JPS5833176B2 - Tanjikande Datsukeikanouna cement materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cement composition that can be demolded in a short time and provides a hardened product with high strength.

Hydraulic cement compositions generally harden slowly and are cured at room temperature (including air-drying or underwater curing).

), the mold is usually demolded 1 to 2 days after molding.

This long demolding time impairs the manufacturing efficiency of hydraulic cement products and poses a problem in mass production.

Autoclave curing is known as a method to shorten the time required for demolding after molding. A cured product has the disadvantage that its strength is lower than that of a product cured at room temperature.

Additionally, a method of adding a curing accelerator during room temperature curing is known, but conventionally known curing accelerators rarely provide enough accelerating effect to allow demolding within a few hours, and When a curing accelerator having an accelerating effect that allows removal from the mold over time is used, there is a disadvantage that the strength becomes weaker than that of a cured product of a cement composition to which no accelerator is added.

As a result of various studies to solve these drawbacks, the present inventors have found that a cement composition that exhibits high strength under various curing conditions and that can be demolded in a few hours when cured at room temperature is
It was discovered that it falls within the range of the following formulation.

(a) 60 to 120 parts by weight of alumina cement paste with a water/cement ratio of 0.2 to 0.8 (b)
Salts having sulfate or sulfite groups 0.1 to 10 parts by weight (c) Carboxylic acid salts 0.1 to 20 parts by weight (
d) Anti-shrinkage agent for cement 1 to 20 parts by weight The present invention uses alumina cement, which hardens relatively quickly among various cements, and further contains a salt having a sulfate group or a sulfite group and a carboxylate salt at the same time. Due to the synergistic effect of the composite curing accelerator, the curing time is significantly shortened and the mold can be removed from the mold in a short time after molding.

Further, in order to prevent shrinkage due to rapid hardening of the alumina cement composition containing the above-mentioned composite curing accelerator, the cement composition of the present invention is characterized in that it contains a cement shrinkage inhibitor, If the water/cement ratio of the alumina cement paste is less than 0.2, the viscosity of the cement paste will increase, resulting in poor workability during molding.

In addition, if the water/cement ratio is greater than 0.8, curing will be slow and it will take a long time for demolding to become possible, so the water/cement ratio of alumina cement paste should be 0.2 to 0.
．． A range of 8 is desirable.

The curing accelerator used in the cement composition of the present invention is a composite curing accelerator that simultaneously contains at least one selected from salts having a sulfate group or a sulfite group and at least one selected from carboxylic acid salts. Due to the synergistic hardening accelerating effect of each salt, demolding is possible within several hours after molding even when cured at room temperature.

Particularly preferable salt curing accelerators having a sulfate group include ammonium sulfate, magnesium sulfate, calcium sulfate, barium sulfate, zinc sulfate, and aluminum sulfate; examples of salt curing accelerators having a sulfite group include ammonium sulfite and sulfite. Barium, zinc sulfite, and aluminum sulfite are particularly preferred.

The carboxylate curing accelerator means an ammonium salt or a metal salt of an aliphatic carboxylic acid compound or an aromatic carboxylic acid compound having at least one carboxyl group.

Examples of aliphatic carboxylate curing accelerators include acetic acid, formic acid,
Oxalic acid, propionic acid, stearic acid, oleic acid,
There are ammonium salts and metal salts of trichloroacetic acid, sebacic acid, tartaric acid, octylic acid, acrylic acid, methacrylic acid, polyacrylic acid, isobutyric acid, citric acid, maleic acid, succinic acid, etc., and among these, particularly preferred are These include ammonium salts and barium salts of acetic acid, oxalic acid, trichloroacetic acid, and acrylic acid.

Aromatic carboxylate curing accelerators include ammonium salts and metal salts of benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, anthranilic acid, salicylic acid, P-toluic acid, P-nitrobenzoic acid, etc. Particularly desirable among these are ammonium salts and barium salts of benzoic acid, isophthalic acid, phthalic acid, and terephthalic acid.

Further, the carboxylate hardening accelerator also functions as a calcium ion scavenger and is effective in preventing the phenomenon of pleating of cement compositions.

When the amount of the salt having a sulfate group or a sulfite group is less than 0.1 part by weight in the cement composition of the present invention,
Even if a large amount of carboxylic acid salt is blended, the accelerating effect to harden in a few hours cannot be obtained, and if the amount exceeds 10 parts by weight, the contribution to the curing accelerating effect becomes small, and the strength development is also small. Therefore, the amount of the salt having a sulfate group or a sulfite group is preferably in the range of 0.1 to 10 parts by weight.

In the cement composition of the present invention, when the amount of carboxylic acid salt is less than 0.1 part by weight, even if a large amount of salt having a sulfate or sulfite group is added, the curing effect is so great that it hardens in a few hours. However, if the amount exceeds 20 parts by weight, the contribution rate in accordance with the curing accelerating effect will decrease, and the strength development will also tend to decrease. is desirable.

The cement shrinkage inhibitors contained in the cement composition of the present invention include gypsum hemihydrate, anhydrite, calcium sulfoaluminate-based cement shrinkage inhibitors, and metal oxides such as MgO and CaO that expand when strained with water. etc., but the most desirable ones are hemihydrate gypsum and calcium sulfoal□
It is a nate-based cement shrinkage inhibitor.

If the amount of the above cement shrinkage inhibitor is less than 1.0 parts by weight, a sufficient effect for preventing cracks in the hardened cement product cannot be expected, and if it is more than 20 parts by weight, the effect of preventing cracks in the hardened cement product will be reduced. Since the contribution rate tends to be small and the development of strength also tends to be small, it is desirable that the amount of the cement shrinkage inhibitor is in the range of 1.0 to 20 parts by weight.

Even when cement mortar or cement concrete containing the cement composition of the present invention mixed with various aggregates is molded, the time required for demolding can be greatly shortened.

Examples of aggregates that can be incorporated into the cement composition of the present invention include pozzolans (bentonite, activated clay, kaolin, white carbon, glass powder, fly ash, quartz powder, volcanic ash,
perlite, etc.), crushed natural stone, river sand, river gravel, whitebait balloons, crow balloons, carbon powder, metal powder, metal oxide powder, and other inorganic aggregates or organic polymer foams or beads, organic fibers, inorganic fibers, Organic aggregates include wood shavings, straw shavings, and fir grains.

The present invention will be explained below with reference to Examples.

Example 1 35 parts by weight of water was added to 100 parts by weight of Al□Na Cement (product of Asano Cement Co., Ltd.), and various hardening accelerators (
Add sulfates, sulfites, carboxylates) or cement shrinkage inhibitors, mix well, and reduce temperature to 20°C and humidity to 6.
The curing characteristics when air-drying at 0% are shown in the table below.

The initial setting time was measured using a method similar to JIS R5201, that is, in JISR5201, the sample was adjusted to the standard softness, but for this example, the sample was adjusted to the standard softness. A needle with a diameter of 1.13 mm with a load of 300 grams was applied to the sample, which was well kneaded under constant conditions with a water/cement ratio of 0.35 and left in a room at a temperature of 200 °C and a humidity of 60 °C. The point at which almost no penetration occurred was defined as the initial condensation time.

The above-mentioned sample in the casing was sandwiched between two iron plates, and 50.9/
The following table shows the test results of a molded plate that was subjected to a load of i and air-dried in a room at a room temperature of 20°C and a humidity of 60°C.

The cement compositions of Sample Nos. 1 to 13 of the Examples in which 0.1 to 10 parts by weight of a salt having a sulfate group or a sulfite group and 0.1 to 20 parts by weight of a galponate were blended had a hardening rate of 0. It can be demolded in 5 to 5 hours, and the strength is extremely high.

The cement compositions of sample numbers 2 and 3 of the comparative example are examples in which a single hardening accelerator is blended, but the curing is slower and the desorption rate is slower than that of the cement compositions of sample numbers 1 to 13 of the example. The amount of time available for molding is increased.

This is because in the cement compositions of sample numbers 1 to 13 in the example, by simultaneously blending a salt with a sulfate or sulfite group and a carboxylate, they synergistically contribute to hardening. It shows.

The cement compositions of Comparative Example Sample No. 4 containing less than 0.1 part by weight of a salt having a sulfate group and Sample No. 5 of Comparative Example containing less than 0.1 part by weight of a carboxylic acid salt are Haton. No synergistic curing accelerating effect was shown, and the time required for demolding to become possible was longer than that of Sample Nos. 1 to 13 of the Examples.

The cement compositions of Comparative Example Sample No. 6 containing more than 10 parts by weight of a salt having a sulfate group and Comparative Example Sample No. 7 containing more than 20 parts by weight of a carboxylic acid salt had a low contribution rate to the hardening accelerating effect. They tend to become smaller, more fragile, and exhibit less strength.

Example 2 100 parts by weight of alumina cement (product of Asano Cement Co., Ltd.), 35 parts by weight of water, 2.5 parts by weight of barium acetate,
1.0 parts by weight of ammonium sulfate, calcium sulfoaluminate (Denka C8A).

5 parts by weight of Denki Kagaku Kogyo Co., Ltd. product) and 300 parts by weight of 10-30 mesh river sand were blended.

Next, knead well, sandwich between two iron plates, and store at 50 ml
9/cr? The test results of mortar molded plates cured by adding t and changing curing conditions are shown in the following table.

Claims (1)

[Claims] 1 part by weight of (a) 60 to 120 parts of alumina cement paste with a water/cement ratio of 0.2 to 0.8, (b) 0.1 to 10 parts of a salt having a sulfate or sulfite group, (c) A cement composition capable of being demolded in a short time, characterized in that it contains 0.1 to 20 parts of a carboxylic acid salt and 1.0 to 20 parts of (d) a cement shrinkage inhibitor.