JPH0152356B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing lightweight cellular concrete rich in closed cells. The lightweight aerated concrete referred to in the present invention is generally
It is called ALC, and is prepared by adding finely pulverized silicic acid raw materials, calcareous raw materials, and various additives as necessary so that the molar ratio of CaO and SiO ₂ is 0.8 or less (hereinafter referred to as ALC). A suitable amount of water and aluminum metal powder are added to the mixture (the mixture is called a blended raw material) and kneaded to form a slurry. This slurry is poured into a mold and foamed and solidified. Once it has reached a certain degree of hardness, it is shaped into the specified dimensions. Bulk specific gravity 0.45 cut and steam-cured at high temperature and pressure in an autoclave
~0.55. Silica stone, silica sand, fly ash, blast furnace slag, etc. are used as silicic raw materials, quicklime, slaked lime, etc. are used as calcareous raw materials, and various inorganic materials such as ordinary Portland cement are used as other additives. cement is used. ALC with the above-mentioned bulk specific gravity is effectively used for building exterior walls due to its heat insulating properties, but
When trying to improve the insulation properties of ALC and use it for various purposes, it is necessary to use ALC containing a larger amount of air bubbles.
ALC, i.e. having a bulk specific gravity of 0.45 or less
ALC must be manufactured. Therefore, as a method for manufacturing ALC containing a large amount of bubbles, the first possible method is to increase the amount of aluminum metal powder added to the conventional blended raw materials, or to add a large amount of kneading water to the blended raw materials. However, in the former method, an excessive amount of air bubbles are generated, and the air bubbles coalesce or defoam and float to the surface of the slurry of mixed raw materials, resulting in a weak strength of the resulting aerated concrete. , it becomes heterogeneous. In addition, in the latter method, the viscosity of the slurry of the mixed raw materials decreases too much, causing phenomena of solid-liquid separation and defoaming, making it impossible to produce aerated concrete. Therefore, the present inventor added an appropriate amount of water to the blended raw materials, kneaded them, added aluminum metal powder and kneaded them to create a slurry, poured this slurry into a mold, and placed the mold together with the slurry in a pressure reducer. We have conducted various research on methods of placing slurry in a vacuum container, foaming it, and solidifying it under specific conditions, and found that when the slurry is solidified under reduced pressure, the foamed gas is almost uniformly distributed within the lightweight concrete, which is created as closed cells. , and discovered that by adjusting the viscosity of the mixed raw material slurry, adjusting the amount of aluminum metal powder, the viscosity of the slurry, and the degree of vacuum, it was possible to create various products with different bulk specific gravity in which closed cells were uniformly distributed in concrete. did.
Bulk specific gravity here refers to the specific gravity of a product dried at a temperature of 100°C until it reaches a constant weight. The "bulk specific gravity" described below was measured using the same method as above. Next, the experimental results will be explained. Experimental example 1 Silica stone 60 with a fineness of 2800 cm ² /g (Blaine value)
Kg, 88 micron Mix 10 Kg of quicklime with 10% sieve residue and 30 Kg of ordinary Portland cement.
The molar ratio of CaO and SiO ₂ is 0.52), 70% of water is added to 100kg of this mixture, and after kneading for 1 minute, 62g of aluminum metal powder is added and kneaded for another 1 minute to reduce the viscosity.
Manufactured a 500cps (B type viscometer). After pouring this slurry separately into three molds with a volume of 300, each was placed in a pressure reducer, and after removing the air in the pressure reducer, the inside was (1)-100, (2)-400, (3) The pressure was reduced to 600 mmHg to foam and solidify. Next, this solidified material was taken out and put into an autoclave and cured at 180℃ for 15 hours.The resulting lightweight aerated concrete was dried at 100℃ until it reached a constant weight, the bulk specific gravity was determined, and the compressive strength was measured. The results shown in Table 1 below were obtained. Here, compressive strength is the strength measured until the moisture content in the product reaches 10%.
This refers to the strength when dried at 70℃. The compressive strength described below was also measured using the same method as above. For comparison, the same amount of water and aluminum metal powder as above were added to the same blended raw materials as above and kneaded, put into the same mold as above, foamed and solidified under normal pressure, and the solidified product was the same as above. The results of autoclave curing under these conditions are also listed in Table 1.

[Table] From the above experimental results, when the slurry viscosity of the mixed raw material (500 cps) and the amount of aluminum metal powder added are constant, the larger the degree of pressure reduction of the pressure reducer, the larger the diameter of the bubbles in the lightweight cellular concrete obtained. , and it was observed that all the generated bubbles had an independent spherical shape. Moreover, even if the amount of aluminum metal powder added is reduced, lightweight cellular concrete with a bulk specific gravity of about 0.45 can be obtained by reducing the pressure to about -350 mmHg. Note that even if the pressure is reduced to about -100 mmHg, lightweight aerated concrete with a bulk specific gravity greater than 0.45 can be obtained as with the conventional technology, but the generated air bubbles are uniformly distributed within the lightweight concrete, so the compressive strength is It was recognized that a great product could be obtained. On the other hand, when lightweight aerated concrete is made by foaming the raw material slurry in the atmosphere and then treating it in an autoclave, the air bubbles contained in the concrete are often irregular and have horizontal cracks, resulting in a high bulk specific gravity. It was also observed that the compressive strength was comparatively low. Experimental Example 2 Using raw materials with the same fineness as those used in Experimental Example 1, 70 kg of silica sand, 13 kg of quicklime, and 17 kg of ordinary Portland cement were mixed (CaO and
The molar ratio of _SiO2 is 0.38), and water is
After kneading for 1 minute, 40 g and 120 g of aluminum metal powder were added and kneading for another 1 minute to prepare a slurry (viscosity 1500 cps). This slurry was separately injected into 6 molds each having a volume of 300 ml and placed in a pressure reducer to remove the air inside the mold.
-400 for (4), -500 for (5), -600 mmHg for (6), and -50 for (7), -100 for (8), and (9) for the sample. ), the pressure was reduced to -300 mmHg to foam and solidify. Next, this coagulated material was taken out and placed in an autoclave, both at 180℃.
After curing for 15 hours, the resulting lightweight cellular concrete was dried at 100°C until it had a constant weight, and its bulk specific gravity and compressive strength were measured, and the results shown in Table 2 below were obtained. For comparison, the same amount of water and aluminum metal powder as above were added and kneaded to the same blended raw materials as above, put into the same mold as above, foamed and solidified under normal pressure, and then the solidified material was mixed as above. The results of autoclave curing under the same conditions as above are also listed in Table 2 as comparative examples.

[Table] From the above experimental results, the slurry viscosity of the blended raw material is
When keeping the rate constant at 1600 cps and varying the amount of aluminum metal powder added, products with uniformly dispersed closed cells in lightweight cellular concrete were obtained in all cases.
The degree of reduced pressure for foaming the slurry can be reduced as the amount of aluminum metal powder added increases, and as in Experimental Example 1, as the degree of reduced pressure increases, the bulk specific gravity becomes smaller. Admitted. Experimental Example 3 Using raw materials with the same particle size as those used in Experimental Example 1, 55 kg of silica sand, 30 kg of quicklime, and 15 kg of ordinary Portland cement were mixed (CaO and
The molar ratio of _SiO2 is 0.78), and water is
75 was added and kneaded for 1 minute, then 55 g of aluminum metal powder was added and kneaded for another 1 minute to prepare a slurry (viscosity 360 cps). This slurry has a volume of 300
Inject it into the formwork, put it in a pressure reducer with the formwork,
After removing the air inside the vessel, the internal pressure of the vessel was reduced to -400 mmHg to allow foaming and solidification. Next, this solidified material was taken out and placed in an autoclave, and after curing at 180℃ for 15 hours, the resulting lightweight aerated concrete was
Dry at 100℃ until constant weight, determine bulk specific gravity,
The compressive strength was also measured and the results shown in Table 3 below were obtained. For comparison, the same amount of water and aluminum metal powder as above were added and kneaded to the same blended raw materials as above, put into the same mold as above, foamed and solidified under normal pressure, and then the solidified material was mixed as above. Products obtained by autoclave curing under the same conditions as (conventional method products) are also listed in Table 3.

[Table] From this result, if you want to obtain a product with the same bulk specific gravity as lightweight cellular concrete obtained by the conventional method, use approximately 1/2 the amount of aluminum metal powder in the conventional method, reduce the pressure of the slurry to -400 mmHg, and foam it. It is recognized that it can be obtained by curing in an autoclave as in the conventional method after solidification. Moreover, according to the method of the present invention, the air bubbles in the lightweight cellular concrete obtained were well aligned with a size of about 2 to 3 mm, and the compressive strength was high, whereas the air bubbles in the lightweight cellular concrete obtained by the conventional method were irregular and were broken and coalesced. It was found that the compressive strength was also lower than that made by the present invention. The above experimental examples all illustrate the case where aluminum metal powder is used as the foaming agent, but almost the same results as above can be obtained when metal powder other than aluminum metal, such as zinc or barium, is used. It was done. The present invention is based on these findings, and
For 100 parts by weight of raw materials for producing lightweight cellular concrete consisting of calcareous raw materials and silicic raw materials with a molar ratio of CaO to SiO ₂ in the range of 0.3 to 0.8, and cement.
A water slurry mixed with metal powder in a proportion of 0.03 to 0.15 parts by weight is adjusted to a viscosity range of 300 to 1600 cps,
This water slurry is heated to a reduced pressure of -50 to -600 in the mold.
Foaming and solidification under reduced pressure of mmHg,
The method for producing lightweight cellular concrete rich in closed cells is characterized in that the obtained coagulated material is then cured in an autoclave to produce lightweight cellular concrete with a bulk specific gravity of 0.45 or less. In the present invention, the siliceous raw materials are powders such as silica sand, silica stone, fly ash, and blast furnace slag with a particle size of 30% or less remaining on the 88μ sieve, and the calcareous raw materials are quicklime, slaked lime, etc. having a particle size of 88μ and 30% or less remaining on the sieve. Powder with a content of less than 10%, and other binding materials such as Portland cement, mixed cement, and alumina cement are used. Further, as the blowing agent, there are used metal powders which generate hydrogen when reacting with an alkaline aqueous solution, such as powders of aluminum metal, zinc metal, barium metal, and alloy metals of copper and aluminum. In the following method of the present invention, the amount of blowing agent added, the slurry viscosity of the raw material for preparation, and the degree of pressure reduction for the slurry are closely related to each other. However, when the viscosity of the slurry of the raw material for preparation is less than 300 cps, the solid-liquid state of the slurry is If the slurry viscosity exceeds 1600 cps, the viscosity is too high, and the air bubble density will be different between the upper and lower layers of lightweight cellular concrete. It is inappropriate to use viscous slurries. Therefore, the viscosity range of the raw material slurry used in the present invention is preferably 300 to 1,600 cps, more preferably 400 to 700 cps. Next, if the amount of foaming agent added is small, the degree of vacuum can be increased, and if it is large, the degree of vacuum can be decreased to make the desired lightweight cellular concrete product.However, from an economical point of view, the amount of foaming agent added is 100% by weight of the mixed raw material. 0.03 to 0.15 parts by weight, preferably 0.05 to 0.10 parts by weight. The reduced pressure on the slurry is preferably -50 to -600mmHg, more preferably -300 to -500mmHg.
It is Hg. Example: Silica stone 55 with a fineness of 3000 cm ² /g (Blaine value)
Blend 10 kg of quicklime with 5% residue on an 88 μ sieve and 35 kg of ordinary Portland cement (CaO in the mixed raw materials
SiO ₂ molar ratio is 0.60), water 70 for 100Kg of this formulation.
and after kneading for 1 minute, aluminum metal powder
Add 62g and knead for another minute until the viscosity is 500cps.
(Type B viscometer) slurry was made. This slurry was poured into a 300 mm mold and placed in a pressure reducer to remove the air inside the container, and then the pressure was reduced to -400 mmHg to cause foaming and solidification. Next, this coagulated body was taken out, placed in an autoclave, and cured at 180°C for 15 hours. The bulk specific gravity of the lightweight aerated concrete obtained is
0.35, the compressive strength was 42 Kg/cm ² , and the cell diameter in the product was 1.5 to 2.0 mm, all of which were closed cells.

Claims (1)

[Claims] 1. Metal powder at a ratio of 0.03 to 0.15 parts by weight based on 100 parts by weight of raw materials for producing lightweight cellular concrete consisting of calcareous raw materials and silicic raw materials with a molar ratio of CaO to SiO ₂ in the range of 0.3 to 0.8, and cement. The water slurry mixed with is adjusted to a viscosity range of 300 to 1600 cps, and this water slurry is heated to a vacuum degree of -50 to - in the mold.
A method for producing lightweight cellular concrete rich in closed cells, characterized by foaming and solidifying under reduced pressure of 600 mmHg, and then curing the obtained solidified material in an autoclave to obtain lightweight cellular concrete having a bulk specific gravity of 0.45 or less.