JP2000247702A - Cement admixture and cement composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cement admixture and a cement composition, both having a small temperature dependence on depressing effect on heat of hydration, capable of remarkably reducing the calorific value of heat of hydration, excellent in strength manifestation and used in the field of civil engineering and construction. SOLUTION: The cement admixture comprises alkali metal carbonates, organic acids and a dextrin containing 5-90 wt.% soluble content in cold water at 20 deg.C, and additionally a strength-enhancing agent containing a reactive silica fine powder and/or anhydrous gypsum. The cement composition comprises the cement admixture and cement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cement admixture and a cement composition mainly used in the fields of civil engineering and construction.

[0002]

2. Description of the Related Art Cement / concrete is an excellent material that can be used to construct a large structure at low cost, but has the disadvantage of cracking due to various causes. One of the causes is cracking due to hydration heat generation. Cracks due to heat of hydration are generated when a large amount of concrete is poured, and various methods have been proposed to suppress this. Above all, the method of using low heat Portland cement with an increased belite content, which has a low hydration calorific value, not only can significantly reduce the hydration calorific value, but also makes it easy to secure fluidity, It has excellent properties such as good strength development over a long period of time. However, normally, there is at most three cement silos at the ready-mixed concrete plant, and ordinary Portland cement, blast furnace cement, and early-strength Portland cement that are shipped in large quantities are stored. At present, there is almost no ready-mixed concrete factory that has silos dedicated to low-heat Portland cement with a small shipment volume. Therefore, at present, low-heat Portland cement is only shipped to large-scale properties where a ready-mixed concrete plant is installed at a casting site. In this way, the admixture type does not require new capital investment such as additional silos, and can be put into practical use at ready-mixed concrete plants around the country by opening bags, but low heat Portland cement has excellent properties. However, since the type of use is of the cement type, there is a problem that new capital investment such as additional silos is required.

On the other hand, organic acids have been known as setting retarders for cements (JP-A-50-80315, US Pat. No. 3,427,175). However, when an organic acid is used, the effect of suppressing the heat of hydration can be obtained, but there is a problem that the strength expression is deteriorated and the setting is extremely delayed. In order to solve such a problem, an admixture mainly composed of an organic acid and a quick-setting alkali metal inorganic salt such as an alkali metal carbonate, silicate, aluminate and hydroxide has been proposed. (Japanese Patent Publication No. Hei 7-12963). However, this admixture has a large temperature dependency on the heat of hydration suppression, and has a problem that the heat of hydration suppression is remarkable at low temperatures but is poor at high temperatures.

[0004] Dextrin is also known as a heat of hydration inhibitor (Japanese Patent Publication No. 57-261). However,
There is a problem that dextrin has almost no effect of suppressing heat of hydration at low temperatures and excessively delays hydration at high temperatures.

[0005] To solve this problem, an admixture containing dextrin and salicylic acid, a kind of organic acid, as main components has been proposed (Japanese Patent Application Laid-Open No. 60-54955). However, this admixture has the advantage that the temperature dependence on the effect of suppressing heat of hydration is small, but there is a problem that the strength development is poor. For this reason, development of a material that has a small temperature dependence on the heat of hydration suppression effect, can significantly reduce the calorific value of hydration, and has good strength development has been awaited today.

As a result of various efforts, the inventor of the present invention has found that the above-mentioned problems can be solved by using a specific cement admixture, and has completed the present invention.

[0007]

That is, the present invention is a cement admixture containing alkali metal carbonates, organic acids, and dextrin having a cold water soluble content at 20 ° C. of 5 to 90% by weight, The cement admixture further comprising a strength enhancer, wherein the strength enhancer is the cement admixture of reactive silica fine powder and / or anhydrous gypsum, comprising the cement admixture and cement. A cement composition.

Hereinafter, the present invention will be described in more detail.

The alkali metal carbonates (hereinafter referred to as "carbonates") used in the present invention are not particularly limited, and are a general term for carbonates or bicarbonates such as sodium, potassium and lithium, and are anhydrous. Salts and hydrated salts can be used. The maximum particle size of the carbonates is 1
mm or less is preferable, and 0.1 mm or less is more preferable. If the maximum particle size of the carbonates exceeds 1 mm, sufficient strength development may not be obtained.

The organic acids used in the present invention are not particularly limited, and carboxylic acids, oxymonocarboxylic acids,
Oxypolycarboxylic acids and polycarboxylic acids or salts thereof can be used. As specific examples thereof, for example, as the carboxylic acid, oxalic acid of a saturated or unsaturated carboxylic acid, malonic acid, succinic acid, glutaric acid, adipic acid,
Maleic acid, fumaric acid, heptanoic acid and the like are mentioned, and monooxycarboxylic acids are heptonic acid, gluconic acid, glycolic acid and the like. Examples of the oxypolycarboxylic acid include malic acid, tartaric acid, and citric acid, and examples of the polycarboxylic acid include co-condensates such as acrylic acid and maleic anhydride. These salts include alkali metal salts, alkaline earth metal salts, and salts of zinc, copper, aluminum, ammonium and the like.

The dextrin used in the present invention is also called a soluble starch, and is usually obtained by adding a dilute acid to a starch and decomposing it by heating. However, it is obtained by a production method such as enzymatic decomposition of starch or condensation of glucose. Although those which can be used are also usable, it is necessary that the cold-water-soluble matter at 20 ° C. (hereinafter, simply referred to as cold-water-soluble matter) is 5-90% by weight. In particular, it is preferable to use one having a cold water soluble content of 10 to 65% by weight. If the amount is less than 5% by weight, a sufficient heat suppressing effect may not be obtained, and if it exceeds 90% by weight, poor curing may occur.

The strength enhancer used in the present invention comprises a reactive silica fine powder and / or anhydrous gypsum.

The term "reactive silica fine powder" (hereinafter referred to as "silica powder") used in the present invention is a general term for fine powder of a substance having a siliceous component as a main component and having an alkali latent hydraulic property, and is particularly limited. However, examples thereof include fine powders such as silica fume, diatomaceous earth, silicate clay, fly ash, blast furnace slag, and silica dust, and one or more of these can be used in the present invention.
The particle size of the silica powder, blur - preferably 4,000 cm ² / g or more in emission values, more preferably at least ^{6,000cm 2 / g, 8,000cm 2 /} g or more is most preferred. If it is less than 4,000 cm ² / g, sufficient strength may not be obtained.

The anhydrous gypsum used in the present invention is not particularly limited. Natural anhydrous gypsum naturally produced, anhydrous gypsum produced as an industrial by-product, or gypsum dihydrate or hemihydrate gypsum is subjected to heat treatment. Anything can be used, such as those obtained by using Although the particle size of the anhydrous gypsum is not particularly limited,
2,000 cm ² / g or more is preferable, and 4,000 cm ² / g or more is more preferable. If it is less than 2,000 cm ² / g, strength developability and dimensional stability may deteriorate.

The proportion of the components in the cement admixture of the present invention is not particularly limited, but the cement admixture may be a dextrin (hereinafter, referred to as a dextrin having a carbonate, an organic acid, and a cold water soluble content of 5 to 90% by weight). DX), the carbonate is preferably 40 to 80 parts by weight, more preferably 50 to 70 parts by weight, per 100 parts by weight of the cement admixture. Organic acids are 5
It is preferably from 40 to 40 parts by weight, more preferably from 10 to 30 parts by weight.
Further, DX is preferably 5 to 40 parts by weight, more preferably 10 to 30 parts by weight. If the component ratio in the cement admixture is outside the above range, the temperature dependency on the hydration heat suppression effect is small, the calorific value of hydration can be significantly reduced, the strength developability is good, and the initial fluidity is also high. In some cases, the effects of the present invention, that is, better performance, that is, multi-dimensional performance improvement, cannot be obtained. In addition, when the cement admixture is made of carbonates, organic acids, DX, and a strength enhancer, the carbonates are preferably 1 to 20 parts by weight in 100 parts by weight of the cement admixture,
5 to 15 parts by weight are more preferred. The organic acids are 1 to 20
It is preferably 5 parts by weight, more preferably 5 to 15 parts by weight. DX is preferably 1 to 20 parts by weight, more preferably 5 to 15 parts by weight. Further, the strength enhancing material is preferably 60 to 97 parts by weight, more preferably 70 to 95 parts by weight. If the component ratio is outside the above range, the temperature dependency on the heat of hydration suppression is small, the calorific value of hydration can be significantly reduced, the strength developability becomes good, and the effect of the present invention may not be sufficiently obtained. is there.

The amount of the cement admixture of the present invention is not particularly limited, but when the cement admixture is composed of carbonates, organic acids, and DX, a binder 100 composed of cement and cement admixture is used. Of the parts by weight, 0.05 to 2 parts by weight is preferable, and 0.1 to 1 part by weight is more preferable. When the amount of the cement admixture is outside the above range, the temperature dependency on the heat of hydration suppression is small, the calorific value of hydration can be significantly reduced, and the effect of the present invention in which the strength developability is good cannot be obtained. If the cement admixture is composed of carbonates, organic acids, DX, and strength enhancers, the binder
In 100 parts by weight, 1 to 10 parts by weight is preferable, and 2 to 5 parts by weight is more preferable. If the amount of the cement admixture is outside the above range, the temperature dependence on the hydration heat suppression effect is small,
In some cases, the effect of the present invention, in which the calorific value of hydration can be remarkably reduced and the strength developability is good, cannot be obtained.

Here, as cement, ordinary, early strength,
Alternatively, various types of ultra-high strength Portland cement, various types of mixed cement obtained by mixing blast furnace slag, fly ash, or the like with these Portland cements can be used. By using these cements in combination with the cement admixture of the present invention, it is possible to obtain a cement composition having a small hydration calorific value and good strength development, but a moderately heat Portland semester which originally has a small hydration calorific value. The cement admixture of the present invention may be used in combination with a cement or a low heat Portland cement.

In the present invention, in addition to cement and cement admixture and aggregates such as sand and gravel, a setting accelerator, a water reducing agent, an AE
Water reducer, high-performance water reducer, high-performance AE water reducer, AE agent, thickener, cement quick-hardening material, cement expansion agent, rust preventive, antifreeze, polymer emulsion, clay minerals such as bentonite and montmorillonite, zeolite , Hydrotalcite, and ion exchangers such as hydrocalmite, inorganic phosphates, and one or more of boric acid and the like can be used in combination within a range that does not substantially inhibit the object of the present invention. It is.

As the mixing device used for producing the cement admixture of the present invention, any existing stirring device can be used. For example, a tilting mixer, an omni mixer, a V-type mixer, a Henschel mixer can be used. , And Nauta
Mixers and the like can be used.

In the mixing, the respective materials may be mixed at the time of construction, or some or all of them may be mixed in advance.

[0021]

Hereinafter, the present invention will be described in detail with reference to experimental examples.

EXPERIMENTAL EXAMPLE 1 60 parts by weight of carbonates A, 20 parts by weight of organic acids a, and DX
20 parts by weight were blended to prepare a cement admixture. The amount of the cement admixture in 100 parts by weight of the cement and the cement admixture prepared was changed as shown in Table 1, and the unit binder amount was 300 kg / m ³ , the unit water amount was 150 kg / m ³ , and S / a
= 42% was prepared, and the adiabatic temperature rise and compressive strength were measured. The results are also shown in Table 1.

<Materials Used> Carbonates A: Potassium carbonate, Reagent 1st grade Organic acids a: Citric acid, Reagent 1st grade DX A: Cold water soluble 30% by weight Cement α: Ordinary Portland cement, Commercial product Sand: Niigata Himekawa sand, specific gravity 2.62 Gravel: Himekawa, Niigata prefecture, crushed stone, G _max = 20mm, specific gravity 2.64 Water: tap water

<Measurement Method> Adiabatic Temperature Rise: In order to examine the temperature dependence on the hydration heat suppression effect, an adiabatic temperature rise amount measuring device manufactured by Tokyo Riko Co., Ltd. was used. Measured under three conditions: 20 ° C and 30 ° C Compressive strength: Measured according to JIS A 1108

[0025]

[Table 1]

Experimental Example 2 The amount of the cement admixture in 100 parts by weight of the binder was 0.5 parts by weight, and the amounts of carbonates A, organic acids a, and DX in 100 parts by weight of the cement admixture were as shown in Table 2. The experiment was performed in the same manner as in Experimental Example 1 except that the temperature was changed as shown in FIG. The results are also shown in Table 2.

[0027]

[Table 2]

Experimental Example 3 An experiment was conducted in the same manner as in Experimental Example 1 except that the amount of the cement admixture in 100 parts by weight of the binder was 0.5 parts by weight and the carbonates shown in Table 3 were used. The results are also shown in Table 3.

<Materials used> Carbonate B: sodium carbonate, reagent primary carbonate C: lithium carbonate, reagent primary carbonate D: sodium bicarbonate, reagent primary carbonate E: 50 parts by weight of carbonate A and carbonate Mixture of D50 parts by weight

[0030]

[Table 3]

Experimental Example 4 An experiment was performed in the same manner as in Experimental Example 1 except that the amount of the cement admixture in 100 parts by weight of the binder was 0.5 part by weight and the organic acids shown in Table 4 were used. The results are also shown in Table 4.

<Materials Used> Organic acids b: tartaric acid, reagent primary organic acids c: sodium gluconate, reagent primary organic acids d: malonic acid, reagent primary organic acids e: polycarboxylic acid, commercially available organic acids f : A mixture of 50 parts by weight of first-class reagent citric acid and 50 parts by weight tartaric acid

[0033]

[Table 4]

Experimental Example 5 Experimental Example 1 was conducted except that the amount of the cement admixture in 100 parts by weight of the binder was 0.5 part by weight and DX shown in Table 5 was used.
The same was done. The results are also shown in Table 5.

<Materials Used> DX B: 5% by weight of soluble in cold water DX C: 10% by weight of soluble in cold water DX D: 65% by weight of soluble in cold water DX E: 90% by weight of soluble in cold water DX: Cold water soluble content 0% by weight DX G: Cold water soluble content 95% by weight

[0036]

[Table 5]

Experimental Example 6 A cement admixture was prepared by mixing 10 parts by weight of carbonates A, 10 parts by weight of organic acids a, 10 parts by weight of DXA, and 70 parts by weight of a strength enhancer A. The procedure was performed in the same manner as in Experimental Example 1 except that the cement admixture shown in Table 6 was used in 100 parts by weight of the binder. The results are also shown in Table 6.

<Materials used> Strength enhancer A: silica fume, commercial product, Brain value 8.8
40cm ² / g

[0039]

[Table 6]

Experimental Example 7 The amount of the cement admixture in 100 parts by weight of the binder was 3 parts by weight, and in 100 parts by weight of the cement admixture, carbonates A, organic acids a, DXi, and strength shown in Table 7 were shown. The same operation as in Experimental Example 6 was carried out except that the enhancer A was used. The results are also shown in Table 7.

[0041]

[Table 7]

Experimental Example 8 An experiment was conducted in the same manner as in Experimental Example 6 except that the amount of the cement admixture in 100 parts by weight of the binder was 3 parts by weight, and the strength enhancing materials shown in Table 8 were used. The results are also shown in Table 8.

<Materials used> Strength enhancer B: Blast furnace slag, commercial product, Brain value 6,040cm
² / g Strength-increasing material C: Fly ash, commercial product, Brine value 4,1
10cm ² / g Strength enhancer D: Natural anhydrous gypsum, commercial product, Brain value
3,520cm ² / g Strength enhancer E: By-product anhydrous gypsum, commercial product, Brain value
5,200cm ² / g Strength enhancer F: A mixture of 50 parts by weight of strength enhancer A and 50 parts by weight of strength enhancer E

[0044]

[Table 8]

Experimental Example 9 The same operation as in Experimental Example 6 was carried out except that the cement admixture was used in an amount of 3 parts by weight per 100 parts by weight of the binder and the cements shown in Table 9 were used. The results are also shown in Table 9.

<Materials> Cement β: Low heat Portland cement, commercial product, Brain value 3,640 cm ² / g Cement γ: Early high strength Portland cement, commercial product, Brain value 3,870 cm ² / g

[0047]

[Table 9]

[0048]

EFFECT OF THE INVENTION By using the cement admixture of the present invention, the temperature dependency on the hydration heat suppression effect is small,
It is possible to provide a cement composition that can significantly reduce the heat of hydration and improve strength.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Minoru Shirasawa 2209 Aomi, Aomi-cho, Nishikubiki-gun, Niigata Inside the Aomi Plant of Denki Kagaku Kogyo Co., Ltd. Chemical industry Co., Ltd. Aomi factory F term (reference) 4G012 MB06

Claims (4)

[Claims] 1. An alkali metal carbonate, an organic acid, and
A cement admixture containing dextrin having a soluble content of cold water at 20 ° C. of 5 to 90% by weight. 2. Alkali metal carbonates, organic acids, 20 ° C.
A cement admixture comprising a dextrin having a cold water-soluble content of 5 to 90% by weight and a strength enhancer. 3. The method of claim 1, wherein the strength-enhancing material is a reactive silica fine powder and / or
3. The cement admixture according to claim 2, wherein the cement admixture is anhydrous gypsum. 4. A cement composition comprising the cement admixture according to claim 1 and cement.