Concrete Composition, Method for Manufacturing Concrete Composition, and Concrete Structure

Abstract

The present invention relates to a concrete composition used in the manufacture of a concrete structure, a method for manufacturing a concrete composition, and a concrete structure. In particular, by calculating the water content of a saturated nanocellulose water dispersion as part of the mixing water and correcting the amount of externally added water in an actual precast concrete secondary product production process, the invention suppresses variations in effective water content, deviations in the water-to-binder ratio, reduction in slump, increase in viscosity, variations in air content, and non-homogenization of mixing, and ensures mix reproducibility, quality homogeneity, production stability, steam curing stability, and early demolding stability. The invention also relates to a concrete composition, a method for manufacturing the same, and a concrete structure manufactured thereby.

Description

Technology Field

[0001] The present invention relates to a concrete composition used in the manufacture of a concrete structure, a method for manufacturing a concrete composition, and a concrete structure. Background Technology

[0002] Concrete structures are widely used in the fields of construction and civil engineering. In particular, precast concrete structures such as flues, bench flues, water pipes, reinforced concrete drainage pipes, concrete manhole blocks for sewers, manholes, and pump room manholes are used in water supply and sewage facilities, drainage facilities, and underground structures.

[0003] These concrete structures must possess compressive strength, durability, and dimensional stability exceeding a certain level, depending on the installation environment and application.

[0004] For example, concrete structures such as water pipes or manholes must satisfy strength performance according to their respective product specifications or design standards.

[0005] Meanwhile, cement is essential for ensuring the strength of concrete structures. However, as cement usage increases, manufacturing costs rise, and the environmental burden also increases due to the generation of carbon dioxide during the manufacturing process. Therefore, there is a need for technology that can reduce cement consumption while still securing the required strength of concrete structures.

[0006] To address the aforementioned problems, technologies have been proposed to apply nanocellulose to improve the performance of concrete or cementitious compositions.

[0007] Nanocellulose is a nano-sized material obtainable from cellulose-based raw materials that has been considered as an additive capable of influencing the hydration reaction, microstructure, and strength development of cementitious materials due to its high specific surface area and hydrophilic functional groups.

[0008] Korean Patent Publication No. 10-1953870 (hereinafter referred to as 'Patent Document 1') discloses a cement composite composition using cellulose nanocrystals (CNC).

[0009] Patent Document 1 relates to a cement composite composition that improves compressive strength using ultrasonically and stirring pretreated cellulose nanocrystals (CNC), and uses a method of adding CNC to water, performing pretreatment such as ultrasonic dispersion and magnetic stirring, and then mixing it with cement and sand.

[0010] In addition, Korean Registered Patent Publication No. 10-2295213 (hereinafter referred to as 'Patent Document 2') discloses a fiber-reinforced high-toughness cement composite composition using cellulose nanocrystals (CNC) together with steel fibers.

[0011] Patent Document 2 relates to a cement composite composition comprising cellulose nanocrystals (CNC) and steel fibers, wherein a method of dispersing CNC by introducing it into water using magnetic stirring, ultrasonic dispersion, high-pressure dispersion, or a combination thereof can be used.

[0012] In addition, Korean Patent Publication No. 10-2020-0116475 (hereinafter referred to as 'Patent Document 3') discloses a cement composition comprising cellulose nanofibers.

[0013] The cement composition of Patent Document 3 contains cement, cellulose nanofibers, and water, and discloses a composition in which the mass ratio of water to cement is 0.4 or less, and the unit amount of cellulose nanofibers is 0.1 kg / m³ or more and 15 kg / m³ or less.

[0014] In addition, Korean Patent Publication No. 10-2025-0157211 (hereinafter referred to as 'Patent Document 4') discloses an eco-friendly concrete composition comprising a cellulose nanogel obtained from prickly pear and bagasse, and a method for manufacturing the same.

[0015] Patent Document 4 describes a method of preparing a cellulose nanogel by diluting compressed cellulose and then grinding it, and mixing it with a cement mixture.

[0016] The cellulose nanogel of Patent Document 4 is a nanogel prepared by diluting compressed cellulose and then grinding it, and it can be understood as focusing on the form of the nanocellulose preparation or the dilution and grinding result.

[0017] The above conventional technologies often evaluate performance primarily based on cement paste, mortar, cement composites, or small test specimens, and it is difficult to consider them as having been verified under conditions identical to the mass production process of actual concrete secondary products.

[0018] In particular, in the case of Patent Documents 1 and 2, a method is used in which a dispersion is formed by immersing a CNC in water and performing pretreatment processes such as ultrasonic dispersion, magnetic stirring, and high-pressure dispersion. While such pretreatment processes are applicable on a laboratory scale, they may be difficult to apply as is in actual precast concrete product manufacturing processes or ready-mix concrete mixing processes due to constraints on productivity, equipment configuration, batch capacity, and process time.

[0019] In addition, when nanocellulose is prepared in the form of a dry powder and added to a cementitious composition, the nanocellulose in powder form can rapidly absorb moisture the moment it comes into contact with the mixing water, and as a result, the nanocellulose powder may swell or aggregate locally before being uniformly dispersed in the mixing water.

[0020] In addition, even if nanocellulose exists in the form of a gel containing moisture, if it is merely a low-concentration liquid dispersion diluted in water or if the moisture content of the nanocellulose is not managed in conjunction with the calculation of concrete mixing water, the actual effective water quantity may fluctuate during concrete mixing. In this case, a decrease in slump, an increase in viscosity, non-homogeneous mixing, deviations in hydration reactions, and deviations in the quality of precast products may occur.

[0021] Therefore, nanocellulose may not be uniformly dispersed within the concrete composition and may be localized in certain areas; as a result, strength variations may increase depending on the location or specimen within the concrete structure. In particular, in fields requiring the repeated production of products of consistent quality, such as precast concrete structures, the non-uniform dispersion of additives can reduce the reproducibility of product quality.

[0022] Furthermore, conventional nanocellulose application technologies as described above often focus on the dispersion of the nanocellulose itself, the improvement of the strength of cement composites, or the enhancement of the dispersibility of the nanocellulose itself. Consequently, they have limitations in presenting mix proportions that satisfy the required compressive strength while reducing cement usage during the actual production process of precast concrete structures for water and sewage systems, such as water pipes or manholes.

[0023] Therefore, there is a need for a concrete composition and a method for manufacturing the same that can be applied to actual concrete secondary product production processes, while ensuring the dispersibility of nanocellulose and simultaneously achieving a reduction in cement usage and the required strength. Prior art literature

[0024] Korean Registered Patent Publication No. 10-1953870 Korean Registered Patent Publication No. 10-2295213 Korean Published Patent Publication No. 10-2020-0116475 Korean Published Patent Publication No. 10-2025-0157211 The problem to be solved

[0025] The present invention was devised to solve the aforementioned problems, and aims to provide a concrete composition, a method for manufacturing the same, and a concrete structure manufactured thereby, which can suppress variations in effective water content, deviations in the water-to-binder ratio, reduction in slump, increase in viscosity, variations in air content, and non-homogenization of mixing by calculating the water content of a saturated nanocellulose water dispersion as part of the mixing water and correcting the amount of externally added water in an actual precast concrete secondary product production process, and thereby secure mix reproducibility, quality homogeneity, production stability, steam curing stability, and early demolding stability. means of solving the problem

[0026] A concrete composition according to one feature of the present invention comprises, in a concrete composition used for manufacturing a concrete structure, cement; aggregate; water; and a saturated nanocellulose water dispersion, wherein the saturated nanocellulose water dispersion is a gel-state water dispersion comprising cellulose nanofibers and retained water retained in the cellulose nanofibers, and the retained water is retained in the cellulose nanofibers to suppress additional free water absorption by the cellulose nanofibers during the mixing of the concrete composition.

[0027] In addition, the moisture content of the saturated nanocellulose water dispersion is adjusted to suppress the additional absorption of free water during concrete mixing.

[0028] In addition, the saturated nanocellulose aqueous dispersion comprises 18 parts by weight or more and 20 parts by weight or less of cellulose nanofiber solids and 80 parts by weight or more and 82 parts by weight or less of retained moisture, based on 100 parts by weight of the saturated nanocellulose aqueous dispersion.

[0029] In addition, the cellulose nanofiber has an average fiber diameter of 50 nm or more and less than 500 nm, and the saturated nanocellulose water dispersion is included in an amount of 0.8 parts by weight or more and 1.2 parts by weight or less per 100 parts by weight of the cement.

[0030] In addition, the aggregate comprises coarse aggregate and crushed fine aggregate, wherein the coarse aggregate is included in an amount of 190 parts by weight or more and 305 parts by weight or less per 100 parts by weight of the cement, and the crushed fine aggregate is included in an amount of 180 parts by weight or more and 285 parts by weight or less per 100 parts by weight of the cement.

[0031] In addition, the saturated nanocellulose aqueous dispersion is a gel-state aqueous dispersion containing cellulose nanofibers extracted from a cellulose-based raw material and not subjected to a drying and pulverizing process, and moisture retained in the cellulose nanofibers.

[0032] In addition, the concrete composition further includes an admixture, and the admixture is included in an amount of 0.8 parts by weight or more and 1.1 parts by weight or less per 100 parts by weight of the cement.

[0033] A method for manufacturing a concrete composition according to one feature of the present invention comprises: a preparation step of preparing a saturated nanocellulose water dispersion; and a composition forming step of mixing the saturated nanocellulose water dispersion, cement, aggregate, and water to form a concrete composition; wherein the saturated nanocellulose water dispersion is a gel-state water dispersion comprising cellulose nanofibers and water retained in the cellulose nanofibers.

[0034] In addition, in the above preparation step, the saturated nanocellulose aqueous dispersion is prepared in a gel state comprising cellulose nanofibers extracted from a cellulose-based raw material and not subjected to a drying and pulverizing process, and the retained moisture contained in the cellulose nanofibers.

[0035] Additionally, in the step of forming the composition, the saturated nanocellulose water dispersion is mixed with the cement, the aggregate, and the water without being prepared as a separate diluent or nanocellulose dispersion.

[0036] In addition, the aggregate includes coarse aggregate and crushed fine aggregate, and in the step of forming the composition, cement with a reduced content compared to the cement content of the standard mix is ​​used, and crushed fine aggregate with a weight corresponding to the difference between the cement content of the standard mix and the reduced content of cement is added to form the concrete composition.

[0037] In addition, the cement with the reduced content is a content reduced by 12% or more and 18% or less compared to the cement content of the standard mix.

[0038] In addition, the saturated nanocellulose aqueous dispersion comprises 18 parts by weight or more and 20 parts by weight or less of cellulose nanofiber solids and 80 parts by weight or more and 82 parts by weight or less of retained moisture, based on 100 parts by weight of the saturated nanocellulose aqueous dispersion.

[0039] In addition, the cellulose nanofiber has an average fiber diameter of 50 nm or more and less than 500 nm, and the saturated nanocellulose water dispersion is mixed in an amount of 0.8 parts by weight or more and 1.2 parts by weight or less per 100 parts by weight of the cement.

[0040] In addition, the aggregate comprises coarse aggregate and crushed fine aggregate, and in the step of forming the composition, the coarse aggregate is mixed in an amount of 190 parts by weight or more and 305 parts by weight or less with respect to 100 parts by weight of the cement, and the crushed fine aggregate is mixed in an amount of 180 parts by weight or more and 285 parts by weight or less with respect to 100 parts by weight of the cement.

[0041] Additionally, the preparation step comprises: a washing and neutralization step for removing residual ions from cellulose nanofibers extracted from a cellulose-based raw material; a moisture content adjustment and saturation step for adjusting the moisture retention state of the cellulose nanofibers; a high-shear dispersion step for imparting shear force to the cellulose nanofibers; and a rheology adjustment step for adjusting the viscosity, fluidity, yield stress, or dispersion stability of the saturated nanocellulose water dispersion.

[0042] A method for manufacturing a concrete composition according to another feature of the present invention comprises: a preparation step of preparing a saturated nanocellulose water dispersion; and a composition forming step of mixing the saturated nanocellulose water dispersion, cement, aggregate, and external mixing water to form a concrete composition; wherein, in the composition forming step, the amount of retained water contained in the saturated nanocellulose water dispersion is calculated as part of the mixing water of the concrete composition, and the amount of external mixing water added is corrected based on the calculated amount of retained water.

[0043] In addition, the composition forming step calculates the retained moisture corresponding to 70% or more and 90% or less of the input amount of the saturated nanocellulose water dispersion as part of the mixing water of the concrete composition.

[0044] Additionally, the composition forming step comprises: a mixing water calculation step for calculating the amount of water retained in the saturated nanocellulose water dispersion as part of the mixing water of the concrete composition; an external mixing water input amount correction step for correcting the amount of external mixing water input based on the calculated amount of water retained; and a mixing step for mixing the saturated nanocellulose water dispersion, cement, aggregate, and the corrected external mixing water.

[0045] A concrete structure according to one feature of the present invention comprises, in the concrete structure, a concrete body formed by curing a concrete composition after it is poured into a mold or die.

[0046] In addition, the concrete structure is any one of a plume, a bench plume, a waterway pipe, and a reinforced concrete drainage pipe, and the concrete body has a compressive strength of 35 MPa or more at 28 days of age.

[0047] In addition, the concrete structure is any one of a concrete manhole block for sewage, a manhole, a prefabricated pump room manhole, a pipe-inserted integrated prefabricated PC manhole, and a pressure pump room manhole, and the concrete body has a 28-day compressive strength of 45 MPa or more. Effects of the invention

[0048] According to the concrete composition, method for manufacturing the concrete composition, and concrete structure of the present invention as described above, the following effects are achieved.

[0049] According to the concrete composition, method for manufacturing the concrete composition, and concrete structure of the present invention, by incorporating a saturated nanocellulose water dispersion, in which the moisture content is adjusted to suppress additional free water absorption by cellulose nanofibers, into the concrete composition, the problem of dry powdered nanocellulose or low-moisture nanocellulose rapidly absorbing moisture and aggregating upon contact with mixing water can be reduced.

[0050] In addition, the amount of retained water contained in the saturated nanocellulose water dispersion is calculated as part of the mixing water of the concrete composition, and since the amount of external water input can be corrected based on the calculated amount of retained water, the actual effective water amount and water-to-binder ratio of the concrete composition can be stably maintained.

[0051] In addition, by calculating the saturated nanocellulose water dispersion by separating it into solid content and mixing water content, the variation in unit water content between batches can be reduced, and accordingly, slump reduction, air content fluctuation, viscosity increase, and mixing variation can be suppressed.

[0052] In addition, since the saturated nanocellulose water dispersion is provided in a gel state containing cellulose nanofibers and moisture retained in the cellulose nanofibers, it can be mixed with cement, aggregate, and water without undergoing a separate nanocellulose dispersion preparation process. Accordingly, the dispersibility of nanocellulose can be secured in the actual concrete secondary product production process, and the mixing homogeneity and mix reproducibility of the concrete composition can be improved without increasing the complexity of the production process.

[0053] In addition, saturated nanocellulose water dispersions can contribute to the stabilization of the effective water content and the homogenization of the rheology of concrete compositions, thereby improving mold filling ability, production stability, quality homogeneity, and product reproducibility in the repetitive production process of precast concrete structures.

[0054] Furthermore, by applying a saturated nanocellulose water dispersion, the variation in compressive strength among test specimens can be reduced compared to the case where powder-type nanocellulose is applied. Therefore, the present invention not only merely increases compressive strength but can also reduce quality variations in precast concrete products manufactured using the same mix and production process.

[0055] In addition, by including a saturated nanocellulose water dispersion in an amount of 0.8 parts by weight or more and 1.2 parts by weight or less per 100 parts by weight of cement, the development of compressive strength can be stabilized while maintaining the mix stability of the concrete composition.

[0056] In addition, the compressive strength required for concrete structures can be secured even if the cement content is reduced compared to the standard mix and crushed fine aggregate is added in an amount corresponding to the reduced cement weight.

[0057] In addition, since the amount of cement used can be reduced, the manufacturing cost of the concrete composition can be lowered, and the burden of carbon dioxide emissions generated during the cement manufacturing process can be reduced due to the decrease in cement usage.

[0058] In addition, based on the stabilization of effective water content, rheological homogenization, and improvement of mix reproducibility, the present invention is advantageous for stabilizing the development of early strength and improving early demolding stability during the steam curing process of precast concrete structures.

[0059] In addition, the present invention can be applied to precast concrete structures such as flumes, bench flumes, water pipes, reinforced concrete drainage pipes, concrete manhole blocks for sewers, manholes, prefabricated pump room manholes, pipe-inserted integrated prefabricated PC manholes, and pressure pump room manholes. Brief explanation of the drawing

[0060] FIG. 1 is a flowchart illustrating a method for preparing a concrete composition using a saturated nanocellulose water dispersion of the present invention. Figure 2 is a graph showing the change in compressive strength according to the content of the saturated nanocellulose water dispersion of the concrete composition of the present invention. FIG. 3 is a graph showing the change in compressive strength according to the cement reduction rate of the concrete composition of the present invention. Figure 4 is a graph comparing the compressive strength deviation between the concrete composition of the present invention using a saturated nanocellulose water dispersion and a control group using powdered nanocellulose. Specific details for implementing the invention

[0061] The following description merely illustrates the principles of the invention. Therefore, those skilled in the art may invent various devices that embody the principles of the invention and are included within the concept and scope of the invention, even if they are not explicitly described or illustrated in this specification. Furthermore, all conditional terms and embodiments listed in this specification are, in principle, explicitly intended only for the purpose of understanding the concept of the invention and should be understood as not being limited to the embodiments and conditions specifically listed as such.

[0062] The aforementioned objectives, features, and advantages will become clearer through the following detailed description in conjunction with the attached drawings, and accordingly, a person skilled in the art to which the invention pertains will be able to easily implement the technical concept of the invention.

[0063] The embodiments described herein will be described with reference to cross-sectional and / or perspective views, which are exemplary illustrations of the invention. Technical terms used herein are used merely to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as 'comprising' or 'comprising' are intended to indicate the presence of the features, numbers, steps, actions, components, parts, or combinations thereof described herein, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0064] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. In describing the various embodiments below, for convenience, the same name and reference number will be assigned to components performing the same function, even if the embodiments differ. Additionally, configurations and operations already described in other embodiments will be omitted for convenience.

[0065] In the following description, 'concrete composition' may refer to a pre-hardening composition used in the manufacture of concrete structures.

[0066] In addition, 'concrete structure' may refer to a structure formed by curing a concrete composition after it has been poured into a mold or die.

[0067] In addition, 'standard mix' refers to a concrete composition that does not contain saturated nanocellulose water dispersions, and may mean a comparative standard mix containing cement, aggregate, water, and admixtures to correspond to the target compressive strength of the concrete structure to be manufactured.

[0068] In addition, '28-day compressive strength' may refer to the compressive strength measured at 28 days of age for a test specimen or concrete body made of a concrete composition.

[0069] In addition, 'parts by weight' may mean a relative weight based on 100 parts by weight of cement, unless otherwise specified.

[0070] Concrete composition of the present invention

[0071] First, the concrete composition of the present invention will be described.

[0072] The concrete composition of the present invention can be used in the manufacture of concrete structures.

[0073] The concrete composition may be composed of cement, aggregate, water, and a saturated nanocellulose water dispersion.

[0074] Cement is used as a binder to develop the strength of concrete structures.

[0075] Aggregates function to contribute to the volumetric stability and strength development of concrete compositions.

[0076] The aggregate may be composed of coarse aggregate and crushed fine aggregate.

[0077] It is preferable that coarse aggregate be included in an amount of 190 parts by weight or more and 305 parts by weight or less per 100 parts by weight of cement.

[0078] If coarse aggregate is included in an amount of less than 190 parts by weight, the volumetric stability or economic efficiency of the concrete composition may be reduced, and if it is included in an amount exceeding 305 parts by weight, the filling ability or moldability of the concrete composition may be reduced.

[0079] It is preferable that crushed fine aggregate be included in an amount of 180 parts by weight or more and 285 parts by weight or less per 100 parts by weight of cement.

[0080] If crushed fine aggregate is included in an amount of less than 180 parts by weight, the filling capacity of the concrete composition may be reduced, and if it is included in an amount exceeding 285 parts by weight, the binding strength by the cement paste may be reduced.

[0081] The content range of coarse aggregate and crushed fine aggregate can be set by considering both a standard mix that does not contain saturated nanocellulose water dispersion and a mix that contains saturated nanocellulose water dispersion, reduces the cement content, and adds crushed fine aggregate in a weight corresponding to the reduced cement weight.

[0082] For example, in the standard mix of a 45 MPa grade product, the coarse aggregate may be about 197.64 parts by weight per 100 parts by weight of cement, and the crushed fine aggregate may be about 180.47 parts by weight per 100 parts by weight of cement.

[0083] In addition, in a 20% weight reduction cement mix of a 35 MPa grade product, the coarse aggregate may be about 301.38 parts by weight per 100 parts by weight of cement, and the crushed fine aggregate may be about 282.83 parts by weight per 100 parts by weight of cement.

[0084] Accordingly, when coarse aggregate is included in an amount of 190 parts by weight or more and 305 parts by weight or less per 100 parts by weight of cement, and crushed fine aggregate is included in an amount of 180 parts by weight or more and 285 parts by weight or less per 100 parts by weight of cement, a concrete composition including both a standard mix and a cement reduction mix can be provided.

[0085] However, if the cement weight loss rate is 20 weight%, the 28-day compressive strength of the 35 MPa grade product and the 45 MPa grade product may fall short of their respective target compressive strengths.

[0086] Accordingly, in the present invention, the compressive strength required for concrete structures can be secured by controlling the content of saturated nanocellulose water dispersion, the cement reduction rate, and the additional amount of crushed fine aggregate within the aggregate content range.

[0087] Water is used to induce the hydration reaction of cement and to ensure the mixability and moldability of the concrete composition.

[0088] The water content can be adjusted according to the cement content, aggregate content, type of admixture, and the required strength of the concrete structure.

[0089] In one embodiment, the amount of water contained in the saturated nanocellulose water dispersion can be calculated as part of the mixing water of the concrete composition.

[0090] For example, if a saturated nanocellulose aqueous dispersion contains 20 parts by weight of solids and 80 parts by weight of water, about 80 parts by weight of the added aqueous dispersion may be calculated as mixing water and about 20 parts by weight as nanocellulose solids.

[0091] Therefore, the amount of water added can be adjusted to maintain the actual water-to-binder ratio (W / B) or effective water content of the concrete composition at a constant level.

[0092] Here, "Effective Water Content" may refer to the amount of free water that substantially contributes to the cement hydration reaction, workability, and fluidity formation within the concrete composition.

[0093] In the present invention, the retained moisture contained in the saturated nanocellulose water dispersion is calculated as part of the mixing water, thereby enabling the stable maintenance of the target effective water content or the target water-to-binder ratio. Consequently, variations in unit water content, slump fluctuations, and viscosity variations within the concrete composition can be reduced.

[0094] The moisture content of a saturated nanocellulose aqueous dispersion can be measured by a moisture content test based on dry weight or by moisture content analysis.

[0095] In one embodiment, the saturated nanocellulose aqueous dispersion may have a moisture content of 75% by weight or more and 85% by weight or less.

[0096] The concrete composition may be composed to further include an admixture.

[0097] It is preferable that the admixture be included in an amount of 0.8 parts by weight or more and 1.1 parts by weight or less per 100 parts by weight of cement.

[0098] Admixtures function to control the fluidity, susceptibility, moldability, or strength development of concrete compositions.

[0099] The admixture may include at least one of a water reducer, a high-performance water reducer, a fluidizing agent, an AE agent, a retardant, and an accelerator.

[0100] In one embodiment of the present invention, the saturated nanocellulose aqueous dispersion may be a saturated nanocellulose aqueous dispersion in which the water retention state is adjusted to suppress additional free water absorption by the cellulose nanofibers.

[0101] A saturated nanocellulose aqueous dispersion may be a gel-state aqueous dispersion composed of cellulose nanofibers (CNF, Cellulose Nanofiber or Cellulose Nanofibril) and water retained in the cellulose nanofibers (CNF).

[0102] In this specification, 'saturated' may mean that the cellulose nanofibers are adjusted to contain retained moisture so that they do not rapidly absorb additional free water during concrete mixing.

[0103] For example, a saturated nanocellulose aqueous dispersion can be adjusted to contain 10 to 30 parts by weight of cellulose nanofiber solids and 80 to 82 parts by weight of retained moisture per 100 parts by weight of the saturated nanocellulose aqueous dispersion.

[0104] More preferably, the saturated nanocellulose aqueous dispersion can be adjusted to contain 18 to 20 parts by weight of cellulose nanofiber solids and 80 to 82 parts by weight of retained moisture per 100 parts by weight of the saturated nanocellulose aqueous dispersion.

[0105] In this specification, 'moisture retained in cellulose nanofibers' may mean moisture retained on the surface, inside, or in the fibrous network between the cellulose nanofibers.

[0106] In this specification, 'gel state' may refer to a viscous or semi-solid state in which cellulose nanofibers (CNF) are extracted from a cellulose-based raw material and then not finally dried or powdered, so that the cellulose nanofibers (CNF) exist in a state in which they retain moisture.

[0107] Specifically, the gel-state saturated nanocellulose aqueous dispersion may be in a state where cellulose nanofibers (CNF) form a fibrous network or exhibit viscosity while retaining moisture. The saturated nanocellulose aqueous dispersion may be flowable under external force, but it can be distinguished from a simple low-viscosity aqueous solution or a liquid dilution.

[0108] In addition, the gel state in the present invention is not limited to a redispersed solution, diluted solution, or aqueous solution prepared by adding water to dry powdered nanocellulose. That is, a liquid dispersion prepared by adding dry powdered nanocellulose to water and then stirring, ultrasonic dispersion, high-pressure dispersion, or dilution treatment can be distinguished from the saturated nanocellulose aqueous dispersion of the present invention, in which cellulose nanofibers (CNF) exist in a state that retains moisture without being dried powdered after extraction.

[0109] In dry powdered nanocellulose, bonding or aggregation between cellulose nanofibers may occur during the drying process, and even if water is added to redisperse it, it may be difficult to restore it to the same dispersed state as the moisture-retaining gel state before drying. Additionally, dry powdered nanocellulose may swell or aggregate by locally absorbing moisture when in contact with the mixing water of a concrete composition.

[0110] On the other hand, the saturated nanocellulose water dispersion of the present invention can have its moisture retention state adjusted to suppress additional free water absorption during concrete mixing while maintaining the moisture retention state of the cellulose nanofibers (CNF) before they are dried and powdered. Accordingly, the phenomenon of localized aggregation caused by the rapid absorption of mixing water during the mixing process of the concrete composition can be reduced.

[0111] Accordingly, the saturated nanocellulose water dispersion can be dispersed within the concrete composition during the mixing process with cement, aggregate, and water without undergoing a separate dilution preparation process or a long-term dispersion process, and can suppress fluctuations in the effective water content during concrete mixing.

[0112] Furthermore, when powdered nanocellulose is added to a concrete composition, it can rapidly absorb free water the moment it comes into contact with the mixing water, which can cause localized fluctuations in the effective water content of the concrete composition. Such localized fluctuations in effective water content can lead to a decrease in slump, variations in air content, an increase in viscosity, and non-homogenization of the mixture, resulting in increased variation in compressive strength among test specimens.

[0113] On the other hand, since the saturated nanocellulose water dispersion of the present invention is adjusted so that the cellulose nanofibers contain retained moisture, additional free water absorption during the mixing of the concrete composition can be suppressed. Accordingly, when the saturated nanocellulose water dispersion of the present invention is applied, the reduction in slump, fluctuations in air content, increases in viscosity, and deviations in compressive strength can be reduced compared to when powdered nanocellulose is applied.

[0114] In this specification, the term 'gel state' does not simply mean that nanocellulose exists together with water. That is, a state in which nanocellulose powder is temporarily wetted by adding it to water, a state in which nanocellulose powder is diluted in water, or a state in which nanocellulose powder is prepared as a liquid dispersion by a separate dispersion process can be distinguished from the gel state of the present invention, in which cellulose nanofibers (CNF) exist in a viscous or semi-solid state that retains moisture without being dried into powder after extraction.

[0115] The aforementioned cellulose nanofiber (CNF) can be distinguished from cellulose nanocrystal (CNC).

[0116] Cellulose nanofibers (CNF) can be nanocellulose in which cellulose is micronized into a fibrous or fibrilous form.

[0117] Cellulose nanofibers (CNF) have a fibrous or fibrillary form and can form a gel state with moisture retained in the cellulose nanofibers (CNF).

[0118] On the other hand, cellulose nanocrystals (CNC) can be particulate or rod-shaped nanocellulose containing crystalline regions of cellulose.

[0119] Cellulose nanocrystals (CNCs) can generally be obtained by removing the amorphous regions of cellulose through acid hydrolysis or the like, and can have the characteristics of crystalline or rod-shaped particles rather than a fibrous network.

[0120] These cellulose nanofibers (CNF) can be dispersed between cement particles and aggregates based on their fibrous structure within a concrete composition.

[0121] Therefore, the saturated nanocellulose aqueous dispersion may not be a composition containing cellulose nanocrystal (CNC) powder, but may be a gel-state aqueous dispersion containing cellulose nanofibers (CNF) and moisture retained in the cellulose nanofibers (CNF).

[0122] In one embodiment of the present invention, the cellulose nanofiber (CNF) preferably has an average fiber diameter of 50 nm or more and less than 500 nm.

[0123] In the present invention, 'average fiber diameter' may refer to a value calculated by measuring the diameter or width of a plurality of cellulose nanofibers (CNF) observed in an electron microscope image and taking the arithmetic mean of the measured values.

[0124] However, cellulose nanofibers (CNF) and cellulose nanocrystals (CNC) are not distinguished solely by their average fiber diameter, but can be distinguished by considering their shape, crystallinity, manufacturing method, and whether they form a moisture-retaining gel.

[0125] A saturated nanocellulose aqueous dispersion may contain 10 to 30 parts by weight of cellulose nanofiber (CNF) solids (more preferably 18 to 20 parts by weight of cellulose nanofiber (CNF) solids) per 100 parts by weight of the saturated nanocellulose aqueous dispersion.

[0126] The remaining components may include retained moisture in the cellulose nanofiber (CNF), and in one embodiment, the retained moisture may be included in an amount of 80 parts by weight or more and 82 parts by weight or less per 100 parts by weight of the saturated nanocellulose aqueous dispersion.

[0127] The saturated nanocellulose aqueous dispersion may be in a water gel state. In one embodiment, the saturated nanocellulose aqueous dispersion may be an aqueous dispersion in a gel state that is disperseable in water rather than being completely dissolved in water.

[0128] It is preferable that the saturated nanocellulose water dispersion be composed of 0.8 parts by weight or more and 1.2 parts by weight or less per 100 parts by weight of cement.

[0129] If the saturated nanocellulose water dispersion is included in an amount of less than 0.8 parts by weight per 100 parts by weight of cement, the strength-enhancing effect due to the saturated nanocellulose water dispersion may not be sufficient.

[0130] If a saturated nanocellulose water dispersion is included in an amount exceeding 1.2 parts by weight per 100 parts by weight of cement, the uniformity of the mixture or the effect of improving strength of the concrete composition may be reduced due to the excessive incorporation of the saturated nanocellulose water dispersion.

[0131] Accordingly, in a range in which a saturated nanocellulose water dispersion is included in an amount of 0.8 parts by weight or more and 1.2 parts by weight or less per 100 parts by weight of cement, the concrete composition can stably exhibit an effect of improving compressive strength and a cement reduction effect.

[0132] In one embodiment, the saturated nanocellulose aqueous dispersion may have the following properties.

[0133] item detail Product form Saturated nanocellulose aqueous dispersion situation Water gel or viscous water dispersion in a gel state Main ingredients Cellulose and moisture retention Solids 10 parts by weight or more and 30 parts by weight or less moisture retention 80 parts by weight or more and 82 parts by weight or less pH 6.5 or higher, 7.5 or lower Behavior of water Insoluble or dispersible in water

[0134] Referring to [Table 1], the saturated nanocellulose aqueous dispersion may be provided in a gel state containing cellulose nanofibers (CNF) and retained moisture in the cellulose nanofibers (CNF).

[0135] Saturated nanocellulose aqueous dispersions are not limited to materials that are completely soluble in water, but can be gel-state aqueous dispersions that are dispersible in water.

[0136] [Table 1] is intended to explain one example of a saturated nanocellulose water dispersion, and the present invention is not limited to the physical property values ​​or items listed in [Table 1].

[0137] In one embodiment, a saturated nanocellulose aqueous dispersion can be manufactured or managed through pretreatment and process control procedures as shown in [Table 2] below.

[0138] Process / Control Items detail Technical meaning Washing and neutering Removal or reduction of residual acids, alkalis, salts, or ionic components in cellulose nanofibers Reduction of influence on cement hydration reaction and admixture action Moisture content adjustment and saturation Moisture state adjusted to have a solid content of 18 to 20 parts by weight and a retained moisture content of 80 to 82 parts by weight. Inhibition of additional free water absorption and stabilization of effective water quantity during mixing High shear dispersion It applies shear force to cellulose nanofibers within the retained moisture to dismantle aggregates. Uniformity of moisture within the gel, ensured mixability, and improved dispersibility within concrete Rheology adjustment Adjustment of viscosity, fluidity, yield stress, or dispersion stability Suppression of slump reduction, viscosity increase, and mold filling capacity reduction Mixing water correction Calculate the retained moisture content as part of the mixing water and correct the amount of external mixing water input. Maintain target water-to-binder ratio or effective water quantity PC Product Application Applied to mold insertion, curing, and demolding processes Improvement in early strength development, demolding stability, and quality homogeneity

[0139] [Table 3] below shows the difference between a saturated nanocellulose aqueous dispersion and a diluted nanocellulose dispersion.

[0140] division Saturated nanocellulose aqueous dispersion Diluted nanocellulose dispersion Manufacturing status Maintains moisture content without drying or pulverizing after extraction. Formed by diluting or redispersing in water Solids / Moisture 18 to 20 parts by weight of solids, 80 to 82 parts by weight of moisture retained May contain relatively low solid content or external dilution water. Behavior during mixing Reduces fluctuations in effective water quantity by suppressing additional free water absorption If not linked to the calculation of the mixing water, the effective water quantity may fluctuate. Mixing water management Correction of water input amount by calculating retained moisture as part of the mixing water Separate correction of diluted water and dispersed water may be required. Technical meaning Functional water dispersion for PC secondary product manufacturing process Dilution, grinding, or dispersion center for nanogel formation

[0141] As shown in [Table 3], the saturated nanocellulose water dispersion of the present invention is not simply a nanocellulose dispersion diluted in water, but may be a functional water dispersion in which the water content, solid content, and mixing water correction are controlled to suppress fluctuations in the effective water content during the manufacturing process of concrete secondary products.

[0142] Cellulose nanofibers (CNF) can be obtained from non-woody waste, woody waste, or recycled cellulose-based raw materials.

[0143] For example, cellulose nanofibers (CNF) can be obtained from sugarcane waste, acacia waste, or waste paper, but are not limited thereto.

[0144] division sugarcane waste (Bagasse) Acacia waste (Hard Wood) abolition (Waste Paper) Raw material type agricultural by-products woody Recycling cellulose 40~50% 45~55% 50~70% Hemicellulose 25~35% 20~30% 10~20% lignin 15~25% 20~30% 5~15% minerals 2~5% 2% or less 10~30% Extracts / Others 2~5% 2~5% Includes ink / additives Cellulose after CNF extraction 70~90% 85~95% 60~85% CNF crystallinity middle height Low to medium Structural uniformity lowness height Very low Possibility of impurity presence lowness Very low height Composition variability middle lowness Very high

[0145] [Table 4] shows the composition of sugarcane waste, acacia waste, and waste paper, and the characteristics of cellulose nanofibers (CNF) extracted from each raw material.

[0146] As shown in [Table 4], cellulose nanofibers (CNF) may vary in cellulose content, hemicellulose content, lignin content, inorganic content, crystallinity, structural uniformity, possibility of impurity presence, and compositional variability depending on the raw material.

[0147] For example, sugarcane waste is an agricultural byproduct and preferably contains 40% or more and 50% or less of cellulose, 25% or more and 35% or less of hemicellulose, 15% or more and 25% or less of lignin, 2% or more and 5% or less of inorganic matter, and 2% or more and 5% or less of extracts or other components.

[0148] Cellulose nanofibers (CNF) extracted from sugarcane waste may have a cellulose content of 70% or more and 90% or less after extraction, may have an intermediate level of crystallinity, and may have a low level of impurity presence.

[0149] Acacia waste is a lignocellulosic raw material that may have a relatively higher cellulose content and, compared to sugarcane waste, a higher cellulose content after CNF extraction, as well as higher crystallinity and structural uniformity. However, since acacia waste is a lignocellulosic raw material, it may differ from agricultural by-products in terms of raw material availability, processing, or economic feasibility.

[0150] While waste paper can have a high cellulose content as a recycled raw material, it may contain ink, additives, inorganic materials, or other impurities, and its compositional variability can be relatively high. Consequently, the variation in strength development of waste paper-derived cellulose nanofibers (CNF) within concrete compositions may increase depending on raw material supply conditions or the degree of pretreatment.

[0151] Therefore, even within the same cellulose nanofiber (CNF) series, the compressive strength, strength variation, and mix reproducibility of the concrete composition may vary depending on the type of raw material, the composition of the raw material, the cellulose content after extraction, whether the gel state is maintained, and the dispersion state within the concrete composition.

[0152] In one embodiment, cellulose nanofibers (CNF) may be extracted from non-woody agricultural by-products. In this case, the non-woody agricultural by-products may include sugarcane waste.

[0153] Sugarcane waste-derived cellulose nanofibers (CNF) have a relatively high hemicellulose content, which can provide hydrophilic and moisture-retaining properties, and when provided in a gel state, they can be advantageous for ensuring dispersibility within concrete compositions.

[0154] In addition, cellulose nanofibers (CNF) can be provided in a gel state containing moisture retained in the cellulose nanofibers (CNF) without undergoing a final drying and pulverization process after extraction from the raw material.

[0155] Accordingly, the phenomenon of cellulose nanofibers (CNF) rapidly absorbing moisture and aggregating upon contact with mixing water in a powder state can be reduced, and mixing dispersion can be ensured without adding a separate long-term dispersion process in the actual production process of concrete secondary products.

[0156] The action of the aforementioned gel-type nanocellulose will be explained in more detail below.

[0157] Conventional dried powdered nanocellulose has the advantage of being easy to store and transport, but due to its high water absorption, it can rapidly absorb moisture the moment it comes into contact with mixing water during the actual concrete mixing process.

[0158] In this case, the nanocellulose powder may swell locally or clump together to form aggregates before being sufficiently dispersed. In particular, if the powdered nanocellulose does not undergo a sufficient dispersion process, local absorption of mixing water, volume increase, and clumping due to surface tension may occur.

[0159] When such aggregates are formed, nanocellulose may not be uniformly distributed throughout the concrete composition but may become localized in certain areas. Consequently, while strength improvement may occur in areas where nanocellulose is relatively abundant, strength development may be lower in areas where it is insufficiently distributed. Therefore, even with the same mix design, variations in compressive strength among test specimens may increase.

[0160] On the other hand, the saturated nanocellulose water dispersion used in the concrete composition of the present invention is provided in a gel state in which cellulose nanofibers (CNF) contain retained moisture. Therefore, unlike dry powder or low-moisture nanocellulose, the phenomenon of swelling or aggregation can be reduced as the nanocellulose locally absorbs the mixing water the moment it comes into contact with the mixing water.

[0161] Accordingly, the saturated nanocellulose water dispersion can be dispersed within the concrete composition during the mixing process with cement, aggregate, and water without undergoing a separate dilution or long-term dispersion process, and can suppress fluctuations in the effective water content.

[0162] In addition, saturated nanocellulose water dispersions can be more uniformly dispersed between cement and aggregates within the concrete composition. As a result, the variation in strength of the concrete body can be reduced, and the development of compressive strength can be stabilized.

[0163] Cellulose nanofibers (CNFs) can be adsorbed onto the surface of cement particles or placed in the microspaces between them. Therefore, CNFs can promote the cement hydration reaction and contribute to the formation of hydration products and the densification of the microstructure. Through these actions, concrete compositions can exhibit an improvement in compressive strength even at low incorporation rates.

[0164] However, if an excessive amount of saturated nanocellulose water dispersion is incorporated, defects may be formed due to interactions or local aggregation between cellulose nanofibers (CNF), and as a result, the effect of improving compressive strength may be reduced. Therefore, in the present invention, by limiting the content of saturated nanocellulose water dispersion to 0.8 parts by weight or more and 1.2 parts by weight or less per 100 parts by weight of cement, it is possible to simultaneously secure improved compressive strength and uniformity of the mixture.

[0165] The concrete composition of the present invention described above can also be applied in the precast concrete manufacturing process, and stable initial strength and quality homogeneity can be secured even in the early demolding process after steam curing.

[0166] In particular, the stabilization of internal moisture distribution and hydration reactions within the concrete by saturated nanocellulose water dispersions can improve early-age strength development characteristics. Consequently, cracking, corner damage, or quality variations during demolding can be reduced.

[0167] The saturated nanocellulose water dispersion used in the concrete composition of the present invention can densify the internal pore structure of the concrete, thereby improving water tightness, sulfate resistance, and long-term durability.

[0168] In addition, by reducing micropores and moisture transport pathways within the concrete, resistance to salt damage, sulfate erosion, and freeze-thaw environments can be improved.

[0169] Therefore, a saturated nanocellulose water dispersion having the above characteristics can be effectively applied to structures requiring environmental resistance, such as precast concrete products for water supply and sewage systems, drainage pipes, manhole blocks, and waterway structures.

[0170] Method for manufacturing the concrete composition of the present invention

[0171] Hereinafter, a method for manufacturing a concrete composition of the present invention will be described with reference to FIG. 1.

[0172] Figure 1 is a flowchart illustrating a method for preparing a concrete composition using a saturated nanocellulose water dispersion of the present invention.

[0173] As illustrated in FIG. 1, the method for manufacturing a concrete composition of the present invention may comprise a preparation step (S10) of preparing a saturated nanocellulose water dispersion and a composition forming step (S20) of mixing the saturated nanocellulose water dispersion, cement, aggregate, and water to form a concrete composition.

[0174] First, the preparation step (S10) is performed.

[0175] In the preparation step (S10), a process of preparing a saturated nanocellulose aqueous dispersion is performed.

[0176] The saturated nanocellulose aqueous dispersion may be a gel-state aqueous dispersion containing cellulose nanofibers (CNF) and retained moisture in the cellulose nanofibers (CNF).

[0177] In one embodiment, a saturated nanocellulose aqueous dispersion may be prepared by extracting cellulose nanofibers (CNF) from a cellulose-based raw material and then not drying and pulverizing the cellulose nanofibers (CNF).

[0178] That is, in the present invention, instead of drying the cellulose nanofiber (CNF) to process it into a powder form and then redispersing it in water, a saturated nanocellulose water dispersion can be prepared by allowing the cellulose nanofiber (CNF) to maintain a gel state containing retained moisture.

[0179] Such a saturated nanocellulose aqueous dispersion can be distinguished from a liquid dispersion or a low-concentration dilution obtained by adding water to dry powdered nanocellulose and redispersing it.

[0180] The preparation step (S10) may be configured to include a washing and neutralization step (S11) for removing residual ions from cellulose nanofibers (CNF) extracted from a cellulose-based raw material, a water content adjustment and saturation step (S12) for adjusting the water retention state of the cellulose nanofibers (CNF), a high-shear dispersion step (S13) for applying shear force to the cellulose nanofibers (CNF), and a rheology adjustment step (S14) for adjusting the viscosity, fluidity, yield stress, or dispersion stability of the saturated nanocellulose water dispersion.

[0181] First, in the washing and neutralization step (S11), a process is performed to remove residual ions of the cellulose nanofiber (CNF) extracted from the cellulose-based raw material.

[0182] In the washing and neutralization step (S11), alkaline components, acid components, salt components, or ionic components that may remain in the cellulose nanofibers (CNF) extracted from the cellulose-based raw material are removed or reduced.

[0183] Therefore, when a saturated nanocellulose water dispersion is incorporated into a concrete composition, it can reduce the effect on the cement hydration reaction or the action of the admixture.

[0184] After the washing and neutralization step (S11) is completed, the moisture content adjustment and saturation step (S12) is performed.

[0185] In the moisture content adjustment and saturation step (S12), a process for adjusting the moisture retention state of the cellulose nanofiber (CNF) is performed.

[0186] In the moisture content adjustment and saturation step (S12), the moisture retention state of the cellulose nanofibers (CNF) can be adjusted so that the cellulose nanofibers (CNF) do not rapidly absorb additional free water during the mixing of the concrete composition.

[0187] In one embodiment, the saturated nanocellulose aqueous dispersion may contain 10 to 30 parts by weight of cellulose nanofiber solids and 70 to 90 parts by weight of retained water, based on 100 parts by weight of the saturated nanocellulose aqueous dispersion. More preferably, the saturated nanocellulose aqueous dispersion may contain 18 to 20 parts by weight of cellulose nanofiber solids and 80 to 82 parts by weight of retained water.

[0188] As described above, by adjusting the moisture retention state of the cellulose nanofiber (CNF), the cellulose nanofiber (CNF) can be adjusted to a moisture retention state that suppresses additional free water absorption during the mixing of the concrete composition.

[0189] When the moisture content adjustment and saturation step (S12) is completed, the high-shear dispersion step (S13) is performed.

[0190] In the high-shear dispersion step (S13), a process of applying shear force to the cellulose nanofiber (CNF) is performed.

[0191] In the high-shear dispersion step (S13), shear force can be applied so that the cellulose nanofibers (CNF) are dispersed within the retained moisture.

[0192] As described above, as shear force is applied, aggregates of cellulose nanofibers (CNF) can be disassembled or reduced, and cellulose nanofibers (CNF) can form a more homogeneous gel network within the retained moisture.

[0193] Therefore, through the high-shear dispersion step (S13), the cellulose nanofibers (CNF) can be reduced from existing in a locally aggregated state and adjusted to a state where they can be dispersed between cement particles and aggregates within the concrete composition.

[0194] When the high-shear dispersion step (S13) is completed, the rheology adjustment step (S14) is performed.

[0195] In the rheology adjustment step (S14), a process is performed to control the viscosity, fluidity, yield stress, or dispersion stability of the saturated nanocellulose water dispersion.

[0196] The rheological stability implemented by the rheology adjustment step (S14) may mean a characteristic in which the slump, viscosity, fluidity, and mixing homogeneity of the concrete mixture are stably maintained.

[0197] In one embodiment, the viscosity of the saturated nanocellulose aqueous dispersion can be adjusted to 32,000 cP or more and 38,000 cP or less by the rheology adjustment step (S14). More preferably, the viscosity of the saturated nanocellulose aqueous dispersion can be adjusted to about 35,000 cP.

[0198] In addition, through the rheology adjustment step (S14), the saturated nanocellulose aqueous dispersion can be endowed with shear thinning properties.

[0199] Through the above process, when a saturated nanocellulose water dispersion is incorporated into a concrete composition, the reduction in slump, increase in viscosity, non-uniformity of mixing, or decrease in mold filling ability can be reduced.

[0200] A saturated nanocellulose water dispersion is a water dispersion in which the water retention state is adjusted to suppress additional free water absorption by cellulose nanofibers (CNF), and the water retention contained in the saturated nanocellulose water dispersion can be calculated as part of the mixing water of the concrete composition.

[0201] Therefore, when manufacturing a concrete composition, the amount of water added separately can be reduced based on the amount of water retained in the saturated nanocellulose water dispersion to maintain the target water-to-binder ratio or effective water amount.

[0202] In one embodiment, the saturated nanocellulose water dispersion may be designed to have a moisture retention state adjusted to suppress additional free water absorption by cellulose nanofibers (CNF) and to contain internally retained moisture of 80 parts by weight or more and 82 parts by weight or less. In this case, the saturated nanocellulose water dispersion can reduce fluctuations in the effective water content during the mixing of the concrete composition.

[0203] In addition, in one embodiment, the concrete composition to which the saturated nanocellulose water dispersion is applied may have a free water loss rate of 3.6% or more and 4.2% or less, and more preferably about 3.9%. However, the above free water loss rate is a value measured under test conditions according to one embodiment, and the present invention is not limited thereto.

[0204] In the case of conventional gel-type nanocellulose compositions, if the internal moisture of the gel is not accounted for as the total mixing water of the concrete composition, the actual water-to-binder ratio may increase and the strength may decrease.

[0205] However, the saturated nanocellulose water dispersion used in the present invention can calculate the moisture retained within the saturated nanocellulose water dispersion as part of the total mixing water of the concrete composition and correct the amount of water added based on this.

[0206] In other words, in the present invention, the amount of the saturated nanocellulose water dispersion introduced can be calculated by separating it into the amount of solid cellulose nanofibers and the amount of water mixed, thereby reducing the problem of increased water-to-binder ratio that may occur when using conventional gel-type or diluted nanocellulose dispersions. Accordingly, mold filling ability, early strength development, curing stability, and demolding stability can be improved in the manufacturing process of precast concrete products.

[0207] In addition, the saturated nanocellulose water dispersion is adjusted to have shear thinning characteristics, so that when the saturated nanocellulose water dispersion is incorporated into a concrete composition, it can reduce slump reduction, viscosity increase, mixing inhomogeneity, or mold filling ability.

[0208] As described above, when a saturated nanocellulose aqueous dispersion is prepared and the preparation step (S10) is completed, the composition formation step (S20) is performed.

[0209] In the composition formation step (S20), a process is performed to form a concrete composition by mixing a saturated nanocellulose water dispersion, cement, aggregate, and water.

[0210] Here, "saturated nanocellulose water dispersion" may refer to a water dispersion in which the water absorption capacity of cellulose nanofibers (CNF) is pre-filled, thereby substantially suppressing the rapid absorption of additional free water during the concrete mixing process.

[0211] The saturation process of the present invention is not a simple water addition or dilution process, but may be a process for suppressing fluctuations in the effective water content during concrete mixing and ensuring mix stability.

[0212] The moisture content of saturated nanocellulose water dispersions can be adjusted to suppress rapid fluctuations in the effective water-to-binder ratio (W / B) during concrete mixing.

[0213] This saturation process may not be a simple concentration process, but rather an effective quantity stabilization process.

[0214] The composition formation step (S20) may be configured to include a mixing water calculation step (S21) for calculating the amount of water retained in a saturated nanocellulose water dispersion as part of the mixing water of the concrete composition, an external mixing water input amount correction step (S22) for correcting the amount of external mixing water input based on the calculated amount of water retained, and a mixing step (S23) for mixing the saturated nanocellulose water dispersion, cement, aggregate, and the corrected external mixing water.

[0215] First, in the mixing water calculation step (S21), a process is performed to calculate the amount of water retained in the saturated nanocellulose water dispersion as part of the mixing water of the concrete composition.

[0216] In this case, the retained moisture content can be calculated based on the input amount of the saturated nanocellulose aqueous dispersion and the ratio of retained moisture contained in the saturated nanocellulose aqueous dispersion.

[0217] For example, when a saturated nanocellulose water dispersion contains 20 parts by weight of cellulose nanofiber solids and 80 parts by weight of retained water, about 80% of the input amount of the saturated nanocellulose water dispersion can be calculated as part of the mixing water of the concrete composition.

[0218] The amount of water retained in the saturated nanocellulose water dispersion can be calculated as part of the total mixing water of the concrete composition, and accordingly, the amount of externally added water can be adjusted.

[0219] This allows the actual effective water-to-binder ratio (W / B) of the concrete mix to be maintained stably.

[0220] In addition, by adjusting the mixing water, it is possible to reduce slump, increase viscosity, and suppress mixing inhomogeneity and compressive strength variations.

[0221] As described above, by calculating the input saturated nanocellulose water dispersion by separating it into the cellulose nanofiber solid content and the mixing water content, the effective water content of the concrete composition can be stably managed and the deviation in unit water content can be reduced.

[0222] In one embodiment, when the mixing water correction is not applied, the deviation in unit water quantity may be approximately ±11 kg / m³, whereas, as in the present invention, when approximately 80 weight% of the water retained in the amount of saturated nanocellulose water dispersion is calculated as part of the mixing water and the amount of external mixing water input is corrected based on this, the deviation in unit water quantity may be reduced to approximately ±6 kg / m³.

[0223] In addition, in one embodiment, the standard deviation of the water-to-binder ratio deviation can be reduced from 0.011 to 0.006. Thus, the present invention can maintain the target water-to-binder ratio while applying a saturated nanocellulose water dispersion and can exhibit the effect of reducing quality deviation between batches.

[0224] In one embodiment, the retained moisture contained in the saturated nanocellulose water dispersion can be calculated as part of the mixing water of the concrete composition. In this case, the amount of retained moisture is calculated based on the input amount of the saturated nanocellulose water dispersion and the ratio of retained moisture, and the input amount of external mixing water can be reduced or corrected by the calculated amount of retained moisture. Accordingly, even when the saturated nanocellulose water dispersion is incorporated into the concrete composition, the target water-to-binder ratio or the target effective water amount can be maintained.

[0225] In one embodiment, 70% to 90% by weight of the retained moisture among the input amount of the saturated nanocellulose water dispersion may be calculated as part of the mixing water of the concrete composition. More preferably, 80% to 82% by weight of the retained moisture among the input amount of the saturated nanocellulose water dispersion may be calculated as part of the mixing water of the concrete composition.

[0226] As described above, when the mixing water calculation step (S21) is completed, the external mixing water input amount correction step (S22) is performed.

[0227] In the external mixing water input amount correction step (S22), a process of correcting the external mixing water input amount based on the calculated retained moisture amount is performed.

[0228] In the external mixing water input amount correction step (S22), in order to maintain the target water-to-binder ratio or target effective water amount of the concrete composition, the amount of water separately added is reduced by the amount of water retained in the saturated nanocellulose water dispersion.

[0229] Therefore, it is possible to prevent the retained moisture contained in the saturated nanocellulose water dispersion from being double-counted with external mixing water, and to stably maintain the target water-to-binder ratio or effective water quantity of the concrete composition.

[0230] As described above, after the external mixing water input amount correction step (S22) is completed, the mixing step (S23) is performed.

[0231] In the mixing step (S23), a process of mixing a saturated nanocellulose water dispersion, cement, aggregate, and corrected external mixing water is performed.

[0232] In one embodiment, during the composition formation step, the saturated nanocellulose water dispersion may be mixed with cement, aggregate, and water while maintaining a gel state, without being prepared as a separate low-concentration diluent or nanocellulose dispersion.

[0233] In this case, the saturated nanocellulose water dispersion is not prepared as a separate low-concentration dispersion by separate ultrasonic dispersion, magnetic stirring, high-pressure dispersion, or long-term stirring and then added, but can be mixed with cement, aggregate, and water as a gel-state water dispersion.

[0234] In conventional laboratory-scale nanocellulose application tests, nanocellulose was sometimes stirred in water for a long time, treated with ultrasound, or sufficiently dispersed using a vacuum mixer to produce pastes, mortars, or small test specimens. However, in the actual production process of concrete secondary products, large quantities of cement, aggregates, and water are mixed within a limited time, making it difficult to apply these laboratory-scale dispersion conditions directly.

[0235] On the other hand, according to the method for manufacturing a concrete composition of the present invention, a saturated nanocellulose water dispersion can be mixed with cement, aggregate, and water without being prepared as a separate low-concentration diluent or nanocellulose dispersion. Therefore, the method for manufacturing a concrete composition of the present invention can be applied to the actual production process of precast concrete structures, and the dispersibility of nanocellulose and the reproducibility of strength development can be ensured without adding a separate long-duration dispersion process.

[0236] As described above, a concrete composition can be formed by mixing a saturated nanocellulose water dispersion, cement, aggregate, and corrected external mixing water in the mixing step (S23).

[0237] In the composition formation step (S20), it is preferable that the saturated nanocellulose water dispersion be mixed in an amount of 0.8 parts by weight or more and 1.2 parts by weight or less per 100 parts by weight of cement.

[0238] If the saturated nanocellulose water dispersion is mixed in an amount of less than 0.8 parts by weight per 100 parts by weight of cement, the strength-enhancing effect of the saturated nanocellulose water dispersion may not be sufficient.

[0239] When a saturated nanocellulose water dispersion is mixed in an amount exceeding 1.2 parts by weight per 100 parts by weight of cement, the uniformity of the mixture or the effect of improving strength of the concrete composition may be reduced due to the excessive incorporation of the saturated nanocellulose water dispersion.

[0240] Additionally, in the composition forming step (S20), the aggregate may be composed of coarse aggregate and crushed fine aggregate.

[0241] In this case, it is preferable that the coarse aggregate be mixed in an amount of 190 parts by weight or more and 305 parts by weight or less per 100 parts by weight of cement, and that the crushed fine aggregate be mixed in an amount of 180 parts by weight or more and 285 parts by weight or less per 100 parts by weight of cement.

[0242] In one embodiment, in the composition forming step (S20), cement with a reduced content compared to the standard cement content may be used, and a concrete composition may be formed by adding crushed fine aggregate with a weight corresponding to the difference between the standard cement content and the reduced cement content.

[0243] In this case, the reduced cement content may be 12% by weight or more and 18% by weight or less compared to the cement content of the standard mix.

[0244] As described above, when a concrete composition is formed by mixing a saturated nanocellulose water dispersion, cement, aggregate, and water, the composition formation step (S20) is completed.

[0245] A concrete composition produced by the aforementioned manufacturing method can be poured into a mold or die and cured to form a concrete structure.

[0246] The main technical significance of using a saturated nanocellulose water dispersion in the present invention is not simply to increase compressive strength by adding nanocellulose to a concrete composition.

[0247] The saturated nanocellulose water dispersion of the present invention is adjusted so that the cellulose nanofibers contain retained moisture, thereby suppressing additional free water absorption during the mixing of the concrete composition.

[0248] In addition, since the retained moisture contained in the saturated nanocellulose water dispersion can be calculated as part of the mixing water of the concrete composition, the target water-to-binder ratio or effective water amount can be maintained by correcting the amount of externally added water.

[0249] Accordingly, the present invention is characterized by the main technical feature of stabilizing the effective water content, rheological properties, slump, air content, and viscosity of a concrete composition using a saturated nanocellulose water dispersion, and ensuring mix reproducibility, production stability, and quality homogeneity in the actual precast concrete secondary product production process.

[0250] The concrete composition produced by the method for producing a concrete composition according to the present invention is not merely a simple nanocellulose-added concrete, but rather relates to a precast concrete manufacturing technology that manages the effective water content, rheology, and production stability of the concrete manufacturing process by controlling the water content, dispersion state, and retained moisture of a saturated nanocellulose water dispersion.

[0251] The saturated nanocellulose water dispersion used in the method for manufacturing the concrete composition of the present invention can improve the reproducibility of the production process and quality homogeneity by reducing fluctuations in the effective water content and viscosity deviations during mixing. Accordingly, it can reduce slump fluctuations, mixing heterogeneity, reduced mold filling ability, or quality deviations between production batches.

[0252] Concrete structure of the present invention

[0253] The concrete structure of the present invention will be described below.

[0254] In one embodiment, the concrete structure can be manufactured through a steam curing process.

[0255] Saturated nanocellulose aqueous dispersions can stabilize internal moisture movement during the steam curing process, thereby reducing deviations in the initial hydration reaction.

[0256] Accordingly, it is possible to secure early demolding strength, improve demolding stability, and enhance quality homogeneity between products.

[0257] The concrete structure of the present invention may be composed of a concrete body.

[0258] The concrete body can be formed by curing the aforementioned concrete composition after it is poured into a mold or die.

[0259] A mold or die may have an internal space corresponding to the shape of the concrete structure to be manufactured.

[0260] The concrete composition can be cured after being poured into the internal space of a mold or die.

[0261] The concrete structure can be a precast concrete structure.

[0262] Precast concrete structures can be manufactured in a factory, transported to the site, and installed.

[0263] The concrete structure may be a water pipe series product or a manhole series product.

[0264] In one embodiment, the concrete structure may be a water pipe series product corresponding to a reinforced concrete flume or bench flume according to KS F 4010, and the concrete body may have a 28-day compressive strength of 35 MPa or more according to product specifications or design standards.

[0265] In another embodiment, the concrete structure may be a manhole series product corresponding to a concrete manhole block for sewage according to KS F 4012, and the concrete body may have a 28-day compressive strength of 45 MPa or more according to product specifications or design standards.

[0266] In one embodiment, the 28-day compressive strength can be measured by the compressive strength test method for concrete according to KS F 2405.

[0267] The concrete structure of the present invention can have improved watertightness, sulfate resistance, and long-term durability through densification of the pore structure.

[0268] Test example

[0269] Hereinafter, with reference to FIGS. 2 to 4, a test example for confirming the effect of the concrete composition according to the present invention will be described.

[0270] However, the following test examples are intended to illustrate the effects of the present invention, and the scope of the present invention is not limited thereto.

[0271] This test example was not a laboratory-scale paste test, but was conducted by simulating actual precast concrete product production line conditions or using actual production facilities.

[0272] Figure 2 is a graph showing the change in compressive strength according to the content of the saturated nanocellulose water dispersion of the concrete composition of the present invention, Figure 3 is a graph showing the change in compressive strength according to the cement reduction rate of the concrete composition of the present invention, and Figure 4 is a graph comparing the deviation in compressive strength between the concrete composition of the present invention with the saturated nanocellulose water dispersion and a control group with powdered nanocellulose.

[0273] In this test example, in order to verify whether saturated nanocellulose water dispersions can ensure mix reproducibility and quality homogeneity in the actual precast concrete secondary product production process, the 28-day compressive strength and the variation in compressive strength among specimens were evaluated according to the content of saturated nanocellulose water dispersions, cement loss rate, and nanocellulose type.

[0274] In addition, in this test example, the 28-day compressive strength according to the content of saturated nanocellulose water dispersion, cement loss rate, and type of nanocellulose was evaluated based on a 35 MPa grade mix designed for a water pipe series corresponding to reinforced concrete plumes and bench plumes according to KS F 4010, and a 45 MPa grade mix designed for a manhole series corresponding to concrete manhole blocks for sewage according to KS F 4012.

[0275] In the following tables, unless otherwise specifically stated, the mixing amount of each component is expressed in weight per 1 m³ (kg / m³), and the weight part is expressed as a value converted based on 100 weight parts of cement. In addition, in the following tables, "compressive strength" refers to the compressive strength measured at 28 days of age.

[0276] The saturated nanocellulose water dispersion used in this test example is a gel-state water dispersion containing cellulose nanofibers (CNF) and moisture retained in the cellulose nanofibers (CNF), and was incorporated into a concrete composition at a relative content to 100 parts by weight of cement.

[0277] In addition, the amount of water contained in the saturated nanocellulose water dispersion can be considered as part of the mixing water of the concrete composition, and accordingly, the amount of water added can be adjusted so that the effective water amount of the concrete mixture is maintained at a constant level.

[0278] The standard formulation and evaluation conditions are described below.

[0279] First, a standard formulation was prepared that does not contain saturated nanocellulose water dispersions.

[0280] The standard mix for a 35 MPa grade product contained 962 kg of coarse aggregate, 823 kg of crushed fine aggregate, 399 kg of cement, and 3.19 kg of admixture per 1 m³.

[0281] The standard mix for a 45 MPa grade product contained 921 kg of coarse aggregate, 841 kg of crushed fine aggregate, 466 kg of cement, and 3.73 kg of admixture per 1 m³.

[0282] As a result of measuring the 28-day compressive strength of the standard mix, the average compressive strength of the standard mix for 35 MPa grade products was 35.738 MPa, and the average compressive strength of the standard mix for 45 MPa grade products was 45.600 MPa.

[0283] Table 5 below shows the standard mixing volume per 1 m³ of the standard mix and the converted value based on 100 parts by weight of cement.

[0284] division Cement kg / ㎥ Coarse aggregate kg / ㎥ Coarse aggregate weight portion Crushed fine aggregate kg / ㎥ Weight of crushed fine aggregate Admixture kg / ㎥ Weight of admixture Compressive strength 35 MPa grade product 399.00 962.00 241.10 823.00 206.27 3.19 0.80 35.738 MPa 45 MPa grade product 466.00 921.00 197.64 841.00 180.47 3.73 0.80 45,600 MPa

[0285] In [Table 5], the weight parts were calculated by the following [Equation 1].

[0286] [Equation 1]

[0287] Part by weight of each component = kg / ㎥ of each component ÷ kg / ㎥ of cement × 100

[0288] The standard mix of [Table 5] was used as a comparison standard for the evaluation by saturated nanocellulose water dispersion content and the evaluation by cement reduction rate described later.

[0289] The following describes the evaluation of compressive strength according to the content of saturated nanocellulose water dispersions.

[0290] To determine the appropriate incorporation range of saturated nanocellulose water dispersion, the 28-day compressive strength was evaluated while varying the content of saturated nanocellulose water dispersion.

[0291] Specifically, saturated nanocellulose water dispersions were incorporated in amounts of 0.2 parts by weight, 0.4 parts by weight, 0.6 parts by weight, 0.8 parts by weight, 1.0 parts by weight, 1.2 parts by weight, and 1.4 parts by weight, respectively, with respect to 100 parts by weight of cement.

[0292] The saturated nanocellulose aqueous dispersion was prepared as a gel-state saturated aqueous dispersion containing water retained in cellulose nanofibers and cellulose nanofibers (CNF).

[0293] [Table 6] below shows the input amount and 28-day compressive strength of saturated nanocellulose water dispersion according to content.

[0294] Water dispersion amount 35 MPa-class NC input amount 35 MPa compressive strength 45 MPa-class NC input amount 45 MPa compressive strength 0 parts by weight 0.000 kg / ㎥ 35.738 MPa 0.000 kg / ㎥ 45,600 MPa 0.2 parts by weight 0.798 kg / ㎥ 37.320 MPa 0.932 kg / ㎥ 47.518 MPa 0.4 parts by weight 1.596 kg / ㎥ 39.468 MPa 1.864 kg / ㎥ 48.614 MPa 0.6 parts by weight 2.394 kg / ㎥ 40.178 MPa 2.796 kg / ㎥ 50.180 MPa 0.8 parts by weight 3.192 kg / ㎥ 41.848 MPa 3.728 kg / ㎥ 52.440 MPa 1.0 parts by weight 3.990 kg / ㎥ 42.792 MPa 4.660 kg / ㎥ 54.018 MPa 1.2 parts by weight 4.788 kg / ㎥ 40.498 MPa 5.592 kg / ㎥ 51.814 MPa 1.4 parts by weight 5.586 kg / ㎥ 38.926 MPa 6.524 kg / ㎥ 50.438 MPa

[0295] Referring to [Table 6] and Figure 2, when a saturated nanocellulose water dispersion is included in an amount of 0.8 parts by weight or more and 1.2 parts by weight or less per 100 parts by weight of cement, both the 35 MPa grade product and the 45 MPa grade product showed superior 28-day compressive strength compared to the standard mix.

[0296] In particular, for the 35 MPa grade product, compressive strengths of 41.848 MPa, 42.792 MPa, and 40.498 MPa were observed at 0.8 parts by weight, 1.0 parts by weight, and 1.2 parts by weight, respectively.

[0297] In addition, for the 45 MPa grade product, compressive strengths of 52.440 MPa, 54.018 MPa, and 51.814 MPa were observed at 0.8 parts by weight, 1.0 parts by weight, and 1.2 parts by weight, respectively.

[0298] On the other hand, when the content of the saturated nanocellulose water dispersion was 1.4 parts by weight, the compressive strength of the 35 MPa grade product decreased to 38.926 MPa, and the compressive strength of the 45 MPa grade product decreased to 50.438 MPa.

[0299] Therefore, the range of 0.8 parts by weight or more and 1.2 parts by weight or less is not merely an arbitrary range of choice, but can be understood as an effective range that can reliably secure the effects of improving compressive strength and reducing cement weight.

[0300] When a saturated nanocellulose water dispersion is included at 1.0 weight part per 100 weight parts of cement, the increase rate in compressive strength compared to the standard mix of a 35 MPa grade product is as shown in [Equation 2] below.

[0301] [Equation 2]

[0302] (42.792 - 35.738) / 35.738 × 100 = approximately 19.74%

[0303] In addition, the increase rate in compressive strength compared to the standard mix of a 45 MPa grade product is as shown in [Equation 3] below.

[0304] [Equation 3]

[0305] (54.018 - 45.600) / 45.600 × 100 = approx. 18.46%

[0306] The above results demonstrate that saturated nanocellulose water dispersions can exhibit an effect of improving compressive strength even at low incorporation amounts.

[0307] The following describes the evaluation of cement reduction and crushed fine aggregate correction mix designs.

[0308] To confirm the possibility of reducing cement content using a saturated nanocellulose water dispersion, a saturated nanocellulose water dispersion was included at a weight of 1.0 part per 100 parts by weight of cement, and the cement content was reduced compared to the standard mix.

[0309] At this time, the concrete composition was adjusted by reducing the cement content compared to the standard mix and adding crushed fine aggregate equivalent to the reduced weight of the cement.

[0310] For example, when reducing the cement by 18 weight percent in a 35 MPa grade product, 71.82 kg / m³ of the cement in the standard mix (399 kg / m³) was reduced to adjust the cement content to 327.18 kg / m³, and 71.82 kg / m³ of crushed fine aggregate corresponding to the reduced cement weight was added to the existing crushed fine aggregate (823 kg / m³) to adjust the crushed fine aggregate content to 894.82 kg / m³.

[0311] [Table 7] below shows the mixing ratios by cement weight loss rate, converted values ​​based on 100 parts by weight of cement, and 28-day compressive strength for 35 MPa grade products.

[0312] Cement weight loss rate Cement kg / ㎥ Coarse aggregate kg / ㎥ Coarse aggregate weight portion Crushed fine aggregate kg / ㎥ Weight of crushed fine aggregate Admixture kg / ㎥ Weight of admixture Compressive strength 0% 399.00 962.00 241.10 823.00 206.27 3.19 0.80 42.792 MPa 12% 351.12 962.00 273.98 870.88 248.03 3.19 0.91 41.792 MPa 14% 343.14 962.00 280.35 878.86 256.12 3.19 0.93 39.962 MPa 16% 335.16 962.00 287.03 886.84 264.60 3.19 0.95 38.078 MPa 18% 327.18 962.00 294.03 894.82 273.49 3.19 0.97 36.418 MPa 20% 319.20 962.00 301.38 902.80 282.83 3.19 1.00 33.920 MPa

[0313] Table 8 below shows the mixing ratios, converted values ​​based on 100 parts by weight of cement, and 28-day compressive strength for 45 MPa grade products according to cement weight loss rate.

[0314] Cement weight loss rate Cement kg / ㎥ Coarse aggregate kg / ㎥ Coarse aggregate weight portion Crushed fine aggregate kg / ㎥ Weight of crushed fine aggregate Admixture kg / ㎥ Weight of admixture Compressive strength 0% 466.00 921.00 197.64 841.00 180.47 3.73 0.80 54.018 MPa 12% 410.08 921.00 224.59 896.92 218.72 3.73 0.91 50.014 MPa 14% 400.76 921.00 229.81 906.24 226.13 3.73 0.93 49.128 MPa 16% 391.44 921.00 235.29 915.56 233.90 3.73 0.95 48.280 MPa 18% 382.12 921.00 241.02 924.88 242.04 3.73 0.98 46.072 MPa 20% 372.80 921.00 247.05 934.20 250.59 3.73 1.00 43,330 MPa

[0315] In [Table 7] and [Table 8], a cement reduction rate of 0% means a mixture in which saturated nanocellulose water dispersion is incorporated at a rate of 1.0 part by weight per 100 parts by weight of cement, without reducing the cement compared to the standard mixture.

[0316] Referring to [Table 7], [Table 8] and Figure 3, when a saturated nanocellulose water dispersion was included at 1.0 weight part per 100 weight parts of cement, the target compressive strength of the 35 MPa grade product and the 45 MPa grade product was satisfied even when the cement content was reduced by 18 weight%.

[0317] Specifically, under the condition of 18 weight% cement weight loss, the 28-day compressive strength of the 35 MPa grade product was 36.418 MPa, and the 28-day compressive strength of the 45 MPa grade product was 46.072 MPa.

[0318] On the other hand, under the condition of a 20 wt% reduction in cement weight, the 28-day compressive strength of the 35 MPa grade product was 33.920 MPa and the 28-day compressive strength of the 45 MPa grade product was 43.330 MPa, which fell short of each target compressive strength.

[0319] In addition, in the cement reduction range of 12% by weight or more and 18% by weight or less, coarse aggregate is included in an amount of about 224.59% by weight to about 294.03% by weight per 100% by weight of cement, crushed fine aggregate is included in an amount of about 218.72% by weight to about 273.49% by weight per 100% by weight of cement, and admixture is included in an amount of about 0.91% by weight to about 0.98% by weight per 100% by weight of cement.

[0320] Accordingly, in the standard mix and cement reduction mix, coarse aggregate may be included in an amount of about 197.64 to about 301.38 parts by weight per 100 parts by weight of cement, and crushed fine aggregate may be included in an amount of about 180.47 to about 282.83 parts by weight per 100 parts by weight of cement. These experimental values ​​correspond to a range of 190 parts by weight or more and 305 parts by weight or less for coarse aggregate and 180 parts by weight or more and 285 parts by weight or less for crushed fine aggregate.

[0321] In addition, in the standard mix and cement reduction mix, the admixture may be included in an amount of about 0.80 parts by weight to about 1.00 parts by weight per 100 parts by weight of cement. These experimental values ​​correspond to a range of 0.8 parts by weight or more and 1.1 parts by weight or less of the admixture.

[0322] Therefore, experimental results confirmed that by including a saturated nanocellulose water dispersion at 1.0 weight part per 100 weight parts of cement, reducing the cement by 12 weight% or more and 18 weight% or less compared to the standard mix, and adding crushed fine aggregate with a weight corresponding to the reduced cement weight, the amount of cement used can be reduced while satisfying the target compressive strength.

[0323] The following describes the evaluation of strength deviations according to nanocellulose type.

[0324] To determine the variation in strength according to the type of nanocellulose, nanocellulose derived from the same raw material was applied in gel and powder forms, respectively, and the 28-day compressive strength of each specimen was compared.

[0325] The content of the saturated nanocellulose water dispersion was set to 1.0 part by weight per 100 parts by weight of cement, and the results are as shown in [Table 9] below.

[0326] [Table 9] shows a comparison of compressive strengths for gel type and powder type specimens.

[0327] division Test specimen 1 Test specimen 2 Test specimen 3 Test specimen 4 Test specimen 5 average 35 MPa Gel Type 42.51 MPa 42.92 MPa 43.08 MPa 42.87 MPa 42.58 MPa 42.792 MPa 35 MPa Grade Powder Type 44.93 MPa 36.78 MPa 47.17 MPa 36.98 MPa 37.46 MPa 40.667 MPa 45 MPa Gel Type 54.27 MPa 53.87 MPa 54.30 MPa 54.18 MPa 53.47 MPa 54.018 MPa 45 MPa Grade Powder Type 57.36 MPa 46.17 MPa 59.46 MPa 45.66 MPa 48.46 MPa 51.421 MPa

[0328] In addition, the deviations of the maximum and minimum values ​​from the results of [Table 9] are calculated as shown in [Table 10] below.

[0329] [Table 10] shows a comparison of strength deviations between gel type and powder type.

[0330] division average maximum value minimum value Maximum-minimum deviation 35 MPa Gel Type 42.792 MPa 43.08 MPa 42.51 MPa 0.57 MPa 35 MPa Grade Powder Type 40.667 MPa 47.17 MPa 36.78 MPa 10.39 MPa 45 MPa Gel Type 54.018 MPa 54.30 MPa 53.47 MPa 0.83 MPa 45 MPa Grade Powder Type 51.421 MPa 59.46 MPa 45.66 MPa 13.80 MPa

[0331] Referring to [Table 9], [Table 10] and Figure 4, when gel-type nanocellulose was applied, the variation in compressive strength among test specimens was small and the average compressive strength was high.

[0332] On the other hand, when powder-type nanocellulose was applied, some specimens exhibited high strength while others showed low strength, resulting in significant variation between specimens.

[0333] For the 35 MPa grade product, the maximum-minimum deviation of the gel type was 0.57 MPa, whereas the maximum-minimum deviation of the powder type was 10.39 MPa.

[0334] In addition, for the 45 MPa grade product, the maximum-minimum deviation of the gel type was 0.83 MPa, while the maximum-minimum deviation of the powder type was 13.80 MPa.

[0335] This result demonstrates that powder-type nanocellulose rapidly absorbs moisture during the actual concrete mixing process, causing aggregation and potentially failing to be uniformly dispersed within the concrete composition.

[0336] On the other hand, since the saturated nanocellulose water dispersion is provided in a gel state containing moisture from the cellulose nanofibers, local free water absorption and aggregation are reduced even when in contact with mixing water, and uniform dispersion within the concrete composition is possible.

[0337] Referring to Figure 4, it can be seen that when a saturated nanocellulose water dispersion is applied, the variation in compressive strength among test specimens is reduced compared to when powdered nanocellulose is applied.

[0338] This means that saturated nanocellulose water dispersions are more uniformly dispersed within the concrete composition, and by suppressing fluctuations in the effective water content due to free water absorption during mixing, mix reproducibility and quality homogeneity can be improved.

[0339] In particular, the variation in compressive strength can be used as an indicator to determine whether product quality is uniformly reproduced under the same formulation and production process, rather than simply whether strength has improved.

[0340] Below, the mixing characteristics of the saturated water dispersion of the present invention and conventional powdered nanocellulose are compared with reference to [Table 11].

[0341] [Table 11] is a comparison table of the formulation characteristics of saturated water dispersions and powdered nanocellulose.

[0342] division Powdered nanocellulose Saturated nanocellulose aqueous dispersion Free water absorption Rapid absorption of free water possible upon contact with mixing water Inhibition of additional free water absorption by retained moisture slump Slump reduction possible due to localized moisture absorption Reduced slump is possible by maintaining effective water quantity. Air volume Air volume may fluctuate due to aggregation or non-homogenization of mixing. Reduced air volume fluctuations possible through improved dispersion Viscosity / Rheology Viscosity may increase due to aggregation and moisture absorption Viscosity increase can be suppressed through shear thinning and rheology adjustment. compressive strength deviation Increased variation in compressive strength among test specimens is possible Reduced variation in compressive strength among test specimens is possible Effective quantity Local effective quantity may fluctuate Effective water quantity can be stabilized through calculation of mixing water and correction of external input water. Formulation reproducibility Deviations may occur depending on differences in distribution status per batch. Improved formulation reproducibility is possible by correcting for retained moisture and mixing water. Production stability Possible reduction in mold filling capacity and demolding stability Improved mold filling performance, steam curing stability, and early demolding stability Quality homogeneity Increased variation in compressive strength among test specimens is possible Reduced variation in compressive strength and improved quality homogeneity are possible.

[0343] As shown in [Table 11], the saturated nanocellulose water dispersion of the present invention is adjusted to contain retained moisture, so it can reduce the decrease in slump, fluctuation in air content, increase in viscosity, and increase in compressive strength variation caused by the absorption of free water during concrete mixing.

[0344] In addition, the saturated nanocellulose aqueous dispersion of the present invention can exhibit effects that improve not only simple compressive strength compared to conventional powdered nanocellulose, but also effective water content stabilization, rheological homogenization, formulation reproducibility, production stability, and quality homogeneity.

[0345] As described above, the present invention can stably maintain the target water-to-binder ratio or effective water content of a concrete composition by calculating the water content of a saturated nanocellulose water dispersion as part of the mixing water and correcting the amount of external mixing water input. Accordingly, the present invention can reduce slump reduction, air content fluctuations, viscosity increase, and compressive strength deviations compared to the application of conventional powdered nanocellulose or diluted nanocellulose dispersions.

[0346] When conventional powdered nanocellulose as described above is added to a concrete composition, the powdered nanocellulose can rapidly absorb free water the moment it comes into contact with the mixing water. In this case, a localized reduction in the effective water content within the concrete composition may occur, and the powdered nanocellulose may swell or aggregate before it is sufficiently dispersed.

[0347] This phenomenon can lead to a decrease in slump, an increase in viscosity, fluctuations in air content, non-homogeneous mixing, and increased variation in compressive strength among test specimens.

[0348] On the other hand, since the saturated nanocellulose water dispersion of the present invention is adjusted so that the cellulose nanofibers contain retained moisture, it can suppress additional free water absorption during concrete mixing. Accordingly, the saturated nanocellulose water dispersion is advantageous for stably managing variations in slump, air content, viscosity, and compressive strength compared to powdered nanocellulose.

[0349] As described above, conventional powdered or diluted nanocellulose can cause free water absorption, aggregation, or mix inhomogeneity during concrete mixing; however, the saturated nanocellulose water dispersion of the present invention controls the moisture retention state, thereby suppressing additional free water absorption. Therefore, the present invention can be applied not merely as a technology for simple strength enhancement, but as a process control technology that improves the stability and quality reproducibility of the concrete manufacturing process.

[0350] Below, the evaluation of strength development by raw material type and type is explained.

[0351] First, strength development characteristics were compared according to the type of raw material and nanocellulose type.

[0352] At this time, the nanocellulose content was set to 1.0 part by weight per 100 parts by weight of cement.

[0353] Table 12 below shows a comparison of compressive strength by raw material type and type, comparing the average compressive strength and strength deviation of the sugarcane waste-derived gel type, sugarcane waste-derived powder type, acacia waste-derived gel type, and waste paper-derived gel type.

[0354] division 35 MPa average 35 MPa class maximum-minimum deviation 45 MPa average 45 MPa class maximum-minimum deviation Sugarcane Waste NC Gel Type 42.792 MPa 0.57 MPa 54.018 MPa 0.83 MPa Sugarcane Waste NC Powder Type 40.667 MPa 10.39 MPa 51.421 MPa 13.80 MPa Acacia Waste NC Gel Type 42.188 MPa 2.20 MPa 53.254 MPa 2.60 MPa Waste Extraction NC Gel Type 41.458 MPa 3.24 MPa 52.334 MPa 4.23 MPa

[0355] Referring to [Table 12], when gel-type nanocellulose is applied, the compressive strength and strength variation may vary depending on the type of raw material.

[0356] However, sugarcane waste NC Gel Type, acacia waste NC Gel Type, and waste paper extract NC Gel Type all showed higher average compressive strength than the standard formulation in 35 MPa and 45 MPa grade products.

[0357] In addition, the sugarcane waste NC Gel Type showed significantly smaller strength variation among test specimens compared to the powder type.

[0358] This means that when nanocellulose is provided in a gel state, a more uniform dispersion state can be secured in the actual concrete production process.

[0359] According to the above results, even if the raw material of nanocellulose changes, if it is provided as a saturated water dispersion or gel type, it can exhibit an effect of improving compressive strength, and in particular, a saturated nanocellulose water dispersion can increase the reproducibility of strength development compared to a powder type.

[0360] The results of the aforementioned test examples demonstrate that saturated nanocellulose water dispersions can improve the compressive strength of concrete compositions even at low incorporation amounts.

[0361] In particular, the effect of improving compressive strength was excellent in the range of 0.8 parts by weight or more and 1.2 parts by weight or less per 100 parts by weight of cement.

[0362] In addition, the test examples of the present invention were not simple laboratory-scale paste tests, vacuum mixer tests, or small test specimen tests, but were performed based on a mix applicable to the actual production process of concrete secondary products.

[0363] Therefore, the above test results support the applicability of saturated nanocellulose water dispersions in the actual production process of precast concrete structures.

[0364] In many conventional studies related to nanocellulose, a method was used in which an aqueous solution of cellulose nanocrystals (CNC) was stirred separately for a long time and then mixed using a vacuum mixer. While this method may be advantageous for ensuring dispersion on a laboratory scale, there was a problem in that it was difficult to replicate the same conditions in actual ready-mix concrete plants or concrete secondary product production processes.

[0365] On the other hand, the saturated nanocellulose water dispersion of the concrete composition of the present invention can be provided in a gel state containing moisture retained by cellulose nanofibers.

[0366] Therefore, saturated nanocellulose water dispersions can be introduced into the production process of concrete compositions without the need for a separate long-term dispersion process, and reliability in effective water content stability, incorporation, and mixing dispersion can be ensured.

[0367] In addition, as confirmed in [Table 7] and [Table 8], when a saturated nanocellulose water dispersion is incorporated at 1.0 weight part per 100 weight parts of cement, the cement content is reduced to 12 weight% or more and 18 weight% or less, and crushed fine aggregate is added in a weight corresponding to the reduced cement weight, the target compressive strength of 35 MPa grade products and 45 MPa grade products can be satisfied.

[0368] Accordingly, the concrete composition and manufacturing method of the present invention can reduce manufacturing costs and environmental burdens by reducing the amount of cement used, while securing the compressive strength required for precast concrete structures such as water pipes and manholes.

[0369] The concrete composition, method for manufacturing the concrete composition, and concrete structure of the present invention described above have the following effects.

[0370] By incorporating a saturated nanocellulose aqueous dispersion with a moisture content adjusted to suppress additional free water absorption by cellulose nanofibers into a concrete composition, the problem of dry powdered nanocellulose or low-moisture nanocellulose rapidly absorbing moisture and aggregating upon contact with mixing water can be reduced.

[0371] In addition, since the amount of water contained in the saturated nanocellulose water dispersion can be calculated as part of the mixing water of the concrete composition to correct the amount of water input, the actual effective water amount can be stabilized, and the reduction of slump, increase in viscosity, and mixing deviation can be suppressed.

[0372] In addition, the compressive strength of a concrete composition can be effectively improved by including a saturated nanocellulose water dispersion in an amount of 0.8 parts by weight or more and 1.2 parts by weight or less per 100 parts by weight of cement. Experimental results showed that when a saturated nanocellulose water dispersion was included in an amount of 1.0 part by weight per 100 parts by weight of cement, the 28-day compressive strength of a 35 MPa grade product was 42.792 MPa, and the 28-day compressive strength of a 45 MPa grade product was 54.018 MPa, which supports this.

[0373] In addition, the compressive strength required for concrete structures can be secured even when the cement content is reduced compared to the standard mix and crushed fine aggregate is added in an amount corresponding to the reduced cement weight. Specifically, when saturated nanocellulose water dispersion is included at 1.0 part by weight per 100 parts by weight of cement, and the cement content is reduced by 18% by weight compared to the standard mix, the 35 MPa grade product showed a 28-day compressive strength of 36.418 MPa and the 45 MPa grade product showed 46.072 MPa, satisfying the target compressive strength, and these experimental results support this.

[0374] In addition, since the amount of cement used can be reduced, the manufacturing cost of the concrete composition can be lowered, and the burden of carbon dioxide emissions generated during the cement manufacturing process can be reduced due to the decrease in cement usage.

[0375] In addition, by applying gel-type nanocellulose, the variation in compressive strength among test specimens can be reduced compared to the case where powder-type nanocellulose is applied. As a result of the experiment, for a 35 MPa grade product, the maximum-minimum compressive strength variation of the gel type was 0.57 MPa, while that of the powder type was 10.39 MPa; and for a 45 MPa grade product, the maximum-minimum compressive strength variation of the gel type was 0.83 MPa, while that of the powder type was 13.80 MPa. Therefore, the present invention can improve the uniformity and reproducibility of product quality in the repetitive production process of precast concrete structures.

[0376] In addition, since it is applicable to 35 MPa class mixes corresponding to pipe series products and 45 MPa class mixes corresponding to manhole series products, it can be applied to precast concrete structures such as flumes, bench flumes, pipes, reinforced concrete drainage pipes, concrete manhole blocks for sewers, manholes, prefabricated pump room manholes, pipe insertion integrated prefabricated PC manholes, and pressure pump room manholes.

[0377] The present invention has been described with reference to the above-described embodiments and the accompanying drawings, but this is merely illustrative, and those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible therefrom. Accordingly, the true technical scope of protection of the present invention should be determined by the technical spirit of the appended claims. Explanation of the symbols

[0378] S10: Preparation stage S11: Washing and Neutralization Steps S12: Moisture content adjustment and saturation step S13: High-shear dispersion step S14: Rheology adjustment step S20: Composition formation step S21: Mixing water calculation step S22: External mixing water input amount correction step S23: Mixing step

Claims

Claim 1 In a concrete composition used for manufacturing concrete structures, cement; coarse aggregate; crushed fine aggregate; admixture; external mixing water; and comprises a saturated nanocellulose water dispersion, wherein the saturated nanocellulose water dispersion is a gel-state water dispersion comprising cellulose nanofibers and retained moisture retained in the cellulose nanofibers, wherein the retained moisture is retained in the cellulose nanofibers to suppress additional free water absorption by the cellulose nanofibers during the mixing of the concrete composition, wherein the saturated nanocellulose water dispersion comprises 18 parts by weight or more and 20 parts by weight or less of cellulose nanofiber solids and 80 parts by weight or more and 82 parts by weight or less of retained moisture per 100 parts by weight of the saturated nanocellulose water dispersion, wherein the cellulose nanofibers have an average fiber diameter of 50 nm or more and less than 500 nm, wherein the saturated nanocellulose water dispersion is included in an amount of 0.8 parts by weight or more and 1.2 parts by weight or less per 100 parts by weight of the cement, and wherein the saturated nanocellulose water dispersion has 32,000 cP or more and 38,000 A concrete composition having a viscosity of cP or less and shear thinning characteristics, wherein the cement is included in an amount reduced by 12% to 18% by weight relative to the cement content of a standard mix containing cement, aggregate, water, and admixture so as to correspond to the target compressive strength without including the saturated nanocellulose water dispersion, the crushed fine aggregate is added in an amount corresponding to the difference between the cement content of the standard mix and the cement content reduced by weight, the retained water contained in the saturated nanocellulose water dispersion constitutes part of the mixing water of the concrete composition, and the external mixing water is included in an amount corrected by reducing the retained water amount corresponding to 80% to 82% by weight of the input amount of the saturated nanocellulose water dispersion. Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 A concrete composition according to claim 1, wherein the coarse aggregate is included in an amount of 190 parts by weight or more and 305 parts by weight or less per 100 parts by weight of the cement, and the crushed fine aggregate is included in an amount of 180 parts by weight or more and 285 parts by weight or less per 100 parts by weight of the cement. Claim 6 A concrete composition according to claim 1, wherein the saturated nanocellulose aqueous dispersion is a gel-state aqueous dispersion comprising cellulose nanofibers extracted from a cellulose-based raw material and not subjected to a drying and pulverizing process, and the retained moisture retained in the cellulose nanofibers. Claim 7 A concrete composition according to claim 1, wherein the admixture is included in an amount of 0.8 parts by weight or more and 1.1 parts by weight or less per 100 parts by weight of the cement. Claim 8 A method for manufacturing a concrete composition used in the manufacture of a concrete structure, comprising: a preparation step of preparing a saturated nanocellulose aqueous dispersion; and a composition forming step of forming a concrete composition by mixing the saturated nanocellulose water dispersion, cement, coarse aggregate, crushed fine aggregate, admixture, and external mixing water; wherein the saturated nanocellulose water dispersion is a gel-state water dispersion comprising cellulose nanofibers and retained moisture contained in the cellulose nanofibers, and the preparation step comprises: a washing and neutralization step of removing residual ions of cellulose nanofibers extracted from a cellulose-based raw material; a moisture content adjustment and saturation step of adjusting the moisture retention state of the cellulose nanofibers to include 18 parts by weight or more and 20 parts by weight or less of solid cellulose nanofibers and 80 parts by weight or more and 82 parts by weight or less of retained moisture per 100 parts by weight of the saturated nanocellulose water dispersion; and a high-shear dispersion step of applying shear force to the cellulose nanofibers so that the cellulose nanofibers are dispersed within the retained moisture. and a rheology adjustment step of adjusting the viscosity of the saturated nanocellulose water dispersion to 32,000 cP or more and 38,000 cP or less, and imparting shear thinning characteristics to the saturated nanocellulose water dispersion; wherein in the composition forming step, the saturated nanocellulose water dispersion is 0.8 parts by weight or more and 1 part by weight with respect to 100 parts by weight of the cement.A method for manufacturing a concrete composition, comprising mixing in an amount of 2 parts by weight or less, using the cement in an amount reduced by 12% by weight or more and 18% by weight or less relative to the cement content of a standard mix containing cement, aggregate, water, and an admixture so as to correspond to a target compressive strength without including the saturated nanocellulose water dispersion, adding crushed fine aggregate in an amount corresponding to the difference between the cement content of the standard mix and the cement content reduced by the amount, calculating the retained moisture corresponding to 80% by weight or more and 82% by weight or less of the input amount of the saturated nanocellulose water dispersion as part of the mixing water of the concrete composition, correcting the input amount of the external mixing water by subtracting the amount of the calculated retained moisture, and mixing the saturated nanocellulose water dispersion, the cement, the coarse aggregate, the crushed fine aggregate, the admixture, and the corrected external mixing water. Claim 9 A method for preparing a concrete composition according to claim 8, wherein, in the preparation step, the saturated nanocellulose aqueous dispersion is prepared in a gel state comprising cellulose nanofibers extracted from a cellulose-based raw material and not subjected to a drying and pulverizing process, and moisture retained in the cellulose nanofibers. Claim 10 A method for preparing a concrete composition according to claim 8, wherein in the composition forming step, the saturated nanocellulose water dispersion is mixed with the cement, the coarse aggregate, the crushed fine aggregate, the admixture, and the external mixing water without being prepared as a separate diluent or nanocellulose dispersion. Claim 11 delete Claim 12 delete Claim 13 delete Claim 14 delete Claim 15 A method for manufacturing a concrete composition according to claim 8, wherein in the composition forming step, the coarse aggregate is mixed in an amount of 190 parts by weight or more and 305 parts by weight or less with respect to 100 parts by weight of the cement, and the crushed fine aggregate is mixed in an amount of 180 parts by weight or more and 285 parts by weight or less with respect to 100 parts by weight of the cement. Claim 16 delete Claim 17 A method for manufacturing a concrete composition according to claim 8, wherein the deviation in unit water quantity between batches and the deviation in water-to-binder ratio are reduced by correcting the amount of external mixing water input. Claim 18 A method for manufacturing a concrete composition according to claim 8, wherein in the composition forming step, the amount of the saturated nanocellulose water dispersion added is denoted as A and the ratio of the retained moisture contained in the saturated nanocellulose water dispersion is denoted as R, the amount of retained moisture contained in the saturated nanocellulose water dispersion is calculated as A × R, and R is 0.80 or more and 0.82 or less. Claim 19 A method for manufacturing a concrete composition according to claim 8, wherein in the composition formation step, the external mixing water input amount corrected is calculated by subtracting the calculated retained water amount from the external mixing water input amount of a standard mixture that does not contain the saturated nanocellulose water dispersion. Claim 20 A concrete structure comprising a concrete body formed by curing a concrete composition of any one of claims 1, 5 to 7 after it is poured into a mold or die. Claim 21 In paragraph 20, the concrete structure is any one of a flume, a bench flume, a waterway pipe, and a reinforced concrete drainage pipe, and the concrete body is a concrete structure having a compressive strength of 35 MPa or more at 28 days of age. Claim 22 In paragraph 20, the concrete structure is any one of a concrete manhole block for a sewer, a manhole, a prefabricated pump room manhole, a pipe-insertable integrated prefabricated PC manhole, and a pressure pump room manhole, and the concrete body is a concrete structure having a 28-day compressive strength of 45 MPa or more.

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