A nano-sulfur-containing concrete cement composite material and a preparation method thereof

Abstract

The application discloses a concrete gel composite material containing nano sulfur and a preparation method thereof, and belongs to the technical field of concrete additive preparation. A modified catechol derivative is obtained by mixing and reacting a Schiff base derivative, a catechol derivative, EDC hydrochloride and N-hydroxysuccinimide; a microcapsule suspension is obtained by mixing, dispersing and emulsifying the modified catechol derivative and nano sulfur and then performing cross-linking reaction; and the concrete gel composite material is obtained by mixing and polymerizing the microcapsule suspension, polypropylene fibers and an initiator. The modified catechol derivative is obtained by mixing and reacting the Schiff base derivative and the catechol derivative with the catechol structure; the microcapsule suspension wrapping the nano sulfur is obtained by mixing the modified catechol derivative with the nano sulfur and then performing alkaline oxidation self-polymerization; and the concrete gel composite material containing the nano sulfur is obtained by mixing and reacting the polypropylene fibers and the microcapsule suspension.

Description

Technical Field

[0001] This invention belongs to the field of concrete additive preparation technology, specifically relating to a concrete cementitious composite material containing nano-sulfur and its preparation method. Background Technology

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

[0003] In order to improve the impermeability of concrete, various methods and technologies have been adopted in the current construction, 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 and the porosity can be reduced, thereby effectively improving the impermeability; (2) Using high-performance cement: Selecting cement with good impermeability, such as slag cement and fly ash cement, 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: A reasonable aggregate gradation can improve the density of concrete, reduce porosity, form a better filling effect, and thus improve impermeability; (4) Add admixtures: The use of admixtures can significantly improve the impermeability of concrete, such as water-reducing agents (which can reduce the amount of water used and lower the water-cement ratio, thereby enhancing the density of concrete), air-entraining agents (which introduce tiny air bubbles into concrete, thereby improving the freeze-thaw resistance of concrete and reducing 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 water tanks. (6) Curing: Good curing measures can promote the hydration reaction of concrete, enhance its structural density, and thus improve impermeability.

[0004] Sulfur concrete is a novel thermoplastic building material that uses sulfur as a binding agent to bind mineral fillers, aggregates, and other raw materials together. Due to sulfur's excellent binding properties, sulfur concrete has low water absorption and is not easily eroded or penetrated, making its application in the field of concrete impermeability promising. However, because sulfur often needs to be melted before use during construction, it leads to excessive volume shrinkage upon cooling, easily causing cracks and brittle fracture, thus weakening the performance of sulfur concrete. Therefore, existing technologies pre-treat sulfur before applying it to concrete preparation to improve its performance.

[0005] Patent CN118530001A discloses an asphalt mixture based on water-damage-resistant modified sulfur and its preparation method. This invention involves polymerizing sulfur with sodium lignosulfonate under high-temperature conditions, causing small sulfur molecules to form large molecular chains. Simultaneously, sodium lignosulfonate has surface-active properties, which can reduce the surface tension of water. After the modified sulfur asphalt mortar is fully mixed with aggregates, the modified sulfur asphalt mortar adheres to 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 lignosulfonate, the water stability, mechanical properties and high-temperature properties of the asphalt mixture can be improved simultaneously.

[0006] Patent CN117447161A discloses a pavement material containing composite modified asphalt, its preparation method and application. This invention obtains a sulfur / SBS / terpene resin modified asphalt with good crack resistance stability by melting and mixing asphalt, SBS, sulfur and terpene resin, thereby giving asphalt concrete good stability.

[0007] Due to its powdery nature and fine particle size, sulfur is prone to agglomeration during direct mixing and modification, resulting in poor modification effects. Therefore, it is of great significance to improve the agglomeration property of sulfur and thus modify it so that it can be mixed with materials used to prepare concrete with good performance. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention first reacts a Schiff base derivative with a catechol derivative having a catechol structure to obtain a modified catechol derivative. Then, the modified catechol derivative is mixed with nano-sulfur and subjected to alkaline oxidation and self-polymerization to obtain a microcapsule suspension encapsulating nano-sulfur. Next, polypropylene fibers are mixed with the microcapsule suspension to obtain a concrete cementitious composite material containing nano-sulfur, thereby solving the technical problems mentioned in the background art. Specifically, the technical solution of this invention includes the following:

[0009] A method for preparing a concrete cementitious composite material containing nano-sulfur, the method comprising the following steps:

[0010] A modified catechol derivative was obtained by mixing Schiff base derivatives, catechol derivatives, EDC hydrochloride and N-hydroxysuccinimide in a weight ratio of 1:3~4:1.5~2:1.

[0011] Modified catechol derivatives and nano-sulfur were mixed, dispersed, emulsified, and then cross-linked to obtain microcapsule suspensions.

[0012] A concrete cementitious composite material is obtained by mixing and polymerizing microcapsule suspension, polypropylene fiber and initiator in a weight ratio of 10:0.1~0.2:0.01~0.02.

[0013] Furthermore, the preparation method of the Schiff base derivative includes the following steps:

[0014] Schiff base derivatives are obtained by mixing and heating an aldehyde derivative, a diamine crosslinking agent, anhydrous ethanol and acetic acid in a weight ratio of 2~3:1:18~24:0.2~0.3.

[0015] Furthermore, the enaldehyde derivative includes cinnamaldehyde, and the enaldehyde derivative needs to contain a benzene ring in its structure to jointly improve high-temperature stability.

[0016] Furthermore, the diamine crosslinking agent includes propylenediamine.

[0017] Furthermore, the conditions for the mixed heating reaction include a temperature of 60°C to 70°C and a reaction time of 3 to 5 hours.

[0018] Furthermore, the catechol derivative includes levodopa.

[0019] Furthermore, the mixed reaction process of the Schiff base derivative, catechol derivative, EDC hydrochloride and N-hydroxysuccinimide includes a pre-activation treatment of 30 min in an environment with pH 5.5 and temperature 20°C, followed by a reaction in an environment with pH 7.0 and temperature 30°C for 8 h to 12 h.

[0020] Furthermore, the particle size of the nano-sulfur is 50 nm.

[0021] Furthermore, the conditions for the mixed dispersion emulsification include mixing emulsifiers, a rotation speed of 600 r / min, and an emulsification time of 20 min to 30 min.

[0022] Furthermore, the mixed emulsifier is composed of Span 60 and sodium dodecyl sulfate in a weight ratio of 1:0.5.

[0023] Furthermore, the conditions for the crosslinking reaction include a reaction pH of 8.0 to 8.5, a reaction temperature of 25°C, a stirring speed of 400 r / min to 500 r / min, and a reaction time of 18 h to 20 h.

[0024] Furthermore, the polypropylene fiber is chopped polypropylene fiber.

[0025] Furthermore, the initiator includes azobisisobutyronitrile.

[0026] Furthermore, the conditions for the mixed polymerization include a rotation speed of 400 r / min, a reaction temperature of 65℃~70℃, and a reaction time of 2h~3h.

[0027] The second objective of this invention is to provide a concrete cementitious composite material obtained by a method for preparing a concrete cementitious composite material containing nano-sulfur.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] This invention first reacts an enaldehyde derivative containing a benzene ring structure with a diamine crosslinking agent. The enaldehyde derivative and the diamine crosslinking agent form a high-temperature resistant imine bond structure through the condensation of the aldehyde and amino groups, thus obtaining a Schiff base derivative. The Schiff base derivative is then mixed with a catechol derivative containing a catechol structure. An amidation condensation reaction occurs between the amino group on the Schiff base derivative and the carboxyl group on the catechol derivative, thereby introducing a high-temperature resistant imine bond structure and a carbon-carbon double bond structure onto the side chain of the catechol derivative, resulting in a modified catechol derivative. Next, utilizing the mechanism of molecular biomimetic, the modified catechol derivative and nano-sulfur are ultrasonically mixed and dispersed to form a mixed emulsion. The mixed emulsion is adjusted to a weakly alkaline environment, causing the L-DOPA containing the catechol structure to oxidatively self-polymerize and form a poly-L-DOPA structure with adhesive properties, thereby encapsulating the nano-sulfur and obtaining a microcapsule suspension encapsulating nano-sulfur. Polypropylene fibers, which can reduce plastic cracking in concrete, are then mixed with microcapsule suspensions. An initiator catalyzes the reaction of the two fibers through carbon-carbon double bonds, resulting in a concrete cementitious composite material containing nano-sulfur. The imine bonds and benzene ring structures in the concrete cementitious composite material improve its stability during high-temperature heating, preventing premature leaching of the nano-sulfur and ensuring its uniform dispersion. Introducing polypropylene fibers into the concrete cementitious composite material via initiated polymerization allows the fibers, which are difficult to integrate with the concrete interface, to be better incorporated into the concrete. The synergistic effect of the polypropylene fibers and nano-sulfur improves the mechanical properties and impermeability of the concrete prepared using the concrete cementitious composite material of this invention. Detailed Implementation

[0030] The technical solution of the present invention will be clearly and completely described below through embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Unless otherwise stated, all raw materials and reagents used in this invention are commercially available or can be prepared by known methods.

[0032] Nano-sulfur was purchased from Zhejiang Yamei Nanotechnology Co., Ltd.

[0033] The polypropylene chopped fibers were purchased from Zibo Baina New Material Technology Co., Ltd.

[0034] Preparation Example 1:

[0035] The preparation method of Schiff base derivatives specifically includes the following steps:

[0036] 200g of cinnamaldehyde and 1800g of anhydrous ethanol were weighed and added to a reactor, and mixed and stirred at 100 rpm until homogeneous. Then, 100g of 1,3-propanediamine was weighed and added to the reactor, and mixing and stirring were continued until homogeneous. Finally, 20g of acetic acid (molar concentration 0.01mol / L) was added as an auxiliary catalyst. At this point, the stirring speed was increased to 200 rpm, and the temperature was raised to 60℃, and the reaction was timed for 3 hours. After the reaction was completed, the anhydrous ethanol was evaporated under reduced pressure, and after cooling to room temperature, the filter cake was obtained by vacuum filtration. The filter cake was washed with anhydrous ethanol and then dried under vacuum at 55℃ to obtain Schiff base derivatives.

[0037] Preparation Example 2:

[0038] The preparation method of Schiff base derivatives specifically includes the following steps:

[0039] 250g of cinnamaldehyde and 2000g of anhydrous ethanol were weighed and added to a reactor, and mixed and stirred at 100 rpm until homogeneous. Then, 100g of 1,3-propanediamine was weighed and added to the reactor, and mixing and stirring were continued until homogeneous. Finally, 25g of acetic acid (0.01mol / L) was added as an auxiliary catalyst. At this point, the stirring speed was increased to 200 rpm, and the temperature was raised to 65℃, and the reaction was timed for 4 hours. After the reaction was completed, the anhydrous ethanol was evaporated under reduced pressure, and after cooling to room temperature, the filter cake was obtained by vacuum filtration. The filter cake was washed with anhydrous ethanol and then dried under vacuum at 55℃ to obtain Schiff base derivatives.

[0040] Preparation Example 3:

[0041] The preparation method of Schiff base derivatives specifically includes the following steps:

[0042] 300g of cinnamaldehyde and 2400g of anhydrous ethanol were weighed and added to a reactor, and mixed and stirred at 100 rpm until homogeneous. Then, 100g of 1,3-propanediamine was weighed and added to the reactor, and mixing and stirring were continued until homogeneous. Finally, 30g of acetic acid (molar concentration of 0.01mol / L) was added as an auxiliary catalyst. At this point, the stirring speed was increased to 200 rpm, and the temperature was raised to 70℃, and the reaction was timed for 5 hours. After the reaction was completed, the anhydrous ethanol was evaporated under reduced pressure, and after cooling to room temperature, the filter cake was obtained by vacuum filtration. The filter cake was washed with anhydrous ethanol and then dried under vacuum at 55℃ to obtain Schiff base derivatives.

[0043] Preparation Example 4:

[0044] The preparation method of Schiff base derivatives specifically includes the following steps:

[0045] 300g of trans-2-hexenal and 2400g of anhydrous ethanol were weighed and added to a reactor, and mixed and stirred at 100 rpm until homogeneous. Then, 100g of 1,3-propanediamine was weighed and added to the reactor, and mixing and stirring were continued until homogeneous. Finally, 30g of acetic acid (0.01mol / L) was added as an auxiliary catalyst. At this point, the stirring speed was increased to 200 rpm, and the temperature was raised to 70℃, and the reaction was timed for 5 hours. After the reaction was completed, the anhydrous ethanol was evaporated under reduced pressure, and after cooling to room temperature, the filter cake was obtained by vacuum filtration. The filter cake was washed with anhydrous ethanol and then dried under vacuum at 55℃ to obtain the Schiff base derivative.

[0046] Preparation Example 5:

[0047] The preparation method of Schiff base derivatives specifically includes the following steps:

[0048] 300g of cinnamaldehyde and 2400g of anhydrous ethanol were weighed and added to a reactor, and mixed and stirred at 100 rpm until homogeneous. Then, 100g of 1,6-hexanediamine was weighed and added to the reactor, and mixing and stirring were continued until homogeneous. Finally, 30g of acetic acid (molar concentration 0.01mol / L) was added as an auxiliary catalyst. At this point, the stirring speed was increased to 200 rpm, and the temperature was raised to 70℃, and the reaction was timed for 5 hours. After the reaction was completed, the anhydrous ethanol was evaporated under reduced pressure, and after cooling to room temperature, the filter cake was obtained by vacuum filtration. The filter cake was washed with anhydrous ethanol and then dried under vacuum at 55℃ to obtain Schiff base derivatives.

[0049] Example 1: A method for preparing a concrete cementitious composite material containing nano-sulfur, specifically including the following steps:

[0050] 600g of levodopa was weighed and added to 3L of anhydrous dimethyl sulfoxide solvent. The mixture was dispersed using ultrasound at 200W for 20min to obtain a dispersion. Then, 300g of EDC hydrochloride and 200g of N-hydroxysuccinimide were weighed and added to the dispersion. The pH was adjusted to 5.5 with dilute hydrochloric acid, and the temperature was controlled at 20℃. Pre-activation was performed by stirring continuously at 400r / min for 30min. After pre-activation, the pH was adjusted to 7.0 with ammonia. Then, 200g of the Schiff base derivative obtained in Preparation Example 1 was added, mixed, and stirred. The mixture was heated to 30℃ and reacted for 8h. After the reaction, anhydrous ethanol was added, mixed, stirred, and centrifuged to collect the precipitate. The precipitate was washed with anhydrous ethanol, then with deionized water until the wash water was neutral. Finally, it was dried in a vacuum drying oven at 60℃ to obtain the modified catechol derivative.

[0051] Weigh 30g of modified catechol derivative and add it to 4L of Tris-hydrochloric acid buffer at pH 8.0. Then add 1g of mixed emulsifier (composed of Span 60 and sodium dodecyl sulfate in a weight ratio of 1:0.5) and 100g of nano sulfur (particle size of 50nm). Then control the temperature at 25℃ and stir emulsify at 600r / min for 20min. After emulsification, reduce the speed to 400r / min and stir the crosslinking reaction for 18h to obtain the microcapsule suspension.

[0052] Weigh 10 parts by weight of microcapsule suspension, 0.1 parts by weight of chopped polypropylene fibers and 0.01 parts by weight of azobisisobutyronitrile, mix them, heat to 65°C, stir at 400 r / min for 2 h, after the reaction is completed, let cool naturally to room temperature, centrifuge to separate and collect the precipitate to obtain concrete cementitious composite material.

[0053] Example 2, a method for preparing a concrete cementitious composite material containing nano-sulfur, specifically includes the following steps:

[0054] 700g of levodopa was weighed and added to 3L of anhydrous dimethyl sulfoxide solvent. The mixture was dispersed using ultrasound at 200W for 20min to obtain a dispersion. Then, 350g of EDC hydrochloride and 200g of N-hydroxysuccinimide were weighed and added to the dispersion. The pH was adjusted to 5.5 with dilute hydrochloric acid, and the temperature was controlled at 20℃. Pre-activation was performed by stirring continuously at 400r / min for 30min. After pre-activation, the pH was adjusted to 7.0 with ammonia. Then, 200g of the Schiff base derivative obtained in Preparation Example 2 was added, mixed, and stirred. The mixture was heated to 30℃ and reacted for 10h. After the reaction, anhydrous ethanol was added, mixed, stirred, and centrifuged to collect the precipitate. The precipitate was washed with anhydrous ethanol, then with deionized water until the wash water was neutral. Finally, it was dried in a vacuum drying oven at 60℃ to obtain the modified catechol derivative.

[0055] 40g of modified catechol derivative was weighed and added to 4L of Tris-hydrochloric acid buffer at pH 8.5. Then, 1g of mixed emulsifier (composed of Span 60 and sodium dodecyl sulfate in a weight ratio of 1:0.5) and 100g of nano sulfur (particle size of 50nm) were added and mixed. The temperature was controlled at 25℃, and then the mixture was stirred and emulsified at 600r / min for 25min. After emulsification, the stirring speed was reduced to 400r / min and the crosslinking reaction was stirred for 19h to obtain the microcapsule suspension.

[0056] Weigh 10 parts by weight of microcapsule suspension, 0.15 parts by weight of polypropylene short chopped fiber and 0.015 parts by weight of azobisisobutyronitrile and mix them. Heat the mixture to 70°C and stir it at 400 r / min for 2.5 h. After the reaction is completed, let it cool to room temperature naturally and centrifuge to collect the precipitate to obtain concrete cementitious composite material.

[0057] Example 3, a method for preparing a concrete cementitious composite material containing nano-sulfur, specifically includes the following steps:

[0058] 800g of levodopa was weighed and added to 3L of anhydrous dimethyl sulfoxide solvent. The mixture was dispersed using ultrasound at 200W for 20min to obtain a dispersion. Then, 400g of EDC hydrochloride and 200g of N-hydroxysuccinimide were weighed and added to the dispersion. The pH was adjusted to 5.5 with dilute hydrochloric acid, and the temperature was controlled at 20℃. Pre-activation was performed by stirring continuously at 400r / min for 30min. After pre-activation, the pH was adjusted to 7.0 with ammonia. Then, 200g of the Schiff base derivative obtained in Preparation Example 3 was added, mixed, and stirred. The mixture was heated to 30℃ and reacted for 12h. After the reaction, anhydrous ethanol was added, mixed, stirred, and centrifuged to collect the precipitate. The precipitate was washed with anhydrous ethanol, then with deionized water until the wash water was neutral. Finally, it was dried in a vacuum drying oven at 60℃ to obtain the modified catechol derivative.

[0059] Weigh 50g of modified catechol derivative and add it to 4L of Tris-hydrochloric acid buffer at pH 8.5. Then add 1g of mixed emulsifier (composed of Span 60 and sodium dodecyl sulfate in a weight ratio of 1:0.5) and 100g of nano sulfur (particle size of 50nm). Then control the temperature at 25℃ and stir emulsify at 600r / min for 30min. After emulsification, reduce the speed to 500r / min and stir the crosslinking reaction for 20h to obtain the microcapsule suspension.

[0060] Weigh 10 parts by weight of microcapsule suspension, 0.2 parts by weight of chopped polypropylene fibers and 0.02 parts by weight of azobisisobutyronitrile, mix them, heat to 70°C, stir at 400 r / min for 3 h, and after the reaction is completed, let it cool to room temperature naturally, centrifuge to separate and collect the precipitate to obtain concrete cementitious composite material.

[0061] Comparative Example 1:

[0062] A method for preparing a concrete cementitious composite material containing nano-sulfur specifically includes the following steps:

[0063] The Schiff base derivative in Example 3 was replaced with the Schiff base derivative obtained in Preparation Example 4, and the rest of the preparation process was the same as in Example 3.

[0064] Comparative Example 2:

[0065] A method for preparing a concrete cementitious composite material containing nano-sulfur specifically includes the following steps:

[0066] The Schiff base derivative in Example 3 was replaced with the Schiff base derivative obtained in Preparation Example 5, and the rest of the preparation process was the same as in Example 3.

[0067] Comparative Example 3:

[0068] A method for preparing a concrete cementitious composite material containing nano-sulfur specifically includes the following steps:

[0069] In Example 3, L-DOPA was replaced with dopamine hydrochloride, and the rest of the preparation process remained the same as in Example 3.

[0070] Comparative Example 4:

[0071] A method for preparing a concrete cementitious composite material containing nano-sulfur specifically includes the following steps:

[0072] 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 the same as in Example 3.

[0073] Comparative Example 5:

[0074] A method for preparing a concrete cementitious composite material containing nano-sulfur specifically includes the following steps:

[0075] 800g of levodopa was weighed and added to 3L of anhydrous dimethyl sulfoxide solvent. The mixture was dispersed by ultrasonic power of 200W for 20min to obtain a dispersion. Then, 400g of EDC hydrochloride and 200g 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 at 20℃. The mixture was stirred continuously at 400r / min for 30min for pre-activation treatment. After the pre-activation treatment, the pH was adjusted to 8.0 with ammonia water. Then, 200g of the Schiff base derivative obtained in Preparation Example 3 was added, mixed and stirred, and the temperature was raised to 30℃ for 12h. After the reaction, it was found that the product was too viscous and could not be further processed, resulting in preparation failure. This may be because, in the amidation catalyzed by EDC and N-hydroxysuccinimide, although a neutral to weakly basic environment is conducive to amidation, the presence of L-DOPA in this system and its high dosage led to a weakly basic environment that favored the oxidative self-polymerization of L-DOPA, resulting in a highly viscous product that could not be separated for further processing.

[0076] The concrete cementitious composite materials obtained in Examples 1-3 and Comparative Examples 1-4 were heated to 120°C and kept at that temperature. Then, the sand was preheated to 90°C and mixed with the preheated 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. After natural cooling, the resulting concrete blocks were tested for mechanical properties according to the "GB / T 50081-2019 Standard for Test Methods of Physical and Mechanical Properties of Concrete". The test size was 100mm×100mm×100mm. The results are shown in Table 1 below.

[0077] Table 1 Mechanical Properties

[0078] ;

[0079] The following conclusions can be drawn from Table 1 above:

[0080] (1) As can be seen from Examples 1 to 3, the concrete cementitious composite material prepared by the present invention exhibits good mechanical properties when applied to concrete preparation.

[0081] (2) Comparative Example 1 shows that when the prepared concrete cementitious composite material is applied to concrete preparation, the mechanical properties of the molded concrete are poor. This may be because in this system, the concrete cementitious composite material containing nano-sulfur needs to be heated in advance during the mixing and preparation process to melt the sulfur. Although trans-2-hexenal can form high-temperature resistant imine bonds, since the structure does not contain a high-temperature resistant benzene ring, it relies solely on the high-temperature resistance of the imine bonds. When melting at high temperature, the high temperature and high alkalinity in the concrete can easily cause the imine bonds to break quickly, which in turn causes the nano-sulfur to seep out early, which is not conducive to mixing with cement, sand and gravel, etc., and thus the mechanical properties of the prepared concrete are poor.

[0082] (3) Comparative Example 2 shows that when the prepared concrete cementitious composite material is applied to concrete preparation, the mechanical properties of the molded concrete are poor. This may be because in this system, 1,6-hexanediamine has a longer carbon chain than 1,3-propanediamine. The excessively long carbon chain may hinder the close packing of benzene ring molecules in the spatial structure, affecting the intermolecular forces, thereby weakening the high-temperature stability of the nano-sulfur-encapsulated system when the concrete is mixed at high temperature. This makes it easy for the nano-sulfur to seep out early, which is not conducive to mixing with cement, sand and gravel, etc., thus resulting in poor mechanical properties of the prepared concrete.

[0083] (4) Comparative Example 3 shows that when the prepared concrete cementitious composite material is applied to concrete preparation, the mechanical properties of the formed concrete are poor. 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 encapsulate nano-sulfur, there are no carboxyl functional groups on dopamine hydrochloride that can be used for amino condensation and amidation with Schiff base derivatives. As a result, the modified catechol derivatives prepared do not have carbon-carbon double bonds that can be polymerized with polypropylene short-cut fibers. Consequently, polypropylene short-cut fibers cannot be introduced into the modified catechol derivatives. Relying solely on the bonding and coagulation effect of nano-sulfur, the mechanical properties of concrete are poorly improved.

[0084] (5) It can be seen from the preparation example 4 that when the prepared concrete cementitious composite material is applied to the preparation of concrete, the mechanical properties of the molded concrete are poor. This may be because in this system, the alkaline oxidative self-polymerization of L-DOPA containing catechol structure to encapsulate nano-sulfur has a poor encapsulation effect on larger particle sizes. It is easy to break quickly during the concrete heating and mixing stage, which affects the mixing and dispersion effect, resulting in poor mechanical properties of the final prepared concrete.

[0085] The embodiments described above provide a detailed explanation 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 can be made to the present invention without departing from its spirit and scope, and all 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 includes the following steps: A modified catechol derivative was obtained by mixing Schiff base derivatives, catechol derivatives, EDC hydrochloride and N-hydroxysuccinimide in a weight ratio of 1:3~4:1.5~2:

1. Modified catechol derivatives and nano-sulfur were mixed, dispersed, emulsified, and then cross-linked to obtain microcapsule suspensions. Microcapsule suspension, polypropylene fiber, and initiator were mixed and polymerized in a weight ratio of 10:0.1~0.2:0.01~0.02 to obtain a concrete cementitious composite material; The catechol derivative is levodopa; The nano-sulfur has a particle size of 50 nm.

2. The method for preparing a concrete cementitious composite material containing nano-sulfur according to claim 1, characterized in that, The preparation method of the Schiff base derivative includes the following steps: Schiff base derivatives are obtained by mixing and heating an aldehyde derivative, a diamine crosslinking agent, anhydrous ethanol and acetic acid in a weight ratio of 2~3:1:18~24:0.2~0.

3.

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

4. The method for preparing a concrete cementitious composite material containing nano-sulfur according to claim 2, characterized in that, The conditions for the mixed heating reaction include a temperature of 60℃~70℃ and a reaction time of 3h~5h.

5. The method for preparing a concrete cementitious composite material containing nano-sulfur according to claim 1, characterized in that, The process of mixing Schiff base derivatives, catechol derivatives, EDC hydrochloride and N-hydroxysuccinimide involves pre-activation treatment for 30 min at pH 5.5 and temperature 20°C, followed by reaction at pH 7.0 and temperature 30°C for 8 h to 12 h.

6. The method for preparing a concrete cementitious composite material containing nano-sulfur according to claim 1, characterized in that, The conditions for the mixed dispersion emulsification include mixing emulsifiers, rotating speed of 600 r / min, and emulsification time of 20 min to 30 min.

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

8. The method for preparing a concrete cementitious composite material containing nano-sulfur 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℃~70℃, and a reaction time of 2h~3h.

9. A concrete cementitious composite material obtained by the preparation method of a concrete cementitious composite material containing nano-sulfur as described in any one of claims 1 to 8.