JP6641636B2 - Method for controlling efflorescence for cement composition and cement product - Google Patents

Description

The present invention relates to efflorescence suppression methods and cement products for cement compositions.

  In a cement composition such as mortar or concrete, efflorescence, in which a white precipitate in the form of a sheet or a spot is deposited on the surface, may occur. Efflorescence is caused by water containing a water-soluble efflorescence component contained in the cement composition, which moves to the surface through internal voids due to drying or the like, and on the surface, the efflorescence component causes carbonic acid in the atmosphere It is generated by reacting with a gas to produce a white substance. The efflorescence component is calcium hydroxide, an alkali compound, a carbonate compound, or the like.

  In the efflorescence, the primary efflorescence caused by the efflorescence component dissolved in water during the production of the cement composition, and the secondary efflorescence caused by the efflorescence component dissolved in water invading from the surface of the cement composition, There is. In the primary efflorescence, calcium hydroxide is dissolved in water due to the hydration reaction of cement to generate calcium ions, and as described above, reacts with carbon dioxide gas in the atmosphere to generate calcium carbonate. It is caused by precipitation of crystals of calcium or calcium hydroxide itself.

  The occurrence of such efflorescence does not cause a decrease in the strength of the cement composition or an environmental problem, but is not preferable because it impairs the aesthetic appearance of the cement composition. In particular, the demand for a colored cement composition colored with a pigment or the like has been increasing in recent years. However, since a white substance due to efflorescence is conspicuous in appearance, the possibility of impairing the aesthetic appearance increases. Therefore, a cement composition free of efflorescence is desired, and various methods have been proposed as methods for suppressing the efflorescence phenomenon of the cement composition. For example, as one of the methods, there is a method of adding a silicone-based whitening inhibitor generally commercially available for a cement composition. Further, there is known a method of adding blast furnace slag fine powder or fly ash that reacts with a white flower component to suppress the white flower.

  Furthermore, there is also known a method of treating the surface of a cement composition to suppress efflorescence. Patent Literature 1 proposes a method of treating a surface of a cement composition with carbon dioxide, thereby carbonating the surface and suppressing subsequent carbonation of the surface, thereby suppressing efflorescence. Patent Literature 2 proposes a method in which cement and water are mixed to irradiate ultrasonic waves to reduce the occurrence of efflorescence.

JP-A-11-217281 JP-A-9-70811

  However, the conventional efflorescence inhibitor, blast furnace slag fine powder, and fly ash cannot be said to have a sufficient efflorescence suppression effect, and particularly have a low effect on primary efflorescence in a low-temperature environment. In addition, the methods of treating with carbon dioxide and ultrasonic waves all require a large amount of capital investment, so that the production cost increases and the number of production steps increases, so that the productivity of the cement composition decreases.

  The present invention has been made in view of the above circumstances, does not require a special device, and can suppress efflorescence without significantly changing the conventional cement composition manufacturing process, low temperature It is an object of the present invention to provide a efflorescence inhibitor and a method for suppressing efflorescence that can sufficiently suppress the occurrence of efflorescence of a cement composition under conditions, and a cement product that is excellent in appearance and can be easily handled.

The present inventor has conducted intensive studies in order to solve such problems, and as a result, has found that calcium nitrite can strongly suppress the occurrence of efflorescence of the cement composition even under low-temperature conditions. Based on this finding, they have found that calcium nitrite is suitable as a whitening inhibitor for cement compositions, leading to the present invention. Therefore, the present invention includes the following embodiments.
(1 ) A method for controlling efflorescence for a cement composition according to an embodiment of the present invention includes the step of adding a efflorescence inhibitor for a cement composition containing calcium nitrite to the cement composition.
( 2 ) The cement product according to the embodiment of the present invention is obtained by adding a cement composition-containing efflorescence inhibitor containing calcium nitrite to a cement composition containing cement.

  The efflorescence inhibitor for a cement composition and the efflorescence control method for a cement composition of the present invention suppresses efflorescence without requiring a special device and without significantly changing the conventional production process of the cement composition. And even under low-temperature conditions, the occurrence of efflorescence of the cement composition can be sufficiently suppressed. Further, the cement product of the present invention has excellent appearance and can be easily handled.

(Cement composition)
The efflorescence inhibitor and the method for controlling efflorescence according to the embodiment of the present invention are intended to suppress efflorescence of a cement composition. The cement composition is formed from a material containing at least cement and water, and the cement composition is either completely cured by a hydration reaction between cement and water, or uncured. Including. In the present specification, the uncured cement composition may be at least partially uncured, and may be partially cured, the other part is uncured, and the whole is uncured. Including both.

  The cement composition includes products including concrete and mortar, and semi-finished products that are in the process of being manufactured. Specifically, the cement composition includes concrete-containing portions and mortar-containing portions such as roads, bridges, tunnels, and buildings, interlocking blocks, building cavity blocks, decorative blocks, flat plates, ordinary blocks, earth retaining blocks, and tile bases. And mortar products and concrete products, and semi-finished products thereof.

  Generally, a cement composition is formed by three types of molding steps: vibration compaction, centrifugal compaction, and immediate demolding. The vibration compaction method is a method of compacting using a vibrator while putting a relatively soft uncured cement composition into a mold and curing it.The centrifugal compaction method applies a centrifugal force. This is a method for producing a cement composition having a lower water-cement ratio by removing uncured water inside the cement composition and curing the composition. Immediate demolding method is to suppress the plastic deformation after demolding, so that the content of water is extremely low, the uncured cement composition adjusted the mass ratio of water and cement, for cement composition This is a molding method in which the material is put into a mold, compacted by vibration, and then immediately removed from the mold and cured.

  A colored cement composition colored by adding a pigment or paint is known as a cosmetic product, but since the white substance generated by white flower is conspicuous in appearance, the aesthetic appearance is likely to be impaired by white flower. Become. Therefore, it is particularly effective to use the efflorescence inhibitor of the present invention in a colored cement composition.

  As described above, the cement composition is formed from a material containing at least cement and water. The cement composition may further include an aggregate.For example, the concrete material includes cement, fine aggregate, coarse aggregate, and water, and the mortar material includes cement and fine bone. Contains wood and water. The cement composition may further contain various additives. The cement composition is prepared by kneading using a general concrete mixer. For example, an uncured cement composition can be prepared by kneading the materials of the cement composition in a predetermined ratio by using a uniaxial or biaxial forced kneader.

  The uncured cement composition used in the present embodiment is preferably a hardened cement composition containing a small amount of water from the viewpoint of suppressing efflorescence. Therefore, as the uncured cement composition, a cement composition having a measured value of 0 cm measured by a slump test of the cement composition before curing can be suitably used.

  The cement is not particularly limited as long as it is a cement generally used in a cement composition. Examples of the cement include ordinary Portland cement, early-strength Portland cement, ultra-high-strength Portland cement, moderate-heat Portland cement, low-heat Portland cement, blast furnace cement, fly ash cement, silica cement, alumina cement, jet cement and the like. . One or more cements may be used.

  Examples of the water include, but are not particularly limited to, tap water, industrial water, recovered water, groundwater, river water, rainwater, and the like, and include organic substances and chlorides that have a negative effect on the hydration reaction of the cement and the cement composition. It is preferable that ions, sodium ions, potassium ions and the like are not contained, or that their contents are very small. As the water, tap water or industrial water with stable quality is particularly preferable.

  The aggregate includes fine aggregate and coarse aggregate. As the fine aggregate, mountain sand, sea sand, river sand, crushed sand, silica sand, blast furnace slag fine aggregate, ferronickel fine aggregate, copper slag fine aggregate, electric furnace oxidized slag fine aggregate, ferrochrome fine aggregate, Artificial lightweight fine aggregates, recycled fine aggregates and the like can be mentioned. The fine aggregate may be one kind or a mixture of two or more kinds.

  Examples of the coarse aggregate include mountain gravel, sea gravel, river gravel, crushed stone, blast furnace slag coarse aggregate, artificial lightweight coarse aggregate, and recycled coarse aggregate. The fine aggregate may be one kind or a mixture of two or more kinds.

  The cement composition used in the present embodiment may contain additives as necessary. Examples of the additive include a chemical admixture such as a shrinkage reducing agent, a water reducing agent, a defoaming agent, a fluidizing agent, a setting accelerator, a setting retarder, a synthetic resin powder, a synthetic resin fiber, a metal fiber, a carbon fiber, and a glass. Examples include fiber, limestone fine powder, expansive material, fly ash, silica fume, blast furnace slag fine powder, and the like. However, in consideration of the compatibility with calcium nitrite, the above-mentioned additive can be made so as not to contain an additive containing thiocyanate (rodanate) as a main component. In addition, the said additive may be used individually by 1 type, or may be used in mixture of 2 or more types.

(Bleach inhibitor)
The efflorescence inhibitor for a cement composition of the embodiment of the present invention contains calcium nitrite as an active ingredient. The efflorescence inhibitor for the cement composition may be composed of only calcium nitrite, or may contain other components other than calcium nitrite. As described above, the efflorescence inhibitor containing calcium nitrite has a large effect of suppressing the efflorescence of the cement composition even under a low temperature condition of about 5 ° C.

  Since the above-mentioned efflorescence inhibitor for cement composition contains calcium nitrite as an active ingredient, calcium nitrite-containing aqueous solution of calcium nitrite or powder or granular material containing calcium nitrite such as calcium nitrite is used. As a calcium nitrate-containing material, it can be added to the cement composition. For example, when the cement composition whitening inhibitor is an aqueous solution of calcium nitrite, by spraying or coating, to adhere the whitening inhibitor to the surface of the cement composition where the whitening phenomenon occurs, and the cement composition Since it can be kneaded in a material, it can be easily added to the cement composition. When the whitening inhibitor for a cement composition is a powdery substance or a granular substance, it can be easily added to the cement composition by kneading the cement composition. For this reason, the efflorescence inhibitor for cement composition of the present embodiment does not require a special device and can be used without greatly changing the conventional production process of the cement composition.

  Therefore, the efflorescence inhibitor for the cement composition of the present embodiment does not require a special device, and can be used without greatly changing the production process of the conventional cement composition, and at low temperatures. In this case, the cement composition has a large effect of suppressing the occurrence of efflorescence.

  The aqueous calcium nitrite solution may contain the calcium nitrite in an amount of 5% by mass or more and 30% by mass or less, preferably 10% by mass or more and 30% by mass or less, with the total amount of the calcium nitrite solution being 100% by mass. Good. If the amount is less than 5% by mass, the cement composition may have efflorescence due to too much water relative to the amount of calcium nitrite. In addition, since the whitening prevention effect can be sufficiently obtained at 30% by mass or less, the whitening of the cement composition can be effectively suppressed by adding calcium nitrite in this concentration range.

  The bleaching inhibitor according to the present embodiment can be effectively used for a cement composition molded by any molding method such as a vibration compaction method, a centrifugal force compaction method, and an immediate demolding method. Among these, the efflorescence inhibitor according to the present embodiment can be particularly effectively used for an immediate demolding cement composition molded by an instant demolding method. The immediate demolding cement composition has a lower water content per unit volume of the cement composition than a normal cement composition. Therefore, there is little free water to transfer the water-soluble component from the inside of the cement composition to the surface layer, and it is possible to suppress efflorescence only by treating the surface layer of the cement composition with the efflorescence inhibitor. Therefore, the use of the whitening inhibitor according to the present embodiment for an immediate demolding cement composition can reduce the amount of the whitening inhibitor and reduce the production cost.

(How to control efflorescence)
Next, a method for controlling efflorescence for a cement composition according to an embodiment of the present invention will be described. The method for controlling efflorescence of a cement composition of the present embodiment includes a step of adding calcium nitrite to the cement composition. Thereby, even under a low temperature condition, the occurrence of efflorescence of the cement composition can be extremely effectively suppressed.

  The method for controlling efflorescence for a cement composition according to the present embodiment may include a molding step of the cement composition. As described above, the molding step of the cement composition can be performed by the vibration compaction method, the centrifugal compaction method, or the immediate removal method, but is preferably performed by the immediate removal method. Here, a molding method using the immediate demolding method will be described. First, the above-described cement composition is charged into a mold having a desired shape and molded. At the time of molding, a pressure vibration molding process is added. Thereby, the filling property of the cement composition into the mold is improved, and the obtained cement composition is densified. The cement composition that has been subjected to the pressure vibration molding treatment is immediately removed from the mold. Thereby, a cement composition can be molded. The term “immediately” may be immediately after molding or may be several seconds to several minutes after molding.

  The method for controlling efflorescence for a cement composition of the present embodiment may further include a curing step of curing the molded cement composition. The curing step can be performed by a known curing method such as normal-pressure steam curing and autoclave curing. The curing step may be a low-temperature curing step of curing under a low-temperature condition of about 5 ° C. According to the method for controlling white spots of the present embodiment, even when cured at a low temperature of about 5 ° C., a sufficient effect of suppressing white spots can be obtained as compared with the conventional method for controlling white spots. it can. In addition, the curing step is preferably performed in a state where there is no or little water supply such as rainfall in the molded cement composition.

  The step of adding calcium nitrite to the cement composition may include a step of attaching a calcium nitrite-containing substance to the surface of the molded cement composition. In addition, the step of adding calcium nitrite to the cement composition can include a step of kneading a calcium nitrite-containing substance into the cement composition. Hereinafter, these will be separately described as a method for controlling efflorescence for a cement composition according to one embodiment and another embodiment.

(Method of controlling efflorescence for cement composition according to one embodiment)
The method for controlling efflorescence for cement composition according to one embodiment of the present invention includes, as a step of adding calcium nitrite, a step of molding the cement composition, and a step of adding the calcium nitrite-containing substance to the surface of the molded cement composition. Adhering. In the present specification, the calcium nitrite-containing substance refers to a substance containing calcium nitrite, and may be in any state such as powder, granule, aqueous solution or gel fluid. You may.

  In the present embodiment, an example will be described in which the cement composition is molded by an immediate demolding method, and an aqueous solution of calcium nitrite is used as the calcium nitrite-containing material. More specifically, the method for controlling efflorescence for cement composition comprises a step of molding the cement composition by an immediate demolding method, and after demolding, an aqueous solution of calcium nitrite is applied to the surface of the molded cement composition. Adhering.

  The molded cement composition comprises a surface layer exposed to the atmosphere and an interior surrounded by the surface layer. According to such a method, nitrite is removed from the surface of the molded cement composition exposed to the atmosphere. Since calcium can be applied, the efflorescence suppressing layer containing calcium nitrite is formed only on the surface layer of the molded cement composition, and can be prevented from being formed inside. Thereby, while the efflorescence of a cement composition can be suppressed, the production cost can be reduced by suppressing the usage of calcium nitrite.

  The step of adhering the aqueous calcium nitrite solution, which is a calcium nitrite-containing substance, to the surface of the molded cement composition is performed by applying or spraying the aqueous calcium nitrite solution on the surface of the molded cement composition. Can be. The application or spraying of the calcium nitrite aqueous solution can be performed using a coating method or a spraying device arranged on a cement composition production line by a known method such as a roller method, a spray method, or a brushing method. .

  The step of attaching the aqueous calcium nitrite solution, which is a calcium nitrite-containing substance, to the surface of the molded cement composition can be performed within 60 minutes after the molding of the cement composition. According to this, the calcium nitrite aqueous solution can be applied at a stage where the hydration reaction of the cement and water in the cement composition does not proceed excessively, so that the efflorescence can be effectively suppressed.

As described above, when the aqueous calcium nitrite solution is attached to the surface of the molded cement composition, the amount of the applied calcium nitrite aqueous solution is 0.1 kg / m ² or more and 1.0 kg / m ² or less, preferably 0 kg / m ² or less. it can be .2kg / ^{m 2} or more 0.8 kg / ^{m 2} or less. By controlling the amount of adhesion to be 0.1 kg / m ² or more and 1.0 kg / m ² or less, the effect of calcium nitrite to suppress efflorescence is obtained. However, the adhesion amount becomes liquid unevenness is likely to occur when less than 0.2 kg / ^{m 2,} when it exceeds 0.8 kg / ^{m 2,} tends to occur the influence of efflorescence caused by water in the aqueous solution, efflorescence suppression since the effect is reduced, it is possible to further enhance the efflorescence suppression effect by a 0.2 kg / ^{m 2} or more 0.8 kg / ^{m 2} or less.

When a calcium nitrite-containing substance such as an aqueous solution of calcium nitrite is adhered, the content of calcium nitrite per unit area in the calcium nitrite-containing substance adhered to the surface of the molded cement composition is reduced to 0. By controlling the amount to be from 2.02 kg / m ^{2 to} 0.30 kg / m ² , the effect of calcium nitrite to suppress efflorescence can be sufficiently obtained. Preferably, the content of calcium nitrite per unit area in the calcium nitrite-containing material attached to the surface of the molded cement composition is 0.03 kg / m ² or more and 0.16 kg / m ² or less. By attaching a calcium nitrite-containing material to the varnish, an extremely high efflorescence suppressing effect can be obtained.

Furthermore, when a calcium nitrite-containing substance such as an aqueous calcium nitrite solution is adhered, the water content per unit area of the calcium nitrite-containing substance adhered to the surface of the molded cement composition is 0.06 kg. / M ² or more and 0.80 kg / m ² or less, preferably 0.16 kg / m ² or more and 0.64 kg / m ² or less. When the water content is 0.06 kg / m ² or more and 0.80 kg / m ² or less, the effect of calcium nitrite to suppress efflorescence can be sufficiently obtained. When the water content per unit area is 0.16 kg / m ² or more and 0.64 kg / m ² or less, the water can be smoothly adhered to the molded cement composition, and the water content in the calcium nitrite-containing material can be improved. It is also possible to reduce the influence of the occurrence of white spots, and it is possible to further enhance the white spot suppression effect.

More preferably, when applying a calcium nitrite-containing substance such as an aqueous solution of calcium nitrite, the content of calcium nitrite per unit area in the calcium nitrite-containing substance attached to the surface of the molded cement composition There 0.02 kg / m ² or more and, nitrous as water content per unit area of the calcium nitrite-containing material in which is adhered to the surface of the molded cement composition is 0.80 kg / m ² or less A substance containing calcium nitrate may be attached. More preferably, the content of calcium nitrite per unit area in the calcium nitrite-containing substance attached to the surface of the molded cement composition is 0.03 kg / m ² or more, and the molded cement composition The calcium nitrite-containing substance may be adhered so that the water content per unit area in the calcium nitrite-containing substance adhered to the surface of the resin is 0.64 kg / m ² or less. According to this, the effect of water in the calcium nitrite-containing material to prevent the occurrence of efflorescence can be prevented while obtaining a high efflorescence suppression effect of calcium nitrite, so that the efflorescence suppression effect can be further enhanced.

  The method for controlling efflorescence of the cement composition of the present embodiment is performed such that the cement composition is exposed before the step of attaching the calcium nitrite-containing substance to the surface of the molded cement composition. May include a step of protecting the periphery of the cement composition with a coating covering the periphery of the cement composition. That is, the method for controlling efflorescence of the cement composition according to the present embodiment includes a step of protecting the periphery of the cement composition, a step of molding the cement composition, and attaching the calcium nitrite-containing substance to the surface of the molded cement composition. And a step of causing it to be performed. Thus, when attaching the calcium nitrite-containing substance, the contamination of the surrounding environment can be prevented by preventing the calcium nitrite from scattering around.

  Further, the method for controlling efflorescence of cement composition of the present embodiment may include the above-mentioned curing step after the step of attaching the calcium nitrite-containing substance to the surface of the molded cement composition.

(Method for controlling efflorescence for cement composition according to another embodiment)
A method for controlling efflorescence for a cement composition according to another embodiment of the present invention includes the steps of adding a calcium nitrite-containing substance to the cement composition, and molding the cement composition to which the calcium nitrite-containing substance is added. And a step. Furthermore, the method for controlling efflorescence of cement composition of the present embodiment may include the above-mentioned curing step after the step of molding the cement composition. Here, as described above, the calcium nitrite-containing substance is a powder or granular substance of calcium nitrite alone, a fluid such as an aqueous solution of calcium nitrite, or a mixture of substances other than calcium nitrite. Can be added.

  In the step of adding and mixing the calcium nitrite-containing material, the uncured cement composition to which the calcium nitrite-containing material has been added is kneaded using a kneader. The calcium nitrite-containing material may be added to the powdery cement composition material and mixed, and then water may be added, and the uncured cement composition to which the calcium nitrite-containing material has been added may be kneaded. Alternatively, a calcium nitrite-containing substance may be added later to the kneaded cement composition and further kneaded.

  The calcium nitrite-containing material is preferably 1.5 parts by mass or more so that calcium nitrite is 0.5 parts by mass or more and 3.0 parts by mass or less based on 100 parts by mass of cement in the cement composition. A calcium nitrite-containing substance can be added to the cement composition so as to be 2.5 parts by mass or less. Suppression of efflorescence by calcium nitrite by adding a calcium nitrite-containing substance to a cement composition such that calcium nitrite is 0.5 parts by mass or more and 3.0 parts by mass or less based on 100 parts by mass of cement. The effect can be sufficiently obtained. Further, by adding a calcium nitrite-containing substance to the cement composition so that the calcium nitrite is 1.5 parts by mass or more, the effect of preventing efflorescence can be extremely increased. If the calcium nitrite exceeds 2.5 parts by mass, the viscosity of the cement composition in a fresh state increases, the temporal change of the consistency increases, and the material cost increases. It is preferable that the content be 1.5 to 2.5 parts by mass with respect to parts.

(Cement products)
The cement product of the present embodiment is obtained by adding calcium nitrite to a cement composition containing cement. Calcium nitrite not only suppresses the efflorescence of the above-mentioned cement composition, but also promotes the hardening of the cement composition, and can express the strength of concrete at an early stage. Therefore, the cement product of the present embodiment is less likely to cause efflorescence and can be cured at an early stage, so that it has excellent appearance and can be easily handled.

  Subsequently, an example in which the whitening inhibitor and the method for preventing whitening according to the present embodiment are more specifically described.

(Example 1)
As the cement composition material, a mortar material composed of 28 parts by mass of water, 100 parts by mass of cement, 360 parts by mass of fine aggregate, and 10 parts by mass of pigment was prepared. Tap water was used as water, ordinary Portland cement was used as cement, and silica sand was used as fine aggregate. As an additive material, a efflorescence inhibitor consisting of calcium nitrite was added. The additive material was mixed with the cement composition such that the additive material was 2 parts by mass with respect to 100 parts by mass of the cement in the cement composition. The method of addition was the same as that of Example 1 having a size of φ75 mm × 30 mm by kneading an uncured cement composition to which water in which an additive material was dissolved was added using a mortar mixer and then compacting using a mold and a vibrator. A specimen was obtained. The compaction rate was set to 82% so as to easily cause efflorescence.

(Example 2)
The same procedures as in Example 1 were carried out except that the mass ratio of calcium nitrite as an additive material was changed to 3 parts by mass and the mass ratio of water was changed to 27 parts by mass with respect to 100 parts by mass of the cement in the cement composition. 2 specimens were obtained.

(Comparative Example 1)
A specimen of Comparative Example 1 was obtained in the same manner as in Example 1, except that the additive material was not added and the mass ratio of water to 100 parts by mass of cement was changed to 30 parts by mass. For this reason, in Table 1, the additive material type was not added.

(Comparative Example 2)
The additive material was changed to a conventional silicone-based kneading-type white flower inhibitor instead of the calcium nitrite-based white flower inhibitor, and the mass ratio of the conventional white flower inhibitor to 100 parts by mass of cement was changed. A specimen of Comparative Example 2 was obtained in the same manner as in Example 1, except that the mass ratio of 0.3 part by mass and water was changed to 29.7 parts by mass.

(Comparative Example 3)
The additive material was changed to a blast furnace slag fine powder instead of the efflorescence inhibitor consisting of calcium nitrite, and the mass ratio of the additive material was 30 parts by mass and the mass ratio of the fine aggregate was 334 parts by mass with respect to 100 parts by mass of cement. And a test piece of Comparative Example 3 was obtained in the same manner as in Example 1 except that the added material was added without dissolving in water.

(Comparative Example 4)
A specimen of Comparative Example 4 was obtained in the same manner as in Example 1 except that the additive material was changed to sodium nitrite instead of the efflorescence inhibitor composed of calcium nitrite.

(Comparative Example 5)
A specimen of Comparative Example 5 was obtained in the same manner as in Example 1 except that the additive material was changed to potassium nitrite instead of the efflorescence inhibitor consisting of calcium nitrite.

(Comparative Example 6)
A specimen of Comparative Example 6 was obtained in the same manner as in Example 1 except that the additive material was changed to lithium nitrite instead of the efflorescence inhibitor consisting of calcium nitrite.

(Comparative Example 7)
A specimen of Comparative Example 7 was obtained in the same manner as in Example 1 except that the additive material was changed to calcium nitrate instead of the efflorescence inhibitor consisting of calcium nitrite.

(Comparative Example 8)
A specimen of Comparative Example 8 was obtained in the same manner as in Example 1 except that the additive material was changed to sodium nitrate instead of the efflorescence inhibitor consisting of calcium nitrite.

(Comparative Example 9)
A specimen of Comparative Example 9 was obtained in the same manner as in Example 1 except that the additive material was changed to potassium nitrate instead of the efflorescence inhibitor consisting of calcium nitrite.

(Comparative Example 10)
A specimen of Comparative Example 10 was obtained in the same manner as in Example 1 except that the additive material was changed to lithium nitrate instead of the efflorescence inhibitor consisting of calcium nitrite.

( Comparative Example 12 )
A specimen of Comparative Example 12 was obtained in the same manner as in Example 1 except that the mass ratio of the added material and the mass ratio of water were changed to 0.5 parts by mass and 29.5 parts by mass with respect to 100 parts by mass of cement. Was.

( Comparative Example 13 )
A specimen of Comparative Example 13 was obtained in the same manner as in Example 1, except that the mass ratio of the additive material and the mass ratio of water were changed to 1 part by mass and 29 parts by mass with respect to 100 parts by mass of cement.

(Example 5)
As a bleach inhibitor, a 20% by mass aqueous solution of calcium nitrite was prepared by dissolving calcium nitrite in water such that the total amount of the aqueous solution of calcium nitrite was 100% by mass and the amount of calcium nitrite was 20% by mass. As the cement composition material, a mortar material composed of 30 parts by mass of tap water, 100 parts by mass of ordinary Portland cement, 360 parts by mass of silica sand, and 10 parts by mass of pigment was prepared. The uncured cement composition kneaded with the mortar material is immediately molded by a demolding method. Immediately after the demolding (spray start time: 0 minutes), the surface of the molded cement composition is atomized by mist spraying. The test piece of Example 5 was obtained by spraying the efflorescence inhibitor so that the amount of the inhibitor attached was 0.2 kg / m ² .

(Example 6)
A specimen of Example 6 was obtained in the same manner as in Example 5, except that the amount of the 20% by mass aqueous solution of calcium nitrite as a whitening inhibitor was sprayed so that the adhesion amount was 0.3 kg / m ² .

(Example 7)
A test piece of Example 7 was obtained in the same manner as in Example 5, except that the amount of the 20% by mass aqueous solution of calcium nitrite as a whitening inhibitor was sprayed so that the adhesion amount was 0.5 kg / m ² .

(Example 8)
After removing the molded cement composition, 20 minutes by mass of a 20% by mass nitrite as a whitening inhibitor such that the adhesion amount of the 20% by mass aqueous solution of calcium nitrite becomes 0.3 kg / m ² when 30 minutes have passed. A specimen of Example 8 was obtained in the same manner as in Example 5, except that the aqueous calcium solution was sprayed.

(Example 9)
After removing the molded cement composition from the mold, when 60 minutes have elapsed, 20 mass% nitrite is used as a whitening inhibitor such that the adhesion amount of the 20 mass% calcium nitrite aqueous solution becomes 0.3 kg / m ^2. A specimen of Example 9 was obtained in the same manner as in Example 5, except that the aqueous calcium solution was sprayed.

( Comparative Example 14 )
A specimen of Comparative Example 14 was obtained in the same manner as in Example 5, except that the amount of the 20% by mass aqueous solution of calcium nitrite as a whitening inhibitor was sprayed so as to be 0.1 kg / m ² .

( Comparative Example 15 )
A specimen of Comparative Example 15 was obtained in the same manner as in Example 5, except that the amount of the 20 mass% calcium nitrite aqueous solution as a whitening inhibitor was sprayed so as to be 1.0 kg / m ² .

(Comparative Example 11)
The molded cement composition of Example 5 to which the aqueous calcium nitrite solution was not adhered (no adhesion) was used as a specimen of Comparative Example 11. In addition, since the calcium nitrite aqueous solution was not attached to this test piece, in Table 3, the type of the propellant was not attached.

(Example 12)
A test piece of Example 12 was obtained in the same manner as in Example 5, except that the 20 mass% aqueous solution of calcium nitrite as a florescence inhibitor was sprayed so that the adhesion amount was 0.8 kg / m ² .

( Comparative Example 16 )
A specimen of Comparative Example 16 was obtained in the same manner as in Example 6, except that the bleaching inhibitor was changed to a 5% by mass aqueous solution of calcium nitrite instead of the 20% by mass aqueous solution of calcium nitrite. The 5% by mass aqueous solution of calcium nitrite contains 5% by mass of calcium nitrite, with the total amount of the aqueous solution of calcium nitrite being 100% by mass.

(Example 14)
A specimen of Example 14 was obtained in the same manner as in Example 6, except that the bleaching inhibitor was changed to a 10% by mass aqueous solution of calcium nitrite instead of the 20% by mass aqueous solution of calcium nitrite. Hereinafter, the 10% by mass aqueous solution of calcium nitrite contains 10% by mass of calcium nitrite, with the total amount of the aqueous solution of calcium nitrite being 100% by mass.

(Example 15)
A specimen of Example 15 was obtained in the same manner as in Example 7, except that the bleaching inhibitor was changed to a 10% by mass aqueous solution of calcium nitrite instead of the 20% by mass aqueous solution of calcium nitrite.

(Example 16)
A test piece of Example 16 was obtained in the same manner as in Example 6, except that the whitening inhibitor was changed to a 30% by mass aqueous solution of calcium nitrite instead of the 20% by mass aqueous solution of calcium nitrite. Hereinafter, the 30% by mass aqueous solution of calcium nitrite contains 30% by mass of calcium nitrite, with the total amount of the aqueous solution of calcium nitrite being 100% by mass.

( Comparative Example 17 )
A test sample of Comparative Example 17 was obtained in the same manner as in Comparative Example 15 , except that the whitening inhibitor was changed to a 30% by mass aqueous solution of calcium nitrite instead of the 20% by mass aqueous solution of calcium nitrite.

[White flower test 1]
By visually observing the specimens of Examples 1 and 2 and Comparative Examples 1 to 10 that were exposed to a thermostat at a temperature of 5 ° C. and a humidity of 88%, which is a condition in which efflorescence is likely to occur, for 7 days, Efficacy of white flower was evaluated. In the case where the occurrence of white flower was not recognized at all or the amount was extremely small, the white spot suppression effect was evaluated as “○” having an excellent effect, and “X” was evaluated as “No effect” except for the above. Table 1 shows the results of the evaluation of the thus-measured effect of the white spots.

[White flower test 2]
Among the specimens of Example 1 and the specimens of Comparative Examples 1, 4 to 10 exposed to a thermostat at a temperature of 5 ° C. and a humidity of 88%, which is a condition that easily causes efflorescence, among the specimens, the atmosphere was The surface of the specimen where the efflorescence was exposed to the inside and the surface of the specimen of Comparative Example 1 (without additives) which was not exposed to the air and where the efflorescence was not generated. By measuring the color difference ΔE * ab, the degree of the effect of suppressing the white spot by the type of the additive material was measured. Unless exposed to the air, drying and carbonation do not occur, and no efflorescence occurs. Therefore, of the specimens of Comparative Example 1 (no additive specimen), The measurement was performed on a surface where no efflorescence was generated.

  ΔE * ab, which is the L * a * b * color difference, was measured by measuring L *, a *, and b * with a colorimeter and calculating the value by the formula shown in Equation 1. Note that ΔL *, Δa *, and Δb * represent the whiteness of the surface of each specimen, which was exposed to the air, and the whiteness of the specimen of Comparative Example 1 (the additive-free specimen) which was not exposed to the air. This is the difference between L *, a *, and b * from the surface where no sintering occurs. Table 2 shows the measured color difference ΔE * ab. Note that L *, a *, and b * are called CIE1976 (L * a * b *) color system, and are stipulated in JIS Z 8729 in Japanese Industrial Standards.

  In Table 1, in Comparative Examples 1 to 10, the evaluation of the inhibitory effect was "x", whereas in Examples 1 and 2 in Table 1, the evaluation of the inhibitory effect was "O". Then, as shown in Table 2, the color difference ΔE * ab of Example 1 was much lower than those of Comparative Examples 1 to 10. That is, from the results of the above-described efflorescence tests 1 and 2, calcium nitrite strongly suppresses efflorescence of the cement composition, and calcium nitrite is effective as an efflorescence inhibitor for the cement composition. Was found.

  From the results of Comparative Example 3, it is recognized that the blast furnace slag fine powder has a low effect of suppressing primary efflorescence generated at the initial age under low temperature conditions. This is presumed that the expected reaction between the blast furnace fine powder and calcium hydroxide did not occur under the low temperature condition and at the initial age. From the experiment using Comparative Example 2, it was confirmed that the conventional silicone-based kneading-type florescence inhibitor tends to have a variation in the efflorescence suppressing effect in the primary florescence at low temperature.

[White flower test 3]
Next, using the specimens of Examples 1 and 2 and Comparative Examples 1 , 12 , and 13 , the change in the effect of inhibiting the white blossom due to the amount of calcium nitrite added when kneading with addition of calcium nitrite was verified. . By observing the specimens of Examples 1 and 2 and Comparative Examples 12 and 13 exposed to a thermostat at a temperature of 5 ° C. and a humidity of 88% for 7 days, which is a condition that easily causes the efflorescence, the efflorescence suppression effect was observed. evaluated. As for the effect of suppressing the efflorescence, when no occurrence of efflorescence was observed or when the amount was extremely small, it was evaluated as “◎”, which was an excellent effect. In addition, it was evaluated as “○” when there was an effect when the white spot was suppressed as compared with the case where no additive was added, and “×” when the white spot was generated more. Table 3 shows the evaluation results.

  From the results of Efflorescence Test 3, when calcium nitrite is added and kneaded, calcium nitrite is added in an amount of 0.5 parts by mass or more based on 100 parts by mass of cement in the cement composition. It was recognized that by adding calcium nitrite to the cement composition so as to be 3.0 parts by mass or less, it was possible to suppress the efflorescence of the mortar. By adding calcium nitrite to the cement composition so that the calcium nitrite exceeds 1.0 part by mass and becomes 2.0 parts by mass, it is apparent that the efflorescence of the mortar can be more effectively suppressed. Became. Therefore, preferably, calcium nitrite is added to the cement composition such that calcium nitrite is 1.5 parts by mass or more with respect to 100 parts by mass of cement in the cement composition. Can be more effectively suppressed.

  Further, when the calcium nitrite exceeds 2.5 parts by mass, the viscosity of the cement composition in a fresh state increases, the temporal change in consistency increases, and the material cost increases. It is preferable to add calcium nitrite to the cement composition so that the amount of calcium nitrite is 2.5 parts by mass or less based on parts. Therefore, as the addition amount of calcium nitrite, calcium nitrite is added to the cement composition such that calcium nitrite is 1.5 parts by mass or more and 2.5 parts by mass or less based on 100 parts by mass of cement in the cement composition. It is preferable to add it to the product.

[White flower test 4]
Using the test specimens of Examples 5 to 9 and Comparative Example 11, the presence or absence of the effect of inhibiting the occurrence of efflorescence by attaching an aqueous solution of calcium nitrite to the surface of the molded cement composition was examined. The specimens of Examples 5 to 9 and Comparative Example 11 were exposed to a thermostat at a temperature of 5 ° C. and a humidity of 88% for 7 days, which is a condition under which white floc is easily generated, by visually observing the occurrence of white floc. Hua suppression effect was evaluated. The evaluation of the whitening effect was evaluated as "O" when no or no trace of whitening occurred, and "X" when there was no effect. Table 4 shows the evaluation results.

  As described above, while the specimens of Examples 5 to 9 did not produce or had a very small amount, the specimen of Comparative Example 11 produced much efflorescence. Therefore, it was recognized that attaching an aqueous solution of calcium nitrite to the surface of the molded cement composition was effective for the effect of suppressing efflorescence. Then, 30 minutes and 60 minutes after the molding, an aqueous solution of calcium nitrite was adhered to the surface of the molded cement composition, which also had an effect of suppressing efflorescence. Thereby, it was recognized that even after a certain period of time had elapsed after the molding, an aqueous solution of calcium nitrite was applied to the molded cement composition to obtain an effect of suppressing efflorescence. It is considered that this can be achieved by effectively applying the aqueous solution of calcium nitrite at a stage where the hydration reaction of the cement and water in the cement composition does not proceed excessively, whereby the efflorescence can be effectively suppressed.

[White flower test 5]
Using the specimens of Examples 5 to 7 , 12, 14 to 16 and Comparative Examples 11 and 14 to 17 which were exposed to a thermostat at a temperature of 5 ° C. and a humidity of 88%, which is a condition that easily causes efflorescence , for 7 days, The effect of the cement composition on the inhibition of efflorescence by the concentration and amount of the calcium nitrite aqueous solution adhered to the surface of the molded cement composition was examined. The occurrence of efflorescence in the specimen on the 7th day of age was visually observed to evaluate the efflorescence suppression effect. With respect to the effect of suppressing the efflorescence, a case where no efflorescence was generated or a very small amount of efflorescence was evaluated as “◎”, which is an excellent effect. In addition, it was evaluated as “○” when there was an effect on the occurrence of white flower, and evaluated as “×” when a lot of white flower was generated as compared with the case of no adhesion. Table 5 shows the evaluation results.

As a result of the efflorescence test 5, by controlling the amount of the aqueous solution of calcium nitrite on the surface of the molded cement composition to be 0.1 kg / m ² or more and 1.0 kg / m ² or less, efflorescence suppression by calcium nitrite is performed. It is recognized that the effect can be obtained. Preferably, the adhesion amount of calcium nitrite aqueous solution to the surface of the molded cement composition by a 0.2 kg / m ² or more 0.8 kg / m ² or less, to obtain a very high efflorescence suppression It is recognized that it is possible. Deposition amount becomes liquid unevenness is likely to occur when less than 0.2 kg / m ^2, when it exceeds 0.8 kg / m ^2, in order to influence the efflorescence caused by water in the aqueous solution occurs, white with nitrous acid calcium This is because it is considered that the sinter suppression effect is reduced.

In addition, by setting the content of calcium nitrite per unit area in the adhesive agent attached to the surface of the molded cement composition to 0.02 kg / m ² or more and 0.30 kg / m ² or less, It is recognized that the efflorescence suppressing effect by calcium can be obtained. Preferably, the content of calcium nitrite per unit area in the adhesive attached to the surface of the molded cement composition is 0.03 kg / m ² or more and 0.16 kg / m ² or less. It is recognized that an extremely high whitening suppression effect can be obtained by attaching the aqueous calcium nitrate solution.

In addition, by setting the water content per unit area of the adhesive agent adhered to the surface of the molded cement composition to 0.06 kg / m ² or more and 0.80 kg / m ² or less, whitening by calcium nitrite is performed. The sinter suppression effect is sufficiently recognized. Preferably, by setting the content to 0.16 kg / m ² or more and 0.64 kg / m ² or less, the cement composition can be smoothly attached to the molded cement composition, and at the same time, the effect of efflorescence caused by water in the adhesive is suppressed. Can also be reduced, and the effect of suppressing efflorescence can be further enhanced.

From these, the content of calcium nitrite per unit area in the adhesive agent adhering to the surface of the molded cement composition is 0.02 kg / m ² or more, and the adhering agent adheres to the surface of the molded cement composition. It has been found that it is more preferable to attach the adhesive so that the water content per unit area in the applied adhesive is 0.80 kg / m ² or less. Thereby, it is possible to prevent the effect of water in the adhesive on the occurrence of efflorescence while obtaining the efflorescence suppressing effect of calcium nitrite. More preferably, the content of calcium nitrite per unit area in the adhesive agent adhered to the surface of the molded cement composition is 0.03 kg / m ² or more, and The adhesive may be attached such that the water content per unit area in the adhesive attached to the surface is 0.64 kg / m ² or less. According to this, it is possible to prevent the effect of water in the adhesive from causing the occurrence of efflorescence while obtaining the high efflorescence suppression effect of calcium nitrite, so that the efflorescence suppression effect can be further enhanced.

  Note that the technical scope of the present invention is not limited to the above embodiments and examples, and various changes can be made without departing from the spirit of the present invention. From the above description, it is confirmed that the embodiment of the present invention is as follows.

(1) The bleaching inhibitor for a cement composition according to the embodiment of the present invention contains calcium nitrite.
(2) The efflorescence inhibitor for cement composition according to the embodiment of the present invention is a calcium nitrite aqueous solution containing the calcium nitrite, wherein the total amount of the calcium nitrite aqueous solution is 100% by mass, and Is an aqueous solution of calcium nitrite containing 5% by mass or more and 30% by mass or less.
(3) The method for controlling efflorescence of a cement composition according to the embodiment of the present invention includes a step of adding calcium nitrite to the cement composition.
(4) The method for controlling efflorescence for a cement composition according to the embodiment of the present invention is the method for controlling efflorescence for a cement composition according to the above (3), wherein the step of adding the calcium nitrite is performed as described above. A step of kneading the uncured cement composition to which the calcium nitrite-containing substance is added.
(5) The method for controlling efflorescence for a cement composition according to the embodiment of the present invention is the method for controlling efflorescence for a cement composition according to the above (4), wherein the cement composition contains cement, and The step of kneading the uncured cement composition to which the calcium nitrate-containing material is added is performed so that the calcium nitrite is 0.5 parts by mass or more and 3.0 parts by mass or less based on 100 parts by mass of the cement. And adding the calcium nitrite-containing material to the cement composition.
(6) The method for controlling efflorescence for a cement composition according to the embodiment of the present invention is the method for controlling efflorescence for a cement composition according to (3), wherein the step of adding the calcium nitrite includes the step of: A step of applying a calcium nitrite-containing substance to the surface of the cement composition.
(7) The method for controlling efflorescence for a cement composition according to the embodiment of the present invention is the method for controlling efflorescence for a cement composition according to (6), wherein the calcium nitrite-containing material is calcium nitrite. The step of applying the calcium nitrite-containing material to the surface of the cement composition so that the amount of the calcium nitrite aqueous solution becomes 0.1 kg / m ² or more and 1.0 g / m ² or less. A step of attaching the calcium nitrite aqueous solution.
(8) The method for controlling efflorescence for a cement composition according to an embodiment of the present invention is the method for controlling efflorescence for a cement composition according to (6) or (7), wherein the calcium nitrite-containing material is And an aqueous solution of calcium nitrite, wherein the aqueous solution of calcium nitrite contains 5% by mass or more and 30% by mass or less of the calcium nitrite based on 100% by mass of the total amount of the aqueous solution of calcium nitrite.
(9) The method for controlling efflorescence for a cement composition according to the embodiment of the present invention is the method for controlling efflorescence for a cement composition according to any one of (3) to (8) above, wherein the calcium nitrite is used. Is provided with a molding step of molding the cement composition by an immediate demolding method.
(10) The cement product according to the embodiment of the present invention is obtained by adding calcium nitrite to a cement composition containing cement.

Claims (4)

It comprises a step of adding a calcium nitrite-containing cement composition efflorescence inhibitor to a cement composition containing cement ,
The step of adding the cement composition efflorescence inhibitor to the cement composition includes a step of kneading the cement composition efflorescence inhibitor to the uncured cement composition,
In the step of kneading the cement composition bleaching inhibitor to the uncured cement composition, the calcium nitrite is more than 1 part by mass and not more than 3.0 parts by mass with respect to 100 parts by mass of the cement. Thus, a method for controlling efflorescence for a cement composition , comprising adding the efflorescence inhibitor for a cement composition to the cement composition. It comprises a step of adding a calcium nitrite-containing cement composition efflorescence inhibitor to a cement composition containing cement,
The step of adding the cement composition efflorescence inhibitor to the cement composition comprises the step of attaching the cement composition efflorescence inhibitor to the surface of the cement composition ,
The cement composition efflorescence inhibitor is a calcium nitrite aqueous solution containing the calcium nitrite,
The aqueous calcium nitrite solution contains 10% by mass or more and 30% by mass or less of the calcium nitrite, with the total amount of the aqueous solution of calcium nitrite being 100% by mass.
Wherein in the step of the cement composition efflorescence inhibitor is deposited on the surface of the cement composition, so that the amount of deposition of the calcium nitrite solution is 0.2 kg / m ² or more 0.8 kg / m ² or less, A method for controlling efflorescence of a cement composition, wherein the calcium nitrite aqueous solution is adhered to a surface of the cement composition. An uncured cement composition containing cement is mixed with a cement composition efflorescence inhibitor containing calcium nitrite ,
A cement product containing the calcium nitrite in an amount of more than 1 part by mass and 3.0 parts by mass or less based on 100 parts by mass of the cement.   On the surface of the cement composition containing cement, a cement composition-containing efflorescence inhibitor containing calcium nitrite is attached,
  The cement composition efflorescence inhibitor is a calcium nitrite aqueous solution containing the calcium nitrite,
  The aqueous calcium nitrite solution contains 10% by mass or more and 30% by mass or less of the calcium nitrite, with the total amount of the aqueous solution of calcium nitrite being 100% by mass.
  The amount of the calcium nitrite aqueous solution deposited on the surface of the cement composition is 0.2 kg / m ² 0.8 kg / m or more ² Cement products that are: