JPH09268084A - Production of lightweight foamed concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing ALC(aerated lightweight concrete) excellent in appearance and quality by reducing voids produced in the circumference of rein forcing steel for reinforcing the interior of aerated lightweight concrete. SOLUTION: A blend amount and quality of a raw material of green slurry for pouring into a formwork in which reinforcing steel is arranged, especially quicklime are controlled. Thereby yield value of the green slurry is controlled to <=120Pa until expansion due to reaction of a foaming agent is finished and expansion and shrinkage of green slurry after expansion due to reaction of the foaming agent is finished or green body produced by hardening of the green slurry are suppressed to <=3.0%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam-cured lightweight cellular concrete (hereinafter referred to as AL) used for an outer wall of a building or the like.
C)).

[0002]

2. Description of the Related Art Conventionally, in the general manufacturing method of ALC,
After setting the reinforcing bars in advance at a predetermined position in the mold, silica sand, quick lime, cement, gypsum, and a mixture of repetitive raw materials, and further added and mixed with aluminum powder as a foaming agent, the green slurry, in the above mold Inject. And
After the slurry foamed in the mold hardens into a green body, the green body is cut into a predetermined size with a piano wire, and then steam-cured in an autoclave to produce an ALC.

The blending amount of the above ALC raw material varies depending on the manufacturer, but silica sand is 35 to 60% by weight, and quick lime is 4%.
~ 20 wt%, cement 5-35 wt%, gypsum 0
It is general that 10% by weight and 5 to 40% by weight of the repeating raw material are blended, and 0.06 to 0.07% by weight of aluminum powder as a foaming agent is blended to the powder raw material. Is. Repeated raw materials are crushed green bodies that occur when cutting with a piano wire or ALC after steam curing.
It is a finely pulverized product such as defective product.

[0004]

However, in the above-mentioned conventional ALC manufacturing method, cavities are generated in the green slurry and the green body around the reinforcing bars, which remain until after steam curing. It was a big problem in terms of quality such as appearance and strength. Also,
The cavities left in the ALC contributed to the deterioration of the yield of ALC products.

In view of the above conventional circumstances, the present invention is
It is an object of the present invention to provide a method for producing ALC having excellent appearance and quality by reducing voids generated around reinforcing reinforcing bars inside LC.

[0006]

In order to achieve the above-mentioned object, the ALC manufacturing method provided by the present invention is such that a green slurry of lightweight cellular concrete is injected into a mold in which reinforcing reinforcing bars are arranged and foamed. In the method for producing lightweight cellular concrete to be cured, the yield value of the green slurry is adjusted to 120 Pa or less until the expansion due to the reaction of the foaming agent is completed, and the green slurry after the expansion due to the reaction of the foaming agent is completed or the hardening thereof. It is characterized in that the expansion and contraction of the green body generated by the above is suppressed to 3.0% or less.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The main cause of the formation of cavities around reinforcing bars in an ALC is that the yield value of the green slurry is large while the green slurry expands due to the reaction of a foaming agent such as aluminum powder. It is considered that this is because it rises and becomes difficult to be plastically deformed, and after the expansion due to the reaction of the foaming agent such as aluminum powder ends, the green slurry and the green body further expand or contract.

The present inventors can suppress the increase in the yield value of the green slurry while the green slurry is expanding due to the reaction of the foaming agent by appropriately controlling the blending amount of the raw materials and the quality thereof, and It was found that the expansion and contraction of the green slurry and the green body after the completion of expansion due to the reaction of the foaming agent can be suppressed, and the generation of cavities is much less than in the conventional AL.
The present invention relates to a method for producing C.

The increase in the yield value during the expansion of the green slurry due to the reaction of the foaming agent such as aluminum powder is mainly due to the hydration reaction of quicklime and the repeated agglomeration and water absorption of the raw material. The formation of bubbles due to the reaction and impurities such as clay minerals contained in silica sand also influence. That is, when the blending amount of quick lime or repeated raw materials is increased, when the blending amount of a foaming agent such as aluminum powder is increased with respect to the amount of green slurry, or when a large amount of impurities such as clay minerals are mixed in silica sand. It was found that the yield value of the green slurry increased.

Due to these causes, the yield value of the green slurry during expansion due to the reaction of the foaming agent is 120 P.
When it exceeds a, the green slurry becomes difficult to be plastically deformed, so that the cavity at the upper part of the reinforcing rebar generated during expansion is not filled with the green slurry or the filling is delayed, so that the cavity remains around the reinforcing bar. It will be easier. Therefore, in the method of the present invention, the yield value of the green slurry is adjusted to 120 Pa or less, preferably in the range of 1 to 100 Pa until the expansion due to the reaction of the foaming agent is completed.

In general, the expansion of the green slurry due to foaming of aluminum powder or the like starts immediately after the green slurry is injected into the mold and ends 10 to 30 minutes after the injection. After that, the green slurry hardens due to the hydration reaction of quicklime and cement in the green slurry,
During the transition to the green body due to this curing, the temperature increase due to the heat of hydration reaction causes thermal expansion of the green slurry or the green body, which further increases the internal pressure. Then, with the passage of time, the internal pressure is relaxed and the fine structure is collapsed, so that the green body is contracted.

Therefore, in the expansion and contraction of the green slurry and the green body after the expansion due to the reaction of the foaming agent is completed, there are many parts where the respective factors overlap each other,
If the expansion is large after the reaction of the foaming agent such as aluminum powder is completed, the contraction is large, and conversely, if the expansion is small, the contraction is small.

In particular, it has been found that it is mainly quicklime that causes the green slurry and green body to expand and contract. If you increase the amount of quicklime,
The temperature increase due to the hydration reaction is large, so that the thermal expansion is large and the subsequent contraction is also large.

Further, in terms of quality of quick lime, when hard baked quick lime is used, its hydration reaction is slow, so that the hydration reaction with water becomes intense after the transfer to the green body, and the behavior of expansion and contraction. Grows very large. The hard-baked quick lime is quick lime burned at a high temperature of about 1350 ° C. when lime is produced, and the test method therefor is a drop amount of 4N-HCl for 10 minutes by the quick lime coarse-grain titration method. Two
It is said that it is quick lime of 0 to 250 cc or less.

When the expansion and contraction after the reaction of the foaming agent such as aluminum powder as described above is so large as to exceed 3.0%, the green slurry or green body may exceed 500 Pa during this period. It has been found that in a situation where the yield strength is extremely large, a relative movement is caused between the reinforcing bar and the reinforcing bar, which tends to leave a cavity around the reinforcing bar. Therefore, in the method of the present invention, the expansion and contraction of the green slurry or green body after the reaction of the foaming agent is completed is 3.0.
Adjust to less than%.

In the method of the present invention, the yield value of the green slurry until the expansion due to the reaction of the foaming agent is completed is adjusted to 120 Pa or less as described above, and the green slurry or the green body after the reaction of the foaming agent is completed. The expansion and contraction of lime are suppressed to 3.0% or less, but these can be controlled by adjusting the blending amount of the raw materials, particularly the blending amount of the quick lime and the repeated raw material, and particularly controlling the quality of the quick lime.

That is, the silica sand 35 which is generally used in the past
~ 60 wt%, quicklime 4-20 wt%, cement 5-3
5% by weight, gypsum 0-10% by weight, repeated raw material 5-40
% By weight, and a foaming agent in proportion to these powder raw materials of 0.
In the present invention, in order to suppress the hydration reaction of quicklime and water absorption due to repeated raw materials, the compounding amount of both is decreased, and the hydration reaction is delayed in terms of quality, in contrast to the compounding amount of 06 to 0.07% by weight. It is necessary not to use hard-baked quicklime that causes expansion due to.

More specifically, it is preferable that the content of quick lime is 10% by weight or less and the content of repetitive raw materials is 20% by weight or less. If the compounding amount of either quicklime or repeated raw materials exceeds the above range, the yield value of the green slurry exceeds 120 Pa, or the expansion and contraction exceeds 3.0%, and ALC with few voids can be obtained. Disappear. Further, the amount of the foaming agent such as aluminum powder to be blended should not exceed 0.07% by weight for the same reason. Further, it is preferable to avoid the use of silica sand containing a large amount of impurities such as clay minerals.

[0019]

EXAMPLES ALCs according to the present invention will be described below based on examples.
The manufacturing method will be specifically described. Powder raw materials such as silica sand, quick lime, cement, gypsum, and repeated raw materials were blended for each sample, and aluminum powder was added and mixed as a foaming agent. Table 1 below shows the total amount of the powder raw materials in each sample and the blending amount of aluminum mixed with the powder raw materials. Further, the water-solid ratio of the green slurry was set to 0.66 (constant) for all the samples.

[0020]

[Table 1] ALC raw material content (% by weight) Sample Quartz sand quicklime cement Gypsum Repeated raw material Al powder Raw material Quality Special notes 1 46 3 30 7 14 0.05 None 2 55 7 30 8 0 0.06 None 3 49 3 26 7 15 0.06 None 4 * 46 15 24 5 10 0.06 None 5 * 41 6 22 6 35 0.06 None 6 * 48 6 26 6 14 0.08 None 7 * 48 6 26 6 14 0.06 A lot of clay in silica sand 8 * 48 6 26 6 14 0.06 Hard baking Use of quick lime (Note) Samples marked with * in the table are comparative examples.

Each of the obtained green slurries was poured into a mold provided with reinforcing bars, and the slurry foamed in the mold hardened into a green body, which was then cut into a predetermined size with a piano wire. ALC panels were manufactured by steam curing in an autoclave. still,
The green slurry temperature at the time of pouring the mold was set to 48 ° C. (constant) in all the samples.

In the manufacturing process of the above ALC panel,
The change with time of the yield value of each green slurry was measured with a Rheoset viscometer manufactured by Brookfield Company, and the maximum value until the expansion of the green slurry due to the reaction of the aluminum powder was completed was obtained. In addition, the height of the upper surface of the green slurry and the green body in the mold is measured over time,
The height after the reaction of the aluminum powder was calculated as 100, and the expansion rate and the contraction rate were obtained.

Further, after steam curing by an autoclave,
Eighteen panels for each sample extracted from a predetermined position in each form were cut at predetermined five positions, and the generation of cavities around the reinforcing bars was confirmed. The results are summarized in Table 2 below. The state of cavities in the ALC panel was shown by the average value of the cavities generated in the upper part of the reinforcing bars in the vertical direction of the mold.

[0024]

[Table 2] (Note) Samples marked with * in the table are comparative examples.

As can be seen from the above results, in sample 1, the yield value of the green slurry was suppressed to 100 Pa or less by adjusting the reduction amounts of the quicklime, the repeated raw material, and the aluminum powder, and the quicklime and the repeated raw material were mixed in the yield value. Since the amount was reduced, there was no expansion or contraction after the completion of the aluminum powder reaction, and no void was generated in the ALC panel.

In Sample 2, the green slurry yield value was further reduced because the raw materials were not blended repeatedly, but since the blending amount of quicklime was larger than in Sample 1, expansion and contraction occurred, and some cavities were formed inside the panel. Occurred. Also,
In Sample Example 3, the yield value of the green slurry increased because the blending amount of the starting material and the aluminum powder was slightly larger than that of Sample 1, but the shrinkage was very large due to the large expansion due to the reduction amount of the quicklime mixture being adjusted. It's small, and the cavities inside the panel are quite small.

In sample 4 which is a comparative example, the yield value of the green slurry is large and the expansion and contraction are also very large because the amount of quicklime is particularly large, and a very large cavity is generated inside the panel. did. In Sample 5, since the blending amount of the raw material was repeatedly increased, the yield value of the green slurry became very large and a large void was generated in the panel. Further, in sample 6, since the blending amount of aluminum powder was increased, the yield value of the green slurry was increased, and again a large void was generated.

In sample 7, since the silica sand used as the powder raw material contained a large amount of viscous minerals as impurities, the yield value of the green slurry was greatly increased and a slightly large void was generated. Further, in sample 8, since the hard-baked quicklime was used, the hydration reaction by quicklime became active after the foaming reaction of the aluminum powder was completed, and the large expansion and contraction of the green slurry and the green body became very large, and the inside of the panel was extremely damaged. There was a large cavity in the.

[0029]

According to the present invention, the yield value of the green slurry is controlled to 120 Pa or less until the expansion due to the reaction of the foaming agent is controlled by controlling and adjusting the blending amount of the raw materials and the quality thereof, and By suppressing the expansion and contraction of the green slurry or green body after the expansion due to the reaction to 3.0% or less, the cavities generated around the reinforcing bars are eliminated or reduced, and the appearance and quality are lightweight. Aerated concrete can be produced.

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Claims (2)

[Claims] 1. A method for producing a lightweight cellular concrete in which a green slurry of lightweight cellular concrete is injected into a formwork provided with reinforcing reinforcing bars to foam and cure,
The yield value of the green slurry is adjusted to 120 Pa or less until the expansion due to the reaction of the foaming agent is completed, and the expansion and contraction of the green slurry after the expansion due to the reaction of the foaming agent is completed or the green body produced by the curing thereof is 3 or less. A method for producing lightweight cellular concrete, which is characterized by suppressing the content to 0.0% or less. 2. Hard baked lime is not used as the quick lime in the lightweight cellular concrete raw material, and the quick lime content is 10.
The method for producing a lightweight cellular concrete according to claim 1, wherein the content of the repeating raw material is 20% by weight or less, and the compounding amount of the repeating raw material is 20% by weight or less.