JP6826115B2 - Fast-strength agent for cement, fast-strength cement using it, and method for manufacturing fast-strength concrete - Google Patents

Description

The present invention mainly relates to a cement composition used in civil engineering and construction, a cement hardened product using the same, and a method for producing the same.

Concrete products are manufactured by pouring a mixture of cement, aggregate, water, and admixture into a mold, curing it appropriately, and then removing the mold. Here, it is important to develop high strength in the early stage of the material age in terms of improving productivity, that is, the turnover rate of the mold. Improving the turnover rate of the formwork leads to reducing the required number of expensive formwork. As a method for increasing the initial strength, it is known to use early-strength cement, to prepare concrete having a low water-cement ratio by using a water reducing agent in combination, and to perform steam curing.

In recent years, the energy cost associated with the use of steam has risen, and there is an urgent need for a method that can shorten the steam curing time and a method that does not require steam curing. Further, from the demand for higher productivity, further shortening of the curing process may be desired. For example, in the production of concrete products, it may be necessary to develop high strength in a curing time of 16 hours. Normally, a complicated process such as a heating work process using steam or the like is incorporated in the curing process, but even if such a process is changed to improve the initial strength, it is difficult to be a practical method. Therefore, a method for easily obtaining a concrete product having high initial strength without changing the process is eagerly desired in the market from the viewpoint of manufacturing cost and the like.

As an admixture for increasing strength, those mainly composed of quicklime, gypsum, alkali metal sulfate and the like, and those in which a specific compound such as glycerin and an alkali metal sulfate are used in combination are known (Patent Document 1). ~ 4). In addition, there have been reports of using nitrates and carboxylic acids as curing accelerators, but there are few reports mentioning the combination of these plurality of curing accelerator components (Patent Documents 5 to 7). Further, a curing accelerator containing chlorine such as sodium chloride and calcium chloride is also known, but it is not preferable to use it because it causes salt damage which is a cause of deterioration of concrete.

Further, it has been reported that an aqueous solution containing nitrate promotes elution of calcium hydroxide in a hardened cement product (Non-Patent Document 1). Therefore, when nitrate is used as a curing accelerator, the production of calcium hydroxide, which is a hydration product of cement, does not proceed sufficiently, and the strength development may be inhibited in a long period of time. Therefore, it is preferable to set the concentration of calcium in the aqueous solution containing nitrate to a value of a certain amount or more so that the amount of calcium hydroxide produced is not impaired. However, if the concentration becomes too high, the calcium salt becomes a liquid. It precipitates inside and the storability of the liquid is impaired.

Curing accelerators containing nitrates and carboxylic acids have already been reported, but the curing accelerators referred to here are used as solids (Patent Document 8), and their concentrations have not been investigated (Patent Document 8). Patent Document 9).

Japanese Unexamined Patent Publication No. 2001-294460 Japanese Unexamined Patent Publication No. 2011-153068 Japanese Unexamined Patent Publication No. 2000-23959 Japanese Patent Publication No. 2008-591752 Japanese Unexamined Patent Publication No. 02-279546 Special Table 2000-516191 JP-A-2010-132547 JP-A-2002-220267 Japanese Patent No. 5140215

Cement / Concrete Papers, Vol. 61 (2008), pp. 262-269

As a result of various studies on the above-mentioned problems and requirements, the present invention dissolves nitric acid and its salt, carboxylic acid and its salt in water to a specific blending range without impairing the storability of the liquid. We have found that it is possible to develop an early-strengthening agent that does not inhibit the development of strength even in the long term, and obtained the knowledge to solve the above-mentioned problems, and completed the present invention.

That is, in the embodiment of the present invention, the following can be provided.

(1) Nitric acid or its salt is 30% by mass or more and 60% by mass or less.
Carboxylic acid or its salt is 0.1% by mass or more and 10% by mass or less.
A fast-strengthening agent for cement containing water
Moreover, the early-strengthening agent for cement is characterized in that the concentration of the calcium element in the early-strengthening agent for cement is in the range of 5% by mass or more and 20% by mass or less.

(2) Further, the fast-strengthening agent for cement of (1) containing alcohol amine or glycerin.

(3) A fast-strength cement in which 0.1 to 10 parts by mass of the fast-strengthening agent for cement of (1) or (2) is blended with respect to 100 parts by mass of cement.

(4) A method for producing fast-strength concrete, which comprises adding the fast-strengthening agent for cement of (1) or (2) to the ready-mixed concrete of an agitator car afterwards.

(5) A method for producing concrete, which comprises applying or spraying 100 to 600 g / m ^{2 of the} fast-strengthening agent for cement of (1) or (2) on a concrete surface before hardening.

The early-strengthening agent for cement according to the embodiment of the present invention is excellent in initial strength development, fluidity, and storage stability as compared with conventional materials.

Hereinafter, the present invention will be described in detail. Parts and% in this specification are based on mass unless otherwise specified. The term "concrete" as used herein is a general term for cement paste, mortar, and cement concrete. Further, in the present specification, the cement hardened body is a general term for concrete secondary products and concrete structures manufactured from cement paste, mortar, or concrete, or further combined with reinforcing bars or the like.

In the present specification, the numerical range (for example, the one represented by the symbol tilde "~") shall include the upper limit value and the lower limit value unless otherwise specified.

The nitric acid and its salt used in the embodiment of the present invention may be either an anhydride or a hydrate. Examples of nitrates include alkali metals, alkaline earth metals, and aluminum salts. You may use these in combination of 2 or more types. Among these, nitric acid, sodium nitrate, magnesium nitrate, potassium nitrate, calcium nitrate, and aluminum nitrate are preferable, and sodium nitrate and calcium nitrate are more preferable in terms of excellent strength development. It is more preferable to use calcium nitrate and sodium nitrate together.

In the cement quick-strengthening agent according to the embodiment of the present invention, the amount of nitric acid and its salt is preferably in the range of 30% or more and 60% or less, more preferably 40% or more and 50% or less in terms of anhydride. If the amount of nitric acid and its salt is less than 30%, excellent strength development may not be obtained, and if it exceeds 60%, slump may be lowered or long-term strength may be lowered.

The carboxylic acid and its salt used in the embodiment of the present invention are a general term for an organic compound having a carboxyl group and a salt thereof. Examples of such carboxylic acids include monocarboxylic acids such as formic acid, acetic acid and propionic acid, and dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelli acid, maleic acid, fumaric acid and phthalic acid. , Tricarboxylic acids such as trimellitic acid and tricarbarilylic acid, oxymonocarboxylic acids such as hydroxybutyric acid, lactic acid, and salicylic acid, oxydicarboxylic acids of malic acid, aminocarboxylic acids such as aspartic acid and glutamic acid, ethylenediamine tetraacetic acid (EDTA) And aminopolycarboxylic acids such as trans-1,2-diaminocyclohexanetetraacetic acid (CyDTA). Examples of the carboxylic acid salt include salts of alkali metals, alkaline earth metals and the like and any of the above carboxylic acids. Two or more of these can be used in combination. Among carboxylic acids and salts thereof, formic acid, sodium formate, calcium formate, sodium acetate, sodium oxalate, sodium lactate, and sodium aspartate are preferred, especially formic acid, sodium formate, and sodium formate, because of their excellent strength development. Calcium formate is more preferred. More preferably, formic acid and sodium formate can be used in combination.

In the cement quick-strengthening agent according to the embodiment of the present invention, the amount of the carboxylic acid and its salt is preferably in the range of 0.1% or more and 10% or less, and more preferably in the range of 2% or more and 7% or less. If the amount of the carboxylic acid and its salt is less than 0.1%, excellent strength development may not be obtained, and if it exceeds 10%, the long-term strength may be lowered.

The amount of calcium (Ca) element contained in the cement fast-strengthening agent according to the embodiment of the present invention is preferably in the range of 5% or more and 20% or less, and more preferably in the range of 8% or more and 15% or less. If the amount of calcium element is less than 5%, the long-term strength development may be impaired, and if it exceeds 20%, the storage stability of the liquid may be impaired. In order to include the calcium element in the fast-strengthening agent, a calcium salt may be used as a raw material. For example, the above-mentioned calcium salt of nitric acid or carboxylic acid may be used, or another calcium salt may be used. You may use either or both. Such a calcium salt is not particularly limited as long as it is a water-soluble salt, or even if it is a salt having a low water solubility, nitric acid or a salt thereof, a carboxylic acid or a carboxylic acid thereof contained in the fast-strengthening agent according to the embodiment of the present invention. It is not particularly limited as long as it reacts with a salt and dissolves. Another such calcium salt is, for example, calcium hydroxide.

The method for obtaining the amount of the calcium element is not particularly limited as long as it is a general quantitative analysis method, and can be calculated using, for example, an atomic absorption spectrophotometer.

In the fast-strengthening agent for cement according to the embodiment of the present invention, water is an essential component, and nitric acid or a salt thereof and a carboxylic acid or a salt thereof, or nitric acid or a salt thereof and a carboxylic acid or a salt thereof and another calcium salt are added. The balance added is water.

In the cement quick-strengthening agent according to the embodiment of the present invention, the amount of water is preferably 25 to 60%, more preferably 30 to 55%. If the amount of water is less than 25%, the material may be separated, and if it exceeds 60%, the premature strength may be insufficient.

The early-strengthening agent for cement according to the embodiment of the present invention may contain alcohol amine. Alcohol amines are used to improve the initial strength of the cement composition. Alcohol amine is not particularly limited, but can be used as long as it can be dissolved in an early-strengthening agent. The alcohol amine is an organic compound having a> N-R-OH structure in the structural formula. Here, R is an atomic group usually called an alkyl group or an aryl group, and R has a branched structure such as a linear alkylene group such as a methylene group, an ethylene group or an n-propylene group, or an isopropylene group. Examples thereof include an alkylene group and an aryl group having an aromatic ring such as a phenyl group and a benzyl group. R may be bonded to the nitrogen atom at two or more points, and a part or all of R may have a cyclic structure. R may be bonded to a plurality of hydroxyl groups. R may have an element other than carbon and an element other than hydrogen, for example, sulfur, fluorine, chlorine, oxygen, etc. as a part of the alkyl group. A plurality of hydroxyl groups may be bonded to R.

Examples of alcohol amines include ethanolamine, diethanolamine, diisopropanolamine, triethanolamine, N-methyldiethanolamine, N, N-dimethylethanolamine, N, N-dibutylethanolamine, N- (2-aminoethyl) ethanolamine, and the like. Examples thereof include boron trifluoride triethanolamine and derivatives thereof. One or more of these can be used.

Among the alcohol amines, monoethanolamine, diethanolamine, triethanolamine, and diisopropanolamine are preferable, and diethanolamine is more preferable, because they are excellent in improving fluidity. The amount of alcohol amine contained in the cement fast-strengthening agent is preferably 1 to 15%, more preferably 5 to 10%. If the amount of alcohol amine is less than 1%, the improvement in initial strength may be small, and if it exceeds 15%, the fluidity may be reduced.

The cement quick-strengthening agent according to the embodiment of the present invention may contain glycerin. Glycerin is used for the purpose of improving the initial strength of the cement composition. The glycerin used in the present invention, C ₃ H ₈ O ₃ in the chemical formula, a compound represented by the chemical name 1,2,3-propanetriol or glycerol. The amount of glycerin contained in the cement fast-strengthening agent is preferably 1 to 10%, more preferably 3 to 7%. If the amount of glycerin is less than 1%, the improvement in early strength may be small, and if it exceeds 10%, the long-term strength may be lowered.

The early-strengthening agent for cement according to the embodiment of the present invention preferably has a chlorine content of 0.1% or less. This is a feature required from the viewpoint of suppressing salt damage, which is a factor of deterioration of concrete. In order to reduce the chlorine content to 0.1% or less, it is sufficient to refrain from using a chlorine-containing material in the production of the early-strengthening agent. Among the above-mentioned raw materials, water is generally most likely to contain chlorine, but its content is unlikely to be a problem unless seawater or the like is used.

A fast-strength cement can be produced by blending the fast-strengthening agent according to the embodiment of the present invention with the cement. In this case, the amount of the fast-strengthening agent used is preferably 0.05 to 12 parts, more preferably 0.1 to 10 parts, still more preferably 0.5 to 10 parts, and 0.7 to 100 parts of cement. ~ 7 parts are more preferable, and 1 to 5 parts are most preferable. If the amount of the fast-strengthening agent is less than 0.5 parts, the improvement in strength development may not be excellent, and if it exceeds 10 parts, the slump may decrease or the long-term strength development may decrease.

Further, the fast-strengthening agent for cement according to the embodiment of the present invention can be sprayed on the concrete surface before hardening to increase the crack resistance. The amount to be sprayed onto the concrete surface is not particularly limited but is preferably from 50 to 800 g / m ^2, more preferably 100 to 600 / m ^2, more preferably 200-500 g / m ^2. Outside the above range, the crack reducing effect may not be sufficient.

Examples of cement referred to here include various commercially available Portland cements such as ordinary, early-strength, moderate-heat, and ultra-fast-strength, and various mixed cements in which fly ash and blast furnace slag are mixed with these various Portland cements. It is also possible to use these as fine powders.

The concrete used in the embodiment of the present invention contains cement and aggregate. Here, as the aggregate, one having a low water absorption rate and a high aggregate strength is preferable.

As the fine aggregate, river sand, mountain sand, lime sand, silica sand and the like can be used, and as the coarse aggregate, river gravel, mountain gravel, lime gravel and the like can be used.

The amount of water used for concrete is preferably 30% or more, more preferably 33 to 55% from the viewpoint of strength development. If the amount of water is less than 30%, cement concrete may not be mixed sufficiently.

The nitric acid and its salt, and the carboxylic acid and its salt, respectively, used in the embodiments of the present invention are materials that function as early-strengthening agents. However, compared to the case where these materials are used individually, when these materials and water are prepared as a fast-strength agent mixed at an appropriate mixing ratio, the individual components show a synergistic effect and are superior. The present inventor has found that a remarkable effect of exhibiting excellent fluidity and strength development can be obtained. The mechanism of effect manifestation of the cement fast-strengthening agent according to the embodiment of the present invention is not desired to be bound by a specific theory, but nitrate ions and carboxylic acid ions supplied from raw materials synergistically. It is considered that the elution of cement components is promoted and the hydration reaction is promoted.

Further, since the embodiment of the present invention is in the form of a liquid using water as a solvent, the promoting effect is higher than the case where a solid nitrate or carboxylate is used as it is. Regarding this, liquids are easier to mix in cement than solids, and an endothermic reaction occurs when nitrate dissolves in water, so if you add it to concrete as a solid, the temperature of the concrete will drop and the reaction will occur. The reason may be that it is suppressed.

Therefore, the early-strengthening agent according to the embodiment of the present invention is excellent in versatility even for cast-in-place concrete, which is particularly difficult to manage. For example, by transporting concrete to the site with an agitator car and adding the early-strengthening agent to the concrete immediately before driving at the site, the concrete and the early-strengthening agent are mixed without segregation, so that early-strength concrete can be appropriately manufactured. ..

Further, since the concentration of the calcium element in the fast-strengthening agent according to the embodiment of the present invention is within a certain range, it does not promote the elution of calcium hydroxide generated by the hydration of cement, and has an effect on long-term strength development. It also has the effect of being small.

Hereinafter, the present invention will be described in detail based on Examples.

"Experimental Example 1"
Nitric acid and its salts, carboxylic acid and its salts, and calcium salt as needed are added to water and stirred for 4 hours to obtain various liquid forms of cement so as to have the types and formulations shown in Tables 1 and 2. An early-strength agent was prepared. The fast-strengthening agent prepared in this way was added to concrete and evaluated.

The basic composition of concrete is 145 kg / m ³ for unit water, 440 kg / m ^{3 for} unit cement, 2.5 kg / m ^{3 for} water reducing agent, 39.4% for s / a, and 4.5% for air, and the temperature is 20 ° C. Slumps of concrete were measured using the fast-strengthening agents of the formulations shown in Table 1 or Table 2 under the environment of. The early-strengthening agent for cement was added by weighing 13.2 kg / m ³ corresponding to 3 parts to 100 parts of cement. Then, the mold was filled with concrete, held at 20 ° C., demolded after 8 hours, and the compressive strength was measured. The results are shown in Tables 1 and 2.

In addition, a separate study was conducted in the case of a formulation in which a fast-strengthening agent for cement was not added, and in the case where nitrate and carboxylate were used alone or in combination in a solid state.

<Material used>
Nitric acid and its salts: [A] concentrated nitric acid, [B] sodium nitrate, [C] magnesium nitrate, [D] potassium nitrate, [E] calcium nitrate, [F] aluminum nitrate, all commercially available carboxylic acids and their salts: [A] formic acid, [b] sodium formate, [c] calcium formate, [d] sodium acetate, [e] sodium oxalate, [f] sodium lactate, [g] sodium aspartate, all commercially available calcium concentration adjustment Salt for use: Calcium nitrate Water: Industrial water Cement: Ordinary Portoland cement, commercial product, brain value 3,200 cm ² / g, specific gravity 3.15
Fine aggregate: From Himekawa, Niigata, Japan, 5 mm below, density 2.62 g / cm ³
Coarse aggregate: Himekawa, Niigata, Japan, 25 mm below, density 2.64 g / cm ³
Water reducing agent: Naphthalene sulfonic acid, trade name "Mighty 150", manufactured by Kao Corporation

<Measurement method>
Slump: Compliant with JIS A 1101 Compression strength: Compliant with JIS A 1108 Concrete is sealed and cured at 20 ° C until the age of 24 hours, and then cured in water at 20 ° C. The concentration of calcium element is calculated by an atomic absorption spectrophotometer.

From Tables 1 and 2, when the concentration of nitric acid and its salt is 30 to 60% and the concentration of carboxylic acid and its salt is 0.1 to 10%, the initial strength is excellently improved, and the slump and long-term strength can be improved. It is understood that the impact is also small. It is also understood that when the concentration of the calcium element is 5 to 20%, the long-term strength development is not hindered and the liquid storage property is also excellent. Among nitric acid and salts thereof, calcium nitrate is particularly desirable, and it can be seen that the combined use of calcium nitrate and sodium nitrate is even more preferable. It can also be seen that among carboxylic acids and salts thereof, formic acid is particularly desirable, and the combined use of formic acid and sodium formate is even more preferable.

When the fast-strengthening agent for cement according to the embodiment of the present invention is used, the initial strength is improved, so that the curing period required to develop the strength required for demolding can be shortened, which leads to an improvement in concrete productivity. I understand.

"Experimental Example 2"
Compared to the configuration in which the calcium nitrate content is 45%, the formic acid content is 5%, and the calcium element concentration is 11% (corresponding to Experiment No. 1-9 of Experimental Example 1), the types and concentrations shown in Table 3 are further added. Alcohol amine or glycerin was added to water and stirred for 4 hours to prepare various quick-strengthening agents for calcium. In addition, the prepared early-strengthening agent for cement was added to concrete and evaluated.

Unit water volume 145 kg / m ³ , unit cement volume 440 kg / m ³ , water reducing agent 2.5 kg / m ³ , s / a 39.4%, air volume 4.5% as the basic composition of concrete, 20 ° C. The concrete slump was measured using the cement quick-strengthening agent of the formulation shown in Table 3 under the environment of. As for the fast-strengthening agent for cement, 13.2 kg / m ^3, which corresponds to 3 parts, was weighed together with water and added to 100 parts of cement. Then, the mold was filled with concrete, held at 20 ° C., demolded after 8 hours, and the compressive strength was measured. The results are shown in Table 3.

<Material used>
Alcohol amine or glycerin: [α] monoethanolamine, [β] diethanolamine, [γ] triethanolamine, [Δ] diisopropanolamine, [ε] glycerin, and other materials are the same as in "Experimental Example 1".

From Table 3, it can be seen that when ethanolamine or glycerin is contained, the initial strength is excellently improved. It can be seen that among ethanolamines, diethanolamine is preferable. It can also be seen that it is preferable that the concentration of ethanolamine is in the range of 1 to 15% and the concentration of glycerin is in the range of 1 to 10% in terms of fluidity and strength development.

"Experimental Example 3"
The basic composition of concrete was 145 kg / m ³ for unit water, 440 kg / m ^{3 for} cement, 2.5 kg / m ^{3 for} water reducing agent, 39.4% for s / a, and 4.5% for air. A concrete slump was measured using several of the cement fast-strengthening agents prepared in "Example 1" in an environment of 20 ° C. at the addition rate shown in Table 4. The addition rate of the fast-strengthening agent for cement was measured as a part with respect to 100 parts of cement. Then, the mold was filled with concrete, held at 20 ° C., demolded after 8 hours, and the compressive strength was measured. The results are shown in Table 4.

In addition, a separate study was also conducted on the case where a formulation without adding a fast-strengthening agent for cement and the case where nitric acid and its salt and carboxylic acid and its salt were used alone.

<Material used>
Same as the material used in "Experimental Example 1".

From Table 4, it can be seen that the cement fast-strengthening agent according to the embodiment of the present invention is excellent in improving the initial strength even when the addition rate of the cement fast-strengthening agent is changed. Further, it is understood that the addition rate of the early-strength agent for cement is 0.1 to 10 parts with respect to 100 parts of cement, because it suppresses fluctuations in slump and is excellent in strength development. ..

"Experimental Example 4"
Unit water volume 145 kg / m ³ , unit cement volume 440 kg / m ³ , water reducing agent 2.5 kg / m ³ , s / a 39.4%, air volume 4.5% concrete is kneaded and kneaded 30 After minutes, the cement quick-strengthening agent prepared in "Experimental Example 1" was added afterwards, the concrete was mixed again, and the slump of the concrete was measured. The early strength agent for cement was added after weighing 13.2 kg / m ³ corresponding to 3 parts with respect to 100 parts of cement. Then, the mold was filled with concrete, held at 20 ° C., demolded after 8 hours, and the compressive strength was measured. The results are shown in Table 5.

In addition, a separate study was also conducted on the case where the precocious agent for cement was not added and the case where nitric acid and its salt and carboxylic acid and its salt were used alone.

<Material used>
Same as the material used in "Experimental Example 1".

From Table 5, it can be seen that the fast-strengthening agent according to the embodiment of the present invention exhibits the same degree of slump and strength development regardless of the timing of addition of the fast-strengthening agent. This is an excellent performance especially when the premixed concrete is carried to the site and the early-strengthening agent is added to the agitator car or the like at the site.

"Experimental Example 5"
Unit water volume 145 kg / m ³ , unit cement volume 440 kg / m ³ , water reducing agent 2.5 kg / m ³ , s / a 39.4%, air volume 4.5% concrete mixed, height 20 cm , A concrete plate with a length of 2 m and a width of 2 m was placed. After casting, after finishing the concrete surface, Experiment No. 200 g / m ^{3 of} 1-9 cement fast-strengthening agent was sprayed. Then, at the age of 28 days, the concrete surface was observed. The crack resistance was evaluated. The results are shown in Table 6. The meanings of the symbols are as follows.
--Those with no cracks
+ 1-2 cracks
++ 3-5 cracks
+++ 6 or more cracks

<Material used>
Same as the material used in "Experimental Example 1".

From Table 6, it can be seen that the occurrence of cracks on the concrete surface can be remarkably suppressed by spraying the cement quick-strengthening agent according to the embodiment of the present invention on the concrete surface.

The early-strengthening agent for cement according to the embodiment of the present invention is excellent in initial strength development, fluidity, and storage stability as compared with conventional materials, and is therefore suitable for civil engineering and construction fields using concrete. is there.

Claims (5)

Nitric acid or its salt is 30% by mass or more and 60% by mass or less.
Carboxylic acid or its salt is 0.1% by mass or more and 10% by mass or less.
A fast-strengthening agent for cement containing water
Moreover, the cement fast-strengthening agent, wherein the concentration of the calcium element in the cement fast-strengthening agent is 5% by mass or more and 20% by mass or less. The early-strengthening agent for cement according to claim 1, further comprising alcohol amine or glycerin. A fast-strength cement comprising 0.1 to 10 parts by mass of the fast-strengthening agent for cement according to claim 1 or 2 with respect to 100 parts by mass of the cement. A method for producing fast-strength concrete, which comprises adding the fast-strengthening agent for cement according to claim 1 or 2 to the ready-mixed concrete of an agitator car. A method for producing concrete, which comprises applying or spraying 100 to 600 g / m ^{2 of the} fast-strengthening agent for cement according to claim 1 or 2 on a concrete surface before hardening.