JP2007171125A - Deterioration history determination method for light-weight cellular concrete - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a deterioration hysteresis determination method for a light-weight cellular concrete (ALC) capable of determining, totally and in detail, the durability of the ALC that has been used over the years. <P>SOLUTION: Steam adsorption isotherms in adsorption and desorption are acquired as to one part collected from the ALC, and the levels of hysteresis in the obtained steam adsorption isotherms serve as a deterioration history in the ALC. This method determines that the ALC, of which the hysteresis (1-Wa/Wd) in the steam adsorption isotherm obtained, based on an equilibrium moisture content Wa at 0.6 of the relative pressure in the adsorption, and based on an equilibrium moisture content Wd at 0.6 of the relative pressure in desorption, is 0.1 or larger, as having gone through a moderate deterioration history, and determines that the ALC of which the hysteresis (1-Wa/Wd) to be 0.075 or smaller, as having gone through an abrupt deterioration history. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a degradation history determination method for lightweight cellular concrete, and more particularly, to a degradation history determination method for lightweight cellular concrete (ALC) panels used for walls, roofs, floors, and the like of buildings.

  ALC is mainly composed of siliceous raw materials such as silica and calcareous raw materials such as cement and quick lime, and additives such as water and aluminum powder are added to these fine powders to form a slurry, followed by the reaction of the aluminum powder. It is manufactured by carrying out high-temperature and high-pressure steam curing with an autoclave after foaming, semi-curing by reaction of the calcareous raw material, forming to a predetermined dimension. Further, reinforcing bars are arranged in advance on the ALC panel, which contributes to maintaining the strength of the ALC panel. ALC panels are light in weight and excellent in fire resistance, heat insulation and workability, and thus are widely used as building materials.

  Since ALC panels are sufficiently steam-cured, they are inherently highly durable. However, the long-term durability of several decades is the most important issue for reaction and decomposition with carbon dioxide in the air. It is carbonation deterioration by. Carbonation degradation can cause degradation phenomena such as cracks, deflection, shrinkage or reduced strength in the ALC panel. These deterioration phenomena cannot be visually confirmed because they are hidden under the finish applied to a normal ALC panel. For this reason, as described in Japanese Patent No. 3451616, Japanese Patent No. 3451617, and Japanese Patent No. 3478160, the present inventors have collected a small amount of sample and obtained a carbonic acid which is a chemical analysis method. A diagnostic method using the degree of conversion as an index is proposed. However, the carbonation degree alone was not sufficient.

Japanese Patent No. 3451616

Japanese Patent No. 3451617

Japanese Patent No. 3478160

  An object of the present invention is to provide an ALC deterioration history determination method capable of comprehensively and specifically determining the durability of an ALC panel used over time.

  In one aspect of the method for judging deterioration history of lightweight aerated concrete according to the present invention, a portion collected from the lightweight aerated concrete is obtained with a water vapor adsorption isotherm at the time of adsorption and desorption, and the water vapor adsorption isotherm obtained. Let the magnitude | size of the hysteresis which a line has be a deterioration log | history in the said lightweight cellular concrete.

  In a different aspect of the degradation history judgment method for lightweight aerated concrete of the present invention, a water vapor adsorption isotherm at the time of adsorption and desorption is obtained for a part collected from the lightweight aerated concrete, and a relative pressure of 0.6 is obtained. A lightweight aerated concrete having a water vapor adsorption isotherm (1-Wa / Wd) of not less than 0.1 obtained by the equilibrium moisture content Wa during adsorption Wa and the equilibrium moisture content Wd during desorption at a relative pressure of 0.6, It is determined that a mild deterioration history has passed, and the lightweight cellular concrete having the hysteresis (1-Wa / Wd) of 0.075 or less is determined to have passed a rapid deterioration history.

  In a different aspect of the degradation history judgment method for light-weight aerated concrete of the present invention, the pore diameter distribution is measured by nitrogen adsorption for a part collected from the lightweight aerated concrete, and the pore diameter is 0.5 nm to 5 nm. The peak of the pores is defined as the deterioration history of the lightweight cellular concrete.

  In a different aspect of the degradation history judgment method for light-weight aerated concrete of the present invention, the pore diameter distribution is measured by nitrogen adsorption for a part collected from the lightweight aerated concrete, and the pore diameter is 0.5 nm to 5 nm. It is determined that lightweight cellular concrete having a pore peak of 0.05 ml / g or less has undergone a mild deterioration history, and lightweight cellular concrete having a pore peak of 0.08 ml / g or more has a rapid degradation history. Judge that it has passed.

  In a different aspect of the method for determining deterioration history of lightweight aerated concrete according to the present invention, the BET specific surface area obtained by measuring the BET specific surface area by nitrogen adsorption for a part collected from the lightweight aerated concrete, The deterioration history of lightweight cellular concrete.

  In a different aspect of the degradation history judgment method of lightweight cellular concrete used over time of the present invention, the BET specific surface area obtained by measuring the BET specific surface area by nitrogen adsorption for a part collected from the lightweight cellular concrete, Compared to the BET specific surface area obtained from the lightweight cellular concrete newly produced by the same method, the small lightweight cellular concrete is judged to have undergone a gradual deterioration history, and the large lightweight cellular concrete is abrupt. It is determined that the deterioration history has passed.

  According to the present invention, it is possible to determine a deterioration history from a sample obtained by collecting a part of an ALC panel that has been used over time. By adding the determination based on the degree of carbonation to the obtained deterioration history, the durability of the ALC panel used over time can be determined comprehensively and in detail.

  From the subsequent studies by the present inventors, when the carbonation deterioration gradually progresses, when passing through a slow deterioration history, the deterioration of the ALC panel as a building member is not remarkable even if the carbonation degree is high. On the contrary, it has been found that the deterioration of the ALC panel as a building member is remarkable from the stage where the degree of carbonation is low when a rapid deterioration history is caused by the rapid deterioration of carbonation. In this specification, the state in which carbonation deterioration progresses slowly means that the atmosphere is a carbon dioxide concentration of about 0.03% by volume, which is a normal carbon dioxide concentration in the air, and moisture enters the ALC panel. Do not air dry. Contrary to this, the state in which carbonation deterioration rapidly proceeds is that the atmosphere has a carbon dioxide gas concentration of 0.3% by volume or more, which is 10 times or more than the carbon dioxide concentration in normal air, Alternatively, moisture enters the ALC panel, and the moisture content of the ALC panel is 10% by mass or more.

  From the sample survey by the present inventors, as shown in Table 1, regarding the relationship between the degree of carbonation and the presence or absence of cracks on the panel surface, an ALC panel that has undergone a gradual deterioration history has a degree of carbonation exceeding 50%. It was found that the ALC panel panel, which has cracked from the initial stage and has undergone a rapid deterioration history, has already cracked at a carbonation degree of 35%. That is, it can be seen that it is necessary to determine not only the degree of carbonation but also the deterioration history in order to accurately determine the degree of carbonation deterioration of the ALC panel.

  In one aspect of the method for determining deterioration history of ALC of the present invention, for a part collected from ALC used over time, water vapor adsorption isotherms at the time of adsorption and desorption are obtained, and the hysteresis of the water vapor adsorption isotherm obtained is obtained. The size is the deterioration history in the ALC.

  Furthermore, the hysteresis (1-Wa / Wd) of the water vapor adsorption isotherm obtained by the equilibrium water content Wa during adsorption at relative pressure 0.6 and the equilibrium water content Wd during desorption at relative pressure 0.6 is 0.1 or more. It is determined that the lightweight aerated concrete has undergone a moderate deterioration history, and the lightweight aerated concrete having the hysteresis (1-Wa / Wd) of 0.075 or less is determined to have undergone a rapid deterioration history.

  For quantifying hysteresis, methods such as calculating the area of the difference between the desorption side and the adsorption side, and calculating the difference or ratio of the adsorption amount between the desorption side and the adsorption side at an arbitrary relative pressure are common. . The method of calculating the area of the difference between the desorption side and the adsorption side is not easily implemented by anyone, and is greatly influenced by the measurement conditions of how far the high pressure side is measured. On the other hand, the method of calculating the difference or ratio of the amount of adsorption between the desorption side and the adsorption side at an arbitrary relative pressure is simple, but the relative pressure to be set is important, and at a relative pressure of 0.3 or less, the hysteresis is Usually, it is not seen, and at a relative pressure of 0.8 or more, the influence of fluctuation due to measurement conditions becomes strong. Therefore, in the present invention, a method is adopted in which anyone can easily carry out and obtain from the ratio of the equilibrium water content at a relative pressure of 0.6 with little fluctuation.

  Accordingly, as a preferred embodiment, the hysteresis (1-Wa / Wd) of the water vapor adsorption isotherm obtained by the equilibrium water content Wa during adsorption at a relative pressure 0.6 and the equilibrium water content Wd during desorption at a relative pressure 0.6. Although it is quantified, the evaluation method of hysteresis is not limited to this. As described above, the ALC having a hysteresis (1-Wa / Wd) of 0.1 or more cracks from the stage where the carbonation degree exceeds 50%, and the ALC having a hysteresis degree of 0.075 or less Cracks already occur at 35%.

  In a different aspect of the ALC degradation history determination method of the present invention, the pore diameter distribution is measured by nitrogen adsorption for a part collected from the ALC that has been used over time, and the pore peak with a pore diameter of 0.5 nm to 5 nm is measured. Is the deterioration history in the ALC.

  Furthermore, ALC with a pore diameter of 0.5 nm to 5 nm having a pore peak of 0.05 ml / g or less was judged to have passed a gradual deterioration history, and ALC having a pore diameter of 0.08 ml / g or more was It is determined that a rapid deterioration history has passed.

  As described above, the ALC having a pore peak with a pore diameter of 0.5 nm to 5 nm having a pore size of 0.05 ml / g or less is cracked from the stage where the carbonation degree exceeds 50%, and is 0.08 ml / g. An ALC of g or more already cracks at a carbonation degree of 35%.

  In a different aspect of the ALC degradation history determination method of the present invention, the BET specific surface area obtained by measuring the BET specific surface area by nitrogen adsorption for a part collected from the ALC used over time, and the obtained BET specific surface area as the degradation history in the ALC. To do.

  Furthermore, the obtained BET specific surface area is smaller than the BET specific surface area obtained from the ALC newly produced by the same method, and it is determined that a small ALC has undergone a gradual deterioration history and a large ALC. Is determined to have undergone a rapid deterioration history.

  The obtained BET specific surface area is smaller than the BET specific surface area obtained from the ALC newly produced by the same method. As described above, the AET is cracked from the stage where the carbonation degree exceeds 50%. Large ALC is already cracked at a carbonation degree of 35%.

Example 1
About a part collected from the new ALC, a water vapor adsorption isotherm at the time of adsorption and desorption was obtained using a gas adsorption measurement device (BELSORP-18PLUS-T, manufactured by Bell Japan Co., Ltd.). The obtained water vapor adsorption isotherm is shown in FIG. 1 and FIG.

  From the figure, the hysteresis (1-Wa / Wd) of the water vapor adsorption isotherm obtained from the equilibrium water content Wa during adsorption at relative pressure 0.6 and the equilibrium water content Wd during desorption at relative pressure 0.6 was calculated. 0.034.

  Furthermore, the pore size distribution was measured by nitrogen adsorption using a nitrogen adsorption type pore size measuring device (Amco Corporation, Soapmatic). The obtained pore size distribution is shown in FIGS. The peak of pores having a pore diameter of 0.5 nm to 5 nm was 0.05 ml / g.

Furthermore, the BET specific surface area was measured by nitrogen adsorption using a nitrogen adsorption surface area measuring apparatus (manufactured by Amco Corporation, Soapmatic). The BET specific surface area obtained was 20.4 m ² / g. The measurement results are shown in Table 2.

(Example 2)
About the ALC panel obtained by the same manufacturing method as Example 1, the average relative humidity is about 90%, and the moisture content is 10 to 15% by mass in an atmosphere of carbon dioxide concentration (about 0.03%) in the atmosphere. For a part of the test specimen collected from the ALC panel that was allowed to stand for 6 months, in the same manner as in Example 1, water vapor adsorption isotherms during adsorption and desorption were obtained.

  When the carbonation degree was measured with reference to the aforementioned Japanese Patent No. 3451616, it was 25%. The obtained water vapor adsorption isotherm is shown in FIG. The magnitude of hysteresis calculated from FIG. 1 was 0.049.

  Further, as in Example 1, the pore size distribution was measured by nitrogen adsorption. The obtained pore size distribution is shown in FIG. The peak of pores having a pore diameter of 0.5 nm to 5 nm was 0.09 ml / g.

  Further, as in Example 1, the BET specific surface area was measured by nitrogen adsorption. The obtained BET specific surface area is shown in Table 2.

(Example 3)
For an ALC panel obtained by the same production method as in Example 1, a specimen having a moisture content of 3 to 5% by mass in an atmosphere having an average relative humidity of about 65% and a carbon dioxide gas concentration of 0.3% was obtained. For a part collected from the ALC panel left still for months, as in Example 1, water vapor adsorption isotherms during adsorption and desorption were obtained.

  When the carbonation degree was measured with reference to the aforementioned Japanese Patent No. 3451616, it was 50%. The obtained water vapor adsorption isotherm is shown in FIG. The magnitude of hysteresis calculated from FIG. 1 was 0.065.

  Further, as in Example 1, the pore size distribution was measured by nitrogen adsorption. The obtained pore size distribution is shown in FIG. The peak of pores having a pore diameter of 0.5 nm to 5 nm was 0.22 ml / g.

  Further, as in Example 1, the BET specific surface area was measured by nitrogen adsorption. The obtained BET specific surface area is shown in Table 2.

Example 4
For an ALC panel obtained by the same production method as in Example 1, a test specimen having a moisture content of 10 to 15% by mass in an atmosphere having an average relative humidity of about 90% and a carbon dioxide gas concentration of 0.3% was obtained. For a part collected from the ALC panel left still for months, as in Example 1, water vapor adsorption isotherms during adsorption and desorption were obtained.

  The degree of carbonation was measured with reference to the aforementioned Japanese Patent No. 3451616 and found to be 60%. The obtained water vapor adsorption isotherm is shown in FIG. The magnitude of the hysteresis calculated from FIG. 1 was 0.073.

  Further, as in Example 1, the pore size distribution was measured by nitrogen adsorption. The obtained pore size distribution is shown in FIG. The peak of pores having a pore diameter of 0.5 nm to 5 nm was 0.28 ml / g.

  Further, as in Example 1, the BET specific surface area was measured by nitrogen adsorption. The obtained BET specific surface area is shown in Table 2.

(Example 5)
About the ALC panel obtained by the same manufacturing method as Example 1, the average relative humidity is about 65% and the moisture content is 3 to 5% by mass in an atmosphere of carbon dioxide gas concentration (about 0.03%) in the atmosphere. For a part of the specimen collected from the ALC panel which was left standing for 10 years, the water vapor adsorption isotherm during adsorption and desorption was obtained in the same manner as in Example 1.

  The degree of carbonation was measured with reference to the aforementioned Japanese Patent No. 3451616 and found to be 30%. The obtained water vapor adsorption isotherm is shown in FIG. The magnitude of hysteresis was calculated from FIG. 2 and found to be 0.106.

  Further, as in Example 1, the pore size distribution was measured by nitrogen adsorption. The obtained pore size distribution is shown in FIG. The peak of pores having a pore diameter of 0.5 nm to 5 nm was 0.04 ml / g.

  Further, as in Example 1, the BET specific surface area was measured by nitrogen adsorption. The obtained BET specific surface area is shown in Table 2.

(Example 6)
About the ALC panel obtained by the same manufacturing method as Example 1, the average relative humidity is about 65% and the moisture content is 3 to 5% by mass in an atmosphere of carbon dioxide gas concentration (about 0.03%) in the atmosphere. The water vapor adsorption isotherm at the time of adsorption and desorption was obtained in the same manner as in Example 1 for a part of the specimen collected from the ALC panel which was left standing for 22 years.

  When the carbonation degree was measured with reference to the aforementioned Japanese Patent No. 3451616, it was 50%. The obtained water vapor adsorption isotherm is shown in FIG. The magnitude of hysteresis was calculated from FIG. 2 and found to be 0.150.

  Further, as in Example 1, the BET specific surface area was measured by nitrogen adsorption. The obtained BET specific surface area is shown in Table 2.

(Example 7)
About the ALC panel obtained by the same manufacturing method as Example 1, the average relative humidity is about 65% and the moisture content is 3 to 5% by mass in an atmosphere of carbon dioxide gas concentration (about 0.03%) in the atmosphere. For a part of the specimen collected from the ALC panel which was left standing for 30 years, the water vapor adsorption isotherm during adsorption and desorption was obtained in the same manner as in Example 1.

  The degree of carbonation was measured with reference to the aforementioned Japanese Patent No. 3451616, and it was 59%. The obtained water vapor adsorption isotherm is shown in FIG. It was 0.251 when the magnitude | size of the hysteresis was computed from FIG.

  Further, as in Example 1, the pore size distribution was measured by nitrogen adsorption. The obtained pore size distribution is shown in FIG. The peak of pores having a pore diameter of 0.5 nm to 5 nm was 0.03 ml / g.

  Further, as in Example 1, the BET specific surface area was measured by nitrogen adsorption. The obtained BET specific surface area is shown in Table 2.

  As shown in FIG. 1 and FIG. 2, the hysteresis in the water vapor adsorption isotherm is such that the equilibrium moisture content at the time of desorption is higher than that at the time of adsorption, and the relative pressure (P / Ps) closes around 0.4. Becomes smaller. In Examples 2 to 4 which are rapid deterioration histories, almost no hysteresis was observed, and in Examples 5 to 7 which were gradual deterioration histories, typical hysteresis was obtained.

  As shown in FIG. 3 and FIG. 4, in the pore diameter distribution by nitrogen adsorption, in Examples 2 to 4 which are rapid deterioration history, a remarkable peak is shown in the region where the pore diameter is 0.5 nm to 5 nm. However, in Examples 5 to 7, which have a gradual deterioration history, no peak is observed in the region where the pore diameter is 0.5 nm to 5 nm.

  As shown in Table 2, in Examples 2 to 4 which are rapid deterioration histories, the BET specific surface area is larger than in Example 1 which is a new ALC, and in Examples 5 to 7 which are gradual deterioration histories, BET specific surface area is small.

  The main minerals of ALC are tobermorite and silica and gypsum remaining from the raw material, and even if it is a new ALC, the BET specific surface area varies depending on the amount of these and the state of curing by autoclave. Moreover, it is tobermorite that a BET specific surface area changes by carbonation deterioration, and the BET specific surface area of a silica and a gypsum hardly changes. Therefore, it is not appropriate to determine the absolute value of the BET specific surface area, and the deterioration history is determined based on whether the BET specific surface area is large or small with respect to a new ALC manufactured under the same conditions.

It is a graph which shows a water vapor | steam adsorption isotherm. It is a graph which shows a water vapor | steam adsorption isotherm. It is a graph which shows pore diameter distribution by nitrogen adsorption. It is a graph which shows pore diameter distribution by nitrogen adsorption.

Claims (6)

  This is a method for judging the deterioration history of lightweight aerated concrete that has been used for many years. For some of the samples taken from the lightweight aerated concrete, obtain water vapor adsorption isotherms at the time of adsorption and desorption, and the hysteresis of the water vapor adsorption isotherm obtained. A degradation history determination method for lightweight cellular concrete, characterized in that the size is a degradation history in the lightweight cellular concrete.   Deterioration history determination method for light-weight aerated concrete used over time, obtaining water vapor adsorption isotherms during adsorption and desorption for a portion collected from the lightweight aerated concrete, and equilibrium moisture content during adsorption at a relative pressure of 0.6 The lightweight cellular concrete with a water vapor adsorption isotherm (1-Wa / Wd) of 0.1 or more obtained by the rate Wa and the equilibrium water content Wd at the time of desorption at a relative pressure of 0.6 has a moderate deterioration history. It is determined that the lightweight cellular concrete having the hysteresis (1-Wa / Wd) of 0.075 or less is determined to have undergone a rapid degradation history. .   Deterioration history determination method for light-weight aerated concrete used over time, a pore diameter distribution of a portion collected from the light-weight aerated concrete is measured by nitrogen adsorption, and the pore diameter is 0.5 nm to 5 nm. Is a deterioration history judgment method of the lightweight cellular concrete, characterized in that the degradation history of the lightweight cellular concrete is used.   Deterioration history determination method for light-weight aerated concrete used over time, a pore diameter distribution of a portion collected from the light-weight aerated concrete is measured by nitrogen adsorption, and the pore diameter is 0.5 nm to 5 nm. However, it is determined that lightweight cellular concrete having a volume of 0.05 ml / g or less has undergone a slow deterioration history, and lightweight cellular concrete having a capacity of 0.08 ml / g or greater has been determined to have undergone a rapid degradation history. Deterioration history judgment method for lightweight cellular concrete characterized by the above.   Deterioration history determination method for light-weight cellular concrete used over time, for a part collected from the lightweight cellular concrete, by measuring the BET specific surface area by nitrogen adsorption, the resulting BET specific surface area is degraded in the lightweight cellular concrete A method for judging deterioration history of lightweight cellular concrete, characterized in that it is a history.   This is a deterioration history judgment method for lightweight cellular concrete that has been used over time. For a part collected from the lightweight cellular concrete, the BET specific surface area is measured by nitrogen adsorption, and the obtained BET specific surface area is newly determined by the same method. In comparison with the BET specific surface area obtained from the lightweight aerated concrete manufactured in the above, it is determined that the small lightweight aerated concrete has undergone a gradual deterioration history, and the large lightweight aerated concrete has undergone a rapid deterioration history. A method for determining a deterioration history of lightweight cellular concrete, characterized in that: