JPH0155219B2 - - Google Patents

Description

[Detailed description of the invention]

Steam-cured lightweight aerated concrete (ALC)
In the production of silicic acid raw materials and calcareous raw materials, selection of the quality of silicic acid raw materials and calcareous raw materials is important to ensure the physical properties of finished products. Particularly in the case of silicic acid raw materials, those with a high alkali content are currently not used as they are considered inappropriate. The present invention relates to a method for producing ALC using a silicic acid raw material with a high alkali content, which has not been used in the past. ALC is made by mixing silicic acid raw materials such as crushed silica sand and silica stone, and calcareous raw materials such as lime and cement with water in an appropriate ratio, adding metal powder such as aluminum, and stirring. Alternatively, it is manufactured by incorporating air bubbles by blowing air into it, semi-curing it, and then transferring it to an autoclave and curing it with high-temperature, high-pressure steam. In order to ensure that the ALC produced in this way has the physical performance necessary as a building material, the selection of the main raw materials is important. In particular, the quality of silica sand and silica stone as silicic acid raw materials greatly influences the material quality of ALC. In the production of calcium silicate hydrate in the hydrothermal reaction known as the basic reaction in ALC production, Na ₂ It is generally said that a necessary condition is to use a silicic acid raw material with a low alkali content such as O and K ₂ O of 0.5% by weight or less based on the total silicic acid raw material. Therefore, there have been no examples of using a silicic acid raw material with a high alkaline content as a main raw material for ALC. Examples of silica sand with a high alkali content include polishing waste sand (Na ₂ O + K ₂ O, 1% by weight or more) generated from the polishing process of glass manufacturing plants, and mountain sand containing feldspar (Na ₂ O + K ₂ O, 1% by weight). % or more). In ALC manufactured by using silica sand and silica stone with high alkali content as silicic acid raw materials together with calcareous raw materials such as quicklime and cement, the normal hydrothermal reaction in the autoclave is inhibited. In other words, fine particles in crushed silica sand and silica stone gel early in the slurry with a high alkali content, react with lime in a relatively low temperature range, and form a large amount of gelled calcium silicate. Produces hydrates. Therefore, it is thought that the homogeneous production of highly crystalline calcium silicate hydrate due to the normal hydrothermal reaction within the autoclave is partially inhibited. As a result, this phenomenon hinders the development of mechanical strength of the product, increases the wet-dry shrinkage rate, and deteriorates the physical properties. As explained above, the present invention uses silica sand and silica stone with a high alkali content, which have been considered unsuitable as raw materials for ALC in the past, and has the same compressive strength and wet-dry shrinkage rate as conventional ALC products. etc.
The purpose is to provide a method for manufacturing ALC. In order to achieve this objective, the inventors of the present application have proposed that when using silicic acid raw materials such as silica sand and silica stone in which the content of alkali metal oxides is 0.5% by weight or more in all silicic acid raw materials, In order to alleviate the above-mentioned phenomenon that inhibits the production of good calcium silicate hydrate when mixing calcareous raw materials such as cement and powdered quicklime, which are conventionally used in 8 in main ingredients
It has been experimentally found that satisfactory results can be obtained by adding dihydrate gypsum to contain ~16% by weight calcium sulfate. The mixing ratio of the silicic acid raw material and the calcareous raw material used here may be the same as in the conventional method, and the amount of gypsum in the newly added dihydrate is 8 to 16% by weight of CaSO4 _.
The reason why this is added is because, as shown in the examples, if the amount is outside this range, the compressive strength will decrease whether the amount added is too small or too large. The present invention will be explained in detail below. In the production of ALC, it is known to add calcium sulphate in the form of gypsum hemihydrate or gypsum dihydrate to the raw material mixture. Calcium sulfate helps control the digestion of powdered quicklime, thus preventing the formation of cracks and cavities in the ALC caused by premature lime digestion. It is also known that the use of calcium sulfate in certain areas increases physical mechanical strength. For example, according to Japanese Patent Publication No. 47-15359, in the production of steam-cured gas concrete containing 1 part of pulverized lime and 3 parts of cement, compression is achieved by adding 2.5 to 3.5% by weight of calcium sulfate as SO ₃ to the mortar mixture. Strength is increased by 30-50%. The present inventors also disclosed in Japanese Patent Publication No. 55-27030 that calcium sulfate is contained in an amount of 6.5 to 12% by weight in a mixture of calcareous raw materials and silicate raw materials with a weight ratio of cement to lime of 1:0.5 to 3.5. It is proposed that the addition of dihydrate gypsum increases compressive strength by approximately 52-65%. By further increasing the calcium sulfate content as described above, the present invention enables polishing waste sand and feldspar that have a high alkali (Na ₂ O + K ₂ O) content, which until now has been considered unusable as an ALC raw material. We have established a method for manufacturing ALC equivalent to conventional products using silica sand containing . The polishing waste sand is a mixture of glass powder and silica sand used as a polishing agent for glass during the manufacture of polished glass plates, and has been discarded until now. The composition of this waste sand and mountain sand containing feldspar is, for example, as shown in Table 1, with a considerably high alkaline content.

[Table] In addition, the particle size of polishing waste sand is 10 μ or less 40.0, 10 ~
20μ25.0, 20~30μ15.0, 30~40μ15.0, 40μ or more 5.0
Each weight% is extremely fine powder. In order to obtain a product with high compressive strength by adding calcium sulfate to a combination of these silicic acid raw materials exhibiting a high alkali content, powdered quicklime, and cement, the calcium sulfate content of the raw material mixture must be 8 to 8.
It must be regulated within a range of 16% by weight. The form of calcium sulfate added to ALC raw materials is dihydrate, which hydrates extremely slowly, rather than α- and β-type hemihydrate gypsum and type anhydrite, which react with water to cause a rapid hydration reaction and solidify. It needs to be plaster. The method of the present invention can be operated in the same manner as the conventional method, except that an appropriate amount of calcium sulfate is included. According to the method of the present invention, it is possible to obtain a product that has an appropriate bulk specific gravity, high compressive strength, and satisfactorily satisfies other mechanical strength and physical properties. Examples will be described below. Example 1 The weight ratio of 45 to 60% by weight of the polishing waste sand shown in Table 1, powdered quicklime and Portland cement (containing 3.3% by weight of CaSO ₄ ) was 1 to 0.3 to 8.35 to 45 0 to 21.8% by weight based on the total solid content of the mixture with calcareous raw materials (no loss on ignition)
After adding gypsum dihydrate and curing with steam at high temperature and pressure (180℃, 10.5Kg/cm ² ) according to the normal procedure, ALC was performed.
was manufactured, and the compressive strength (Kgf/cm ² ) of the product was measured according to JIS A-5416-7. The results are shown in Table 2.

【table】

[Table] As is clear from Table 2, even when the weight ratio of powdered quicklime to cement is in a wide range of 1:0.3 to 8, calcium sulfate is contained in the total solid content in an amount of 8 to 16% by weight. The compressive strength of the products to which dihydrate gypsum was added increased by about 44 to 50% compared to the case without the addition (Experiment Nos. 1, 8, 11, and 14), and the calcium sulfate content was outside the range of the present invention. (Experiment No. 2, 3,
7, 9, 12, 15), the compressive strength increased by about 20 to 35%. Example 2 Mountain sand containing 49-55% by weight of the feldspar shown in Table 1, about 9-10% by weight of powdered quicklime, and 31-35% by weight of Portland cement (containing 3.3% by weight of CaSO ₄ ). 7.3 internally based on the total solids in the mixture;
Adding 10.9% by weight of dihydrate gypsum, Example 1 below
The compressive strength of the product was measured in the same manner. The results are shown in Table 3.

[Table] From Table 3, when comparing Experiment No. 18 using the method of the present invention and Experiment No. 19 using the method of the present invention, the compressive strength increased by about 24%, and when compared with the case without additives, it increased by about 52%.
There was a clear difference in the increase, and the product produced by the method of the present invention was comparable to conventional ALC, which had improved physical and mechanical properties. Example 3 25% by weight of polishing waste sand shown in Table 1 and 24% by weight
mixture with silica powder (Na ₂ O + K ₂ O 1.10% by weight)
ALC was manufactured and tested in the same manner as in Example 1 by adding 11% by weight of dihydrate gypsum as an additive to 20% by weight of powdered quicklime and 20% by weight of Portland cement. As a result, the bulk specific gravity (g/cm ² ) was 0.50 and the compressive strength (Kgf/cm ² ) was 53. With the present invention, high alkali-containing waste polishing sand and feldspar-containing mountain sand, which were conventionally discarded, can now be used in large quantities as the main raw materials for ALC.
It will also result in significant cost reduction.

Claims (1)

[Claims] 1 A siliceous raw material containing 0.5% by weight or more of an alkali metal oxide in a totally silicic raw material consisting of one or more of silica sand, silica stone, or polishing waste sand, and a calcareous raw material consisting of lime and cement. Steam-cured lightweight foam, which is used as a raw material and is characterized by adding dihydrate gypsum so that the total solid content of the main raw material contains 8 to 16% by weight of calcium sulfate, and curing with high-temperature and high-pressure steam. Concrete manufacturing method.