JPH0118034B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in the manufacturing method of steam-cured lightweight cellular concrete (hereinafter abbreviated as ALC). ALC is made by mixing siliceous raw materials such as silica sand and silica stone and calcareous raw materials such as lime and cement with water in an appropriate ratio, then adding metal powder such as aluminum and stirring, or mixing air. After containing air bubbles by a method such as
It is manufactured by solidifying and semi-hardening, transferring it to an autoclave, and curing it with high temperature and high pressure steam. The ALC produced in this way must have physical properties that allow it to be used as a building material. As a means of improving the physical performance of ALC, in the past we have added approximately 0.5% by weight of alkali hydroxide to the total solid content of the slurry of the silicic raw material, which is the main component of ALC, and the calcareous raw material consisting of lime and cement. Attempts have been made to adjust foaming so that the slurry generates normal bubbles by adding . However, although the addition of this alkali was certainly effective in controlling foaming, it ended up worsening the wet-drying shrinkage rate of the product. From this result, the main raw materials Ca and SiO ₂ are
Since the ratio of CaO/SiO ₂ = 0.4 to 0.8 is preferable, it is important to know whether the alkaline content (Na ₂ O + 0.658K ₂ O) contained in the silicic raw material, which is used in large quantities, will affect the physical performance of ALC. After conducting a study to determine whether or not this was the case, we found that the presence of alkali in excess of a predetermined amount reduces the strength of ALC. Today, the alkaline content in silicic raw materials is already 1
It is known to use up to 0.5% by weight, preferably up to 0.5% by weight. However, as mentioned above, even if the ratio of CaO/SiO ₂ and the alkali content in the silicate raw material are regulated, the compressive strength and wet-dry shrinkage rate are still insufficient, so at present, the crystallization of calcium silicate hydrate is For improvement, mineral alumina substances such as carrion, granulated blast furnace slag, etc. are added in an amount of about 2 to 4% by weight based on the total solids of the raw material. Although the addition of kaolin and the like improves the compressive strength, etc., it has the disadvantage that the bubbles become disordered during the foaming stage, which increases the water absorption rate of the product, which also increases the cost. There is a point. This is probably due to the fact that kaolin and other materials are difficult to obtain. In addition, in order to improve the compressive strength of ALC, (1) add calcium sulfate to the mortar mixture as SO ₃ to
(2) Method for producing ALC by adding 6.5 to 12% by weight of calcium sulfate to the main raw material mixture (Japanese Patent Publication No. 15359/1983), (2) Method for producing ALC by adding 6.5 to 12% by weight of calcium sulfate to the main raw material mixture (Japanese Patent Publication No. 15359/1983). There are proposals such as the following. However, according to various studies conducted by the applicant of the present invention, the above two methods also have problems such as the increase in raw material constituent substances, which makes their management complicated in actual operation. The present invention is an ALC manufacturing method that does not cause bubble disturbance during foaming, is easy to manage in actual operation, and in particular can reduce the wet-dry shrinkage rate compared to conventional methods, and improves both the compressive strength and overall water absorption rate. The challenge is to provide the following. In order to achieve this goal, the alkaline content (contained as Na ₂ SO ₄ or K ₂ SO ₄ ) in cement that was shipped from cement manufacturers without any indication of its content
We focused on changes in alkali content and compressive strength,
As a result of investigating the relationship with wet-dry shrinkage rate, etc., it was found that when cement with an alkali content of more than 1.2% by weight was used, the compressive strength and wet-dry shrinkage were lower than when using cement with a lower alkali content. It was found that the dry shrinkage rate etc. were not good. However, most commercially available cements have an alkali content of about 1% by weight or more.
The reason for this is that most of the alkaline content in cement comes from the clay that is the raw material for cement, but there are few clay raw materials with low alkaline content, and if you try to use clay raw materials with low alkaline content, the price of cement will be high. This is to become. However, in order to provide high quality ALC,
The present invention aims to solve the problem by manufacturing ALC using a siliceous raw material with an alkali content of 0.5% by weight or less and at the same time using cement with an alkali content of 0.8% by weight or less. According to the present invention, compressive strength, wet-dry shrinkage rate,
It becomes possible to reliably provide ALC with improved overall water absorption rate than before. Furthermore, according to the present invention, it is possible to sufficiently improve compressive strength, wet-dry shrinkage, etc. without adding kaolin, etc., so there are advantages such as cost reduction and no side effects that occur when using additives. can get. Example 55 parts by weight of finely ground silica (alkali content (Na ₂ O + 0.658K ₂ O) 0.15% by weight), 10 parts by weight of powdered quicklime, and 35 parts by weight of ordinary Portland cement with varying alkali content. and to 100 parts by weight of this mixture, 60 parts by weight of water, 0.07 parts by weight of metal aluminum powder, 1.0 parts by weight of calcined gypsum as a setting regulator, and 0.02 parts by weight of a foaming stabilizer, High temperature and high pressure steam curing (180℃, 10Kgf/cm ² ) according to the method of
ALC was manufactured and its compressive strength, wet-dry shrinkage rate, and overall water absorption rate were investigated. The results are shown in the following table for comparison with ALC produced by adding 2.1 parts by weight (2% by weight) of finely powdered kaolin to 100 parts by weight of the solid content of the above mixture.

【table】

[Table] As can be seen by comparing the compressive strength, wet-dry shrinkage rate, and overall water absorption rate between the comparative example in the table above and the present invention, the manufacturing method of the present invention has a higher compressive strength, wet-dry shrinkage rate, and wet-dry shrinkage rate than the conventional method. ALC with improved reproducibility in water absorption rate and overall water absorption rate
can be provided.

Claims (1)

[Claims] 1. In the manufacturing method of steam-cured lightweight cellular concrete using powdered silica stone or silica sand with an alkali content of 0.5% by weight or less as a siliceous raw material and cement as a calcareous raw material, or cement and calcareous powder as the main raw materials, the alkali content A method for producing steam-cured lightweight aerated concrete characterized by using 0.8% by weight or less of cement.