JPH059045A - Super fast hardening type cement composition - Google Patents

Abstract

PURPOSE:To provide a super fast hardening concrete with high initial strength excellent in workability and durability, etc. CONSTITUTION:The super fast hardening cement composition is obtained by incorporating 2-10 pts.wt, in terms of CaSo4, hemihydrate gypsum and/or anhydrous gypsum with 100 pts.wt,. of a Portland cement containing 60-75wt.% Ca silicate (C3S), and has 5000-7000cm<2>/g the fineness of the prescribed Portland cement in a Blaine specific area and 6000-8000cm<2>/g the fineness of the prescribed gypsum in a Blanie specific area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a super early strength type cement composition which is excellent in workability and durability.

[0002]

[Prior Art and its Problems] Currently, in the construction requiring high strength of concrete such as erection of PC girder, road repair, construction for urgent rotation of formwork, etc. Hard cement is used.

However, since early-strength Portland cement has insufficient early-strength, it is not possible to expect a significant reduction in the construction period of the entire construction. Super early strength Portland cement has good strength development, but it has poor workability due to the large slump loss of concrete. In addition, although ultra-fast cement can obtain practical strength in a short time, it takes a very short time to harden and it cannot be manufactured at a ready-mixed concrete plant and transported to the construction site.
As a result, it can only be used for very small works. In addition, ultrafast cements are very costly, limiting their use.

Therefore, a method of adding hemihydrate gypsum and / or anhydrous gypsum to the cement has been proposed as a method for improving the strength, slump loss, etc. in the cement as described above, particularly for increasing the initial strength of the concrete. There is.

However, in the method of adding hemihydrate gypsum and / or anhydrous gypsum, the fineness is usually as small as about 6000 cm ² / g or less in terms of Blaine specific surface area, and the addition amount is as large as about 10% by weight with respect to the cement. I am using
Except in the case of steam curing, there is a problem in that unreacted gypsum causes expansion in water and the like to cause cracks in the molded body, resulting in deterioration of durability.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a super early strength type cement composition which is excellent in workability and durability.

That is, the present invention provides calcium silicate (C
₃ S) The content of hemihydrate gypsum and / or anhydrous gypsum is 2 to 10 parts by weight in terms of CaSO ₄ with respect to 100 parts by weight of Portland cement having a content of 60 to 75% by weight, and the fineness of the Portland cement is Brane ratio. 5000 in surface area
~7000cm a ² / g, in which and according to an ultra high-early-strength cement composition, wherein the fineness of the gypsum is 6000~8000cm ² / g in Blaine specific surface area.

The present inventors have conducted extensive studies to solve the above problems, particularly the above-mentioned adverse effects caused by unreacted gypsum, and as a result, increased the content of calcium silicate (C ₃ S) in cement, and further, By increasing the fineness of cement and the fineness of gypsum to be added to increase the reaction activity of cement and gypsum, unreacted gypsum remains even if the addition amount of gypsum is increased as in the case of steam curing. The inventors have found that the reaction of gypsum is completed in the initial stage of hydration without any matter, and completed the present invention.

The present invention will be described in detail below.

As the cement used in the present invention, Portland cement containing 60 to 75% by weight of calcium silicate (C ₃ S) is used. If the content of calcium silicate is less than 60% by weight, sufficient initial strength cannot be obtained even if the fineness of the cement is increased, and if it exceeds 75% by weight, the firing temperature of the cement becomes high and the productivity decreases. Problems such as deterioration of quality stability occur. The fineness of the above cement is 5000-7000c in terms of Blaine specific surface area.
m ² / g. If the fineness is less than 5000 cm ² / g, sufficient initial strength cannot be obtained even if the amount of calcium silicate in the cement is increased, and if it exceeds 7,000 cm ² / g, the initial strength is well expressed, but the slump loss of concrete is high. Is relatively large and the crushing cost is extremely high, which is not preferable. The fineness can be adjusted by various crushing devices such as a normal ball mill.

As the hemihydrate gypsum and / or anhydrous gypsum to be added to the cement, those produced by a conventional method may be used, and CaS is added to 100 parts by weight of the cement.
Add 2 to 10 parts by weight in terms of O ₄ . If the amount added is less than 2 parts by weight, the effects of promoting the initial strength development and reducing slump loss are not sufficient, and if the amount added exceeds 10 parts by weight, unreacted gypsum remains and the durability is reduced. To do. The fineness of the Blaine specific surface area is 6000 to
A material having a fineness of 8000 cm ² / g is used. On the case where the fineness is less than 6000 cm ² / g is insufficient effect of promoting early strength development, gypsum unreacted tends to remain, 8000 cm ² / g and is in extreme grinding costs when exceeded This is not preferable because it increases the cost and raises the production cost.

The method of adding and mixing the above-mentioned hemihydrate gypsum and / or anhydrous gypsum into the above cement may be carried out according to a conventional method, for example, various mixing devices such as a ribbon mixer.

In the case of using the super early-strength cement composition of the present invention, for example, when producing concrete, the composition is designed according to the application in accordance with a conventional method, and water, a predetermined aggregate,
And various additives such as a high performance water reducing agent may be kneaded and molded.

[0014]

EFFECTS OF THE INVENTION According to the present invention, it is possible to provide a super early-strength concrete having high workability and durability and a high initial strength, and it is possible to shorten the construction period of concrete work in the construction industry and the like. ..

[0015]

EXAMPLES Examples, comparative examples and reference examples will be shown below to further clarify the features of the present invention. In each of the examples, comparative examples and reference examples, concrete was manufactured with the concrete mix (1 to 3) as shown in Table 1.

[0016]

[Table 1]

[0017]

EXAMPLE 1 calcium silicate was contained 65 wt% of anhydrous its Blaine specific surface area relative to Portland cement (manufactured by Osaka Cement Co.) 100 parts by weight of 5910cm ² / g, the Blaine specific surface area of 7110cm ² / g 5 parts by weight of gypsum was added and kneaded to produce concrete.
The high performance water reducing agent in Table 1 is "Mighty 2000WH".
(Manufactured by Kao Corporation) was used.

Next, as a material test of the obtained concrete, the results of aging of slump (composition No. 2), compressive strength for 1 day of age, and observation of cracking after underwater curing for 3 months are shown. Shown in the table.

[0019]

Examples 2 to 3 The same procedure as in Example 1 was carried out except that the amount of hemihydrate gypsum and / or anhydrous gypsum and the fineness (Blaine specific surface area) were changed. Further, the same test as in Example 1 was conducted on the obtained concrete. The results are shown in Table 2.

[0020]

[Table 2]

[0021]

[Comparative Examples 1 and 2] In Comparative Example 1, the fineness (Blaine specific surface area) of hemihydrate gypsum and / or anhydrous gypsum was outside the scope of the present invention, and in Comparative Example 2, the amount of hemihydrate gypsum and / or anhydrous gypsum added. Was carried out in the same manner as in Example 1 except that was outside the scope of the present invention. The results are shown in Table 3.

From the results shown in Table 3, since the fineness of the gypsum to be added in Comparative Example 1 is smaller than the range of the present invention, the strength development is smaller than that of the example in which the gypsum with a high fineness is added, and It can be seen that cracking occurred during curing and the durability was poor. Similarly, in Comparative Example 2 in which the amount of gypsum added was excessive (12%), cracking occurred during underwater curing and it was found that durability was poor.

[0023]

[Comparative Examples 3 to 7] Without adding hemihydrate gypsum and / or anhydrous gypsum, each cement having a composition as shown in Table 2 was kneaded to produce concrete. Further, the same tests as in Example 1 were conducted on each of the obtained concretes. The results are shown in Table 3.

[0024]

[Table 3]

[0025]

[Table 4]

From the results shown in Table 3, it can be seen that the slump loss is large and the workability is inferior as compared with those of the examples to which hemihydrate gypsum and / or anhydrous gypsum are added. In particular, Comparative Example 3 using a cement containing less calcium silicate than the range of the present invention has a smaller strength development than Comparative Examples 4 and 5 containing calcium silicate of the present invention. .. Also. Comparative Example 6
It is understood that the cement used has a fineness smaller than the range of the present invention, and the strength development is smaller than that of Comparative Example 7 using the fineness within the range of the present invention.

[0027]

Reference Example 1 Commercially available early strength Portland cement (manufactured by Osaka Cement Co., Ltd.) was kneaded to produce concrete, and the same test as in Example 1 was conducted. The results are shown in Table 4.

[0028]

[Reference Example 2] Commercially available super early strength Portland cement (manufactured by Osaka Cement Co., Ltd.) was kneaded to produce concrete, and the same test as in Example 1 was performed. The results are shown in Table 4.

[0029]

[Table 5]

As is clear from the results shown in Table 4, the early strength Portland cement of Reference Example 1 has a small strength development, and the super early strength Portland cement of Reference Example 2 has a large slump loss.

From the above results, the super early strength type cement composition of the present invention is excellent in strength development, small in slump loss,
Furthermore, it is clear that excellent effects can be exhibited in terms of durability.

[0032]

Claims (1)

Claims: 1. Calcium silicate (C ₃ S) content 60 to 7
Hemohydrate gypsum and / or anhydrous gypsum is added to 2 parts by CaSO ₄ conversion to 100 parts by weight of Portland cement which is 5% by weight.
10 to 10 parts by weight, and the fineness of the Portland cement is 5000 to 7000 cm ² / g in terms of Blaine specific surface area.
And the fineness of the gypsum is 6 in terms of Blaine specific surface area.
000-8000 cm < ² > / g, The super early strength type cement composition characterized by the above-mentioned.