Concrete cementitious composite material containing nano sulfur and preparation method of concrete cementitious composite material

Abstract

The invention discloses a concrete gel composite material containing nano sulfur and a preparation method of the concrete gel composite material, and belongs to the technical field of preparation of additives for concrete. The preparation method comprises the following steps: mixing a Schiff base derivative, a catechol derivative, EDC hydrochloride and N-hydroxysuccinimide, and reacting to obtain a modified catechol derivative; mixing, dispersing and emulsifying the modified catechol derivative and nano sulfur, and performing cross-linking reaction to obtain microcapsule suspension; and mixing and polymerizing the microcapsule suspension, polypropylene fiber and an initiator to obtain the concrete gel composite material. The preparation method comprises the following steps: firstly, mixing and reacting a Schiff base derivative with a catechol derivative with a catechol structure to obtain a modified catechol derivative, then mixing the modified catechol derivative with nano sulfur, and carrying out alkaline oxidation auto-polymerization to obtain a microcapsule suspension wrapping the nano sulfur; and mixing the polypropylene fiber with the microcapsule suspension for reaction to obtain the concrete gel composite material containing the nano sulfur.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of concrete additives, and particularly relates to a concrete cementitious composite material containing nano-sulfur and a preparation method thereof. Background Art

[0002] Concrete is one of the most important building materials in modern construction, widely used in a variety of projects, including bridges, high-rise buildings, and dams. Due to its high strength and excellent durability, concrete occupies a pivotal position in the construction industry. Concrete's basic components include water, cement, aggregates, and admixtures. Each component has a significant impact on concrete's properties, including its impermeability. Water is an indispensable component of concrete, primarily reacting with cement to form a cement paste. Cement, the binder in concrete, is primarily composed of silicate minerals. Different types of cement have different hydration characteristics and impermeability. Aggregates are divided into coarse and fine aggregates, primarily responsible for the volume and strength of concrete. The particle size, shape, gradation, and surface characteristics of aggregates all affect the compactness and impermeability of concrete. Admixtures, such as water-reducing agents, air-entraining agents, and early-strength agents, are impermeable materials used to improve the density, impermeability, and mechanical properties of concrete. Appropriate use of admixtures can effectively improve the impermeability of concrete. The impermeability of concrete refers to the ability of concrete to resist the penetration of water or other liquids. This property is crucial to the durability and structural safety of concrete, and is mainly manifested in the following aspects: (1) Preventing water intrusion: The impermeability of concrete can effectively prevent the intrusion of water, prevent water from corroding the interior of the concrete, and thus reduce the strength of the concrete. This is especially important for structures that are in a humid environment for a long time, such as underground projects and bridge foundations. (2) Reducing chemical corrosion: Salts and other chemicals dissolved in water can corrode concrete, causing concrete deterioration. Good impermeability can reduce the intrusion of chemicals, thereby extending the service life of concrete. (3) Preventing freeze-thaw damage: In cold areas, after water penetrates into concrete, if the temperature drops to freezing point, the water will freeze and expand, causing the concrete to crack. Impermeable concrete can effectively reduce water penetration, thereby reducing the risk of freeze-thaw damage. (4) Ensuring structural safety: The impermeability of concrete directly affects the safety of the building structure. Water seepage may cause problems such as steel corrosion and concrete cracking, which will affect the overall stability and bearing capacity of the structure.

[0003] In order to improve the impermeability of concrete, a variety of methods and technologies are used in existing construction, mainly including the following: (1) Reducing the water-cement ratio: The water-cement ratio is one of the key factors affecting the impermeability of concrete. By reducing the water-cement ratio, the density of concrete can be increased, the porosity can be reduced, and the impermeability can be effectively improved; (2) Using high-performance cement: Selecting cement with good impermeability, such as slag cement, fly ash cement, etc., can improve the performance of concrete. The hydration products formed by these cements during the hydration process can fill the tiny pores in the concrete, enhance the density of the concrete, and thus improve the impermeability. (3) Optimize aggregate gradation: Reasonable aggregate gradation can improve the density of concrete, reduce porosity, form a better filling effect, and thus improve the anti-permeability performance; (4) Add admixtures: The use of admixtures can significantly improve the anti-permeability performance of concrete, such as water reducers (which can reduce the amount of water and lower the water-cement ratio, thereby enhancing the density of concrete) and air entraining agents (which introduce tiny bubbles into concrete, which can improve the freeze-thaw resistance of concrete and reduce water permeability); (5) Surface treatment: Coating or spraying a special waterproofing agent on the concrete surface can effectively prevent water penetration. This method is suitable for structures with high waterproofing requirements, such as underground projects and pools. (6) Maintenance: Good maintenance measures can promote the hydration reaction of concrete, enhance its structural density, and thus improve the anti-permeability performance.

[0004] Sulfur concrete is a new type of thermoplastic building material that uses sulfur as a binder to bond mineral fillers, aggregates, and other raw materials together. Due to sulfur's excellent binding and bonding properties, sulfur concrete has low water absorption and is resistant to erosion and penetration. Therefore, sulfur holds great promise for its application in the field of concrete impermeability. However, during construction, sulfur often needs to be heated and melted before use. This leads to excessive volume shrinkage upon cooling, which can easily cause cracks and brittle failure, thus weakening the performance of sulfur concrete. Therefore, existing techniques have been used to improve the performance of sulfur concrete by pre-treating sulfur before applying it to concrete preparation.

[0005] Patent CN118530001A discloses an asphalt mixture based on water-resistant modified sulfur and its preparation method. The invention polymerizes sulfur and sodium lignin sulfonate under high temperature conditions to connect small sulfur molecules into large molecular long chains. At the same time, sodium lignin sulfonate also has a surface active effect and can reduce the surface tension of water. After the modified sulfur asphalt mortar is fully mixed with the aggregate, the modified sulfur asphalt mortar is wrapped around the surface of the mixture, which can effectively improve the water stability of the asphalt mixture; at the same time, based on the functional group modification effect of sodium lignin sulfonate, the water stability, mechanical properties and high-temperature performance of the asphalt mixture can be simultaneously improved.

[0006] Patent CN117447161A discloses a pavement material containing composite modified asphalt, its preparation method and application. The invention obtains a sulfur / SBS / terpene resin modified asphalt with good anti-cracking stability by melt-mixing asphalt, SBS, sulfur and terpene resin, which makes the asphalt concrete have good stability.

[0007] Due to its inherent powder properties and fine particle size, sulfur is prone to agglomeration when directly mixed with modified materials, resulting in poor modification results. Therefore, it is of great significance to improve the agglomeration of sulfur and thus achieve its modification so that it can be mixed with concrete materials to produce concrete with good properties. Summary of the Invention

[0008] To address the shortcomings of the prior art, the present invention first reacts a Schiff base derivative with a catechol derivative having a catechol structure to obtain a modified catechol derivative. The modified catechol derivative is then mixed with nanosulfur and subjected to alkaline oxidation and autopolymerization to obtain a microcapsule suspension containing the nanosulfur. Polypropylene fiber is then reacted with the microcapsule suspension to obtain a nanosulfur-containing concrete cementitious composite material, thereby resolving the technical problems identified in the prior art. Specifically, the present invention comprises the following technical solutions: A method for preparing a concrete cementitious composite material containing nano-sulfur, the preparation method comprising the following steps: The Schiff base derivative, the catechol derivative, EDC hydrochloride and N-hydroxysuccinimide are mixed and reacted in a weight ratio of 1:3-4:1.5-2:1 to obtain a modified catechol derivative; The modified catechol derivative and nano-sulfur are mixed, dispersed and emulsified in a weight ratio of 0.3-0.5:1, and then cross-linked to obtain a microcapsule suspension; The microcapsule suspension, polypropylene fiber and initiator are mixed and polymerized according to a weight ratio of 10:0.1-0.2:0.01-0.02 to obtain a concrete cementitious composite material.

[0009] Furthermore, the preparation method of the Schiff base derivative comprises the following steps: The enal derivative, the diamine cross-linking agent, the anhydrous ethanol and the acetic acid are mixed in a weight ratio of 2-3:1:18-24:0.2-0.3, and heated to react to obtain the Schiff base derivative.

[0010] Furthermore, the olefinic aldehyde derivative includes cinnamaldehyde, and the structure of the olefinic aldehyde derivative needs to contain a benzene ring to jointly improve the high temperature stability.

[0011] Furthermore, the diamine cross-linking agent includes propylene diamine.

[0012] Furthermore, the conditions for the mixed heating reaction include a temperature of 60° C. to 70° C. and a reaction time of 3 h to 5 h.

[0013] Furthermore, the catechol derivative includes levodopa.

[0014] Furthermore, the mixed reaction process of the Schiff base derivative, catechol derivative, EDC hydrochloride and N-hydroxysuccinimide includes pre-activation treatment for 30 minutes in an environment with a pH of 5.5 and a temperature of 20°C, and then reacting for 8 hours to 12 hours in an environment with a pH of 7.0 and a temperature of 30°C.

[0015] Furthermore, the particle size of the nano-sulfur is 50 nm.

[0016] Furthermore, the mixing, dispersing and emulsifying conditions include mixing an emulsifier, a rotation speed of 600 r / min and an emulsification time of 20 min to 30 min.

[0017] Furthermore, the mixed emulsifier is composed of Span 60 and sodium lauryl sulfate in a weight ratio of 1:0.5.

[0018] Furthermore, the conditions of the cross-linking reaction include a reaction pH of 8.0-8.5, a reaction temperature of 25° C., a stirring speed of 400 r / min-500 r / min, and a reaction time of 18 h-20 h.

[0019] Furthermore, the polypropylene fibers are polypropylene chopped fibers.

[0020] Furthermore, the initiator includes azobisisobutyronitrile.

[0021] Furthermore, the conditions for the mixed polymerization include a rotation speed of 400 r / min, a reaction temperature of 65° C. to 70° C., and a reaction time of 2 h to 3 h.

[0022] A second object of the present invention is to provide a concrete cementitious composite material obtained by a method for preparing a concrete cementitious composite material containing nano-sulfur.

[0023] Compared with the prior art, the present invention has the following beneficial effects: The present invention first reacts an aldehyde derivative containing a benzene ring structure with a diamine crosslinker. The aldehyde group and the diamine crosslinker condense to form a high-temperature resistant imine bond structure, thereby obtaining a Schiff base derivative. The Schiff base derivative is then mixed with a catechol derivative having a catechol structure. The amino groups on the Schiff base derivative and the carboxyl groups on the catechol derivative undergo an amidation condensation reaction, thereby introducing the high-temperature resistant imine bond structure and a carbon-carbon double bond structure into the side chain of the catechol derivative, thereby obtaining a modified catechol derivative. Subsequently, utilizing the mechanism of molecular biomimetic, the modified catechol derivative and nanosulfur are ultrasonically mixed and dispersed to form a mixed emulsion. The mixed emulsion is then adjusted to a weakly alkaline environment, causing the catechol-structured levodopa to oxidatively self-polymerize to form a poly-levodopa structure with adhesive properties, thereby encapsulating the nanosulfur and obtaining a nanosulfur-encapsulated microcapsule suspension. The invention further comprises mixing polypropylene fibers capable of reducing plastic cracks in concrete with a microcapsule suspension, and combining the two via a carbon-carbon double bond reaction catalyzed by an initiator to obtain a nano-sulfur-containing concrete cementitious composite material. The imine bond and benzene ring structure in the concrete cementitious composite material structure can improve the stability of the concrete cementitious composite material when heated at high temperatures, thereby preventing the nano-sulfur from prematurely seeping out and ensuring the uniformity of the nano-sulfur dispersion. The polypropylene fibers are introduced into the concrete cementitious composite material through initiated polymerization, so that the polypropylene fibers, which are incompatible with the concrete interface, can be preferably integrated into the concrete through the concrete cementitious composite material. The synergistic effect of the polypropylene fibers and the nano-sulfur improves the mechanical properties and impermeability of the concrete prepared by using the concrete cementitious composite material of the invention. DETAILED DESCRIPTION

[0024] The following will clearly and completely describe the technical solutions of the present invention through the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present invention.

[0025] Unless otherwise specified, the raw materials and reagents used in the present invention are commercially available or can be prepared by known methods.

[0026] Nanosulfur was purchased from Zhejiang Yamei Nanotechnology Co., Ltd. Polypropylene chopped fibers were purchased from Zibo Baina New Material Technology Co., Ltd. Preparation Example 1: The preparation method of the Schiff base derivative specifically includes the following steps: 200g of cinnamaldehyde and 1800g of anhydrous ethanol were weighed and added to a reactor, where they were stirred at 100 r / min. 100g of 1,3-propylenediamine was then added to the reactor and continued to stir until uniformly dispersed. Finally, 20g of acetic acid (0.01 mol / L) was added as a co-catalyst. The stirring speed was increased to 200 r / min, and the temperature was raised to 60°C for a timed reaction of 3 hours. After the reaction, the anhydrous ethanol was evaporated under reduced pressure. After cooling to room temperature, the mixture was vacuum filtered to obtain a filter cake. The filter cake was rinsed with anhydrous ethanol and dried under vacuum at 55°C to obtain the Schiff base derivative.

[0027] Preparation Example 2: The preparation method of the Schiff base derivative specifically includes the following steps: 250g of cinnamaldehyde and 2000g of anhydrous ethanol were added to a reactor and stirred at 100 r / min. Then, 100g of 1,3-propylenediamine was added to the reactor and continued to stir until uniformly dispersed. Finally, 25g of acetic acid (molar concentration of 0.01 mol / L) was added as a co-catalyst. The stirring speed was increased to 200 r / min, and the temperature was raised to 65°C for a timed reaction of 4 hours. After the reaction, the anhydrous ethanol was evaporated under reduced pressure. After cooling to room temperature, the mixture was vacuum filtered to obtain a filter cake. The filter cake was rinsed with anhydrous ethanol and dried in vacuo at 55°C to obtain the Schiff base derivative.

[0028] Preparation Example 3: The preparation method of the Schiff base derivative specifically includes the following steps: 300g of cinnamaldehyde and 2400g of anhydrous ethanol were added to a reactor and stirred at 100 r / min. Then, 100g of 1,3-propylenediamine was added to the reactor and continued to stir until uniformly dispersed. Finally, 30g of acetic acid (0.01 mol / L) was added as a co-catalyst. The stirring speed was increased to 200 r / min, and the temperature was raised to 70°C for a timed reaction of 5 hours. After the reaction, the anhydrous ethanol was evaporated under reduced pressure. After cooling to room temperature, the mixture was vacuum filtered to obtain a filter cake. The filter cake was rinsed with anhydrous ethanol and dried in vacuo at 55°C to obtain the Schiff base derivative.

[0029] Preparation Example 4: The preparation method of the Schiff base derivative specifically includes the following steps: 300g of trans-2-hexenal and 2400g of anhydrous ethanol were added to a reactor and stirred at 100 r / min. Then, 100g of 1,3-propylenediamine was added to the reactor and continued to stir until uniformly dispersed. Finally, 30g of acetic acid (0.01 mol / L) was added as a co-catalyst. The stirring speed was increased to 200 r / min, and the temperature was raised to 70°C for a timed reaction of 5 hours. After the reaction, the anhydrous ethanol was evaporated under reduced pressure. After cooling to room temperature, the mixture was vacuum filtered to obtain a filter cake. The filter cake was rinsed with anhydrous ethanol and dried in vacuo at 55°C to obtain the Schiff base derivative.

[0030] Preparation Example 5: The preparation method of the Schiff base derivative specifically includes the following steps: 300g of cinnamaldehyde and 2400g of anhydrous ethanol were added to a reactor and stirred at 100 r / min. Then, 100g of 1,6-hexanediamine was added to the reactor and continued to stir until uniformly dispersed. Finally, 30g of acetic acid (0.01 mol / L) was added as a co-catalyst. The stirring speed was increased to 200 r / min, and the temperature was raised to 70°C for a timed reaction of 5 hours. After the reaction, the anhydrous ethanol was evaporated under reduced pressure. After cooling to room temperature, the mixture was vacuum filtered to obtain a filter cake. The filter cake was rinsed with anhydrous ethanol and dried in vacuo at 55°C to obtain the Schiff base derivative.

[0031] Example 1, a method for preparing a concrete cementitious composite material containing nano-sulfur, specifically comprising the following steps: 600g of levodopa was weighed and added to 3L of anhydrous dimethyl sulfoxide solvent. The mixture was ultrasonically dispersed at 200W for 20 minutes to obtain a dispersion. 300g of EDC hydrochloride and 200g of N-hydroxysuccinimide were then weighed and added to the dispersion. The pH was then adjusted to 5.5 with dilute hydrochloric acid. The temperature was then controlled to 20°C and the mixture was stirred at 400r / min for 30 minutes for pre-activation. After the pre-activation, the pH was adjusted to 7.0 with aqueous ammonia. 200g of the Schiff base derivative obtained in Preparation Example 1 was added and mixed and stirred. The mixture was heated to 30°C and reacted for 8 hours. After the reaction, anhydrous ethanol was added, mixed and stirred, and the precipitate was collected by centrifugation. The precipitate was rinsed with anhydrous ethanol and then rinsed with deionized water until the rinse water became neutral. Finally, the mixture was dried in a vacuum drying oven at 60°C to obtain a modified catechol derivative. 30 g of the modified catechol derivative was weighed and added to 4 L of Tris-hydrochloric acid buffer solution with a pH of 8.0. 1 g of a mixed emulsifier (composed of Span 60 and sodium lauryl sulfate in a weight ratio of 1:0.5) and 100 g of nanosulfur (particle size of 50 nm) were then added and mixed. The mixture was then stirred at 600 rpm for 20 min while controlling the temperature at 25°C. After emulsification, the speed was reduced to 400 rpm, and the cross-linking reaction was stirred for 18 h to obtain a microcapsule suspension. 10 parts by weight of microcapsule suspension, 0.1 parts by weight of polypropylene short fibers and 0.01 parts by weight of azobisisobutyronitrile were weighed and mixed, heated to 65° C., and stirred at a speed of 400 r / min for 2 h. After the reaction was completed, it was naturally cooled to room temperature, and the precipitate was collected by centrifugation to obtain a concrete cementitious composite material.

[0032] Example 2, a method for preparing a concrete cementitious composite material containing nano-sulfur, specifically comprising the following steps: 700g of levodopa was weighed and added to 3L of anhydrous dimethyl sulfoxide solvent. The mixture was ultrasonically dispersed at 200W for 20 minutes to obtain a dispersion. 350g of EDC hydrochloride and 200g of N-hydroxysuccinimide were then weighed and added to the dispersion. The pH was then adjusted to 5.5 with dilute hydrochloric acid. The temperature was then controlled to 20°C and the mixture was stirred at 400r / min for 30 minutes for pre-activation. After the pre-activation, the pH was adjusted to 7.0 with aqueous ammonia. 200g of the Schiff base derivative obtained in Preparation Example 2 was added and mixed and stirred. The mixture was heated to 30°C and reacted for 10 hours. After the reaction, anhydrous ethanol was added, mixed and stirred, and the precipitate was collected by centrifugation. The precipitate was rinsed with anhydrous ethanol and then rinsed with deionized water until the rinse water became neutral. Finally, the mixture was dried in a vacuum drying oven at 60°C to obtain a modified catechol derivative. 40 g of the modified catechol derivative was weighed and added to 4 L of Tris-hydrochloric acid buffer with a pH of 8.5. 1 g of a mixed emulsifier (composed of Span 60 and sodium lauryl sulfate in a weight ratio of 1:0.5) and 100 g of nanosulfur (particle size of 50 nm) were then added and mixed. The mixture was then stirred at 600 rpm for 25 minutes while maintaining the temperature at 25°C. After emulsification, the speed was reduced to 400 rpm, and the mixture was stirred for a cross-linking reaction for 19 hours to obtain a microcapsule suspension. 10 parts by weight of microcapsule suspension, 0.15 parts by weight of polypropylene chopped fibers and 0.015 parts of azobisisobutyronitrile were weighed and mixed, heated to 70° C., and stirred at a speed of 400 r / min for 2.5 hours. After the reaction was completed, it was naturally cooled to room temperature, and the precipitate was collected by centrifugation to obtain a concrete cementitious composite material.

[0033] Example 3, a method for preparing a concrete cementitious composite material containing nano-sulfur, specifically comprising the following steps: 800g of levodopa was weighed and added to 3L of anhydrous dimethyl sulfoxide solvent. The mixture was ultrasonically dispersed at 200W for 20 minutes to obtain a dispersion. 400g of EDC hydrochloride and 200g of N-hydroxysuccinimide were then weighed and added to the dispersion. The pH was then adjusted to 5.5 with dilute hydrochloric acid. The temperature was then controlled to 20°C and the mixture was stirred at 400r / min for 30 minutes for pre-activation. After the pre-activation, the pH was adjusted to 7.0 with aqueous ammonia. 200g of the Schiff base derivative obtained in Preparation Example 3 was added and mixed and stirred. The mixture was heated to 30°C and reacted for 12 hours. After the reaction, anhydrous ethanol was added, mixed and stirred, and the precipitate was collected by centrifugation. The precipitate was rinsed with anhydrous ethanol and then rinsed with deionized water until the rinse water became neutral. Finally, the mixture was dried in a vacuum drying oven at 60°C to obtain a modified catechol derivative. 50 g of the modified catechol derivative was weighed and added to 4 L of Tris-hydrochloric acid buffer with a pH of 8.5. 1 g of a mixed emulsifier (composed of Span 60 and sodium lauryl sulfate in a weight ratio of 1:0.5) and 100 g of nanosulfur (particle size of 50 nm) were then added and mixed. The mixture was then stirred at 600 rpm for 30 min while controlling the temperature at 25°C. After emulsification, the speed was reduced to 500 rpm, and the mixture was stirred for a cross-linking reaction for 20 h to obtain a microcapsule suspension. 10 parts by weight of microcapsule suspension, 0.2 parts by weight of polypropylene chopped fibers and 0.02 parts of azobisisobutyronitrile were weighed and mixed, heated to 70° C., and stirred at a speed of 400 r / min for 3 hours. After the reaction was completed, it was naturally cooled to room temperature, and the precipitate was collected by centrifugation to obtain a concrete cementitious composite material.

[0034] Comparative Example 1: A method for preparing a concrete cementitious composite material containing nano-sulfur, specifically comprising the following steps: The Schiff base derivative in Example 3 was replaced by the Schiff base derivative obtained in Preparation Example 4, and the rest of the preparation process remained the same as in Example 3.

[0035] Comparative Example 2: A method for preparing a concrete cementitious composite material containing nano-sulfur, specifically comprising the following steps: The Schiff base derivative in Example 3 was replaced by the Schiff base derivative obtained in Preparation Example 5, and the rest of the preparation process remained the same as in Example 3.

[0036] Comparative Example 3: A method for preparing a concrete cementitious composite material containing nano-sulfur, specifically comprising the following steps: The levodopa in Example 3 was replaced by dopamine hydrochloride, and the rest of the preparation process was consistent with that of Example 3.

[0037] Comparative Example 4: A method for preparing a concrete cementitious composite material containing nano-sulfur, specifically comprising the following steps: The nano-sulfur in Example 3 was replaced with nano-sulfur with a particle size of 90 nm, and the rest of the preparation process was consistent with Example 3.

[0038] Comparative Example 5: A method for preparing a concrete cementitious composite material containing nano-sulfur, specifically comprising the following steps: 800 g of levodopa was weighed and added to 3 L of anhydrous dimethyl sulfoxide solvent, and the dispersion was obtained by ultrasonic dispersion treatment at a power of 200 W for 20 minutes. Then 400 g of EDC hydrochloride and 200 g of N-hydroxysuccinimide were weighed and added to the dispersion. The pH was then adjusted to 5.5 with dilute hydrochloric acid, and the temperature was controlled to 20°C. The mixture was stirred at a speed of 400 r / min for 30 minutes for pre-activation treatment. After the pre-activation treatment, the pH was adjusted to 8.0 with ammonia water, and 200 g of the Schiff base derivative obtained in Preparation Example 3 was added, mixed and stirred, and the temperature was raised to 30°C for a timed reaction of 12 hours. After the reaction, it was found that the product was too viscous to be further processed, and the preparation failed. This may be because in the amidation catalyzed by EDC and N-hydroxysuccinimide, although a neutral to weakly alkaline environment is conducive to the amidation, the presence of levodopa and the high dosage in this system favor the oxidative self-polymerization of levodopa, thereby forming a highly viscous product that cannot be separated for the next step of processing.

[0039] The concrete cementitious composite materials obtained in Examples 1-3 and Comparative Examples 1-4 were heated to 120°C for insulation. Sand was then preheated to 90°C and mixed with the insulated concrete cementitious composite material (the weight ratio of concrete cementitious composite material to sand was 3:7). The mixture was stirred at 120°C until completely degassed and then poured into a mold coated with an oil-based release agent. The resulting concrete blocks, which were naturally cooled, were subjected to mechanical property testing in accordance with GB / T 50081-2019 Standard for Test Methods for Physical and Mechanical Properties of Concrete. The test size was 100 mm × 100 mm × 100 mm. The results are shown in Table 1 below.

[0040] Table 1 Mechanical properties ; The following conclusions can be drawn from Table 1: (1) It can be found from Examples 1 to 3 that when the concrete cementitious composite material prepared by the present invention is used in concrete preparation, the mechanical properties of the formed concrete are good.

[0041] (2) It can be found from Comparative Example 1 that when the prepared concrete cementitious composite material is used in concrete preparation, the mechanical properties of the formed concrete are poor. This may be because in this system, during the mixing and preparation of concrete, the concrete cementitious composite material containing nanosulfur needs to be heated in advance to melt the sulfur. Although trans-2-hexenal can form a high-temperature resistant imine bond, since its structure does not contain a high-temperature resistant benzene ring, it only relies on the high-temperature resistance of the imine bond. When it melts at high temperature, the high temperature and high alkalinity in the concrete easily causes the imine bond to break quickly, thereby causing the nanosulfur to seep out early, which is not conducive to mixing with cement, sand, etc., and thus the mechanical properties of the prepared concrete are poor.

[0042] (3) It can be found from Comparative Example 2 that when the prepared concrete cementitious composite material is used in concrete preparation, the mechanical properties of the formed concrete are poor. This may be because in this system, 1,6-hexanediamine has a longer carbon chain than 1,3-propylenediamine. The excessively long carbon chain may hinder the close stacking of benzene ring molecules in the spatial structure, affecting the intermolecular force, thereby weakening the high-temperature stability of the nanosulfur coating system during high-temperature mixing of concrete, making it easy for nanosulfur to seep out prematurely, which is not conducive to mixing with cement, sand, and gravel, thereby making the mechanical properties of the prepared concrete poor.

[0043] (4) It can be found from Comparative Example 3 that the mechanical properties of the prepared concrete cementitious composite material are poor when used in concrete preparation. This may be because in this system, although dopamine hydrochloride can also be oxidized and self-polymerized in an alkaline environment to form a polydopamine structure to wrap nanosulfur, dopamine hydrochloride does not have a carboxyl functional group that can be used for condensation and amidation with the amino group on the Schiff base derivative. As a result, the prepared modified catechol derivative does not have a carbon-carbon double bond that can be polymerized with polypropylene short fibers, which in turn makes it impossible to introduce polypropylene short fibers into the modified catechol derivative. Relying solely on the bonding and condensation effect of nanosulfur, the mechanical properties of concrete are poorly improved.

[0044] (5) It can be found from Preparation Example 4 that the mechanical properties of the prepared concrete cementitious composite material are poor when used in concrete preparation. This may be because in this system, the alkaline oxidation self-polymerization of levodopa containing a catechol structure to wrap the nanosulfur has a poor wrapping effect on larger particles, which is easy to break quickly during the concrete heating and mixing stage, affecting the mixing and dispersion effect, resulting in poor mechanical properties of the final prepared concrete.

[0045] The embodiments described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A method for preparing a concrete cementitious composite material containing nano-sulfur, characterized in that: The preparation method comprises the following steps: The Schiff base derivative, the catechol derivative, EDC hydrochloride and N-hydroxysuccinimide are mixed and reacted in a weight ratio of 1:3-4:1.5-2:1 to obtain a modified catechol derivative; The modified catechol derivative and nano-sulfur are mixed, dispersed and emulsified in a weight ratio of 0.3-0.5:1, and then cross-linked to obtain a microcapsule suspension; The microcapsule suspension, polypropylene fiber and initiator are mixed and polymerized according to a weight ratio of 10:0.1-0.2:0.01-0.02 to obtain a concrete cementitious composite material.

2. The method for preparing a nano-sulfur-containing concrete cementitious composite material according to claim 1, characterized in that: The preparation method of the Schiff base derivative comprises the following steps: The enal derivative, the diamine cross-linking agent, the anhydrous ethanol and the acetic acid are mixed in a weight ratio of 2-3:1:18-24:0.2-0.3, and heated to react to obtain the Schiff base derivative.

3. The method for preparing a nano-sulfur-containing concrete cementitious composite material according to claim 2, characterized in that: The enal derivatives include cinnamaldehyde.

4. The method for preparing a nano-sulfur-containing concrete cementitious composite material according to claim 2, wherein: The conditions for the mixed heating reaction include a temperature of 60° C. to 70° C. and a reaction time of 3 h to 5 h.

5. The method for preparing a nano-sulfur-containing concrete cementitious composite material according to claim 1, characterized in that: The catechol derivatives include levodopa.

6. The method for preparing a nano-sulfur-containing concrete cementitious composite material according to claim 1, characterized in that: The mixed reaction process of the Schiff base derivative, catechol derivative, EDC hydrochloride and N-hydroxysuccinimide includes pre-activation treatment for 30 minutes in an environment with a pH of 5.5 and a temperature of 20°C, and then reaction for 8 hours to 12 hours in an environment with a pH of 7.0 and a temperature of 30°C.

7. The method for preparing a nano-sulfur-containing concrete cementitious composite material according to claim 1, characterized in that: The mixing, dispersing and emulsifying conditions include mixing an emulsifier, a rotation speed of 600 r / min and an emulsification time of 20 min to 30 min.

8. The method for preparing a nano-sulfur-containing concrete cementitious composite material according to claim 1, characterized in that: The conditions of the cross-linking reaction include a reaction pH of 8.0-8.5, a reaction temperature of 25° C., a stirring speed of 400 r / min-500 r / min, and a reaction time of 18 h-20 h.

9. The method for preparing a nano-sulfur-containing concrete cementitious composite material according to claim 1, characterized in that: The conditions for the mixed polymerization include a rotation speed of 400 r / min, a reaction temperature of 65° C. to 70° C., and a reaction time of 2 h to 3 h.

10. A concrete cementitious composite material obtained by the method for preparing a concrete cementitious composite material containing nano-sulfur according to any one of claims 1 to 9.