One-Part Early Strength Concrete Admixture Containing a Liquid Alkaline Activator and Method of Manufacturing Thereof

Abstract

The present invention relates to a one-component rapid-strength admixture containing a liquid alkali stimulant and a method for manufacturing the same. More specifically, regarding a rapid-strength admixture added to general concrete containing a large amount of slag in the production of cold-weather concrete, the invention relates to a one-component rapid-strength admixture containing a liquid alkali stimulant that maintains strength above a certain level from the beginning and improves field applicability by manufacturing the liquid alkali stimulant and the general rapid-strength admixture, which previously existed as a two-component system, into a one-component system, and a method for manufacturing the same.

Description

Technology Field

[0001] The present invention relates to a one-component rapid-strength admixture containing a liquid alkali stimulant and a method for manufacturing the same. More specifically, regarding a rapid-strength admixture added to general concrete containing a large amount of slag in the production of cold-weather concrete, the invention relates to a one-component rapid-strength admixture containing a liquid alkali stimulant that maintains strength above a certain level from the beginning and improves field applicability by manufacturing the liquid alkali stimulant and the general rapid-strength admixture, which previously existed as a two-component system, into a one-component system, and a method for manufacturing the same. Background Technology

[0002] Concrete admixtures are materials added to control the physical properties of concrete, such as fluidity, dispersibility, and strength development, during the mixing of concrete composed of cement, aggregates, and water. These admixtures are mainly classified into water reducers, rapid-hardening agents, air-entraining agents, and retarders; among them, water reducers are widely used as key materials that enable sufficient workability while reducing the unit water content.

[0003] In particular, among chemical admixtures, polycarboxylic acid (hereinafter “PC-based”) high-performance superplasticizers exhibit a high water reduction rate even in small quantities compared to other classes of superplasticizers, and have the advantage of significantly improving the dispersibility of concrete. For this reason, PC-based admixtures are currently the most widely applied throughout the concrete industry.

[0004] Meanwhile, cold-weather concrete constructed during the winter (low-temperature conditions) faces the problem of reduced hydration reaction and delayed early strength development due to low ambient temperatures. Accordingly, various techniques have been proposed at construction sites to ensure early strength. For example, these include ① manufacturing rich-mix concrete by increasing the unit cement content, ② promoting the hydration reaction by minimizing the unit water content using high-performance superplasticizers, and ③ using rapid-strengthening cement (Type 3 cement).

[0005] However, all of these methods entail problems such as increased unit costs, deterioration of concrete long-term performance, and reduced workability. In particular, increasing the unit cement content not only raises material costs but also increases the likelihood of shrinkage cracking, while the use of special water-reducing agents or high-early-strength cement carries the disadvantage of being significantly more expensive than standard cement. Consequently, there is a problem in that the cost-saving effects achieved through shortened construction periods are limited.

[0006] In addition, according to the recently revised "Specifications for Cold Weather Concrete [KCS 14 20 40, revised on Dec. 30, 2024]," a temperature correction value of +6 MPa must be applied. As a result, as further increases in material costs and production costs are predicted, a new approach is required to ensure the quality of winter concrete without reflecting these upward factors, rather than simply strengthening construction management. This involves improving material performance or technically improving curing methods. Prior art literature

[0007] Korean Registered Patent Publication No. 10-2153658 (Title of Invention: Early Strength Accelerating Cement for Winter Season, Date of Publication: 2020.09.09) The problem to be solved

[0008] The objective of the present invention is to provide a one-component rapid-strength admixture and a method for manufacturing the same, wherein the rapid-strength admixture is added to general concrete containing a large amount of slag during the manufacture of cold-weather concrete, and the liquid alkali stimulator is manufactured into a one-component form to enhance field applicability by maintaining strength above a certain level from the beginning, and the liquid alkali stimulator and general rapid-strength admixture, which previously existed as a two-component system, are combined.

[0009] The control measures of the present invention are not limited to the problems mentioned above, and other unmentioned problems will be clearly understood by a person skilled in the art from the description below. means of solving the problem

[0010] To solve the aforementioned problem, the present invention provides a one-component rapid-strengthening admixture comprising a liquid alkali stimulator and a polycarboxylic acid-based rapid-strengthening admixture, wherein the liquid alkali stimulator and the polycarboxylic acid-based rapid-strengthening admixture are mixed in a liquid state and provided as a one-component type.

[0011] In addition, the present invention provides a one-component rapid-strengthening admixture comprising a liquid alkali stimulant characterized in that the liquid alkali stimulant is selected from the group consisting of a sodium sulfate solution, a calcium nitrate solution, and a sodium hydroxide solution.

[0012] In addition, the present invention provides a one-component rapid-strengthening admixture comprising a liquid alkali stimulant characterized in that the liquid alkali stimulant is a sodium sulfate solution.

[0013] In addition, a one-component rapid-strengthening admixture is provided, wherein, with respect to the total weight of the one-component rapid-strengthening admixture, the liquid alkali stimulator is 1 to 50 weight % and the polycarboxylic acid-based rapid-strengthening admixture is 50 to 99 weight %.

[0014] Additionally, the present invention provides a method for manufacturing a one-component rapid-strength admixture comprising a liquid alkali stimulant, characterized by including a water preparation step in which water is prepared in a manufacturing tank; a liquid stimulant introduction step in which a liquid stimulant is introduced into the water; a first stirring step in which a first mixture of the water and the liquid stimulant is stirred for 15 to 60 minutes; a defoaming agent introduction step in which a defoaming agent is introduced into the first mixture; a rapid-strength admixture introduction step in which a rapid-strength admixture is introduced into the first mixture into which the defoaming agent has been introduced; and a second stirring step in which a second mixture of the defoaming agent, the first mixture, and the rapid-strength admixture is mixed is stirred for 20 to 60 minutes.

[0015] In addition, a cold-weather concrete composition is provided, characterized by comprising water, coarse aggregate, fine aggregate, a binder, and the one-component rapid-strengthening admixture of claim 1.

[0016] In addition, the present invention provides a cold-weather concrete composition characterized in that the binder comprises cement and slag, the cement is 80% to 99% by weight, the slag is 20% to 1% by weight, and the one-component rapid-strengthening admixture is 1% to 1.3% by weight relative to the total weight of the binder.

[0017] In addition, the present invention provides a cold-weather concrete composition characterized by the fact that the compressive strength of the above cold-weather concrete composition exhibits a compressive strength of 68 to 78% of the quality standard strength at an initial curing temperature of 20°C and 24 hours of age, and exhibits a compressive strength of 89% or more of the quality standard strength at 3 days of age, approximately 96 to 100% or more at 7 days of age, and 104 to 120% or more at 28 days of age, thereby enabling the simultaneous securing of early strength and long-term strength without temperature correction. Effects of the invention

[0018] According to a one-component rapid-strengthening admixture containing a liquid alkaline stimulant and a method for manufacturing the same according to one embodiment of the present invention, one or more of the following effects are provided.

[0019] First, the one-component rapid-strengthening admixture according to the present invention improves upon the existing two-component structure, which requires mixing a liquid alkali stimulant and a powder or liquid rapid-strengthening admixture separately in a mixer. Since it is provided in a one-component form consisting of a single solution, the mixing process at the site is simplified, and material separation or mixing errors are minimized, thereby offering excellent advantages in field applicability, such as improved construction efficiency and uniformity of quality.

[0020] Second, the one-component rapid-strength admixture according to the present invention is formulated to enable early strength development even under low winter conditions (0~4℃), allowing the target strength to be reached early without the need for separate continuous high-temperature curing or insulation devices during cold weather concrete construction. In particular, sufficient strength can be secured even in adverse environments where the temperature is maintained at 20℃ for 24 hours after concrete pouring and then at 0℃ for 28 days, thereby enabling early demolding and continuous process execution.

[0021] Third, the target strength can be secured under conditions where the +6 MPa temperature correction value is not applied due to the revision of the “Cold Weather Concrete Specification [KCS 14 20 40, Dec. 30, 2024]”. Therefore, quality standards can be satisfied without increasing the unit cement content or using special rapid-strength cement, which provides economic benefits such as reduced material costs and construction costs.

[0022] Fourth, by optimizing the reaction balance between the liquid alkali stimulant and the early strength components, the risk of cracking due to rapid hydration reaction or a decrease in long-term strength is low while the early strength is developed quickly, thus providing an effect of improving quality stability that can simultaneously secure early strength and long-term durability.

[0023] Fifth, the one-component rapid-strengthening admixture according to the present invention has the advantage of improving work safety and environmental friendliness because it does not require separate handling of high-concentration alkaline solutions at the site, thereby reducing the risk of chemical exposure for workers and improving safety during storage and transportation processes.

[0024] Sixth, the one-component rapid-strength admixture according to the present invention has the advantage of excellent industrial applicability because it can utilize existing concrete manufacturing facilities and mixing systems without requiring separate equipment modifications, making it applicable to various fields such as cold-weather concrete, precast concrete, and emergency repair concrete.

[0025] Seventh, the cold-weather concrete composition according to the present invention exhibits a compressive strength of approximately 68-78% of the quality standard strength at an initial curing temperature of 20℃ and 24 hours of age, which not only sufficiently exceeds the formwork removal standard of 5MPa for vertical members (columns, walls), but also has the advantage of stably satisfying at least 14MPa, which is 2 / 3 times the design standard compressive strength that is the formwork removal standard for horizontal members (slabs and beam bottoms).

[0026] Eighth, additionally, the cold-weather concrete composition according to the present invention exhibits a compressive strength of at least 89% of the quality standard strength at 3 days of age, at least 96 to 100% at 7 days of age, and at least 104 to 120% at 28 days of age, thereby enabling early strength to be secured without temperature correction and possessing excellent strength development characteristics that sufficiently satisfy the demolding criteria of the structure even during winter construction. Therefore, early strength and long-term strength can be secured simultaneously without increasing the amount of binder during winter casting, and it provides economic and construction advantages that eliminate the need for the application of conventional temperature correction strength.

[0027] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by a person skilled in the art from the description in the claims. Brief explanation of the drawing

[0028] Figure 1 is an image of test specimens (7 types) according to the mixing ratio of cement and slag of the binder. Figure 2 is a graph showing the mortar strength measured for seven types of test specimens in Figure 1. Figure 3 is a graph showing the ratio of the mortar strength measured in Figure 2 to OPC (Portland cement). Figure 4 is a graph showing the mortar strength measured for the test specimens according to Table 1. Figure 5 is a graph showing the mortar strength measured according to the test specimens based on the mixing ratios in Table 2. Figure 6 is a graph showing the mortar strength measured according to the test specimens based on the mixing ratios in Table 3. Figure 7 is an image showing a liquid alkaline stimulant prepared according to the first manufacturing example of the present invention and the process of mixing it. Figure 8 is a graph showing concrete curing conditions. Figure 9 is a graph showing the concrete strength measured under the curing conditions according to Figure 8. Figure 10 is a graph comparing the compressive strength of concrete with respect to a one-component rapid-strength admixture according to the present invention and a general rapid-strength admixture. Figure 11 is a graph comparing compressive strength according to the ratio of cement to slag. Specific details for implementing the invention

[0029] The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Throughout the specification, the same reference numerals refer to the same components.

[0030] The size or shape of components depicted in the drawings attached to this specification may be exaggerated for clarity and convenience of explanation. It should be noted that identical components in each drawing may be depicted with the same reference numeral. Furthermore, detailed descriptions of functions and configurations of known technology that are deemed to unnecessarily obscure the essence of the invention may be omitted.

[0031] The terms used herein are for describing specific embodiments and are not intended to limit the invention. As used herein, the singular form may include the plural form unless the context clearly indicates otherwise. Furthermore, throughout this specification, when a part is described as "comprising" a certain component, it means that it may include additional components unless specifically stated otherwise.

[0032] When it is stated that one component is “connected” or “connected” to another component, it should be understood that while it may be directly connected or connected to that other component, there may also be other components in between. Conversely, when it is stated that one component is “directly connected” or “directly connected” to another component, it should be understood that there are no other components in between. Other expressions used to describe relationships between components should be interpreted in the same way.

[0033] Terms such as top, bottom, upper surface, lower surface, or upper, lower, used in this specification are used to distinguish relative positions among components. For example, while the upper part of a drawing may be designated as the upper part and the lower part as the lower part for convenience, in practice, the upper part may be designated as the lower part and the lower part as the upper part without departing from the scope of the present invention.

[0034] Terms including ordinal numbers, such as "the first," "the second," etc., as described in this specification may be used to describe various components, but said components are not limited by said terms. These terms are used merely to distinguish that each component is a different component and are not bound by the order of manufacture; furthermore, the names may not match between the detailed description of the invention and the claims.

[0035] All terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains, unless otherwise defined. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this specification.

[0036] Hereinafter, a one-component rapid-strengthening admixture comprising a liquid alkali stimulant according to one embodiment of the present invention and a method for manufacturing the same will be described with reference to the drawings.

[0037] FIG. 1 is an image of test specimens (7 types) according to the mixing ratio of cement and slag of the binder; FIG. 2 is a graph showing the mortar strength measured for the 7 test specimens of FIG. 1; FIG. 3 is a graph showing the ratio of the mortar strength measured in FIG. 2 compared to OPC (Portland cement); FIG. 4 is a graph showing the mortar strength measured for the test specimens according to Table 1; FIG. 5 is a graph showing the mortar strength measured according to the test specimens according to the mixing ratio of Table 2; FIG. 6 is a graph showing the mortar strength measured according to the test specimens according to the mixing ratio of Table 3; FIG. 7 is an image showing the liquid alkali stimulant prepared according to the first manufacturing example of the present invention and the process of mixing it; FIG. 8 is a graph showing concrete curing conditions; FIG. 9 is a graph showing the concrete strength measured under the curing conditions according to FIG. 8; FIG. 10 is regarding the one-component rapid-strength admixture according to the present invention and a general rapid-strength admixture. Figure 11 is a graph comparing the compressive strength of concrete and the compressive strength according to the ratio of cement to slag.

[0038] The one-component rapid-strengthening admixture according to the present invention comprises a liquid alkali stimulant and a polycarboxylic acid-based (PC) rapid-strengthening admixture, wherein the liquid alkali stimulant and the polycarboxylic acid-based rapid-strengthening admixture may be mixed in a liquid state and provided as a one-component type.

[0039] The above liquid alkali activator plays a role in inducing early strength development by promoting the hydration reaction of cement, and may include alkali metal compounds such as sodium hydroxide, potassium hydroxide, sodium silicate, and potassium silicate. Meanwhile, the above polycarboxylic acid-based rapid strength admixture functions to help achieve uniform early strength development by controlling the hydration reaction rate while maintaining fluidity by improving the dispersibility of the cement particle surface.

[0040] The term “liquid alkali stimulant” refers to an alkaline substance intended to promote the hydration reaction of a binder for concrete (slag, fly ash, etc.), and includes not only strong alkali or silicate-based solutions such as sodium hydroxide, sodium carbonate, and sodium silicate, but also alkali salts (basic salts) such as sodium sulfate, calcium nitrate, and sodium nitrate.

[0041] Among these, sodium sulfate is a sulfate-based auxiliary stimulant with mild basicity that stably promotes the initial hydration reaction of slag, and sodium silicate is a silicate-based alkali stimulant that reacts with calcium ions in the binder to accelerate the reaction of hydrated calcium silicate (CSH) formation, thereby contributing to the development of early strength.

[0042] The term “one-component type” refers to a form manufactured such that the main components, such as the liquid alkali stimulant, hardening agent, and water reducing agent, coexist stably in a single solution state.

[0043] The term “early-strength admixture” means an admixture used to promote the development of early strength in concrete.

[0044] Since the one-component rapid-strengthening admixture according to the present invention is provided with the two components pre-mixed in a liquid state, a separate on-site mixing process is not required during use, and it facilitates the composition of concrete of uniform quality. In addition, by applying stabilization technology to the liquid composition, separation or sedimentation does not occur even during long-term storage, thereby maintaining excellent storage stability.

[0045] Therefore, the one-component rapid-strength admixture according to the present invention has the effect of simultaneously achieving simplification of the mixing process, improvement of quality uniformity, and improvement of storage stability compared to existing powder-type or multi-component rapid-strength admixtures.

[0046] Meanwhile, the liquid alkali stimulant may be selected from the group consisting of sodium sulfate solution, calcium nitrate solution, and sodium hydroxide solution. Preferably, the liquid alkali stimulant may be a sodium sulfate solution.

[0047] The above-mentioned liquid alkali stimulant plays a key role in improving early strength by promoting the hydration reaction of cement.

[0048] In particular, the sodium sulfate solution in the cement By reacting with (tricalcium aluminate) to rapidly induce the formation of ettringite, initial setting can be accelerated and the rapid hardening effect can be increased.

[0049] Meanwhile, the calcium nitrate solution supplies calcium ions to promote the formation of hydration products (CSH gel) within the cement, and simultaneously, the nitrate ions interact with alkali metal ions to improve freeze-thaw resistance and salt resistance.

[0050] Furthermore, sodium hydroxide solution maintains high alkalinity to increase the solubility of cement particles and enhances the reaction rate during the initial hydration stage, thereby maximizing early strength development. This action of sodium hydroxide is particularly advantageous for effectively mitigating the problem of reduced early strength when pouring concrete in low-temperature environments.

[0051] As such, the liquid alkali stimulator according to the present invention has the effect of promoting the hydration reaction of cement in stages by selectively mixing a single or multiple components from a solution of sodium sulfate, calcium nitrate, sodium hydroxide, etc., and stably securing initial strength and early setting performance even under various environmental conditions.

[0052] The above one-component rapid-strengthening admixture may contain 1 to 50 weight% of the liquid alkali stimulant and 50 to 99 weight% of the polycarboxylic acid-based rapid-strengthening admixture based on the total weight.

[0053] The above compositional ratio is set as the optimal range to simultaneously ensure the long-term stability and rapid strength performance of the admixture while maintaining the reactivity of the alkali stimulant.

[0054] In other words, if the content of the liquid alkali activator is less than 1% by weight, the initial hydration reaction of the cement is not sufficiently induced, and there is a risk that the early strength development will be reduced.

[0055] Conversely, if it exceeds 50% by weight, side effects such as delayed setting, increased bleeding, and surface whitening may occur due to an excess of alkaline components.

[0056] In addition, by maintaining the content of the polycarboxylic acid-based rapid-strengthening admixture at 50 to 99 weight percent, the rapid-strengthening component acts as the main component to ensure fluidity and dispersibility, and even when mixed with an alkali stimulator, a stable one-component solution state can be maintained without an increase in viscosity or precipitation.

[0057] Meanwhile, if the content of the liquid alkali stimulant increases excessively, it may lead to an increase in the viscosity of the admixture or phase separation, which can lower manufacturing stability; therefore, it is necessary to appropriately limit it depending on the type and composition of the rapid-hardening admixture and the type and composition of the liquid alkali stimulant used during manufacturing.

[0058] A method for manufacturing a one-component rapid-strength admixture containing a liquid alkaline stimulant according to the present invention may include a water preparation step in which water is prepared in a mixing tank; a liquid stimulant substance introduction step in which a liquid stimulant substance is introduced into the water; a first stirring step in which a first mixture of the water and the liquid stimulant substance is stirred for 15 to 60 minutes; a defoaming agent introduction step in which a defoaming agent is introduced into the first mixture; a rapid-strength admixture substance introduction step in which a rapid-strength admixture substance is introduced into the first mixture in which the defoaming agent has been introduced; and a second stirring step in which a second mixture of the defoaming agent, the first mixture, and the rapid-strength admixture substance is mixed is stirred for 20 to 60 minutes.

[0059] In the above water preparation step, a certain amount of water is prepared in the mixing tank.

[0060] The above water preparation step is a pretreatment process that secures the solvent serving as the basis for the entire mixing process, while simultaneously ensuring that the liquid stimulating substance and crude mixing substance to be subsequently added are uniformly dispersed.

[0061] In the step of adding the liquid stimulating substance, an alkaline liquid stimulating substance (e.g., selected from sodium sulfate powder, calcium nitrate powder, and sodium hydroxide powder) is added to the water.

[0062] In the above step of adding the liquid stimulating substance, the liquid stimulating substance is a chemical stimulating component capable of promoting the cement hydration reaction, and is initially mixed with water for uniform dispersion.

[0063] In the first stirring step above, a first mixture consisting of water and a liquid stimulating substance is stirred for about 15 to 60 minutes.

[0064] The above stirring time is the time required to homogenize the concentration of the stimulant solution and stabilize the initial reaction. If the stirring time is too short, variations in the stimulant concentration may occur, and if it is too long, unnecessary exothermic reaction and an increase in viscosity may be induced; therefore, it is desirable to maintain the time within the above range.

[0065] In the above defoaming agent addition step, a defoaming agent is added to the first mixture to remove or suppress bubbles that may occur during the mixing process.

[0066] The above defoaming agent addition step is a very important step for the viscosity stability of the final mixture and for preventing sedimentation during storage, and the amount of defoaming agent and stirring intensity can be adjusted to match the viscosity of the liquid mixture.

[0067] In the step of adding the rapid strength admixture, a polycarboxylic acid-based rapid strength admixture is added to the first mixture into which the defoaming agent has been added. The rapid strength admixture serves as the main active component of the admixture and plays a role in accelerating the hydration reaction and inducing the development of early strength in concrete.

[0068] In the second stirring step, the second mixture, which is a mixture of the defoaming agent, the first mixture, and the crude steel mixing material, is stirred for about 20 to 60 minutes. The second stirring step is a step that completes the homogenization of the entire mixture composition. If the mixing time is insufficient, the dispersion of fine particles becomes uneven, and if it is excessively long, pumpability may decrease due to increased viscosity; therefore, the optimal stirring time is maintained within the above range.

[0069] The one-component rapid-strength admixture manufactured through the above-described process eliminates the need for a separate on-site mixing process required in conventional two-component structures, and has the advantage of maintaining stability even during long-term storage while exhibiting the same performance.

[0070] The cold-weather concrete composition according to the present invention may include water, coarse aggregate, fine aggregate, a binder, and the one-component rapid-strengthening admixture of claim 1. The binder comprises cement and slag, wherein the cement is 80% to 99% by weight and the slag is 20% to 1% by weight, and the one-component rapid-strengthening admixture may be 1% to 1.3% by weight relative to the total weight of the binder.

[0071] The above composition ratio is set as the optimal mix ratio to solve the problem of reduced early strength development of concrete in low-temperature environments, such as winter (0~4℃).

[0072] That is, by maintaining the ratio of cement at 80% by weight or more, the heat of the basic hydration reaction can be secured, and by including slag at 20% by weight to 1% by weight, the sustainability of the hydration reaction and the development of long-term strength can be improved.

[0073] Meanwhile, by adding the above-mentioned one-component rapid-strengthening admixture in an amount of about 1 to 1.3 parts by weight relative to the total weight of the binder, the initial hydration reaction is promoted, and the initial target compressive strength (e.g., up to 7 years of age) can be stably secured even under low-temperature conditions.

[0074] Furthermore, since the one-component rapid-strength admixture is uniformly dispersed in liquid form, it is evenly adsorbed onto the surfaces of cement and slag particles, suppressing aggregation between particles and ensuring that the hydration reaction proceeds uniformly within each particle. Consequently, the reactivity of the slag is enhanced, and the generated hydration products (CSH, Aft, etc.) finely fill the pores between particles, forming a dense microstructure.

[0075] The formation of such a homogeneous microstructure blocks the upward movement pathway of moisture, thereby suppressing bleeding, and increases the internal structural density of the cement paste, which has the effect of simultaneously improving strength at early ages and surface stability.

[0076] Therefore, the one-component rapid-hardening admixture of the present invention contributes not only to simple early hardening enhancement but also to the reduction of bleeding, the formation of a homogeneous structure, and the improvement of surface quality.

[0077] Meanwhile, if the above-mentioned rapid-strengthening admixture is added in an amount of less than about 1 part by weight, it is difficult to secure early strength due to reduced dispersibility and the resulting increase in water requirements; if it exceeds 1.3 parts by weight, there is a risk of adverse effects such as increased viscosity, delayed setting, increased air content, and surface hardness occurring due to excessive dispersion. Therefore, it is desirable to add it in the range of about 1 to 1.3 parts by weight to ensure a balance of early fluidity, early strength, workability, and durability.

[0078] In particular, the above composition has the advantage of excellent on-site constructability and economic efficiency, as it can meet the standard strength specified in the Cold Weather Concrete Specification (KCS 14 20 40, revised on Dec. 30, 2024) without the need for separate heat curing or the use of expensive special cement.

[0079] Accordingly, the cold-weather concrete composition according to the present invention has the effect of providing a practical concrete composition that can secure stable strength development and a homogeneous hardening structure even in a low-temperature construction environment, while maximizing the convenience of on-site use of the rapid-strength admixture.

[0080] The compressive strength of the above-mentioned cold-weather concrete composition exhibits a compressive strength of approximately 68~78% of the quality standard strength at an initial curing temperature of 20℃ and 24 hours of age, which not only sufficiently exceeds the formwork removal standard of 5MPa or more for vertical members (columns, walls), but also stably satisfies at least 14MPa, which is 2 / 3 or more of the design standard compressive strength, which is the formwork removal standard for horizontal members (slabs and beam bottoms).

[0081] In addition, the present composition exhibits compressive strength of at least 89% of the quality standard strength at 3 days of age, at least 96-100% at 7 days of age, and at least 104-120% at 28 days of age in all formulations, thereby enabling early strength to be secured without temperature correction and possessing excellent strength development characteristics that sufficiently satisfy the demolding criteria of the structure even during winter construction.

[0082] In particular, the composition of the present invention has the effect of securing sufficient initial strength and long-term strength under field conditions without separate heat curing or external temperature control. In addition, despite being a composition containing 20% ​​by weight of slag, the latent hydraulic properties of the slag are effectively activated through the combined action of a liquid alkali stimulant and a polycarboxylic acid-based rapid-strengthening admixture, thereby inducing the formation of a uniform hydration product (CSH gel) even at low temperatures.

[0083] Therefore, the cold-weather concrete composition of the present invention has the effect of possessing excellent strength retention characteristics that can secure economic efficiency, constructability, and structural reliability while solving the problems of strength reduction and curing delay in conventional winter construction.

[0084] The present invention will be explained in more detail below using examples, but the following examples are merely illustrative to aid in understanding the invention, and the content of the invention is not limited to the following examples.

[0085] Generally, ready-mix concrete plants in multi-regional areas have secured spare silos, enabling the supply of slag-containing cement (cement with added slag); however, regional and general ready-mix concrete plants find it difficult to secure spare silos, making it impossible to supply materials other than cement, fly ash, and slag. (In other words, they are equipped with only three silos: cement, fly ash, and slag. It is difficult to secure a separate silo for slag-containing cement.)

[0086] In addition, rather than using 100% cement, it is advantageous to use a mixture of slag for economic reasons, but it becomes necessary to increase the amount of powder to ensure strength.

[0087] Meanwhile, if a blended cement (slag-containing cement) with a predetermined cement-to-slag mixing ratio is applied to enable supply to most regions nationwide, supply is possible even without the aforementioned spare silos.

[0088] Furthermore, since it is difficult to secure initial strength when slag is mixed, it becomes necessary to apply a rapid-strengthening admixture containing a liquid alkali stimulant capable of stimulating the slag to resolve this issue. In addition, because securing initial strength is difficult when slag is mixed, early formwork demolding is also difficult; therefore, since securing early strength is necessary for early formwork demolding, a rapid-strengthening admixture containing a liquid alkali stimulant is required.

[0089] Test Example 1: Comparative experiment on mortar strength according to slag mixing ratio in binder

[0090] The above first test is conducted to determine how the mortar strength changes according to the mixing ratio of cement and slag in the binder, that is, according to the slag replacement rate, and to determine the optimal mixing ratio.

[0091] In the first test above, to confirm the increase or decrease in cement mortar strength (compressive strength), test specimens are prepared according to mixing ratio while varying the slag substitution rate from 0 weight% to 60 weight%, and a mortar strength (compressive strength) test is performed on them.

[0092] Test specimens are prepared by mixing cement and slag in mixing ratios of 10:0, 9:1, 8:2, 7:3, 6:4, 5:5, and 4:6 (7 types), and the mortar strength of each test specimen (the above 7 types) is measured according to the curing age of 1 day, 2 days, 3 days, 7 days, 14 days, and 28 days (6 days).

[0093] Figure 1 is an image of test specimens (7 types) according to the mixing ratio of cement and slag of the binder.

[0094] When the mortar strength is measured for the 7 types of test specimens according to the above mixing ratios, it appears as shown in Figure 2.

[0095] Referring to Figure 2, the comparative example OPC (Ordinary Portland Cement; Portland Cement) has a high initial mortar strength as indicated by the red line, and at 28 days of age, slag cement (mixed cement) with cement-to-slag mixing ratios of 9:1, 8:2, and 7:3 shows a higher mortar strength compared to OPC.

[0096] In other words, it was confirmed that the initial mortar strength of slag cement tends to be lower than that of OPC, and that at 28 days of age, a mortar strength higher than that of OPC can be secured up to a slag replacement rate of 30 weight%.

[0097] The above-described content is illustrated in a comparison graph as shown in Fig. 3.

[0098] In other words, when showing the ratio of mortar strength of slag cement based on OPC, in the initial period (from day 1 to day 7), all slag cements fall short of OPC, but at 28 days of age, the mortar strength is higher than OPC up to a slag replacement rate of 30%.

[0099] Therefore, it is necessary to secure early strength for slag cement, and to achieve this, it is necessary to apply an early-strengthening admixture containing an alkali stimulant capable of stimulating the slag.

[0100] In the following, a test is conducted to select the type of stimulant, and as one example, the slag cement is based on a cement-to-slag ratio of 8:2. The cement-to-slag ratio can be used up to 7:3, as in the first test example described above.

[0101] Test Example 2: Test of Stimulant Types for Securing Early Strength

[0102] Section 2-1 Test: Mortar Strength Test by Type of Stimulant (1st)

[0103] In Test 2-1, to confirm the early reactive activation of slag, sodium sulfate, glycerin, sodium nitrate, and Kalmarton (product) were used as stimulants, and the mortar strength was measured at ages 1, 2, and 7.

[0104] Table 1 shows the mixing ratios of binder (the ratio of cement to slag is 8:2), water, and sand according to the type of stimulant.

[0108] Table 1. Formulation ratios by type of stimulant

[0109]

[0110] Here, O8S2 indicates that the mixing ratio of OPC and slag is 8:2, AD (Admixture) represents the rapid steel admixture, S10 indicates a mixing amount of sodium sulfate relative to the rapid steel admixture of 10 wt%, N10 indicates a mixing amount of sodium nitrate relative to the rapid steel admixture of 10 wt%, G10 indicates a mixing amount of glycerin relative to the rapid steel admixture of 10 wt%, and K10 indicates a mixing amount of Kalmartron relative to the rapid steel admixture of 10 wt%.

[0111] In addition, W / B is the ratio of water to binder, the B ratio is the ratio of cement to slag in the binder, B represents the amount of binder, W represents the amount of water, and S represents the amount of sand. In Table 1, it means that 0.1 parts by weight of the stimulant corresponding to the sample name was added relative to the total weight, and since the rapid-hardening admixture is 1 part by weight, the ratio of the stimulant is 10 parts by weight relative to 100 parts by weight of the rapid-hardening admixture.

[0112] Figure 4 is a graph showing the mortar strength measured for the test specimens according to Table 1.

[0113] Referring to Figure 4, it can be seen that compared to the initial state without stimulants, sodium nitrate, glycerin, and Kalmarton have no effect as stimulants, and only sodium sulfate has an effect as a stimulant. In particular, in the case of sodium sulfate, it can be seen that strength equivalent to or greater than that of the case without stimulants can be secured at the initial ages of 1 and 2.

[0114] Therefore, tests were conducted as follows regarding the trend of change relative to specific sodium sulfate content and additionally other stimulants.

[0115] Test 2-2: Mortar Strength Test by Type of Stimulant (2nd)

[0116] Test 2-2 was conducted to verify the responsiveness of other stimulants based on the results of Test 2-1, and sodium sulfate, calcium nitrate, and sodium hydroxide were used as stimulants.

[0117] In Test 2-2, the test was conducted to verify the degree of reactive activity according to the concentration of the stimulant, that is, by adjusting the mixing ratio of the admixture.

[0118] Meanwhile, the above 2-2 test was conducted by maintaining the slag cement mixing ratio (cement to slag 8:2) in the same way as the 2-1 test, while adjusting the concentration of each type of activator.

[0119] Test specimens were prepared at 5, 10, and 15 wt% relative to the admixture for sodium sulfate and calcium nitrate, and at 2.5, 5, and 10 wt% for sodium hydroxide, and the mortar strength was measured based on the prepared test specimens.

[0120] Table 2 shows the mixing ratios for each type of additional stimulant. Since the basic explanation is the same as the explanation in Table 1 above, it will be replaced here with that explanation.

[0123] Table 2. Formulation ratios by type of additional stimulant

[0124]

[0125] As mentioned above, S, N, and O following the name represent sodium sulfate, sodium nitrate, and sodium hydroxide, respectively, and the number following them indicates the mixing ratio (concentration) of the stimulant relative to the admixture.

[0126] As shown in Table 1, 1 part by weight of the admixture was used per 100 parts by weight of the binder, and the stimulant represents the mixing ratio of the stimulant to the admixture.

[0127] Figure 5 is a graph showing the mortar strength measured according to the test specimens according to the mixing ratio of Table 2 above, and shows the mortar strength (compressive strength) according to the ages of 1 day, 2 days, and 7 days for each test specimen.

[0128] Referring to Figure 5, it was found that, with the exception of sodium sulfate (15%), there was almost no effect of the stimulants compared to the standard without stimulants. In other words, while other types of stimulants showed minimal effect even when the concentration was increased, in the case of sodium sulfate, the initial intensity was higher as the concentration increased, confirming the need to conduct tests by further increasing the concentration (mixing ratio).

[0130] Tests 2-3: Mortar Strength Test by Type and Concentration of Stimulant (3rd)

[0131] Test 2-3 was conducted to verify the reactivity at each increased concentration by increasing the concentrations of sodium sulfate, calcium nitrate, and sodium hydroxide according to the results of Test 2-2 above.

[0132] Test specimens were prepared with the same conditions as the above-mentioned 2-2 test, but with the concentration (mixing ratio) of the aforementioned stimulant changed to 10 wt%, 20 wt%, 30 wt%, 40 wt%, and 50 wt%, and the mortar strength was measured for the prepared test specimens.

[0133] However, since there are variations and physical properties among admixture manufacturers, a rapid-hardening admixture from a different manufacturer (Company D) than the one used in Test 2-2 was used, and consequently, it showed better results than the previous manufacturer.

[0134] Table 3 shows the mixing ratios by type and concentration of stimulant, and the basic conditions are the same as in Table 2, with only the mixing ratio of the stimulant relative to the rapid-strengthening admixture being different.

[0141] Table 3. Formulation ratios by type and concentration of stimulant (change in admixture manufacturer)

[0142]

[0143] Figure 6 is a graph showing the mortar strength measured for test specimens according to Table 3, and is a graph showing the compressive strength at 1, 2, and 7 days of age, mixed with amounts (%) of 10 wt%, 20 wt%, 30 wt%, 40 wt%, and 50 wt% of liquid alkali stimulators, sodium sulfate (Examples 1 to 5), calcium nitrate (Comparative Examples 2 to 6), and sodium hydroxide (Comparative Examples 7 to 11), with no stimulator added (Comparative Example 1), and liquid alkali stimulators, sodium sulfate (Comparative Examples 2 to 6) and sodium hydroxide (Comparative Examples 7 to 11).

[0144] Referring to Figure 6, when sodium sulfate was used as an stimulant, the initial strength was measured to be superior to Comparative Example 1 (no stimulant added), and when sodium hydroxide was used as an stimulant, the initial strength was also measured to be relatively superior. Meanwhile, in the case of calcium nitrate, the initial strength was superior in some cases depending on the concentration, and it was confirmed that the initial strength varied significantly depending on the mixing ratio.

[0145] Meanwhile, when sodium sulfate is used as an activator, the initial strength development is excellent compared to other activators, so it is desirable to use sodium sulfate as an activator. Since the initial strength is excellent even when used from 10% by weight to 50% by weight, a mixing ratio of 10% to 50% by weight can be a desirable ratio for sodium sulfate.

[0146] In the following example, an early-strengthening admixture was prepared using sodium sulfate as an activator, and after manufacturing concrete using this admixture, the concrete strength was measured to confirm its effectiveness.

[0147] Preparation Example 1: Preparation of a rapid-hardening admixture using sodium sulfate as an alkali stimulant

[0148] When using an alkali stimulant and a rapid-strengthening admixture containing an alkali stimulant separately, they must be added to a mixer separately. However, in reality, it is very difficult to add the alkali stimulant and the rapid-strengthening admixture, which consist of two liquid forms (i.e., a liquid alkali stimulant and a liquid rapid-strengthening admixture), to the mixer in the correct amount.

[0149] Therefore, using a pre-manufactured one-component rapid-strengthening admixture not only resolves these inconveniences but also enables precise quantitative injection, thereby eliminating issues such as the need for additional equipment or variations in injection volume depending on the operator.

[0150] Therefore, it is necessary to manufacture a rapid-strengthening admixture containing a liquid alkali stimulant in a one-component form, and the above-mentioned one-component rapid-strengthening admixture can be manufactured through the following manufacturing process.

[0151] A method for manufacturing a one-component rapid-strength admixture containing a liquid alkaline stimulant may include a water preparation step in which water is prepared in a manufacturing tank; a liquid stimulant introduction step in which a liquid stimulant is introduced into the water; a first stirring step in which a first mixture of the water and the liquid stimulant is stirred for 15 to 60 minutes; a defoaming agent introduction step in which a defoaming agent is introduced into the first mixture; a rapid-strength admixture introduction step in which a rapid-strength admixture is introduced into the first mixture into which the defoaming agent has been introduced; and a second stirring step in which a second mixture of the defoaming agent, the first mixture, and the rapid-strength admixture is mixed is stirred for 20 to 60 minutes.

[0152] The manufacturing temperature is preferably 10℃ to 25℃, and the stirring speed is preferably 500 to 800 rpm.

[0153] Since the solubility of sodium sulfate is 36g in 100g of water at 20℃, based on this, a temperature of 10℃ to 25℃ is desirable, and if the temperature is lower than that, reprecipitation may occur, and if it is higher, further dissolution may occur, which is not desirable.

[0154] Figure 7 is an image showing the process of mixing the liquid alkaline stimulant prepared according to the first manufacturing example.

[0155] When a polycarboxylic acid-based rapid-strengthening admixture is used as a rapid-strengthening admixture, the liquid alkali stimulator can be added in an amount of 1% to 50% by weight, and preferably in an amount of 10% to 50% by weight, the effect of developing early strength as described above appears.

[0156] Concrete containing slag cement is manufactured using the above-mentioned PC-based rapid-strength admixture containing sodium sulfate, and its initial strength is measured to explain, through the following test, whether there is an actual effect of improving initial strength.

[0158] Test Example 3: Compressive strength test of cold-weather concrete prepared using a PC-based rapid-hardening admixture containing a liquid alkali stimulant

[0159] The third test was conducted as follows to evaluate the performance of cold-weather concrete manufactured using the aforementioned one-component rapid-hardening admixture.

[0160] The above concrete consists of water, coarse aggregate, fine aggregate, binder (slag and cement), and rapid-strength admixture. Since the specifications specify a certain ratio for coarse aggregate, fine aggregate, and water, the ratios of the binder and rapid-strength admixture are determined accordingly.

[0161] Here, the binder used was a slag-containing cement (mixed cement) in which cement and slag were mixed in an 8:2 ratio, and the rapid strength admixture used was a one-component rapid strength admixture according to the present invention, in which a PC-based rapid strength admixture was mixed with 10% by weight of a sodium sulfate solution relative to the rapid strength admixture.

[0162] The test was conducted under conditions that were harsher than field curing, with 0℃ curing carried out for 24 hours after rapid heat curing until 28 days of age.

[0163] This is a test designed to ensure the strength of concrete under low winter conditions of 0℃ to 4℃ while enabling a continuous process in the shortest possible time, taking into account the available working time at the site.

[0164] Specifically, this is done to provide cold-weather concrete that can exhibit sufficient strength even in an unfavorable environment where the curing conditions after pouring the concrete are maintained at 20°C for 24 hours and then at 0°C for 28 days.

[0165] Figure 8 is a graph showing the curing temperature conditions described above.

[0166] According to the curing conditions of Fig. 8 above, the compressive strength of concrete to which the one-component rapid-strengthening admixture according to the present invention was applied was measured, and the result as shown in Fig. 9 was obtained.

[0167] Figure 9 is a graph showing the results of measuring compressive strength when cured at 20℃ and when cured under the conditions according to Figure 8, initially cured at 20℃ for 24 hours and then cured at 0℃ until 28 days of age.

[0168] Referring to Fig. 9, it can be seen that the target strength of 30 MPa or more is secured even after 28 days of curing.

[0169] Specifically, for concrete cured at a curing temperature of 20℃, the compressive strength is measured at 17.5MPa at 1 day of age and increases to 57.5MPa by 28 days of age.

[0170] On the other hand, when a curing temperature of 20℃ was applied for up to 24 hours and then a curing temperature of 0℃ was applied until 28 days of age, the compressive strength was measured at 17.5 MPa at 1 day of age, and then increased until 28 days of age, reaching 33.9 MPa at 28 days.

[0171] Accordingly, it has been proven that by using the one-component rapid-strengthening admixture according to the present invention, sufficient early strength can be secured in slag-containing cement (8:2) by satisfying the target strength of 30 MPa or more by 28 days of age under the curing conditions according to Fig. 8, and the target strength can be secured using a new material or curing method that does not require the application of the temperature correction value +6 MPa specified in the cold-weather concrete specifications.

[0172] Meanwhile, as shown in Table 4 below, for concrete compositions, the total composition ratio of binder, water, fine aggregate, and coarse aggregate is 450:175:805:880 based on 30 MPa, that is, approximately 19.4 wt%, 7.6 wt%, 34.8 wt%, and 38.1 wt%, and varies depending on the target mix.

[0173] Table 4 Concrete Composition Ratio

[0174]

[0176] In addition, Figure 10 is a graph showing the compressive strength of concrete with a one-component rapid-strength admixture containing a liquid alkali stimulant according to the present invention and concrete with a general rapid-strength admixture. It can be seen that the compressive strength of the concrete with the one-component rapid-strength admixture according to the present invention was higher from 1 to 28 years of age, satisfying the target strength of 30 MPa or higher.

[0177] In particular, referring to Table 5, it can be seen that early strength and long-term strength can be secured simultaneously without temperature correction by achieving a compressive strength of approximately 68 to 78% of the quality standard strength at an initial curing temperature of 20℃ and 24 hours of age, and at least 89% of the quality standard strength at 3 days of age, at least 96 to 100% at 7 days of age, and at least 104 to 120% at 28 days of age.

[0180] Table 5 Compressive strength during low-temperature curing by quality standard strength

[0181]

[0183] Meanwhile, Figure 11 shows a graph of compressive strength measured for a cement-to-slag ratio of 7:3, indicating that compressive strength was not achieved at 28 days of age. (S0 represents 0% sodium sulfate and S3 represents 3% sodium sulfate; 24 represents a quality standard strength of 24 MPa and 27 represents 27 MPa.)

[0184] In addition, referring to Table 6 below, the cold-weather concrete mix for the test of Table 5 above is as follows, and it can be seen that 1.1 to 1.3 parts by weight of a one-component rapid-hardening admixture was used per 100 parts by weight of binder, and the target performance is satisfied.

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[0190] Table 6 Cold and China Concrete Mix Ratios

[0191]

[0193] As described above, preferred embodiments of the present invention have been illustrated and described with reference to the drawings; however, the present invention is not limited to the specific embodiments described above. Various modifications are possible by those skilled in the art without departing from the essence of the invention as claimed in the patent claims, and such modifications should not be understood individually from the technical spirit or perspective of the present invention.

Claims

Claim 1 delete Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 delete Claim 6 Water; coarse aggregate; fine aggregate; binder; A cold-weather concrete composition comprising a one-component rapid-strength admixture including a liquid alkali stimulant and a polycarboxylic acid-based rapid-strength admixture, wherein the binder comprises cement and slag, and the cement and slag each constitute 80% by weight and 20% by weight, respectively, of the total weight of the binder; the liquid alkali stimulant is a sodium sulfate solution, and the sodium sulfate constitutes 10% to 50% by weight of the total weight of the one-component rapid-strength admixture; and the one-component rapid-strength admixture comprises 1 to 1.3 parts by weight per 100 parts by weight of the binder; and when the cold-weather concrete composition is cured at 20°C for the initial 24 hours and then cured at 0°C until 28 years of age, it exhibits a compressive strength of 68 to 78% of the quality standard strength at an initial curing temperature of 20°C and 24 hours of age, and 89% or more of the quality standard strength at 3 days of age, and at 28 days of age A cold-weather concrete composition characterized by exhibiting a compressive strength of 96 to 100% or more at 7 days and 104 to 120% or more at 28 days.

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