A concrete functional admixture, its preparation method and application

Abstract

This invention discloses a functional admixture for improving concrete performance, its preparation method, and its application. The functional admixture is made from the following raw materials in parts by weight: 80-120 parts silicate solution, 5-15 parts fumed nano-silica, 0.5-1.5 parts fatty acid salt surfactant, 0.05-0.16 parts hydrated calcium silicate guiding liquid, 0.2-0.6 parts fluorosilicate, 0.1-0.4 parts air-entraining agent, 0.1-0.3 parts defoamer, 0.5-1.0 parts early-strength agent, and 0.1-0.9 parts retarder. This invention also provides a concrete with high density and self-healing crack function, including this functional admixture.

Description

Technical Field

[0001] This invention belongs to the field of concrete and building materials technology, specifically relating to a functional admixture for improving concrete performance, its preparation method, and its application. Background Technology

[0002] Concrete is made by mixing coarse and fine aggregates, cement, water-reducing agents, and water in a specific ratio. During concrete preparation, the interface between the cement paste and aggregates becomes one of the factors inducing internal shrinkage cracking in the later stages of concrete. During curing, internal moisture continuously migrates to the surface, while externally supplied moisture cannot reach the interior of the concrete in time to support the continuous hydration of the cement. Incomplete cement hydration can also cause micro-cracks within the concrete. Because monitoring changes in the internal structure of concrete is difficult and the methods for treating micro-cracks are limited, these micro-cracks eventually connect, forming obvious tensile cracks.

[0003] For existing through-tensile cracks, higher-strength cementitious materials (repair materials) are often used for surface repair. However, if the interface between the old and new cementitious materials is not properly treated, the repair material will detach within a short period of time, losing its repair and protective functions. Moreover, surface repair cannot eliminate micro-cracks inside the concrete, nor can it prevent micro-cracks from forming tensile cracks.

[0004] There are existing reports of concrete crack repair capsules being added during concrete mixing. For example, Chinese invention patent application CN114482611A (publication date May 13, 2022), entitled "A Method for Self-Healing Concrete," discloses a method of adding concrete repair capsules to concrete. After concrete cracks appear, the repair fluid within the capsules flows out, repairing internal defects in the cracks. Chinese utility model patent CN213680420U (authorization announcement date July 13, 2021), entitled "A Concrete Crack Repair Capsule," discloses a concrete crack repair capsule comprising a capsule shell and a sealing body, with the sealing body stored in a cavity within the capsule shell. These repair capsules rely on the cracking of the concrete to break the capsule, causing the repair material to flow out. However, if the crack is a micro-crack, insufficient to rupture the capsule, the repair material will not be effective.

[0005] Therefore, it is necessary to develop a functional admixture that improves the performance of concrete. When added during concrete mixing, it can fill microcracks and achieve self-healing, improve the water permeability resistance of concrete, and extend the service life of concrete. Summary of the Invention

[0006] To address the aforementioned technical problems in existing technologies, this invention provides a functional admixture for improving concrete performance. This admixture improves the internal pore structure of the hydration products of concrete cementitious materials, densifying the internal pore structure, reducing internal porosity and average pore size, and enhancing the compactness of the concrete structure. Furthermore, when microcracks appear in the concrete structure, the functional admixture within the concrete is activated by external water, continuing to react with incompletely hydrated cementitious materials to produce hydration products, thereby achieving the filling and self-healing of microcracks. The functional admixture of this invention does not affect the setting time and strength properties of concrete, exhibits a significant repair effect, and effectively solves the problem of uncontrollable repair effects in existing concrete repair capsules.

[0007] Therefore, the present invention adopts the following technical solution:

[0008] A functional admixture for improving concrete performance is made from the following raw materials in parts by weight:

[0009] 80-120 parts silicate solution, 5-15 parts fumed nano silica, 0.5-1.5 parts fatty acid salt surfactant, 0.05-0.16 parts hydrated calcium silicate guiding solution, 0.2-0.6 parts fluorosilicate, 0.1-0.4 parts air-entraining agent, 0.1-0.3 parts defoamer, 0.5-1.0 parts early-strength agent, and 0.1-0.9 parts retarder;

[0010] The hydrated calcium silicate guiding solution is prepared through the following steps:

[0011] S1. Weigh 100 parts by weight of deionized water, and then uniformly disperse 0.5-2.0 parts by weight of CarbopolUltrez 21 in the deionized water while stirring. Continue stirring for at least 2 hours to obtain a gel solution.

[0012] S2. Weigh 15-20 parts by weight of calcium silicate hydrate crystals, 1.0-3.0 parts by weight of citric acid and 0.2-0.8 parts by weight of sodium tripolyphosphate, and add them sequentially to the gel solution prepared in step S1 while stirring, and continue stirring for no less than 30 minutes.

[0013] S3. Weigh 0.2-0.5 parts by mass of triethanolamine and add it to the mixed solution prepared in step S2 while stirring. Continue stirring for no less than 15 minutes until a uniform gel emulsion is formed, thus obtaining the hydrated calcium silicate guiding solution.

[0014] Preferably, the functional admixture for improving concrete performance is made from the following raw materials in parts by weight:

[0015] 90-110 parts silicate solution, 8-13 parts fumed nano silica, 0.7-1.3 parts fatty acid salt surfactant, 0.08-0.14 parts hydrated calcium silicate guiding solution, 0.3-0.5 parts fluorosilicate, 0.15-0.3 parts air-entraining agent, 0.1-0.2 parts defoamer, 0.6-0.9 parts early-strength agent, and 0.2-0.7 parts retarder.

[0016] Preferably, the silicate is selected from one or two of sodium silicate and potassium silicate in any proportion.

[0017] More preferably, the silicate aqueous solution has a mass percentage concentration of 20-40%. The silicate aqueous solution can react with Ca in concrete cementitious materials. 2+ A chemical reaction occurs, producing hydrated calcium silicate, which fills microcracks and micropores, increasing density and repairing the structure. Furthermore, silicates can react with Ca(OH)₂, a hydration product in concrete, to form CSH(xCaO·SiO₂·yH₂O) gel, improving the waterproofing ability of concrete.

[0018] Preferably, the loose packing density of the fumed silica nanoparticles is 0.15-0.2 g / cm³. 3 Fineness 200-500 mesh.

[0019] Fumed nano-silica possesses optical properties that resist ultraviolet radiation and can improve the aging resistance, strength, and chemical resistance of other materials. Fumed nano-silica can also partially participate in the hydration reaction of cementitious materials, filling pores and further enhancing the impermeability of these materials.

[0020] Preferably, the fatty acid salt surfactant is selected from one or two of sodium stearate and potassium stearate in any proportion.

[0021] The fatty acid salt surfactants, as waterproofing agents, primarily function to reduce the surface tension of concrete mixtures and decrease or eliminate micro-cracks and capillaries on the surface of concrete structures.

[0022] The hydrated calcium silicate guiding liquid is a calcium silicate hydrated mineral composite system, rich in hybrid particles of inorganic microcrystals and organic polymers with nanoscale microstructures. As a highly efficient additive, the hydrated calcium silicate guiding liquid of this invention can induce cement hydration to form CSH gel, reduce the activation energy of the cement hydration reaction, increase the hydration reaction rate, and promote rapid strength development during the hardening period.

[0023] Preferably, the fluorosilicate is selected from at least one of magnesium fluorosilicate, zinc fluorosilicate, and potassium fluorosilicate. Fluorosilicate can reduce the initial hydration rate of cementitious materials to a certain extent, and when microcracks appear or moisture enters the interior of the structure during later curing or service, it can further promote the continuous participation of the functional additives involved in the present invention in the hydration reaction, thereby achieving the purpose of filling cracks and pores.

[0024] Preferably, the defoamer is selected from polyether or silicone defoamers.

[0025] Preferably, the air-entraining agent is selected from methylcellulose ether or rosin soap.

[0026] Preferably, the early strength agent is selected from at least one of calcium formate, sodium formate, sodium acetate, and calcium acetate.

[0027] Among them, the early strength agent contains carboxylate ions (HCOO). - The diffusion rate is rapid, which not only promotes the formation of CSH gel, but also better promotes the penetration of the functional admixture of the present invention into the concrete structure system, thereby helping the functional admixture of the present invention to further improve the compactness and later crack resistance of the concrete.

[0028] Preferably, the retarder is selected from at least one of tartaric acid, borax, boric acid and aminated lignin.

[0029] Preferably, the functional admixture for improving concrete performance according to the present invention may further include 100-130 parts by weight of water as raw material.

[0030] Preferably, the water is deionized water with a resistivity greater than or equal to 10 megohms per centimeter.

[0031] Therefore, the present invention provides two physical states of functional admixtures for improving concrete performance: one is solid, in which the raw material does not include water; the other is liquid, in which the raw material includes the stated mass fraction of water.

[0032] The present invention also provides a method for preparing the solid functional admixture, comprising the following steps:

[0033] I. Prepare each raw material according to the above-mentioned weight proportions;

[0034] II. Add 100-130 parts by weight of water to the mixer, and then add fumed nano silica, fatty acid salt surfactant, hydrated calcium silicate guiding solution, fluorosilicate, air-entraining agent, retarder, defoamer and early strength agent in sequence at a stirring speed of 30 r / min-60 r / min. Continue stirring for 30 s-80 s, and finally add silicate solution. Stir at a speed of 45 r / min-100 r / min for 60 s-300 s until the solution is fully mixed and homogeneous.

[0035] III. Filter the mixture obtained in step II through a 100-mesh sieve, dry the filtrate under vacuum, and grind it until it all passes through a 200-mesh sieve to obtain the final product.

[0036] Preferably, in step III, the vacuum drying conditions are: vacuum drying at a negative pressure of 0.1 MPa and a temperature of 95-105°C for 5-10 hours.

[0037] The present invention also provides a method for preparing the liquid functional admixture, comprising the following steps:

[0038] I. Prepare all raw materials, including water, according to the above-mentioned weight proportions;

[0039] II. Add the stated mass fraction of water to the mixer, and then add the fumed nano silica, fatty acid salt surfactant, hydrated calcium silicate guiding solution, fluorosilicate, air-entraining agent, retarder, defoamer and early strength agent in sequence at a stirring speed of 30 r / min-60 r / min. Continue stirring for 30 s-80 s, and finally add the silicate solution. Stir at a speed of 45 r / min-100 r / min for 60 s-300 s until the solution is fully mixed and homogeneous.

[0040] III. Filter the mixture obtained in step II through a 100-mesh sieve. The filtrate is the liquid functional additive.

[0041] The present invention also provides the application of the functional admixtures (including the solid functional admixtures and the liquid functional admixtures) in improving the performance of concrete.

[0042] Preferably, the amount of the solid functional admixture is 0.5% to 2.5% of the cement mass.

[0043] Preferably, the amount of the liquid functional admixture is 1% to 5% of the total mass of the concrete cementitious materials.

[0044] Specifically, improving concrete performance refers to increasing concrete compressive strength, self-healing ability, and freeze-thaw resistance, while reducing concrete water absorption, electrical flux, and chloride ion permeability coefficient.

[0045] Specifically, the application refers to adding the functional admixture described in this invention during the concrete mixing process and mixing it evenly.

[0046] Therefore, the present invention also provides a concrete with high density and self-healing crack function, including the above-mentioned functional admixture.

[0047] Another objective of this invention is to provide a method for preparing concrete with high density and self-healing crack function, comprising the following steps:

[0048] Place the concrete mix and the solid functional admixture described in this invention at 5-40°C for at least 24 hours; clean the inside of the mixer to ensure that the surface is free of dirt, oil stains and / or grease; add all raw material components of the concrete except water and the solid functional admixture described in this invention to the mixer, premix for 30s-90s, then add mixing water and mix for 60s-250s until all raw materials are evenly mixed to obtain the final product.

[0049] or

[0050] Place the concrete mix and the liquid functional admixture described in this invention at 5-40°C for at least 24 hours; clean the inside of the mixer to ensure that the surface is free of dirt, oil stains and / or grease; add all raw material components of the concrete except water to the mixer, premix for 30s-90s, then add the liquid functional admixture described in this invention and mixing water, and stir for 60s-250s until all raw materials are evenly mixed to obtain the final product.

[0051] Those skilled in the art will know that the raw materials of the concrete include aggregates, cementitious materials, and mixing water; wherein, the raw materials other than water are called mixing materials; the aggregates include coarse aggregates and fine aggregates, and the cementitious materials include cement and mineral admixtures such as fly ash, silica fume, and ground granulated slag.

[0052] The functional admixtures of this invention are mainly applicable to concrete using cementitious materials such as silicate cement, ordinary silicate cement, and composite silicate cement.

[0053] The functional admixture for improving concrete performance provided by this invention uses sodium silicate and / or potassium silicate as the main components, and also adds an early-strength agent (such as sodium formate). Because carboxylate ions can form similar compounds to AHt and AFm (CA·3Ca(HCOO)2·30H2O, CA·Ca(HCOO)2·10H2O, etc.), the setting time is shortened. Furthermore, carboxylate ions diffuse rapidly and penetrate deeply, thus reaching deep into the concrete interior. Carboxylate ions can also chemically bind silicon atoms to further react with OH groups. - The reaction crosslinks adjacent silicate groups, promoting the formation of CSH gel, increasing the hardening strength of concrete, and accelerating the reaction rate and strength growth of the material.

[0054] The nano-silica introduced by the functional admixture of this invention, in addition to playing the role of filling micro-aggregates, can also participate in the hydration reaction of cementitious materials to generate more hydrated calcium silicate products, reduce the overall porosity, and improve the durability of concrete and mortar structures.

[0055] The retarder in the functional admixture of this invention plays a certain role in regulating the concentration of Ca(OH)2 in the concrete paste. Because the incorporation of the retarder prolongs the hydration reaction time, C3S hydration is more complete, achieving good repair and reinforcement effects as well as improved water permeability resistance.

[0056] The fluorosilicate in the functional admixture of this invention can react with Ca(OH)2, a cement hydration product in concrete, to generate insoluble crystals that block and repair cracks and pores, thereby improving the density, strength, and durability of concrete.

[0057] The waterproofing agent in the functional admixture of this invention can improve the water-repellent effect of concrete surfaces.

[0058] The preparation method of the functional admixture of the present invention is simple and convenient to use. It can be effectively applied to concrete preparation and subsequent maintenance, effectively reducing micro-cracks (at the micron level) inside the concrete structure and surface cracks; thus, it can improve the water penetration resistance of concrete to a certain extent, and the concrete has good durability and long service life.

[0059] In this specification, the mass fractions of each component are not actual mass numbers, but rather represent the proportions of each component. Depending on the actual situation, 1 mass fraction can be any mass unit, such as 1 kg, 2 kg, 10 kg, 100 kg, 1 ton, 1 g, 2 g, 10 g, 20 g, 50 g, 250 g, 500 g, etc. Attached Figure Description

[0060] The present invention will be further described below with reference to the accompanying drawings.

[0061] Figure 1 The photograph shows scanning electron microscope (SEM) images (magnification 5000x) of the concrete mix prepared in Example 8 after sieving out stones, taken at 3d, 7d, and 28d.

[0062] Figure 2 The photograph shows scanning electron microscope (SEM) images (magnification 5000x) of the concrete mix prepared from Comparative Example 6 after sieving out the stones, taken at three ages: 3d, 7d, and 28d.

[0063] Figure 1 and Figure 2 In the diagram, a: 3 days old; b: 7 days old; c: 28 days old. Detailed Implementation

[0064] The present invention will be described below with reference to specific embodiments. Those skilled in the art will understand that these embodiments are for illustrative purposes only and do not limit the scope of the invention in any way.

[0065] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the raw materials used in the following examples are commercially available building materials or industrial additives. The purchase details of some of the raw materials are as follows.

[0066] Sodium silicate, potassium silicate: Tianjin Zhiyuan Chemical Reagent Co., Ltd.

[0067] Fumed nano silica: Beijing Deco Island Gold Technology Co., Ltd.

[0068] Calcium formate, sodium formate: Shanghai Aladdin Technology Co., Ltd.

[0069] Magnesium fluorosilicate, zinc fluorosilicate: Foshan Nanhai Shuangfu Chemical Co., Ltd.

[0070] Tartaric acid: Suzhou Dingya Chemical Co., Ltd.

[0071] Sodium stearate: Tianjin Jinhui Taiya Chemical Reagent Co., Ltd.

[0072] Calcium silicate hydrate: Nanjing Xinyi Synthetic Technology Co., Ltd.

[0073] Penetrating Crystallizing Waterproofing Agent: Beijing Dechang Weiye Architectural Engineering Technology Co., Ltd.

[0074] 1#-3# hydrated calcium silicate guiding solutions were prepared using the following steps and processes for the following examples and comparative examples:

[0075] S1. Weigh 100 parts by weight of deionized water, and then uniformly disperse 0.5-2.0 parts by weight of CarbopolUltrez 21 in the deionized water while stirring. Continue stirring for at least 2 hours to obtain a gel solution.

[0076] S2. Weigh 15-20 parts by weight of calcium silicate hydrate crystals, 1.0-3.0 parts by weight of citric acid and 0.2-0.8 parts by weight of sodium tripolyphosphate, and add them sequentially to the gel solution prepared in step S1 while stirring, and continue stirring for no less than 30 minutes.

[0077] S3. Weigh 0.2-0.5 parts by mass of triethanolamine and add it to the mixed solution prepared in step S2 while stirring. Continue stirring for no less than 15 minutes until a uniform gel emulsion is formed, thus obtaining the hydrated calcium silicate guiding solution.

[0078] The raw material composition of the No. 1 hydrated calcium silicate guiding solution is as follows: 100 parts deionized water, 1.4 parts Carbopol Ultrez 21, 18 parts hydrated calcium silicate crystals, 1.4 parts citric acid, 0.5 parts sodium tripolyphosphate, and 0.4 parts triethanolamine.

[0079] Composition of raw materials for 2# hydrated calcium silicate guiding liquid: 100 parts deionized water, 11.2 parts Carbopol Ultrez 21, 16 parts hydrated calcium silicate crystals, 1.2 parts citric acid, 0.6 parts sodium tripolyphosphate, and 0.4 parts triethanolamine;

[0080] Composition of raw materials for 3# hydrated calcium silicate guiding solution: 100 parts deionized water, 1.7 parts Carbopol Ultrez 21, 20 parts hydrated calcium silicate crystals, 1.9 parts citric acid, 0.6 parts sodium tripolyphosphate, and 0.4 parts triethanolamine.

[0081] Examples 1-6: Functional admixtures for improving concrete performance

[0082] The raw material composition of the functional additives in Examples 1-6 is shown in Table 1.

[0083] The functional additives in Examples 1-3 and 5-6 are in liquid form. Examples 1-3 use No. 1 hydrated calcium silicate guiding solution, and Examples 5-6 use No. 2 hydrated calcium silicate guiding solution. They are prepared using the following method:

[0084] I. Prepare each raw material according to the mass parts shown in Table 1, where 1 mass part = 1 kg;

[0085] II. Add water to the mixer, and then add fumed nano silica, fatty acid salt surfactant, hydrated calcium silicate guiding solution, fluorosilicate, air-entraining agent, retarder, defoamer and early strength agent in sequence at a stirring speed of 30 r / min-60 r / min. Continue stirring for 30 s-80 s, and finally add silicate solution. Stir at a speed of 45 r / min-100 r / min for 60 s-300 s until the solution is fully mixed and homogeneous.

[0086] III. Filter the solution obtained in step II through a 100-mesh sieve. The filtrate is the liquid functional additive.

[0087] The functional additive in Example 4 is a solid, prepared using No. 3 hydrated calcium silicate guiding solution, and is carried out by the following method:

[0088] I. Prepare each raw material according to the mass parts shown in Table 1, where 1 mass part = 1 kg;

[0089] II. Add 115 parts by weight of water to the mixer, and then add fumed nano silica, fatty acid salt surfactant, hydrated calcium silicate guiding solution, fluorosilicate, air-entraining agent, retarder, defoamer and early strength agent in sequence at a stirring speed of 30 r / min-60 r / min. Continue stirring for 30 s-80 s, and finally add silicate solution. Stir at a speed of 45 r / min-100 r / min for 60 s-300 s until the solution is fully mixed and homogeneous.

[0090] III. Filter the solution obtained in step II through a 100-mesh sieve. Dry the filtrate under vacuum at a negative pressure of 0.1 MPa and a temperature of 95-105℃ for 12 hours. Grind the filtrate until it passes through a 200-mesh sieve.

[0091] Comparative Examples 1-2: A functional admixture for concrete

[0092] The functional additives in Comparative Examples 1-2 are in liquid form, and their raw material compositions are shown in Table 1. Comparative Example 1 uses No. 1 hydrated calcium silicate guiding solution, prepared by the following method:

[0093] I. Prepare each raw material according to the mass parts shown in Table 1, where 1 mass part = 1 kg;

[0094] II. Add water to the mixer, and then add fumed nano silica, hydrated calcium silicate guiding solution, fatty acid salt surfactant, hydrated calcium silicate guiding solution, fluorosilicate, air-entraining agent, retarder, defoamer and early strength agent in sequence at a stirring speed of 30 r / min-60 r / min. Continue stirring for 30 s-80 s, and finally add silicate solution. Stir at a speed of 45 r / min-100 r / min for 60 s-300 s until the solution is fully mixed and homogeneous.

[0095] III. Filter the solution obtained in step II through a 100-mesh sieve. The filtrate is the liquid functional additive.

[0096] Table 1. Raw material composition of Examples 1-6 and Comparative Examples 1-2

[0097]

[0098] Examples 7-12: A type of concrete

[0099] The concretes of Examples 7-12 each contained the raw materials shown in Table 2, and also included the functional admixtures of Examples 1-6.

[0100] The concrete preparation methods for Examples 7-9 and 11-12 are as follows:

[0101] 1) Before use, store the functional admixture and concrete mix at room temperature (20±2℃) for at least 24 hours.

[0102] 2) Clean the inside of the concrete mixer to ensure that the surface is free of dirt, oil stains, grease, or other contaminants that reduce adhesion.

[0103] 3) Weigh out cement, fly ash, slag powder, coarse aggregate, fine aggregate, and water-reducing agent according to the mass proportions shown in Table 2 (1 mass proportion = 1 kg), and put them into a mixer. Mix and premix for 30s to 90s. Then add functional admixtures and water as shown in Table 2 and mix for 60s to 250s until all raw materials are evenly mixed.

[0104] The method for preparing the concrete in Example 10 is as follows:

[0105] 1) Before use, store the functional admixture and concrete mix at room temperature (20±2℃) for at least 24 hours.

[0106] 2) Clean the inside of the concrete mixer to ensure that the surface is free of dirt, oil stains, grease, or other contaminants that reduce adhesion.

[0107] 3) Weigh out cement, fly ash, slag powder, coarse aggregate, water-reducing agent and functional admixture of Example 4 according to the mass parts shown in Table 2 (1 mass part = 1 kg), and put them into a mixer. Mix and premix for 30s to 90s, then add the water shown in Table 2 and mix for 60s to 250s until all raw materials are mixed evenly; this is the final product.

[0108] Comparative Examples 3-6: A type of concrete

[0109] The raw material composition of the concrete in Comparative Examples 3-6 is shown in Table 2; wherein, Comparative Example 3 includes the functional admixture of Comparative Example 1, Comparative Example 4 includes the functional admixture of Comparative Example 2, Comparative Example 5 uses a commercially available penetrating crystallizing waterproofing agent as an admixture, and Comparative Example 6 does not include any admixture.

[0110] The preparation methods for the concrete in Comparative Examples 3-6 are as follows:

[0111] 1) Before use, store the functional admixture and concrete mix at room temperature (20±2℃) for at least 24 hours.

[0112] 2) Clean the inside of the concrete mixer to ensure that the surface is free of dirt, oil stains, grease, or other contaminants that reduce adhesion.

[0113] 3) Weigh out cement, fly ash, slag powder, coarse aggregate, fine aggregate, water-reducing agent, etc. according to the mass parts shown in Table 2 (1 mass part = 1 kg), put them into the mixer, and mix for 30s to 90s. Then add or not add admixtures and water as shown in Table 2, and mix for 60s to 250s until all raw materials are evenly mixed.

[0114] Table 2 Concrete composition of Examples 7-12 and Comparative Examples 3-6

[0115]

[0116]

[0117] a : Penetrating crystallizing additive.

[0118] Test example:

[0119] 1. Macroscopic property determination of concrete prepared in each embodiment and comparative example

[0120] Precast concrete samples for Examples 7-12 and Comparative Examples 3-6 were prepared in accordance with the "Standard for Test Methods of Performance of Ordinary Concrete Mixtures" GB / T50080-2019 and the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" GB / T50081-2019 to obtain precast concrete.

[0121] The strength, electrical flux, chloride ion permeability resistance, frost resistance, compressive strength recovery rate, and self-healing ability of the precast concrete prepared above were measured in accordance with the following standards: GB / T 17671-2021 "Test Method for Strength of Cement Mortar", DL / T5126-2001 "Test Procedure for Polymer Modified Cement Mortar", GB / T50082-2019 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete", TB 10425-2019 "Standard for Strength Testing and Evaluation of Railway Concrete", and T / CECS1004-2022 "Technical Specification for Rigid Waterproofing Engineering". The results are shown in Table 3.

[0122] Table 3. Concrete performance test results for each embodiment and comparative example.

[0123]

[0124] Table 3 shows that the compressive strength of the concrete prepared in Examples 7-12 at all ages was significantly higher than that of the comparative example, the water absorption rate was approximately 1%, the electrical flux was less than 400C, and the chloride ion permeability resistance coefficient was less than 0.5×10⁻⁶. -12 The additive exhibits advantages such as a relative dynamic modulus of elasticity greater than 95% for frost resistance, a mass loss rate less than 1.5%, a compressive strength recovery rate greater than 95%, and a self-healing ability greater than 110%. These data demonstrate that the functional admixture of this invention can improve the compressive strength of concrete, significantly reduce the water absorption rate, electrical flux, and chloride ion permeability coefficient of concrete, thereby improving its impermeability, frost resistance, and durability.

[0125] Compared with the examples, in Comparative Example 3, the admixture of Comparative Example 1 was used in the concrete; in Comparative Example 4, the admixture of Comparative Example 2 was used; in Comparative Example 5, a conventional commercially available penetrating crystallization admixture was used; and Comparative Example 6 was a blank sample of concrete without any admixture. The other raw materials and their mass fractions were the same as those in the examples. However, the compressive strength of the concrete prepared in Comparative Examples 3-6 was significantly lower than that in Examples 1-6, the water absorption rate was greater than 2%, the electric flux was greater than 500 C, the chloride ion penetration coefficient was greater than 1.0×10 -12 , and the relative dynamic modulus of the frost resistance performance was less than 90% and the mass loss was greater than 2%.

[0126] 2. Comparison of the microscopic structures of the concrete in the examples and comparative examples

[0127] The gravel in the concrete mixture of Example 8 (including the functional admixture of Example 2) was sieved out using a 4.75-mm sieve, and then the sieved mixture was prepared into specimens with dimensions of 40 mm×40 mm×160 mm. The specimens were cured under the conditions of (20±2)°C and a humidity greater than 90%. Specimens at three ages of 3 d, 7 d, and 28 d were taken, and their microscopic structures were observed under an electron microscope (at a magnification of 5000 times). The electron microscope scanning photos at the three ages are shown in Figure 1 a-c.

[0128] Figure 1 It is shown that when the specimen prepared from the mortar of Example 8 was at the age of 3 d, there were tiny cracks ( Figure 1 a in it), and as the age increased, no cracks were found at the ages of 7 d and 28 d (see Figure 1 b and c in it respectively).

[0129] According to the same method, the gravel in the mixture of Comparative Example 6 was removed, and then specimens of the same specifications were prepared. The specimens were cured under the same conditions. Specimens at three ages of 3 d, 7 d, and 28 d were taken, and their microscopic structures were observed under an electron microscope (at a magnification of 5000 times). The electron microscope scanning photos at the three ages are shown in Figure 2 a-c.

[0130] Figure 2 It is shown that tiny cracks were found in the specimens prepared in Comparative Example 6 during the tests at the ages of 3 d ( Figure 2 a in it), 7 d ( Figure 2 b in it), and 28 d ( Figure 2 c in it).

[0131] The above results of macroscopic performance tests and microstructural characterization of concrete all indicate that the functional admixture of concrete involved in this invention can, on the one hand, effectively reduce micro-cracks inside the concrete structure and improve its structural density; on the other hand, it can significantly improve the compressive strength, water absorption, electrical flux, chloride ion permeability resistance, and freeze-thaw resistance of concrete, thereby improving the durability of concrete.

Claims

1. A functional admixture for improving concrete performance, made from the following raw materials in parts by weight: 80-120 parts silicate solution, 5-15 parts fumed nano silica, 0.5-1.5 parts fatty acid salt surfactant, 0.05-0.16 parts hydrated calcium silicate guiding solution, 0.2-0.6 parts fluorosilicate, 0.1-0.4 parts air-entraining agent, 0.1-0.3 parts defoamer, 0.5-1.0 parts early-strength agent, and 0.1-0.9 parts retarder; The silicate is selected from one or two of sodium silicate and potassium silicate in any proportion; the mass percentage concentration of the silicate solution is 20-40%. The fatty acid salt surfactant is selected from one or two of sodium stearate and potassium stearate in any proportion; The fluorosilicate is selected from at least one of magnesium fluorosilicate, zinc fluorosilicate, and potassium fluorosilicate; The defoamer is selected from polyether or silicone defoamers; The air-entraining agent is selected from methyl cellulose ether or rosin soap; The early strength agent is selected from at least one of calcium formate, sodium formate, sodium acetate, and calcium acetate; The retarder is selected from at least one of tartaric acid, borax, boric acid and aminated lignin; The hydrated calcium silicate guiding solution is prepared through the following steps: S1. Weigh 100 parts by weight of deionized water, and then, while stirring, uniformly disperse 0.5-2.0 parts by weight of CarbopolUltrez 21 in the deionized water and continue stirring for at least 2 hours to obtain a gel solution. S2. Weigh 15-20 parts by weight of calcium silicate hydrate crystals, 1.0-3.0 parts by weight of citric acid and 0.2-0.8 parts by weight of sodium tripolyphosphate, and add them sequentially to the gel solution prepared in step S1 while stirring, and continue stirring for no less than 30 minutes. S3. Weigh 0.2-0.5 parts by mass of triethanolamine and add it to the mixed solution prepared in step S2 while stirring. Continue stirring for no less than 15 minutes until a uniform gel emulsion is formed, which is the hydrated calcium silicate guiding solution. Improving concrete performance refers to increasing concrete compressive strength, self-healing ability, and freeze-thaw resistance, while reducing concrete water absorption, electrical flux, and chloride ion permeability coefficient.

2. The functional admixture for improving the performance of concrete according to claim 1, wherein Made from the following parts by weight of raw materials: 90-110 parts of silicate aqueous solution, 8-13 parts of fumed nano silica, 0.7-1.3 parts of fatty acid salt surfactant, 0.08-0.14 parts of hydrated calcium silicate guiding solution, 0.3-0.5 parts of fluorosilicate, 0.15-0.3 parts of air-entraining agent, 0.1-0.2 parts of defoamer, 0.6-0.9 parts of early-strength agent, and 0.2-0.7 parts of retarder; The hydrated calcium silicate guiding solution is prepared according to the steps described in claim 1.

3. The functional admixture for improving the performance of concrete according to claim 1 or 2, characterized in that, The loose packing density of the fumed silica nanoparticles is 0.15-0.2 g / cm³. 3 Fineness 200-500 mesh.

4. The functional admixture for improving concrete performance according to claim 1 or 2, characterized in that, The raw materials also include 100-130 parts by weight of water.

5. The functional admixture for improving concrete performance according to claim 3, characterized in that, The raw materials also include 100-130 parts by weight of water.

6. The functional admixture for improving concrete performance according to claim 4, characterized in that, The water is deionized water with a resistivity greater than or equal to 10 megohms per centimeter.

7. The functional admixture for improving concrete performance according to claim 5, characterized in that, The water is deionized water with a resistivity greater than or equal to 10 megohms per centimeter.

8. A method for preparing a solid functional admixture for improving concrete performance, comprising the following steps: I. Prepare the raw materials according to claim 1 or 2; II. Add 100-130 parts by weight of water to the mixer, and then add fumed nano silica, fatty acid salt surfactant, hydrated calcium silicate guiding solution, fluorosilicate, air-entraining agent, retarder, defoamer and early strength agent in sequence at a stirring speed of 30 r / min-60 r / min. Continue stirring for 30 s-80 s, and finally add silicate solution. Stir at a speed of 45 r / min-100 r / min for 60 s-300 s until the solution is fully mixed and homogeneous. III. Filter the mixture obtained in step II through a 100-mesh sieve, dry the filtrate under vacuum, and grind it until it all passes through a 200-mesh sieve to obtain the final product.

9. The production method according to claim 8, characterized by, In step III, the vacuum drying conditions are: negative pressure 0.1 MPa, vacuum drying at 95-105℃ for 5-10 hours.

10. A method for preparing a liquid functional admixture for improving concrete performance, comprising the following steps: I. Prepare the raw materials according to claim 4 or 5; II. Add the stated mass fraction of water to the mixer, and then add the fumed nano silica, fatty acid salt surfactant, hydrated calcium silicate guiding solution, fluorosilicate, air-entraining agent, retarder, defoamer and early strength agent in sequence at a stirring speed of 30 r / min-60 r / min. Continue stirring for 30 s-80 s, and finally add the silicate solution. Stir at a speed of 45 r / min-100 r / min for 60 s-300 s until the solution is fully mixed and homogeneous. III. Filter the mixture obtained in step II through a 100-mesh sieve. The filtrate is the liquid functional additive.

11. The application of the functional admixture according to any one of claims 1 to 7, the solid functional admixture prepared by the preparation method according to claim 8 or 9, or the liquid functional admixture prepared by the preparation method according to claim 10, in improving the performance of concrete.

12. Use according to claim 11, characterized in that, The amount of the solid functional admixture is 0.5%-2.5% of the cement mass.

13. The use according to claim 11, characterized in that, The amount of the liquid functional admixture is 1%-5% of the total mass of the concrete cementitious materials.

14. A high-density concrete with self-healing crack function, comprising the functional admixture according to any one of claims 1 to 7, a solid functional admixture prepared by the preparation method according to claim 8 or 9, or a liquid functional admixture prepared by the preparation method according to claim 10.

15. The method for preparing concrete with high density and self-healing crack function as described in claim 14, comprising the following operations: Place the concrete mix and the solid functional admixture at 5-40℃ for at least 24 hours; clean the inside of the mixer to ensure that the surface is free of dirt and / or grease; add all raw material components of the concrete except water and the solid functional admixture to the mixer, premix for 30s-90s, then add mixing water and mix for 60s-250s until all raw materials are evenly mixed to obtain the final product. or Place the concrete mix and the liquid functional admixture at 5-40℃ for at least 24 hours; clean the inside of the mixer to ensure that the surface is free of dirt and / or grease; add all raw material components of the concrete except water to the mixer, premix for 30s-90s, then add the liquid functional admixture and mixing water, and stir for 60s-250s until all raw materials are evenly mixed to obtain the final product.

16. The method of claim 15, wherein, The dirt was all oil stains.

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