JPH08198646A - Cement for steam curing product - Google Patents

Abstract

PURPOSE: To produce a cement for a steam curing product excellent in strength manifesting property by mixing a portland cement and a gypsum dihydrate which are separately ground so that a prescribed particle size may be obtained. CONSTITUTION: In (A) a portland cement clinker having a hydraulic ratio of 2.15-2.35 and 3800-5000cm<2> /g particle size by Blaine specific surface area and (B) the gypsum dihydrate having 4000-5000cm<2> /g particle size by Blaine specific surface area which are separately ground, the B component is mixed to the A component so that the B component may be <=2.6% per A component expressed in terms of SO3 to obtain the cement for the steam curing product.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cement for steam curing products which is mainly used in the field of secondary concrete products and has excellent strength development.

[0002]

2. Description of the Related Art Conventionally, cement compositions for steam-curing products and high-strength admixtures have been used to improve the strength when manufacturing concrete secondary products by steam-curing. As the cement composition, there is one disclosed in JP-A-59-30740 which defines various ratios of cement clinker, and as an admixture, it is disclosed in JP-A-56-149358 mainly containing anhydrous gypsum. There is something like this. As shown in these, when steam curing, commercially available normal Portland cement or early-strength Portland cement alone, or these as the matrix cement, and use by adding an admixture mainly of anhydrous gypsum-based material Was common.

[0003]

However, when an admixture mainly composed of anhydrous gypsum-based material is used, in order to obtain a sufficient effect of steam curing, high-strength Portland cement is used as the cement and the unit cement amount is 400 kg / m ³ or more, since it is necessary to the steam curing temperature 70 to 80 ° C.,
It was not suitable in cost for general products by casting. Further, when the admixture is used, the strength development is improved, but the amount of SO _{3 in} the cement becomes excessive and there is a risk that the stability will be impaired by expansion. Furthermore, since the admixture is not specified in JIS, the product using the admixture cannot be certified as a JIS product, and therefore, a separate public inspection must be performed when the product is shipped. There were many inconveniences, including the effort and expense involved.

In view of the above-mentioned problems, the inventors of the present invention have made it possible to use general casting secondary products among concrete secondary products without using admixtures mainly composed of anhydrous gypsum-based materials. As a result of intensive studies on the cement for steam curing products, which has the same sufficient strength as the above, and the product using the cement is JIS standard product, it was crushed separately to have a predetermined fineness. The present inventors have found that a cement composed of a mixture of Portland cement clinker and gypsum dihydrate is sufficient, and have completed the present invention.

[0005]

[Means for Solving the Problems] That is, according to the present invention, the separately pulverized hydraulic modulus is 2.15 to 2.35, and the fineness is 3,800 to 5,500 cm ² / Blaine specific surface area.
g of Portland cement clinker and 2.6% or less in terms of SO ₃ with respect to the clinker, and ² having a fineness of Blaine specific surface area of 4,000 to 5,000 cm ² / g.
It is a cement for steam curing products that is mixed with water gypsum.
Hereinafter, the present invention will be described in detail.

The Portland cement clinker of the present invention is pulverized alone so that its hydraulic modulus is 2.15 to 2.35 and its fineness is 3,800 to 5,500 cm ² / g in terms of Blaine specific surface area. Must be If the hydraulic modulus is less than 2.15, practically sufficient strength cannot be obtained, and if it exceeds 2.35, the viscosity during kneading becomes high,
The clinker manufacturing cost is also high. As for the fineness, if the Blaine specific surface area is less than 3,800 cm ² / g, practically sufficient strength cannot be obtained, and if it is more than this, the higher the specific surface area, the higher the strength obtained, but if it is too large, Workability is poor and manufacturing cost is high.
00 cm ² / g or less is preferable.

On the other hand, the gypsum added to and mixed with the clinker is dihydrate gypsum, and the fineness is 4,00 in terms of Blaine specific surface area.
The content is 0 to 5,000 cm ² / g, and must be pulverized alone so as not to be semi-hydrated, and the amount added to the clinker must be 2.6% or less in terms of SO ₃ .

Semi-water in the form of gypsum in cement, or
As the proportion of anhydrous gypsum increases, the strength decreases with the same fineness and the same composition. If the Blaine specific surface area is less than 4,000 cm ² / g, sufficient strength cannot be obtained. If the Blaine specific surface area exceeds 5,000 cm ² / g, the strength does not increase even if the specific surface area is increased. However, it is not good because it will lead to semi-waterification and cost will increase.

The addition ratio of dihydrate gypsum to the above-mentioned Portland cement clinker is 2 to 3% in terms of SO _3, which shows the highest strength. However, by making it less than 2.6%, it becomes a JIS standard ordinary Portland cement. Can fit. Therefore, the most preferable amount is 2.0 to 2.6% in terms of SO ₃ .

The cement for steam curing products of the present invention can be obtained by mixing the above-mentioned Portland cement clinker and dihydrate gypsum. The reason why both should not be mixed and pulverized is that most of the dihydrate gypsum is semi-hydrated due to heat and impact during pulverization, which reduces the strength. Water sprinkling in a mill is a method for suppressing the semi-hydration of dihydrate gypsum in mixed pulverization.
Not only is the semi-hydration of dihydrate gypsum suppressed, but cement reacts with water to form a hydrate on the surface of the cement particles, which lowers the initial strength development of the cement, which is not preferable.

The crushing device and the mixing device for obtaining the cement of the present invention are not particularly limited, and the conventional cement manufacturing device can be applied as it is. Although the cement of the present invention can obtain sufficient strength by itself, it does not prevent the use of various conventionally used admixtures (materials), and if necessary, admixture of AE water reducing agent, high performance water reducing agent, etc. Agent (material)
You may use together. The steam curing is preferably performed at 60 to 65 ° C. for 2 hours, but since the strength development is good, the curing time can be shortened and the curing temperature can be lowered. Hereinafter, the present invention will be described more specifically based on Examples.

[0012]

【Example】

(1) Material used ○ Gypsum ・ Drained dehydrated gypsum (manufactured by Nippon Cement Co., Ltd.) ・ Semihydrate gypsum: 2 water heated at 150 ° C for 3 hours ・ Hydrofluoric acid byproduct anhydrous gypsum (manufactured by Daiichi Cement Co.) ○ Commercial cement ・ Nihon Cement Ordinary Portland cement made by the company ○ Aggregate-Fine aggregate: Ome crushed sand (specific gravity: 2.61 FM: 2.89) -Coarse aggregate: Oume crushed stone (specific gravity: 2.64 FM: 7.06 Gma
x: 20 mm) ○ Admixture (material) -AE water reducing agent: Pozzolis No. 70 (manufactured by NMB) ・ AE auxiliary agent: 303A (manufactured by NMB) ・ Asano Supermix: Anhydrite-based high-strength admixture for steam curing products (manufactured by Nippon Cement Co., Ltd.)

(2) Trial production of cement 20 kg / 1 batch of the clinker described above in a 710 mmφ × 730 mm batch type ball mill and 400 mm of gypsum.
Using a batch type ball mill of φ × 450 mm, 4 kg / 1 batch was pulverized to the fineness shown in Table 1 and 500 mm × 670 so that the gypsum was 2% in terms of SO ₃ with respect to the clinker.
40 mm mm batch type mixer (Ledige mixer)
kg / 1 batch was mixed for 5 minutes, and each cement was trial-produced.

(3) Concrete experiment Using each cement produced as a trial, slump = 8 ± 1.0%,
s / a = 44%, W / C = 50%, air volume = 4.5 ±
Concrete was kneaded with a forced kneading mixer (0.05 m ³ ) under a mixing condition of 1.5% and AE water-reducing agent added = 0.25% to prepare a concrete specimen of φ10 × 20 cm according to JIS A1132. For comparison, a commercially available ordinary Portland cement and a mixture in which a high-strength admixture was used as the base cement were also prepared in the same manner. Steam curing conditions are as follows: pre-curing at 20 ° C for 3 hours,
The temperature was raised to 65 ° C. at a heating rate of 20 ° C./h, held for 2 hours, and then lowered to 20 ° C. in 9 hours and 45 minutes. Immediately after steam curing, the mold was removed and a strength test was performed according to JIS A 1108. The results are shown in Table 1.

[0015]

[Table 1]

When the hydraulic modulus was less than 2.15 as shown in Experiments 1 to 3, when the Blaine value of the clinker was lower than the range of the present invention as shown in Experiments 4 and 7, 2 water was obtained as shown in Experiment 10. When the Blaine value of gypsum is lower than the range of the present invention,
Further, as shown in Experiments 13 to 15, only with the gypsum form other than dihydrate gypsum or with the commercially available cement, sufficient demolding strength as in the case of mixing the high strength admixture for steam curing products was not obtained.

[Reference Experiment] Specimen size 4 × 4 × with W / C = 50% using cements with different hemihydrate rates of 2 gypsum
Mortar of 16 cm was molded, pre-cured at 20 ° C. for 2 hours and 30 minutes, heated at a heating rate of 20 ° C./h, and then heated at 60 ° C. for 1 hour.
It was kept for 45 minutes and steam-cured at 20 ° C. for 9 hours and 45 minutes. After demolding, the compressive strength was measured. As a result, it was found that the strength decreased as the semi-hydration progressed.
(Fig. 1)

[0018]

EFFECTS OF THE INVENTION By using the cement for steam curing product of the present invention, compared to the commercially available Portland cement, a large steam curing effect can be obtained even without using an admixture mainly composed of anhydrous gypsum-based material. It is possible to obtain an excellent secondary concrete product for casting. Furthermore, the obtained product is JIS
Since it is a standard product, there will be no inconvenience such as having to undergo official inspection at the time of product shipment.

[Brief description of drawings]

FIG. 1 shows the relationship between the semi-hydration ratio of dihydrate gypsum and the compressive strength of mortar immediately after demolding after steam curing.

Claims (2)

[Claims] 1. A water hardness of 2.15 to 2.35 and a fineness of Blaine specific surface area of 3,800 to 5,500 cm.
^A cement for steam curing products, which comprises a mixture of ² / g Portland cement clinker and 2.6% or less of dihydrate gypsum in terms of SO _{3 with} respect to the clinker. 2. Portland cement clinker and dihydrate gypsum are separate pulverized products, and the fineness of dihydrate gypsum is 4,000 to 5,000 cm ² / blaine specific surface area.
The cement for steam curing products according to claim 1, wherein the cement is g.