Concrete admixture composition capable of being poured in a rainy environment and concrete composition comprising the same

Abstract

The present invention relates to a concrete admixture composition capable of minimizing strength reduction even in rainy environments, and a concrete composition comprising the same. The present admixture comprises an associative thickener and may optionally include a methylcellulose-based thickener, a water-reducing agent, and core-shell nanoparticles. Concrete to which the admixture of the present invention is applied exhibits a low rate of compressive strength reduction even during rain, excellent resistance to material segregation, and good workability, thereby enabling stable quality even in rainy environments.

Description

Technology Field

[0001] The present invention relates to a concrete admixture composition and a concrete composition containing the same, and more specifically, to a concrete admixture composition capable of being poured even in a rainy environment and a concrete composition containing the same. Background Technology

[0003] Concrete is a widely used material for constructing foundations and key structural members, and it achieves its designed strength and durability through a hardening process after casting. However, when concrete is cast at a construction site in adverse weather conditions, such as rain, particularly during rainfall, rainwater is mixed into the concrete before the cement hydrates, causing the water-to-cement ratio (W / C ratio) to rise. This increase in the water-to-cement ratio leads to a decrease in the compressive strength of the concrete after hardening and can cause various problems, including reduced long-term durability, material segregation, increased bleeding, and the formation of air bubbles.

[0004] In particular, when pouring concrete in rainy environments, the use of general concrete compositions with low resistance to material segregation makes it prone to aggregate segregation and cement paste loss within the formwork, accompanied by increased water incorporation due to rainwater. This can directly lead to a deterioration in the quality of the final structure. Since these issues can ultimately result in safety accidents such as shortened structural lifespan, cracking, or even collapse, technical countermeasures to prevent them are urgently needed.

[0005] For this reason, the domestic concrete specifications revised in 2024 (KCS 14 20 10 : 2024) stipulate that concrete pouring is prohibited in principle when rain or snowfall is expected to have a detrimental effect on concrete quality. However, pouring may proceed with the approval of the responsible engineer if sufficient measures are taken to prevent rainwater inflow or if the quality degradation caused by rainfall is judged to be minimal. Furthermore, through the "Research on the Development of Standards for Concrete Pouring During Rainfall (April 2024 – November 2024)," the Ministry of Land, Infrastructure and Transport presented standards for concrete that can be constructed even in rainy environments and strengthened work standards. For example, specific work standards have been established, such as allowing concrete pouring only when the rainfall is 3 mm / hr or less.

[0006] However, in actual construction sites, it is difficult to completely avoid pouring concrete during rain due to the climate characteristics of Korea, which has a high number of rainy days per year. For example, considering that the annual average number of rainy days in Seoul has exceeded 100 over the past 10 years, completely banning pouring during rain would inevitably result in a significant economic burden due to project delays and increased construction costs. Unreasonable shortening of the construction schedule to avoid these problems carries the risk of leading to substandard construction, quality degradation, and safety accidents.

[0007] Against this backdrop, there is a very high technical demand for the development of concrete compositions that can secure a certain level of compressive strength and resistance to material segregation even in rainy environments, while minimizing quality degradation issues caused by an increase in the water-cement ratio. In particular, conventional technology using general methylcellulose-based thickeners is vulnerable to rainwater ingress in rainy environments, which has limitations in forming uniform viscosity and securing resistance to material segregation. Accordingly, there is a demand for the development of a concrete admixture composition capable of being poured in rainy environments and a concrete composition containing the same, which can solve these problems. The problem to be solved

[0009] The objective of the present invention is to provide a concrete composition that can be poured without performance degradation even in rainy environments. More specifically, the objective is to provide a concrete admixture composition that effectively suppresses problems such as an increase in the water-cement ratio, material segregation, and a decrease in compressive strength, which commonly occur in concrete poured during rainfall, and to ensure compressive strength and durability above a certain level.

[0010] In addition, the present invention has another objective of providing a concrete composition for rain that enables uniform dispersion of the material and maintenance of viscosity despite the inflow of rainwater due to rainfall, and exhibits improved performance compared to a composition using a conventional methylcellulose-based thickener in both initial and long-term strength characteristics.

[0011] In addition, one of the important tasks of the present invention is to provide a concrete composition capable of ensuring stable constructability and quality even in rainy environments by introducing functional nanoparticles (core-shell structures) that can improve the problem of strength reduction caused by rainwater inflow and promote bonding strength and hydration reactions between cement particles. means of solving the problem

[0013] In order to achieve the above objective, according to one embodiment of the present invention, a concrete admixture comprising an associative thickener and a water-reducing agent is provided.

[0014] The above-mentioned water reducer may be at least one of a polycarboxylic acid-based water reducer, a naphthalene-based water reducer, a melamine-based water reducer, and a lignin-based water reducer.

[0015] The above concrete admixture composition may further include core-shell nanoparticles.

[0016] The above core may include a metal oxide.

[0017] The above shell may contain calcium.

[0018] The above concrete admixture composition may further include a methylcellulose-based thickener.

[0019] The above methylcellulose thickener may include at least one of methylcellulose, hydroxypropyl methylcellulose, hydroxyethyl methylcellulose, and hydroxybutyl methylcellulose.

[0020] For every 100 parts by weight of the total concrete admixture composition, the associative thickener may be 1 to 50 parts by weight.

[0021] With respect to 100 parts by weight of the total concrete admixture composition, the water reducing agent may be in an amount of 20 to 99 parts by weight.

[0022] With respect to 100 parts by weight of the total concrete admixture composition, the core-shell nanoparticles may be in an amount of 20 to 70 parts by weight.

[0023] According to one embodiment of the present invention, a concrete composition comprising the aforementioned concrete admixture composition is provided. Effects of the invention

[0025] The concrete composition according to the present invention includes an admixture designed to enable casting in a rainy environment, thereby reducing the rate of strength reduction and improving resistance to material segregation compared to concrete using conventional methylcellulose-based thickeners. Accordingly, concrete can be cast without quality degradation even in environments with rainfall of 3 mm / hr or more, thereby preventing construction delays and ensuring flexibility in construction.

[0026] In particular, the associative thickener used in the present invention adsorbs and evenly disperses cement particles through association that forms a network structure within concrete, thereby maintaining uniform viscosity and increasing resistance to material separation. This enables the securing of much more stable rheological properties in rainy environments compared to methylcellulose-based thickeners that rely on physical entanglement.

[0027] Furthermore, the concrete composition according to the present invention includes core-shell structured nanoparticles, thereby promoting the hydration reaction and effectively filling the voids between cement particles, which can simultaneously improve early strength and long-term durability. As a result, the stability and durability of the structure can be ensured even during rainfall, making it possible to construct high-quality concrete structures.

[0028] In addition, the present invention can achieve a balance of economic efficiency and quality by appropriately combining an associative thickener and a methylcellulose-based thickener, and provides excellent constructability and performance across quality indicators such as strength performance, resistance to material separation, air content, and slump.

[0029] Therefore, the present invention provides a useful technical means to fundamentally solve the problems of construction delays and quality degradation caused by weather conditions by providing a concrete construction technology capable of ensuring consistent performance even in rainy environments. Specific details for implementing the invention

[0031] The present disclosure is described in detail below.

[0032] Expressions such as "comprising" as used in this specification should be understood as open-ended terms implying the possibility of including other technical features.

[0033] As used herein, "as an example," "as an embodiment," and "preferably" refer to embodiments of the present invention that may provide certain advantages under certain conditions, and are not intended to exclude other embodiments from the scope of the present invention.

[0034] The term "average particle size (D50)" used in this application may refer to an intermediate particle size corresponding to 50% in a cumulative distribution (number-based distribution) in which the corresponding particles are arranged in order of size.

[0035] The present invention provides a concrete admixture composition.

[0036] In one embodiment of the present invention, the concrete admixture composition may include an associative thickener and a water-reducing agent.

[0037] The above-mentioned associative thickener is an amphiphilic polymer having both hydrophobic and hydrophilic groups, and forms a network structure through the interaction between hydrophobic groups in an aqueous solution. By effectively capturing cement particles or other solid components within the concrete, it can control viscosity and improve resistance to material separation.

[0038] The above urethane-based associative thickener may be, for example, hydrophobically modified ethoxylated polyurethane, poly(ethylene oxide)-poly(propylene oxide) block copolymer-based polyurethane, or poly(ethylene glycol)-urethane copolymer, but is not limited thereto.

[0039] The above acrylic associative thickener may be, for example, an alkyl acrylate-acrylic acid copolymer, an alkyl acrylate-acrylamide copolymer, or an alkyl acrylate-methacrylic acid copolymer, but is not limited thereto.

[0040] The above-mentioned cellulose-based associative thickener may be, for example, hydroxyethyl cellulose, a derivative of hydroxyethyl cellulose in which a hydrophobic substituent is introduced (hydrophobically modified hydroxyethyl cellulose), or methyl hydroxyethyl cellulose, but is not limited thereto.

[0041] The above-mentioned associative thickener may be present in an amount of 1 part by weight or more, 2 parts by weight or more, 3 parts by weight or more, 4 parts by weight or more, 5 parts by weight or more, 6 parts by weight or more, 7 parts by weight or more, 8 parts by weight or more, 9 parts by weight or more, or 10 parts by weight or more, and may be 50 parts by weight or less, 45 parts by weight or less, 40 parts by weight or less, 35 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less, or 20 parts by weight or less, based on 100 parts by weight of the total concrete admixture composition. When the above weight range is satisfied, appropriate viscosity control and resistance to material separation are imparted within the concrete mixture, while simultaneously maintaining the flowability and workability of the admixture composition, thereby enabling the casting of concrete of stable quality even in rainy environments. Furthermore, the required fluidity and strength characteristics can be effectively secured while preventing a decrease in workability or an increase in costs caused by the excessive addition of thickener.

[0042] The above-mentioned water-reducing agent prevents aggregation between cement particles and improves dispersibility, thereby improving the fluidity and workability of concrete and enhancing strength and durability by reducing water usage. In addition, the above-mentioned water-reducing agent is adsorbed onto the surface of cement particles through negatively charged functional groups and induces electrostatic repulsion or a stearic hindrance effect between particles, enabling uniform dispersion of cement particles.

[0043] The above-mentioned water reducer may be, for example, at least one of a polycarboxylic acid-based water reducer, a naphthalene-based water reducer, a melamine-based water reducer, and a lignin-based water reducer.

[0044] The above-mentioned polycarboxylic acid-based water reducer may be, for example, a poly(acrylic acid-maleic acid) copolymer, a poly(acrylic acid-ethylene oxide) copolymer, or a poly(methacrylic acid-alkyl ester) copolymer, but is not limited thereto.

[0045] The above-mentioned naphthalene-based water reducer may be, for example, a naphthalene sulfonate-formaldehyde condensate, a sodium naphthalene sulfonate, or poly(naphthalene sulfonate) derivatives, but is not limited thereto.

[0046] The above melamine-based water reducer may be, for example, a melamine sulfonate-formaldehyde condensate, sodium melamine sulfonate, or poly(melamine sulfonate) derivatives, but is not limited thereto.

[0047] The above-mentioned lignin-based water reducer may be, for example, calcium lignosulfonate, sodium lignosulfonate, or magnesium lignosulfonate, but is not limited thereto.

[0048] The above-mentioned water reducer may be 20 parts by weight or more, 25 parts by weight or more, 30 parts by weight or more, or 35 parts by weight or more, and 99 parts by weight or less, 95 parts by weight or less, 90 parts by weight or less, 85 parts by weight or less, or 80 parts by weight or less, based on 100 parts by weight of the total concrete admixture composition.

[0049] When the above weight range is satisfied, the fluidity of the concrete mixture can be effectively secured, and it can contribute to improved strength and durability by minimizing slump loss and reducing the water-to-cement ratio. In addition, it enhances the dispersion stability of cement particles to increase the uniformity of material mixing, and ensures excellent workability and quality even in rainy environments.

[0050] In one embodiment of the present invention, the concrete admixture composition may further include core-shell nanoparticles.

[0051] The above core-shell nanoparticles consist of a core and a shell, the core may contain a metal oxide, and the shell may contain an inorganic compound containing calcium.

[0052] The above core acts as a nucleation seed during the cement hydration reaction, and the shell has a chemical composition similar to the hydration product, thereby effectively filling the voids between cement particles and promoting the hydration reaction.

[0053] The above core may be, for example, one or more of silica, titanium dioxide, cerium oxide, zinc oxide, aluminum oxide, zirconium oxide, manganese oxide, iron oxide, vanadium oxide, tin oxide, and tungsten oxide, but is not limited thereto.

[0054] The shell may be, for example, one or more of calcium silicate, calcium titanate, calcium cerate, calcium zincate, calcium aluminate, calcium zirconate, calcium permanganate, calcium ferrite, calcium vanadate, calcium stanate, and calcium tungstate, but is not limited thereto.

[0055] The average particle size of the core-shell nanoparticles may be, for example, 10 nm or more, 20 nm or more, 30 nm or more, or 50 nm or more, and 500 nm or less, 300 nm or less, 200 nm or less, or 100 nm or less. When the average particle size of the core-shell nanoparticles is within the above range, they can effectively act as a nucleating agent in the cement hydration reaction and effectively fill the voids between cement particles to contribute to the formation of a dense microstructure. In addition, it can prevent a decrease in dispersibility or aggregation caused by an excessive increase in particle size.

[0056] The average particle size of the core may be, for example, 5 nm or more, 10 nm or more, or 20 nm or more, and 300 nm or less, 200 nm or less, or 100 nm or less. When the average particle size of the core is within the above range, the core can perform the role of a stable nucleation seed during the hydration reaction and maintain a strong bonding force at the interface with the shell, which is effective in improving durability. In addition, since a uniform coating is possible during shell formation, dispersion stability within the concrete mixture can be secured.

[0057] The average thickness of the shell may be, for example, 1 nm or more, 2 nm or more, 3 nm or more, 5 nm or more, or 10 nm or more, and 100 nm or less, 70 nm or less, 50 nm or less, or 30 nm or less.

[0058] When the average thickness of the shell is within the above range, the shell can stably surround the core while maintaining reactivity with the cement hydration product, allowing the core-shell nanoparticles to effectively act as nucleation seeds for the hydration reaction. In addition, as the shell is composed of an inorganic compound similar to the hydration product, interfacial bonding strength and dispersion stability within the concrete are improved, thereby contributing to the enhancement of early and long-term compressive strength.

[0059] The above core-shell nanoparticles may be 20 parts by weight or more, 25 parts by weight or more, 30 parts by weight or more, 35 parts by weight or more, or 40 parts by weight or more, and 70 parts by weight or less, 60 parts by weight or less, or 50 parts by weight or less, based on 100 parts by weight of the total concrete admixture composition.

[0060] When satisfying the above weight range, it can act as a reaction accelerator in the initial stage of the cement hydration reaction to improve initial strength, and can enhance long-term strength and durability by acting as a fine filler to fill the voids between cement particles. In addition, the inorganic compounds contained in the shell improve the mutual bonding strength within the concrete due to their chemical affinity with the hydration products, and can provide excellent structural stability and strength retention effects even in rainy environments.

[0061] In one embodiment of the present invention, the concrete admixture composition may further include a methylcellulose-based thickener.

[0062] The above methylcellulose-based thickener may be a water-soluble polymer compound having a structure in which a methyl group (-OCH3) is substituted for a hydroxyl group (-OH) of cellulose, as one of the cellulose derivatives. Such a polymer imparts viscosity through hydrogen bonding and physical entanglement between polymer chains in an aqueous solution, and improves the resistance to material separation of the concrete mixture.

[0063] The above methylcellulose-based thickener may be, for example, one or more of methylcellulose (-OCH, Methyl cellulose), hydroxypropyl methylcellulose (-OCH3-CH₂CH(OH)CH₃, Hydroxypropyl methyl cellulose, HPMC), hydroxyethyl methylcellulose (-OCH3-CH₂CH₂OH, Hydroxyethyl methyl cellulose, HEMC), and hydroxybutyl methylcellulose (-OCH3-CH₂CH(CH₃)CH₂OH, Hydroxybutyl methyl cellulose, HBMC), but is not limited thereto.

[0064] The above methylcellulose thickener may be 1 part by weight or more, 2 parts by weight or more, 5 parts by weight or more, or 10 parts by weight or more, and 40 parts by weight or less, 30 parts by weight or less, or 20 parts by weight or less, based on 100 parts by weight of the total concrete admixture composition.

[0065] When the above weight range is satisfied, it can provide an effect of forming initial viscosity of the concrete mixture and preventing material separation, and is particularly advantageous for preventing bleeding and controlling slump loss in high-strength concrete or fluid concrete. However, since methylcellulose-based thickeners may cause viscosity variations when rainwater is mixed in due to the viscosity-improving characteristics caused by physical entanglement, in one embodiment of the present invention, they may be used in combination with an associative thickener to maintain stable viscosity and improve construction quality.

[0066] In one embodiment of the present invention, the concrete admixture composition may further include an air-entraining agent (AE agent).

[0067] The above air-entraining agent disperses air introduced from the outside into fine, uniform bubbles during concrete mixing, thereby stably trapping it within the concrete, which can provide effects such as improved workability, prevention of bleeding, reduction of material segregation, reduction of drying shrinkage and cracking, and improved freeze-thaw resistance.

[0068] The above air-entraining agent may be one or more of, for example, alkylbenzene sulfonate, lauryl sulfate salt, naphthalene-based or lignin-based surfactants, and polyether-type nonionic surfactants, but is not limited thereto.

[0069] The above air-entraining agent may be 0.001 parts by weight or more, 0.005 parts by weight or more, or 0.01 parts by weight or more, and 5 parts by weight or less, 1 part by weight or less, or 0.1 parts by weight or less, based on 100 parts by weight of the total concrete admixture composition. When the above weight range is satisfied, the amount of air in the concrete can be effectively controlled, thereby maintaining fluidity without slump loss even in situations where construction conditions are unfavorable, such as rainy environments, and ensuring the long-term durability and quality stability of the concrete.

[0070] The present invention provides a concrete composition.

[0071] In one embodiment of the present invention, the concrete composition may include the aforementioned concrete admixture composition.

[0072] In one embodiment of the present invention, the concrete composition may include a binder, aggregate, and mixing water.

[0073] The above binder may be, for example, at least one of cement, blast furnace slag, fly ash, and silica fume.

[0074] The above cement may be one or more of, for example, Portland cement, ground granulated blast furnace slag cement, fly ash cement, rapid-hardening cement, low heat cement, sulfate resistant cement, white cement, or calcium aluminate cement, but is not limited thereto.

[0075] The above cement contributes to the development of concrete strength by forming hydration products through a hydration reaction, and when used in combination with other binders, it can provide additional effects such as increased long-term strength, reduced heat of hydration, and improved chemical resistance.

[0076] The above blast furnace slag can be used, for example, in the form of ground granulated blast furnace slag (GGBFS), which is a byproduct generated during the process of manufacturing iron in a blast furnace.

[0077] The above fly ash may be a material having pozzolanic reactivity, for example, as fine fly ash generated during coal combustion.

[0078] The above fly ash can improve the long-term strength of concrete and provide effects such as reducing heat of hydration, improving slump retention, improving workability, and improving durability by reacting with calcium hydroxide among the cement hydration products to form secondary hydration products.

[0079] The above silica fume, for example, is a byproduct generated during the manufacturing process of metallic silicon or ferrosilicon alloys and may consist of very fine amorphous silica (amorphous silicon dioxide) with a particle size of tens of nanometers.

[0080] The above silica fume has excellent pozzolanic reactivity and can significantly improve the early strength and long-term strength of concrete by reacting with cement hydration products to form a dense CSH gel.

[0081] In addition, silica fume can improve the interfacial transition zone (ITZ) between cement particles and aggregates, and provide effects such as reduced porosity, improved chemical resistance, and reduced permeability.

[0082] The above aggregate is an essential component that constitutes the volume of the concrete, suppresses shrinkage and deformation of the cement paste, and contributes to securing overall mechanical strength.

[0083] The above aggregates can be classified into fine aggregates and coarse aggregates according to particle size, and may be included in appropriate proportions depending on the type, use, and required performance of the concrete.

[0084] The above fine aggregate may be, for example, a material with a particle size of 5 mm or less, and may be one or more of natural sand, crushed sand, artificial sand, or recycled aggregate.

[0085] The above fine aggregate affects the workability, finishability, and uniform paste dispersion of the concrete, and combines with the cement paste within the concrete to form a continuous matrix.

[0086] The above coarse aggregate may be, for example, a material having a particle size greater than 5 mm and less than or equal to 25 mm, gravel, crushed stone, recycled coarse aggregate, or a mixture thereof.

[0087] The above coarse aggregate contributes to the compressive strength, modulus, creep resistance, and inhibition of drying shrinkage of concrete, and also plays a role in minimizing gaps between aggregates and preventing excessive use of cement paste.

[0088] The above aggregate may be composed of materials of suitable quality, and aggregate of a single particle size or a mixed particle size may be used depending on the purpose of use.

[0089] In addition, since the surface condition, particle size distribution, and mixing ratio of the aggregate affect the fluidity, strength development, resistance to material segregation, and durability of the concrete, in one embodiment of the present invention, they can be appropriately adjusted according to the usage conditions and performance requirements of the concrete.

[0090] The above-mentioned mixing water can be used as a component to promote the hydration reaction of cement in concrete and to ensure the mixing and fluidity of materials during concrete mixing.

[0091] The above-mentioned mixed water may be, for example, one or more of tap water, ground water, river water, process water, or recycled wash water, but is not limited thereto, and it is desirable that it does not contain excessive impurities that adversely affect the strength or hardening characteristics of the concrete.

[0092] The amount of the above-mentioned mixing water added can be adjusted to be between 25 parts by weight and 60 parts by weight relative to the total weight of the cement or binder, or so that the water-to-binder ratio (W / B) is between 0.25 and 0.60. This range is suitable for ensuring a balanced balance of fluidity, workability, and strength development of the concrete.

[0094] The present invention will be described in more detail below through examples. These examples are merely illustrative of the present invention, and therefore the scope of the present invention should not be interpreted as being limited by these examples.

[0096] Examples 1 to 3 and Comparative Example 1

[0097] An admixture composition was prepared by mixing the compositions as shown in Table 1 below.

[0098] Classification (weight part) Methylcellulose-based thickener Meeting-type thickening system Suppressant Core-shell nanoparticles Comparative Example 1 20 - 80 - Example 1 - 20 80 - Example 2 - 20 40 40 Example 3 10 10 40 40

[0099] Evaluation example

[0100] Table 2 shows a comparison of the compressive strength, strength reduction rate, air content, and slump results of Example 1 and Comparative Example 1.

[0101] Example 1 utilizes an associative thickener and exhibits superior characteristics in compressive strength, the rate of strength reduction due to rainfall, and resistance to material separation compared to the existing product (Comparative Example 1) using a methylcellulose-based thickener under rainfall conditions. This is attributed to the difference in how associative thickeners and methylcellulose-based thickeners achieve viscosity. Methylcellulose-based thickeners increase viscosity through physical entanglement, whereas associative thickeners regulate viscosity through associative action that forms a network structure. This associative structure is effective in adsorbing cement particles within the concrete mixture and dispersing them evenly, thereby maintaining the flowability of the mixture while simultaneously improving strength. On the other hand, methylcellulose-based thickeners may impart viscosity locally, raising a significant concern regarding performance degradation in rainfall environments where rainwater flows into the entire concrete pouring area. Therefore, Example 1, which includes an associative thickener, demonstrates superior performance compared to existing products by addressing the issues of strength reduction and material separation that may occur under rainfall conditions.

[0102] As a result of comparing compressive strength based on the 28th day of curing, Example 1 showed improvements of 15.29%, 16.19%, and 17.41% compared to Comparative Example 1 in environments with rainfall amounts of 0 mm / hr, 3 mm / hr, and 6 mm / hr, respectively. Overall, it was found that there was a strength enhancement effect compared to existing products, and the effect was found to be higher in rainfall environments of 3 mm / hr and 6 mm / hr than in the absence of rainfall at 0 mm / hr.

[0103] As a result of comparing the strength reduction rate relative to rainfall of 0 mm / hr, Example 1 showed a reduction of 2.20% and 6.36% in rainfall environments of 3 mm / hr and 6 mm / hr, respectively, compared to the environment without rainfall. These results represent an improvement of 2.9 times and 1.8 times, respectively, compared to the strength reduction rate of the Comparative Example. The air content of Comparative Example 1 and Example 1 satisfied the air content criteria with 3.8% and 4.8%, respectively, and the slump of Comparative Example 1 and Example 1 was similar at 185 mm and 180 mm, respectively. Overall, Example 1, which used an associative thickener, showed improved effects in terms of compressive strength and resistance to material separation compared to the Comparative Example, which used a conventional methylcellulose-based thickener, and it was confirmed that the effect was particularly superior in rainfall environments.

[0104] division 28-day compressive strength (MPa) according to rainfall Reduction rate (%) of 28-day cured strength compared to rainfall of 0 mm / hr Air volume (%) Slump (mm) 0mm / hr 3mm / hr 6mm / hr 3mm / hr 6mm / hr Comparative Example 1 27.82 26.04 24.57 6.40 11.68 3.8 185 Example 1 31.77 31.07 29.75 2.20 6.36 4.8 180

[0105] Table 3 shows a comparison of the compressive strength, strength reduction rate, air content, and slump results of Comparative Example 1 and Examples 1 and 2.

[0106] Example 2 contains core-shell nanoparticles and was found to be capable of improving strength reduction caused by rainwater inflow in rainfall environments, and particularly effective in enhancing initial strength. This effect is achieved by the core-shell nanoparticles promoting the hydration reaction of cement and acting as an internal filler to fill the voids between cement particles. Accordingly, the reduction in compressive strength caused by rainwater inflow can be suppressed, thereby providing superior strength performance compared to existing products.

[0107] As a result of comparing the initial strength, which is the compressive strength at 7 days of age, Example 2 was found to be improved by 28.40%, 19.36%, and 14.81% compared to Comparative Example 1 in rainfall environments of 0 mm / hr, 3 mm / hr, and 6 mm / hr, respectively. Overall, the strength enhancement effect compared to existing products was excellent, and a strength enhancement effect of about 15% was confirmed in rainfall environments of 3 mm / hr and 6 mm / hr.

[0108] As a result of comparing the strength reduction rate at 7 days of age with a rainfall of 0 mm / hr, Example 2 showed a reduction of 6.83% and 13.98% in environments with rainfall of 3 mm / hr and 6 mm / hr, respectively, compared to an environment without rainfall. These results represent an improvement of 2.6 times and 1.4 times, respectively, compared to the strength reduction rate of Comparative Example 1, and an improvement of 1.9 times and 1.1 times, respectively, compared to the strength reduction rate of Example 1.

[0109] The air content of Comparative Example 1, Example 1, and Example 2 satisfied the air content criteria with 3.8%, 4.8%, and 4.9%, respectively, and the slump was similar with 185mm, 180mm, and 185mm.

[0110] division 7-day compressive strength (MPa) according to rainfall 7-day cured strength reduction rate (%) compared to rainfall of 0 mm / hr Air volume (%) Slump (mm) 0mm / hr 3mm / hr 6mm / hr 3mm / hr 6mm / hr Comparative Example 1 17.84 14.62 14.26 18.05 20.07 3.8 185 Example 1 20.06 17.48 16.99 12.86 15.3 4.8 180 Example 2 19.46 18.13 16.74 6.83 13.98 4.9 185

[0111] Table 4 shows a comparison of the results of Comparative Example 1 and Example 3. Example 3 is a composition based on Example 2, which includes an associative thickener and core-shell nanoparticles, but with improved economic efficiency achieved by replacing some of the associative thickeners with methylcellulose-based thickeners. Associative thickeners are relatively more expensive than methylcellulose-based thickeners and are sensitive to pH environments. On the other hand, while methylcellulose-based thickeners have slightly lower resistance to material separation than associative thickeners, they offer a lower price and excellent chemical stability. Therefore, Example 3 improves economic efficiency and pH stability compared to Example 2 by using a combination of the two thickeners, while simultaneously securing an effect of enhancing initial and long-term strength through the application of core-shell nanoparticles. As a result, Example 3 can not only prevent strength degradation due to rainwater inflow but also secure competitiveness in terms of cost compared to Examples 1 and 2.

[0112] As a result of comparing compressive strength based on the 28th day of curing, Example 3 showed improvements of 14.65%, 15.48%, and 15.06% compared to the comparative example in rainfall environments of 0mm / hr, 3mm / hr, and 6mm / hr, respectively. Overall, it was found that there was a strength enhancement effect compared to existing products, and the effect was found to be higher in rainfall environments of 3mm / hr and 6mm / hr than in the absence of rainfall at 0mm / hr.

[0113] As a result of comparing the intensity reduction rate with respect to rainfall of 0 mm / hr, Example 3 showed a reduction of 3.63% and 8.95% in rainfall environments of 3 mm / hr and 6 mm / hr, respectively, compared to a no-rainfall environment. These results represent an improvement of 1.8 times and 1.3 times, respectively, compared to the intensity reduction rate of the comparative example.

[0114] The air content of Comparative Example 1 and Example 3 was 3.8% and 5.7%, respectively, satisfying the air content criteria, and the slump of Comparative Example 1 and Example 3 was 185 mm and 200 mm, respectively, confirming that Example 3 had higher fluidity.

[0115] In summary, Example 3, which uses a combination of an associative thickener and a methylcellulose-based thickener and core-shell nanoparticles, showed improved effects in terms of compressive strength and resistance to material separation compared to Comparative Example 1, which used a conventional methylcellulose-based thickener, and it was confirmed that the effect was particularly superior in a rainfall environment.

[0116] division 28-day compressive strength (MPa) according to rainfall Reduction rate (%) of 28-day cured strength compared to rainfall of 0 mm / hr Air volume (%) Slump (mm) 0mm / hr 3mm / hr 6mm / hr 3mm / hr 6mm / hr Comparative Example 1 27.82 26.04 24.57 6.4 11.68 3.8 185 Example 3 31.97 30.81 29.11 3.63 8.95 5.7 200

Claims

Claim 1 A concrete admixture composition comprising a methylcellulose thickener, an associative thickener and a water reducer, and core-shell nanoparticles, wherein, based on 100 parts by weight of the total concrete admixture composition, the methylcellulose thickener is 5 to 20 parts by weight, the associative thickener is 5 to 20 parts by weight, the water reducer is 35 to 80 parts by weight, and the core-shell nanoparticles are 35 to 50 parts by weight, and when poured in an environment with a rainfall of 6 mm / hr, the reduction rate of compressive strength at 28 days compared to a rainfall of 0 mm / hr is 8.95% or less. Claim 2 A concrete admixture composition according to claim 1, wherein the associative thickener is at least one of a urethane-based associative thickener, an acrylic-based associative thickener, and a methylcellulose-based associative thickener. Claim 3 A concrete admixture composition according to claim 1, wherein the water reducer is at least one of a polycarboxylic acid-based water reducer, a naphthalene-based water reducer, a melamine-based water reducer, and a lignin-based water reducer. Claim 4 delete Claim 5 A concrete admixture composition according to claim 1, wherein the core comprises a metal oxide. Claim 6 A concrete admixture composition according to claim 1, wherein the shell comprises calcium. Claim 7 delete Claim 8 A concrete admixture composition according to claim 1, wherein the methylcellulose thickener comprises at least one of methylcellulose, hydroxypropyl methylcellulose, hydroxyethyl methylcellulose, and hydroxybutyl methylcellulose. Claim 9 delete Claim 10 delete Claim 11 delete Claim 12 A concrete composition comprising any one of claims 1 to 3, 5, 6 and claim 8.

Images