JPS5852025B2 - Mosquito-resistant cement or gypsum composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cement or gypsum composition that prevents rusting of metal that comes into contact with cement, gypsum, etc.

It is generally known that when cement is used for reinforced concrete or steel frame coatings, iron will corrode and rust due to salt accompanying the sand used, other rust-producing substances contained in aggregates and trace additives, etc. It is being

As a measure to prevent this corrosion, it has been proposed to add calcium nitrite to cement (Special Publication No. 42-2295
Publication No. 7).

One of the inventors of the present invention previously discovered that a mixture of calcium nitrite and calcium nitrate and basic calcium nitrite achieve this object more advantageously and filed a patent application (Japanese Patent Laid-Open No. 50-80315 and (Sho 50-160329).

However, these nitrites are soluble in water, so
When cement products, concrete products, etc. containing this substance are exposed to the wind and rain, moisture movement occurs inside the concrete, etc., and the added nitrites also leach out to the surface layer, causing the reinforcing bars inside the reinforced concrete to initially deteriorate. It was confirmed that even if rust prevention could be achieved, the rust prevention effect could not be expected in the long term.

As a method for this improvement, if sodium silicate is used in combination with an aqueous solution, the alkali will be too strong, and if added in a large amount, efflorescence will occur, which is undesirable.

The object of the present invention is to provide a cement or gypsum composition that effectively and long-term prevents rusting caused by iron material coming into contact with cement, gypsum, etc.

This invention combines nitrite and S i 02 /M20 (
However, M represents an alkali metal atom or a substituted or unsubstituted ammonium cation group.

) A rust-preventive cement or gypsum composition containing silica sol having a molar ratio of 5 to 2000.

The nitrites used in the present invention include most of the nitrites of monovalent alkali metals such as Na, alkaline earth metals such as Ca and Ml, other metals, and cations such as ammonium. Of course, it goes without saying that the nitrites are limited to those that have a rust-preventing effect.

The aforementioned mixtures of calcium nitrite and calcium nitrate and basic walsium nitrite are also preferred nitrites for use in this invention.

These nitrites are used as a powder or dissolved in water.

The silica sol used in the present invention is a sol liquid of SiO2 in which water and/or a hydrophilic organic solvent is dispersed.
2 to 60% by weight, and 5t as a sol stabilizer.
The molar ratio M of 02/M20 represents an alkali metal atom.

) containing 4 or more, preferably 5 to 2,000 alkali metal atoms, or alternatively, some or all of them are ammonia,
This sol uses guanidine, piperidine, quaternary ammonium hydroxide, etc.

Particularly effective sol stabilizers are those in which ammonia or the like is substituted for the alkali metal.

Further, finely powdered silica or silica aerogel dispersed in water has no gelling effect and is not used in the present invention.

The present inventors have discovered that when silica sol is added to a cement composition containing nitrite, not only does the rust prevention effect last dramatically, but the cement becomes extremely dense, reducing water permeability, and causing efflorescence on the surface. It has been found that it also has the additional effect of preventing

These effects are due to the fact that when cement gypsum etc. hardens with water, the silica sol simultaneously gels and forms a hard gel layer, and the nitrites dispersed or dissolved in the silica sol are fixed therein, and this silica gel layer is also used for cement gypsum. It reacts with free calcium, forming a denser and harder gel layer, which acts to stop the movement of water within this layer, and as a result prevents the elution of nitrite, and the metals in contact with it. The rust-preventing effect of this product lasts dramatically without disappearing.

As described above, excellent effects can be brought about by adding nitrite and silica sol to cement, gypsum, etc. before water hardening to form the composition of the present invention.

The composition of this invention may be prepared by any procedure as long as it contains the required amounts of silica sol and nitrite, which are essential components.

For example, in cement mortar, silica sol and nitrite can be added together with water during preparation, or nitrite powder can be added to cement in advance and silica sol can be added together with water removal to make mortar.

The content of nitrite in the composition of this invention is usually within 5% by weight based on cement, gypsum, etc., but it is It is determined by the amount of rust-producing substances inside.

The amount of silica sol is 0.1-1 per 10 parts by weight of nitrite.
000 parts by weight of 5i02 solids is preferred.

Further, the composition of the present invention may be used in combination with dispersants, thickeners, aggregates, inorganic/organic binders, setting accelerators, etc. used in general concrete, cement mortar, gypsum plaster, etc.

The most effective nitrites in the compositions of this invention are calcium nitrite, basic calcium nitrite and mixtures of calcium nitrite and calcium nitrate, and magnesium nitrite.

The reason for this is that when the silica sol gels and forms a gel layer, the cations Ca and Mg of these nitrites make it a strong gel layer that still contains nitrite ions, which allows for a long period of time. It has a remarkable anti-rust effect on steel.

Next, an experimental example will be described.

Example 1 A hardened mortar was prepared by mixing 1 kg of Portland cement, 2 kg of No. 7 silica sand, 10 kg of sodium chloride powder, and 1.6 kg of water.

Aqueous silica sol 20 containing 510,218 kg wt% and 6 wt% dimethyljetanol ammonium hydroxide
Solution 20 in which 7g of sodium nitrite was dissolved in 0g the day before.
7 g was added to the mortar described above to make the mortar composition of this invention.

This was poured into a double-barreled cement mold of 4 x 4 x 16 cm, and three iron rods whose surfaces had been previously degreased and polished with 1120 sandpaper were inserted into the center of the mortar.

On the other hand, as a comparison (Comparative Example 1), 160 g of water was used instead of 200 g of the aqueous silica sol in Example 1, and 167 g of a solution in which 7 g of sodium nitrite had been dissolved the day before was used. A test specimen was prepared in the same manner.

The mortar of the present invention method and the comparative example were demolded and installed in a Toyo Rika Sunshine Weather Meter, and after 15 days, 30 days, and 60 days, the specimen was taken out and the test specimen was broken to check the rusting of the iron rod. The results were as shown in the table below.

Furthermore, while the cement mold of the comparative example already had white efflorescence on the surface after 15 days, no efflorescence was observed on the cement mold of the present invention even after 30 days.

Example 2 1 kg of gypsum hemihydrate and 501 kg of water in advance. Calcium nitrite 20g, aqueous silica sol “Snowtex-O” (
Liquid 7009, which is a mixture of 180 g of SiO2 (20% by weight, Na200.03% by weight) (manufactured by Nissan Chemical Industries KK), was kneaded and filled into a 1801 rL paper cup, into which the same iron rod as in Example 1 was inserted.

- After being left for day and night, the test piece was removed from the paper mold and exposed outdoors for one month, and then the test piece was split to examine the rusting state of the iron rod, but no rust was found.

On the other hand, as a comparative example, 160 g of water was used instead of 20.9 g of calcium nitrite and 180 g of aqueous silica sol in Example 2.
One was treated in exactly the same manner as in Example 2, except that 180F was used (Comparative Example 2), and the other was treated in the same manner as in Example 2, except that 140 g of water was used instead of the aqueous silica sol 180F in Example 2. (Comparative Example 3) was tested in the same manner as in Example 2.

The one according to Comparative Example 2 was considerably rusted after 7 days, and 1
After several months, the iron rod was in a considerably corroded state.

The one according to Comparative Example 3 was slightly rusted after 7 days, and 1
A few months later, the number of roads had increased slightly.

Furthermore, the plaster molds made using the method of the present invention had extremely good water resistance and did not lose their shape even after being soaked in running water for 4 hours, whereas the plaster molds of Comparative Examples 2 and 3 partially dissolved and lost their shape. was there.

Example 3 60 g of 200 meth powder of magnesia clinker, 500 g of sea sand, aqueous silica sol [containing 3% by weight of monomethyltriethanolammonium hydroxide and 12% by weight of 5iO2.

(a kind of amine dinocate)) 240g, 30% K by weight
Sequentially knead 15g of No2 aqueous solution, 5×5×10cIr
The mixture was poured into a wooden mold (t), into which iron and aluminum rods, whose surfaces had been degreased and polished with sandpaper, were inserted.

This magnesium silicate cement slurry hardened in 30 minutes.

After leaving the mold for another 6 hours and removing it from the mold and exposing it to the outdoors for 3 months, the test specimen was split and examined for rust on the iron rod and aluminum rod, but no rust was observed on either.

Claims (1)

[Claims] 1. It is characterized by containing a nitrite and a silica sol having a molar ratio of 5t02/M20 (where M represents an alkali metal atom or a substituted or unsubstituted ammonium cation) from 5 to 2000. Rust-preventive cement or gypsum composition.