KR102703816B1 - Cement admixture, and cement composition containing the same - Google Patents

Abstract

The present invention relates to a cement admixture having excellent viscosity properties and material separation resistance, and a cement composition comprising the same.
According to the present invention, it is possible to prevent bleeding that occurs during concrete production and to solve workability and fluidity problems that frequently occur when producing low-carbon concrete (a substitute for cement).

Description

CEMENT ADMIXTURE, AND CEMENT COMPOSITION CONTAINING THE SAME

The present invention relates to a cement admixture having excellent viscosity properties and material separation resistance, and a cement composition comprising the same.

The domestic construction industry is transitioning to smart construction technology to overcome productivity limitations and achieve sustainable future growth, and the need for basic technology development for excellent building materials is increasing accordingly. In particular, the application of 3D printing technology, one of the smart construction technologies, must first be preceded by the development of low-viscosity, high-strength concrete materials that do not require a compaction process during the pouring process.

The cement industry heats calcium carbonate during the production process, emitting a large amount of carbon dioxide ( _CO2 ), a representative greenhouse gas. Carbon dioxide emissions account for 7-8% of global _CO2 emissions and cause environmental pollution and climate change. Even if cement production is reduced by just 1%, it is expected to reduce carbon dioxide emissions by more than 600,000 tons per year, so the use of industrial byproducts such as slag and fly ash and recycled aggregates from crushed waste concrete is actively encouraged, and in the future, carbon reduction capabilities linked to carbon emissions can become a measure of determining a company's cement production volume. The Global Cement and Concrete Association (GCCA) announced its goal of reducing greenhouse gas emissions by 1/4 by 2030 and achieving carbon neutrality by 2050, and the green concrete market area is gradually expanding due to the global green technology paradigm such as carbon dioxide reduction and utilization of recycled resources.

Recently, due to the low-carbon growth policy, the recycling of concrete compositions (slag, fly ash, recycled aggregates, etc.) has increased, and problems such as deterioration of concrete properties, material separation, and large-scale collapse accidents during the pouring process due to increased viscosity have occurred frequently. Therefore, the development of admixture technology with excellent viscosity properties and high resistance to material separation is very urgent.

The object of the present invention is to provide a cement admixture capable of preventing bleeding that occurs during the production of concrete and solving workability and fluidity problems that frequently occur when producing low-carbon concrete (a substitute for cement), and a cement composition containing the same.

In addition, the task of the present invention is to provide a cement admixture and a cement composition including the same, which exhibit excellent effects in maintaining workability and fluidity by significantly improving dispersion stability between cement particles by effectively arranging phosphate groups and ester groups in a polymer chain using acrylate containing phosphate groups.

In order to achieve the above-mentioned task, the present invention,

A repeating unit containing an ethylene glycol group of the following chemical formula 1;

A repeating unit containing a carboxylic acid group of the following chemical formula 2; and

A cement admixture containing a polycarboxylic acid copolymer including at least one phosphate group-containing repeating unit among the following chemical formulas 3 to 5 is provided:

[Chemical Formula 1]

[Chemical formula 2]

[Chemical Formula 3]

[Chemical Formula 4]

[Chemical Formula 5]

(In the chemical formulas 1 to 5 above,

R ₁ to R ₅ are the same or different and are each independently H or CH ₃ ,

R _c is a group of -CH ₂ -CH ₂ - or -CH ₂ -CH(CH ₃ )-, or -CH(CH ₃ )-CH ₂ -,

n is an integer from 1 to 10,

x is an integer from 1 to 10.)

In addition, the present invention provides a cement composition characterized in that it comprises 0.01 to 10 parts by weight of the cement admixture per 100 parts by weight of cement.

According to the present invention, in the case of a polycarboxylic acid copolymer copolymerized using an allylic monomer containing phosphoric acid in the main chain, the phosphate ion forms a chelate with the calcium ion of the cement and strongly binds to improve the dispersing power of the cement particles, thereby reducing the bleeding of the concrete, decreasing the viscosity, and improving the strength without reducing the fluidity, thereby exhibiting the effect of improving workability and productivity. Accordingly, the properties of the concrete can be stably maintained even when recycled resources are used, so that the amount of cement used can be reduced, and it can be applied to ultra-high-performance concrete (UHPC), so that it can be used as an eco-friendly material that can reduce carbon emissions by about 30% compared to general concrete.

Figure 1 is a schematic diagram showing the mechanism of action of a cement admixture according to one embodiment of the present invention.

The present invention is described in detail below.

The cement admixture of the present invention contains a polycarboxylic acid copolymer, wherein the polycarboxylic acid copolymer includes an ethylene glycol group-containing repeating unit of the following chemical formula 1; a carboxylic acid group-containing repeating unit of the following chemical formula 2; and at least one phosphate group-containing repeating unit of the following chemical formulas 3 to 5:

[Chemical Formula 1]

[Chemical formula 2]

[Chemical Formula 3]

[Chemical Formula 4]

[Chemical Formula 5]

(In the chemical formulas 1 to 5 above,

R ₁ to R ₅ are the same or different and are each independently H or CH ₃ ,

R _c is a group of -CH ₂ -CH ₂ - or -CH ₂ -CH(CH ₃ )-, or -CH(CH ₃ )-CH ₂ -,

n is an integer from 1 to 10,

x is an integer from 1 to 10.)

Figure 1 is a schematic diagram showing the mechanism of action of a cement admixture according to one embodiment of the present invention.

The polycarboxylic acid copolymer cement admixture according to the present invention contains a phosphate group and an ester group, and the negatively charged phosphate group and ester group provide stronger adsorption ability with cement particles, and the steric hindrance of the tail portion can improve the dispersibility between cement particles and the resistance to material separation in which water and cement are separated. That is, by introducing a phosphate group and an ester group to the polymer main chain, a chelate is formed with calcium ion, which is a main component in cement, to delay the hydration reaction for a certain period of time, and the dispersing force between particles is increased due to binding with calcium ion, thereby reducing the viscosity of the cement. In addition, the high dispersibility due to the electrostatic repulsion of the carboxyl group and the steric hindrance effect of the long-chain polyether provides excellent water-reducing performance, so that it can be used in a low unit quantity, and can exhibit excellent workability in the mixing of slag powder, which has recently been applied to mixing eco-friendly concrete.

In one embodiment of the present invention, the polycarboxylic acid copolymer can be obtained by copolymerizing an unsaturated polyethylene glycol monomer, one or more unsaturated carboxylic acid monomers, and an allylic monomer containing a phosphoric acid group of the following chemical formulas 6 to 8:

[Chemical formula 6]

[Chemical formula 7]

[Chemical formula 8]

(In the chemical formulas 6 to 8 above,

R _a and R _b are the same or different and are each independently H or CH ₃ ,

R _c is a group of -CH ₂ -CH ₂ - or -CH ₂ -CH(CH ₃ )-, or -CH(CH ₃ )-CH ₂ -,

x is an integer from 1 to 10.)

In one embodiment of the present invention, the unsaturated carboxylic acid monomer may be at least one selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, methyl acrylate, ethyl acrylate, 2-hydroxyethyl acrylate, hydroxyethyl (meth)acrylate, propyl acrylate, butylacrylate, and acrylamide.

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In one embodiment of the present invention, the phosphoric acid group-containing allylic monomer can be obtained through a process as shown in the following reaction schemes 1 and 2.

[Reaction Formula 1]

[Reaction Formula 2]

In one embodiment of the present invention, the polycarboxylic acid copolymer can be represented by the following chemical formula 10:

[Chemical Formula 10]

(In the above chemical formula 10,

R ₁ to R ₃ are the same or different from each other, and are each independently H or CH ₃ ,

x, y, and z are the polymerization molar ratios of each repeating unit, 10~30: 10~30: 100~300, and y>x>z.

n is an integer from 1 to 10.)

In one embodiment of the present invention, the weight average molecular weight of the polycarboxylic acid copolymer may be 15,000 to 70,000. At this time, if the weight average molecular weight of the polycarboxylic acid copolymer is less than the above range, the initial dispersibility of the cement concrete is significantly reduced and the workability is not improved. On the other hand, if it exceeds the above range, the time-dependent dispersion retention of the cement concrete may not be sufficiently improved and sufficient workability may not be provided.

In one embodiment of the present invention, the pH of the polycarboxylic acid copolymer may be 2 to 6.

In the present invention, the polymerization method of the polycarboxylic acid copolymer can be solution polymerization, emulsion polymerization, or bulk polymerization, but aqueous solution polymerization is preferably useful, and the polymerization reaction can be performed in a batch reactor or a continuous reactor.

At this time, the initiator used in the polymerization reaction can be a conventional radical polymerization initiator. The radical initiator used in the water-soluble polymerization is a persulfate salt, and a peroxide such as ammonium persulfate, sodium persulfate, potassium persulfate, and hydrogen peroxide is used, and as an azo compound, 2,2-azobis-2-(2-imidazoline-2yl)propane hydrogen chloride and 2-carbamoyl azoisobutyronitrile are used.

In addition, the polymerization reaction is carried out with a redox polymerization initiator composed of a peroxide and a reducing agent. Useful types of these include a combination of hydrogen peroxide and L-ascorbic acid, a combination of hydrogen peroxide and isoascorbic acid, a combination of sodium persulfate and sodium bisulfite, and a combination of hydrogen peroxide and Mohr's salt. The amount of the polymerization initiator is suitably 0.1 to 10 mol% of the total monomer amount, and preferably 0.5 to 5 mol%. Here, when the amount of the polymerization initiator is less than 0.1 mol% of the total monomer amount, the amount of unreacted monomer increases and the molecular weight increases, thereby increasing the viscosity of the polymer. On the other hand, when it is 10 mol% or more, the molecular weight of the polymer is too small to exhibit the desired characteristics, which is not preferable.

In order to obtain a useful range of molecular weights in the present invention, the pH of the reaction monomer mixture is adjusted to between pH 2 and 5 using caustic soda, and a chain transfer agent, which is a molecular weight regulator, is used. When the pH is between 2 and 5, the reactivity of the polymer is reduced, making it impossible to obtain a polymer of the desired molecular weight. Copolymerization is performed between pH 2 and 5, and the pH is adjusted to the desired level after polymerization is completed.

The above chain transfer agents include mercaptoethanol, thioglycerol, thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, 2-mercaptoethanesulfonic acid, isopropanol, phosphoric acid, hypophosphorous acid and its salts (sodium hypophosphite, hypophosphite). These chain transfer agents may be used in combination of one or more, and the appropriate amount to be used is 0.1 to 5 mol% of the monomer. At this time, if 0.1 mol% or less is used, the effect as a molecular weight regulator does not appear, making it difficult to control the molecular weight, so an insoluble polymer with a large molecular weight is produced, and if 5 mol% or more is used, a polymer at the oligomer level with too small a molecular weight is produced, making it impossible to exhibit the desired properties.

In the present invention, the temperature of the polymerization reaction can be determined according to the half-life of the initiator used in the polymerization reaction. When a persulfate is used as the initiator, the polymerization reaction temperature is suitably in the range of 40 to 90°C. When an oxidation-reduction system is used as the initiator, the reaction temperature is suitably in the range of 30 to 80°C, and the polymerization reaction time is suitably in the range of 2 to 6 hours. If the polymerization reaction time is less than 2 hours or more than 6 hours, the reaction yield and productivity are lowered, which is not desirable.

The cement admixture (concrete admixture) of the present invention is composed of a copolymer synthesized by the method presented above, and is preferably in an aqueous solution state considering workability.

The cement admixture (concrete admixture) of the present invention may also contain other additives. Such cement additives include air-entraining agents, anti-foaming agents, early strength agents and early strength accelerators, retarders, waterproofing agents, corrosion inhibitors, and crack-reducing agents.

At this time, fatty acid soap, unsaturated fatty acid salt, linear alkylbenzene sulfonic acid, sodium polyoxyalkyl sulfate, sodium alkyl sulfate salt, sodium alpha-olefin sulfonate, alkane sulfonate, polyoxyethylene alkyl (phenyl) ether, betaine, fatty acid alkanolamide, amine oxide, sodium alkenyl sulfosuccinate, etc. can be used as air-entraining agents.

At this time, polyoxyalkylene defoaming agents, alcohol defoaming agents, amide defoaming agents, phosphate defoaming agents, metal soap defoaming agents, fatty acid ester defoaming agents, mineral oil defoaming agents, fat or oil defoaming agents, etc. can be used as defoaming agents.

At this time, calcium chloride, calcium nitrite, calcium nitrate, magnesium chloride, iron chloride, alkanolamine, aluminum sulfate, thiosulfate, etc. can be used as pre-strengthening agents and pre-strengthening accelerators.

At this time, formic acid and its salts, gluconic acid and its metal salts, citric acid and its metal salts, glucose, saccharose, oligosaccharides, dextrin, sorbitol, xylitol, glycerin, etc. can be used as delaying agents.

At this time, fatty acids and their salts, fatty acid esters, fats and oils, silicone, paraffin, asphalt, wax, etc. can be used as waterproofing agents.

At this time, nitrates, phosphates, zinc oxide, etc. can be used as corrosion inhibitors.

At this time, alkanediols such as polyoxyalkyl ether and 2-methyl-2,4-pentanediol can be used as crack reducing agents.

The cement composition of the present invention comprises 0.5 to 3 parts by weight of a cement admixture containing the above-mentioned polycarboxylic acid copolymer per 100 parts by weight of cement.

Hereinafter, preferred examples and experimental examples are presented to help understand the present invention. However, the following examples are provided only to help understand the present invention more easily, and the content of the present invention is not limited by the examples. Unless otherwise specified, % means weight %.

Example 1: Synthesis of polycarboxylic acid copolymer containing phosphoric acid

A 2L polymerization reactor equipped with a thermometer, a condenser, a stirrer, a dropping funnel, and a temperature controller was placed, and 440 g of VPEG (molecular weight 2400, Polyethylene glycol mono alkyl allyl ether, CAS-No. 31497-33-3) was placed in the polymerization reactor, 160 g of distilled water was added, and the temperature was raised to 70℃. In dropping funnel 1, 48 g of 2-(bis(2-hydroxyethyl phosphonate)amino)ethyl acrylate, 4 g of 2-hydroxyethyl acrylate, 50 g of acrylic acid, and 1.5 g of 2-mercaptoethanol were mixed with 200 g of distilled water and mixed. In dropping funnel 2, 4.0 g of ammonium persulfate was added to 100 g of distilled water and completely dissolved. The temperature of the polymerization reactor was raised to 60°C, and the dropping funnels 1 and 2 were simultaneously added to conduct a polymerization reaction for 3 hours. After completion of the addition, a maturation reaction was conducted at 70°C for 2 hours, and then cooled to room temperature to synthesize a transparent copolymer with a solid content of 51.2% and a pH of 2.2.

Example 2

A 2L polymerization reactor equipped with a thermometer, a condenser, a stirrer, a dropping funnel, and a temperature controller was placed, and 440 g of VPEG (molecular weight 2400, Polyethylene glycol mono alkyl allyl ether, CAS-No. 31497-33-3) was placed in the polymerization reactor, 160 g of distilled water was added, and the temperature was raised to 70℃. In dropping funnel 1, 200 g of distilled water was added to a monomer solution mixed with 48 g of 2-hydroxyethyl methacrylate phosphate, 4 g of 2-hydroxyethyl acrylate, 50 g of acrylic acid, and 1.5 g of 2-mercaptoethanol, and mixed. In dropping funnel 2, 4.0 g of ammonium persulfate was added to 100 g of distilled water and completely dissolved. The temperature of the polymerization reactor was raised to 60°C, and dropping funnels 1 and 2 were simultaneously added to conduct a polymerization reaction for 3 hours. After completion of addition, a maturation reaction was conducted at 70°C for 2 hours, and then cooled to room temperature to synthesize a transparent copolymer with a solid content of 51.2% and a pH of 2.3.

Example 3

A 2L polymerization reactor equipped with a thermometer, a condenser, a stirrer, a dropping funnel, and a temperature controller was placed, and 440 g of VPEG (molecular weight 2400, Polyethylene glycol mono alkyl allyl ether, CAS-No. 31497-33-3) was placed in the polymerization reactor, 160 g of distilled water was added, and the temperature was raised to 70℃. In dropping funnel 1, 48 g of poly(oxy-1,2-ethanediyl)-alpha-2-propen-1-yl-omega-hydroxy phosphate, 4 g of 2-hydroxyethyl acrylate, 50 g of acrylic acid, and 1.5 g of 2-mercaptoethanol were mixed with 200 g of distilled water to a monomer solution and mixed. In dropping funnel 2, 4.0 g of ammonium persulfate was added to 100 g of distilled water and completely dissolved. The temperature of the polymerization reactor was raised to 60°C, and dropping funnels 1 and 2 were simultaneously added to conduct a polymerization reaction for 3 hours. After completion of addition, a maturation reaction was conducted at 70°C for 2 hours, and then cooled to room temperature to synthesize a transparent copolymer with a solid content of 51.2% and a pH of 2.3.

Comparative Example 1

A 2L polymerization reactor equipped with a thermometer, a condenser, a stirrer, a dropping funnel, and a temperature controller was placed, and 440 g of VPEG (molecular weight 2400) was placed in the polymerization reactor, 160 g of distilled water was added, and the temperature was raised to 70℃. In dropping funnel 1, 200 g of distilled water was added to a monomer solution mixed with 4 g of 2-hydroxyethyl acrylate, 50 g of acrylic acid, and 1.5 g of 2-mercaptoethanol and mixed. In dropping funnel 2, 4.0 g of ammonium persulfate was added to 100 g of distilled water and completely dissolved. The temperature of the polymerization reactor was raised to 60℃, and dropping funnels 1 and 2 were simultaneously dropped to conduct a polymerization reaction for 3 hours. After completion of the injection, a maturation reaction was performed at 70°C for 2 hours and then cooled to room temperature to synthesize a transparent copolymer with a solid content of 49.5% and a pH of 2.5.

Experimental Example 1: Mortar Flow Experiment

The concrete chemical additive samples manufactured in the above Examples 1 to 3 and Comparative Example 1 were prepared using distilled water to adjust the concentration to 20%. 1,350 g of ISO standard sand and 900 g of cement were placed in a mortar mixer bowl, and the additive (20%) sample was added to 315 g of water in a beaker and mixed well. The contents of the beaker were placed in the mortar mixer bowl containing the ISO standard sand and cement and mixed at 120 rpm for 1 minute. Then, the cement powder was thoroughly scraped off the wall surface, stirred at 150 rpm for 2 minutes with the mortar mixer, and then placed in a flow cone in three portions and compacted to lift it up. The length and time were measured when the flow was finished.

The results of mortar flow experiments of the polymers of Examples 1 to 3 and Comparative Example 1 were measured and are shown in Table 1 below.

Among the phosphoric acid monomers of Example 1, the polymer using 2-(bis(2-hydroxyethyl phosphonate)amino)ethyl acrylate had the best flow reaching time, and Comparative Example 1 without the phosphoric acid monomer showed a significantly increased flow reaching time.

Experimental Example 2: Concrete Mix Application Experiment

According to the mixing conditions described in the concrete mixing ratio of Table 2 below, each concrete mixing experiment was prepared. Using a 50 L concrete forced mixing mixer, portland cement (specific gravity = 3.16), sand (specific gravity = 2.65), and gravel (specific gravity = 2.66) were sequentially added and mixed for 30 seconds. Then, 0.7%, 0.9%, and 1.2% of each example and comparative example were mixed, added together with mixing water, and mixed for 3 minutes to conduct an experiment. The L-flow test and compressive strength of the concrete of each experimental example prepared above were obtained as follows, and the results are summarized and presented in Table 3 below.

1. W/C: Water/concrete ratio

2. S/A: Aggregate ratio (sand/sand+gravel)

L-Flow was measured by pouring a certain amount of concrete mix into an L-Flow measuring device, opening the lid on one side, measuring the distance it flows, and then measuring the time it takes to flow to the final distance.

For compressive strength, the strength was measured at 1, 7, and 28 days according to JIS-A1108.

To examine the fluidity of the concrete mixtures of the polymers manufactured in Examples 1 to 3 and Comparative Example 1, the results of the L-flow experiment and the compressive strength measurement experiment are shown in Table 3 below.

Claims (8)

Cement admixture containing a polycarboxylic acid copolymer characterized by the following chemical formula 10:
[Chemical Formula 10]

(In the above chemical formula 10,
R ₁ to R ₃ are the same or different from each other, and are each independently H or CH ₃ ,
x, y, and z are the polymerization molar ratios of each repeating unit, 10~30: 10~30: 100~300, and y>x>z.
n is an integer from 1 to 10.) In the first paragraph, the polycarboxylic acid copolymer
Unsaturated polyethylene glycol monomer;
One or more unsaturated carboxylic acid monomers; and
Cement admixture containing a polycarboxylic acid copolymer characterized by copolymerizing an allylic monomer containing a phosphoric acid group of the following chemical formulas 6 to 8:
[Chemical formula 6]

[Chemical formula 7]

[Chemical formula 8]

(In the chemical formulas 6 to 8 above,
R _a and R _b are the same or different and are each independently H or CH ₃ ,
R _c is a group of -CH ₂ -CH ₂ - or -CH ₂ -CH(CH ₃ )-, or -CH(CH ₃ )-CH ₂ -,
x is an integer from 1 to 10.) delete In the second paragraph, the unsaturated carboxylic acid monomer
A cement admixture containing a polycarboxylic acid copolymer, characterized in that at least one selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, methyl acrylate, ethyl acrylate, 2-hydroxyethyl acrylate, hydroxyethyl (meth) acrylate, propyl acrylate, butylacrylate, and acrylamide. delete A cement admixture containing a polycarboxylic acid copolymer, characterized in that in claim 1, the weight average molecular weight of the polycarboxylic acid copolymer is 15,000 to 70,000. A cement admixture containing a polycarboxylic acid copolymer, characterized in that in claim 1, the pH of the polycarboxylic acid copolymer is 2 to 6. A cement composition characterized by comprising 0.5 to 3 parts by weight of a cement admixture according to any one of claims 1, 2, 4, 6 and 7 per 100 parts by weight of cement.