JPH11310443A - Admixture for cement and production of cement-based hardened product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cement admixture capable of regulating promoting actions on setting and hardening and the pot life by including amines and a nitrite as principal components therein. SOLUTION: An alkanolamine can be used as amines and, above all, triethanolamine and diethanolamine are suitable. Calcium nitrite, sodium nitrite, potassium nitrite, or the like, can be used as the nitrite and, above all, the calcium nitrite is suitable. The amount of the nitrite used is preferably >=10 pts.wt. based on 100 pts.wt. of the amines. Furthermore, a water-reducing admixture in an amount of >=5 pts.wt. based on 100 pts.wt. of the amines and expressed in terms of the solid content is preferably compounded. The amines and nitrite or further the water-reducing admixture are added to a cement paste, a mortar and a concrete and the resultant mixture is heated and/or pressed and molded to afford a cement-based hardened product. As for the cement admixture, the amines are used in an amount within the range of preferably 0.01-3 pts.wt. based on 100 pts.wt. of the cement and the nitrite is used in an amount within the range of preferably 0.05-5 pts.wt. based on 100 pts.wt. of the cement and expressed in terms of an anhydride. Furthermore, the water-reducing admixture is used in an amount within the range of preferably 0.02-3 pts.wt. based on 100 pts.wt. of the cement and expressed in terms of the solid content.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of civil engineering and construction, in which mortar or concrete is cast into a formwork.
A cement admixture, which is effective for shortening the curing time and reducing the curing cost by expressing strength at an early stage, and which can provide good shape retention by heating and / or pressure molding, and And a method for producing a hardened cementitious material.

[0002]

2. Description of the Related Art In general, the production of mortar and concrete products (hereinafter referred to as a cement-based hardened product) includes the steps of kneading concrete → casting into a mold → curing → demolding. In such a process, it is important to shorten the time from curing to demolding (curing time) to increase the rotation rate of the mold in order to reduce manufacturing costs. Conventionally, steam curing is used to shorten the curing time, but it still takes several hours to remove the mold, and the fuel cost of steam curing also increases the production cost.

[0003] On the other hand, various additives have been used for the purpose of obtaining an early strength of a cement-based hardened product without depending on steam curing. As such an additive, for example, salts such as calcium chloride, or mineral materials such as calcium aluminate, calcium sulfoaluminate, calcium fluoroaluminate, calcined alum or aluminum sulfate, and gypsum are formed on these mineral materials. The combined quick-hardening admixture is included.

However, calcium chloride has drawbacks such as corrosion of reinforcing steel in concrete due to chloride ions, a decrease in freeze-thaw resistance, and an increase in drying shrinkage. I have. In addition, a quick-setting admixture containing a mineral material as a main component generates a large amount of calcium aluminate hydrate or calcium sulfoaluminate hydrate such as ettringite or monosulfate hydrate, thereby improving quick-setting properties. It has the effect of expressing. However, since these contain a large amount of aluminum component and sulfate ion component, depending on the curing method and usage environment, the unreacted calcium component, aluminum component and sulfate ion component react after the setting and hardening of the cement are completed, and they are delayed. It has been pointed out that there is a risk that ettringite, which is soluble, may be formed and an expanded crack is generated in the cured product. Further, when the amount of such an additive, particularly a mineral-based material, is increased to increase the effect of accelerating the hardening, the setting time is remarkably shortened, and the pot life cannot be sufficiently secured, which may hinder the work.

[0005] As other early demolding methods, vibration molding or pressure vibration molding is known. This method is a method in which a slump-zero ultra-solid kneaded concrete kneaded with a low water-cement ratio is cast and then molded by applying only vibration or simultaneously applying pressure and vibration. However, this method has the drawback that the noise generated when applying vibration adversely affects the surrounding environment, and that large voids remain on the surface of the concrete product, resulting in poor aesthetics.

[0006]

As described above, the main disadvantages of the prior art are as follows. That is, as a drawback of the additive, i) Even if mortar / concrete can be imparted with rapid hardening,
The setting is remarkably fast and a sufficient working time cannot be secured. ii) The obtained cement-based cured product lacks long-term stability. In addition, noise is generated as a disadvantage of methods such as vibration molding and pressure vibration molding. And so on.

In view of the above situation, the present inventors have developed a cement admixture that enables early demolding while ensuring working time and does not reduce the durability of a cured product, and a cement-based curing agent using the same. As a result of intensive studies on the method for producing the body, the present inventors have found that the above object can be achieved by combining amines and nitrite, and completed the present invention.

[0008]

That is, the present invention provides:
1) To provide an admixture for cement containing amines and nitrite as main components. Amines or nitrites are
The effect of accelerating the setting and hardening was known, but it was difficult to secure the pot life of mortar, concrete or the like when used alone. On the other hand, the present invention makes it possible for the first time to adjust the setting and hardening action and to adjust the pot life by using the admixture for cement in which amines and nitrite are combined. In addition, the admixture for the cement,
2) 100 parts by weight of amines, 10% by weight or more of nitrite in terms of anhydride, and 3) 100% by weight of amines
It contains 5 parts by weight or more of a water reducing agent in terms of solid content based on parts by weight. In addition, the present invention provides 4) cement paste,
Mortar, concrete, amines and nitrite,
Another object of the present invention is to provide a method for producing a cement-based cured product, which comprises adding an amine, a nitrite and a water reducing agent, and heating and / or pressurizing the molded product.

As the amines according to the present invention, for example, one or more kinds of alkanolamines such as diethanolamine, triethanolamine, tripropanolamine and triisopropanolamine can be used.
Among them, triethanolamine or diethanolamine is preferable because it has an excellent effect of accelerating coagulation and hardening, particularly an effect of accelerating coagulation.

Further, as the nitrite according to the present invention, one or more of calcium nitrite, sodium nitrite and potassium nitrite can be used. Among them, calcium nitrite is preferable because of its excellent hardening and accelerating action. Nitrite has a hardening / acceleration effect by itself, and when used with amines, in addition to increasing the plasticity of mortar, concrete, etc., suppresses excessive promotion of coagulation by amines and secures the pot life. Play a role. The amount of nitrite used is preferably at least 10 parts by weight, more preferably at least 20 parts by weight and not more than 5000 parts by weight, per 100 parts by weight of the amines. Further, the amount is more preferably 40 parts by weight or more and 4000 parts by weight or less. If the amount is less than 10 parts by weight, excessive coagulation of amines may not be suppressed. In addition, amines and nitrites are known to have a corrosion inhibiting effect on steel materials, and the present admixture for cement can be expected to have a rust-preventing effect on reinforcing bars, formwork, and the like.

In the present invention, the water reducing agent reduces the amount of kneading water by imparting plasticity and fluidity to a kneaded material comprising cement, aggregate (fine aggregate, coarse aggregate) and water. It has the role of accelerating the setting and hardening to increase the strength of the cement-based hardened body. As such a water reducing agent, a water reducing agent such as lignin sulfonic acid, naphthalene sulfonic acid / formalin condensate, polycarboxylic acid or a salt thereof,
One of AE water reducer, high performance water reducer or high performance AE water reducer
Species or two or more can be used. The amount of the water reducing agent used is preferably 5 parts by weight or more, more preferably 10 parts by weight or more and 100 parts by weight, based on 100 parts by weight of amines.
0 parts by weight or less. Further, the amount is more preferably from 20 parts by weight to 800 parts by weight. If the amount is less than 5 parts by weight, sufficient plasticity and fluidity may not be imparted to the kneaded material.

Cement which can be used as the admixture for cement according to the present invention is specified in JIS such as Portland cements such as ordinary Portland cement and early-strength Portland cement, blast furnace cement, silica cement and mixed cement such as fly ash cement. Other cements such as white cement and ultra-rapid hardening cement.

The amount of the admixture for cement used is 0.01 to 3 parts by weight for amines, 0.05 to 5 parts by weight in terms of anhydrous nitrite, and 100 to 100 parts by weight of cement. The range of 0.02 to 3 parts by weight in terms of solids is preferable. Further, the range is more preferably 0.02 to 2 parts by weight for amines, 0.1 to 3 parts by weight in terms of anhydrous nitrite, and 0.05 to 2 parts by weight in terms of solids of the water reducing agent.

The admixture for cement of the present invention may be used in combination with the above-mentioned quick-setting admixture, and the addition of the admixture for cement of the present invention does not reduce the durability of the hardened cementitious product. Absent.

The method of using the cement admixture of the present invention is as follows.
The following embodiments are possible. 1) Amine, nitrite and, if necessary, a water reducing agent are separately added to mortar / concrete or the like and kneaded. 2) Add amines and nitrites and, if necessary, water reducing agents to mortar / concrete or the like in the form of a premixed mixture and knead them. 3) Kneading water in which the mixture of 2) is dissolved is added to mortar, concrete or the like and kneaded. 4) One or more of amines, nitrites, and water reducing agents are preliminarily mixed with cement and used as a cement composition. Either method does not change the setting / hardening promoting action of the admixture for cement.

The method for producing a cement-based cured product of the present invention comprises:
Mortar, concrete and the like are kneaded by the above-mentioned method of using the admixture for cement, and plasticity and fluidity are imparted. Then, the mixture is poured into a mold, and heated and / or pressed to be molded. Heating not only accelerates the hydration reaction of the cement, but also further enhances the setting promoting action of amines in particular. In addition, the plastic action of nitrite and water reducing agent
The kneading water in the concrete is easy to move, and when pressurized, excess water is removed and the structure of the hardened body becomes more dense.

The heating temperature and the pressing pressure are not particularly limited as long as they are within the range in which molding can be performed. For example, the heating temperature is preferably 25 to 100 ° C., the pressing pressure is preferably ² to ²⁰ N / mm ² , and the heating temperature is 50. ~ 100 ° C, pressurizing pressure is 4 ~ 20
N / mm ² is even more preferred. Further, when the heating and the pressurizing are simultaneously applied, the above effects are synergistically exerted, which is more effective. The molding time may be from 10 seconds to 15 minutes, and the molding time can be shortened as the heating temperature is increased and as the pressure is increased.

In the production method, the amine is used in an amount of 0.05 to 3 parts by weight, preferably 0.1 to 2 parts by weight, based on 100 parts by weight of the cement. If the amount is less than 0.05 part by weight, the formability is not sufficient, and if the amount is more than 3 parts by weight, there is a possibility of pseudo-caking. The amount of nitrite (in terms of anhydride) and the amount of water reducing agent (in terms of solid content) used are preferably at least 10 parts by weight, based on 100 parts by weight of amines, for the purpose of imparting plasticity and ensuring the pot life. .

The amount of the kneading water used is preferably within a range where plasticity and fluidity can be imparted to mortar, concrete, etc., because a smaller strength is obtained because of higher strength. For example, the water cement ratio is preferably 0.5 or less, more preferably 0.4 or less.

When the admixture for cement of the present invention is used, admixtures such as slag, fly ash, silica fume and calcium carbonate powder, polymer dispersion,
Even when an admixture such as a re-emulsifying powder resin or a fiber such as glass, vinylon, polyethylene, or polypropylene is used, the effect of the present admixture for cement can be used without impairment.

[0021]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples.

Test Example 1 A cement admixture having the composition shown in Table 1 was dissolved in kneading water and added.
35 cement pastes were made. The setting time (start and end) of the cement paste was measured by an automatic setting tester. Table 1 shows the measurement results. No. containing only water reducing agent 1-8 (Comparative Example) has remarkably slow setting. However, No. 3 containing triethanolamine, calcium nitrite and a water reducing agent. 1-1. In all of Examples 1-7 (Examples), the setting was fast, and 1-1 to N
o. 1-5 or No. 1 Nos. 1-6 and No. 1; As shown in 1-7, it can be seen that the setting time is prolonged with an increase in the amount of calcium nitrite added, and that the pot life can be easily adjusted. No. 3 containing triethanolamine and a water reducing agent and not containing calcium nitrite. 1-9 (comparative example)
Cannot be used abnormally quickly. Further, No. 3 containing calcium nitrite and a water reducing agent and not containing triethanolamine. In 1-10 (Comparative Example), the setting promotion effect is low. Therefore, it is understood that triethanolamine has a function of accelerating coagulation, calcium nitrite has a function of arbitrarily adjusting the pot life, and the object of the present invention can be achieved only by a certain combination of both.

[0023]

[Table 1]

The materials used in Test Examples 1 to 3 are shown below. Cement: ordinary Portland cement, early strength Portland cement (made by Chichibu Onoda) Sand: Toyoura standard sand Triethanolamine: reagent grade (manufactured by Kanto Kagaku) Calcium nitrite: reagent grade (made by Kanto Kagaku) Water reducing agent A: core flow NP-55 (made by Chichibu Onoda) Water reducer B: Core Flow CP-300 (made by Chichibu Onoda)

(Test Example 2) A mortar having a composition shown in Table 2 was kneaded with an admixture for cement having a composition shown in Table 3 and kneaded.
After being cast in a 4 cm × 4 cm × 16 cm formwork, a test piece was prepared by humid curing, and the compressive strength of the mortar for 12 hours was measured. Table 3 shows the measurement results. No. 1 containing only the water reducing agent. 2-4 (comparative example) has low compressive strength. However, No. 3 containing triethanolamine, calcium nitrite and a water reducing agent was used. 2-1 to No. 2-3 (Example)
Shows that the compressive strength is high, and the compressive strength increases according to the amount of calcium nitrite added. Therefore, calcium nitrite is effective for adjusting the pot life shown in Test Example 1 and for increasing the compressive strength.

[0026]

[Table 2]

[0027]

[Table 3]

(Test Example 3) A mortar shown in Table 4 was kneaded by adding an admixture for cement having the composition shown in Table 5, and then heated and pressed under the molding conditions shown in Table 5 to obtain a 30 mm x 150 m.
Specimens of mx 10 mm in thickness were prepared. The time required for heating and / or pressing until the bending strength that does not break due to its own weight was developed with both ends of the test body fixed was measured as the molding time. Table 5 shows the measurement results. No. 1 containing only the water reducing agent. 3-9 (Comparative Example) shows that the molding time was 15 minutes even under the molding conditions of a heating temperature of 70 ° C. and a pressure of 10 N / mm ^2.
Molding was not possible within minutes. On the other hand, No. 3 in which triethanolamine, calcium nitrite and a water reducing agent were added.
3-1 to No. 3-8 (Example) is a heating temperature of 25 ° C.
Under the molding conditions of 90 ° C. and the pressure of 1 to 10 N / mm ² , the molding time was 1 to 12 minutes, which was much shorter than the comparative example.

[0029]

[Table 4]

[0030]

[Table 5]

[0031]

EFFECTS OF THE INVENTION The admixture for cement according to the present invention has the following advantages. 1) Since the pot life can be arbitrarily adjusted, the working time can be easily secured. 2) In order to express the strength of the cement-based hardened body early,
The molding time can be greatly reduced. 3) Since no delayed ettringite is generated, the durability of the cement-based cured product does not decrease. And so on. Further, according to the method for producing a hardened cementitious body of the present invention, the effect of the admixture for cement can be effectively exerted, so that the working time can be significantly reduced and the production cost can be reduced.

Continuing from the front page (72) Inventor Koichi Soeda 2-4-2 Daisaku, Sakura-shi, Chiba Pref.

Claims (4)

[Claims] 1. A cement admixture comprising amines and nitrite as main components. 2. The admixture for cement according to claim 1, wherein the admixture contains at least 10 parts by weight of nitrite based on 100 parts by weight of amines in terms of anhydride. 3. The admixture for a cement according to claim 1, wherein the water reducing agent is contained in an amount of 5 parts by weight or more in terms of solid content based on 100 parts by weight of the amines. 4. Cement-based hardening characterized by adding amines and nitrites or amines, nitrites and water reducing agents to cement paste, mortar and concrete, and heating and / or pressurizing to form. How to make the body.