A cement enhancing additive and its use in cementitious materials

Abstract

The application provides a cement reinforcing additive, which comprises an organic component and a modified inorganic component in a weight ratio of 1:(0.5-5); the organic component is an organic monomer containing an unsaturated double bond; the modified inorganic component is obtained by modifying an inorganic component capable of participating in a hydration product formation process by a polymerizable siloxane; the cement reinforcing additive can be applied in the preparation of a cement-based material; and finally obtained cement-based material is a cement-based material internally constructed with an organic-inorganic hybrid network, compared with a traditional method of directly adding a polymer emulsion or fibers, the amount of the organic component is small, and the working performance of the cement-based material is not negatively affected, and even the working performance is improved under some conditions. Compared with the traditional method of adding inorganic nanoparticles or hybrid nanoparticles, the method can more effectively play the role of the nanoparticles in the cement-based material, that is, as a part of a bridging, connecting the hydration product and the organic component, and effectively improving the flexural strength.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, and in particular to a cement reinforcing additive and application thereof in cement-based materials. BACKGROUND

[0002] Cement-based composite materials have become the main building materials in the world due to their advantages of rich raw materials, low cost, high strength, simple production process, etc., and are widely used in civil buildings, roads, bridges, airports, ports and water conservancy, etc. However, cement-based composite materials are inhomogeneous porous brittle materials, when subjected to external load, stress is first concentrated at defects, nano cracks are generated at loose hydrated products and gradually expand into micron cracks, under the action of continuous load, micron cracks continuously expand and merge to form macro cracks, and then lead to brittle fracture. The existence of pores and cracks not only reduces the strength, but also induces problems such as permeation, harmful ions invade to reduce durability, increase maintenance cost and shorten service life. Therefore, strengthening cement-based composite materials has become one of the current research hotspots.

[0003] Studies have shown that by introducing some high-toughness materials, among which fiber and polymer emulsion are two materials that are more studied and applied. However, the fiber is not uniformly dispersed in the concrete mixing process, and is easy to agglomerate, resulting in poor workability and difficult pumping; in addition, since the fiber relies on the pull-out effect to limit the development of cracks in the toughening of concrete, the performance of fiber modified concrete is closely related to the dispersion and orientation of the fiber, so the stability of the fiber modified concrete is more difficult to control, and more aspects need to be paid attention to in actual use. However, the improvement of the flexural strength of the polymer emulsion modified concrete often needs to sacrifice the compressive strength of the cement-based material, for example, in the work reported by Farshad Farshchi Tabrizi in 2019, SBA modified concrete can improve the flexural strength by 22.6%, but the compressive strength decreases significantly. This decline is mainly due to the fact that traditional additives such as fiber and polymer emulsion are not active, neither participate in the hydration reaction nor promote the hydration process, and mainly rely on physical action, the role in the concrete is only related to its own physical properties. It has no modification effect on the microstructure of the concrete.

[0004] Patent CN 111517703 A discloses a high-flexural-strength cement-based material and its preparation method, relating to the field of concrete technology. The high-flexural-strength cement-based material includes cement hydrates and a polymer chemically bonded to the cement hydrates. The polymer is obtained by in-situ polymerization of monomers in cement under the action of an initiator and an accelerator. The preparation method of the high-flexural-strength cement-based material involves mixing and dissolving the monomers, initiator, and accelerator, and then performing in-situ polymerization in cement. The resulting polymer and cement hydrates are linked by chemical bonds, effectively improving the flexural strength of the cement-based material. However, this method has a significant impact on fluidity, thus limiting its application.

[0005] Patent CN 111363077 A discloses a polymer cement-based material, its preparation method, and its applications, belonging to the field of building materials technology. The preparation method includes: mixing an initiation system and a mixed solution of acrylate monomers with a cement-based material, and then subjecting the acrylate monomers to in-situ polymerization in the cement-based material to form another network interwoven with the cement hydration products, thereby obtaining an in-situ polymer cement-based material. This method is simple and convenient to operate. By carrying out in-situ polymerization of acrylate monomers in the cement-based system, the compatibility between the two networks of the polymer-based cement is ensured, resulting in a polymer cement-based material with interwoven network characteristics. The aforementioned polymer cement-based material exhibits high flexural strength without affecting compressive strength, and its setting time is adjustable. This polymer cement-based material can be used in 3D printing, dam construction, wall panels, or concrete pavement slabs, etc. However, this method is not conducive to industrial implementation in practical applications.

[0006] Patent CN114436597A discloses an in-situ synergistic modification and reinforcement of cement-based composite materials and its applications, belonging to the field of building materials technology. Its preparation method includes mixing cementitious materials, polymer monomers, initiators, crosslinking agents, and whiskers. The resulting product exhibits physical adsorption and weak ionic bonding between the polymer and whiskers. It enhances the flexural strength of cement-based materials and reduces the adverse effects of in-situ polymerization on the compressive strength of cement-based composite materials. However, it still has a negative impact on compressive strength, thus significantly affecting practical applications. Therefore, finding a chemically active reinforcing material that can interact more with concrete adhesives is of great significance for preparing high-strength, high-toughness, and long-life cement-based composite materials. Summary of the Invention

[0007] To address the problems of low toughness and low flexural strength in existing cement-based materials, this invention provides a cement reinforcing additive and its application in cement-based materials. When this cement reinforcing additive is applied to cement-based materials, the resulting cement-based material contains a uniformly distributed organic-inorganic hybrid network. The inorganic components are connected to the hydrated particles in the cement-based material, and the organic and inorganic components are linked by chemical bonds. This network is constructed in situ by adding modified inorganic components and polymeric monomers to cement under the action of an initiator. The presence of this organic-inorganic hybrid network can significantly improve the workability of cement-based materials before hardening and their mechanical properties (flexural and tensile strength) after hardening.

[0008] A cement reinforcing additive comprising an organic component and a modified inorganic component, wherein the weight fraction ratio of the organic component to the modified inorganic component is 1:(0.5-5).

[0009] The above organic components are at least one of the following general formulas (1)-(4):

[0010] Where R1 represents H, CH3, or CH3COOH, R2 represents H or an active metal ion; R3 represents H or CH3; R4 and R5 independently represent H, CH3, CH2CH3, CH2OH, CH2CH2OH, and CH2CHCH3OH, respectively; R6, R7, and R8 independently represent H or CH3, respectively; R9 represents an alkyl group with 4-30 carbon atoms; X1, X2, and X3 independently represent O or NH, respectively; a and b independently refer to the average repeating unit number of the ethoxy-CH2CH2O- chain segment, with values ​​ranging from 4 to 50;

[0011] The modified inorganic component is obtained by modifying an inorganic component that can participate in the hydration product generation process with a polymerizable siloxane; the particle size of the modified inorganic component is less than 76 μm.

[0012] The inorganic components mentioned above are selected from at least one of nano-SiO2, nano-CSH, cement, and nano-TiO2.

[0013] Preferably, the inorganic component is silicon dioxide or titanium dioxide.

[0014] The polymerizable siloxane structure described above contains at least one vinyl group, and the polymerizable siloxane is selected from at least one of vinyltrimethoxysilane (VTMS), vinyltriethoxysilane (VTES), methacryloxypropyltrimethoxysilane (MAPTMS), methacryloxypropyltriethoxysilane (MAPTES), methacryloxymethyltriethoxysilane (AAPTES), acryloyloxymethyltrimethoxysilane (AAMTMS), and acryloyloxypropyltrimethoxysilane (AAPTMS);

[0015] The molar ratio of the polymerizable siloxane to the inorganic component is (0.05-0.3):1.

[0016] The modified inorganic component was prepared by the following steps: the inorganic component was added to a solvent and stirred evenly, and then polymerizable siloxane and hydrochloric acid were added dropwise. After the reaction was completed, the modified inorganic component with a particle size of <76 μm was obtained by washing, drying and grinding.

[0017] The concentration of the polymerizable siloxane is 0.5-2%; the concentration of the hydrochloric acid is 1 mol / L, and the amount used is 0.5-2% of the mass of the inorganic component.

[0018] The above-mentioned polymerizable siloxane can be added under the following conditions: temperature 60℃, dropping rate 3ml / min; or it can be added in one drop. The choice of dropping method does not affect the reaction results. The concentration of the above-mentioned polymerizable siloxane is 0.5-3wt%.

[0019] The reaction conditions after the above addition were 60±0.5℃ for 1-2 hours, then the temperature was increased to 70-80℃ and maintained for 8-12 hours.

[0020] The washing process involved ultrasonic washing and centrifugation three times with ethanol and water, respectively; the drying conditions were vacuum drying at 90°C for 24 hours in a vacuum drying oven.

[0021] The application of the cement reinforcing additive described in claim 1, wherein the cement reinforcing additive is applied in the construction process of cement-based materials.

[0022] A cement-based material comprising the following components in parts by weight: 1-10 parts cement reinforcing additive, 0.002-0.1 parts initiator, 225 parts standard sand, 0.05-0.2 parts water-reducing agent, 100 parts cement, and 25-50 parts water; wherein the initiator is a free radical initiator, and the amount of the initiator is 0.1%-2.5% of the organic components in the cement reinforcing additive; wherein the cement reinforcing additive is the cement reinforcing additive as described in claim 1.

[0023] The free radical initiators mentioned above are thermal initiators or redox initiation systems of the medium temperature (30℃-100℃).

[0024] The aforementioned thermal initiator is at least one selected from azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, azobisisobutylamidine hydrochloride, ammonium persulfate, azobiscyanopentanoic acid, tetratert-butyl peroxide, benzoyl peroxide, and tert-butyl peroxide; the aforementioned redox initiation system consists of a persulfate or peroxide as an oxidant and a sulfite or organic amine as a reducing agent; the amount of the reducing agent is 50%-200% of the amount of the oxidant.

[0025] The oxidant mentioned above is at least one of hydrogen peroxide, ammonium persulfate, sodium persulfate, and potassium persulfate.

[0026] The reducing agent mentioned above is at least one of ferrous sulfate, oxalic acid, glucose, sodium sulfite, sodium bisulfite, sodium metabisulfite, triethanolamine, and triisopropanolamine.

[0027] A method for preparing a cement-based material involves mixing cement reinforcing additives with water to obtain a mixing liquid A, preparing an initiator into a mixing liquid B with a concentration of 0.02%-0.6%, and mixing the mixing liquid A, mixing liquid B, standard sand, water-reducing agent, and cement to obtain the cement-based material.

[0028] If the initiator is a redox initiation system, the reducing agent, cement reinforcing additive, and water are mixed and stirred evenly to obtain mixture A, and the oxidizing agent is prepared into mixture B for the preparation of cement-based materials.

[0029] The cement-based material ultimately obtained in this application is a cement-based material with an internally constructed organic-inorganic hybrid network. The cement-based material includes cement hydrate and an organic polymer network connected to the cement hydrate by chemical bonds. The organic polymer network is obtained by in-situ polymerization of organic components and modified inorganic components in cement reinforcing additives by an initiator in cement. The organic components are network-connected and unconnected modified inorganic components. The modified inorganic components are obtained by modifying inorganic components that can participate in the hydration product generation process with polymerizable siloxanes. The mass ratio of the cement hydrate, organic components, and modified inorganic components is 100:(0.5-5):(0.5-5).

[0030] The present invention has the following advantages over the prior art:

[0031] 1. The in-situ construction of a polymerization system in cement-based materials described in this invention differs from directly adding polymer emulsions. By adding cement reinforcing additives (organic components and modified inorganic components) to cement, an organic-inorganic hybrid network can be formed and uniformly distributed within the cement-based material. The modified inorganic components and hydrated particles in the cement-based material are linked to form modified cement. This network is constructed in-situ by adding modified cement and organic components under the action of an initiator. During this network construction process, the modified inorganic components first participate in the hydration process, introducing double-bonded functional groups onto the hydrated calcium silicate gel. Then, the double-bonded calcium silicate gel and organic components undergo free radical polymerization to form the organic-inorganic hybrid network. During this network construction process, the polymerization reaction is controlled to occur after the acceleration period of the hydration reaction by varying the initiator and monomer concentrations during the hydration process and by using temperature-sensitive initiators such as azo initiators or persulfates, thus avoiding the impact of pre-polymerization on hydration. Because this invention controls polymerization to occur after the acceleration period of hydration, it has a beneficial effect on the compressive strength of cement-based materials.

[0032] 2. The organic-inorganic hybrid network of the present invention uses modified inorganic components to connect cement hydration products and organic components through covalent bonds. The presence of this organic-inorganic hybrid network can significantly improve the workability of cement-based materials before hardening and their mechanical properties after hardening.

[0033] 3. Compared to traditional methods of directly adding polymer emulsions or fibers, this method requires less organic component and has no negative impact on the workability of cement-based materials; in fact, it may even improve workability under certain conditions. Compared to traditional methods of adding inorganic or hybrid nanoparticles, this method can more effectively utilize the role of nanoparticles in cement-based materials, acting as a bridging agent to connect hydration products and organic components, thereby effectively improving flexural strength. Attached Figure Description

[0034] Figure 1 The main morphology of the polymer network in the cement paste specimens of Examples 1, 1 Comparative Example 2, 3 Comparative Example 3, and 4 are shown in the performance test results.

[0035] Figure 2 SEM image of MS6 sample; Detailed Implementation

[0036] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] The general structural formulas and corresponding abbreviations of the organic components used in each embodiment are shown in Table 1 below:

[0038] Table 1

[0039]

[0040] Example 1

[0041] (1) Add 10 parts of 15nm silica and 300 parts of toluene to the reactor. After stirring evenly, add 100 parts of a 0.5wt% VTMS toluene solution and 0.2 parts of hydrochloric acid dropwise at a rate of 3 ml / min under 60°C. After the addition is complete, maintain the temperature at 60°C for 1.5 h, then raise the temperature to 80°C and maintain it for 10 h. Wash the product three times with ethanol and water by ultrasonication and centrifugation, and finally dry it under vacuum at 90°C for 24 h to obtain the modified silica product. Grind the obtained product in a mortar and pestle and sieve to ensure that the particle size is <38 μm.

[0042] (2) Mix 0.5 parts of modified silica (particle size <38um), 2 parts of polymerizable monomer P1 and 30 parts of water thoroughly to form mixing solution A, and 0.002 parts of initiator (azobisisobutylamidine hydrochloride) and 5 parts of water to form mixing solution B.

[0043] (3) Mix standard sand, water-reducing agent, reference cement, mixing liquid A, and mixing liquid B in a ratio of 225:0.05:100:32.5:5.002 using automatic mixing. The mixing process is as follows: low speed mixing for 60 seconds - high speed mixing for 30 seconds - stop mixing for 90 seconds, then high speed mixing for 60 seconds, for a total of 4 minutes. Place the resulting cement paste in a 40*40*160mm mold. After hardening, remove the mold and cure until the desired curing age. The resulting sample is marked as test block MS1. This test block is the one with an internal organic-inorganic hybrid network.

[0044] Example 2

[0045] (1) Add 10 parts of 15nm silica and 300 parts of toluene to the reactor. After stirring evenly, add 100 parts of a 1wt% VTES toluene solution and 0.2 parts of hydrochloric acid dropwise at a rate of 3 ml / min under 60°C. After the addition is complete, maintain the temperature at 60°C for 1 h, then raise the temperature to 80°C and maintain it for 8 h. Wash the product three times with ethanol and water by ultrasonication and centrifugation, and finally dry it under vacuum at 90°C for 24 h to obtain the modified silica product. Grind the obtained product in a mortar and pestle and sieve to ensure that the particle size is <38 μm.

[0046] (2) Add 10 parts of 30nm titanium dioxide and 300 parts of ethanol to the reactor, stir well, and then add 100 parts of ethanol solution with a concentration of 1wt% MAPTES. Then raise the temperature to 70 degrees and maintain it for 10 hours. Wash and centrifuge three times with ethanol and water respectively, and finally dry in a vacuum drying oven at 90 degrees for 24 hours to obtain the product modified titanium dioxide. The obtained product is ground in a mortar and sieved to ensure that the particle size is <76μm.

[0047] (3) Mix 0.5 parts of modified silica (particle size <38um), 0.5 parts of modified titanium dioxide, 2 parts of polymerizable monomer P2 and 30 parts of water thoroughly to form mixing solution A, and 0.02 parts of initiator (azodicyanovalerate) and 5 parts of water to form mixing solution B.

[0048] (4) Mix standard sand, water-reducing agent, reference cement, mixing liquid A, and mixing liquid B in a ratio of 225:0.2:100:33:5.02 using automatic mixing. The mixing process is as follows: low speed mixing for 60 seconds - high speed mixing for 30 seconds - stop mixing for 90 seconds, then high speed mixing for 60 seconds, for a total of 4 minutes. Place the resulting cement paste in a 40*40*160mm mold. After hardening, remove the mold and cure until the desired curing age. The resulting sample is marked as MST2 specimen. This specimen is the specimen with an internal organic-inorganic hybrid network.

[0049] Example 3

[0050] (1) Add 10 parts of 30nm titanium dioxide and 300 parts of ethanol to the reactor, stir well, and then add 100 parts of ethanol solution with a concentration of 1wt% MAPTES and 0.2 parts of hydrochloric acid. Then raise the temperature to 70 degrees and maintain it for 12 hours. Wash and centrifuge three times with ethanol and water respectively, and finally dry in a vacuum drying oven at 90 degrees for 24 hours to obtain the product modified titanium dioxide. The obtained product is ground in a mortar and sieved to ensure that the particle size is <76μm.

[0051] (2) Mix 5 parts of modified titanium dioxide (particle size <76um), 5 parts of polymerizable monomer P3 and 35 parts of water thoroughly to form mixing liquid A, and 0.02 parts of initiator (tetra-tert-butyl peroxide) and 5 parts of water to form mixing liquid B.

[0052] (3) Mix standard sand, water-reducing agent, reference cement, mixing liquid A, and mixing liquid B in a ratio of 225:0.3:100:40:5.02 using automatic mixing. The mixing process is as follows: low speed mixing for 60 seconds - high speed mixing for 30 seconds - stop mixing for 90 seconds, then high speed mixing for 60 seconds, for a total of 4 minutes. Place the resulting cement paste in a 40*40*160mm mold. After hardening, remove the mold and cure until the desired curing age. The resulting sample is marked as MT3 specimen. This specimen is the specimen with an internal organic-inorganic hybrid network.

[0053] Example 4

[0054] (1) Add 10 parts of 30nm titanium dioxide and 300 parts of ethanol to the reactor, stir well, and then add 100 parts of 1wt% AAPTES ethanol solution and 0.2 parts of hydrochloric acid. Then raise the temperature to 70 degrees and maintain it for 10 hours. Wash the product with ethanol and water by ultrasonication and centrifugation three times, and finally dry it in a vacuum drying oven at 90 degrees for 24 hours to obtain the modified titanium dioxide product. The obtained product is ground in a mortar and sieved to ensure that the particle size is <76μm.

[0055] (2) Mix 5 parts of modified titanium dioxide (particle size <76um), 5 parts of polymerizable monomer P4 and 35 parts of water thoroughly to form mixing solution A, and 0.02 parts of initiator (benzoyl peroxide) and 5 parts of water to form mixing solution B.

[0056] (3) Mix standard sand, water-reducing agent, reference cement, mixing liquid A, and mixing liquid B in a ratio of 225:0.05:100:45:5.02 using automatic mixing. The mixing process is as follows: low speed mixing for 60 seconds - high speed mixing for 30 seconds - stop mixing for 90 seconds, then high speed mixing for 60 seconds, for a total of 4 minutes. Place the resulting cement paste in a 40*40*160mm mold. After hardening, remove the mold and cure until the desired curing age. The resulting sample is marked as MT4 specimen. This specimen is the specimen with an internal organic-inorganic hybrid network.

[0057] Example 5

[0058] (1) Add 10 parts of 30nm titanium dioxide and 300 parts of ethanol to the reactor, stir well, and then add 100 parts of 1wt% AAMTMS ethanol solution and 0.2 parts of hydrochloric acid. Then raise the temperature to 70 degrees and maintain it for 10 hours. Wash the product with ethanol and water by ultrasonication and centrifugation three times, and finally dry it in a vacuum drying oven at 90 degrees for 24 hours to obtain the modified titanium dioxide product. The obtained product is ground in a mortar and sieved to ensure that the particle size is <76μm.

[0059] (2) Mix 5 parts of modified titanium dioxide (particle size <76um), 5 parts of polymerizable monomer P5 and 35 parts of water thoroughly to form mixing solution A, and mix 0.01 parts of benzoyl peroxide, 0.01 parts of tert-butyl peroxide and 5 parts of water to form mixing solution B.

[0060] (3) Mix standard sand, water-reducing agent, reference cement, mixing liquid A, and mixing liquid B in a ratio of 225:0.05:100:45:5.02 using automatic mixing. The mixing process is as follows: low speed mixing for 60 seconds - high speed mixing for 30 seconds - stop mixing for 90 seconds, then high speed mixing for 60 seconds, for a total of 4 minutes. Place the resulting cement paste in a 40*40*160mm mold. After hardening, remove the mold and mark the sample obtained after curing to the required age as MT5 specimen. This specimen is the specimen with an internal organic-inorganic hybrid network.

[0061] Example 6

[0062] (1) Add 10 parts of 15nm silica and 300 parts of toluene to the reactor. After stirring evenly, add 50 parts of a 1wt% AAMTMMS toluene solution at a rate of 3 ml / min at 60°C. After the addition is complete, add 50 parts of 1wt% VTES and 0.2 parts of hydrochloric acid all at once. After the addition is complete, maintain the temperature at 60°C for 1.5 h, then raise the temperature to 80°C and maintain it for 10 h. Wash the product three times with ethanol and water by ultrasonication and centrifugation. Finally, dry the product in a vacuum drying oven at 90°C for 24 h to obtain the modified silica product. Grind the obtained product in a mortar and pestle and sieve to ensure that the particle size is <38 μm.

[0063] (2) Mix 0.05 parts ferrous sulfate, 1 part modified silica (particle size <38um), 2 parts polymerizable monomer P6 and 30 parts water thoroughly to make mixing solution A, and mix 0.05 parts hydrogen peroxide and 5 parts water thoroughly to make mixing solution B.

[0064] (3) Mix standard sand, water-reducing agent, reference cement, mixing liquid A, and mixing liquid B in a ratio of 225:0.05:100:33:5 using automatic mixing. The mixing process is as follows: low speed mixing for 60 seconds - high speed mixing for 30 seconds - stop mixing for 90 seconds, then high speed mixing for 60 seconds, for a total of 4 minutes. Place the resulting cement paste in a 40*40*160mm mold. After hardening, remove the mold and cure until the desired curing age. The resulting sample is marked as MS6 specimen. This specimen is the specimen with an internal organic-inorganic hybrid network.

[0065] Example 7

[0066] (1) Add 10 parts of 15nm silica and 300 parts of toluene to the reactor. After stirring evenly, add 100 parts of a 1wt% AAPTMMS toluene solution and 0.2 parts of hydrochloric acid dropwise at a rate of 3 ml / min under 60°C. After the addition is complete, maintain the temperature at 60°C for 1.5 h, then raise the temperature to 80°C and maintain it for 10 h. Wash the product three times with ethanol and water by ultrasonication and centrifugation, and finally dry it under vacuum at 90°C for 24 h to obtain the modified silica product. Grind the obtained product in a mortar and pestle and sieve to ensure that the particle size is <38 μm.

[0067] (2) Mix 0.05 parts of oxalic acid, 1 part of modified silica (particle size <38um), 2 parts of polymerizable monomer P7 and 30 parts of water thoroughly to make mixing solution A, and mix 0.05 parts of ammonium persulfate and 5 parts of water thoroughly to make mixing solution B.

[0068] (4) Mix standard sand, water-reducing agent, reference cement, mixing liquid A, and mixing liquid B in a ratio of 225:0.05:100:33:5 using automatic mixing. The mixing process is as follows: low speed mixing for 60 seconds - high speed mixing for 30 seconds - stop mixing for 90 seconds, then high speed mixing for 60 seconds, for a total of 4 minutes. Place the resulting cement paste in a 40*40*160mm mold. After hardening, remove the mold and cure until the desired curing age. The resulting sample is marked as MS7 specimen. This specimen is the specimen with an internal organic-inorganic hybrid network.

[0069] Example 8

[0070] (1) Add 10 parts of 15nm silica and 300 parts of toluene to the reactor. After stirring evenly, add 100 parts of a 1wt% AAPTMMS toluene solution and 0.2 parts of hydrochloric acid dropwise at a rate of 3 ml / min under 60°C. After the addition is complete, maintain the temperature at 60°C for 1.5 h, then raise the temperature to 80°C and maintain it for 10 h. Wash the product three times with ethanol and water by ultrasonication and centrifugation, and finally dry it under vacuum at 90°C for 24 h to obtain the modified silica product. Grind the obtained product in a mortar and pestle and sieve to ensure that the particle size is <38 μm.

[0071] (2) Mix 0.05 parts glucose, 1 part modified silica (particle size <38um), 2 parts polymerizable monomer P8, 2 parts polymerizable monomer P11 and 30 parts water thoroughly to make mixing solution A, and mix 0.05 parts sodium persulfate and 5 parts water thoroughly to make mixing solution B.

[0072] (4) Mix standard sand, water-reducing agent, reference cement, mixing liquid A, and mixing liquid B in a ratio of 225:0.05:100:35:5 using automatic mixing. The mixing process is as follows: low speed mixing for 60 seconds - high speed mixing for 30 seconds - stop mixing for 90 seconds, then high speed mixing for 60 seconds, for a total of 4 minutes. Place the resulting cement paste in a 40*40*160mm mold. After hardening, remove the mold and cure until the desired curing age. The resulting sample is marked as MS8 specimen. This specimen is the specimen with an internal organic-inorganic hybrid network.

[0073] Example 9

[0074] (1) Add 10 parts of 15nm silica and 300 parts of toluene to the reactor. After stirring evenly, add 100 parts of a 1wt% AAPTMMS toluene solution and 0.2 parts of hydrochloric acid dropwise at a rate of 3 ml / min under 60°C. After the addition is complete, maintain the temperature at 60°C for 1.5 h, then raise the temperature to 80°C and maintain it for 10 h. Wash the product three times with ethanol and water by ultrasonication and centrifugation, and finally dry it under vacuum at 90°C for 24 h to obtain the modified silica product. Grind the obtained product in a mortar and pestle and sieve to ensure that the particle size is <38 μm.

[0075] (2) Mix 0.1 parts sodium sulfite, 1 part modified silica (particle size <38um), 2 parts polymerizable monomer P9 and 30 parts water thoroughly to make mixing solution A, and mix 0.01 parts potassium persulfate and 5 parts water thoroughly to make mixing solution B.

[0076] (4) Mix standard sand, water-reducing agent, reference cement, mixing liquid A, and mixing liquid B in a ratio of 225:0.05:100:33:5 using automatic mixing. The mixing process is as follows: low speed mixing for 60 seconds - high speed mixing for 30 seconds - stop mixing for 90 seconds, then high speed mixing for 60 seconds, for a total of 4 minutes. Place the resulting cement paste in a 40*40*160mm mold. After hardening, remove the mold and cure until the desired curing age. The resulting sample is marked as MS9 specimen. This specimen is the specimen with an internal organic-inorganic hybrid network.

[0077] Example 10

[0078] (1) Add 10 parts of 15nm silica and 300 parts of toluene to the reactor. After stirring evenly, add 100 parts of a 2wt% AAPTMMS toluene solution and 0.2 parts of hydrochloric acid dropwise at a rate of 3 ml / min under 60°C. After the addition is complete, maintain the temperature at 60°C for 1.5 h, then raise the temperature to 80°C and maintain it for 10 h. Wash the product three times with ethanol and water by ultrasonication and centrifugation, and finally dry it under vacuum at 90°C for 24 h to obtain the modified silica product. Grind the obtained product in a mortar and pestle and sieve to ensure that the particle size is <38 μm.

[0079] (2) Mix 0.05 parts sodium bisulfite, 1 part modified silica (particle size <38um), 2 parts polymerizable monomer P10 and 30 parts water thoroughly to make mixing solution A, and mix 0.05 parts potassium persulfate and 5 parts water thoroughly to make mixing solution B.

[0080] (4) Mix standard sand, water-reducing agent, reference cement, mixing liquid A, and mixing liquid B in a ratio of 225:0.05:100:33:5 using automatic mixing. The mixing process is as follows: low speed mixing for 60 seconds - high speed mixing for 30 seconds - stop mixing for 90 seconds, then high speed mixing for 60 seconds, for a total of 4 minutes. Place the resulting cement paste in a 40*40*160mm mold. After hardening, remove the mold and cure until the desired curing age. The resulting sample is marked as MS10 specimen. This specimen is the specimen with an internal organic-inorganic hybrid network.

[0081] Example 11

[0082] (1) Add 10 parts of 15nm silica and 300 parts of toluene to the reactor. After stirring evenly, add 100 parts of a 1wt% AAPTMMS toluene solution and 0.2 parts of hydrochloric acid dropwise at a rate of 3 ml / min under 60°C. After the addition is complete, maintain the temperature at 60°C for 1.5 h, then raise the temperature to 80°C and maintain it for 10 h. Wash the product three times with ethanol and water by ultrasonication and centrifugation, and finally dry it under vacuum at 90°C for 24 h to obtain the modified silica product. Grind the obtained product in a mortar and pestle and sieve to ensure that the particle size is <38 μm.

[0083] (2) Mix 0.05 parts sodium metabisulfite, 1 part modified silica (particle size <38um), 3 parts polymerizable monomer P11, 0.02 parts N,N-methylenebisacrylamide and 30 parts water thoroughly to make mixing solution A, and mix 0.05 parts potassium persulfate and 5 parts water thoroughly to make mixing solution B.

[0084] (4) Mix standard sand, water-reducing agent, reference cement, mixing liquid A, and mixing liquid B in a ratio of 225:0.05:100:34:5 using automatic mixing. The mixing process is as follows: low speed mixing for 60 seconds - high speed mixing for 30 seconds - stop mixing for 90 seconds, then high speed mixing for 60 seconds, for a total of 4 minutes. Place the resulting cement paste in a 40*40*160mm mold. After hardening, remove the mold and cure until the desired curing age. The resulting sample is marked as test block MS11. This test block is the one with an internal organic-inorganic hybrid network.

[0085] Example 12

[0086] (1) Add 10 parts of 15nm silica and 300 parts of toluene to the reactor. After stirring evenly, add 100 parts of a 1wt% AAPTMMS toluene solution and 0.2 parts of hydrochloric acid dropwise at a rate of 3 ml / min under 60°C. After the addition is complete, maintain the temperature at 60°C for 1.5 h, then raise the temperature to 80°C and maintain it for 10 h. Wash the product three times with ethanol and water by ultrasonication and centrifugation, and finally dry it under vacuum at 90°C for 24 h to obtain the modified silica product. Grind the obtained product in a mortar and pestle and sieve to ensure that the particle size is <38 μm.

[0087] (2) Mix 0.2 parts of triethanolamine, 1 part of modified silica (particle size <38um), 2 parts of polymerizable monomer P4, 2 parts of polymerizable monomer P11 and 30 parts of water thoroughly to make mixing solution A, and mix 0.1 parts of potassium persulfate and 5 parts of water thoroughly to make mixing solution B.

[0088] (4) Mix standard sand, water-reducing agent, reference cement, mixing liquid A, and mixing liquid B in a ratio of 225:0.05:100:35:5 using automatic mixing. The mixing process is as follows: low speed mixing for 60 seconds - high speed mixing for 30 seconds - stop mixing for 90 seconds, then high speed mixing for 60 seconds, for a total of 4 minutes. Place the resulting cement paste in a 40*40*160mm mold. After hardening, remove the mold and cure until the desired curing age. The resulting sample is marked as test block MS12. This test block is the one with an internal organic-inorganic hybrid network.

[0089] Example 13

[0090] (1) Add 10 parts of 15nm silica and 300 parts of toluene to the reactor. After stirring evenly, add 100 parts of a 1wt% AAPTMMS toluene solution and 0.2 parts of hydrochloric acid dropwise at a rate of 3 ml / min under 60°C. After the addition is complete, maintain the temperature at 60°C for 1.5 h, then raise the temperature to 80°C and maintain it for 10 h. Wash the product three times with ethanol and water by ultrasonication and centrifugation, and finally dry it under vacuum at 90°C for 24 h to obtain the modified silica product. Grind the obtained product in a mortar and pestle and sieve to ensure that the particle size is <38 μm.

[0091] (2) Mix 0.1 parts of triisopropanolamine, 1 part of modified silica (particle size <38um), 5 parts of polymerizable monomer P11 and 30 parts of water thoroughly to make mixing solution A, and mix 0.02 parts of potassium persulfate and 5 parts of water thoroughly to make mixing solution B.

[0092] (4) Mix standard sand, water-reducing agent, reference cement, mixing liquid A, and mixing liquid B in a ratio of 225:0.05:100:36:5 using automatic mixing. The mixing process is as follows: low speed mixing for 60 seconds - high speed mixing for 30 seconds - stop mixing for 90 seconds, then high speed mixing for 60 seconds, for a total of 4 minutes. Place the resulting cement paste in a 40*40*160mm mold. After hardening, remove the mold and cure until the desired curing age. The resulting sample is marked as test block MS13. This test block is the one with an internal organic-inorganic hybrid network.

[0093] Example 14

[0094] (1) Add 10 parts of 15nm silica and 300 parts of toluene to the reactor. After stirring evenly, add 100 parts of a 1wt% AAPTMMS toluene solution and 0.2 parts of hydrochloric acid dropwise at a rate of 3 ml / min under 60°C. After the addition is complete, maintain the temperature at 60°C for 1.5 h, then raise the temperature to 80°C and maintain it for 10 h. Wash the product three times with ethanol and water by ultrasonication and centrifugation, and finally dry it under vacuum at 90°C for 24 h to obtain the modified silica product. Grind the obtained product in a mortar and pestle and sieve to ensure that the particle size is <38 μm.

[0095] (2) Mix 0.01 parts of triisopropanolamine, 1 part of modified silica (particle size <38um), 0.5 parts of polymerizable monomer P11 and 30 parts of water thoroughly to form mixing solution A, and mix 0.002 parts of potassium persulfate and 5 parts of water thoroughly to form mixing solution B.

[0096] (4) Mix standard sand, water-reducing agent, reference cement, mixing liquid A, and mixing liquid B in a ratio of 225:0.05:100:31.5:5 using automatic mixing. The mixing process is as follows: low speed mixing for 60 seconds - high speed mixing for 30 seconds - stop mixing for 90 seconds, then high speed mixing for 60 seconds, for a total of 4 minutes. Place the resulting cement paste in a 40*40*160mm mold. After hardening, remove the mold and cure until the desired curing age. The resulting sample is marked as test block MS13. This test block is the one with an internal organic-inorganic hybrid network.

[0097] Comparative Example 1

[0098] (1) Add 10 parts of 15nm silica and 300 parts of toluene to the reactor. After stirring evenly, add 100 parts of a 0.5wt% VTMS toluene solution and 0.2 parts of hydrochloric acid dropwise at a rate of 3 ml / min under 60°C. After the addition is complete, maintain the temperature at 60°C for 1.5 h, then raise the temperature to 80°C and maintain it for 10 h. Wash the product three times with ethanol and water by ultrasonication and centrifugation, and finally dry it under vacuum at 90°C for 24 h to obtain the modified silica product. Grind the obtained product in a mortar and pestle and sieve to ensure that the particle size is <38 μm.

[0099] (2) Mix 0.5 parts of modified silica, 2 parts of polymerizable monomer P1 and 30 parts of water at 60 degrees, add 5 parts of 0.04% aqueous solution of 2,2'-azobisisobutylamidine dihydrochloride, maintain the reaction at 60 degrees for 7 hours, and use the resulting solution as the mixing liquid.

[0100] (3) Mix standard sand, water-reducing agent, reference cement, and mixing liquid in a ratio of 225:0.2:100:36 using automatic mixing. The mixing process is as follows: low speed mixing for 60 seconds - high speed mixing for 30 seconds - stop mixing for 90 seconds, then high speed mixing for 60 seconds, for a total of 4 minutes. Place the resulting cement paste in a 40*40*160mm mold. After hardening, remove the mold and mark the sample obtained after curing to the required age as specimen block B1.

[0101] Comparative Example 2

[0102] (1) Mix 0.5 parts of silica (particle size <38um), 2 parts of polymerizable monomer P1 and 30 parts of water thoroughly to form mixing solution A, and 0.002 parts of initiator (azobisisobutylamidine hydrochloride) and 5 parts of water to form mixing solution B.

[0103] (2) Mix standard sand, water-reducing agent, reference cement, mixing liquid A, and mixing liquid B in a ratio of 225:0.2:100:32.5:5 using automatic mixing. The mixing process is as follows: low speed mixing for 60 seconds - high speed mixing for 30 seconds - stop mixing for 90 seconds, then high speed mixing for 60 seconds, for a total of 4 minutes. Place the resulting cement paste in a 40*40*160mm mold. After hardening, remove the mold and mark the sample obtained after curing to the required age as specimen block B2.

[0104] Comparative Example 3

[0105] (1) Add 10 parts of 15nm silica and 300 parts of toluene to the reactor. After stirring evenly, add 100 parts of a 0.5wt% VTMS toluene solution and 0.2 parts of hydrochloric acid dropwise at a rate of 3 ml / min under 60°C. After the addition is complete, maintain the temperature at 60°C for 1.5 h, then raise the temperature to 80°C and maintain it for 10 h. Wash the product three times with ethanol and water by ultrasonication and centrifugation, and finally dry it under vacuum at 90°C for 24 h to obtain the modified silica product. Grind the obtained product in a mortar and pestle and sieve to ensure that the particle size is <38 μm.

[0106] (2) Standard sand, water-reducing agent, reference cement, modified silica (particle size <38µm), monomer P1, water, and initiator (azobisisobutylamidine hydrochloride) were mixed in a ratio of 225:0.2:100:0.5:2:35:0.002 using an automatic mixing system. The mixing process was as follows: low speed mixing for 60 seconds - high speed mixing for 30 seconds - stop mixing for 90 seconds, then high speed mixing for 60 seconds, for a total of 4 minutes. The resulting cement paste was placed in a 40*40*160mm mold. After hardening, the mold was removed, and the sample obtained after curing to the designated age was marked as specimen block B3.

[0107] Comparative Example 4

[0108] (1) Mix 2 parts of polymerizable monomer P1 with 30 parts of water thoroughly to form mixing solution A, and 0.002 parts of initiator (azobisisobutylamidine hydrochloride) and 5 parts of water to form mixing solution B.

[0109] (2) Standard sand, water-reducing agent, reference cement, mixing liquid A, and mixing liquid B (azobisisobutylamidine hydrochloride) were mixed in a ratio of 225:0.3:100:32:5 using an automatic mixing system. The mixing process was as follows: low speed mixing for 60 seconds, high speed mixing for 30 seconds, stop mixing for 90 seconds, and then high speed mixing for 60 seconds, for a total of 4 minutes. The resulting cement paste was placed in a 40*40*160mm mold. After hardening, the mold was removed, and the samples obtained after curing to the designated age were marked as specimen blocks B4.

[0110] Test Example 1: Performance Test

[0111] The mortar uses Onoda P·11 52.5 cement with a water-cement ratio of 0.3. The admixture dosage is calculated based on the reduced weight of the cementitious material (unit: mass percentage, %bwoc). The water-reducing agent used is the commercially available polycarboxylate superplasticizer PCA-I from Subote Company. Specific testing methods were performed according to the relevant provisions of GB8077-2012 "Test Method for Homogeneity of Concrete Admixtures". Test results are available in the appendix to the instruction manual. Figure 1 .

[0112] from Figure 1 As can be seen, the flowability of Example 1 is similar to that of the blank sample within 2 hours, and greater than that of the blank sample after 2 hours. The flowability of Comparative Examples 2, 3, and 4 is similar, slightly lower than that of the blank sample. The flowability of Comparative Example 1 is significantly lower than that of the other samples, with a flowability of <200 mm after 1.5 hours. These examples demonstrate that controlling the polymerization reaction to occur after the acceleration period of the hydration reaction, avoiding polymerization beforehand, can lead to the presence of large unhydrated particles in the resulting specimens, which greatly affects the mechanical properties of the cement specimens and results in localized low strength. In other words, constructing an organic-inorganic hybrid network in situ within cement-based materials can significantly improve the workability of cement-based materials.

[0113] Test Example 2: Mechanical Property Test

[0114] For the 40*40*160mm specimens in the examples, the flexural strength was tested using the three-point bending method at a test speed of 50 N / s, and the compressive strength was tested at a test speed of 2.4 kN / s. (The reference sample was prepared by mixing reference cement and mixing liquid in a 20:7 ratio, and the mixing and curing methods were the same as those used for the specimens in the examples). All mortars used were commercially available, conventional polycarboxylate superplasticizers from Jiangsu Subote New Material Co., Ltd. I. The test results of the mechanical properties of the specimen are shown in Table 2 below.

[0115] Table 2

[0116]

[0117]

[0118]

[0119] Table 1 shows the mechanical property test results of the specimens. The mechanical properties of samples MS1, MST2, MT3, MT4, and MT5-MS8 are significantly better than the reference samples. The 28-day flexural strength is significantly improved compared to the reference samples, while the compressive strength remains unchanged. The sample with the highest flexural strength, water-cured MS13, reached 15.76 MPa at 28 days. In contrast, the standard-cured B1 sample with directly added polymer showed a slight improvement in 28-day flexural strength (0.28 MPa) compared to the control sample, but its compressive strength decreased significantly. This is because low-molecular-weight polymers aggregate and coat the surface of unhydrated cement particles, preventing some cement from hydrating and affecting the overall hydration process. Furthermore, the resulting specimens may contain large unhydrated particles. Both of these factors greatly affect the mechanical properties of the cement specimens. High-molecular-weight polymers can cause the cement paste to lose its fluidity, making it impossible to pour into the mold. Additionally, the large volume of the polymer makes it difficult to disperse evenly in the cementitious material, leading to localized areas of lower strength in the specimens. In addition, comparative example B3 was prepared by adding all components together and stirring. During the one-pot polymerization process, the initiator concentration was high in some areas, causing premature polymerization of monomers, which significantly affected the overall performance. It can be seen that the mechanical properties of the sample prepared by the one-pot polymerization method decreased significantly compared to Example 1, with a 28-day decrease in compressive strength of 20.68 MPa and a 28-day decrease in flexural strength of 1.03 MPa. Sample B4 was prepared by in-situ polymerization of organic components in cement. The 28-day mechanical properties show that adding only organic components can improve the flexural strength of cement-based materials (0.79 MPa), but the improvement is weaker than in Example 1, while also having a slight negative impact on compressive strength (1.84 MPa). These examples demonstrate that adding cement reinforcing additives to cement-based materials to construct an in-situ organic-inorganic hybrid network can effectively improve the flexural strength of cement-based materials while maintaining compressive strength.

[0120] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A cement reinforcing additive, characterized in that: The cement reinforcing additive includes organic components and modified inorganic components, wherein the weight fraction ratio of the organic components to the modified inorganic components is (0.5-5):1; The organic component is at least one of the following general formulas (1)-(4): ， Where R1 represents H, CH3, or CH3COOH; R2 represents H or an active metal ion; R3 represents H or CH3; R4 and R5 independently represent H, CH3, CH2CH3, CH2OH, CH2CH2OH, or CH2CHCH3OH, respectively; R6, R7, and R8 independently represent H or CH3, respectively; R9 represents an alkyl group with 4-30 carbon atoms; X1, X2, and X3 independently represent O or NH, respectively; a and b independently refer to the average repeating unit number of the ethoxy-CH2CH2O- chain segment, with values ​​ranging from 4 to 50; The modified inorganic component is obtained by modifying an inorganic component that can participate in the hydration product generation process with a polymerizable siloxane. The inorganic component is selected from at least one of nano-SiO2, nano-CSH, cement, and nano-TiO2; The polymerizable siloxane structure contains at least one vinyl group, and the polymerizable siloxane is selected from at least one of vinyltrimethoxysilane, vinyltriethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropyltriethoxysilane, methacryloxymethyltriethoxysilane, acryloyloxymethyltrimethoxysilane, and acryloyloxypropyltrimethoxysilane. The molar ratio of the polymerizable siloxane to the inorganic component is (0.05-0.3):

1.

2. The cement reinforcing additive according to claim 1, characterized in that, The modified inorganic component is prepared by the following steps: the inorganic component is added to a solvent and stirred evenly, then polymerizable siloxane and hydrochloric acid are added dropwise, and after the reaction is completed, the modified inorganic component with a particle size of <76 μm is obtained by washing, drying and grinding.

3. The cement reinforcing additive according to claim 2, characterized in that: The concentration of the polymerizable siloxane is 0.5-2%; the concentration of the hydrochloric acid is 1 mol / L, and the amount used is 0.5-2% of the mass of the inorganic component.

4. The cement reinforcing additive according to claim 2, characterized in that: The reaction conditions after the addition are 60±0.5℃ for 1-2 hours, then the temperature is raised to 70-80℃ and maintained for 8-12 hours.

5. The application of the cement reinforcing additive according to claim 1, characterized in that: This cement reinforcing additive is used in the preparation of cement-based materials to improve their flexural strength and toughness.

6. A cement-based material, characterized in that, The cement-based material comprises the following components in parts by weight: 1-10 parts cement reinforcing additive, 0.0002-0.1 parts initiator, 225 parts standard sand, 0.05-0.2 parts water-reducing agent, 100 parts cement, and 25-50 parts water; the initiator is a free radical initiator, and the amount of the initiator is 0.1%-2.5% of the organic components in the cement reinforcing additive; the cement reinforcing additive is the cement reinforcing additive as described in claim 1.

7. A cement-based material according to claim 6, characterized in that: The free radical initiator is a medium-temperature thermal initiator or a redox initiation system.

8. A cement-based material according to claim 7, characterized in that, The term "medium temperature" refers to 30℃-100℃.

9. A cement-based material according to claim 6, characterized in that: The thermal initiator is at least one selected from azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, azobisisobutylamidine hydrochloride, ammonium persulfate, azobiscyanopentanoic acid, tetratert-butyl peroxide, benzoyl peroxide, and tert-butyl peroxide; the redox initiation system consists of a persulfate or peroxide as an oxidant and a sulfite or organic amine as a reducing agent; the amount of reducing agent is 50%-200% of the amount of oxidant.

10. The method for preparing a cement-based material according to claim 6, characterized in that: The cement reinforcing additive is mixed with water to obtain mixing liquid A. The initiator is prepared into mixing liquid B with a concentration of 0.02%-0.6%. The cement-based material is obtained by mixing mixing liquid A, mixing liquid B, standard sand, water-reducing agent and cement.

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