium carbonate estimated to be produced by the deterioration of tobermorite to the amount of calcium (24.32% by weight) that contributed to the tobermorite formation reaction. 36.6% calculated as is the carbonation degree of the test sample of this example, that is, the deterioration degree.

[Example 3] As a test sample, the degree of deterioration of steam-cured lightweight aerated concrete, which had been used for a building 10 years after calcium carbonate was added in the manufacturing process, was analyzed by chemical analysis and thermal analysis. analyzed. In this case, an undegraded sample prepared with the same composition was used as a non-carbonated sample (standard sample) and analyzed in the same manner. Further, it was confirmed by a powder X-ray diffraction method whether or not there was a calcium compound which is an inhibitory component for the quantitative evaluation of the degree of deterioration.

The total calcium quantitatively measured by chemical analysis was 18.00% by weight, which was 56/40 times the molecular weight ratio.
5.20% by weight becomes the calcium oxide equivalent Cmax of the total calcium.

On the other hand, in the thermal analysis method, calcium carbonate is decomposed by a thermogravimetric-differential thermal analyzer, and the amount of weight loss due to carbon dioxide gas generated is quantitatively measured. In the test sample,
A weight loss of 7.0% by weight occurs, which is due to a molecular weight ratio of 56.
The value of 8.9% by weight obtained by multiplying by 44 is the calcium oxide conversion amount C of calcium carbonate in the test sample.

Further, in the uncarbonated sample (standard sample), a weight loss of 1.0% by weight occurs, and 1.3% by weight, which is 56/44 times the molecular weight ratio, becomes 1.3% by weight in the uncarbonated sample (standard sample). It becomes the calcium oxide equivalent amount Co of calcium carbonate in the standard sample).

Therefore, from the calcium oxide conversion amount C (8.9% by weight) of calcium carbonate in the test sample, the calcium oxide conversion amount Co (1.3% by weight) of calcium carbonate other than tobermorite in the uncarbonated sample was calculated. It is found that the calcium oxide conversion amount of calcium carbonate generated by the decomposition of tobermorite-11A is 7.6% by weight.

Calcium oxide equivalent Cm of total calcium
The ax (25.20% by weight) minus the calcium oxide equivalent amount Co (1.3% by weight) of calcium carbonate in the uncarbonated sample was 23.90% by weight, whereas the decomposition of tobermorite-11A occurred. 31.8% calculated as the ratio of the calcium oxide equivalent amount of calcium carbonate (7.6% by weight) is the degree of carbonation of the test sample of this example, that is, the degree of deterioration.

[Example 4] As a test sample, calcium sulfate (anhydrous salt, hemihydrate, dihydrate) was added in the manufacturing process, and steam-cured lightweight aerated concrete that had been used for a building 10 years ago Deterioration degree was analyzed by chemical analysis and thermal analysis. In this case, an undegraded sample prepared with the same composition was used as a non-carbonated sample (standard sample) and analyzed in the same manner. Further, it was confirmed by a powder X-ray diffraction method whether or not there was a calcium compound which is an inhibitory component for the quantitative evaluation of the degree of deterioration.

The total calcium quantitatively measured by chemical analysis was 18.00% by weight, which was 56/40 times the molecular weight ratio.
5.20% by weight becomes the calcium oxide equivalent Cmax of the total calcium. In addition, quantitatively measured sulfur is 0.5
At 0% by weight, 0.88% by weight, which is 56/32 times the molecular weight ratio, becomes the calcium oxide equivalent Cs of calcium sulfate. Calcium oxide equivalent Cs of calcium sulfate
(0.88% by weight) was subtracted from the calcium oxide equivalent Cmax (25.20% by weight) of total calcium 2
4.32% by weight can be the amount of calcium that contributed to the tobermorite formation reaction.

On the other hand, in the thermal analysis method, calcium carbonate is decomposed by a thermogravimetric-differential thermal analyzer, and the amount of weight loss due to carbon dioxide gas generated is quantitatively measured. In the test sample,
A weight loss of 7.0% by weight occurs, which is due to a molecular weight ratio of 56.
The value of 8.9% by weight obtained by multiplying by 44 is the calcium oxide conversion amount C of calcium carbonate in the test sample.

Further, in the uncarbonated sample (standard sample), a weight loss of 1.0% by weight occurs, and 1.3% by weight, which is 56/44 times of the molecular weight ratio, becomes 1.3% by weight in the uncarbonated sample (standard sample). It becomes a calcium oxide equivalent amount Co of calcium carbonate that is not related to tobermorite in the standard sample).

Therefore, by subtracting the calcium oxide conversion amount Co (1.3% by weight) of calcium carbonate in the uncarbonated sample from the calcium oxide conversion amount C (8.9% by weight) of calcium carbonate in the test sample. It can be seen that the calcium carbonate equivalent amount of calcium carbonate generated by the decomposition of tobermorite-11A is 7.6% by weight.

23. From the calcium oxide equivalent of calcium (24.32% by weight) that contributed to the tobermorite formation reaction, the calcium oxide equivalent Co (1.3% by weight) of calcium carbonate in the uncarbonated sample was subtracted. 0
33.0% calculated as a ratio of calcium oxide conversion amount (7.6% by weight) of calcium carbonate generated by decomposition of tobermorite-11A to 2% by weight is carbonation of the test sample of this example. Degree, that is, the degree of deterioration.

Various values relating to the calculation of the carbonation degree, that is, the deterioration degree Dc by the method of the present invention performed in Examples 1 to 4 are shown in Table 1.
Are shown together. In Examples 1 and 2, calcium carbonate was not substantially contained in the samples before deterioration.

[0055]

[Table 1]

[Example 5] As a test sample, a steam-cured lightweight aerated concrete that had been used in a building immediately after production and 5, 9, 22, 26, 31, 33 years had passed was subjected to chemical analysis and thermal analysis. The analysis method was used to calculate the deterioration degree Dc according to the method of the present invention. Moreover, it was confirmed by a powder X-ray diffraction method that there is no calcium compound that is an inhibitory component for the quantitative evaluation of the degree of deterioration. The results are shown in Table 2.

[0057]

[Table 2]

From Table 2, the degree of deterioration increases with the lapse of years, but the deterioration does not progress even after 22 years or more. That is, it can be seen that the degree of deterioration does not rise above a certain level. This is in good agreement with the result of actual visual evaluation.

As described above, it can be understood that there is a common change in the deterioration degree with respect to the elapsed years even among different samples.

[Example 6] As the sample, a lightweight cellular concrete block manufactured at the Sumitomo Metal Mining Co., Ltd. Siporex Yokohama factory was used. 40 x 80 x 1 for each sample
It was molded into 0 mm and accelerated carbonization was carried out under conditions of 20 ° C., relative humidity of 90% and carbon dioxide gas concentration of 3% by volume for 10, 20 and 100 days, respectively. Each accelerated carbonated sample and uncarbonated sample were pretreated at 105 ° C. for 2 hours before quantitative measurement of the amount of calcium carbonate and total calcium content.

Thermogravimetric-differential thermal analyzer (TG-DTA)
In the analysis of the amount of carbon dioxide gas (% by weight), the temperature rising rate was 20 ° C./min and the measurement temperature range was from room temperature to 100 ° C. in a nitrogen flow. The amount of weight loss at 900 ° C. was defined as the carbon dioxide amount (% by weight).

The carbonation degree Dc calculated based on this is 5
From around 0%, a crack was generated on the surface of the sample, and it was confirmed that the sample was suitable for quantitative evaluation of deterioration.

[Comparative Example 1] Since it was considered that the measurement of the carbon dioxide gas amount was different depending on the analysis method, the carbon dioxide gas amounts (wt%) of the four kinds of samples similar to those in Example 6 were measured by the combustion IR spectrum method. Was analyzed by.

The carbon contained in the sample was heated in air, and the desorbed carbon dioxide gas was measured by the infrared absorption method and quantified from the absorption peak intensity.

[Comparative Example 2] Since it was considered that the measurement of the carbon dioxide gas amount was different depending on the analysis method, the carbon dioxide gas amounts (% by weight) of four kinds of samples similar to those in Example 6 were analyzed by hydrochloric acid decomposition coulometry. analyzed. That is, carbon dioxide gas generated by decomposing a sample with hydrochloric acid is absorbed in a solution having a known pH.

As a result, the shifted pH was returned to the original pH by electrolysis, and the amount of carbon was quantitatively measured from the required amount of electric power and converted into the amount of carbon dioxide.

Table 3 shows the measurement results of the carbon dioxide gas amount in Example 6 and Comparative Examples 1 and 2, and the calculation results of the carbonation degree by the method of the present invention using the measurement results of Example 6. In Example 6, the amount of carbon dioxide gas (% by weight) is smaller than that in Comparative Examples 1 and 2. The reason for this is considered as follows.

Thermogravimetric-differential thermal analyzer (TG-DTA)
Then, the decomposition temperature of calcium carbonate is 600 to 900.
The amount of weight loss at ° C is quantitatively measured as the amount of carbon dioxide gas.

On the other hand, in Comparative Examples 1 and 2, the amount of all carbon dioxide gas in the sample is quantitatively measured by combustion or decomposition with hydrochloric acid. Therefore, it is considered that quantitative measurement was performed including the amount of carbon dioxide gas bound to impurities other than calcium carbonate, such as magnesium carbonate, sodium carbonate, and potassium carbonate, and the amount of carbon dioxide gas adsorbed on the sample surface.

Therefore, the TG-DTA equipped with a gas analyzer was used to analyze the thermogravimetric change and the evolved gas of the sample which had been subjected to accelerated carbonation for 100 days. As a result, carbon dioxide begins to desorb at 200 ° C, which corresponds to the decomposition of calcium carbonate at 780 ° C.
There is a peak at 750-790 ° C, which has a top at 5
A shoulder was seen near 50 ° C.

In addition to calcium, alkali metals such as magnesium, sodium and potassium, and alkaline earth metals are mixed in silica stone and cement which are raw materials for steam curing light-weight cellular concrete. Of these carbonates, the ones that decompose when heated are calcium carbonate and magnesium carbonate, and the decomposition temperature for pure substances is 1 atm.
And 898 ° C and 540 ° C. Therefore, 750-79
The peak at 0 ° C is considered to correspond to the decomposition of calcium carbonate and the shoulder near 550 ° C corresponds to the decomposition of magnesium carbonate.

It is considered that the carbon dioxide gas desorbed from around 200 ° C. is the carbon dioxide gas adsorbed on the sample surface. Further, from the study of the present inventor, it is known that the specific surface area of steam-cured lightweight aerated concrete is increased by accelerated carbonation, and the progress of accelerated carbonation increases the adsorption amount of carbon dioxide gas, and the adsorbed carbon dioxide is absorbed. It is highly possible that the gas was desorbed from around 200 ° C.

From the above, the method of quantitatively measuring the total amount of carbon dioxide as an analysis method of the amount of carbon dioxide is not suitable from the viewpoint of evaluating the carbonation degree, and is 600 to 900 ° C.
A suitable method is to find the amount of weight loss corresponding to the decomposition peak of calcium carbonate.

[0074]

[Table 3]

As described above, according to the carbonation degree calculated from the carbon dioxide binding amount by the thermogravimetric-differential thermal analyzer (TG-DTA) and the calcium content by the chemical analysis, all kinds of lightweight cellular concrete can be obtained. , It is possible to compare and consider using the carbonation degree as the same evaluation scale.

[0076]

EFFECTS OF THE INVENTION When steam-cured lightweight aerated concrete is used as a building material, the content of calcium carbonate produced by decomposing tobermorite-11A, which is a component that is deteriorated by the atmosphere, is quantitatively measured, and thus tobermorite-11A is obtained. You can see the resolution of. Therefore, according to the method of the present invention, the deterioration of steam-cured lightweight cellular concrete can be quantitatively evaluated and judged.

Furthermore, it is no longer necessary to remove the finishing layer to visually check for cracks in the steam-cured lightweight cellular concrete, and to remove the steam-cured lightweight cellular concrete panel to measure the bending strength. Has a very remarkable effect that the deterioration degree can be quantitatively evaluated quickly and easily.

Further, the carbonation evaluation of all kinds of lightweight cellular concrete can be performed with the same standard. By applying the method of the present invention to each research result, organically combining and studying many research results, it is possible to develop the carbonation and durability of steam-cured lightweight aerated concrete and apply it to products. Becomes

Continuation of front page (56) Reference JP-A-5-52840 (JP, A) JP-A-3-100460 (JP, A) JP-A-57-77962 (JP, A) JP-A-7-20097 (JP , A) JP 11-352123 (JP, A) JP 10-267920 (JP, A) JP 6-331532 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB) Name) G01N 33/38

Claims (5)

(57) [Claims] 1. A calcium oxide conversion amount C of calcium carbonate obtained by quantitatively measuring a calcium carbonate content by a thermal analysis method for a test sample of steam-cured lightweight cellular concrete,
C / Cm is calculated from the total amount of calcium oxide, Cmax, obtained by quantitatively measuring the total calcium content by chemical analysis.
A method for quantitatively evaluating the degree of deterioration of steam-cured lightweight cellular concrete, which comprises quantitatively evaluating the degree of deterioration of the test sample by the carbonation degree Dc1 (%) of the formula ax × 100. 2. Calcium oxide, calcium hydroxide, used in the manufacturing process of steam-cured lightweight cellular concrete,
The degree of deterioration of the steam-cured lightweight cellular concrete according to claim 1, wherein the amount of calcium used in the cement is calculated by converting the amount of calcium used into the amount of calcium oxide to obtain a calcium oxide conversion amount Cmax of the total calcium. Quantitative evaluation method. 3. A calcium oxide conversion amount C of calcium carbonate obtained by quantitatively measuring a calcium carbonate content by a thermal analysis method for a test sample of steam-cured lightweight cellular concrete.
(% By weight) and the total calcium content obtained by quantitatively measuring the total calcium content by the total amount of calcium oxide equivalent to Cma
x (wt%), and a calcium oxide equivalent Cs (wt%) of calcium sulfate obtained by quantitatively measuring the total sulfur content,
For an uncarbonated sample produced by the same production method as the above sample, the calcium carbonate equivalent amount C0 (% by weight) of calcium carbonate obtained by quantitatively measuring the calcium carbonate content by a thermal analysis method was obtained, and (C- C0) / (Cmax-Cs-C
0) × 100 The degree of carbonation Dc2 (%) is used to quantitatively evaluate the degree of deterioration of the test sample, and a method for quantitatively evaluating the degree of deterioration of steam-cured lightweight cellular concrete. 4. The thermal analysis method for quantitatively measuring calcium carbonate content uses a thermogravimetric-differential thermal analyzer (TG-DTA), and the weight loss of carbon dioxide gas corresponding to an endothermic peak at 600 ° C. to 900 ° C. The method for quantitatively evaluating the degree of deterioration of steam-cured lightweight cellular concrete according to any one of claims 1 to 3, wherein 5. The deterioration degree quantitative evaluation of steam-cured lightweight cellular concrete according to claim 1, wherein the test sample having a carbonation degree of 50% or more is diagnosed as having deteriorated durability. Method.