JP2006151759A - Quick hardening high-strength admixture for steam curing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a quick hardening high-strength admixture for steam curing in which pre-curing and low temperature rising at or below 20°C/hour is not needed, steam curing can be performed at a high temperature of about 65°C right after kneading and high strength can be imparted to a cement-based composition in a short curing time. <P>SOLUTION: The quick hardening high-strength admixture for steam curing containing calcium aluminate, lithium carbonate, and magnesium sulfate, and the quick hardening high-strength cement-based composition for steam curing obtained by mixing 10 to 100 parts by weight the admixture with 100 parts by weight Portland cement or cement mixture are provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a high-strength admixture and a high-strength cement-based composition that can impart curing promotion to various cement-based compositions such as cement paste, mortar, and concrete by steam curing.

It is known to use steam curing as a method for accelerating the hardening of a cement-based composition such as cement paste, mortar, or concrete. Steam curing is generally performed by pre-curing for about 2 to 3 hours, raising the temperature at 20 ° C./hour or less, and holding at the maximum temperature of about 65 ° C. for about 4 to 10 hours (for example, non-curing). Patent Document 1). However, the conventional method requiring pre-curing or low temperature increase has a problem that it takes time to manufacture.
In addition, a method has been proposed in which anhydrous gypsum is mixed with a cement-based composition to improve strength during steam curing (see, for example, Patent Document 1). Although it is possible to manufacture a high-strength member by the method of Patent Literature 1, this method also requires pre-curing and temperature increase at a low speed, and the manufacturing time cannot be shortened.
In addition, as a hardening accelerator used for curing at room temperature, a quick-hardening high-strength admixture containing calcium aluminate, gypsum and lithium carbonate is known, and it is relatively high at a relatively short curing time at room temperature. Strength can be obtained (see Patent Document 2).
JP-A-7-187746 Japanese Patent Laid-Open No. 2001-39761 Japan Society of Civil Engineers 1991 edition of concrete standard specifications Construction edition Published by Japan Society of Civil Engineers September 1991 p. 252-253

However, the method of Patent Document 2 does not perform steam curing at all, and is merely a mixture of a rapid-hardening high-strength admixture with cement and the like. Causes large variations. Further, at a standard environmental temperature of about 20 ° C., only a low compressive strength can be obtained as compared with the method of Patent Document 1 in which steam curing is performed. Moreover, even if steam curing is performed using the admixture of Patent Document 2, only a low compressive strength can be obtained without pre-curing, and the manufacturing time cannot be shortened.
Therefore, the object of the present invention is that pre-curing and heating at a low speed of 20 ° C./hour or less are not required, and steam curing can be performed at a high temperature of about 65 ° C. immediately after mixing, and a short curing time. An object of the present invention is to provide a rapid-curing high-strength admixture for steam curing that can impart high strength to a cementitious composition.

As a result of intensive studies to solve the above problems, the present inventors have found that an admixture in which magnesium sulfate is used in combination with calcium aluminate and lithium carbonate requires pre-curing and heating at a low speed of 20 ° C./hour or less. In addition, the present inventors completed the present invention by finding that steam curing can be performed at a high temperature of about 65 ° C. immediately after mixing, and that high strength can be imparted to the cementitious composition in a short curing time that is half or less of the usual amount.
That is, this invention provides the rapid hardening high intensity | strength admixture for steam curing containing calcium aluminate, lithium carbonate, and magnesium sulfate.

  The present invention also provides a rapid-curing high-strength cement-based composition for steam curing obtained by mixing 10 to 100 parts by weight of the above admixture with 100 parts by weight of Portland cement or mixed cement.

  According to the present invention, pre-curing and low-temperature heating are not required, and high strength can be imparted to concrete and mortar for a short time even if steam curing is performed at a high temperature of about 65 ° C. immediately after mixing. In addition to simplifying the manufacturing process of concrete products, the manufacturing time can be greatly shortened. In addition, since high strength can be obtained for a short time, it is possible to ship quickly without waiting for the material age after curing, and it is possible to omit storage work and save storage space.

The “calcium aluminate” in the present invention is a general term for a compound, a solid solution, a vitreous substance or a mixture thereof containing at least CaO and Al ₂ O ₃ as main components. The calcium aluminate used in the present invention is not particularly limited. For example, C ₁₁ A ₇ · CaF ₂ (11CaO · 7Al ₂ O ₃ · CaF ₂ ), C ₁₂ A ₇ (12CaO · 7Al ₂ O ₃ ), C _{4 A 3 S (4CaO · 3Al} 2 O 3 · SO 3), NC 8 A 3 (Na 2 O · 8CaO · 3Al 2 O 3), include _{C 3 A (3CaO · Al 2} O 3) or alumina cement Alumina cement or C ₁₂ A ₇ is preferred. A known apparatus such as an electric furnace or kiln can be used for firing the calcium aluminate. A normal pulverizer can be used for pulverization.

  As magnesium sulfate, any of anhydrous to heptahydrate can be used. Magnesium sulfate used in the present invention is much more soluble than calcium sulfate, which is the same alkaline earth metal sulfate. Therefore, it is considered that magnesium ions and sulfate ions can be supplied to the cementitious composition at a high rate, and high strength can be imparted to the cementitious composition for a short time.

  The blending amount of magnesium sulfate is preferably 50 to 200 parts by weight, more preferably 60 to 150 parts by weight, and particularly preferably 70 to 110 parts by weight, in terms of anhydride, with respect to 100 parts by weight of calcium aluminate. When the blending amount of magnesium sulfate is less than 50 parts by weight or exceeds 200 parts by weight, a sufficient strength improving effect may not be obtained.

  The rapid hardening high-strength admixture of the present invention is blended with lithium carbonate from the viewpoint of strength enhancement. Lithium carbonate has extremely low solubility, but can be dissolved in cementitious compositions with high solubility by using it together with magnesium sulfate. The blending amount of lithium carbonate is preferably 0.5 to 20 parts by weight, more preferably 0.5 to 10 parts by weight, particularly 1.0 to 5.0 parts by weight, based on 100 parts by weight of the total amount of calcium aluminate and magnesium sulfate. Part is preferred. When the blending amount of lithium carbonate is less than 0.5 parts by weight, the effect of enhancing the strength cannot be obtained sufficiently, and when it exceeds 20 parts by weight, the amount of calcium aluminate and the amount of magnesium sulfate are relatively decreased, making it difficult to shorten the curing time. Since it may become, it is not preferable.

  As long as it does not inhibit the hardening, you may further add materials other than the above to the rapid hardening high intensity | strength admixture of this invention. Examples of such materials include alkali metal or alkaline earth metal sulfates, alkali metal or alkaline earth metal carbonates, dispersants, antifoaming agents, AE agents, thickeners, silica fume, limestone fine powder, Blast furnace slag fine powder, fly ash, silica stone powder and the like can be mentioned.

  For the production of the rapid-hardening high-strength admixture of the present invention, any powder mixing mixer such as a ribbon mixer, a Ladige mixer, or a plow shear mixer can be used.

  The rapid-hardening high-strength admixture of the present invention is mixed in an amount of 10 to 100 parts by weight, more preferably 20 to 70 parts by weight, with respect to 100 parts by weight of Portland cement or mixed cement in the rapid-hardening high-strength cement composition of the present invention. Is preferred. If it is less than 10 parts by weight, sufficient short-time strength cannot be obtained, and if it exceeds 100 parts by weight, the rapid hardening property is too high, and the molding time of concrete or mortar cannot be secured sufficiently.

  As the Portland cement used in the rapid-hardening high-strength cement-based composition of the present invention, any of ordinary, early strength, ultra-early strength, moderate heat, low heat, sulfate resistance, etc. can be used. As the mixed cement, blast furnace cement, fly ash cement, or the like can be used. Further, a cement obtained by replacing a part of the mixed cement with limestone powder or silica fume, a cement obtained by adding gypsum to the mixed cement, or the like can also be used. Two or more selected from Portland cement and mixed cement may be used in combination. Portland cement is preferable from the viewpoint of effectively shortening the curing time, and ordinary Portland cement, early-strength Portland cement, or white Portland cement is particularly preferable.

  A retarder can be added to the rapid-hardening high-strength cement composition of the present invention as long as strength development is not inhibited. The retarder is not particularly limited as long as it is used in cementitious materials, but tartaric acid or tartrate is particularly preferable from the viewpoint that the degree of inhibition of strength development for a short time is small. The retarder may be added to the rapid-hardening high-strength cementitious composition at a ratio of 0.05 to 1.00% by weight with respect to Portland cement or mixed cement from the standpoint of pot life and short-term strength development. preferable.

  Examples of the fine aggregate used in the cement-based composition include river sand, sea sand, mountain sand, crushed sand, and mixtures thereof. Coarse aggregates include river gravel, sea gravel, crushed stone, or mixtures thereof.

  You may add a water reducing agent, a high performance water reducing agent, or a high performance AE water reducing agent further to a cementitious composition. As water reducing agents, high performance water reducing agents or high performance AE water reducing agents, high performance water reducing agents such as alkylallyl sulfonic acid type, naphthalene sulfonic acid type, melamine sulfonic acid type, polycarboxylic acid type, lignin sulfonic acid type, etc. AE water reducing agent is also included), and either liquid or powder can be used.

  The method for producing the cement-based composition is not particularly limited, and the rapid-hardening high-strength cement-based composition of the present invention may be mixed with a conventional mixer installed in a ready-mix factory or construction site. The cement-based composition can be molded by any molding method using a known molding apparatus.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example.

Examples 1-5
[Materials used]
(1) Cement: Ordinary Portland cement (manufactured by Taiheiyo Cement)
(2) Fine aggregate: Crushed sand from Minami-Ogura-ku, Kitakyushu City (specific gravity: 2.69): Sea sand off the coast of Noura, Iki-gun, Nagasaki Prefecture (specific gravity: 2.59) = 3: 7 (weight ratio) mixed product (3) Water; tap water (4) retarder; Rochelle salt

(5) Quick hardening high-strength admixture, calcium aluminate A1; Alumina cement
A2: C ₁₂ A ₇ was fired at 1,600 ° C. in an electric furnace and pulverized with a ball mill. Blaine specific surface area 5000 cm ² / g.
・ Lithium carbonate / sulfate B1; anhydrous gypsum (manufactured by Taiheiyo Materials Co., Ltd.)
B2: Magnesium sulfate / anhydride (manufactured by Maui Kasei Kogyo Co., Ltd.)

  The above calcium aluminate, lithium carbonate and sulfate were mixed using a Laedige mixer (manufactured by Laedige) to obtain a quick-hardening high-strength admixture.

[Production of cementitious composition and compressive strength test]
The rapid hardening high-strength admixture prepared according to the formulation shown in Table 1 and the cement, Rochelle salt, fine aggregate, and water in the mixing ratio shown in Table 1 are mixed for 1 minute using a Hobart mixer, and the rapid hardening high A strong cementitious composition was obtained. Moreover, as a specimen for a strength test, a specimen of 4 × 4 × 16 cm was molded in a constant temperature room at 20 ° C., immediately subjected to steam curing (65 ° C.) without pre-curing and heating time, and taken out after 4 hours, The compressive strength was measured immediately. The molding method and the compressive strength test method were performed in accordance with the test method of JIS R 5201. The measurement results are shown in Table 1.

  As is apparent from Table 1, when the rapid curing high-strength admixture for steam curing according to the present invention is used, a high-strength cement-based composition (with a short curing time) can be obtained even if there is no pre-curing and heating time. I was able to get things. On the other hand, as shown in Comparative Example 1, when gypsum was used instead of magnesium sulfate, the compressive strength was significantly reduced.

  When magnesium sulfate is used, it is not necessary to make the particle size of the magnesium sulfate powder extremely fine due to its high solubility, and the powder obtained by premixing with calcium aluminate and lithium carbonate is pneumatically fed compared to the gypsum system. In addition, it is difficult to form a bridge during storage. In addition, the cement material after adding water to the admixture has an advantage of low viscosity and can be mixed in a short time.

Claims (4)

  Quick hardening high strength admixture for steam curing containing calcium aluminate, lithium carbonate and magnesium sulfate.   The rapid-curing high-strength admixture for steam curing according to claim 1, comprising magnesium sulfate in an amount of 50 to 200 parts by weight in terms of anhydride with respect to 100 parts by weight of calcium aluminate.   The rapid hardening high-strength admixture for steam curing according to claim 1 or 2, wherein lithium carbonate is contained in an amount of 0.5 to 20 parts by weight with respect to 100 parts by weight of the total amount of calcium aluminate and magnesium sulfate.   A rapid hardening high-strength cement composition for steam curing obtained by mixing 10 to 100 parts by weight of the admixture according to any one of claims 1 to 3 with respect to 100 parts by weight of Portland cement or mixed cement.