Medium-flow concrete composition with improved early strength performance

Abstract

The present invention relates to a medium-flow concrete composition, which can provide excellent resistance to material separation and viscosity control by including a concrete admixture containing an aromatic macromonomer, and can provide excellent early strength development by including calcium silicate nanoparticles.

Description

Technology Field

[0001] The present invention relates to a medium-flow concrete composition with improved workability and resistance to material segregation through the control and suppression of viscosity of medium-flow concrete. Specifically, the invention relates to a medium-flow concrete composition characterized by comprising a binder containing cement, aggregate, water, a concrete admixture containing an aromatic macromonomer, and calcium silicate hydrate, which exhibits excellent workability and resistance to material segregation and improved early strength performance. 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 is devised to solve the problems of the aforementioned prior art and aims to provide a medium-flow concrete composition that includes a concrete admixture containing a polycarboxylate ether-based copolymer compound and includes calcium silicate hydrate, which has excellent workability and resistance to material separation, as well as excellent early strength performance. means of solving the problem

[0010] To achieve the above objective, the present invention comprises calcium silicate nanoparticles, a concrete admixture, aggregate, a binder, and water, wherein the concrete admixture comprises a polycarboxylate ether-based copolymer compound and a polycarboxylic acid-based water reducer.

[0011] The above polycarboxylate ether copolymer compound provides a medium-flow concrete composition comprising an aromatic macromonomer, an unsaturated carboxylic acid, a chain transfer agent, a solvent, and a polymerization initiator.

[0012] In a medium-flow concrete composition according to one embodiment of the present invention, the calcium silicate nanoparticles are prepared by reacting a water-soluble calcium compound and a water-soluble silicate compound, and

[0013] The above calcium silicate nanoparticles are characterized by having a molar ratio of calcium to silicon (Ca / Si) of 2 to 10.

[0014] The above water-soluble calcium compounds include calcium nitrate, calcium chloride, calcium formate, calcium acetate, calcium bicarbonate, calcium bromide, calcium carbonate, calcium citrate, calcium chlorate, calcium fluoride, calcium gluconate, calcium hydroxide, calcium oxide, calcium hypochlorite, calcium iodide, calcium lactate, calcium nitrite, calcium oxalate, calcium phosphate, and calcium It is characterized by comprising one or more selected from the group consisting of calcium propionate, calcium silicate, calcium stearate, calcium sulfate, calcium sulfate hemihydrate, calcium sulfate dihydrate, calcium sulfide, calcium tartrate, calcium aluminate, tricalcium silicate, dicalcium silicate, and hydrates thereof.

[0015] The above water-soluble silicate compound is characterized by being one or more of the group consisting of sodium silicate, potassium silicate, water glass, aluminum silicate, tricalcium silicate, dicalcium silicate, calcium silicate, silicic acid, sodium metasilicate, potassium metasilicate, and hydrates thereof.

[0016] The above polycarboxylate ether-based copolymer compound is

[0017] It is characterized by having 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, relative to 100 parts by weight of the aromatic macromonomer.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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. Effects of the invention

[0023] 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.

[0024] In addition, by including calcium silicate nanoparticles, it can improve water-reducing performance and promote early strength development of medium-flow concrete compositions, thereby providing excellent productivity and economic effects.

[0025] 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.

[0026] 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.

[0027] 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. Brief explanation of the drawing

[0029] Figure 1 is a graph showing the heat of hydration measured in 5°C sealed curing according to one comparative example and an embodiment of the present invention. FIG. 2 is a graph showing the heat of hydration measured in 10°C sealed curing according to one comparative example and an embodiment of the present invention. 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 calcium silicate nanoparticles, a concrete admixture, aggregate, a binder, and water.

[0033] Sealed curing reproduces the hydration temperature of concrete in winter and may involve curing a medium-flow concrete composition inside a Styrofoam ice box. At this time, the temperature inside the ice box for the sealed curing may be 5°C to 20°C, and according to one embodiment of the present invention, the temperature may be 5°C to 10°C. When the medium-flow concrete composition is sealed and cured in the manner described above, calcium silicate nanoparticles can further improve the water sensitivity performance of the concrete admixture and provide excellent rough strength development.

[0034] In a medium-flow concrete composition according to one embodiment of the present invention, the calcium silicate nanoparticles are prepared by reacting a water-soluble calcium compound and a water-soluble silicate compound, and

[0035] The above calcium silicate nanoparticles are characterized by having a molar ratio of calcium to silicon (Ca / Si) of 2 to 10.

[0036] Typically, the hydration process of cement involves cement compounds reacting with water to produce hydrates, which then lose their fluidity and set, and as time passes, further hydration reactions proceed to harden, thereby increasing the strength of the structure; thus, hydration and hardening (strength) are closely related. These hydrates consist of tricalcium silicate (3CaOSiO2), referred to as alite (C3S), and dicalcium silicate (2CaOSiO2), commonly referred to as belite (C2S). Among these, C3S accounts for the largest proportion of cement compounds, and when it reacts with water, it immediately produces calcium hydroxide [Ca(OH)2] and calcium silicate hydrate (CSH, Calcium Silicate Hydrate, hereinafter abbreviated as "CSH"). At this time, it is known that the initial rate of CSH, the final hydration product of cementitious compounds, has a significant impact on whether the concrete can secure early strength, and this rate is known as the rate-determining stage of the hydration process, which usually takes at least 6 hours and up to 10 hours.

[0037] When calcium silicate nanoparticles according to the present invention are mixed with a concrete mixture, the nanoparticles containing CSH act as nucleation seeds. As they grow larger, they fill the voids between cement particles, thereby eliminating the initial hydration process of cement, which was the conventional rate-determining stage. Consequently, the curing time of the concrete can be drastically reduced. Through the addition of this, early strength that could not be achieved in conventional concrete can be realized. Furthermore, by developing application technologies, the construction period at construction sites can be shortened to two-thirds of the conventional period, thereby increasing process efficiency and drastically reducing energy consumption. Additionally, there is an effect of reducing construction costs and labor costs.

[0038] The molar ratio of calcium to silicon (Ca / Si) of the calcium silicate hydrate may be 2 to 10. That is, the molar ratio of silicon (Si) to calcium (Ca) may be 1:2 to 10. If the molar ratio of calcium to silicon (Ca / Si) of the calcium silicate hydrate falls outside the above range, that is, if the molar ratio of calcium to silicon (Ca / Si) is less than 2 or exceeds 10, the effect of early strength enhancement may be insufficient, and as a result, the compressive strength is significantly lower compared to when it is within the above range, which is undesirable.

[0039] The size of the calcium silicate nanoparticles may be 10 to 1,000 nm.

[0040] The above calcium silicate nanoparticles are prepared by reacting a water-soluble calcium compound and a water-soluble silicate compound. Specifically, the preparation can include the step of preparing a mixture by mixing a water-soluble calcium compound and a water-soluble silicate compound, and preparing nanoparticles by stirring the mixture.

[0041] The above mixture may further include a polymer dispersant, and the polymer dispersant may include a polycarboxylate-based compound.

[0042] The above-mentioned dispersant may inhibit the aggregation of particles such as water-soluble calcium compounds, water-soluble silicate compounds, and alkali metal hydroxides used in the method for manufacturing nanoparticles of the present invention, and may cause the particles to be separated from each other using electrostatic or physical repulsive forces. Through this, uniform strength is achieved across the entire area of ​​the cement concrete, and sufficient workability can be secured while reducing the amount of water mixed.

[0043] The above water-soluble calcium compounds include calcium nitrate, calcium chloride, calcium formate, calcium acetate, calcium bicarbonate, calcium bromide, calcium carbonate, calcium citrate, calcium chlorate, calcium fluoride, calcium gluconate, calcium hydroxide, calcium oxide, calcium hypochlorite, calcium iodide, calcium lactate, calcium nitrite, calcium oxalate, calcium phosphate, and calcium It is characterized by comprising one or more selected from the group consisting of calcium propionate, calcium silicate, calcium stearate, calcium sulfate, calcium sulfate hemihydrate, calcium sulfate dihydrate, calcium sulfide, calcium tartrate, calcium aluminate, tricalcium silicate, dicalcium silicate, and hydrates thereof.

[0044] The above water-soluble silicate compound is characterized by being one or more of the group consisting of sodium silicate, potassium silicate, water glass, aluminum silicate, tricalcium silicate, dicalcium silicate, calcium silicate, silicic acid, sodium metasilicate, potassium metasilicate, and hydrates thereof.

[0045] Preferably, the water-soluble calcium compound is calcium nitrate hydrate and calcium nitrate tetrahydrate (Ca(NO3)2 · 4H2O), and the water-soluble silicate compound may include sodium metasilicate hydrate, preferably sodium metasilicate pentahydrate (Na2SiO3·5H2O).

[0046] The above concrete admixture includes a polycarboxylate ether-based copolymer compound and a polycarboxylic acid-based water reducer.

[0047] 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.

[0048] The above aromatic macromonomer is represented by the following chemical formula 1.

[0049] [Chemical Formula 1]

[0050]

[0051] (In the above chemical formula 1,

[0052] R1 to R3 are each independently hydrogen or C1-C 20 It is an alkyl group, and

[0053] R4 is hydrogen, C1-C 20 It is an alkyl group or a phenyl group, and

[0054] n is an integer selected from 1 to 200, and

[0055] m is an integer selected from 0 to 100, and

[0056] p can be an integer selected from 0 to 1.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] [Chemical Formula 1-1]

[0061]

[0062] 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.

[0063] 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 may comprise both methacrylic acid and acrylic acid.

[0064] 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.

[0065] 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.

[0066] 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 Chemical 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 arise in that 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] The above-described medium-flow concrete composition is characterized by comprising, with respect to the total weight of the above-described medium-flow concrete composition, 1 to 10 parts by weight of the calcium silicate nanoparticles, 1 to 10 parts by weight of the above-described concrete admixture, 40 to 80 parts by weight of the above-described aggregate, 1 to 50 parts by weight of the above-described binder, and 5 to 20 parts by weight of the above-described water.

[0074] 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.

[0075] 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

[0076] 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.

[0077] The above fine aggregate refers to aggregate with a particle size that passes 100% through a standard 5mm mesh sieve, and the above fine aggregate may preferably be crushed sand, but is not limited thereto.

[0078] 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.

[0079] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0087] 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.

[0088] The content of the above concrete admixture may include 1 to 10 parts by weight of the above concrete admixture with respect to the total weight of the above medium-flow concrete composition, and preferably 1 to 2 parts by weight.

[0090] The medium-flow concrete composition according to the present invention includes calcium silicate nanoparticles, thereby providing the effect of having excellent early strength development performance of the concrete composition.

[0091] The content of the calcium silicate nanoparticles may include 1 to 10 parts by weight of the concrete admixture with respect to the total weight of the medium-flow concrete composition, and preferably 1 to 2 parts by weight.

[0093] The above calcium silicate nanoparticles and the above concrete admixture are characterized by having a weight ratio of 1:0.1 to 5, and when within this range, the general compressive strength of the concrete composition can be maintained while having excellent viscosity control and resistance to work separation.

[0095] The medium-flow concrete composition according to the present invention is characterized by having a viscosity of 35 to 80 Pa*s.

[0096] The above-mentioned medium-flow concrete composition is characterized by having a static yield stress of 1,000 to 2,000 Pa.

[0097] 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.

[0098] 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.

[0100] Preparation Example 1 manufacturing

[0101] 1. Preparation of calcium silicate nanoparticles.

[0102] 101.9 g of calcium nitrate tetrahydrate ((CaNO3)2·4H2O, Mw: 236 g / mol) and 43.7 g of distilled water were weighed into a 500 ml beaker and stirred for 30 minutes using a magnetic stirrer to completely dissolve them, thereby preparing the first solution. 45.7 g of sodium metasilicate pentahydrate (Na2SiO3·5H2O, Mw: 212 g / mol) and 473.7 g of distilled water were weighed into a 1,000 ml beaker and stirred for 30 minutes using a magnetic stirrer to prepare the second solution. 100g of a polycarboxylate-based dispersant manufactured by Silk Road C&T and 235g of distilled water were weighed and placed into a 4-neck flask reactor. Then, the first solution and the second solution were simultaneously introduced into the reactor containing the dispersant and distilled water, and the mixture was stirred using a mechanical stirrer at 500 rpm for 120 minutes to produce nanoparticles. At this time, the molar ratio (Ca / Si) of the Ca component of the first solution and the Si component of the second solution was 2.0.

[0104] 2. Manufacture of concrete admixtures

[0105] A mixture was prepared comprising 23 parts by weight of a PPEG-MAA compound prepared including a phenol polyethylene glycol ether compound, 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). 30 parts by weight of the polycarboxylic acid ether copolymer compound were added to a polycarboxylic acid-based water reducer solution, and caustic soda was added to adjust the pH to 6.0 to prepare a concrete admixture.

[0106] .

[0107] Examples 1. Junjogang Cement-based Jungyudong Preparation of concrete composition.

[0108] A medium-flow concrete composition was prepared with the calcium silicate nanoparticles of Preparation Example 1 and a concrete admixture according to the composition shown in Table 1 below.

[0109] [Table 1]

[0110]

[0111] Afterwards, the medium-flow concrete composition prepared as described above was placed in a Styrofoam ice box and sealed cured, and the sealed curing was performed at a temperature of 5℃.

[0113] Examples 2. Ordinary Portland cement based Jungyudong Preparation of concrete composition.

[0114] A medium-flow concrete composition comprising the calcium silicate nanoparticles and a concrete admixture was prepared with the composition shown in Table 1 below.

[0115] [Table 2]

[0116]

[0117] Afterwards, the medium-flow concrete composition prepared as described above was placed in a Styrofoam ice box and sealed cured, and the sealed curing was performed at a temperature of 10℃.

[0119] Comparative example 1. Junjogang Cement-based Jungyudong Preparation of concrete composition.

[0120] For comparison with Example 1, Comparative Example 1 was prepared by forming a medium-flow concrete composition containing calcium silicate nanoparticles and a general high-performance AE water reducer without adding a concrete admixture, and performing sealed curing at 5°C.

[0122] Comparative example 2. Ordinary Portland cement based Jungyudong Preparation of concrete composition.

[0123] For comparison with Example 2, Comparative Example 2 was prepared by forming a medium-flow concrete composition containing calcium silicate nanoparticles and a general high-performance AE water reducer without adding a concrete admixture, and performing sealed curing at 10°C.

[0125] Experimental Example 1: Comparison of Concrete Flow Properties

[0126] To evaluate the fluidity and physical properties of the medium-flow concrete compositions prepared according to the examples and comparative examples, static yield stress, viscosity, flow, and compressive strength over time were measured and are shown in Tables 3 and 4 below.

[0127] [Table 3]

[0128]

[0129] [Table 4]

[0130]

[0131] Referring to Tables 3 and 4 above, regarding static yield stress, when comparing Examples 1 and 2 using the concrete admixture according to the present invention with Comparative Examples 1 and 2 using a general water-reducing agent, it was found that the static yield stress was measured to be lower in the medium-flow concrete compositions of Examples 1 and 2, indicating significantly superior viscosity control. In addition, regardless of the type of cement, the viscosity measurement results were also measured to be lower in Examples 1 and 2, indicating that the medium-flow concrete composition according to the present invention 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.

[0132] In addition, referring to Figures 1 and 2, it was confirmed that the early strength development was excellent even when sealing curing was performed under the same conditions, along with the effects of viscosity control and resistance to material separation.

[0133] Although the present invention has been described in detail above with reference to the drawings and preferred embodiments, the scope of the technical concept of the present invention is not limited by these drawings and 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 calcium silicate nanoparticles, a concrete admixture, aggregate, a 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 the calcium silicate nanoparticles are prepared by reacting a water-soluble calcium compound and a water-soluble silicate compound, and the molar ratio of calcium to silicon (Ca / Si) of the calcium silicate nanoparticles is 2 to 10, and 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, and, with respect to the total weight of the medium-flow concrete composition, the calcium silicate nanoparticles are 1 to 10 parts by weight, and the concrete admixture is 1 to 10 A medium-flow concrete composition characterized by comprising, in parts by weight, 40 to 80 parts by weight of aggregate, 1 to 50 parts by weight of binder, and 5 to 20 parts by weight of water, wherein the weight ratio of calcium silicate nanoparticles to concrete admixture is 1:0.1 to 5 parts by weight, 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 delete Claim 3 In claim 1, the water-soluble calcium compound is calcium nitrate, calcium chloride, calcium formate, calcium acetate, calcium bicarbonate, calcium bromide, calcium carbonate, calcium citrate, calcium chlorate, calcium fluoride, calcium gluconate, calcium hydroxide, calcium oxide, calcium hypochlorite, calcium iodide, calcium lactate, calcium nitrite, calcium oxalate, calcium phosphate, calcium A medium-flow concrete composition comprising one or more selected from the group consisting of calcium propionate, calcium silicate, calcium stearate, calcium sulfate, calcium sulfate hemihydrate, calcium sulfate dihydrate, calcium sulfide, calcium tartrate, calcium aluminate, tricalcium silicate, dicalcium silicate, and their hydrates. Claim 4 A medium-flow concrete composition according to claim 1, wherein the water-soluble silicate compound comprises one or more selected from the group consisting of sodium silicate, potassium silicate, water glass, aluminum silicate, tricalcium silicate, dicalcium silicate, calcium silicate, silicic acid, sodium metasilicate, potassium metasilicate, and hydrates thereof. Claim 5 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 6 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 7 delete Claim 8 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 9 delete

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