JP2020200200A - Method for producing additive for cement - Google Patents

Abstract

To provide a method for producing an additive for cement, in which a start time (setting time) of hydration reaction is substantially the same as when addition is not performed, and maximum arrival temperature after temperature rises due to the hydration reaction can be reduced.SOLUTION: A method for producing an additive for cement includes the following steps (1) to (3): a step (1) of covering a setting retarder for cement with a coating agent that is insoluble or poorly soluble in water at 5 to 50°C, to obtain a covered body; a step (2) of cleansing the covered body with a water-containing cleansing fluid; and a step (3) of drying the cleansed covered body, and then solidifying the dried covered body to obtain the additive for cement.SELECTED DRAWING: None

Description

The present invention relates to a method for producing an additive for cement.

When constructing large-capacity concrete (mass concrete) such as dams and piers, heat generation due to the hydration reaction of cement causes a temperature difference between the inside and outside of the concrete, which may cause cracks in the concrete.

Conventionally, as a control method of this heat of hydration, cooling of the material used, pipe cooling after placing cement concrete, use of an admixture such as fly ash, and use of an admixture such as an endothermic agent or a hydration reaction inhibitor of cement. It has been known.

Among these methods for controlling heat of hydration, as a hydration reaction inhibitor, for example, a heat hydration inhibitor capsule in which microcapsules are impregnated with a liquid condensation retarder and coated with a wax having an appropriate melting point has been proposed. (See, for example, Patent Documents 1 to 3).

Japanese Unexamined Patent Publication No. 10-81552 Japanese Unexamined Patent Publication No. 2000-327382 Japanese Unexamined Patent Publication No. 2005-289718

In the heat hydration suppressing capsules disclosed in Patent Documents 1 to 3, a part of the heat hydration suppressing agent is also attached to the outside of the capsule from the manufacturing process. Therefore, even when the heat hydration suppression capsule is used, the start time of the hydration reaction may be delayed. Therefore, it may take time to harden and develop strength of the concrete structure.

An object of the present invention is to provide a method for producing an additive for cement, in which the start time (condensation time) of the hydration reaction is almost the same as that in the case of no addition, and the maximum temperature rise due to the hydration reaction can be lowered. It is to be.

As a result of diligent studies on the above problems, the present inventors have found that the above problems can be solved by coating the cement setting retarder, washing with a cleaning liquid, and then drying, and have completed the present invention. It was.
That is, the present inventors provide the following [1] to [4].
[1] A method for producing an additive for cement, which comprises the following steps (1) to (3).
Step (1): A step of coating a cement setting retarder with an insoluble or sparingly soluble coating agent in water at 5 to 50 ° C. to obtain a coating material.
Step (2): A step of cleaning the covering body with a cleaning liquid containing water.
Step (3): A step of drying and solidifying the washed coating body to obtain an additive for cement.
[2] The method for producing a cement additive according to the above [1], wherein the cement setting retarder is a solid substance.
[3] The method for producing an additive for cement according to the above [1] or [2], wherein the coating agent is an organic compound having a melting temperature of 60 ° C. or higher.
[4] The method for producing an additive for cement according to any one of the above [1] to [3], wherein the cleaning time is 1 to 30 minutes in the step (2).

According to the present invention, there is provided a method for producing an additive for cement, in which the start time (condensation time) of the hydration reaction is almost the same as that in the case of no addition, and the maximum temperature rise due to the hydration reaction can be lowered. can do.

FIG. 1 is a chart showing the relationship between the elapsed time from water injection and the temperature rise.

Hereinafter, the present invention will be described in detail according to its preferred embodiment. In this specification, the notation "AA to BB" shall indicate AA or more and BB or less.

[1. Manufacturing method of additives for cement]
The method for producing an additive for cement of the present invention has the following steps (1) to (3).
Step (1): A step of coating a cement setting retarder with an insoluble or sparingly soluble coating agent in water at 5 to 50 ° C. to obtain a coating material.
Step (2): A step of cleaning the covering body with a cleaning liquid containing water.
Step (3): A step of drying and solidifying the washed coating material to obtain an additive for cement.
The details of each step will be described below.

[1-1. Process (1)]
The step (1) is a step of coating the cement setting retarder with an insoluble or sparingly soluble coating agent in water at 5 to 50 ° C. to obtain a coating material. By coating the cement setting retarder with a coating agent to obtain a coating, it is possible to suppress the delay in the start time (condensing time) of the hydration reaction during cement preparation.

(Cement setting retarder)
Examples of the setting retarder for cement include gluconates such as sodium gluconate and calcium gluconate; water-soluble polymers such as lignin sulfonate, cellulose derivatives, polyvinyl alcohol, dextrin, and sodium polyacrylate; citric acid. Organic acids having hydroxyl groups such as diketoglutaric acid, carboxy groups, and carbonyl groups; saccharides such as glucose and sorbitol; silica fluorides and phosphates.
The setting retarder for cement includes a solid substance and a liquid substance, and the solid substance is preferable from the viewpoint of coating with a coating agent, sodium gluconate, calcium gluconate, a cellulose derivative, and sodium polyacrylate are more preferable, and glucon. Sodium acid and calcium gluconate are more preferable.

(Dressing agent)
The coating agent is a compound that is insoluble or sparingly soluble in water at 5 to 50 ° C., and an organic compound having a melting temperature of 60 ° C. or higher is preferable. If the compound is insoluble or sparingly soluble in water at 5 to 50 ° C., the cement setting retarder remains contained immediately after being added to the cement, delaying the start time (condensing time) of the hydration reaction. Can be suppressed. Further, when the melting temperature is 60 ° C. or higher, when the hydration reaction proceeds and the cement temperature rises due to the heat of hydration, the coating agent melts and releases the cement setting retarder, and the cement becomes The temperature can be reduced. The upper limit of the melting temperature may be not more than the maximum temperature reached by the hydration reaction, and is usually 80 ° C. or less.
Here, "insoluble or sparingly soluble in water at 5 to 50 ° C." means that 1 g of the dressing is immersed in 100 mL of water at 5 to 50 ° C., allowed to stand for 1 day, and then recovered. It means that the mass of the dried dressing is 90% or more of the mass of the dressing before being immersed in water.

More specifically, the coating agent includes wax, paraffin wax, microwax, fat and oil, fatty acid, fatty acid ester, metal soap, higher alcohol, and thermoplastic resin. Among these, wax and paraffin wax, which have an easy melting point control, are preferable.

(Coating method)
The method of coating with a coating agent is not particularly limited, and a conventionally known method can be used. Examples thereof include an interfacial polymerization method, an In-Situ method, an insolubilization reaction method, a core selvation method, a submerged drying method, a spray drying method, a fluidized bed method, and an ultrasonic method. More specifically, it can be carried out by adding a preheated cement setting retarder to the molten coating agent and slowly cooling the mixture while kneading with a hovert mixer or the like. After slow cooling, excessive particles may be removed by sieving.

The ratio of the amount of the cement setting retarder to the coating agent used (cement setting delay agent: coating agent) is preferably 70 to 95:30 to 5. Within such a range, a coating material containing a cement setting retarder in a coating agent can be prepared.

[1-2. Process (2)]
The step (2) is a step of cleaning the covering body obtained in the step (1) with a cleaning liquid containing water. By cleaning the covering body with a cleaning liquid, the cement setting retarder adhering to the outside of the covering body can be washed. Therefore, the delay in the start time (condensation time) of the hydration reaction due to the cement setting retarder adhering to the outside of the coating can be suppressed, and the start time (condensation time) of the hydration reaction can be almost the same as in the case of no addition. .. In addition, the maximum temperature in the cement due to the hydration reaction can be reduced as compared with the case of no addition or the case of blending the conventional heat hydration suppressing capsule. This suppresses temperature unevenness due to the hydration reaction in the vicinity of the coating and other parts when the cement setting retarder is not attached to the outside of the coating, and as a result, it is uniform throughout the cement. It is presumed that this is because it can be expected to suppress the temperature rise. Further, when the cement setting retarder is not attached to the outside of the covering, the setting delay due to the initial hydration reaction does not occur, so that the temperature of the whole is uniformly raised to reach the melting temperature of the covering material. Therefore, it can be expected that the effect of the retarding agent is uniformly exhibited, and as a result, the hydration reaction temperature can be suppressed.
On the other hand, in the conventional heat hydration suppression capsule, there is a concern that the heat hydration inhibitor attached to the capsule surface or partially exposed from the capsule begins to affect the hydration reaction immediately after the addition and induces a delay in coagulation. is there. In addition, compared to the vicinity of the capsule, the temperature rises due to the heat of hydration in other places, and even if the heat of hydration suppression capsule dissolves and releases the heat of hydration inhibitor, the part not near the capsule There is a concern that it is insufficient to suppress the heat of hydration. Therefore, it is difficult to obtain a uniform suppression of temperature rise, and there is a concern that the initial strength after curing may decrease. Furthermore, in conventional heat hydration-suppressing capsules, the retarder that adheres to or is exposed to the surface of the capsule can affect the initial hydration reaction and cause a delay in coagulation. Therefore, it is not desirable because it affects the initial strength reduction of the cured product.
Therefore, the cement additive produced by the method for producing a cement additive of the present invention suppresses a decrease in the start time (condensation time) of the hydration reaction due to the action of the cement condensation inhibitor adhering to the outside of the coating. At the same time, it has an unexpected and advantageous effect that the maximum temperature reached by the temperature rise due to the hydration reaction can be lowered.

(Cleaning liquid)
The cleaning liquid may be any cleaning liquid containing water, and a cleaning liquid containing water as a main component is preferable, and water is more preferable. As the water, tap water, industrial water, ion-exchanged water or the like may be used. However, industrial water is preferable in view of cost and the purpose of cleaning the cement coagulation inhibitor adhering to the outside of the coating.
The cleaning liquid may contain lower alcohols such as methanol and ethanol, acetone and the like in addition to water as long as the coating agent is not dissolved. In this case, the content of water in the cleaning liquid is preferably 50% by mass or more, more preferably 80% by mass or more.

(Washing method)
The cleaning method is not particularly limited as long as it can clean the cement setting inhibitor adhering to the outside of the covering. For example, the covering body may be immersed in a container filled with a cleaning liquid for cleaning, or the cleaning liquid may be showered and applied to the covering body for cleaning. As a cleaning method, a method of immersing the coating material in a container filled with a cleaning liquid is preferable from the viewpoint of cleaning the cement coagulation inhibitor adhering to the outside of the coating material with good industrial reproducibility. At this time, the cleaning liquid may be agitated and the cleaning liquid may be run water (drained together with the water supply). However, when cleaning is performed by such a method, the covering is placed in a net cage from the viewpoint of preventing the covering from being damaged due to contact with the stir bar of stirring and the covering from being released together with running water. It is preferable to keep it.

The cleaning time is not particularly limited as long as the cement setting inhibitor adhering to the outside of the coating can be cleaned. For example, in the case of a method of immersing the covering body in a container filled with a cleaning liquid, 10 seconds to 30 minutes is preferable, and 1 to 30 minutes is more preferable. When the washing time is 10 seconds to 30 minutes, the cement setting inhibitor adhering to the outside of the covering can be washed, and the cost increase due to the use of an excessive amount of water can be suppressed.
The temperature of the cleaning liquid may be any temperature as long as it does not melt the coating agent, and is preferably normal temperature.

[1-3. Process (3)]
The step (3) is a step of drying and solidifying the washed covering body to obtain an additive for cement. The cement additive obtained in the step (3) has the effect of the present invention because the cement coagulant does not adhere to the outside of the coating body.

The drying method is not particularly limited as long as the coating agent is not dissolved. For example, it may be dried under reduced pressure or naturally dried in air.

[2. Method of suppressing heat of hydration]
Hereinafter, a method for suppressing heat of hydration using the method for producing an additive for cement of the present invention will be described. The method for suppressing heat of hydration can be applied to a cement material containing at least cement and water [1. It is a method of adding the cement additive described in [Cement Additive]. Since the above-mentioned cement additive is used in the method for suppressing heat of hydration, it can be applied to ordinary concrete compounding, and the start time (condensation time) of the hydration reaction is almost the same as that in the case of no addition, and it depends on the hydration reaction. The maximum temperature reached for temperature rise can be lowered, and high-strength concrete can be produced.

[2-1. Cement material]
The cement material contains at least cement, water, and may include aggregate. In addition, [1. It may contain other cement additives (hereinafter, also referred to as “other admixtures”) other than the cement additives described in [Cement Additives].
The cement is not particularly limited. For example, Portoland cement (normal, early-strength, ultra-fast-strength, moderate heat, sulfate-resistant and each low-alkali form), various mixed cements (blast furnace cement, silica cement, fly ash cement), white Portorand cement, alumina cement, Ultra-fast-hardening cement (1 clinker fast-hardening cement, 2 clinker fast-hardening cement, magnesium phosphate cement), grout cement, oil well cement, low heat-generating cement (low-heat-generating blast furnace cement, fly ash mixed low-heat-generating blast furnace cement, belite High-content cement), ultra-high-strength cement, cement-based solidifying material, and eco-cement (cement manufactured from one or more of municipal waste incineration ash and sewage sludge incineration ash). Fine powders such as blast furnace slag, fly ash, cinder ash, clinker ash, husk ash, silica fume, silica powder, and limestone powder, gypsum, and the like may be added to the cement.

The water that can be used as the cement material is not particularly limited, and examples thereof include tap water, water other than tap water (river water, lake water, well water, etc.), and recovered water.

Aggregates include, for example, sand, gravel, crushed stone; granulated slag; recycled aggregate, etc .; silica stone, clayey, zirconite, high alumina, silicon carbide, graphite, chromium, chromog, magnesia And other refractory aggregates.

In the method for suppressing heat of hydration, the ratio of water to cement (water / cement) (mass ratio) is not particularly limited, and it can be widely used from poor to rich compounds. The unit water amount is preferably 135 to 195 kg / m ³ , and more preferably 145 to 185 kg / m ³ . The amount of cement used is preferably 220 to 1200 kg / m ³ , and more preferably 270 to 700 kg / m ³ . The water / cement ratio (mass ratio) is preferably 0.15 to 0.7, more preferably 0.25 to 0.65.

The content ratio of the cement additive is usually 0.01 to 0.50% by mass, preferably 0.02 to 0.30% by mass, and more preferably 0.04 with respect to the total amount of cement. ~ 0.20% by mass. By setting this amount, the maximum temperature reached by the temperature rise due to the hydration reaction can be lowered, and high-strength concrete can be produced.
In the present specification, the "total amount of cement" refers only to the mass of cement (including the binder), and does not include the mass other than the binder such as water and aggregate.

There are no particular restrictions on the method of manufacturing, transporting, placing, curing, managing, etc. the cement material, and ordinary methods can be adopted.

Other admixtures include, for example, cement dispersants, water-soluble polymers, polymer emulsions, cement wetting agents, swelling agents, waterproofing agents, thickeners, flocculants, drying shrinkage reducing agents, strength enhancers, curing accelerators. For known cements such as agents, defoamers, AE agents, surfactants, water reducing agents, high-performance water reducing agents, AE water reducing agents, high-performance AE water reducing agents, fluidizing agents, pumping aids, low thixotropy aids, etc. Additives can be mentioned.
The other admixture may be used alone or in combination of two or more other admixtures at an arbitrary ratio.

Examples of the cement dispersant include dispersants such as naphthalene sulfonic acid formaldehyde condensate and melamine sulfonic acid formaldehyde condensate.

Examples of the water-soluble polymer include polyalkylene glycol. More specifically, polyethylene glycol, polypropylene glycol, polyethylene polypropylene glycol, polyethylene polybutylene glycol and the like can be mentioned.

Examples of the curing accelerator include soluble calcium salts such as calcium chloride, calcium nitrite and calcium nitrate; chlorides such as iron chloride and magnesium chloride; thiosulfates; and formates such as formic acid and calcium formate.

Examples of the thickener include methyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, known cellulose nanofibers, and known cellulose nanocrystals.

As the defoaming agent, a commercially available product may be used. For example, "Floric DF753" manufactured by Floric Co., Ltd. can be mentioned.

Examples of the low thixotropy aid include "Floric FBL-200" manufactured by Floric.

Examples of the high-performance AE water reducing agent include "Floric SF500S" manufactured by Floric.

Hereinafter, the present invention will be described in detail with reference to Examples. The following examples are for the purpose of preferably explaining the present invention, and do not limit the present invention. Unless otherwise specified, the method for measuring the physical property value or the like is the measurement method described above.

[Melting temperature (° C.)]: The melting temperature was measured using MP-80 (manufactured by METTLER TOLEDO).

(Example 1)
Paraffin (melting temperature 70 ° C) liquefied by heating to 100 ° C is added to sodium gluconate that has been preheated to about 70 ° C (sodium gluconate: paraffin = 86: 14) and kneaded with a hovert mixer. While slowly cooling to room temperature, a coating was obtained. After slow cooling, a coarse covering of about 1 mm or more was excluded by a sieve (Sato type vibrating sieve, manufactured by Koei Sangyo Co., Ltd.).

After excluding the coarse covering of about 1 mm or more, the net cage containing the covering was immersed in a container filled with industrial water at room temperature for 15 minutes. At this time, the industrial water in the container was agitated using a magnetic stirrer, and the industrial water was continuously run (drained together with the water supply).
After 15 minutes, the net cage was taken out of the container and left in a well-ventilated place to dry to produce the cement additive (1).

(Comparative Example 1)
Paraffin (melting temperature 70 ° C) liquefied by heating to 100 ° C is added to sodium gluconate that has been preheated to about 70 ° C (sodium gluconate: paraffin = 86: 14) and kneaded with a hovert mixer. While slowly cooling to room temperature, a coating was obtained. After slow cooling, a coarse covering of about 1 mm or more was excluded by a sieve (Sato type vibrating sieve, manufactured by Koei Sangyo Co., Ltd.). In this way, the cement additive (2) was produced.

The paraffin used in Examples and Comparative Examples is paraffin (melting point 68 to 70 ° C.) (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) and is insoluble or sparingly soluble in water at 5 to 50 ° C.

(Performance verification)
At the environmental temperature (20 ° C.), cement (bonding material), water, and aggregate were mixed so as to be in each formulation shown in Table 1, and a high-performance AE water reducing agent was added. Then, it was mechanically kneaded with a mortar mixer for 60 seconds at low speed and 90 seconds at high speed to obtain a cement composition. In Comparative Example 2, the temperature rise was measured using the cement composition. For Example 1 and Comparative Example 1, the temperature rise was measured by separately adding the cement additive (1) or (2) to the cement composition.
The temperature rise was measured at the temperature at the center of the sample, using the cement composition as a cubic sample having a side of 40 cm. At this time, the circumference of the sample was covered with a heat insulating material.

In Table 1, the amount of the cement additive is shown as a ratio to the cement weight. The abbreviations are shown below.
C: Early-strength Portland cement Taiheiyo Cement (d = 3.14 g / cm ³ )
Aggregate: S High-quality sandstone crushed sand (d = 2.61 g / cm ³ )
G High-quality sandstone crushed stone (d = 2.62 g / cm ³ )
Ad: High-performance AE water reducing agent "Floric SF500S" Floric s / a: Indicates the ratio of fine aggregate to total aggregate.

The measurement results of Example 1 and Comparative Examples 1 and 2 are shown in FIG.
From FIG. 1, when the cement additive (1) of the present invention is added, the start time (condensation time) of the hydration reaction is almost the same as that without the addition, and the maximum temperature of the temperature rise due to the hydration reaction is reached. It turns out that can be reduced. On the other hand, when the conventional cement additive (2) is added, the start time (condensation time) of the hydration reaction is delayed, and the maximum temperature at which the temperature rise due to the hydration reaction is reached is compared with that without the addition. It turns out that it cannot be lowered.

Claims (4)

A method for producing an additive for cement, which comprises the following steps (1) to (3).
Step (1): A step of coating a cement setting retarder with an insoluble or sparingly soluble coating agent in water at 5 to 50 ° C. to obtain a coating material.
Step (2): A step of cleaning the covering body with a cleaning liquid containing water.
Step (3): A step of drying and solidifying the washed coating body to obtain an additive for cement. The method for producing a cement additive according to claim 1, wherein the cement setting retarder is a solid substance. The method for producing an additive for cement according to claim 1 or 2, wherein the coating agent is an organic compound having a melting temperature of 60 ° C. or higher. The method for producing an additive for cement according to any one of claims 1 to 3, wherein in the step (2), the cleaning time is 1 to 30 minutes.

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