JPH07247153A - Cement composition - Google Patents

Abstract

PURPOSE:To improve compression strength and flexural strength at an early period, a middle period and a long period, comprising specific cement, anhydrous gypsum, aluminum sulfate, an alkali metal aluminate and steel fibers. CONSTITUTION:100 pts.wt. of cement composed of >=60wt.% of 3CaO.SiO2, having 3,500-7,000cm<2>/g Blaine value is blended with 100 pts.wt. of total amount of 1-5 pts.wt. of anhydrous gypsum having 2,500cm<2>/g Blaine value, 0.2-3 pts.wt. (calculated as anhydride) of aluminum sulfate and 0.1-0.8 pt.wt. of an alkali metal aluminate and 5-25 pts.wt. of steel fibers having 29-80mm fiber length and 50-100 aspect ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a cement composition used in the civil engineering industry, particularly to a cement composition used for road paving.

[0002]

2. Description of the Related Art Conventionally, concrete used for road paving has a problem that a rut portion of a road becomes a groove, so-called "rut digging", which hinders the safety of vehicle running. .

This "rudder digging" is less likely to occur as the bending resistance of the concrete is higher, and in order to improve the bending resistance of the concrete, steel fiber reinforced concrete in which steel fibers are mixed with the concrete has been proposed ( Kazusuke Kobayashi, "Characteristics and Applications of Fiber Reinforced Concrete," 1981, 6
Published by Ohmsha Ltd.) However, the conventional concrete mixed with steel fiber has a problem that the initial strength development is poor.

In order to improve the strength development in the initial stage, steel fiber reinforced concrete using rapid hardening cement is used for the purpose of early release, especially in the case of construction in a place with heavy traffic, because of problems such as traffic congestion. Construction is increasing. However, the work time of steel fiber reinforced concrete using rapid hardening cement is extremely short, so it is not possible to carry out construction in the usual style of kneading with ready-mixed concrete and transporting it to the construction site with an agitator car, so it is a special construction machine. Since it requires a construction method in which kneading is performed on-site using a machine or equipment, continuous large-scale placement is impossible, and there are problems such as a significant increase in construction costs.

Therefore, at present, steel fiber reinforced concrete using rapid hardening cement has not been widespread except for special emergency works such as highways.

[0006] In recent years, instead of rapid-hardening concrete for the purpose of opening the road in a few hours, such as steel fiber reinforced concrete using rapid-hardening cement, a predetermined strength for opening the road in one day, For example, it can develop bending strength of 40 kgf / cm ² or more and compressive strength of 300 kgf / cm ² or more with standard curing at 20 ° C, and without using a special construction machine like quick-hardening concrete, it can be used in the ready-mixed concrete plant as before. There is an increasing demand for concrete that can be kneaded and that can be transported to the construction site by an agitator vehicle, that is, ultra-fast concrete.

As a result of various studies, the inventor of the present invention can use a specific cement composition to knead it with ready-mixed concrete and transport it to a construction site with an agitator car, which is excellent in bending resistance. The present invention has been completed based on the knowledge that early-hardening concrete can be obtained.

[0008]

[Means for Solving the Problems] That is, the present invention provides 3CaO · S
100 parts by weight of cement having an iO ₂ content of 60% by weight or more, 1 to 5 parts by weight of anhydrous gypsum, 0.2 to 3 parts by weight of aluminum sulfate as an anhydride, and 0.1 to 3 parts of alkali metal aluminate.
A cement composition containing 0.8 parts by weight and a steel fiber.

The present invention will be described in detail below.

The cement used in the present invention is 3CaO.SiO ₂
The content is 60% by weight or more, and the 3CaO.SiO ₂ content is preferably 66% by weight or more. If it is less than 60% by weight, sufficient initial strength may not be obtained. Usually, commercially available early-strength Portland cement can be used. The grain size of the cement is preferably 3,500 to 7,000 cm ² / g in terms of Blaine value, and more preferably 4,000 to 5,000 cm ² / g. If it is less than 3,500 cm ² / g, sufficient initial strength may not be obtained.
If it exceeds 0 cm ² / g, concrete slump loss may increase.

The anhydrous gypsum used in the present invention is not particularly limited as long as it is an anhydride, and naturally-occurring anhydrous gypsum, anhydrous gypsum obtained by heat treatment of hemi-water gypsum and dihydrate gypsum, It is also possible to use anhydrous gypsum or the like generated as an industrial by-product. The particle size of the anhydrous gypsum is preferably not less than 2,500 cm ² / g in Blaine value, 4,000 cm ² / g or more is more preferable. If it is less than 2,500 cm ² / g, expansion failure may occur due to unhydrated residual gypsum in the long-term age. The amount of anhydrous gypsum used is 1 to 5 parts by weight, preferably 3 to 4 parts by weight, based on 100 parts by weight of cement. If it is less than 1 part by weight, the initial strength is poorly expressed, and if it exceeds 5 parts by weight, expansion failure may occur due to unhydrated residual gypsum in the long-term age.

The aluminum sulfate used in the present invention is usually a salt having about 0 to 20 mol of bound water, and is not particularly limited, and any salt having bound water can be used. The amount of aluminum sulfate used is cement
The amount is 0.2 to 3 parts by weight in terms of anhydride with respect to 100 parts by weight, and preferably 1 to 2 parts by weight. If it is less than 0.2 parts by weight, the initial strength is poorly expressed, and if it exceeds 3 parts by weight, workability tends to be poor.

The alkali metal aluminate used in the present invention is indispensable for improving the early, medium and long-term strength development properties, and is not particularly limited in terms of its components. It is possible to use potassium aluminate, of which it is economically preferable to use sodium aluminate. The amount of alkali metal aluminate used is 0.1 to 0.8 parts by weight, preferably 0.3 to 0.8 parts by weight, based on 100 parts by weight of cement. If it is less than 0.1 part by weight, sufficient strength development may not be obtained, and if it exceeds 0.8 part by weight, workability may be deteriorated.

The steel fiber used in the present invention means a cut wire, a shear fiber, a cutting fiber, and a melt extraction fiber depending on the manufacturing method.
In the present invention, any fiber can be used, and commercially available products can be easily used, although they can be classified into types. The shape of steel fiber cannot be uniquely determined because it depends on the usage conditions, but it is necessary to select a shape that does not generate fiber balls due to poor dispersion during the kneading process. Is. Generally, it is preferable to use steel fibers having a fiber length of 20 to 80 mm and an aspect ratio of about 50 to 100. The amount of steel fiber used varies depending on the type, but is preferably 5 to 25 parts by weight with respect to 100 parts by weight of a binder composed of cement, anhydrous gypsum, aluminum sulfate, and alkali metal aluminate, 10
-20 parts by weight is more preferred. If it is less than 5 parts by weight, the reinforcing effect by the steel fiber is not sufficient, and if it exceeds 25 parts by weight, fiber balls tend to occur and breathing tends to occur easily.

As an apparatus for mixing the materials of the present invention,
Any existing stirring device can be used, for example, a tilting barrel mixer, an omni mixer, a V-type mixer, a Henschel mixer, and a Nauta mixer can be used. Further, the mixing may be carried out by mixing the respective materials at the time of construction, or by mixing a part or all of them in advance.

In the present invention, in addition to the above materials, a coagulation modifier, a water reducing agent, an AE water reducing agent, a high performance water reducing agent, a high performance AE water reducing agent, an AE agent, a thickening agent, an aggregate such as sand or gravel. , Cement rapid hardening materials, cement expansion materials, rust preventives, antifreeze agents, polymer emulsions, calcium compounds such as calcium oxide and calcium hydroxide, alkali metal sulfates, alkali metal sulfites, and alkali metal bisulfites Sulfates, clay minerals such as bentonite, ion exchangers such as zeolite, hydrotalcite, and hydrocalumite, inorganic phosphates, and boric acid, etc., or one or more of them is substantially the object of the present invention. It is possible to use in combination within the range where it does not inhibit.

[0017]

The present invention will be described in detail below with reference to examples.

Example 1 A binder composed of 4 parts by weight of anhydrous gypsum, 1 part by weight of aluminum sulfate and 0.5 part by weight of alkali aluminate salt was used per 100 parts by weight of cement shown in Table 1. Then, the unit amount in concrete is 500 kg of binder /
m ^3, (20 parts by weight relative to the binder 100 parts by weight) steel fibers 100 kg / m ^3, water 191kg / m ^3, fine aggregates 900 kg / m ^3, and coarse aggregate 689kg / m
³ and prepare concrete mixed with steel fiber, 15φ
A sample of × 30 cm was prepared and the compressive strength was measured. The results are also shown in Table 1.

<Materials used> Cement α: early strength Portland cement manufactured by Denki Kagaku Kogyo, 3CaO / SiO ₂ content 66% by weight, Blaine value 4,460 cm ² / g Cement β: Early strength Portland cement manufactured by Denki Kagaku Kogyo A mixture of 54 parts by weight and ordinary Portland cement 46 parts by weight, 3CaO / SiO ₂ content 60% by weight, Blaine value 3,870 cm ² /
g Cement γ: Ordinary Portland cement manufactured by Denki Kagaku Kogyo Co., 3CaO / SiO ₂ content 53% by weight, Blaine value 3,340 cm ² / g Anhydrous gypsum: Natural anhydrous gypsum, Blaine value 4,120 cm ²
/ g Aluminum sulfate: Powdered sulfuric acid band made by Mizusawa Chemical Industry Co., Ltd.,
Al ₂ O ₃ 17% by weight, water content 43% by weight Alkaline aluminate salt: sodium aluminate, reagent 1
Grade, Blaine value 3,690 cm ² / g Steel fiber: Kobe Steel Co., Ltd. trade name "Shinko fiber", 6φ x 30 mm fine aggregate: Niigata prefecture Himekawa sand, specific gravity 2.63 coarse aggregate: Niigata Himekawa gravel, Gmax = 20 mm, specific gravity 2.
67 Water: Tap water

<Test method> Compressive strength: Measured by making a specimen of 10φ × 20 cm

[0021]

[Table 1]

Example 2 Example 2 was repeated except that cement α was used and the amount of anhydrous gypsum was changed as shown in Table 2.
The results are also shown in Table 2.

[0023]

[Table 2]

Example 3 Cement α was used and the amount of aluminum sulfate used is shown in Table 3.
The same procedure as in Example 1 was performed except that the change was made as shown in FIG. The results are also shown in Table 3.

[0025]

[Table 3]

Example 4 Example 4 was repeated except that cement α was used and the amount of alkali metal aluminate used was changed as shown in Table 4. The results are also shown in Table 4.

[0027]

[Table 4]

Example 5 The same procedure as in Example 1 was repeated except that cement α was used and the amount of steel fiber used was changed as shown in Table 5. 15 × 15 ×
A 55 cm specimen was prepared and the bending strength was measured. The results are also shown in Table 5.

<Test method> Bending strength: Measured according to JIS A 1106

[0030]

[Table 5]

EFFECTS OF THE INVENTION By using the cement composition of the present invention, a road pavement concrete which exhibits good compressive strength and flexural strength in the early, middle and long term and can be opened in one day is obtained. To be

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Claims (1)

[Claims] 1. A cement having a 3CaO.SiO ₂ content of 60% by weight or more, 100 parts by weight, anhydrous gypsum 1 to 5 parts by weight, aluminum sulfate in an amount of 0.2 to 3 parts by weight in terms of anhydride, and an alkali metal aluminate salt. A cement composition comprising 0.1 to 0.8 parts by weight of C, and steel fiber.