Medium-flow concrete composition with improved workability and material separation resistance through viscosity control

Abstract

The present invention relates to a medium-flow concrete composition, and more specifically, to a concrete admixture comprising a polycarboxylate ether-based copolymer compound and a polycarboxylic acid-based water-reducing agent, which has the effect of providing excellent fluidity through viscosity control and excellent resistance to material separation while maintaining the compressive strength of ordinary concrete.

Description

Technology Field

[0001] The present invention relates to a medium-flow concrete composition with improved workability and resistance to material separation through the control and suppression of viscosity of medium-flow concrete. Specifically, the invention relates to a medium-flow concrete composition with excellent workability and resistance to material separation, characterized by comprising a concrete admixture comprising a binder including cement, aggregate, water, and a polycarboxylate ether-based copolymer compound copolymerized using an aromatic macromonomer. Background Technology

[0003] Medium-flow concrete can be defined as concrete that has enhanced fluidity compared to ordinary concrete, thereby achieving a level of fluidity comparable to high-flow concrete. Manufacturing it to possess excellent fluidity in the general strength range requires a different approach from conventional concrete manufacturing methods involving low water-cement ratios and admixture substitution. In the conventional manufacturing of medium-flow concrete, fluidity can be enhanced by adding high-water-reducing admixtures to the general strength concrete mix; however, this can lead to problems such as high water-cement ratios, material segregation occurring very easily due to the low powder content, and excessively high viscosity.

[0004] When manufacturing medium-flow concrete using low-quality aggregates, high-water-reducing admixtures or cellulose thickeners have been used to satisfy the design compressive strength of the concrete and the flow of 400 to 500 mm required for medium-flow concrete. However, this causes excessive viscosity and material segregation, impedes concrete pumping and workability, and results in problems such as poor construction due to incomplete filling, reduced compressive strength, and poor appearance.

[0005] Therefore, there is a need to develop a medium-flow concrete composition that can exhibit high fluidity in general concrete within the normal strength range, thereby effectively controlling viscosity while improving resistance to material segregation.

[0006] Korean Patent Publication No. 10-2023-0036643 relates to a medium-flow concrete composition and discloses a medium-flow concrete composition characterized by including a polycarboxylic acid-based water reducer, a cellulose thickener, and a shrinkage reducing agent. The problem to be solved

[0008] The present invention was devised to solve the problems of the aforementioned prior art and aims to provide a medium-flow concrete composition having excellent workability and resistance to material separation by including a concrete admixture containing a polycarboxylate ether-based copolymer compound. means of solving the problem

[0010] To achieve the above objective, the present invention comprises a concrete admixture, aggregate, binder, and water, and

[0011] The above-mentioned concrete admixture comprises a polycarboxylate ether-based copolymer compound and a polycarboxylic acid-based water reducer, and

[0012] The above polycarboxylate ether-based copolymer compound comprises an aromatic macromonomer, an unsaturated carboxylic acid, a chain transfer agent, a solvent, and a polymerization initiator, thereby providing a medium-flow concrete composition.

[0013] In a medium-flow concrete composition according to one embodiment of the present invention, the polycarboxylate ether-based copolymer compound is characterized by comprising, based on 100 parts by weight of the aromatic macromonomer, 0.01 to 5 parts by weight of the chain transfer agent, 70 to 2,000 parts by weight of the solvent, and 0.01 to 10 parts by weight of the polymerization initiator.

[0014] The above unsaturated carboxylic acid is characterized by comprising one or more selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and mesaconic acid.

[0015] The weight mixing ratio of the above aromatic macromonomer and the unsaturated carboxylic acid is characterized as being greater than 1:0 and less than or equal to 1,050.

[0016] The above polycarboxylate ether-based copolymer compound and polycarboxylic acid-based water reducer are mixed in a weight ratio of 1:1 to 1:20.

[0017] The above polymerization initiator comprises one or more selected from the group consisting of t-amyl peroxy-2-ethylhexanoate, 2,2'-azobis-isobutyronitrile (AIBN), benzoyl peroxide, lauroyl peroxide, 2,2'-azobis-(2,4-dimethylvaleronitrile), 2,2'-azobis-(4-methoxy-2,4-dimethylvaleronitrile), t-butylperoxypivalate, 1,1'-bis-(bis-t-butylperoxy)cyclohexane, and combinations thereof.

[0018] The above-mentioned medium-flow concrete composition is characterized by comprising, with respect to the total weight of the above-mentioned medium-flow concrete composition, 1 to 20 parts by weight of the concrete admixture, 40 to 80 parts by weight of the aggregate, 1 to 50 parts by weight of the binder, and 5 to 20 parts by weight of the water.

[0019] The above binder comprises one or more selected from the group consisting of ordinary Portland cement, rapid-hardening Portland cement, lime cement, slag cement, blast furnace slag cement, Portland pozzolan cement, fly ash, bottom ash, gypsum cement, lime cement, silica fume, and low-heat cement.

[0020] The above aggregate is fine aggregate composed of crushed sand, washed sand, and recycled aggregate with a particle size of 0.01 to 5 mm; and

[0021] It includes one or more types selected from the group consisting of crushed stone, crushed slag, natural gravel, crushed gravel, and coarse aggregate composed of recycled aggregate with a particle size of 5 to 25 mm.

[0022] The above-mentioned medium-flow concrete composition is characterized by having a viscosity of 35 to 80 Pa*s.

[0023] The above-mentioned medium-flow concrete composition is characterized by having a static yield stress of 1,000 to 2,000 Pa. Effects of the invention

[0025] The medium-flow concrete composition according to the present invention includes a concrete admixture comprising a polycarboxylate ether-based copolymer compound and a polycarboxylic acid-based water reducer, thereby providing the effect of having excellent fluidity while maintaining the strength of ordinary concrete.

[0026] In addition, by controlling and suppressing the viscosity of concrete, it is possible to secure concrete properties suitable for the construction site and pouring section, thereby providing economic benefits such as shortening the construction period through improved constructability.

[0027] In addition, when manufacturing ready-mixed concrete using medium-flow concrete according to the present invention, excellent productivity can be provided due to improved workability and resistance to material segregation.

[0028] It can be seen that the medium-flow concrete according to the present invention exhibits superior yield stress and viscosity compared to ordinary concrete, thereby providing an excellent viscosity control effect. Specific details for implementing the invention

[0030] Specific embodiments of the invention are described in detail below. However, the concept of the present invention is not limited to the presented embodiments. Those skilled in the art who understand the concept of the present invention may easily propose other inventions that are inferior or other embodiments included within the scope of the concept of the present invention by adding, changing, or deleting other components within the same scope of the concept, and such are also to be considered to be included within the scope of the concept of the present invention.

[0031] Additionally, the terms used in this invention are used merely to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. Throughout the specification of this invention, the term 'comprising' any component means that, unless specifically stated otherwise, it does not exclude other components but may include additional components. The invention will be described in detail below.

[0032] A medium-flow concrete composition according to one embodiment of the present invention comprises a concrete admixture, aggregate, binder, and water.

[0033] The above concrete admixture includes a polycarboxylate ether-based copolymer compound and a polycarboxylic acid-based water reducer.

[0034] The above polycarboxylate ether-based copolymer compound comprises an aromatic macromonomer, an unsaturated carboxylic acid, a chain transfer agent, a solvent, and a polymerization initiator, thereby providing a medium-flow concrete composition.

[0035] The above aromatic macromonomer is represented by the following chemical formula 1.

[0036] [Chemical Formula 1]

[0037]

[0038] (In the above chemical formula 1,

[0039] R1 to R3 are each independently hydrogen or C1-C 20 It is an alkyl group, and

[0040] R4 is hydrogen, C1-C 20 It is an alkyl group or a phenyl group, and

[0041] n is an integer selected from 1 to 200, and

[0042] m is an integer selected from 0 to 100, and

[0043] p may be an integer selected from 0 to 1.

[0044] The above polycarboxylate ether-based copolymer compound may be prepared by reacting it to essentially include an aromatic macromonomer represented by Chemical Formula 1. In this case, the aromatic macromonomer may have a structure including a benzene ring as shown in Chemical Formula 1. That is, the medium-flow concrete composition according to the present invention may have the effect of preventing material separation due to the floating of lightweight aggregates and improving workability compared to existing medium-flow concrete compositions by including an aromatic macromonomer represented by Chemical Formula 1.

[0045] The above macromonomer refers to a large molecule having a single terminal group acting as a monomer, and in Chemical Formula 1, the terminal group may refer to a carbon-carbon double bond at the left end. That is, polymerization may occur through the carbon-carbon double bond site.

[0046] In the above Chemical Formula 1, preferably R1 to R3 are each independently hydrogen or C1-C 10 It is an alkyl group, R4 is hydrogen, C1-C 10It may be an alkyl group or a phenyl group, n may be an integer selected from 1 to 100, and m may be an integer selected from 0 to 50; more preferably, R1 to R3 are each independently hydrogen or a C1-C5 alkyl group, R4 is hydrogen, a C1-C5 alkyl group, or a phenyl group, n may be an integer selected from 1 to 100, and m may be an integer selected from 0 to 25; even more preferably, R1 is a C1-C5 alkyl group, R2 to R4 are each hydrogen, n may be an integer selected from 1 to 80, and m may be an integer selected from 0 to 10. Meanwhile, according to one embodiment of the present invention, the aromatic macromonomer represented by Chemical Formula 1 may refer to a PPEG-MAA compound represented by Chemical Formula 1-1 below.

[0047] [Chemical Formula 1-1]

[0048]

[0049] The above polycarboxylate ether-based copolymer compound may be prepared by reacting one or more selected from the group consisting of the aromatic macromonomer represented by Chemical Formula 1 and the unsaturated carboxylic acid. In some cases, it may be optionally copolymerized with the aromatic macromonomer represented by Chemical Formula 1.

[0050] The above unsaturated carboxylic acid is characterized by comprising one or more selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and mesaconic acid, and preferably comprises methacrylic acid represented by the following chemical formula 2-1 and / or acrylic acid represented by the following chemical formula 2-2.

[0051] [Chemical Formula 2-1]

[0052]

[0053] [Chemical Formula 2-2]

[0054]

[0055] The above-mentioned aromatic macromonomer and unsaturated carboxylic acid are characterized by a weight mixing ratio of greater than 1:0 to less than or equal to 1,050. More specifically, the content of unsaturated carboxylic acid per 100 parts by weight of the aromatic macrocompound represented by Chemical Formula 1 may be 1 to 20 parts by weight.

[0056] In one embodiment of the present invention, the polycarboxylate ether-based copolymer compound may be prepared by reacting it further including a chain transfer agent, a solvent, and a polymerization initiator.

[0058] The above chain transfer agent may comprise a substance selected from the group consisting of 3-mercaptopropionic acid, n-hexyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, thioglycolic acid, 2-mercaptoethanol, α-methylstyrene dimer, and combinations thereof, and according to one embodiment of the present invention, the chain transfer agent may use 3-mercaptopropionic acid. Meanwhile, the content of the above chain transfer agent may be 0.01 to 5 parts by weight per 100 parts by weight of the aromatic macrocompound represented by Formula 1. At this time, if the content of the above chain transfer agent is less than 0.01 parts by weight, a problem may occur in which the efficiency of increasing the polymerization or copolymerization reaction decreases, and if it exceeds 5 parts by weight, the synergistic effect obtained by adding the chain transfer agent is reduced, so it may be inefficient from an economic perspective.

[0059] The above solvent may be distilled water; alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, etc.; aromatic or aliphatic hydrocarbons such as cyclohexane, n-hexane, etc.; ester compounds such as ethyl acetate, etc.; ketone compounds such as acetone, methyl ethyl ketone, etc., but due to the solubility of the raw monomer and the resulting copolymer, it is preferable to use one or more selected from the group consisting of distilled water and lower alcohols having 1 to 4 carbon atoms, and among these, using distilled water as a solvent may be more preferable in that the desoldering process can be omitted. Meanwhile, the content of the above solvent may be 70 to 2,000 parts by weight per 100 parts by weight of the aromatic macrocompound represented by Chemical Formula 1.

[0060] The polymerization initiator may comprise a substance selected from the group consisting of t-amyl peroxy-2-ethylhexanoate, 2,2'-azobis-isobutyronitrile (AIBN), 2,2'-azobis-(2,4-dimethylvaleronitrile), 2,2'-azobis-(4-methoxy-2,4-dimethylvaleronitrile), benzoyl peroxide, lauroyl peroxide, t-butylperoxypivalate, 1,1'-bis-(bis-t-butylperoxy)cyclohexane, and combinations thereof. In this case, the initiator may be added in an amount of 0.01 to 10 parts by weight per 100 parts by weight of the aromatic macrocompound represented by Formula 1, and reacted for 1 to 10 hours, preferably for 2 to 8 hours. If the reaction time is less than 1 hour, the efficiency of copolymer production may decrease, and if it exceeds 10 hours, the time becomes too long and may not be economically efficient.

[0061] The weight-average molecular weight (Mw) of the above polycarboxylate ether-based copolymer compound may be 1,000 to 500,000, and preferably 5,000 to 300,000. If the weight-average molecular weight (Mw) of the above polycarboxylate ether-based copolymer compound is less than 1,000, the dispersion performance is reduced, and if it exceeds 300,000, a problem may occur in which the copolymerization reaction efficiency decreases.

[0062] In a medium-flow concrete composition according to one embodiment of the present invention, the polycarboxylate ether-based copolymer compound is characterized by comprising, based on 100 parts by weight of the aromatic macromonomer, 0.01 to 5 parts by weight of the chain transfer agent, 70 to 2,000 parts by weight of the solvent, and 0.01 to 10 parts by weight of the polymerization initiator.

[0063] The above polycarboxylic acid (PCE)-based water reducer may include a polycarboxylic acid ether-based copolymer compound, and although there are no significant limitations on the type of the polycarboxylic acid ether-based copolymer compound, for example, it may be prepared by reacting one or more of the compounds represented by the following chemical formulas 5 to 9.

[0064] [Chemical Formula 5]

[0065]

[0066] [Chemical Formula 6]

[0067]

[0069] [Chemical Formula 7]

[0070]

[0072] [Chemical Formula 8]

[0073]

[0075] [Chemical Formula 9]

[0076]

[0077] At this time, in the above chemical formulas 5 to 9, n may each be an integer independently selected from 1 to 100.

[0078] By additionally mixing the above-mentioned polycarboxylic acid-based water-reducing agent, it is possible to prevent material separation caused by the floating of lightweight aggregates that are porous and have a low specific gravity, and to provide the effect of improving workability.

[0079] The above polycarboxylate ether-based copolymer compound and polycarboxylic acid-based water reducer are mixed in a weight ratio of 1:1 to 1:20. If the weight ratio is less than 1:1, the effect of increasing concrete workability and resistance to material separation due to the addition of the additive may be negligible, and if the weight ratio exceeds 1:20, the content of the polycarboxylate ether-based copolymer compound is relatively low, which may result in a problem where the function as an admixture is reduced.

[0081] The above-mentioned medium-flow concrete composition is characterized by comprising, with respect to the total weight of the above-mentioned medium-flow concrete composition, 1 to 20 parts by weight of the concrete admixture, 40 to 80 parts by weight of the aggregate, 1 to 50 parts by weight of the binder, and 5 to 20 parts by weight of the water.

[0082] The above aggregate is a construction mineral material that serves as the base of the above-mentioned heavy-flow concrete composition and can be bound together by a binder to form a single mass.

[0083] The above aggregate is fine aggregate composed of crushed sand, washed sand, and recycled aggregate with a particle size of 0.01 to 5 mm; and

[0084] It includes one or more types selected from the group consisting of crushed stone, crushed slag, natural gravel, crushed gravel, and coarse aggregate composed of recycled aggregate with a particle size of 5 to 25 mm.

[0085] The above fine aggregate refers to aggregate with a particle size that passes 100% through a standard 5mm sieve, and the above fine aggregate may preferably be crushed sand, but is not limited thereto.

[0086] The above coarse aggregate refers to aggregate with a particle size that remains 100% on a standard 5mm sieve, and the above coarse aggregate may be crushed gravel, but is not limited thereto.

[0087] The content of the aggregate may be 40 to 80 parts by weight per 100 parts by weight of the total content of the medium-flow concrete composition. If the content of the aggregate is less than 40 parts by weight, the compressive strength of the concrete increases when concrete is manufactured from the medium-flow concrete composition, but at the same time, the unit cost of manufacturing the concrete increases. If the content of the aggregate exceeds 80 parts by weight, separation between the aggregate and the binder may occur, and there is a risk that the quality of the concrete will deteriorate.

[0088] The fine aggregate ratio (S / a) in the above medium-flow concrete composition may be 35 to 65%. Here, the fine aggregate ratio (S / a) refers to the percentage of the absolute volume of fine aggregate (S) relative to the total aggregate (fine aggregate + coarse aggregate, a). If the fine aggregate ratio (S / a) of the above medium-flow concrete composition is less than 35%, the unit water and unit cement content decrease, resulting in reduced workability and a problem where the concrete becomes coarse and separates from other materials. If the fine aggregate ratio (S / a) of the above medium-flow concrete composition exceeds 65%, problems such as increased drying shrinkage, settlement cracks, and plastic shrinkage cracks may occur.

[0089] The above binder serves to provide durability and strength to the concrete by improving and maintaining the adhesion between the aggregates (e.g., fine aggregate or coarse aggregate) included in the concrete-forming composition.

[0090] The above binder comprises one or more selected from the group consisting of ordinary Portland cement, rapid-hardening Portland cement, lime cement, slag cement, blast furnace slag cement, Portland pozzolan cement, fly ash, bottom ash, gypsum cement, lime cement, silica fume, and low-heat cement.

[0091] The content of the above binder may be 1 to 50 parts by weight with respect to the total weight of the medium-flow concrete composition. If the content of the above binder is within the above range with respect to 100 parts by weight of the total content of the medium-flow concrete composition, the manufacturing cost of the concrete can be reduced and watertightness can be increased.

[0092] The water-to-binder ratio (W / B) of the above concrete-forming composition may be 20 to 60%. According to one embodiment of the present invention, the water-to-binder ratio (W / B) of the above medium-flow concrete composition may be 40 to 50%. Here, the water-to-binder ratio (W / B) refers to a percentage of the amount of water (W) relative to the binder (B). If the water-to-binder ratio (W / B) of the above medium-flow concrete composition is less than 20%, the fluidity of the concrete produced from the above medium-flow concrete composition may be reduced, and if the water-to-binder ratio (W / B) of the above medium-flow concrete composition is greater than 60%, the durability and strength of the concrete produced from the above medium-flow concrete composition may be reduced.

[0094] The medium-flow concrete composition according to the present invention includes a concrete admixture and provides the effect of having excellent yield stress and viscosity of the concrete composition.

[0095] The content of the above concrete admixture may include 1 to 20 parts by weight of the above concrete admixture with respect to the total weight of the above medium-flow concrete composition, and preferably 5 to 10 parts by weight.

[0097] The medium-flow concrete composition according to the present invention is characterized by having a viscosity of 35 to 80 Pa*s.

[0098] The above-mentioned medium-flow concrete composition is characterized by having a static yield stress of 1,000 to 2,000 Pa.

[0100] Yield stress and plastic viscosity are indicators related to the fluidity and resistance to segregation of concrete, respectively; therefore, a medium-flow concrete composition must possess low yield stress and an appropriate level of plastic viscosity. When possessing the above static yield stress and viscosity, the medium-flow concrete composition according to the present invention provides the effect of having excellent fluidity while also possessing excellent resistance to segregation.

[0102] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0104] < Examples >

[0105] Comparative Manufacturing Example : PCE Suppressant

[0106] A concrete admixture was prepared by adding caustic soda to a solution of a polycarboxylic acid-based water reducer with a solid content of 20%, which is a water reducer generally used to control the fluidity of concrete compositions, and adjusting the pH to 6.0.

[0108] Preparation Example 1: Concrete admixtures containing aromatic macrocompounds

[0109] 1. Preparation of PPEG-MAA Compound

[0110] 59 parts by weight of a phenol polyethylene glycol ether compound (weight-average molecular weight: 2,000) were placed in a reactor, and 2 parts by weight of sulfuric acid were added. After adding 0.03 parts by weight of phenothiazine as a polymerization inhibitor, 6 parts by weight of meta-acid and 3 parts by weight of toluene were added. Once the addition was complete, the temperature was raised to approximately 120°C. After reacting for about 7 hours, 28 parts by weight of distilled water and 1 part by weight of caustic soda were added and stirred to prepare the PPEG-MAA compound.

[0112] 2. Preparation of polycarboxylate ether-based copolymer compounds

[0113] A mixture was prepared comprising 23 parts by weight of the PPEG-MAA prepared in 1. above, 1.1 parts by weight of methacrylic acid and 1.1 parts by weight of acrylic acid, 0.33 parts by weight of 3-mercaptopropionic acid as a chain transfer agent, and 72.8 parts by weight of distilled water as a solvent, and stirred at 80°C. Subsequently, 0.3 parts by weight of t-amyl peroxy-2-ethylhexanoate as a polymerization initiator were added and reacted for 3 hours to prepare a polycarboxylic acid ether copolymer compound (solid content 20%, weight-average molecular weight 100,000).

[0115] 3. Preparation of Admixtures

[0116] 30 parts by weight of the polycarboxylic acid ether-based copolymer compound prepared in 2. above was added to 100 parts by weight of the admixture prepared in the above comparative manufacturing example, and caustic soda was added to adjust the pH to 6.0 to prepare the admixture.

[0118] Examples 1: Preparation Example including 1 Jungyudong concrete .

[0119] To manufacture an example according to the present invention, a medium-flow concrete composition was prepared as shown in the composition of Table 1 below, including the concrete admixture prepared in the above manufacturing example.

[0120] Fine aggregate (crushed sand) and coarse aggregate were added to a pan mixer (model name: WJ-226, Woojin Precision, 60L) and dry-mixed for 2 to 3 minutes. Subsequently, a binder was added to the pan mixer and dry-mixed for 2 to 3 minutes. Then, water and a concrete admixture prepared according to Example 1 were added and stirred to produce a medium-flow concrete composition.

[0122] Comparative example 1: Comparative manufacturing example inclusive Jungyudong concrete.

[0123] To evaluate the effect of the concrete admixture according to the present invention on the physical properties of medium-flow concrete, medium-flow concrete was prepared by adding the PCE water-reducing agent of the comparative example as a concrete admixture.

[0125] Type W / B (%) S / a (%) Unit volume mass (kg / m³) 3 ) AD (B x % ) W Binder S (Busunsa) G (25mm) C (OPC) FA BS Comparative example 1 48.8 48.5 175 251 54 54 848 918 1.1 Examples 1 W / B: Water / Binder W: Mixing Water C: Class 1 Ordinary Portland Cement S: Washed Sand S: Crushed sand G: Coarse aggregate AD: Amount of high-performance water reducer

[0127] Experimental Example 1: Flow properties of concrete

[0128] To evaluate the fluidity and physical properties of the medium-flow concrete compositions prepared according to Example 1 and Comparative Example 1, static yield stress, viscosity, flow, and compressive strength over time were measured and are shown in Table 2 below.

[0129] Static yield stress is a method of measuring the stress at the moment when the fluid actually begins to move when shear stress is applied while the fluid is completely at rest. When comparing Example 1 using a concrete admixture with Comparative Example 1 using a general water-reducing agent, it was found that the static yield stress was measured to be lower in the medium-flow concrete composition of Example 1.

[0130] In addition, viscosity measurements to evaluate fluidity also showed a lower viscosity in Example 1, indicating that the medium-flow concrete composition according to Example 1 can provide excellent fluidity. This is because the polycarsylate ether copolymer compound in the concrete admixture included in the medium-flow concrete composition according to the present invention can induce particle dispersion and provide excellent resistance to material separation.

[0131] division rheology evaluation Flow (mm) Air( % ) Concrete compressive strength ( MPa ) silence yield stress (Pa) viscosity (Pa*s) 1 day 7 days 28th Comparative Example 1 2447 89 455 5.4 4.8 21.0 28.5 Example 1 1672 41 450 5.5 4.6 20.7 28.6

[0132] In addition, referring to Table 2 above, it can be seen that while the concrete compressive strengths of Comparative Example 1 and Example 1 showed similar results, there were significant differences in static yield stress and viscosity. This indicates that the concrete admixture included in the medium-flow concrete composition according to the present invention can provide excellent effects by controlling viscosity and imparting fluidity to the concrete without impairing the compressive strength of the concrete.

[0134] Although the present invention has been described in detail above with reference to preferred embodiments, the scope of the technical concept of the present invention is not limited by such embodiments. Accordingly, various modifications or equivalent embodiments may exist within the scope of the technical concept of the present invention. Therefore, the scope of rights of the technical concept according to the present invention should be interpreted by the claims, and technical concepts within an equivalent or equivalent scope should be interpreted as falling within the scope of rights of the present invention.

Claims

Claim 1 A medium-flow concrete composition comprising a concrete admixture, aggregate, binder, and water, wherein the concrete admixture comprises a polycarboxylate ether-based copolymer compound and a polycarboxylic acid-based water reducer, and the polycarboxylate ether-based copolymer compound comprises an aromatic macromonomer, an unsaturated carboxylic acid, a chain transfer agent, a solvent, and a polymerization initiator, wherein, based on the total weight of the medium-flow concrete composition, the concrete admixture comprises 5 to 10 parts by weight, the aggregate comprises 40 to 80 parts by weight, the binder comprises 1 to 50 parts by weight, and the water comprises 5 to 20 parts by weight, wherein the viscosity of the medium-flow concrete composition is 35 to 80 Pa*s, and the static yield stress of the medium-flow concrete composition is 1,000 to 2,000 Pa. Claim 2 A medium-flow concrete composition according to claim 1, characterized in that the polycarboxylate ether-based copolymer compound comprises 0.01 to 5 parts by weight of the chain transfer agent, 70 to 2,000 parts by weight of the solvent, and 0.01 to 10 parts by weight of the polymerization initiator, based on 100 parts by weight of the aromatic macro monomer. Claim 3 A medium-flow concrete composition according to claim 1, characterized in that the unsaturated carboxylic acid comprises one or more selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and mesaconic acid. Claim 4 A medium-flow concrete composition according to claim 1, characterized in that the weight mixing ratio of the aromatic macromonomer and the unsaturated carboxylic acid is greater than 1:0 and less than or equal to 1,050. Claim 5 A medium-flow concrete composition according to claim 1, characterized in that the polycarboxylate ether-based copolymer compound and the polycarboxylic acid-based water reducer are mixed in a weight ratio of 1:1 to 1:

20. Claim 6 A medium-flow concrete composition according to claim 1, wherein the polymerization initiator comprises one or more selected from the group consisting of t-amyl peroxy-2-ethylhexanoate, 2,2'-azobis-isobutyronitrile (AIBN), benzoyl peroxide, lauroyl peroxide, 2,2'-azobis-(2,4-dimethylvaleronitrile), 2,2'-azobis-(4-methoxy-2,4-dimethylvaleronitrile), t-butylperoxypivalate, 1,1'-bis-(bis-t-butylperoxy)cyclohexane, and combinations thereof. Claim 7 delete Claim 8 A medium-flow concrete composition according to claim 1, wherein the binder comprises one or more selected from the group consisting of ordinary Portland cement, rapid-strength Portland cement, lime cement, slag cement, blast furnace slag cement, Portland pozzolan cement, fly ash, bottom ash, gypsum cement, lime cement, silica fume, and low-heat cement. Claim 9 A medium-fluid concrete composition according to claim 1, wherein the aggregate comprises one or more selected from the group consisting of: fine aggregate composed of crushed sand, washed sand, and recycled aggregate with a particle size of 0.01 to 5 mm; and coarse aggregate composed of crushed stone, crushed slag, natural gravel, crushed gravel, and recycled aggregate with a particle size of 5 to 25 mm. Claim 10 delete Claim 11 delete

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