JP2011001210A - Method of producing hydraulic composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a hydraulic composition capable of suppressing the generation of cracks, pop-out or the like by a simple and easy way in a method of producing the hydraulic composition.SOLUTION: The present invention is related to a method of producing a hydraulic composition. The method of producing a hydraulic composition containing cement and an expansive additive comprises: producing a cement composition in which the expansive additive is dispersed and contained excessively to the cement so that a ratio becomes β, where α>β, when a ratio of a mass of the cement in a total mass of the cement and the expansive additive in the hydraulic composition to be produced is α; and adjusting the ratio so as to become α by newly adding cement when the cement composition is mixed with water to produce the hydraulic composition.

Description

  The present invention relates to a method for producing a hydraulic composition, for example, a reinforced concrete structure, a reinforced concrete structure, a reinforced steel concrete structure, a prestressed concrete structure, etc. (hereinafter collectively referred to as “RC structure etc.”). It is related with the preparation method of the hydraulic composition containing the expansion | swelling material excellent in the effect which suppresses the crack resulting from the drying shrinkage | contraction which becomes an initial defect, self-shrinkage, and temperature shrinkage.

In recent years, from the viewpoint of reducing life cycle costs in the civil engineering and construction fields, there has been a demand for improved durability of RC structures and the like.
In order to improve the durability of such RC structures, it is effective to prevent cracks, which are initial defects, and it is known that the main causes of such cracks are dry shrinkage, self-shrinkage, and temperature stress. It has been.
Therefore, in RC structures and the like, it is required to suppress cracks due to drying shrinkage, self-shrinkage and temperature stress in the initial curing process.

In response to such a demand, conventionally, an expanding material has been widely used for the purpose of giving an appropriate expansion during curing of concrete or the like.
In particular, recently, an expansion material has been developed that exhibits the same performance (expansion rate) as the conventional one with a usage amount of about two-thirds of the conventional one.
Such a high-performance expansion material is also referred to as a “high-performance expansion material” in distinction from an expansion material having normal performance (hereinafter also referred to as “normal expansion material”). No. 2 describes technical matters regarding this high-performance expansion material.

JP 2002-226243 A JP 2003-063847 A

“Reduction of self-shrinkage of ultra-high-strength concrete”, Annual report of concrete engineering, Vol. 27, no. 1, 2005, p. 1099-1104

It can be said that the use of the expansion material as described above is extremely effective in suppressing cracks caused by drying shrinkage, self-shrinkage and temperature stress.
However, when using normal expansion materials and high-performance expansion materials in general raw plants, in addition to the increase in the unit price of materials, a dedicated supply / metering device for expansion materials is required. It must be thrown in by human power, which is a costly situation.
Moreover, measures such as extending the kneading time are necessary when producing a hydraulic composition such as concrete, and from this point of view, the production unit price in a raw plant is increased.
Furthermore, when the expansion material is introduced, the expansion material is fixed to the liner or blade in the mixer alone, and if it is mixed in the concrete as a lump, there is a risk of pop-out.
Due to these problems, the promotion of the spread of the expansion material has been stopped, and the use in the raw plant has not been generalized.

  Then, this invention makes it a subject to produce the hydraulic composition which can suppress generation | occurrence | production of a crack, popout, etc. by the simple method in the preparation method of a hydraulic composition.

For the above problems, it is considered as an effective measure to use a cement composition in which an expansion material is dispersed in cement (hereinafter also referred to as “expanded cement”).
In the expanded cement, since the expanded material is dispersed in the cement in advance, the expansion of the expanded material in the hydraulic composition may be unevenly distributed to suppress the possibility of pop-out.

By the way, it is known that in the hydraulic composition such as concrete, when the amount of the unit expansion material changes, the expansion coefficient also changes.
On the other hand, since the expanded cement contains the expanded material and the cement at a constant mass ratio, the unit expanded material amount is determined simultaneously by determining the unit cement amount in the hydraulic composition. Become.
Therefore, when using an expanded cement, for example, it is difficult to control the expansion coefficient of the hydraulic composition to be produced within a predetermined range (for example, 150 to 250 × 10 ⁻⁶ for shrinkage compensation). And may cause problems such as a decrease in strength due to excessive addition of the expansion material.

  In particular, when the ratio of water binder is small and the amount of unit cement is large, it is possible that the above-mentioned non-strength may cause a decrease in strength due to delayed expansion (a phenomenon that occurs after the formation of a hardened concrete). It has been pointed out in Patent Document 1 and the like, and it is strongly required to contain a necessary amount of an expanding material in a sufficiently dispersed state.

In order to prevent the above problems, when making expanded concrete by mixing expanded cement and water together with aggregates etc., it is also possible to make up for the lack of expanded material in expanded concrete by adding a new expanded material. Conceivable.
However, in that case, if the expansion material is not sufficiently dispersed, there is a risk of causing problems such as pop-out in the cured body.

As a result of intensive studies paying attention to such a method of using expanded cement, the present inventors have completed the present invention.
That is, the present invention relating to a method for producing a hydraulic composition for solving the above problems is a method for producing a hydraulic composition containing cement and an expansion material, When the ratio of the cement mass to the total mass of the cement and the expansion material in the composition is α, the expansion material is dispersed, and the expansion is performed so that the ratio is β (where α> β). A cement composition containing an excessive amount of material relative to the cement is prepared, and the ratio is adjusted to α by newly adding cement when mixing the cement composition and water. It is characterized by producing a hydraulic composition.

In the present invention, when the ratio of the cement mass to the total mass of the cement and the expansion material in the hydraulic composition to be produced is α, the expansion is performed so that the ratio is β (where α> β). A hydraulic composition is prepared by preparing a cement composition containing a material in excess relative to the cement.
That is, when the cement composition is contained in the hydraulic composition so as to have the required unit expansion material amount, the amount of cement will be insufficient, but this shortage will be compensated by later addition of cement. The unit expansion material amount and unit cement amount of the hydraulic composition can be adjusted to desired values.

Moreover, since the cement composition in which the expansion material is dispersed in advance is used, the mixing time required for dispersion can be shortened compared to the case where the expansion material itself is added during mixing.
In the present invention, cement is added at the time of kneading, but the effort required to disperse the cement to such an extent that it does not affect the cured body is slightly less than the effort to disperse the expansion material. Therefore, the influence on the entire mixing process is small.
Accordingly, it is possible to suppress the dispersion of the expansion material from becoming non-uniform while shortening the mixing time as compared with the case where the expansion material itself is added at the time of mixing.

From such a viewpoint, without adding cement at the time of kneading, each time a hydraulic composition is prepared, cement and an expanding material are mixed at a predetermined ratio to prepare an expanded cement. The same effect can be obtained, but in this case, the number of times of mixing and mixing the cement and the expansion material is increased as compared with the present invention.
That is, according to this invention, the outstanding effect that the hydraulic composition which can suppress generation | occurrence | production of a crack, popout, etc. can be produced with a simple method will be exhibited more notably.

The schematic diagram which showed the equipment structure used for the preparation methods of the hydraulic composition of one Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings by taking expanded concrete as an example of the hydraulic composition. explain.

First, the equipment to be used will be described.
FIG. 1 schematically shows an expanded concrete production facility according to the present embodiment, and an expanded cement silo 11 containing expanded cement in which an expanded material and cement are mixed and dispersed in advance. The expanded concrete production facility 1 used in the present embodiment produces general fresh concrete, except that it is attached to a normal cement silo 12 containing normal cement that does not contain an expanded material. Not very different from the equipment.

That is, the expanded concrete manufacturing facility 1 used in the present embodiment includes an expanded cement silo 11, a normal cement silo 12, an aggregate silo 21, and an admixture tank 31, and the expanded cement silo 11 and the normal cement silo. A cement meter 41 for weighing the expanded cement and the normal cement respectively supplied from the silo 12 is provided.
The expanded concrete production facility 1 further includes a fine aggregate meter 42 and a coarse aggregate meter 43 for measuring fine aggregate and coarse aggregate supplied from the aggregate silo 21 through the belt conveyor 22. ing.
Furthermore, the expanded concrete manufacturing equipment 1 in this embodiment includes a water meter 44 for measuring water for mixing cement and aggregate, and an admixture meter for measuring the admixture supplied from the admixture tank 31. 45.

The cement meter 41, the fine aggregate meter 42, the coarse aggregate meter 43, the water meter 44, and the admixture meter 45 are each a collecting hopper arranged at the lower part thereof. It is arranged so that it can be dropped into 51 and supplied to a mixer 61 for mixing.
The mixer 61 accommodates cement, aggregate, admixture, water, and the like through an upper opening connected to the opening of the lower chute 51a of the collecting hopper 51, and, for example, a stirring mechanism such as a biaxial stirring blade After the kneading, the lower damper is opened, and the hydraulic composition produced by kneading can be supplied to the agitator track 81 through the feeding hopper 71 provided below the mixer 61. Is provided.

In the method for producing expanded concrete using the expanded concrete production facility 1 having such a configuration, first, a step of preparing a cement composition (hereinafter also referred to as “expanded cement”) including cement and an expanded material is performed. This is very important.
This expanded cement can be produced in advance by mixing and dispersing cement and an expanding material at a predetermined ratio.

  The cement used to constitute the expanded cement is not particularly limited, and is usually various early Portland cements such as early strength, very early strength, moderate heat, low heat Portland cement, blast furnace cement, silica cement and fly ash cement. And various cements available on the market such as white Portland cement and alumina cement. These expanded cements can be used alone or in admixture of two or more.

Moreover, the expansion | swelling material for comprising an expansion | swelling cement is not specifically limited, Arbitrary expansion | swelling materials can be used.
Examples of the expansion material include lime-based expansion materials such as quick lime, ettringite-based expansion materials such as calcium sulfoaluminate, ettringite-lime composite expansion materials, iron powder-based, magnesium-based, and aluminum powder. These expanded cements can be used alone or in admixture of two or more.
Among these, an expansion material generally called a low addition type expansion material is suitable.
The low addition type expansion material is, for example, a uniaxial constrained expansion test (Appendix 2) when a performance test based on JIS A6202 “Concrete expansion material-1997” is performed with a unit expansion material amount of 20 kg / m ^3. The value of Method A) is usually 150 × 10 ⁻⁶ or more and 250 × 10 ⁻⁶ or less, and the expansion performance is improved when used in combination with blast furnace cement.

About the ratio of the cement and the expansive material used for producing the expanded cement, the proportion of the cement mass is lower than the proportion of the cement mass in the total amount of the cement and the expansive material in the expanded concrete to be produced. If set, there is no particular limitation.
That is, when the proportion of the cement mass in the total amount of the cement and the expanded material in the expanded concrete is α mass% and the proportion of the cement in the expanded cement is β mass%, the relationship of α> β is satisfied. If it has become like this, the ratio of the cement and expansion | swelling material in expansion concrete will not be specifically limited.

In addition, when producing a plurality of expansive concretes having different designs using the expansive concrete production facility 1, an expansive concrete having the smallest cement ratio (the ratio of the expansive material is large) among the plural expansive concretes. It is preferable to use it as a reference.
That is, when the proportion of cement mass in the total amount of cement and expansive material in the expanded concrete with the smallest proportion of cement is γ mass%, the proportion β in the expanded cement satisfies the relationship of γ> β. It is preferable to make it.
In this way, based on the expanded concrete with the smallest proportion of cement, for example, when producing expanded concrete with a different design, the desired unit can be obtained simply by adjusting the amount of normal cement added during mixing. An expanded concrete having a cement amount and a unit expanded material amount can be produced, and the work can be simplified.

However, if the expansion material is contained excessively, it is necessary to add a large amount of cement in order to adjust the ratio of the cement and the expansion material later.
For this reason, in terms of easily obtaining expanded concrete that is highly useful in the formation of RC structures and the like, the weight ratio of the expandable material as described above to the expanded cement is 6.5 mass% or more and 7.3 mass%. % Or less is preferable.
That is, the value of the ratio (β) in the expanded cement composition composed of cement and an expanded material is preferably 92.7% or more and 93.5% or less.

The method for producing the expanded cement is not particularly limited, and a general means for mixing powders can be employed.
For example, a method of dispersing the expansion material in the expansion cement by stirring and mixing the cement and the expansion material with a mixing device used in a cement manufacturing plant or the like can be mentioned.

  In addition, about the normal cement added later in order to produce expanded concrete, the cement illustrated previously can be utilized as a component which comprises expanded concrete.

And
(1) a step of supplying the expanded cement to the cement meter 41 through the cement supply path L1 by pneumatically feeding the expanded cement from the expanded cement silo 11, and storing the predetermined amount in the cement meter 41;
(2) supplying the fine aggregate from the belt conveyor 22 to the fine aggregate measuring instrument 42 through the fine aggregate supply path L2 and storing the fine aggregate in the fine aggregate measuring instrument 42;
(3) supplying the coarse aggregate to the coarse aggregate measuring instrument 43 through the belt conveyor 22 or the coarse aggregate supply path L3 and storing the coarse aggregate in the coarse aggregate measuring instrument 43;
(4) a step of allowing the water meter 44 to store a predetermined amount of water through the water supply path L4;
(5) A step of storing a predetermined amount of the admixture in the admixture meter 45 through the admixture supply line from the admixture tank,
(6) a step of supplying the normal cement to the cement meter 41 through the cement supply path L1 by pneumatically feeding the normal cement from the normal cement silo 12, and storing the cement meter in a predetermined amount;
After each of these steps, each of these weighed materials is kneaded with a mixer 61 to produce expanded concrete.

At this time, in a process (1), the compounding quantity of an expansion cement is determined based on the unit expansion material amount of the expanded concrete to produce, and the measurement based on this compounding quantity is implemented.
And the expanded cement contains the cement content only at β mass%, which has a smaller proportion of cement, if the proportion of the cement mass in the total amount of cement and expanded material in the expanded concrete to be produced is α mass%. Therefore, the difference is calculated to determine the normal cement amount in step (6).
Determination of the amount of fine aggregate, coarse aggregate, admixture and water in the steps (2) to (5) may be determined based on the unit amount of expanded concrete.

The fine aggregate, coarse aggregate, and admixture used here are not particularly limited, and those generally used for constituting concrete can also be used in this embodiment. For example, as fine aggregate Can use well-known materials, such as river sand, mountain sand, land sand, crushed sand, sea sand, silica sand No. 3-7 fine fine aggregate, or fine powder such as silica powder, limestone powder, etc. Can be used.
Further, for example, known coarse aggregates such as limestone, gravel, and crushed stone can be used as the coarse aggregate, and JIS A 6204 such as AE agent, water reducing agent, high-performance AE water reducing agent can be used as the admixture. It is possible to use chemical admixtures specified in 1.

The order of the steps (1) to (6) and the timing of mixing by the mixer 61 are not particularly limited.
That is, in the present invention, “adding a new cement when mixing a cement composition and water” means that a new cement is added at a desired timing before the start of mixing of the “expanded cement” and water. This includes the case where it is added and the case where a new cement is added immediately after the start of kneading.
For example, after performing step (1) and step (6), supplying a predetermined amount of expanded cement and normal cement to the mixer 61 and not adding water, and once kneading, (2) to The expanded concrete can be produced by carrying out the step (5) and supplying aggregate and water to the mixer 61 and kneading them with the mixer 61.
Or all the processes of (1)-(6) are implemented, all the materials are supplied to the mixer 61, knead | mixed, and an expanded concrete can also be produced.
Furthermore, it is not limited to these, As long as an expanded cement and cement do not remain | survive as a big lump in concrete, an expanded concrete can be produced in various procedures.

  In the kneading, since the expansion material is preliminarily dispersed inside the expansion cement, the expansion material is made uniform by performing a process of dispersing the cement and the aggregate in a general concrete manufacturing method. It is possible to produce expanded concrete dispersed in the slab.

That is, in the conventional method of adding the expansion material at the time of mixing, a long mixing time is required to prevent the expansion material from becoming uneven and causing problems such as pop-out. In the method according to this embodiment, since the expanded cement in which the expanded material is dispersed in advance is used, the mixing time can be shortened.
As described above, in the method for producing expanded concrete according to the present embodiment, the expanded concrete capable of suppressing the occurrence of cracks, pop-outs, and the like can be produced by a simple method.

In this embodiment, expanded concrete is exemplified as the hydraulic composition. However, the present invention is intended for hydraulic compositions such as mortar not containing coarse aggregate and cement paste not containing aggregate. It is the range to do.
Further, in the present embodiment, in the point that the calculation of the amount of the expanded cement to be weighed first and the amount of cement to be added later can be easily performed, a normal material which does not contain an expanding material as cement to be added later. The case of adding cement (with a cement content of 100% by mass) is illustrated, but it is also possible to use an expanded cement having a higher cement content than the expandable material instead of ordinary cement. .
For example, if the proportion of cement mass in the total amount of cement and expansive material in expanded concrete is α mass%, and the proportion of cement in the expanded cement used first is β mass%, then the proportion of cement Is also within the intended scope of the present invention when an expanded cement is used that is contained in a state of less than 100 mass% and greater than α mass%.
That is, the cement ratio is α mass by using the expanded concrete satisfying the relationship of δ mass% (where 100>δ> α) and the expanded concrete whose ratio is β mass% (where α> β). % Hydraulic composition is also within the intended scope of the present invention.
Although details are not illustrated here, conventionally known technical matters can be appropriately employed to produce a hydraulic composition as long as the effects of the present invention are not significantly impaired.

  EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.

(Evaluation methods)
Evaluation about the preparation method of a hydraulic composition was performed using the expanded concrete of the mixing | blending shown in Table 1.

(Examples 1-3)
Each of the compounds shown in Table 1 as blends 1 to 3 was mixed in an actual plant over 40 seconds after the entire amount was added, and the resulting expanded concrete was used in method A of JIS A6202 Annex 2 (reference). The expansion rate was measured over 7 days.
Further, the compressive strength according to JIS A1108 was measured. In addition, the measurement was implemented with respect to what performed standard water curing from 2 days after implantation, and the compressive strength in material age 3 days, 7 days, and 28 days was measured.
Furthermore, the block body produced using the obtained expanded concrete was produced, and surface observation was implemented in order to confirm the generation | occurrence | production presence or absence of pop-out over 3 months.
In Examples 1 to 3, an expanded cement prepared by previously mixing ordinary Portland cement and a low additive expansion material at a mass ratio of 93.3: 6.7 was used.

Example 4
Except that the mixing time was reduced from 40 seconds to 25 seconds, an expanded concrete was prepared in the same manner as in Example 2, and the expansion rate and the compressive strength were measured to confirm the occurrence of pop-out.

(Comparative Examples 1-4)
Although it is the same thing as the mixing | blending content 1-3, the expansion concrete is produced like Example 1-4 except having set it as the aspect (mixing 4-6) which added the expansion | swelling material at the time of kneading. Then, the expansion rate and the compressive strength were measured to confirm the occurrence of pop-out.

As can be seen from the comparison between Examples 1 to 3 and Comparative Examples 1 to 3 in Table 2, the results of Examples 1 to 3 are superior in terms of expansion coefficient and compressive strength as compared with Comparative Examples 1 to 3. Has been obtained.
Further, even when the kneading time was shortened to 25 seconds (Example 4), the expansion coefficient and the compressive strength equivalent to those of Comparative Example 2 in which the expansion material was added during kneading and kneading for 40 seconds were obtained. It can be seen from Table 2.
On the other hand, in the case where the expansion material is mixed at the time of kneading (Comparative Example 4), when the kneading time is shortened to 25 seconds, changes in the expansion rate and compressive strength are relatively slight, but popped out to the block specimen. Occurrence was observed.

  From the above, it can be seen that according to the present invention, in the method for producing a hydraulic composition, a hydraulic composition capable of suppressing the occurrence of cracks and pop-outs can be produced by a simple method.

DESCRIPTION OF SYMBOLS 1 Expanded concrete production equipment 11 Expanded cement silo 12 Normal cement silo 21 Aggregate silo 22 Belt conveyor 31 Admixture tank 41 Cement meter 42 Fine aggregate meter 43 Coarse aggregate meter 44 Water meter 45 Admixture meter 51 Collecting hopper 51a Lower chute 61 Mixer 71 Supply hopper 81 Agitator truck

Claims (2)

A method for producing a hydraulic composition containing cement and an expansion material,
When the ratio of the cement mass to the total mass of the cement and the expansion material in the hydraulic composition to be produced is α, the expansion material is dispersed and the ratio is β (where α> β). As described above, the expansion material is excessively contained with respect to the cement, and the ratio becomes α by newly adding cement when mixing the cement composition and water. A method for producing a hydraulic composition, characterized in that a hydraulic composition is produced by adjusting the composition as described above.   The method for producing a hydraulic composition according to claim 1, wherein a weight ratio of the expansion material to the cement composition is 6.5% by mass to 7.3% by mass.

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