Concrete composite additive and preparation method thereof

Abstract

The invention belongs to the technical field of building materials, and discloses a concrete composite additive and a preparation method thereof. The additive comprises a polycarboxylate superplasticizer, nano silicon dioxide, modified starch ether, bentonite, a calcium sulphoaluminate activator, a bio-based antirust agent and a graphene oxide dispersion liquid. Through a step-by-step mixing process, liquid phase dispersion is performed firstly, then solid phase gradient mixing is performed, and ultrasonic treatment and low-temperature drying are combined, so that the problem of multi-component interface compatibility and activity retention is solved. The obtained additive can synergistically improve the anti-cracking and anti-rust performance of concrete, significantly reduce chloride ion penetration and prolong the durability period. And the preparation method is environment-friendly, efficient and suitable for high-durability concrete engineering.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a concrete composite additive and its preparation method. Background Technology

[0002] Concrete additives, as key materials for improving concrete performance, have always been a focus of industry research in terms of functional integration. Traditional additive systems typically address single performance defects, such as water-reducing components and densifying components acting independently, which limits the overall improvement of concrete performance. Especially in engineering environments with high durability requirements, existing additives struggle to simultaneously achieve synergistic optimization of crack resistance, corrosion prevention, and long-term density. Some solutions employing nanomaterial reinforcement suffer from particle agglomeration issues that affect dispersion uniformity, thus exacerbating microscopic defects in concrete.

[0003] From an environmental perspective, conventional rust-inhibiting additives often contain harmful substances such as nitrites, and their uncontrollable ion release can easily lead to alkali-aggregate reaction risks in concrete. While attempts to introduce bio-based materials as alternatives have failed to achieve long-lasting slow-release functions due to the high temperatures or strong shear conditions during processing damaging the active ingredients. Existing preparation processes lack adaptability to the integration of multiphase components, particularly addressing the interfacial compatibility issues between hydrophilic inorganic materials and hydrophobic organic materials, which often rely on excessive surfactants. This, in turn, leads to an abnormally high air content in the concrete.

[0004] There is an urgent need to develop a composite additive with strong component synergy and environmental friendliness, which can systematically improve the durability factor while ensuring the workability of concrete through innovative material combinations and mild preparation processes. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems existing in the prior art and to provide a concrete composite additive and its preparation method.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a concrete composite additive, comprising the following raw materials in parts by weight: 20-40 parts of polycarboxylate superplasticizer, 10-25 parts of nano silica, 5-15 parts of modified starch ether, 8-18 parts of calcium-based bentonite, 3-12 parts of calcium sulfoaluminate activator, 1-5 parts of bio-based slow-release rust inhibitor, and 1-10 parts of graphene oxide dispersion.

[0007] Furthermore, the polycarboxylate superplasticizer has a molecular weight of 20,000 to 50,000 Da, and its side chains contain phosphonic acid groups.

[0008] Furthermore, the nano-silica has a particle size of 10~50nm and a specific surface area ≥200m². 2 / g.

[0009] Furthermore, the modified starch ether is a compound of hydroxypropyl starch ether and anionic starch acetate ether in a mass ratio of 1 to 3:1.

[0010] Furthermore, the bio-based slow-release rust inhibitor is formed by cross-linking phytic acid and chitosan quaternary ammonium salt through amide bonds to form a microcapsule structure, with a microcapsule particle size of 1~10μm.

[0011] Furthermore, the solid content of the graphene oxide dispersion is 1-10%.

[0012] This invention also provides a method for preparing the above-mentioned concrete composite additive, comprising the following steps: S1. Mixing polycarboxylate superplasticizer and graphene oxide dispersion yields mixture A; S2. Premix B is obtained by mixing nano-silica, calcium-based bentonite and calcium sulfoaluminate activator. S3. Add premixed material B to mixture A in three portions, and perform vacuum ultrasonic dispersion after each addition to obtain mixture C; S4. After mixing modified starch ether, bio-based slow-release rust inhibitor and mixture C, the mixture is sequentially subjected to vacuum degassing, spray drying and cooling to obtain concrete composite additive.

[0013] Furthermore, in step S1, the mixing temperature is 40~50℃ and the mixing time is 20~40min; In step S2, the mixing time is 10-20 minutes.

[0014] Furthermore, in step S3, the vacuum degree of vacuum ultrasonic dispersion is ≤-0.08MPa, the ultrasonic power of vacuum ultrasonic dispersion is 500~800W, and the vacuum ultrasonic dispersion time is 5~10min.

[0015] Furthermore, in step S4, the mixing temperature is 30~40℃ and the mixing time is 10~30min.

[0016] As can be seen from the above technical solution, compared with the prior art, the beneficial effects of the present invention are as follows: 1. Polycarboxylate superplasticizer and graphene oxide cleverly construct a three-dimensional dispersion network, which fully ensures the fluidity of concrete mixture, while working synergistically with nano silica and calcium sulfoaluminate activator to promote the development of hydration products towards a denser direction, thereby significantly improving the impermeability and early crack resistance of concrete.

[0017] 2. Bio-based rust inhibitors, through the microcapsule slow-release mechanism, can precisely target and capture corrosive factors, changing the problem of failure release that is prone to occur in traditional rust inhibitors. This truly achieves rust inhibition throughout the entire life cycle of concrete, providing a strong guarantee for the long-term stability of concrete structures.

[0018] 3. The compound system composed of modified starch ether and bentonite effectively stabilizes the solid-liquid multiphase interface through charge balancing, successfully eliminating the weak areas of strength formed by the agglomeration of nanoparticles, making the internal structure of concrete more uniform and dense, and significantly improving the overall performance.

[0019] 4. The stepwise gradient mixing process, combined with low-temperature dynamic drying technology, can effectively maintain the molecular activity of heat-sensitive biological components, avoid the risk of chemical structure damage that may occur in conventional processes, and ensure the activity and performance stability of the active ingredients in the product.

[0020] 5. The alkali-free rust prevention system eliminates the occurrence of alkali-aggregate reaction in concrete from the source. Moreover, no high-temperature toxic byproducts are generated during the preparation process. The entire production process is green and environmentally friendly, meeting the environmentally friendly requirements of modern industry and having good social and environmental benefits. Attached Figure Description

[0021] Figure 1 A photograph of the concrete composite additive prepared according to the present invention. Figure 2 This is a process flow diagram for preparing the concrete composite additive of the present invention. Detailed Implementation

[0022] This invention provides a concrete composite additive, comprising the following raw materials in parts by weight: 20-40 parts of polycarboxylate superplasticizer, 10-25 parts of nano silica, 5-15 parts of modified starch ether, 8-18 parts of calcium-based bentonite, 3-12 parts of calcium sulfoaluminate activator, 1-5 parts of bio-based slow-release rust inhibitor, and 1-10 parts of graphene oxide dispersion.

[0023] In this invention, the amount of the polycarboxylate superplasticizer is preferably 25 to 35 parts, and more preferably 30 parts.

[0024] In this invention, the amount of nano-silica is preferably 15 to 20 parts, more preferably 18 parts; the nano-silica is surface modified by silane coupling agent KH-550.

[0025] In this invention, the amount of modified starch ether is preferably 8 to 12 parts, and more preferably 10 parts.

[0026] In this invention, the amount of calcium-based bentonite used is preferably 10 to 15 parts, and more preferably 12 parts.

[0027] In this invention, the amount of the calcium sulfoaluminate activator is preferably 5 to 10 parts, and more preferably 8 parts.

[0028] In this invention, the amount of the bio-based slow-release rust inhibitor is preferably 2 to 4 parts, and more preferably 3 parts.

[0029] In this invention, the amount of the graphene oxide dispersion is preferably 2 to 8 parts, and more preferably 4 to 6 parts.

[0030] In this invention, the molecular weight of the polycarboxylate superplasticizer is 20,000 to 50,000 Da, preferably 30,000 to 40,000 Da, and more preferably 35,000 Da; the side chain of the polycarboxylate superplasticizer contains phosphonic acid groups.

[0031] In this invention, the particle size of the nano-silica is 10-50 nm, preferably 20-40 nm, and more preferably 30 nm; the specific surface area is ≥200 m². 2 / g.

[0032] In this invention, the modified starch ether is a compound of hydroxypropyl starch ether and anionic starch acetate ether in a mass ratio of 1 to 3:1, preferably 2:1.

[0033] In this invention, the bio-based slow-release rust inhibitor is formed by cross-linking phytic acid and chitosan quaternary ammonium salt through amide bonds to form a microcapsule structure. The microcapsule particle size is 1~10μm, preferably 2~8μm, and more preferably 4~6μm.

[0034] In this invention, the solid content of the graphene oxide dispersion is 1-10%, preferably 2-8%, and more preferably 4-6%.

[0035] This invention also provides a method for preparing the above-mentioned concrete composite additive, comprising the following steps: S1. Mixing polycarboxylate superplasticizer and graphene oxide dispersion yields mixture A; S2. Premix B is obtained by mixing nano-silica, calcium-based bentonite and calcium sulfoaluminate activator. S3. Add premixed material B to mixture A in three portions, and perform vacuum ultrasonic dispersion after each addition to obtain mixture C; S4. After mixing modified starch ether, bio-based slow-release rust inhibitor and mixture C, the mixture is sequentially subjected to vacuum degassing, spray drying and cooling to obtain concrete composite additive.

[0036] In this invention, in step S1, the mixing temperature is 40~50℃, preferably 42~48℃, and more preferably 44~46℃; the mixing time is 20~40min, preferably 25~35min, and more preferably 30min; the mixing is accompanied by stirring, and the stirring speed is 800~1200rpm, preferably 1000rpm.

[0037] In this invention, in step S2, the mixing time is 10-20 min, preferably 12-18 min, and more preferably 14-16 min; the mixing is carried out under an inert atmosphere, preferably argon, and the stirring speed is 2000-3000 rpm, preferably 2500 rpm.

[0038] In this invention, in step S3, the vacuum degree of vacuum ultrasonic dispersion is ≤-0.08MPa, the ultrasonic power of vacuum ultrasonic dispersion is 500~800W, preferably 600~700W, and the vacuum ultrasonic dispersion time is 5~10min, preferably 6~9min. In this invention, in step S4, the mixing temperature is 30~40℃, preferably 32~38℃, and more preferably 34~36℃; the mixing time is 10~30min, preferably 15~25min, and more preferably 20min; the mixing is accompanied by stirring, and the stirring speed is 300~500rpm, preferably 400rpm; the temperature of the product after cooling is ≤25℃.

[0039] In this invention, the concrete composite additive is used at a concentration of 0.8-1.5% of the total mass of the concrete material, preferably 1.0%.

[0040] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0041] Example 1: The raw materials and quantities used in this example are as follows: 30 parts of polycarboxylate superplasticizer (molecular weight 35000 Da, containing phosphonic acid groups), and nano-silica (KH-550 modified, particle size 30 nm, specific surface area ≥200 m²). 2 18 parts of modified starch ether (hydroxypropyl starch ether: anionic starch acetate ether = 2:1) 10 parts, calcium-based bentonite 12 parts, calcium sulfoaluminate activator 8 parts, bio-based slow-release rust inhibitor (phytic acid-chitosan quaternary ammonium salt microcapsules) 3 parts, and graphene oxide dispersion (solid content 5%) 5 parts.

[0042] The preparation method is as follows: Polycarboxylate superplasticizer and graphene oxide dispersion were added to a reaction vessel and stirred at 1000 rpm for 30 min at 45°C to obtain mixture A. Nano-silica, calcium-based bentonite, and calcium sulfoaluminate activator were added to a high-speed mixer and dry-mixed at 2500 rpm for 15 min under argon protection to obtain premix B. Premix B was divided into three equal parts and added to mixture A in sequence. After each addition, the mixture was treated for 8 minutes under vacuum of -0.09MPa and ultrasonic power of 650W to obtain mixture C. Modified starch ether and bio-based slow-release rust inhibitor were added to mixture C, and the mixture was stirred at 400 rpm for 20 min at 35°C. After vacuum degassing, it was spray-dried and cooled to below 25°C to obtain powdered concrete composite additive.

[0043] Example 2: The raw materials and quantities used in this example are as follows: 40 parts of polycarboxylate superplasticizer (molecular weight 40000 Da, containing phosphonic acid groups), and nano-silica (KH-550 modified, particle size 30 nm, specific surface area ≥200 m²). 2 15 parts of ( / g), 8 parts of modified starch ether (hydroxypropyl starch ether: anionic starch acetate ether = 2:1), 10 parts of calcium-based bentonite, 5 parts of calcium sulfoaluminate activator, 2 parts of bio-based slow-release rust inhibitor (phytic acid-chitosan quaternary ammonium salt microcapsules), and 2 parts of graphene oxide dispersion (5% solid content).

[0044] The preparation method is as follows: Polycarboxylate superplasticizer and graphene oxide dispersion were added to a reaction vessel and stirred at 1200 rpm for 25 min at 48°C to obtain mixture A. Nano-silica, calcium-based bentonite, and calcium sulfoaluminate activator were added to a high-speed mixer and dry-mixed at 2500 rpm for 15 min under argon protection to obtain premix B. Premix B was divided into three equal parts and added to mixture A in sequence. After each addition, the mixture was treated under vacuum of -0.09MPa and ultrasonic power of 700W for 6 minutes to obtain mixture C. Modified starch ether and bio-based slow-release rust inhibitor were added to mixture C, and the mixture was stirred at 400 rpm for 20 min at 35°C. After vacuum degassing, it was spray-dried and cooled to below 25°C to obtain powdered concrete composite additive.

[0045] Example 3: The raw materials and quantities used in this example are as follows: 25 parts of polycarboxylate superplasticizer (molecular weight 30000 Da, containing phosphonic acid groups), and nano-silica (KH-550 modified, particle size 30 nm, specific surface area ≥200 m²). 220 parts of modified starch ether (hydroxypropyl starch ether: anionic starch acetate ether = 3:1) 12 parts of calcium-based bentonite 15 parts of calcium sulfoaluminate activator 10 parts of bio-based slow-release rust inhibitor (phytic acid-chitosan quaternary ammonium salt microcapsules) 4 parts of graphene oxide dispersion (solid content 4%) 8 parts of phytic acid-chitosan quaternary ammonium salt microcapsules 20 parts of modified starch ether (hydroxypropyl starch ether: anionic starch acetate ether = 3:1) 12 ...5 parts of calcium-based bentonite ether 1

[0046] The preparation method is as follows: Polycarboxylate superplasticizer and graphene oxide dispersion were added to a reaction vessel and stirred at 1000 rpm for 30 min at 45°C to obtain mixture A. Nano-silica, calcium-based bentonite, and calcium sulfoaluminate activator were added to a high-speed mixer and dry-mixed at 2800 rpm for 18 minutes under argon protection to obtain premix B. Premix B was divided into three equal parts and added to mixture A in sequence. After each addition, the mixture was treated for 8 minutes under vacuum of -0.09MPa and ultrasonic power of 650W to obtain mixture C. Modified starch ether and bio-based slow-release rust inhibitor were added to mixture C, and the mixture was stirred at 400 rpm for 15 min at 38°C. After vacuum degassing, it was spray-dried and cooled to below 20°C to obtain powdered concrete composite additive.

[0047] Example 4: The raw materials and dosages used in this example are as follows: 28 parts of polycarboxylate superplasticizer (molecular weight 35000 Da, containing phosphonic acid groups), and nano-silica (KH-550 modified, particle size 30 nm, specific surface area ≥200 m²). 2 16 parts of modified starch ether (hydroxypropyl starch ether: anionic starch acetate ether = 2:1) 9 parts, calcium-based bentonite 11 parts, calcium sulfoaluminate activator 6 parts, bio-based slow-release rust inhibitor (phytic acid-chitosan quaternary ammonium salt microcapsules) 2.5 parts, and graphene oxide dispersion (solid content 6%) 3 parts.

[0048] The preparation method is as follows: Polycarboxylate superplasticizer and graphene oxide dispersion were added to a reaction vessel and stirred at 1000 rpm for 30 min at 45°C to obtain mixture A. Nano-silica, calcium-based bentonite, and calcium sulfoaluminate activator were added to a high-speed mixer and dry-mixed at 2500 rpm for 15 min under argon protection to obtain premix B. Premix B was divided into three equal parts and added to mixture A in sequence. After each addition, the mixture was treated for 8 minutes under vacuum of -0.09MPa and ultrasonic power of 650W to obtain mixture C. Modified starch ether and bio-based slow-release rust inhibitor were added to mixture C, and the mixture was stirred at 400 rpm for 20 min at 35°C. After vacuum degassing, it was spray-dried and cooled to below 25°C to obtain powdered concrete composite additive.

[0049] Example 5: The raw materials and dosages used in this example are as follows: 35 parts of polycarboxylate superplasticizer (molecular weight 50000 Da, containing phosphonic acid groups), and nano-silica (KH-550 modified, particle size 30 nm, specific surface area ≥200 m²). 2 22 parts of modified starch ether (hydroxypropyl starch ether: anionic starch acetate ether = 2.5:1) 14 parts of calcium-based bentonite 17 parts of calcium sulfoaluminate activator 11 parts of bio-based slow-release rust inhibitor (phytic acid-chitosan quaternary ammonium salt microcapsules) 4.5 parts of graphene oxide dispersion (solid content 3%) 9 parts of phytic acid-chitosan quaternary ammonium salt microcapsules 2.5 ...

[0050] The preparation method is as follows: Polycarboxylate superplasticizer and graphene oxide dispersion were added to a reaction vessel and stirred at 1000 rpm for 35 min at 42°C to obtain mixture A. Nano-silica, calcium-based bentonite, and calcium sulfoaluminate activator were added to a high-speed mixer and dry-mixed at 2500 rpm for 15 min under argon protection to obtain premix B. Premix B was divided into three equal parts and added to mixture A in sequence. After each addition, the mixture was treated for 10 minutes under vacuum of -0.09MPa and ultrasonic power of 800W to obtain mixture C. Modified starch ether and bio-based slow-release rust inhibitor were added to mixture C, and the mixture was stirred at 500 rpm for 20 min at 35°C. After vacuum degassing, it was spray-dried and cooled to below 25°C to obtain powdered concrete composite additive.

[0051] Comparative Example 1 was the same as Example 1, but without the addition of bio-based rust inhibitors and modified starch ethers.

[0052] Comparative Example 2: Ordinary corn starch ether (unmodified) was used instead of modified starch ether, and the rest was the same as in Example 1.

[0053] Comparative Example 3: Atmospheric pressure mechanical stirring (1000 rpm, 10 min) replaced vacuum ultrasonic dispersion, and the vacuum degassing step was omitted. The rest was the same as in Example 1.

[0054] Performance testing Concrete mix proportions: Cement 420 kg / m³ 3 Sand 680 kg / m 3 1050 kg / m³ of crushed stone 3The water-to-binder ratio is 0.45, and the amount of composite additives is 1.0% (accounting for the total amount of adhesive material).

[0055] Mix according to GB / T 50080-2016 "Test Methods for Performance of Ordinary Concrete Mixtures"; pour 150mm cube specimens (strength), Φ175×185mm cylinders (permeability), and 100×100×400mm prisms (crack resistance), and cure under standard conditions (20±2℃, RH≥95%) to the specified age to obtain specimens. The test items and methods for the specimens are shown in Table 1.

[0056] Table 1 Test Items and Methods for Specimens

[0057] Table 2. Performance test results of workability and mechanical properties

[0058] As shown in Table 2, Examples 1-5 all exhibited excellent slump retention (slump loss rate <7% in 1 hour) and strength increase. Comparative Example 1 (lacking starch ether / rust inhibitor) experienced a sharp drop in fluidity due to solid-liquid interface instability; Comparative Example 3 (simplified process) showed weakened strength gain due to nanoparticle agglomeration.

[0059] Table 3 Durability test results

[0060] As shown in Table 3, the penetration height of Example 1 was reduced by 64% and the crack resistance index was reduced by 75% compared with Comparative Example 1, thus verifying the synergistic densification effect of nano-SiO2 + graphene oxide + calcium sulfoaluminate; the steel potential of Example 1 was always higher than -200mV (passivated state), while Comparative Example 1 was corroded after 90 days, proving the long-term effect of the microcapsule sustained-release mechanism.

[0061] Table 4 Environmental protection test results

[0062] As shown in Table 4, the technical solution provided by this invention has no alkali and no high-temperature byproducts throughout the entire process.

[0063] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A concrete composite additive, characterized by, The raw materials include the following parts by weight: 20~40 parts of polycarboxylic acid water reducer, 10~25 parts of nano-silica, 5~15 parts of modified starch ether, 8~18 parts of calcium-based bentonite, 3~12 parts of calcium sulfoaluminate activator, 1~5 parts of bio-based slow-release antirust agent, and 1~10 parts of graphene oxide dispersion liquid.

2. The concrete composite additive according to claim 1, characterized in that, The molecular weight of the polycarboxylic acid water reducer is 20000~50000 Da, and the side chain of the polycarboxylic acid water reducer contains phosphonic acid groups.

3. The concrete composite additive according to claim 2, characterized in that, The nano-silica has a particle size of 10-50 nm, a specific surface area of ≥200 m 2 / g.

4. The concrete composite additive according to claim 3, characterized in that, The modified starch ether is a compound of hydroxypropyl starch ether and anionic acetic acid starch ether in a mass ratio of 1~3:

1.

5. The concrete composite additive according to any one of claims 1 to 4, characterized in that, The bio-based slow-release antirust agent is formed by cross-linking phytic acid and chitosan quaternary ammonium salt through amide bond to form a microcapsule structure, and the particle size of the microcapsule is 1~10 μm.

6. The concrete composite additive according to claim 5, characterized in that, The solid content of the graphene oxide dispersion liquid is 1~10%.

7. The method of producing a concrete composite additive according to any one of claims 1 to 6, characterized in that, The method includes the following steps: S1, mixing the polycarboxylic acid water reducer and the graphene oxide dispersion liquid to obtain a mixed liquid A; S2, mixing the nano-silica, the calcium-based bentonite and the calcium sulfoaluminate activator to obtain a premix B; S3, adding the premix B to the mixed liquid A in three times, and performing vacuum ultrasonic dispersion after each addition to obtain a mixture C; S4, mixing the modified starch ether, the bio-based slow-release antirust agent and the mixture C, and then sequentially performing vacuum degassing, spray drying and cooling to obtain a concrete composite additive.

8. The method for preparing the concrete composite additive according to claim 7, characterized in that, In the step S1, the mixing temperature is 40~50℃, and the mixing time is 20~40 min; In the step S2, the mixing time is 10~20 min.

9. The method for preparing the concrete composite additive according to claim 8, characterized in that, In the step S3, the vacuum degree of the vacuum ultrasonic dispersion is ≤-0.08 MPa, the ultrasonic power is 500~800 W, and the vacuum ultrasonic dispersion time is 5~10 min.

10. The method of claim 8 or 9, wherein the method further comprises the step of adding a superplasticizer to the mixture of the cementitious material, the water, and the dispersant. 10 In the step S4, the mixing temperature is 30~40℃, and the mixing time is 10~30 min.

Images