Eco-friendly concrete composition and its manufacturing method

Abstract

The present invention relates to an eco-friendly concrete composition comprising a cellulose nanogel obtained from prickly pear and bagasse, and a method for manufacturing the same.

Description

Technology Field

[0001] The present invention relates to an eco-friendly concrete composition and a method for manufacturing the same. Background Technology

[0003] Nanocellulose is an organic polymer material with excellent tensile strength that is attracting attention as an eco-friendly next-generation material to replace organic binders. However, due to high manufacturing costs, nanocellulose is currently limited to the fields of medical, optical, and cosmetic materials. Consequently, its application has not been expanded to general industrial materials.

[0004] Although nanocellulose is not currently produced on an industrial scale, it can be extracted from cellulose-containing materials through various methods, which can be broadly classified into mechanical, chemical, and biological methods. Chemical methods involve hydrolyzing the properties of cellulose macromolecules using acids or enzymes; mechanical methods involve breaking hydrogen bonds within the cellulose using strong physical energy; and biological methods are generated by bacterial species. In the case of mechanical methods, crushing processes are used to shorten and split cellulose fibers, making it possible to manufacture fibers ranging from those with diameters and lengths of several micrometers to those with diameters and lengths of tens of nanometers.

[0005] Although there is currently no technology available for the application of nanocellulose to construction mortar and concrete on an industrial scale, many papers have recently been published on its application for the purpose of strengthening concrete or cement paste. Nanocellulose can be manufactured in gel and powder forms and is insoluble in water, allowing various types of nanocellulose to be mixed with cement. Examples include wood-based CNC, CNC extracted from carrots, microcellulose obtained by acid hydrolysis, nanocellulose extracted from waste generated during wood processing, and microbial cellulose. It has been reported that mixing these nanocelluloses into Portland cement, mortar powder, calcium aluminate cement (CAC) paste, and ordinary Portland cement (OPC) paste at a ratio of 0.04–1.15% can increase concrete strength by an average of 0.1–0.8% (Danuta Barnat-Hunek et al. 2019; Aofei Guo et al. 2020). Increasing the mixing ratio of woody nanocellulose to 0.5–2% relative to cement usage helps increase compressive strength by 13% and flexural strength by 12%, respectively, but there is no significant change in the tensile strength of the concrete. Cement containing cellulose nanocrystals (CNC) can increase specific gravity, reduce the water absorption of cement materials, and delay cement hydration, but hydration levels increase after a certain period. Although adding only a small amount of CNC can improve mechanical strength, using CNC at a high mixing ratio has a counterproductive effect. CNC can reduce air bubbles, increase the density of concrete blocks, and reduce drying shrinkage; however, if it exceeds a certain critical threshold, it can increase carbonation depth and reduce chloride ion penetration, but it is vulnerable to the harmful effects of some resistant freeze-thaw degradation.

[0006] Regarding cementitious materials incorporating cellulose nanofibers (CNF), each study demonstrates that CNF can reduce fluidity, act as a viscosity modifier, increase the specific gravity of cement, and reduce water absorption, while also enhancing thermal conductivity and thermal expansion. Furthermore, CNF can delay the onset of cement hydration, thereby increasing the level of hydration once a specific lifespan is achieved. Adding small amounts of CNF can improve mechanical properties, but adding excessive amounts can have adverse effects. CNF is effective for adjusting the capillary size of block concrete, but there are no consistent conclusions regarding its effect on porosity. Additionally, CNF can reduce free shrinkage and autogenous shrinkage, improve the surface tension and viscosity of cement paste, reduce the penetration of sulfate and chloride ions, and increase resistance to freeze-thaw cycles.

[0007] In the case of cement materials with added microbial cellulose (BC), it is believed that BC can act as a nano-crosslinker to reduce water absorption, improve mechanical properties, and prevent nano-curling. It is known that BC has almost no effect on the hydration, shrinkage, rheology, and durability of cement materials.

[0008] Cement with added cellulose fibers (CF) was also studied for comparison. It was found that CF can reduce fluidity and increase air content, increase the hydrate content for a specific lifespan, and improve mechanical properties, although they did not change significantly. CF can reinforce the surface transition zone (ITZ) between the cement paste and aggregates, and can also act as a factor that increases flow stress and changes viscosity. It is also known that CF has almost no effect on the shrinkage and durability of cement materials.

[0009] Meanwhile, one of the causes of the high manufacturing costs of chemical methods is the acid hydrolysis process of cellulose, in which Nickerson first used sulfuric acid in the early 1940s and has since been commonly used. Hydrolysis with sulfuric acid forms a very stable reaction system with a high negative charge due to the bonding of sulfuric acid ester groups on the surface of crystalline materials. However, hydrolysis methods using concentrated sulfuric acid at low temperatures result in low cellulose yields (Bondeson et al. (2009), Sharma et al. (2012)), which limits their use in the large-scale production of nanocellulose in industrial organizations. For example, according to a study by Bondeson et al. (2006), nanocellulose can be obtained from microcrystalline cellulose with only about 30% yield when acid hydrolyzing cellulose, and it has been reported that the yield of nanocellulose is much lower from other raw materials. For example, the yield of nanocellulose is 0.0256% in rye (Sharma et al. (2012)) and 16.9% in rice straw (Jiang & Hsieh, 2013). In addition, using high-concentration acid (~60%), which consumes a large amount, inevitably leads to limitations in application even on a laboratory scale. Patent Document 1 discloses a process for manufacturing nanocellulose in the form of cellulose powder, specifically a method of hydrolysis (5 hours, using sulfuric acid (concentration: 45%), 40°C), filtration of the recovered solution, introduction into a buffer solution to neutralize the pH to 7, centrifugal filtration, washing, and drying, and finally obtaining nanocellulose powder with a diameter of 100 to 200 nm.In Patent Document 1, the acid solution absorbed by the nanocellulose is effectively neutralized with NH3 or NH4Cl, and the resulting powdered nanocellulose, which is obtained by breaking surface hydrogen bonds, can form a stable colloid in water without clumping upon drying. Additionally, the buffer solution is inexpensive and readily available, and can be applied under mild reaction conditions, making it suitable for industrial-scale application. However, Patent Document 1 has the disadvantage of using high-concentration sulfuric acid, which poses a handling risk and is highly corrosive, thus limiting its use in reactors or processes, and also entails environmental problems due to waste generated after the reaction.

[0010] Mechanical methods were first developed by Turbak et al. in 1980 and can produce nanocellulose with longer fiber lengths and better fiber cohesion, thereby generating cellulose nanogels with stronger gelation; however, they tend to destroy the structure of the microfibers, resulting in lower molecular weight and crystallinity of the generated nanocellulose. Furthermore, mechanical homogenization consumes a large amount of power, so the zeta potential is low (-10 mV) (Stenstad et al. 2008). Therefore, there is a need for a method that can advance the nanocellulose manufacturing process by combining chemical and mechanical methods.

[0011] Patent Documents 2 and 3 disclose a process that combines chemical and mechanical methods. In the chemical method, TEMPO (a mixture of NaBr and NaClO), used as the main pretreatment agent, oxidizes hydroxyl functional groups when it interacts with cellulose and forms carboxylic acid groups at the C6 position of glucopyranose monomers, thereby allowing cellulose fibers to be easily separated from each other during grinding. Patent Document 2 discloses the effect of reducing grinding energy consumption when using lignocellulosic cellulose powder as a raw material thanks to the pretreatment, and Patent Document 3 discloses the effect of improving nanocellulose yield. However, Patent Documents 2 and 3 had problems such as a low nanocellulose yield of 19.7% when nanocellulose was extracted from non-limesilicic raw materials, increased manufacturing costs due to the high price of TEMPO, and environmental issues arising from waste, in addition to TEMPO interfering with the cellulose purification process.

[0012] The biological method was first studied and used by Henriksson et al. (European Polymer Journal, 43). Compared to the chemical method of acid treatment, it is more environmentally friendly and can produce nanocellulose with a higher average specific gravity and shrinkage rate by increasing the reactivity and swelling of cellulose fibers. However, there were limitations to its use due to the low zeta potential (-1.5-2 mv) and low efficiency (~12.3%) of nanocellulose.

[0013] Furthermore, there is a problem in that it is difficult to utilize the by-products generated during manufacturing due to the use of strong acids. Accordingly, there is a need for a method to obtain nanocellulose more safely, efficiently, and economically. Prior art literature

[0015] Chinese Registered Patent CN101942102 (May 23, 2012) Japanese Registered Patent JP4998981 (May 25, 2012) Published Patent WO2009 / 021688 (February 19, 2009) The problem to be solved

[0016] The objective of the present invention is to solve the problems described above by providing a composition of eco-friendly concrete and a method for manufacturing the same, which ensures process stability by obtaining cellulose from prickly pear and bagasse and applying a weak acid during hydrolysis, and is environmentally friendly while increasing the yield compared to conventional methods and lowering manufacturing costs. means of solving the problem

[0018] To achieve the above objective, a composition of eco-friendly concrete according to one embodiment of the present invention comprises a cellulose nanogel obtained from prickly pear and bagasse.

[0019] To achieve the above objective, a method for manufacturing eco-friendly concrete according to another embodiment of the present invention comprises the steps of: (a) obtaining a cellulose nanogel from prickly pear and bagasse; and (b) mixing the cellulose nanogel prepared in step (a) with a cement mixture.

[0020] Additionally, the above step (a) may include: (a-1) a step of separating cellulose from prickly pear and bagasse and then washing with a neutral solution; (a-2) a step of first bleaching the cellulose with a sodium hydroxide solution and a hydrogen peroxide solution and then neutralizing it; (a-3) a step of treating the cellulose neutralized in step (a-2) with a hydrogen peroxide and sulfuric acid solution to hydrolyze it and then neutralize it; (a-4) a step of secondarily bleaching the cellulose neutralized in step (a-3) with a sodium hydroxide solution and a hydrogen peroxide solution, then neutralizing it and pressing it; and (a-5) a step of diluting the pressed cellulose and then grinding it to produce a cellulose nanogel. Effects of the invention

[0022] According to one embodiment of the present invention, by replacing a portion of the cement with a cellulose nanogel obtained from bagasse and prickly pear, the concrete strength can be improved compared to conventional methods while contributing to environmental protection.

[0023] In addition, according to another embodiment of the present invention, by hydrolyzing with a weak acid and low temperature, by-products and waste generated during manufacturing can be utilized immediately without a separate treatment process, thus providing an economical and eco-friendly effect.

[0024] In addition, according to another embodiment of the present invention, the yield of cellulose can be increased by obtaining a cellulose nanogel from bagasse and prickly pear. Brief explanation of the drawing

[0026] FIG. 1 is a flowchart illustrating a method for manufacturing eco-friendly concrete according to one embodiment of the present invention. Figure 2 is a process diagram for explaining a method for manufacturing cellulose nanogels. Specific details for implementing the invention

[0027] Although the present invention is described in detail below according to the embodiments illustrated in the attached drawings, the present invention is not limited to the illustrated embodiments. The above and other objectives and novel features of the present invention will become more apparent from the description in this specification and the attached drawings.

[0029] Hereinafter, an eco-friendly concrete composition according to one embodiment of the present invention will be described in detail.

[0030] An eco-friendly concrete composition according to one embodiment of the present invention may include cellulose nanogels obtained from prickly pear and bagasse, wherein the cellulose nanogels may be prepared by two bleaching processes and acid hydrolysis.

[0031] For example, the cellulose nanogel may be a natural nanomaterial that is pale yellow in color, has a viscosity of about 300 mP.s, has a length of less than 1.0 µm, and has a diameter of less than 200 nm, for example, 100 nm or less. The cellulose nanogel has excellent flexibility and deformability, and has gel or thick suspension-forming properties. It has a higher viscosity than cellulose, and its viscosity decreases when stirred, and it tends to return to its original state when not stirred.

[0032] Meanwhile, the concrete according to the present embodiment can exhibit better biodegradability compared to concrete that does not contain cellulose nanogel by replacing a portion of the cement with cellulose nanogel, and can satisfy a flexural strength of 18.5 to 20 MPa and a compressive strength of 86 to 89 MPa after 28 days of curing, which may be an improvement of 7 to 13% in flexural strength and 8 to 10% in compressive strength compared to conventional materials.

[0033] In this embodiment, bagasse (sugar cane residue) is a waste product discarded by sugar companies after extracting sugar from sugarcane, and Sicyos angulatus is a plant notorious enough to have been designated as an ecosystem-disrupting species by the Ministry of Environment of South Korea on June 1, 2009. By recycling these bagasse and Sicyos angulatus as construction materials, it is possible to contribute to environmental protection while improving the strength of concrete compared to conventional methods.

[0035] Hereinafter, a method for manufacturing eco-friendly concrete according to another embodiment of the present invention will be described in detail with reference to the drawings.

[0036] FIG. 1 is a process flowchart for explaining a method for manufacturing eco-friendly concrete according to one embodiment of the present invention, and FIG. 2 is a process flowchart for explaining a method for manufacturing cellulose nanogel.

[0037] Referring to FIGS. 1 and 2, a cellulose nanogel is obtained from prickly pear and bagasse (S10).

[0038] After separating cellulose from prickly pear and bagasse, wash with a neutral solution (S11).

[0039] After adding 700 to 900 parts by weight of a sodium hydroxide solution with a concentration of 1 to 13%, for example 12 to 13%, to 100 parts by weight of prickly pear and bagasse, low-purity cellulose is separated from the prickly pear and bagasse by stirring in a closed or open equipment at 90 to 110°C for 120 to 150 minutes, for example 150 minutes, then washing at least three times with a neutral solution, i.e., industrial water, and pressing to a moisture content of 20 to 25%. In this embodiment, the solid-liquid ratio of the bagasse may be 1:7 to 9, and it is preferable to recover the neutral solution used as washing water in the first wash and use it as washing water for the second and third washes. It goes without saying that lignin can be separated from the washing water used and recovered at the end and added to concrete production.

[0040] In this embodiment, the bagasse (sugar cane residue) can be used to increase process efficiency by collecting the residue discarded by sugar companies after extracting sugar from sugarcane and drying it to a moisture content of 15% or less, for example, 12-14%. If the moisture content is 0%, the yield is good, but since a large amount of energy is required to remove moisture, not only is process efficiency reduced, but manufacturing costs may also increase. Sicyos angulatus can be used in a fresh state or in a dried state, either alone or in combination, and the state of use is not significantly restricted.

[0042] Then, the cellulose is bleached first with a sodium hydroxide solution and a hydrogen peroxide solution, and then neutralized (S12).

[0043] In step S11 above, 100 parts by weight of the washed cellulose are mixed with 1 to 3 parts by weight of a sodium hydroxide solution with a concentration of 1 to 10%, 3 to 5 parts by weight of a hydrogen peroxide solution with a concentration of 20 to 30%, and 992 to 996 parts by weight of water. After performing primary bleaching at 70 to 90°C for 100 to 150 minutes, the cellulose is neutralized by washing it several times with a neutral solution, i.e., industrial water, until the pH reaches 7, and then pressed to a moisture content of 20 to 25%. In this embodiment, the solid-to-liquid ratio of the cellulose may be 1:9 to 10. If the temperature and time mentioned above are exceeded, it is difficult to properly remove residual lignin, and the quality may deteriorate. Meanwhile, since the cellulose contains a relatively large amount of impurities during primary bleaching, it is preferable to use a larger amount of hydrogen peroxide solution compared to the secondary bleaching step described below.

[0045] Afterwards, the neutralized cellulose is treated with hydrogen peroxide and sulfuric acid solution to hydrolyze and neutralize it (S13).

[0046] 100 parts by weight of the cellulose neutralized in step S12 above can be hydrolyzed by treating it with 800 to 1000 parts by weight of a 0.5 to 0.7% concentration hydrogen peroxide solution and a 0.4 to 0.6% concentration sulfuric acid solution at 120 to 180°C, for example 140 to 160°C for 120 to 180 minutes, for example 140 to 160 minutes, and then washing it several times with a neutral solution, i.e., industrial water, until the pH reaches 7. In this embodiment, the solid-liquid ratio of the neutralized cellulose may be 1:8 to 10, and it may take 25 to 35 minutes, for example 30 minutes, to heat from room temperature to the maximum temperature, and the powder may be removed once the temperature maintenance is finished. If the above temperature is below 140℃, it may be difficult to secure the tensile strength required in the industry, and if it exceeds 160℃, small-sized nanocellulose can be obtained with high purity, but the yield may be low.

[0047] Through hydrolysis, macroscopic or microscopic cellulose can undergo cleavage across the amorphous region to produce rod-shaped materials called cellulose nanocrystals, with a high surface area of ​​1.50 g / cm³. 3 It can have a low density of less than 20 MPa and a high tensile strength of more than 20 MPa.

[0048] As described above, in this embodiment, by treating a low-concentration sulfuric acid solution at a low temperature, the washing process is not difficult, process stability is ensured, and manufacturing costs can be reduced compared to conventional methods while being environmentally friendly. Furthermore, since by-products generated during manufacturing due to the weak acid treatment can be utilized immediately without a separate processing step, it is economical and environmentally friendly.

[0049] For example, cellulose obtained through a sulfuric acid solution disperses well in water and may not have time-dependent viscosity.

[0051] Then, the neutralized cellulose is bleached a second time with a sodium hydroxide solution and a hydrogen peroxide solution, then neutralized and pressed (S14).

[0052] In step S13 above, 1 to 3 parts by weight of a sodium hydroxide solution with a concentration of 1 to 10%, 1 to 3 parts by weight of a hydrogen peroxide solution with a concentration of 20 to 30%, and 994 to 998 parts by weight of water are added to 100 parts by weight of the neutralized cellulose, and secondary bleaching is performed at 70 to 90°C for 40 to 80 minutes. Afterward, the cellulose is neutralized by washing it several times with a neutral solution, i.e., industrial water, until the pH reaches 7, and then pressed until the moisture content reaches 20 to 25%. In this embodiment, the solid-to-liquid ratio of the neutralized cellulose may be 1:9 to 10. If the temperature and time mentioned above are exceeded, it is difficult to properly remove residual lignin, and the quality may deteriorate. Since the cellulose is partially bleached in addition to hydrolysis during the first bleaching step, the content of the hydrogen peroxide solution can be lowered during the second bleaching step, thereby saving more cost and time.

[0054] Finally, the compressed cellulose is diluted and then ground to produce a cellulose nanogel (S15).

[0055] In step S14 above, the compressed cellulose can be diluted to a concentration of 10% and then ground with a shear mill for 1 to 3 minutes to produce a homogeneous cellulose nanogel with a concentration of 10 to 12%.

[0056] For example, the yield of the cellulose nanogel may be 25% or more relative to the weight of the prickly pear and bagasse, it may have a light yellow color, a viscosity of about 300 mP.s, a length of less than 1.0 µm, and a diameter of less than 200 nm, for example, less than 100 nm.

[0057] In the case of cellulose produced using prickly pear and bagasse, the diameter can be relatively small because the homogeneity is better compared to cellulose synthesized from algae, bacteria such as fungi, and marine animals.

[0058] Meanwhile, the alkaline wastewater generated in steps S11, S12, and S14 and the acidic wastewater generated in step S13 are mixed to produce neutral wastewater, which can be harmless to the environment. In addition, lignin can be recovered from the wastewater generated during the manufacturing process and added to concrete.

[0060] Then, the cellulose nanogel and cement mixture are mixed (S20).

[0061] The cellulose nanogel (NC) obtained in step S10 above can be mixed with a cement mixture, wherein the cellulose nanogel (NC) can be mixed in an amount of 1.0 to 2.0 parts by weight based on 100 parts by weight of cement. If the content of the cellulose nanogel (NC) is less than 1.0 parts by weight, the flexural strength and compressive strength may be low, and if it exceeds 2.0 parts by weight, the effect of the increase may not be very significant.

[0062] The cement mixture may include one or more selected from cement (C), sand (S), superplastic admixture (SD), crushed stone (CS), high-performance superplasticizer (SS), water (W), silica fume (SF), and fly ash (FA). Mineral additives may be further included as needed.

[0063] Cement (C) is one or more selected from Portland cement, Portland blast furnace slag cement, Portland fly ash cement, Portland pozzolan cement, masonry cement, dry cement mortar, silica cement, alumina cement, expansive cement, sulfate-resistant cement, and colloidal cement, with a specific gravity of 3.1 g / cm³ 3 , a standard amount of water 31%, a setting time of 120 minutes for initial setting and 210 minutes for final setting, a compressive strength of 22.3 MPa at 3 days and 43.7 MPa at 28 days can be used.

[0064] Superplastic Admixture (SD) may be used, for example, Silkroad SPR3000 conforming to TCVN 8826:2011 and ASTM C494 G type, and may be included in an amount of 0.1 to 1.0 parts by weight per 100 parts by weight of cement.

[0065] Silica fume (SF) is a substance added to enhance durability and improve cracking issues, with a specific gravity of 2.4 g / cm³. 3 , powder residue (45um) maximum 2.5%, powder residue (45um) average 1.0%, activity index at 7 days of age 105%, specific surface area 15 m² 2 / g, satisfying SiO2 content of 94%, water content of 1.2%, and weight loss upon calcination of 3%, may be used. Such silica fume may be included in an amount of 10 to 20 parts by weight per 100 parts by weight of cement.

[0066] Sand (S) is a substance added to ensure strength and durability, with a specific gravity of 2.65 g / cm³ 3, dry state volume mass 2.46 g / cm³ 3 , surface saturated volume mass 2.53 g / cm³ 3 , foam volume mass 1.59 g / cm³ 3 , satisfies an absorption rate of 2.93%, a dust, silt, and clay content of 1.5%, and a size factor (MdI) of 2.6, and can be used. Such sand may be included in an amount of 100 to 300 parts by weight per 100 parts by weight of cement.

[0067] Crushed stone (CS) is a material added to ensure strength and durability, with a specific gravity of 2.74 g / cm³. 3 , dry state volume mass 2.71 g / cm³ 3 , surface saturated volume mass 2.73 g / cm³ 3 , foam volume mass D20 type 1395 kg / m³ 3 , foam volume mass D10 type 1350 kg / m3, water absorption 0.4%, and dust, silt, and clay content 0.3% may be used. Such crushed stone may be included in an amount of 150 to 300 parts by weight per 100 parts by weight of cement.

[0068] High-performance superplasticizers (SS) are substances added to further enhance the function of general superplasticizers, effectively disperse cement, and prevent adverse effects such as delayed setting, reduced strength, and excessive air entrainment; for example, Silk Road High-performance Superplasticizer (SPR3000) can be used. Such high-performance superplasticizers may be included in an amount of 1 to 2 parts by weight per 100 parts by weight of cement.

[0069] Fly ash (FA) is a material added to enhance potential hydraulic properties, long-term strength, and durability, with a specific gravity of 2.2–2.3 g / cm³. 3Fly ash satisfying a moisture content of 0.6% or less, a weight loss of 5.5% upon calcination, and a powder residue of 23% (45 µm) may be used. Such fly ash may be included in an amount of 20 to 60 parts by weight per 100 parts by weight of cement, but if the fly ash content deviates from the ratio mentioned above, it may be difficult to satisfy the tensile strength and compressive strength required by the industry.

[0070] Concrete produced by the above-described manufacturing method can reduce the amount of cement used by 10 to 12% compared to conventional methods, while improving flexural strength and tensile strength by about 7 to 13% and compressive strength by about 8 to 10%, or achieving the same strength.

[0072] Examples 1 and 2. Concrete manufacturing

[0073] Concrete was manufactured by mixing according to the composition and ratios listed in Table 1 below.

[0074] The ratio is parts by weight.

[0075] division C S W SD NC Example 1 100 135 24 0.7 1 Example 2 100 135 24 0.7 1.5

[0077] Examples 3 to 5. Concrete preparation

[0078] Concrete was manufactured by mixing according to the composition and ratios listed in Table 2 below.

[0079] The ratio is parts by weight.

[0080] division C S CS SS W SF FA NC Example 3 100 146 219 1.3 39.7 - 32.9 1.3 Example 4 100 155 172 1.4 35.8 14.2 28.7 1.4 Example 5 100 190 212 1.75 44 17.5 58.3 1.8

[0082] Comparative Example 1. Concrete manufacturing

[0083] Concrete was prepared in the same manner as in Example 1, except that cellulose nanogel (NC) was not used.

[0085] Comparative Examples 2 to 4. Concrete manufacturing

[0086] Concrete was manufactured by mixing according to the composition and ratios listed in Table 3 below.

[0087] The ratio is parts by weight.

[0088] division C S CS SS W SF FA NC Comparative Example 2 100 268 277 1 46 - 25 - Comparative Example 3 100 146 219 1.3 39.7 - 32.9 - Comparative Example 4 100 155 172 1.4 35.8 14.2 28.7 -

[0090] Experimental Example 1. Strength Evaluation

[0091] The compressive strength (KS F 2405), flexural strength (KS F 2408), tensile strength, and slump of the concrete prepared in Examples 1 to 6 and Comparative Examples 1 to 4 were measured, and the results are shown in Tables 4 and 5.

[0092] division Example 1 Example 2 Comparative Example 1 7 days Flexural strength (MPa) 16.1 15 15.3 Compressive strength (MPa) 70.6 73.4 71.1 28th Flexural strength (MPa) 19.6 18.6 18.1 Compressive strength (MPa) 88.6 86.4 85.7

[0093] Referring to Table 4, it was confirmed that after 28 days, when the concrete was fully hardened, Examples 1 and 2 containing cellulose nanogel had higher flexural and compressive strengths compared to Comparative Example 1, which did not contain cellulose nanogel. The flexural and compressive strengths were best when the cellulose nanogel content was 1 wt%.

[0094] division Example 3 Example 4 Example 5 Comparative Example 2 Comparative Example 3 Comparative Example 4 Slump (mm) 570 730 700 480 550 710 Tensile strength (MPa) 7.14 7.41 7.20 5.22 6.72 6.90 Compressive strength (MPa) 64.5 68.5 63.8 45.0 59.6 62.4

[0095] Referring to Table 5, the example containing cellulose nanogel under the same conditions showed superior slump, tensile strength, and compressive strength. Meanwhile, Example 5, in which the cement content was reduced and the fly ash content was increased, showed lower values ​​in all categories compared to Example 4, but it satisfied the numerical range required by the industry.

[0097] Although exemplary embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims also fall within the scope of the present invention.

[0098] All technical terms used in this invention, unless otherwise defined, are used in the sense generally understood by those skilled in the art in the relevant field of this invention. The contents of all publications cited as references in this specification are incorporated into this invention.

Claims

Claim 1 Cellulose nanogels obtained from prickly pear and bagasse In an eco-friendly concrete composition, the cellulose nanogel is prepared by a hydrolysis process using hydrogen peroxide and sulfuric acid solutions, and by primary and secondary bleaching processes performed using a sodium hydroxide solution and a hydrogen peroxide solution, respectively, before and after the hydrolysis process; the primary bleaching process is carried out for 100 to 150 minutes at 70 to 90°C by adding 1 to 3 parts by weight of a sodium hydroxide solution with a concentration of 1 to 10% and 3 to 5 parts by weight of a hydrogen peroxide solution with a concentration of 20 to 30% to 100 parts by weight of cellulose; the secondary bleaching process is carried out for 40 to 80 minutes at 70 to 90°C by adding 1 to 3 parts by weight of a sodium hydroxide solution with a concentration of 1 to 10% and 1 to 3 parts by weight of a hydrogen peroxide solution with a concentration of 20 to 30% to 100 parts by weight of neutralized cellulose; and the cellulose nanogel is of a concentration An eco-friendly concrete composition having a viscosity of 10~12%, a viscosity of 200~400 mPa.s, and a length of less than 1.0 µm, wherein the composition satisfies the ranges of a slump of 570~700 mm, a tensile strength of 7.14~7.41 MPa, and a compressive strength of 63.8~68.5 MPa, satisfies the ranges of a flexural strength of 15~16.1 MPa and a compressive strength of 70.6~73.4 MPa after 7 days of curing, and satisfies the ranges of a flexural strength of 18.5~20 MPa and a compressive strength of 86~89 MPa after 28 days of curing. Claim 2 delete Claim 3 delete Claim 4 A method for manufacturing eco-friendly concrete comprises: (a) a step of obtaining a cellulose nanogel from prickly pear and bagasse; and (b) a step of mixing the cellulose nanogel obtained in step (a) with a cement mixture; wherein step (a) comprises: (a-1) a step of separating cellulose from prickly pear and bagasse and washing it with a neutral solution; (a-2) a step of first bleaching the cellulose with a sodium hydroxide solution and a hydrogen peroxide solution and then neutralizing it; (a-3) a step of treating the cellulose neutralized in step (a-2) with a hydrogen peroxide and sulfuric acid solution to hydrolyze it and then neutralize it; and (a-4) a step of secondarily bleaching the cellulose neutralized in step (a-3) with a sodium hydroxide solution and a hydrogen peroxide solution, then neutralizing it and compressing it. and (a-5) a step of preparing a cellulose nanogel by diluting and then grinding the compressed cellulose; wherein in step (a-2), the first bleaching is performed by adding 1 to 3 parts by weight of a sodium hydroxide solution with a concentration of 1 to 10% and 3 to 5 parts by weight of a hydrogen peroxide solution with a concentration of 20 to 30% to 100 parts by weight of cellulose and carrying out the bleaching at 70 to 90°C for 100 to 150 minutes; wherein in step (a-4), the second bleaching is performed by adding 1 to 3 parts by weight of a sodium hydroxide solution with a concentration of 1 to 10% and 1 to 3 parts by weight of a hydrogen peroxide solution with a concentration of 20 to 30% to 100 parts by weight of neutralized cellulose and carrying out the bleaching at 70 to 90°C for 40 to 80 minutes; and the cellulose nanogel prepared in step (a-5) has a concentration of 10 to 12% and a viscosity A method for manufacturing eco-friendly concrete having a slump of 200~400 mPa.s and a length of less than 1.0 µm, wherein the eco-friendly concrete satisfies the ranges of a slump of 570~700 mm, a tensile strength of 7.14~7.41 MPa, and a compressive strength of 63.8~68.5 MPa, satisfies the ranges of a flexural strength of 15~16.1 MPa and a compressive strength of 70.6~73.4 MPa after 7 days of curing, and satisfies the ranges of a flexural strength of 18.5~20 MPa and a compressive strength of 86~89 MPa after 28 days of curing. Claim 5 delete Claim 6 delete Claim 7 delete Claim 8 A method for manufacturing eco-friendly concrete according to claim 4, wherein in step (a-5), the cellulose nanogel has a diameter of less than 200 nm.

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