A waterproof emulsion modified gradient slow-release type hydration temperature control anti-cracking agent and a preparation method and application thereof

Abstract

The application discloses a waterproof emulsion modified gradient release type hydration temperature control anti-cracking agent and a preparation method and application thereof, and belongs to the technical field of concrete functional admixtures. The application takes organic silicon modified acrylate waterproof emulsion as a core modified component, constructs a four-element synergic system of phase change heat storage-retardation temperature control-waterproof anti-permeation-toughening anti-cracking through secondary hydrophobic modification of a carrier and shell layer grafting copolymerization double processes, and the temperature control anti-cracking agent comprises, in terms of weight parts, 18-22 parts of a phase change heat storage temperature control component, 8-12 parts of a gradient retarding component, 12-18 parts of the organic silicon modified acrylate waterproof emulsion and the like. The application can simultaneously solve two core diseases of hydration heat temperature cracking and permeation erosion of mass concrete, the reduction range of a hydration peak temperature is greater than or equal to 35%, the concrete impermeability grade can be greater than or equal to P12, the 28-day compressive strength retention rate is greater than or equal to 100%, and the application is suitable for various mass concrete projects such as water conservancy, bridges, super high-rise buildings and underground pipe galleries.

Description

Technical Field

[0001] This invention belongs to the technical field of functional admixtures for concrete, specifically relating to a waterproof emulsion-modified gradient slow-release hydration temperature-inhibiting and crack-resistant agent, as well as its preparation method and application in large-volume concrete. Background Technology

[0002] Mass concrete is a core structural material for major infrastructure projects such as water conservancy projects, cross-sea bridges, super high-rise buildings, and underground utility tunnels. During its service life, it faces two major long-term problems:

[0003] First, temperature cracking. During the cement hydration process, clinker minerals such as C3S and C3A release hydration heat 6-48 hours after pouring, causing the highest internal temperature of the concrete to reach 70℃-90℃, with a temperature difference of more than 30℃ from the surface. This results in penetrating temperature cracks, which seriously reduce the overall integrity and durability of the structure.

[0004] Second, seepage and erosion. After the concrete hardens, the capillary channels inside will form a continuous seepage path. Under the action of corrosive media such as groundwater, chloride ions, and sulfates, it will cause problems such as structural leakage, steel corrosion, and concrete deterioration. Temperature cracks will further expand the seepage channels, forming a vicious cycle of "crack-seepage" and significantly shortening the service life of the structure.

[0005] Existing solutions to the above problems suffer from three major insurmountable technical bottlenecks:

[0006] Firstly, their functions are limited, failing to simultaneously address both heat suppression and waterproofing / crack resistance. Existing hydration heat suppressants only focus on regulating hydration heat and reducing temperature peaks, failing to solve the problem of concrete impermeability and waterproofing. Some encapsulated heat suppressants even increase the internal porosity of concrete, leading to a 10%-15% decrease in impermeability. On the other hand, conventional concrete waterproofing agents can only achieve impermeability by sealing capillaries, without any regulation of cement hydration heat release, thus failing to achieve multiple functions in one agent. In engineering projects, heat suppressants and waterproofing agents need to be added separately, which not only increases construction costs but also easily leads to component compatibility conflicts.

[0007] Secondly, the components have poor compatibility and insufficient synergistic effect. Existing technologies attempt to simply physically combine waterproofing components with temperature-suppressing components, but the interfacial compatibility between organic waterproofing emulsions and inorganic carriers and microcapsule shells is extremely poor. In alkaline concrete mixing systems, problems such as demulsification, stratification, and agglomeration easily occur. Not only does this fail to achieve the waterproofing effect, but it also leads to uncontrolled release of the retarding components, with the temperature-suppressing and slow-release performance decreasing by more than 30%. It is impossible to achieve functional synergy through chemical grafting modification.

[0008] Third, the controlled release and crack resistance performance cannot be balanced. In order to achieve long-term slow release, traditional retarding temperature inhibitors often excessively prolong the initial setting time of concrete, resulting in slow early strength development and decreased early crack resistance. On the other hand, the addition of crack-resistant components will interfere with the release rate of the retarder, making it impossible to achieve a balance of multiple properties such as hydration temperature inhibition, gradient slow release, strength development, crack resistance and impermeability.

[0009] In summary, there is an urgent need to develop a composite admixture that combines multiple functions such as hydration and temperature suppression, gradient slow release, waterproofing and seepage prevention, and toughening and crack resistance, so as to fundamentally solve the problem of synergistic treatment of "temperature cracking" and "seepage cracking" in large-volume concrete. Summary of the Invention

[0010] 1. Technical problems to be solved

[0011] The purpose of this invention is to overcome the above-mentioned defects of the prior art and solve the following technical problems:

[0012] (1) Existing technologies cannot simultaneously achieve both hydration-induced temperature suppression and waterproofing and seepage prevention. Simple compounding can easily lead to problems such as matching conflicts and performance degradation.

[0013] (2) The organic waterproofing components have poor compatibility with the inorganic temperature-suppressing system, and cannot achieve functional synergy through chemical grafting;

[0014] (3) Traditional temperature suppressants have poor slow-release stability and are prone to early strength loss, making it impossible to achieve a balance of multiple properties.

[0015] 2. Technical Solution

[0016] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0017] A waterproof emulsion-modified gradient slow-release hydration temperature-inhibiting and crack-resistant agent, by weight, is composed of the following components: 18-22 parts of phase change heat storage and temperature-inhibiting component, 8-12 parts of gradient retarding component, 12-18 parts of organosilicon-modified acrylic waterproof emulsion, 25-32 parts of nano-reinforced composite carrier, 8.8-13.2 parts of temperature-sensitive slow-release shell layer component, and 8-12.5 parts of functional auxiliary component;

[0018] The phase change heat storage and temperature suppression component is a binary eutectic of decanoic acid and palmitic acid with a mass ratio of 7:3, and its phase change temperature is 34℃-39℃, and its latent heat of phase change is ≥190J / g.

[0019] The gradient retarding component is a composition of 7-10 parts aminotrimethylenephosphonic acid and 1-2 parts sodium tetraborate;

[0020] The silicone-modified acrylic waterproof emulsion has a solid content of 38%-42%, a glass transition temperature of -5℃, a water absorption rate of ≤5%, and a pH value of 7.0-8.0.

[0021] The nano-reinforced composite carrier is a diatomaceous earth-expanded perlite composite powder modified with a silane coupling agent and further hydrophobically modified with the organosilicon-modified acrylate waterproof emulsion, wherein the mass ratio of diatomaceous earth to expanded perlite is 2:1.

[0022] Furthermore, the temperature-sensitive slow-release shell component, by weight, consists of 5-7 parts of waterborne polyurethane prepolymer, 3-5 parts of melamine-formaldehyde resin prepolymer, and 0.8-1.2 parts of temperature-sensitive monomer N-isopropylacrylamide; the solid content of the waterborne polyurethane prepolymer is 30%, and the mass content of isocyanate groups is 8%-10%.

[0023] Furthermore, the nano-reinforced composite carrier is a 300-mesh powder with a porosity ≥50%; the silane coupling agent is γ-aminopropyltriethoxysilane, and the modification amount is 3% of the mass of the diatomite-expanded perlite composite powder.

[0024] Furthermore, the functional auxiliary components, by weight, consist of 1.5-2.5 parts Tween-60, 2-3 parts polycarboxylate dispersant, 4-6 parts metakaolin, and 0.5-1 parts polypropylene fiber; the specific surface area of ​​the metakaolin is ≥2000m² / kg, and the length of the polypropylene fiber is 6-12mm, and the diameter is 10-20μm.

[0025] This invention also provides a method for preparing the above-mentioned waterproof emulsion modified gradient slow-release hydration temperature-inhibiting and crack-resistant agent, comprising the following steps:

[0026] S1. Preparation of silane-modified composite carrier: Diatomaceous earth and expanded perlite were mixed at a mass ratio of 2:1, and 3% γ-aminopropyltriethoxysilane ethanol-water solution was added. The solid-liquid ratio was 1:6. The mixture was stirred at 65℃ for 2.5h, filtered, washed twice with anhydrous ethanol, and dried at 110℃ until the water content was <1% to obtain the silane-modified composite carrier.

[0027] S2. Secondary hydrophobic modification of waterproof emulsion: Take 6-8 parts of silicone-modified acrylic waterproof emulsion, dilute with deionized water to a solid content of 20%, adjust the pH value to 7.5, add the silane-modified composite carrier obtained in step S1, stir at 40℃ for 1 hour, filter and dry at 80℃ until the water content is <1% to obtain the hydrophobic modified composite carrier.

[0028] S3. Preparation of phase change-retarded core emulsion: Take the decanoic acid-palmitic acid binary eutectic material according to the formula, heat it to 45℃-50℃ to melt, add aminotrimethylenephosphonic acid and sodium tetraborate, stir at 500 rpm for 15 min to obtain a homogeneous oil phase; add Tween-60 and deionized water to the oil phase, emulsify at 10000 rpm for 20 min to obtain an O / W type core emulsion with a particle size of 1-5 μm;

[0029] S4. Preparation of waterproof emulsion grafted modified microcapsules: The core emulsion obtained in step S3 was transferred into a polymerization reactor, heated to 40°C, and waterborne polyurethane prepolymer and melamine-formaldehyde resin prepolymer were added. The pH value was adjusted to 8.5-9.0 with 10% sodium hydroxide solution. N-isopropylacrylamide was added and stirred at 300 rpm for 30 min. The remaining 6-10 parts of silicone-modified acrylate waterproof emulsion were added and stirred for 20 min to make the emulsion uniformly dispersed at the oil-water interface. The pH value was adjusted to 4.5-5.0 by slowly adding 10% citric acid solution. The temperature was raised to 60°C and kept at the temperature for 2 h for polymerization. After the reaction was completed, the mixture was centrifuged at 3000 rpm for 10 min. The precipitate was washed three times with deionized water and dried at 80°C to constant weight to obtain waterproof modified thermosensitive microcapsules.

[0030] S5. Finished Product Shaping: Take the hydrophobic modified composite carrier prepared in step S2 and the waterproof modified thermosensitive microcapsules prepared in step S4 according to the formula, mix them with polycarboxylate dispersant, metakaolin, and polypropylene fiber, grind them in a planetary ball mill at 300 rpm for 15-20 min, and pass them through a 150-mesh sieve to obtain a finished powder with a particle size of 50-200 μm.

[0031] Furthermore, in step S1, the volume ratio of ethanol to water in the ethanol-water solution is 9:1; and in step S3, the volume ratio of oil phase to water phase is 1:1.2.

[0032] This invention also provides the application of the above-mentioned waterproof emulsion modified gradient slow-release hydration temperature-inhibiting and crack-resistant agent in large-volume concrete, wherein the temperature-inhibiting and crack-resistant agent is added at 3.0%-4.5% of the total mass of concrete cementitious materials; the cementitious materials are any one of silicate cement, slag silicate cement, and medium-low heat silicate cement.

[0033] Furthermore, the temperature-inhibiting and crack-resistant agent is incorporated as follows: after being dry-mixed with the cementitious material for 60 seconds, the mixing water is added, and the mixing time is extended by 2-3 minutes compared to conventional concrete to ensure uniform dispersion of the components.

[0034] Furthermore, the large-volume concrete includes concrete for hydraulic dams, concrete for the abutments of cross-sea bridges, concrete for the raft foundations of super high-rise buildings, concrete for underground integrated pipe corridors, and concrete for the foundations of nuclear power projects.

[0035] 3. Beneficial effects

[0036] Compared with the prior art, the present invention has the following outstanding advantages:

[0037] (1) Achieving multi-performance integration and synergy, filling the technological gap in the industry. This invention is the first to construct a four-element synergistic system of "phase change heat storage - retarding and temperature suppression - waterproofing and seepage prevention - toughening and crack resistance" through dual modification of organosilicon-modified acrylic waterproof emulsion. At the same time, it solves the two core diseases of "temperature cracking" and "seepage cracking" in large-volume concrete. The product's hydration peak temperature is reduced by ≥35%, and can reach up to 39.2%. The concrete impermeability grade can reach P12 or above, and the early crack reduction rate is ≥98%. It achieves multiple functions in one agent and avoids the combination conflict of multi-component compounding.

[0038] (2) Breaking through the technical bottleneck of component compatibility and achieving functional synergy. This invention innovatively designs a dual process of "carrier secondary hydrophobic modification + shell graft copolymerization": On the one hand, a hydrophobic graft membrane with covalent bonds is formed on the surface of the carrier pores by waterproof emulsion, which not only retains the high adsorption performance of the carrier, but also gives it hydrophobic properties, thereby reducing the internal water seepage channels of concrete from the source; on the other hand, an interpenetrating network shell is formed by graft copolymerization of waterproof emulsion and waterborne polyurethane-melamine formaldehyde resin, which not only improves the stability of microcapsules in the alkaline environment of concrete (7-day degradation rate <3%), but also achieves gradient slow release through temperature-sensitive monomers. The slow release cycle accurately covers the exothermic peak period of cement hydration of 12-36 hours, avoiding the sudden release and excessive slow setting of the retarding component.

[0039] (3) Achieving a balance of performance and excellent engineering adaptability. This invention avoids early strength loss caused by a single retarder by using a gradient retarding compound of aminotrimethylene phosphonic acid and sodium tetraborate, combined with the physical heat absorption of phase change heat storage components. Through the synergistic toughening of hydrophobic modified carrier, metakaolin, and polypropylene fiber, the 3-day compressive strength retention rate of concrete is ≥93%, and the 28-day compressive strength is increased by more than 4% compared with the blank group, which completely solves the industry pain point of traditional temperature suppressing agents that "retardation and strength cannot be taken into account". The product is suitable for various complex working conditions such as normal temperature, high temperature, high humidity, and high corrosion risk, and can be widely used in various large-volume concrete projects.

[0040] (4) Green and environmentally friendly, economically efficient, and suitable for industrial mass production. The production process of this invention is free of organic solvents and toxic and harmful byproducts, which meets the requirements of the national green building materials policy; the core modified component uses self-produced organosilicon modified acrylic waterproof emulsion, the raw material cost is controllable, the process parameters are stable, and the single batch capacity can reach more than 5 tons, which is suitable for industrial continuous production. Detailed Implementation

[0041] The present invention will be further described in detail below with reference to specific embodiments. The following embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention; non-creative modifications made by those skilled in the art based on the core concept of the present invention are all within the scope of protection of the present invention.

[0042] Unless otherwise specified, all raw materials and reagents used in the embodiments of this invention are commercially available industrial-grade products; the organosilicon-modified acrylate waterproof emulsion used is produced by the company itself, and its complete preparation method is as follows:

[0043] By weight, 35 parts of butyl acrylate, 15 parts of methyl methacrylate, 8 parts of organosiloxane monomer (KH570), 2 parts of acrylic acid, 2 parts of emulsifier OP-10, 0.5 parts of initiator ammonium persulfate, and 40 parts of deionized water were taken. All monomers, emulsifiers, and 30 parts of deionized water were mixed and sheared at 3000 rpm for 30 min to obtain a pre-emulsion. The remaining 10 parts of deionized water were added to the reactor, heated to 80℃, and the pre-emulsion and ammonium persulfate solution were added dropwise. The addition was completed in 3 h. The reactor was kept at 80℃ for 4 h for polymerization. The reactor was cooled to room temperature, and the pH value was adjusted to 7.0-8.0 with triethanolamine. The mixture was filtered through a 200-mesh filter to obtain an organosilicon-modified acrylic waterproof emulsion with a solid content of 40%. The glass transition temperature was -5℃ and the water absorption rate was ≤5% after 24 h, which met the requirements of the formulation of this invention.

[0044] The concrete foundation mix proportion used in this embodiment of the invention is designed with reference to GB 50164-2011 "Standard for Quality Control of Concrete", and is the benchmark mix proportion for C40 mass concrete. Specifically, it is: 340 kg / m³ of P·O 42.5 silicate cement, 80 kg / m³ of S95 grade fly ash, 735 kg / m³ of medium sand with a fineness modulus of 2.7, 1100 kg / m³ of 5-25mm continuously graded crushed stone, 155 kg / m³ of mixing water, and 1.10 kg / m³ of polycarboxylate-based high-efficiency water-reducing agent (20% solid content).

[0045] All performance tests in this invention embodiment adopt current national / industry standards, as detailed below:

[0046] Cement hydration heat test: GB / T 12959-2021 "Method for Determination of Cement Hydration Heat";

[0047] Concrete mechanical property testing: GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete";

[0048] Concrete impermeability test: GB / T 50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete";

[0049] Performance testing of concrete mixtures: GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures";

[0050] Concrete crack testing: Appendix B of GB / T 50666-2011 "Code for Construction of Concrete Structures".

[0051] Example 1

[0052] This embodiment provides a waterproof emulsion-modified gradient slow-release hydration temperature-inhibiting and crack-resistant agent, which, by weight, comprises: 20 parts of decanoic acid-palmitic acid binary eutectic, 8 parts of aminotrimethylenephosphonic acid, 1.5 parts of sodium tetraborate, 15 parts of organosilicon-modified acrylic waterproof emulsion (of which 8 parts are used for secondary hydrophobic modification of the carrier and 7 parts are used for shell graft copolymerization), 30 parts of silane-modified composite carrier, 6 parts of waterborne polyurethane prepolymer, 4 parts of melamine-formaldehyde resin prepolymer, 1.0 part of N-isopropylacrylamide, 2.0 parts of Tween-60, 2.5 parts of polycarboxylate dispersant, 5 parts of metakaolin, and 0.8 parts of polypropylene fiber.

[0053] The specific steps of its preparation method are as follows:

[0054] S1. Preparation of silane-modified composite carrier: 300-mesh diatomaceous earth and expanded perlite were mixed at a mass ratio of 2:1, and 3% (w / w) of γ-aminopropyltriethoxysilane ethanol-water solution (ethanol to water volume ratio 9:1) was added. The solid-liquid ratio was 1:6, and the mixture was stirred at 65℃ for 2.5 h. After filtration, the mixture was washed twice with anhydrous ethanol and dried at 110℃ until the water content was <1%, thus obtaining the silane-modified composite carrier. The porosity was measured to be 52.3%.

[0055] S2. Secondary hydrophobic modification of waterproof emulsion: Take 8 parts of silicone-modified acrylic waterproof emulsion, dilute with deionized water to a solid content of 20%, adjust the pH value to 7.5 with triethanolamine, add the silane-modified composite carrier obtained in step S1, stir at 40℃ for 1 hour, filter and dry at 80℃ until the water content is <1% to obtain the hydrophobic modified composite carrier.

[0056] S3. Preparation of phase change-retarded core emulsion: The decanoic acid-palmitic acid binary eutectic was measured according to the formula, heated to 48℃ to melt, aminotrimethylenephosphonic acid and sodium tetraborate were added, and the mixture was stirred at 500 rpm for 15 min to obtain a homogeneous oil phase; Tween-60 and deionized water (oil phase to water phase volume ratio 1:1.2) were added to the oil phase, and the mixture was emulsified by high-speed shearing at 10000 rpm for 20 min to obtain an O / W type core emulsion with a particle size of 1-5 μm;

[0057] S4. Preparation of waterproof emulsion grafted modified microcapsules: The core emulsion obtained in step S3 was transferred to a polymerization reactor, heated to 40°C, and waterborne polyurethane prepolymer and melamine-formaldehyde resin prepolymer were added. The pH value was adjusted to 8.8 with 10% sodium hydroxide solution, and N-isopropylacrylamide was added. The mixture was stirred at 300 rpm for 30 min. Then, the remaining 7 parts of organosilicon-modified acrylate waterproof emulsion were added, and the mixture was stirred for 20 min to ensure that the emulsion was uniformly dispersed at the oil-water interface. The pH value was adjusted to 4.8 by slowly adding 10% citric acid solution. The mixture was heated to 60°C and kept at that temperature for 2 h for polymerization. After the reaction was completed, the mixture was centrifuged at 3000 rpm for 10 min, and the precipitate was washed three times with deionized water. The precipitate was dried at 80°C to constant weight to obtain waterproof modified temperature-sensitive microcapsules. The encapsulation rate was tested to be 96.2%.

[0058] S5. Finished Product Shaping: Take the hydrophobic modified composite carrier prepared in step S2 and the waterproof modified thermosensitive microcapsules prepared in step S4 according to the formula, mix them with polycarboxylate dispersant, metakaolin, and polypropylene fiber, grind them in a planetary ball mill at 300 rpm for 18 min, and pass them through a 150-mesh sieve to obtain a finished product with a particle size of 50-200 μm.

[0059] Example 2

[0060] This embodiment provides a waterproof emulsion-modified gradient slow-release hydration temperature-inhibiting and crack-resistant agent, the specific components of which are as follows (by weight):

[0061] 22 parts of decanoic acid-palmitic acid binary eutectic, 10 parts of aminotrimethylenephosphonic acid, 2 parts of sodium tetraborate, 18 parts of organosilicon-modified acrylic waterproof emulsion (8 parts of which are used for secondary hydrophobic modification of the carrier and 10 parts of which are used for shell graft copolymerization), 32 parts of silane-modified composite carrier, 7 parts of waterborne polyurethane prepolymer, 5 parts of melamine-formaldehyde resin prepolymer, 1.2 parts of N-isopropylacrylamide, 2.5 parts of Tween-60, 3 parts of polycarboxylate dispersant, 6 parts of metakaolin, and 1 part of polypropylene fiber.

[0062] Its preparation method is completely consistent with that of Example 1.

[0063] Example 3

[0064] This embodiment provides a waterproof emulsion-modified gradient slow-release hydration temperature-inhibiting and crack-resistant agent, the specific components of which are as follows (by weight):

[0065] 18 parts of decanoic acid-palmitic acid binary eutectic, 7 parts of aminotrimethylenephosphonic acid, 1 part of sodium tetraborate, 12 parts of organosilicon-modified acrylic waterproof emulsion (6 parts of which are used for secondary hydrophobic modification of the carrier and 6 parts of which are used for shell graft copolymerization), 25 parts of silane-modified composite carrier, 5 parts of waterborne polyurethane prepolymer, 3 parts of melamine-formaldehyde resin prepolymer, 0.8 parts of N-isopropylacrylamide, 1.5 parts of Tween-60, 2 parts of polycarboxylate dispersant, 4 parts of metakaolin, and 0.5 parts of polypropylene fiber.

[0066] Its preparation method is completely consistent with that of Example 1.

[0067] Example 4

[0068] This embodiment provides a waterproof emulsion-modified gradient slow-release hydration temperature-inhibiting and crack-resistant agent, the specific components of which are as follows (by weight):

[0069] 19 parts of decanoic acid-palmitic acid binary eutectic, 9 parts of aminotrimethylenephosphonic acid, 1.2 parts of sodium tetraborate, 16 parts of silicone-modified acrylic waterproof emulsion (7 parts of which are used for secondary hydrophobic modification of the carrier and 9 parts of which are used for shell graft copolymerization), 28 parts of silane-modified composite carrier, 5.5 parts of waterborne polyurethane prepolymer, 3.5 parts of melamine-formaldehyde resin prepolymer, 0.9 parts of N-isopropylacrylamide, 1.8 parts of Tween-60, 2.2 parts of polycarboxylate dispersant, 4.5 parts of metakaolin, and 0.6 parts of polypropylene fiber.

[0070] Its preparation method is completely consistent with that of Example 1.

[0071] Comparative Example 1

[0072] This comparative example is a blank control group. No hydration inhibitors or waterproofing agents were added to the concrete, and only the standard mix ratio was used.

[0073] Comparative Example 2

[0074] This comparative example is the company's previously submitted hydration temperature suppressant product, with the following specific components: 20 parts of decanoic acid-lauric acid binary eutectic, 8 parts of hydroxyethylidene diphosphonic acid, 30 parts of silane-modified diatomaceous earth-expanded perlite carrier, 6 parts of polyurea prepolymer, 4 parts of melamine-formaldehyde resin prepolymer, and 1.0 part of N-isopropylacrylamide. The preparation method is conventional interfacial polymerization, without a waterproof emulsion modification step.

[0075] Comparative Example 3

[0076] This comparative example is a simple physical compound sample of waterproof emulsion and early temperature suppressant. The components are: 90 parts of temperature suppressant from Comparative Example 2 and 10 parts of silicone-modified acrylic waterproof emulsion used in this invention. The mixture is prepared by physical mixing at 300 rpm for 20 minutes at room temperature.

[0077] Comparative Example 4

[0078] This comparative example is a sample without waterproof emulsion graft modification. Except for the absence of silicone-modified acrylate waterproof emulsion, the other components and preparation methods are the same as in Example 1.

[0079] Performance Testing and Result Analysis

[0080] The samples from Examples 1-4 and Comparative Examples 1-4 were all added to the reference concrete at 3.5% of the total mass of concrete cementitious materials. The specimens were molded in a standard environment at 25°C and various performance tests were conducted. The test results are shown in Table 1 below.

[0081] Performance indicators Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Maximum internal temperature of concrete / °C 48 49 51 49 79 55 62 56 % decrease in peak hydration temperature 39.2 38.0 35.4 38.0 - 30.4 21.5 29.1 Temperature peak occurrence time / h 34 36 30 32 14 28 18 26 Initial setting time / h 8.2 8.5 7.8 8.0 5.0 7.8 9.1 7.5 3-day compressive strength / MPa 32.3 31.8 31.5 32.0 34.0 29.3 27.2 30.1 3-day strength retention rate / % 95.0 93.5 92.6 94.1 100 86.2 80.0 88.5 28-day compressive strength / MPa 47.2 47.6 46.8 47.0 45.0 45.8 41.4 45.2 Concrete impermeability grade P12 P14 P12 P12 P6 P6 P8 P6 28-day water absorption rate / % 2.1 1.8 2.3 2.2 5.8 5.2 4.2 5.0 Early crack reduction rate / % 98.2 99.1 97.5 98.0 - 90.5 82.3 89.6

[0082] Table 1. Concrete performance test results of each embodiment and comparative example.

[0083] The following conclusions can be drawn from the test results:

[0084] 1. The hydration peak temperature of Examples 1-4 of the present invention is reduced by ≥35%, with a maximum of 39.2%, which is more than 8 percentage points higher than the previous product (Comparative Example 2); the temperature peak time is delayed to more than 30 hours, accurately covering the peak period of cement hydration heat release, and the hydration temperature suppression effect is significantly better than the existing technology.

[0085] 2. The concrete impermeability grade of the embodiment of the present invention can reach P12 or above, and the water absorption rate after 28 days is reduced by more than 60% compared with the blank group, which completely solves the defect of the previous product without waterproof function; while the comparative example 3 with simple physical compound not only failed to achieve the expected waterproof effect, but also had problems such as excessive retardation, strength reduction and temperature suppression effect decay, proving that the chemical grafting modification process of the present invention is the core of achieving functional synergy, and is essentially different from simple physical compound.

[0086] 3. The 3-day strength retention rate of the embodiments of the present invention is ≥92%, and the 28-day compressive strength is more than 4% higher than that of the blank group, achieving a balance between hydration temperature suppression and strength development, without the problems of excessive retardation and early strength loss; while the comparative example 4 without waterproof emulsion modification has significantly reduced temperature suppression effect, impermeability and crack resistance, proving that the dual modification of waterproof emulsion plays a key role in the comprehensive performance of the product.

[0087] 4. Embodiments 1-4 of the present invention cover the entire numerical range of the claims, proving that the technical solutions of the present invention can stably achieve the expected technical effects within the scope of protection of the claims, and the claims are fully supported by the specification.

[0088] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A waterproof emulsion-modified gradient slow-release hydration temperature-inhibiting and crack-resistant agent, characterized in that, By weight, it consists of the following components: 18-22 parts of phase change heat storage and temperature suppression component, 8-12 parts of gradient retarding component, 12-18 parts of organosilicon modified acrylic waterproof emulsion, 25-32 parts of nano-reinforced composite carrier, 8.8-13.2 parts of temperature-sensitive slow-release shell layer component, and 8-12.5 parts of functional auxiliary component. The phase change heat storage and temperature suppression component is a binary eutectic of decanoic acid and palmitic acid with a mass ratio of 7:3, and its phase change temperature is 34℃-39℃, and its latent heat of phase change is ≥190J / g. The gradient retarding component is a composition of 7-10 parts aminotrimethylenephosphonic acid and 1-2 parts sodium tetraborate; The silicone-modified acrylic waterproof emulsion has a solid content of 38%-42%, a glass transition temperature of -5℃, a water absorption rate of ≤5%, and a pH value of 7.0-8.

0. The nano-reinforced composite carrier is a diatomaceous earth-expanded perlite composite powder modified with a silane coupling agent and further hydrophobically modified with the organosilicon-modified acrylate waterproof emulsion, wherein the mass ratio of diatomaceous earth to expanded perlite is 2:

1.

2. The waterproof emulsion-modified gradient slow-release hydration temperature-inhibiting and crack-resistant agent according to claim 1, characterized in that, The thermosensitive sustained-release shell component, by weight, consists of 5-7 parts of waterborne polyurethane prepolymer, 3-5 parts of melamine-formaldehyde resin prepolymer, and 0.8-1.2 parts of thermosensitive monomer N-isopropylacrylamide; the solid content of the waterborne polyurethane prepolymer is 30%, and the mass content of isocyanate groups is 8%-10%.

3. The waterproof emulsion-modified gradient slow-release hydration temperature-inhibiting and crack-resistant agent according to claim 1, characterized in that, The nano-reinforced composite carrier is 300-mesh powder with a porosity ≥50%; the silane coupling agent is γ-aminopropyltriethoxysilane, and the amount of modification is 3% of the mass of the diatomite-expanded perlite composite powder.

4. The waterproof emulsion-modified gradient slow-release hydration temperature-inhibiting and crack-resistant agent according to claim 1, characterized in that, The functional auxiliary components, by weight, consist of 1.5-2.5 parts Tween-60, 2-3 parts polycarboxylate dispersant, 4-6 parts metakaolin, and 0.5-1 parts polypropylene fiber; the specific surface area of ​​the metakaolin is ≥2000m² / kg, and the length of the polypropylene fiber is 6-12mm, and the diameter is 10-20μm.

5. A method for preparing a waterproof emulsion-modified gradient slow-release hydration temperature-inhibiting and crack-resistant agent according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Preparation of silane-modified composite carrier: Diatomite and expanded perlite were mixed at a mass ratio of 2:1, and 3% γ-aminopropyltriethoxysilane ethanol-water solution was added. The solid-liquid ratio was 1:

6. The mixture was stirred at 65℃ for 2.5h, filtered, washed, and dried at 110℃ until the water content was <1% to obtain the silane-modified composite carrier. S2. Secondary hydrophobic modification of waterproof emulsion: Take 6-8 parts of silicone-modified acrylic waterproof emulsion, dilute with deionized water to a solid content of 20%, adjust the pH value to 7.5, add the silane-modified composite carrier obtained in step S1, stir at 40℃ for 1 hour, filter and dry at 80℃ until the water content is <1% to obtain the hydrophobic modified composite carrier. S3. Preparation of phase change-retarded core emulsion: Take the decanoic acid-palmitic acid binary eutectic material according to the formula, heat it to 45-50℃ to melt it, add aminotrimethylenephosphonic acid and sodium tetraborate, stir at 500 rpm for 15 min to obtain the oil phase; add Tween-60 and deionized water to the oil phase, emulsify at 10000 rpm for 20 min to obtain an O / W type core emulsion with a particle size of 1-5 μm; S4. Preparation of waterproof emulsion grafted modified microcapsules: The core emulsion obtained in step S3 was transferred into a polymerization reactor, heated to 40°C, and waterborne polyurethane prepolymer and melamine-formaldehyde resin prepolymer were added. The pH value was adjusted to 8.5-9.0, and N-isopropylacrylamide was added. The mixture was stirred at 300 rpm for 30 min. Then, the remaining 6-10 parts of organosilicon modified acrylate waterproof emulsion were added and stirred for 20 min. After stirring, 10% citric acid solution was added dropwise to adjust the pH value to 4.5-5.

0. The mixture was heated to 60°C and kept at that temperature for 2 h for polymerization. After the reaction was completed, the mixture was centrifuged, washed, and dried at 80°C to constant weight to obtain waterproof modified thermosensitive microcapsules. S5. Finished Product Shaping: Take the hydrophobic modified composite carrier prepared in step S2 and the waterproof modified thermosensitive microcapsules prepared in step S4 according to the formula, mix them with polycarboxylate dispersant, metakaolin, and polypropylene fiber, grind them in a planetary ball mill at 300 rpm for 15-20 min, and pass them through a 150-mesh sieve to obtain the finished powder.

6. The preparation method according to claim 5, characterized in that, In step S1, the volume ratio of ethanol to water in the ethanol-water solution is 9:1; in step S3, the volume ratio of oil phase to water phase is 1:1.

2.

7. The preparation method according to claim 5, characterized in that, In step S4, the pH value is adjusted to 8.5-9.0 using a 10% sodium hydroxide solution; the centrifugation parameters are 3000 rpm for 10 min; and the washing is performed three times with deionized water.

8. The application of a waterproof emulsion-modified gradient slow-release hydration temperature-inhibiting and crack-resistant agent according to any one of claims 1-4 in mass concrete, characterized in that, The temperature-inhibiting and crack-resistant agent is added at 3.0%-4.5% of the total mass of the concrete cementitious materials; the cementitious materials are any one of silicate cement, slag silicate cement, and medium-low heat silicate cement.

9. The application according to claim 8, characterized in that, The temperature-inhibiting and crack-resistant agent is incorporated as follows: after being dry-mixed with the cementitious material for 60 seconds, the mixing water is added, and the mixing time is extended by 2-3 minutes compared to conventional concrete.

10. The application according to claim 8, characterized in that, The large-volume concrete includes concrete for hydraulic dams, concrete for the foundation of cross-sea bridges, concrete for the raft foundation of super high-rise buildings, concrete for underground integrated pipe corridors, and concrete for the foundation of nuclear power projects.