JPH11352123A - Judgement method of cause of generation of defect on alc - Google Patents

Abstract

PROBLEM TO BE SOLVED: To judge the cause of generation of a defect part by observing the defect part generated after autoclave curing of light-weight gas concrete (ALC), its broken face and a broken face obtained by breaking a normal part, and comparing the number of microcracks in both broken faces. SOLUTION: Whether an overload is added to a defect part in its green body stage or not can be judged by comparing a number of microcracks in a specific field of view of a broken face of the defect part and that of a broken face obtained by breaking a normal part adjacent to the defect part. Whereby the cause of the generation of the defect part generated after the curing autoclave of ALC can be judged. Any conventional means can be used in the observation of the microcracks, but an optical observation means such as a scanning electron microscope or the like can be preferably used. In a case when the shearing strain is added to the first and second stages, the cleavage strength after the curing is almost same degree as the non-load, and the impairing of the strength can not be found. On the other hand, when the shearing strain is added to the third stage, the cleavage strength after the curing is considerably impaired.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the occurrence of defects such as chips and cracks occurring after autoclave curing in steam-cured lightweight cellular concrete (hereinafter referred to as "ALC") used for the outer walls of buildings. It relates to a determination method.

[0002]

2. Description of the Related Art The applicant of the present invention has proposed Japanese Patent Application No. Hei 9-87564 as a method for specifying the time of occurrence of a defective portion that occurs in an ALC during the manufacturing process of the ALC. This identification method is called ALC
Observe the fracture surface of the fracture surface by an optical microscope etc. after the end of the manufacturing process, and if a curved surface state is detected in the matrix part of the fracture surface, the stage from the time of casting the green slurry to the end of the expansion of the green body, the matrix part When the plate-like crystal state of tobermorite is detected, the stage from the end of the expansion of the green body to before the autoclave curing, and the stage after the autoclave curing when the dense microcrystalline state is detected in the matrix part. Classification and identification have been made, and measures have been taken for defective parts with reference to this.

However, when an overload is applied to the green body at the stage of the green body, a defective portion is not generated, but a minute destruction occurs inside the green body, and a matrix portion as shown in FIG. It is conceivable that microcracks are generated in such air bubbles, and that the microcracks cause a decrease in strength after autoclaving and lead to defects such as chips and cracks after autoclaving.

In this case, since the fractured surface of the defect is observed in a dense structure state of fine crystals in the matrix portion as in the above-described stage, it is determined that the defect has occurred in the process after the autoclave curing. . However, the cause of this defective portion is the overload in the green body stage, and the cause of the occurrence of the defective portion cannot be accurately grasped, and there has been a problem that it is difficult to take effective measures. Therefore, it is necessary to establish a method for determining the cause of the occurrence of a defective portion occurring after the autoclave curing, but there is no particular method for determining the cause of the occurrence of such a defective portion, and this determination method has been required. .

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to
It is an object of the present invention to provide a method for determining the cause of a defective portion occurring after autoclaving so that measures against defective portions occurring after the autoclaving of C can be effectively taken.

[0006]

According to the present invention, there is provided a method for judging the cause of a defect occurring in an ALC according to the present invention.
In this method, the defect portion, the fracture surface generated after the autoclaving, and the fracture surface that damaged the normal portion are observed, and the number of micro cracks generated in both fracture surfaces is compared.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Tobermorite, which is a main mineral constituting ALC, is composed of calcium-rich calcium silicate hydrate (hereinafter referred to as "CSH") and silicate ions dissolved from raw silica, which are autoclaved. It is produced by a hydration reaction in water. In addition, silicate ions are dissolved in water, and in the dissolved state, they react with CSH to generate tobermorite, so that crystal growth of tobermorite occurs in the presence of water. The crystal of tobermorite is a plate-like crystal, and the size of the crystal grows from several μm to several tens μm when it is large. Therefore, a certain space for crystal growth is required.

The manufacturing process of ALC is performed by injecting a green slurry into a mold, expanding a green slurry by foaming aluminum powder, transferring the green slurry to a green body by setting the green slurry, curing the green body, and curing the green body. It is roughly divided into molding, autoclave curing, final processing, and product inspection. Here, the above-mentioned green slurry is a slurry produced by stirring powder raw material, aluminum powder as a foaming agent, and water. The green slurries condense and migrate to the green body due to the hydration reaction of the powdered raw lime and the cement, and are further cured to the extent that molding with a piano wire is possible to obtain a semi-plastic material.

[0009] Among the defects such as chips and cracks generated in the ALC during the production process of the ALC, the matrix portion of the fractured surface (actual portion which is not a bubble due to foaming of aluminum powder)
Although there is water, plate-like crystals do not grow because there is not enough space necessary for the growth of tobermorite crystals by autoclaving, and a large number of fine tobermorite crystals are formed to form a very dense structure. When such a very fine structure is observed, the time of occurrence of the defective portion is specified to be after the autoclave curing.

[0010] The determination method according to the present invention is performed by comparing the number of generated microcracks in the fractured surface of the defective portion of the ALC identified as having occurred after the autoclave curing with the fractured surface in which the normal portion has been damaged. It is a feature.

Since microcracks have water and space necessary for the growth of tobermorite, plate crystals of tobermorite crystals are found on the microcrack surfaces. However, air bubbles, voids,
Unlike traces such as residual silica, the morphology is mainly linear (lip-like), plate-like tobermorite crystals grow perpendicular to the microcrack plane, and tobermorite from the base. The feature is that almost no growth of the plate-like crystal of the crystal is observed.
m, and some long ones extend several hundred μm into the bubbles. This microcrack may occur due to thermal distortion or the like even if no overload is applied at the stage of the green body, so that it is necessary to compare the microcrack with a normal part.

That is, by comparing the number of micro-cracks occurring in a fixed field of view in the fractured surface of the defective portion and the fractured surface in which the normal portion adjacent to the defective portion has been damaged, the defective portion is overwhelmed at the green body stage. It can be determined whether or not a load is applied (if overload is applied at the stage of the green body, it is considered that the occurrence of microcracks is increasing). By utilizing this fact, it is possible to determine the cause of the occurrence of the defective portion which occurs after the autoclave curing of the ALC, and as a result, a countermeasure is effectively taken. It should be noted that known means can be used to observe the microcracks, but it is preferable to use an optical observation means such as a scanning electron microscope. It is desirable to use a frozen fractured surface artificially produced from the inside of the fractured surface where the normal part was damaged.

[0013]

Embodiments of the present invention will be described below. In Examples of the present invention, production of a green body, application of shear strain to the green body, autoclave curing of the green body subjected to the shear strain, splitting strength test of the semi-plastic subjected to the shear strain in the green body stage ,
A test including a process of observing microcracks by a scanning electron microscope (hereinafter, referred to as “SEM”) was performed. The details of each step are shown below.

Preparation of Green Body A general ALC raw material is blended to prepare a green slurry, and the green slurry is poured into a plastic container (10 × 10 × 20 cm) supported by a dedicated iron formwork. The green body was obtained by allowing the mold to stand together with the mold in a thermostatic oven capable of controlling the temperature for 4.5 hours. At this time, as for the temperature of the thermo-hygrostat, the temperatures of the green slurry and the green body in the actual operation are measured with time in advance, and the temperature is controlled up to 4.5 hours after the injection according to the temperature.
On the other hand, the humidity was set to the saturation humidity.

Load of Shear Strain on Green Body After pre-cultivation for 4.5 hours, the green body was taken out together with the iron mold from the thermo-hygrostat, and the plastic container was peeled off to make the green body a 10 cm cube (aluminum) The direction of foaming [height direction] was reduced. Next, a special shearing jig fixed to the autograph is 10cm.
The half of the green body which was made into a cube was fixed, and the other half was loaded on the autograph, and the shear strain was applied to the green body in four stages including no load until near the breaking point. Loading rate of shear strain by autograph is 0.5
mm / min, and the loading direction was two directions: a direction perpendicular to the foaming direction of the green body (that is, a direction parallel to the green body) and a direction perpendicular to the foaming direction (that is, a direction perpendicular to the green body).

Autoclave curing of green body loaded with shear strain The green body loaded with shear strain was cured in an operating autoclave to prepare a semi-plastic.

Cleavage strength test of semi-plastic with shear strain applied in green body stage Semi-plastic with shear strain applied in green body stage
It was placed in a dryer set to 0 ° C. and dried for 24 hours. After drying, a split strength test was performed by the autograph using a special jig, and a decrease in strength after autoclaving was confirmed. The loading direction of the split strength test was the same as the shear strain loading direction at the stage of the semi-plastic, and the upper and lower sides of the shear surface were sandwiched and loaded with round steel, and the breaking strength was measured.

Observation of Microcracks by SEM As a section sample for SEM observation, first, a prism was cut out from the loading surface side of the ALC on the side loaded at the semi-plastic stage.
This was impregnated with water and frozen at about −50 ° C. for several hours to form a frozen fractured surface from the inside of the fractured fractured surface, which was vacuum-dried to obtain a section sample for SEM observation. Observation of microcracks was performed using a 100-fold image (approximately 1.17 mm ² ) as one visual field, and 6 visual fields were selected at random for one section sample.
The inside of the magnified image was observed at a magnification of 1500 times or more, and the number of generated microcracks was examined. Observation of microcracks by SEM was performed in three samples for all four stages including no load.
Samples that broke at the stage of the green body were excluded from SEM observation.

FIGS. 1 and 2 show the results of a split strength test after curing in an autoclave. According to FIG.
In the case of adding up to the second stage and the second stage, the splitting strength after the autoclave curing was almost the same as that of no load, and no decrease in the strength was observed. On the other hand, when the shear strain was applied to the third stage, the splitting strength after the autoclave curing was remarkably reduced as compared with no load, and in some cases, the splitting occurred at the green body stage (a sample having a splitting strength after the autoclave curing of 0).

FIG. 3 shows the result of observation of microcracks by SEM. As shown in FIG. 3, when the shear strain applied in the green body stage increases, the number of generated microcracks also tends to increase, and in the third stage in which the splitting strength after autoclave curing was reduced was significantly increased. Therefore, if the number of generated microcracks is measured and compared with the number of microcracks in the fractured surface where the normal part is damaged, the presence or absence of overload is found, and countermeasures can be taken with reference to this.

[0021]

As described above, by using the method for judging the cause of the occurrence of a defective portion generated in an ALC according to the present invention, measures for a defective portion such as a chip or a crack generated after autoclave curing can be effectively taken. , ALC yield can be improved.

[Brief description of the drawings]

FIG. 1 is a graph showing the results of a split strength test after curing in an autoclave (loading direction of shear strain at the stage of a green body: perpendicular to the foaming direction).

FIG. 2 is a graph showing the results of a splitting strength test after curing in an autoclave (loading direction of shear strain at the stage of green body: vertical direction in foaming direction).

FIG. 3 is a graph showing observation results of microcracks by a scanning electron microscope.

FIG. 4 is a photograph showing the particle structure of a matrix portion where a microcrack has occurred, using a scanning electron microscope (× 1000).

FIG. 5 is a photograph showing a particle structure of a bubble portion where a microcrack has occurred, by a scanning electron microscope (× 1000).

Claims (1)

[Claims] 1. A defect which occurs in ALC,
Observing the defect, fractured surface, and the fractured surface that damaged the normal part that occurred after the LC autoclave curing, and comparing the number of microcracks that occurred in both fractured surfaces, the ALC was generated. For determining the cause of the occurrence of defective parts.