JPH02271946A - Cement admixture - Google Patents

Abstract

PURPOSE:To easily form a cement admixture at low cost which is capable of producing a cement hardening body excellent in waterproof property, wear resistance, acid resistance and early strength developing properties by incorporating dihydrate gypsum, the ion component of calcium and the ion components of iron(III) and/or aluminum into water. CONSTITUTION:A cement admixture is obtained by incorporating dihydrate gypsum, the main ion component consisting of calcium ion and an auxiliary ion component consisting of one kind or two kinds selected from iron (III) ion and aluminum ion into water. The rate of respective components in this cement admixture is preferably set as described hereunder. In other words, when the total amount of dihydrate gypsum and salt for giving the respective ions is regulated to 100 pts.wt., the rate of the respective components is constituted of 1-5 pts.wt. dihydrate gypsum, 1-5 pts.wt. salt for giving one kind or two kinds selected from iron (III) ion and aluminum ion and the balance salt for giving calcium ion. As the salt for giving calcium ion, calcium nitrate is preferably utilized. As the salt for giving iron (III) ion and/or aluminum ion, sulfate and/or nitrate are preferably utilized.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a cement admixture, and more specifically, the present invention relates to a cement admixture. This invention relates to a cement admixture that can provide a hardened cement product.

INDUSTRIAL APPLICATION This invention is utilized for the material which provides waterproofness etc. to a cement molding, a construction object, etc.

[Conventional technology]

The following materials are known as materials that provide waterproofness to molded products and constructed products.

First, there are organic polymer materials that fill voids with film-forming substances and increase water permeation resistance, such as latex, polymer emulsions, and water-soluble polymers.

Second, there are organic compounds that fill the voids with water-repellent substances and increase the internal water permeation resistance, such as metal soaps, paraffin emulsions, and asphalt emulsions.

Thirdly, there are substances that react with components in cement to produce water-repellent substances inside, such as higher fatty acids.

Fourth, there are inorganic materials that fill the voids with fine substances and have high water permeation resistance, such as silicate powder, calcium hydroxide, barium sulfate, and the like.

Fifth, inorganic materials, such as sodium silicate, which react with components in the cement to produce fine particles that fill the voids.
Potassium, silicofluoride salt, aluminum chloride, calcium chloride, hemihydrate ceracola, etc.

Sixthly, there are water reducing agents and the like as organic surfactants that reduce voids and increase water permeation resistance due to their water reducing effect.

[Problem to be solved by the invention]

Those using the above-mentioned organic materials 1 to 3 generally have delayed strength development, reduced long-term strength, and are inferior in weather resistance and heat resistance compared to inorganic materials. In particular, a polymer emulsion among the first organic polymer materials has excellent waterproof properties, but requires a large amount of use and is expensive. The fourth inorganic material is
Strength decreases because it does not have bonding strength to cement.

On the contrary, the fifth inorganic material is highly reactive with cement and is therefore often used as a rapid setting agent. Therefore, in order to obtain the necessary and sufficient waterproofness through a gentle setting reaction, a separate retarder is required. I need. Also, since chlorine-containing substances tend to cause metal corrosion, and alkali-containing substances may cause an alkali aggregate reaction, the amount of addition is JIS A62.
04 (chemical admixtures for concrete). The sixth one does not show sufficient waterproofing effect.

The present invention solves the above-mentioned problems, and aims to provide a cement admixture that can be easily and inexpensively produced and provides a hardened cement product that is excellent in waterproofness, abrasion resistance, acid resistance, and early strength development. purpose.

[Means to solve the problem]

The cement admixture of the first invention contains dihydrate gypsum, a main ion component consisting of calcium ions, and a subsidiary ion component consisting of one or two of iron (III) ions and aluminum ions in water. It is characterized by containing.

This dihydrate gypsum reacts with the aluminate compound in the cement hydrate to form calcium sulfoaluminite, and the calcium ions react with hydroxide ions to form calcium hydroxide, resulting in cement hydration. By filling the gaps between crystals and aggregates, it achieves excellent waterproof properties, improved compressive strength, and early strength development. Therefore, in the present invention,
Gypsum dihydrate and calcium ions are essential. This gypsum dihydrate may be a powder, but it is preferably as fine a particle as possible, for example, the average particle size is preferably about 10 μm or less. This is because it has good dispersibility and high reactivity, so it fills a predetermined gap and is preferable for improving waterproof properties and the like.

The auxiliary ions may include only iron (nl) ions, only aluminum ions, or both of these ions. This iron ion only needs to be a trivalent ion when used, that is, in a cement admixture, and when preparing raw materials, not only a trivalent salt but also a divalent salt may be added, and in this case, it is oxidized in water. and becomes a trivalent ion. The reason why this secondary ion is essential is as follows. First, the addition of these ions to cement improves the production rate and amount of calcium sulfoaluminate, which is important in the present invention. This is because these ions react first with calcium ions, gypsum dihydrate, and water to form crystal nuclei of calcium sulfoaluminate, thereby assisting the growth of calcium sulfoaluminate produced from calcium aluminate in the cement. Second, since strong salts of iron and aluminum (sulfates, nitrates, etc.) dissolve in water and exhibit acidity, this is to prevent calcium ions from forming calcium hydroxide and precipitating.

Thirdly, since these ions are constituents of cement minerals, it is thought that the addition of a small amount will not have a significant adverse effect on the properties of cement. The salt that provides these ions may be any salt that becomes ions in water under predetermined conditions.

In addition, it is sufficient that the above compounds and each ion are contained in water, and it is preferable that dihydrate gypsum be dispersed almost uniformly, but the present invention is not limited to this, and even if the dispersion state is insufficient, it can be dispersed during use. It may also be used in Furthermore, the concentration of this dihydrous gypsum or each ion is variously selected depending on the purpose, use, etc. Usually, a concentrated stock solution is prepared and diluted for use, but the method is not limited thereto.

The cement admixture of the second invention contains 1 to 5 parts of dihydrate gypsum, iron (II
I) One or two of ions and aluminum ions
It is characterized in that the salt that provides seeds is 1 to 5 parts, and the remainder is a salt that provides calcium ions. 1 to 5 pieces of dihydrate gypsum
The reason for this is that if it is less than 1 part, the rapid hydration reaction of the cement will cause the raw sil-calcium sulfoaluminate to fill in the gaps of cement hydrate crystals, etc., and the effect will be insufficient and waterproof properties will not necessarily be excellent. If the amount exceeds 5 parts, the calcium sulfoaluminate crystals not only fill the gaps in the cement mineral hydrate but also form matrices, which does not lead to further improvement in strength and waterproofness. It is from.

In the cement admixture of the third invention, the salt that provides calcium ions is calcium nitrate, the salt that provides one or two of iron ([) ions, and aluminum ions is one or two of sulfates and nitrates. Characterized by being a species. When one of iron (III) ions and aluminum ions is used, this imparting salt may be a sulfate or a nitrate, and when both of these ions are used, both may be a sulfate or a nitrate, or a mixture thereof may be used.

In the present invention, gypsum dihydrate may be provided in advance in the form of fine particles to the admixture stock solution, or it may be produced by reacting calcium nitrate with a water-soluble sulfate such as iron (II) sulfate in an aqueous solution. You may let them. At this time, by adding an excess amount of calcium salt, the necessary amount of calcium ions can be present in the admixture.

In the present invention, in order to ensure the stability of calcium ions in the admixture stock solution and diluted solution, it is preferable to make the pH acidic. For this purpose, for example, as mentioned above, iron,
Sulfates and nitrates of metals such as aluminum can be added.

In addition, soluble silica or alumina can be added to this admixture to cause a pozzolan reaction with calcium hydroxide to improve water resistance and chemical resistance. In addition, general cement admixtures such as water reducing agents and rust preventive agents, swelling agents,
Antifungal agents, organic cement, etc. can also be added.

[Effect]

Trihydrate gypsum particles react with aluminate hydrate formed by a rapid hydration reaction in cement + minerals, producing needle-shaped crystals of high sulfate type calcium sulfoaluminate called ettringite. Then, it fills the voids in the cement mineral hydrate and aggregate. Furthermore, the calcium ions present in excess react with hydroxide ions generated as the cement hydration reaction progresses to precipitate calcium hydroxide, which further fills the voids and accelerates the hydration reaction. For this reason, the cured product is endowed with waterproof properties, reduced shrinkage, early strength development, and the like.

If soluble silica and alumina coexist at this time, they will react with calcium hydroxide to produce poorly soluble lime silicate hydrate and lime aluminate hydrate, improving water resistance and chemical resistance. This is the same effect that silica and alumina in mixed cements such as blast furnace cement and silica cement provide chemical resistance.

〔Example〕

(1) Preparation of admixtures 2.5 parts of dihydrate gypsum (particle size 10 μm or less), iron nitrate (
I [I) 2. 5 parts of calcium nitrate and 95 parts of calcium nitrate, add an equal amount of water and stir thoroughly to obtain a stock solution. Furthermore, fine crystals of dihydric gypsum may be created during compounding using water-soluble sulfate and calcium salt. For example, iron sulfate (
II) 2.5 parts of calcium nitrate and 97.58'lS of calcium nitrate.

The specific gravity of these aqueous solutions is about 1.3.

(2) Mixing of mortar 100 parts of ordinary Portland cement, 30 parts of No. 8 silica sand, and 43 parts of a diluting admixture were mixed. The dilution rate can be varied from 4 to 20 times depending on the coagulation time and required physical properties.q
In the following tests, the ratio was set to 5.79.11 times. In addition, in the blank as a comparative example, 4 ml of water was used instead of this diluting admixture.
Three parts were used.

(3) Performance evaluation Using the above-mentioned mortar formulation, various hardened cement bodies were used as test specimens to evaluate compressive strength, setting time, water permeation resistance, abrasion resistance, and acid resistance. Curing time for each cured product is 20±
Basically, it was cured for 28 days in water at 5°C.

(a) Compressive strength Compressive strength (kgf/cm2), dilution rate 5.7.9.
A blank hardened product obtained by adding only water and a cement hardened product obtained by changing the ratio to 11 times was used as a test specimen.JIS A
1108 (Concrete Compressive Strength Test Method), and the results are shown in Table 1.

According to this result, the compressive strength is about twice as high as that of the blank at any dilution rate of 5 to 11 times.

(Leaving space below) Table 1 (b) Setting time The setting time is determined based on JIS A6204 (Chemical admixtures for concrete) Annex 1 (Test method for setting time of concrete) for specimens with the same mixing conditions as the compressive strength.
The final time (hr) results are shown in Table 2.

Table 2 According to the results, when the dilution was 11 times, it was about the same as the blank, but when the dilution was 5.7.9 times, both (especially 5
．． 7 times)) It solidifies in a short time and shows early strength development.

(c) Water permeability resistance (waterproofness) As waterproofness evaluation, inner diameter is 250mm, wall thickness is 281ilff
Blaine mortar without an admixture on the inner surface between the two chambers and mortar obtained with an admixture diluted five times were lined to a thickness of 5 [111] under similar curing conditions. After that, both ends of this product were sealed, water was forced into the space, and the water pressure (kgf/cm2) when water leakage was visually observed was measured. The results are shown in Table 3.

It exhibits water permeation resistance 1.7 times or more compared to the rank in Table 3, and 4 times or more compared to untreated, and has extremely excellent waterproof properties.

(d) Abrasion resistance Abrasion resistance was measured by testing specimens obtained by curing a cured mortar obtained with a 5-fold diluted admixture and a cured plain mortar under similar curing conditions under a load of 500 g. Tapered wear tester (wearing wheel: GC-J IOO
) was evaluated.

According to the results, when the admixture was used, the amount of wear was about 1/4 of that of the blank, and the wear resistance was about 4 times higher.

Table 4 According to the results, when an admixture is used, the acid resistance of the cured product with the admixture diluted five times and the plain cured product are cured in water for 7 days. The test specimen (40×40×160+++n+) obtained by the above was immersed in 1N sulfuric acid for 3 days at 20±5° C., and its weight loss was measured.

According to the results, when the admixture was used, the reduction rate was about 1/3 compared to the blank, indicating about 3 times the acid resistance.

Table 5 (4) Summary As can be seen from the above, the admixture of this example can be easily produced by simply blending predetermined compounds, and since inexpensive raw materials are used, this admixture is also inexpensive. Furthermore, even when diluted 5 to 11 times, this product has extremely excellent compressive strength and hardening properties, except that the setting time is the same when diluted 11 times compared to the comparative example product, and it can be used at a dilution ratio according to the purpose. It's very convenient. In addition, in the case of 5 times dilution, the compressive strength is about 2 times, the setting time is 3/4,
It has excellent water permeation resistance of more than twice as much, abrasion resistance of about 4 times, and acid resistance of about 3 times.

Note that, in place of iron sulfate, iron nitrate (■), aluminum sulfate or aluminum nitrate, or even a mixture thereof, can be used to show the same good performance as above.

〔Effect of the invention〕

As described in the above actions and examples, the cement admixture according to the present invention can be easily and inexpensively produced, and its use produces a hardened cement product with extremely excellent waterproof properties, early strength development, abrasion resistance, and acid resistance. Can be provided.

Claims (3)

[Claims] (1) A cement characterized by containing dihydrate gypsum, a main ionic component consisting of calcium ions, and a secondary ionic component consisting of one or two of iron (III) ions and aluminum ions in water. Admixture. (2) The total amount of dihydrate gypsum and the salt that provides each ion is 1
00 parts by weight, dihydrate gypsum is 1 to 5 parts by weight,
The cement admixture according to claim 1, wherein the salt that provides one or both of iron (III) ions and aluminum ions is 1 to 5 parts by weight, and the remainder is a salt that provides calcium ions. (3) The salt that provides calcium ions is calcium nitrate,
The cement admixture according to claim 1 or 2, wherein the salt providing one or two of iron (III) ions and aluminum ions is one or two of sulfates and nitrates.