JPH0680452A - Cement admixture and cement composition - Google Patents

Abstract

PURPOSE:To provide a cement admixture and a cement composition effective in promoting the development of strength and increasing the strength of mortar or concrete and useful for concrete products, etc., as well as general buildings and constructions. CONSTITUTION:The objective cement admixture contains gypsum, an aluminum compound, an alkali metal sulfate, an alkali metal aluminate and a setting controlling agent as active components and the objective cement composition is composed of cement and the above cement admixture. The use of the cement admixture is effective in securing sufficient working time, increasing the early, medium and long-term strength without inhibiting the hydration reaction of cement, promoting the coagulation and setting in steam curing as well as cold curing and increasing the strength of the cured product.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cement admixture and a cement composition. More specifically, it is intended to promote the strength of mortar or concrete and to enhance the strength thereof. In addition to general civil engineering / building structures, concrete The present invention relates to a cement admixture and a cement composition used for products and the like.

[0002]

[Prior art and its problems] Compared with the case of using ordinary Portland cement, the use of early-strength Portland cement or ultra-early-strength Portland cement can shorten the construction period for civil engineering / building structures, and concrete. Even in product factories, the demolding cycle of the formwork can be accelerated. However, there is a problem with the supply of early-strength Portland cement and ultra-early-strength Portland cement, and the present situation is that they are supplied only in limited regions.

Further, innumerable types and methods of salts have been conventionally known for promoting the setting and hardening of concrete. For example, a method of accelerating the setting and hardening of cement has been proposed in which calcinated alum, gypsum, and an organic acid such as citric acid, 2-ketogluconic acid, and tartaric acid, which are ion-sequestering retarders, are blended (JP-A-50). -6635). Further, in order to normalize the setting retardation of insoluble anhydrous gypsum, a method for producing high-strength concrete using aluminum sulfate in combination has also been proposed (JP-A-52-98730). However, in the former method, since the retarder used in combination is an organic acid, the hydration of the cement is delayed and the strength development is delayed if the amount of the retarder added is increased in an attempt to suppress the quick-setting property of the calcined alum and secure sufficient working time. There was a problem of being significantly delayed. In addition, the latter is simply used for the purpose of normalizing the setting retarding action of insoluble anhydrous gypsum, and in order to ensure workability, the addition amount is small, and the strength enhancing action cannot be expected. was there.

On the other hand, alkali metal aluminates and silicates are classically known as quick-setting agents for cement, like alkali metal carbonates, and are often used in sprayed concrete. When added alone, the addition of a small amount within a range that does not cause rapid setting has a small effect of increasing strength, and there is a problem that the medium- to long-term strength is rather lowered.

Further, a method of promoting hardening comprising aluminum sulfate and an alkali metal sulfate has been proposed (Japanese Patent Publication No. 63-291839). However, this method has not yet solved the problem of a decrease in long-term strength.

As a result of various studies to solve the above-mentioned problems, the present inventors have solved the above-mentioned problems by using a specific composition, and have achieved early, medium-term, and long-term use of cement. The present invention has been completed based on the finding that a cement admixture capable of increasing strength can be obtained.

[0007]

Means for Solving the Problems That is, the present invention is a cement admixture containing gypsum, an aluminum compound, an alkali metal sulfate, an alkali metal aluminate, and a setting regulator as an active ingredient, and further, a cement. And a cement composition comprising the cement admixture.

The present invention will be described in detail below.

Examples of the gypsum according to the present invention include type II anhydrous gypsum called insoluble or sparingly soluble, dihydrate gypsum, semi-aqueous gypsum, and soluble type III anhydrous gypsum, among which type II anhydrous gypsum is Most preferred is the use. Also, the fineness of gypsum is the Blaine specific surface area.
It is preferably 2,500 cm ² / g or more. When the fineness is less than 2,500 cm ² / g, when the amount of gypsum added is large, it remains in an unhydrated state, and there is a concern that it may expand in water for a long time. The amount of gypsum used is preferably 0.5 to 6 parts by weight, more preferably 1.0 to 5 parts by weight, and most preferably 1.5 to 4 parts by weight in terms of CaSO _{4 with} respect to 100 parts by weight of cement. If it is less than 0.5 parts by weight, the medium-long term strength tends not to grow, and if it exceeds 6 parts by weight, the early strength tends to decrease due to the delaying property of the gypsum.

Here, as the cement, various Portland cements, these Portland cements, slag,
Examples thereof include fly ash, various mixed cements mixed with silica and the like.

Examples of the aluminum compound according to the present invention include a sulfuric acid band and alumite. As the sulfuric acid band, a commercially available one can be usually used, and it is not affected by impurities normally contained.
Further, any of those containing anhydrous salt and water of crystallization can be used as they are. In addition, alum stone is a natural product, [(K, N
a) (Al, Fe) ₃ (SO ₄ ) ₂ (OH) ₆ ] shows the range of components, and raw alum stone powder crushed this and calcinated alum calcinated at 800 ° C or lower and crushed Stone powder is used. The fineness of the aluminum compound is not particularly limited, and a granular form or a rough form can sufficiently exert the effect. The amount of the aluminum compound used is preferably 0.4 to 4 parts by weight, more preferably 0.6 to 3.5 parts by weight, and most preferably 0.8 to 2.5 parts by weight, based on 100 parts by weight of cement, in terms of anhydride. If it is less than 0.4 parts by weight, early strength tends to be small, and if it exceeds 4 parts by weight, workability cannot be obtained.
Medium- to long-term strength tends to decrease.

The alkali metal sulfate according to the present invention has a function of enhancing early strength as a stimulant for a quick-setting agent for aluminum compounds such as a sulfuric acid band, and sodium sulfate, potassium sulfate and the like can be used. The amount of alkali metal sulfate used is 0.15 to 1 per 100 parts by weight of cement.
Weight part is preferable, 0.2-0.8 weight part is more preferable, and 0.
Most preferred is 3 to 0.5 parts by weight. If it is less than 0.15 parts by weight, the early strength tends to be small, and if it exceeds 1 part by weight, the medium to long-term strength tends to be low and the reactivity of the mortar or concrete with the alkaline aggregate tends to be high.

The alkali metal aluminate according to the present invention has a synergistic effect with the alkali metal sulfate and has an action of enhancing early strength as a stimulant of a quick-setting agent for an aluminum compound, such as sodium aluminate or aluminate. Potassium or the like can be used. The amount of alkali metal aluminate used is preferably 0.05 to 0.5 parts by weight, more preferably 0.1 to 0.4 parts by weight, and 0.15 to 100 parts by weight of cement.
Most preferred is 0.25 parts by weight. If it is less than 0.05 parts by weight, early strength tends to be small, and if it exceeds 0.5 parts by weight, medium
Long-term strength decreases, and it quickly sets, so it tends to be difficult to take work time.

As the coagulation regulator according to the present invention, an oxycarboxylic acid or a salt thereof is used, and examples thereof include gluconic acid, citric acid, tartaric acid, and NH ₄ , Na, K and Ca salts thereof. The use amount of the setting regulator is preferably 0.01 to 0.3 parts by weight, more preferably 0.03 to 0.2 parts by weight, and most preferably 0.05 to 0.1 parts by weight with respect to 100 parts by weight of cement.
If the amount is less than 0.01 parts by weight, work time tends to be difficult to obtain,
If it exceeds 0.3 parts by weight, the early strength tends to be low and the setting time tends to be long.

The cement admixture of the present invention is a general civil engineering
It can be used for soft kneading and hard kneading mortar or concrete used in the production of building structures and various concrete secondary products, as well as super hard kneading mortar or concrete for roller compacted concrete dams and roller compacted concrete paving. .

The mixing method and addition method of the concrete admixture of the present invention to concrete and the like are not particularly limited, but the respective components are mixed in powder form in advance, or the respective components are mixed. The ingredients alone,
It may be added to the mixer at the same time when the mortar or concrete is mixed, or each component may be added alone or as a suspension of a mixture.

[0017]

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

Example 1 Maximum size 25 mm, fine aggregate rate 40%, slump 10 ± 2.5 cm, air amount 2 ± 1%, and water / cement ratio 40%, water 160 kg /
m ^3, cement 400kg / m ^3, sand 727kg / m ^3, crushed stone 1,110kg / m ^3,
And 50 liters of concrete was prepared by using each unit amount of the water reducing agent 6.0 kg / m ³ and the slump temporal change and the compressive strength were measured in a room at 20 ° C. The results are shown in Table 1.
The cement admixture was prepared by mixing each component once in terms of anhydride when mixing the concrete, and lightly mixing it with the cement.

50 liters of concrete was kneaded by a forced kneading mixer for 3 minutes, and a sample for compressive strength test was molded in a cylinder of φ10 × 20 cm using a bar vibrator. The change with time of the slump was measured by taking about 30 liters of the kneaded concrete in a box, allowing it to stand, and kneading it back with a scoop when the time was up. The mold was cured for 24 hours, after which it was demolded, then cured in a room at 20 ° C, and the strength was measured when the age came.

<Materials used> Cement: Ordinary Portland cement manufactured by Denki Kagaku Kogyo Sand: Kawasago crushed stone from Niigata Prefecture Himekawa: 〃 Crushed stone water reducing agent: Denki Kagaku Kogyo's trade name "FT-500V" Naphthalene sulfonate gypsum : Type II anhydrous gypsum Aluminum compound A: Sulfuric acid band, industrial anhydrous aluminum sulfate 〃 B: Calcined alum, Alum from Shokoyama calcined at 650 ° C, crushed into branes 6,800 cm ² / g, purity 90% alkali Metal Sulfate: Industrial Sodium Sulfate Alkali Aluminate Metal Salt: Reagent Sodium Aluminate Coagulation Regulator: Reagent Sodium Citrate

[0021]

[Table 1]

Example 2 The procedure of Example 1 was repeated, except that the formulation shown in Table 2 was used. The results are also shown in Table 2.

[0023]

[Table 2]

Example 3 The procedure of Example 1 was repeated except that the formulation shown in Table 3 was used. The results are also shown in Table 3.

[0025]

[Table 3]

Example 4 The procedure of Example 1 was repeated, except that the formulation shown in Table 4 was used. The results are also shown in Table 4.

[0027]

[Table 4]

Example 5 The procedure of Example 1 was repeated, except that the formulation shown in Table 5 was used. The results are also shown in Table 5.

[0029]

[Table 5]

[0030]

EFFECTS OF THE INVENTION By using the cement admixture of the present invention, the working time is sufficiently secured, the hydration reaction of the cement is not impaired, and the strength of early, middle, and long term is enhanced, steam curing and normal temperature. Even during curing, it has the effect of accelerating the setting and hardening and increasing the strength.

Claims (2)

[Claims] 1. A cement admixture containing gypsum, an aluminum compound, an alkali metal sulfate, an alkali metal aluminate, and a setting regulator as active ingredients. 2. A cement composition comprising cement and the cement admixture according to claim 1.