JPH042642A - Cement composition for watertight concrete and production thereof - Google Patents

Abstract

PURPOSE:To obtain the title composition improved in kneadability and capable of enhancing the watertightness of the watertight concrete therefrom by incorporating a cement composition for watertight concrete comprising cement and noncrystalline silica fine powder with a water-reducing agent and classified fly ash of specified size. CONSTITUTION:Firstly, (A) a cement composition for watertight concrete comprising cement and noncrystalline silica fine powder is incorporated with (B) an appropriate amount of a water-reducing agent and (C) fly ash (a fine granular component obtained by direct classification, with a size <=20mum, of fly ash discharged during coal combustion). The resulting mixture is kneaded with aggregates and water to obtain the objective cement composition for watertight concrete.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is used, for example, in underground areas. The present invention relates to a cement composition for watertight concrete and a method for producing the same.

(Prior Art) In order to improve the watertightness of concrete, fine amorphous silica powder such as silica hneem is added to concrete materials such as cement.

According to this, amorphous silica takes in mixing water under alkaline conditions from cement hydration and forms a gel, filling microscopic voids in concrete and increasing the watertightness of concrete. .

(Problem to be Solved by the Invention) By the way, since such amorphous silica fine powder is a fine powder, it can fill the gaps formed in concrete, but at the same time, it is a fine powder. Therefore, it tends to aggregate easily.

Therefore, it is a difficult task to knead these fine amorphous silica powders so as to uniformly disperse and fill the gaps formed between cement particles, aggregates, etc. The watertight performance of this type of cement composition is not sufficient.

The present application has been made in view of these circumstances, and the first invention of the present application improves the watertight performance of watertight concrete having this type of amorphous silica fine powder, and facilitates good crosstalk. The object of the present invention is to provide a watertight cement composition for concrete.

Moreover, the second invention of the present application aims to provide a manufacturing method that can easily manufacture a cement composition for Kagaro watertight concrete having good watertight performance.

(Means for solving the problems) In order to achieve these objects, the first invention of the present application has the following features:
In a cement composition for watertight concrete containing cement and amorphous silica fine powder, an appropriate amount of water reducing agent and fly ash discharged during coal combustion are classified as they are to a particle size of 20 μm or less without crushing. , and the fine particles obtained through this classification.

Further, the second invention of the present application is to add an appropriate amount of a water reducing agent and fly ash to a cement composition for watertight concrete having cement and amorphous silica fine powder, and the fly ash is discharged during coal combustion. The fly ash that was
The particles are classified without being crushed to have a particle size of 20 μm or less, and the fine particles obtained by this classification are kneaded with aggregate and water.

(Function) According to the first invention of the present application, the diameter of 20 μm without being crushed
Since fly ash classified into the following particle sizes is added to the cement composition for watertight concrete having amorphous silica fine powder, the fly ash is The amorphous silica fine powder is located in the gaps between the fly ash particles and between the fly ash particles and the cement particles.

By adding the classified fly ash in this manner, the size of the gap to be filled with the amorphous silica fine powder becomes smaller, and aggregation of the amorphous silica fine powder is spatially suppressed.

Since an appropriate amount of water reducing agent is added to this cement composition, agglomeration of the amorphous silica fine powder is reduced, and the amorphous silica fine powder is well dispersed in the small gaps. Can be filled.

Therefore, the gaps between the particles of the cement composition are small, and the gaps are reliably filled with amorphous silica fine powder, so that the watertight performance is improved.

Further, as mentioned above, there is little fear of agglomeration of the amorphous silica fine powder having an extremely small particle size, and the amount of the amorphous silica fine powder used is small, so that good kneading can be easily performed.

Furthermore, according to the second invention of the present application, extremely watertight concrete can be reliably obtained by simply adding the required aggregate and water to the mixture such as cement and kneading it. It is easy to produce a cement composition for watertight concrete.

(Example) Examples will be described below.

The cement composition for watertight concrete of this example is:
A mixture of cement, fine amorphous silica powder, water reducing agent, and fly ash is mixed with the required aggregate and water.

In the examples below, the cement is ordinary Portland cement ~40 μm.

The amorphous silica fine powder is silica hneem, and has an average particle size of approximately 0.1 to 0.3 μm.

Note that granular silica fuyume having such a particle size may be used, and not only silica fuyume but also fine powder of other amorphous silica materials may be used.

The water reducing agent is a so-called high performance water reducing agent, which is an anionic surfactant, but an ordinary water reducing agent may also be used.

Fly ash is the fine particles obtained by classifying the fly ash discharged during coal combustion to a particle size of 20 μm without crushing it (hereinafter referred to as classified fly ash).

Most of the particles of this classified fly ash are small spherical, and their Blaine value is 55,000 m27g.
The average particle size is approximately 7.5 μm.

Note that the particle size of the classified fly ash to be classified is not limited to the above-mentioned 20 μm, but may be set as appropriate as long as it is 20 μm or less.

Using these materials, appropriate fine aggregate, coarse aggregate, and water are added to the mixture, kneaded, and hardened to form concrete having the structure shown in the drawing.

In the drawings, 1 is cement particles, 2 is classified fly ash particles, 3 is silica hneem, and 4 is fine aggregate.

In this concrete structure, since the particle size of each material is set as described above, basically, the gap S1 between the aggregate such as the fine aggregate 4, which is a thick particle, and the cement particles 1 The classified fly ash particles 2 with the next largest particle size are arranged within the silica ash particles 4, and the silica hneem 3 with the smallest particle size is arranged between these fine aggregates 4. The structure is filled in the small gap S2 formed between the cement particles 1 and the classified fly ash particles 2.

For the mixture consisting of the above-mentioned materials such as cement, various formulations described below are set, and appropriate amounts of coarse aggregate, fine aggregate, and water are added and kneaded for each of these formulations to form concrete, respectively. The physical properties of each concrete were measured.

The measurement results are shown in Tables 1 and 2.

(Margin below) Table, 1 Table, 2 In these tables, classification F/A means classified fly ash, sample numbers 4 to 8 are examples according to the present invention, and sample numbers 1 to 3 are comparative examples. It is.

Furthermore, it was decided that the performance of each formulation regarding the watertightness of concrete, which is the problem to be solved in this application, would be judged by a water permeability test and a carbonation acceleration test.

The water permeability test was conducted in accordance with JIS A 1404 using a pressurized water permeability tester at 15 kg/cm2.
A water permeability test was carried out for 24 hours and 72 hours at a water pressure of , and the results were expressed in volume %. In addition, the accelerated carbonation test is 3
3 under the conditions of 6℃, carbon dioxide concentration 5%, and humidity 70%.
The depth of carbonation after curing for one month was measured and displayed.

From the results shown in Tables 1 and 2, the following can be gleaned about the watertight performance of these concretes.

(1) In comparing sample numbers 3 and 4 with sample numbers 1 and 2, both sample numbers 3 and 4 are superior in both water permeability and neutralization depth, and have good watertight performance due to the addition of silica hneem. It is thought that this is exhibiting the following.

Sample numbers 3 and 4 differ only in the presence or absence of a high-performance water reducer, and are almost the same in terms of watertight performance of concrete.

However, since the cross-conducting work during the preparation of Sample No. 3 was relatively difficult, it is industrially realistic to use a high-performance water reducing agent.

(2) In comparing sample numbers 4 and 5, only the proportions of classified fly ash and cement are different, and the others are basically the same.

In terms of watertight performance, concrete is similar to Habo, but
Sample number 5 is superior in water permeability at 72 hours,
Sample No. 5 is considered to be more preferable for concrete requiring long-term watertight performance.

(3) Sample numbers 5 to 7 differ only in the amount of amorphous silica fine powder added, and in terms of water permeability and neutralization depth, the amount of amorphous silica fine powder added is is 6% or more, each concrete is considered to have equivalent watertight performance.

(4) Sample number 8 is based on the composition of sample number 5,
It has an increased proportion of classified fly ash compared to the proportion of classified fly ash and cement, and has an extremely high water permeability and extremely good watertightness.

From these measurement results, in the case of this example,
Internal grinding of cement with classified fly ash from 1° to 30% by weight
3 to 6 times of amorphous silica fine powder by external machining.
Highly watertight concrete can be stably obtained by adding 2 parts by weight and also adding a water reducing agent or a high performance water reducing agent and kneading.

The reason why such results were obtained regarding the watertight performance of concrete is considered to be that each of the above-mentioned materials of the cement composition for watertight concrete functioned as follows in each example (hereinafter referred to as drawings). reference).

■ Functions and Effects of Classified Fly Ash Since the particles of classified fly ash are uniformly spherical with a small diameter, they easily roll into and fill the gaps s1 between cement particles.

When the classified fly ash enters the gap S1 between the cement particles, the moisture present therein is pushed out and functions as mixing water, so that the unit water amount of concrete can be reduced.

When fly ash is neutralized with the calcium silicate content of cement under alkaline conditions, tobermorite gel is produced, which improves the watertightness of concrete and increases its strength.

Furthermore, by using the classified fly ash, the classified fly ash particles 2 are positioned in the gaps S1 between the cement particles 1, and the silica huneem 3 fills the minute gap S2 formed by the classified fly ash particles 2, so the silica hneem 3 The aggregation of 3 is spatially suppressed.

And compared to the case without using classified fly ash,
The amount of expensive silica neem 3 to be used can be reduced to about a fraction of that, and the workability of the kneading operation is improved.

■ Functions and effects of silica hneem By using silica hneem 3, which is a fine amorphous silica powder, it fills the minute gap S2 formed between the cement particles 1 and the classified fly ash particles 2. , the moisture present in this gap S2 is expelled, and a water reduction effect can be obtained accordingly.

In addition, since the silica hneem 3 is filled into the minute gap S2 and hardened, the structure of the concrete is densified and the watertightness and strength are further improved.

And ζ such silica hneem 3 has a large surface area,
Due to its high reactivity with water, watertightness and strength develop rapidly.

■ Functions and effects of high-performance water reducing agent Since the high-performance water reducing agent is used, it suppresses agglomeration of Silica Funeem 3, which is amorphous silica fine powder, and makes it easier to fill the minute gap S2 as described above. Improves cross-wire workability.

When applying watertightness to concrete with a construction thickness of 30cm or more, the water-use heat of the cement accumulates inside the concrete, causing cracks in the concrete due to thermal distortion, and these cracks destroy the watertightness of the concrete. Sometimes.

However, according to the present invention, since classified ply ash is added, the amount of cement used is small and the amount of heat generated is small.

In addition, the presence of the classified fly ash particles 2 disperses the cement particles 1, which serve as a heat source, and prevents the formation of high-temperature areas due to local uneven distribution of cement, thereby reducing the occurrence of cracks due to thermal strain. It has the advantage of being able to

When producing a cement composition for watertight concrete using a mixture of such cement, etc., the required aggregate and water are added to the above-mentioned mixture, and the mixture is simply kneaded in the same way as in a normal case, resulting in an extremely watertight concrete composition. Since it is possible to reliably obtain concrete with high water-tightness, it is easy to produce a cement composition for watertight concrete.

(Effects of the Invention) As explained above, according to the first invention of the present application, fly ash classified into particle sizes of 20 μm or less without being crushed can be used for watertight concrete containing fine amorphous silica powder. Since the fly ash particles are added to the cement composition, the fly ash particles are located in the gaps formed between the cement particles, and the gaps between the fly ash particles and between the fly ash particles and the cement particles are The amorphous silica fine powder is located there.

By adding the classified fly ash in this manner, the size of the gap to be filled with the amorphous silica fine powder becomes smaller, and aggregation of the amorphous silica fine powder is spatially suppressed.

Since an appropriate amount of water reducing agent is added to this cement composition, agglomeration of the amorphous silica fine powder is reduced, and the amorphous silica fine powder is well dispersed in the small gaps. Can be filled.

Therefore, the gaps between the particles of the cement composition are small, and the gaps are reliably filled with amorphous silica fine powder, so that the watertight performance is improved.

Further, as mentioned above, there is little fear of agglomeration of the amorphous silica fine powder having an extremely small particle size, and the amount of amorphous silica fine powder used is small, so that good crosstalk can be easily achieved.

Furthermore, according to the second invention of the present application, it is possible to reliably obtain concrete with extremely high watertightness by simply adding the required aggregate and water to a mixture such as cement and kneading it. It is easy to produce a cement composition for watertight concrete.

[Brief explanation of the drawing]

The drawing is a model diagram of the concrete structure of the example. 1; Cement particles, 2; Classified fly ash particles, 3;
Silica hneem (fine amorphous silica powder), 4; fine aggregate. Applicant: Shikoku Research Institute Co., Ltd. Engraving of drawings (no changes in content) ) Commissioner of the Japan Patent Office August 30, 1990 1. Indication of the case 1990 Patent Application No. 102233 2. Name of the invention Cement composition for watertight concrete and its manufacturing method 3. Person making the amendment Related Applicant Name: Shikoku Research Institute Co., Ltd. (1 other person) 4, Agent: 135 Phone: 03-820-1811 Address:
1-14-36 Monzennakacho, Koto-ku, Tokyo Contents of amendment Corrections will be made as per the engraving of the drawing and attached sheet (no changes to the content)

Claims (2)

[Claims] (1) In a cement composition for watertight concrete containing cement and amorphous silica fine powder, an appropriate amount of water reducing agent and fly ash discharged during coal combustion can be directly mixed with a particle size of 20 μm or less without being crushed. 1. A cement composition for watertight concrete, characterized in that the fine particles obtained in the classification are added. (2) An appropriate amount of water reducing agent and fly ash are added to a cement composition for watertight concrete containing cement and fine amorphous silica powder, and the fly ash is created by crushing the fly ash discharged during coal combustion. A method for producing a cement composition for watertight concrete, characterized in that the fine particles obtained by this classification are classified as they are without any separation to a particle size of 20 μm or less, and the fine particles are kneaded with aggregate and water. .