Preparation and application of a pH-responsive sustained-release hydration heat inhibitor

Abstract

This invention discloses the preparation and application of a pH-responsive slow-release hydration heat inhibitor, belonging to the field of concrete admixture technology. This inhibitor slowly releases the inhibitor in the alkaline environment of the cement paste, continuously slowing down cement hydration and reducing the risk of temperature cracking in concrete due to hydration heat. Its core component is pH-responsive slow-release microspheres, composed of octadecyl acrylate, Span 80, Tween 60, white oil, acrylic acid, allyl polyoxyethylene ether 500, N,N-methylenebisacrylamide, deionized water, tert-butyl hydroperoxide, and sodium metabisulfite. It is prepared through steps such as mixing, emulsifying, and reacting the oil and water phases. The inhibitor also includes sorbitol and methanol, prepared through steps such as stirring, filtering, and drying. This inhibitor can effectively reduce the heat of cement hydration, delay setting time, and improve the compressive strength of concrete.

Description

Technical Field

[0001] This invention belongs to the field of concrete admixture technology, and particularly relates to the preparation and application of a pH-responsive slow-release hydration heat inhibitor. Background Technology

[0002] With societal progress and development, modern engineering construction has increasingly shifted towards large-scale projects, leading to the widespread application of large-volume concrete in fields such as water conservancy and hydropower, bridge abutments, and port construction. However, during the pouring and molding process, the hydration of cement in the concrete releases heat, causing a rapid rise in internal temperature. Depending on the size of the concrete structure, the internal temperature can reach as high as 70°C to 80°C. After a period of time, the internal temperature reaches its peak and gradually decreases. At this point, the heat exchange rate on the outer surface is faster, resulting in a lower internal temperature. This increased temperature difference between the internal and external surfaces leads to excessive temperature variations within the components, causing cracks and ultimately damaging the overall structure.

[0003] There are currently two main types of methods to address temperature cracking. One is to improve the heat dissipation effect by improving the construction process and adjusting the structural design, including: (1) using pre-cooled aggregates and mixing water to reduce the pouring temperature of concrete; (2) using cooling water pipes and surface coatings to reduce the internal and external temperature difference after concrete pouring. However, these methods increase the difficulty and cost of construction and pose a risk of reducing the strength of concrete. The other method is to reduce the cement hydration rate from the perspective of materials, including: (1) changing the materials to reduce the heat release of cement in concrete, such as using medium-heat or low-heat cement or adding mineral admixtures such as fly ash; (2) adding hydration heat inhibitors, such as sugars and their derivatives, starch dextrins, etc. However, changing the materials or adding phase change materials can easily lead to problems such as slow strength development and insufficient strength in the later stages.

[0004] Hydration heat inhibitors can reduce the hydration heat release peak, mitigate the risk of temperature cracking in construction, and are economical and convenient. Sugars and their derivatives, starch dextrins, sorbitol, etc., in the early stages of cement hydration, when cement and water mix, produce calcium hydroxide. The hydroxyl groups in the polysaccharides complex with calcium ions, adsorbing onto the surface of cement particles and preventing cement hydration. These hydration heat inhibitors can maintain the plasticity of concrete for a longer period, facilitating pouring, delaying the appearance of the cement hydration heat release peak, and mitigating the formation of temperature differences between the inside and outside of the matrix. However, delayed hydration affects cement setting time, thus affecting strength. High-dosage sucrose retarders can even exhibit a "delayed acceleration" phenomenon; therefore, these admixtures cannot effectively solve the problem of concrete temperature cracking caused by concentrated heat release during cement hydration.

[0005] Therefore, it is necessary to prepare a regulated, slow-release hydration heat-inhibiting material for large-volume concrete, which can be slowly released according to the hydration process to continuously slow down the cement hydration rate and achieve the goal of step-by-step regulation. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes the preparation and application of a pH-responsive slow-release hydration heat inhibitor. Stimulating the material to release slowly in the alkaline environment of cement paste continuously slows down cement hydration, alleviates the formation of temperature differences between the inside and outside of the matrix, and reduces the risk of cracking.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] One objective of this invention is to provide a pH-controlled release microsphere comprising the following components in parts by weight: 0.1-5 parts octadecyl acrylate, 1-10 parts Span 80, 1-10 parts Tween 60, 60-80 parts white oil, 1-30 parts acrylic acid, 1-10 parts allyl polyoxyethylene ether 500, 0.0001-5 parts N,N-methylenebisacrylamide, 20-40 parts deionized water, 0.0001-0.1 parts tert-butyl hydroperoxide, and 0.001-0.1 parts sodium metabisulfite.

[0009] Preferably, the pH-controlled microspheres comprise the following components in parts by weight: 1-3 parts octadecyl acrylate (preferably 1 or 3 parts), 3 parts Span 80, 2 parts Tween 60, 60 parts white oil, 30 parts acrylic acid, 1-15 parts allyl polyoxyethylene ether 500, 0.005-0.01 parts N,N-methylenebisacrylamide, 30 parts deionized water, 0.001 parts tert-butyl hydroperoxide, and 0.01 parts sodium metabisulfite.

[0010] The second objective of this invention is to provide a method for preparing pH-controlled microspheres, comprising the following steps:

[0011] Octadecyl acrylate, Span 80, and Tween 60 were dissolved in white oil to obtain the oil phase;

[0012] Acrylic acid, allyl polyoxyethylene ether 500, and N,N-methylenebisacrylamide were dissolved in deionized water to obtain an aqueous phase.

[0013] The oil phase and the aqueous phase were mixed, emulsified, and stirred. Then, tert-butyl hydrogen peroxide was added under a nitrogen atmosphere to react. Finally, sodium metabisulfite was added and the reaction was stirred. After the reaction was completed, the mixture was filtered, washed, and dried to obtain a white granular powder, namely pH slow-release microspheres.

[0014] Furthermore, the emulsification conditions are as follows: high-speed emulsification at 5000 rpm for 20 minutes.

[0015] Further, after adding tert-butyl hydroperoxide and reacting for 20 minutes, sodium metabisulfite was added, and the reaction was continued with stirring for 2-4 hours.

[0016] The third objective of this invention is to provide a pH-responsive sustained-release hydration heat inhibitor, comprising the following components in parts by weight: 10-60 parts pH sustained-release microspheres, 5-20 parts sorbitol and 60-100 parts methanol.

[0017] Furthermore, the pH-responsive sustained-release hydration heat inhibitor comprises the following components in parts by weight: 10-20 parts pH-response microspheres (preferably 10 or 20 parts), 20 parts sorbitol, and 60 parts methanol.

[0018] The fourth objective of this invention is to provide a method for preparing a pH-responsive sustained-release hydration heat inhibitor, comprising the following steps: adding sorbitol and pH-response microspheres to methanol, stirring, filtering, and drying to obtain a white granular powder, i.e., a pH-responsive sustained-release hydration heat inhibitor.

[0019] The fifth objective of this invention is to provide a pH-responsive slow-release hydration heat inhibitor as an admixture for use in concrete materials.

[0020] Furthermore, the dosage of the pH-responsive slow-release hydration heat inhibitor is 0.1-3% of the mass of the cementitious material.

[0021] The working principle of this invention's pH-responsive slow-release hydration heat inhibitor is as follows: As cement hydration progresses, the pH in the solution continuously rises. Alkaline solution gradually enters the pH-responsive slow-release hydration heat inhibitor, at which point the crystalline sorbitol dissolves, and simultaneously, the carboxyl groups in the cross-linked polyacrylic acid are ionized, causing the molecular chains to highly stretch and promoting the gradual expulsion of sorbitol from the microspheres. Meanwhile, the polymerized allyl polyoxyethylene ether 500 provides a certain degree of steric hindrance, controlling the slow-release rate of sorbitol. Sorbitol is gradually released as hydration progresses, and its hydroxyl groups complex with calcium ions, adsorbing onto the surface of cement particles and preventing further hydration. This slow-release mechanism avoids the inability to achieve sustained hydration inhibition due to insufficient sorbitol addition to concrete, while also preventing excessive sorbitol addition that could lead to excessive inhibition of hydration and severe delayed setting of the concrete.

[0022] Compared with the prior art, the present invention has the following advantages and technical effects:

[0023] This invention successfully solves the cracking problem caused by excessive heat of hydration in large-volume concrete through an innovative pH-responsive slow-release mechanism and optimized microsphere design, while also taking into account the requirements of setting time and mechanical properties. Its preparation method is simple and low-cost, and it has broad application prospects and significant economic and social benefits. Detailed Implementation

[0024] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0025] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0026] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0027] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0028] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0029] This invention provides a method for preparing a pH-responsive sustained-release hydration heat inhibitor, comprising the following steps:

[0030] (1) Preparation of pH sustained-release microspheres: By mass, oil phase preparation: 0.1-5 parts (for example, 1 part, 3 parts, or any number between 0.1-5 parts) of octadecyl acrylate, 1-10 parts (for example, 3 parts, or any number between 1-10 parts) of Span 80, and 1-10 parts (for example, 2 parts, or any number between 1-10 parts) of Tween 60 are dissolved in 60-80 parts (white oil is used as a solvent, the amount of which increases appropriately with the amount of solute; for example, 60 parts, or any number between 60-80 parts) of white oil; aqueous phase preparation: 1-30 parts (for example, 30 parts, or any number between 1-30 parts) of acrylic acid, 1-10 parts (for example, 1 part, 3 parts, or any number between 1-30 parts) of octadecyl acrylate, and 1-10 parts (for example, 1 part, 3 parts, or any number between 1-30 parts) of Tween 60 are dissolved in 60-80 parts (white oil is used as a solvent, the amount of which increases appropriately with the amount of solute; for example, 60 parts, or any number between 60-80 parts) of white oil; 500 parts, 2 parts, 5 parts, and any number between 1 and 10 parts) of allyl polyoxyethylene ether 500, 0.0001-5 parts (as an example, any number between 0.005 parts, 1 part, and any number between 0.0001 and 5 parts may be selected) of N,N-methylenebisacrylamide dissolved in 20-40 parts (deionized water as solvent, the amount of which increases appropriately with the increase of solute amount; as an example, any number between 30 parts and 20-40 parts may be selected) of deionized water; [The text abruptly ends here, likely due to an incomplete translation or a missing section.] The phase and aqueous phase are mixed and emulsified at 5000 rpm for 20 min. The mixture is then transferred to a 500 mL three-necked flask and stirred at 20-40 °C (for example, any temperature between 20 °C, 25 °C, and 20-40 °C can be selected). Nitrogen gas is introduced to remove oxygen for 10 min. 0.0001-0.1 parts (for example, any number between 0.001 parts and 0.0001-1 parts) of tert-butyl hydroperoxide are added for 20 min. Then, 0.001-0.1 parts (for example, any number between 0.01 parts and 0.001-1 parts) of sodium metabisulfite are added to the system and the mixture is stirred for 2-4 h (the stirring time can be appropriately extended as the amount of raw materials increases; for example, any time between 2 h, 4 h, and 2-4 h can be selected). After the reaction is complete, the microspheres are separated from cyclohexane by filtration, repeatedly washed with ethanol, and finally dried in a vacuum drying oven at 45 °C to obtain a white granular powder.

[0031] (2) Preparation of pH-responsive sustained-release hydration heat inhibitor: 5-20 parts (for example, any number between 20 and 5-20 parts) of sorbitol and 10-60 parts (for example, any number between 10, 20 and 10-60 parts) of pH sustained-release microspheres are added to 60-100 parts of methanol (methanol is used as solvent, and its mass fraction is appropriately increased with the increase of raw material amount; for example, any number between 60 and 60-100 parts) of methanol. Stir for 2-4 hours (for example, 3 hours). Then filter and dry the obtained filter residue in a vacuum drying oven at 45°C to obtain a white granular powder, which is the final product.

[0032] Unless otherwise specified, the term "parts" in this invention refers to parts by weight.

[0033] All raw materials used in this invention were purchased from the market.

[0034] The technical solution of the present invention will be further illustrated by the following embodiments.

[0035] Example 1

[0036] A method for preparing a pH-responsive sustained-release hydration heat inhibitor includes the following steps:

[0037] (1) Preparation of pH sustained-release microspheres: By mass, the oil phase was prepared by dissolving 1 part octadecyl acrylate, 3 parts Span 80, and 2 parts Tween 60 in 60 parts white oil; the aqueous phase was prepared by dissolving 30 parts acrylic acid, 1 part allyl polyoxyethylene ether 500, and 0.005 parts N,N-methylenebisacrylamide in 30 parts deionized water; the oil phase and aqueous phase were mixed and emulsified at 5000 rpm for 20 min, then transferred to a 500 mL three-necked flask, stirred at 20 °C, and nitrogen was introduced to remove oxygen for 10 min. After adding 0.001 parts tert-butyl hydrogen peroxide for 20 min, 0.01 parts sodium metabisulfite was added to the system and stirred for 2 h; after the reaction was completed, the microspheres were separated from cyclohexane by filtration, washed repeatedly with ethanol, and finally dried in a vacuum drying oven at 45 °C to obtain a white granular powder;

[0038] (2) Preparation of pH-responsive sustained-release hydration heat inhibitor: 20 parts of sorbitol and 20 parts of pH sustained-release microspheres were added to 60 parts of methanol and stirred for 3 hours. Then the mixture was filtered and dried in a vacuum drying oven at 45°C to obtain a white granular powder, which is the final product.

[0039] Example 2

[0040] A method for preparing a pH-responsive sustained-release hydration heat inhibitor includes the following steps:

[0041] (1) Preparation of pH sustained-release microspheres: By mass, the oil phase was prepared by dissolving 3 parts of octadecyl acrylate, 3 parts of Span 80, and 2 parts of Tween 60 in 60 parts of white oil; the aqueous phase was prepared by dissolving 30 parts of acrylic acid, 2 parts of allyl polyoxyethylene ether 500, and 0.005 parts of N,N-methylenebisacrylamide in 30 parts of deionized water; the oil phase and aqueous phase were mixed and emulsified at 5000 rpm for 20 min, then transferred to a 500 mL three-necked flask, stirred at 25 °C, and nitrogen was introduced to remove oxygen for 10 min. After adding 0.001 parts of tert-butyl hydrogen peroxide for 20 min, 0.01 parts of sodium metabisulfite were added to the system and stirred for 2 h; after the reaction was completed, the microspheres were separated from cyclohexane by filtration, washed repeatedly with ethanol, and finally dried in a vacuum drying oven at 45 °C to obtain a white granular powder;

[0042] (2) Preparation of pH-responsive sustained-release hydration heat inhibitor: 20 parts of sorbitol and 10 parts of pH sustained-release microspheres were added to 60 parts of methanol and stirred for 3 hours. Then the mixture was filtered and dried in a vacuum drying oven at 45°C to obtain a white granular powder, which is the final product.

[0043] Example 3

[0044] A method for preparing a pH-responsive sustained-release hydration heat inhibitor includes the following steps:

[0045] (1) Preparation of pH sustained-release microspheres: By mass, the oil phase was prepared by dissolving 3 parts of octadecyl acrylate, 3 parts of Span 80, and 2 parts of Tween 60 in 60 parts of white oil; the aqueous phase was prepared by dissolving 30 parts of acrylic acid, 5 parts of allyl polyoxyethylene ether 500, and 0.01 parts of N,N-methylenebisacrylamide in 30 parts of deionized water; the oil phase and aqueous phase were mixed and emulsified at 5000 rpm for 20 min, then transferred to a 500 mL three-necked flask, stirred at 25 °C, and nitrogen was introduced to remove oxygen for 10 min. After adding 0.001 parts of tert-butyl hydrogen peroxide for 20 min, 0.01 parts of sodium metabisulfite were added to the system and stirred for 4 h; after the reaction was completed, the microspheres were separated from cyclohexane by filtration, washed repeatedly with ethanol, and finally dried in a vacuum drying oven at 45 °C to obtain a white granular powder;

[0046] (2) Preparation of pH-responsive sustained-release hydration heat inhibitor: 20 parts of sorbitol and 10 parts of pH sustained-release microspheres were added to 60 parts of methanol and stirred for 3 hours. Then the mixture was filtered and dried in a vacuum drying oven at 45°C to obtain a white granular powder, which is the final product.

[0047] Comparative Example 1

[0048] Same as Example 1, except that the acrylic acid in the pH slow-release microspheres is replaced with acrylamide by mass, resulting in a pH slow-release hydration heat inhibitor that does not contain polyacrylic acid.

[0049] Comparative Example 2

[0050] Same as Example 1, except that the allyl polyoxyethylene ether 500 in the pH slow-release microspheres is replaced with acrylic acid by an equal mass, resulting in a pH slow-release hydration heat inhibitor that does not contain allyl polyoxyethylene ether 500.

[0051] Comparative Example 3

[0052] Same as Example 1, except that sorbitol and other substances were replaced with dextrin to prepare a pH-responsive hydration heat inhibitor.

[0053] Performance testing

[0054] The examples and comparative samples were incorporated into concrete for experiments. The concrete raw materials are shown below:

[0055] Cement: Esheng PO 42.5 cement; Sand: Manufactured sand, fineness modulus 2.7; Stone: Crushed pebbles with a particle size of 5-25mm. Water: Ordinary tap water. Water-reducing agent: GK-3000.

[0056] The concrete formula is shown in Table 1.

[0057] Table 1 Concrete mix proportions (kg / m³) 3 )

[0058] Material water cement fly ash sand Stone Water reducing agent pH-responsive sustained-release hydration heat inhibitor Dosage 170 290 70 805 1025 3.6 2.9

[0059] The setting time of concrete was tested according to GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures". The compressive strength ratio was tested according to GB / T 8076-2008 "Concrete Admixtures".

[0060] The thermal temperature rise of concrete was tested using an adiabatic temperature rise meter.

[0061] Concrete without pH-controlled hydration heat inhibitors was used as the baseline group.

[0062] The relevant performance test results are shown in Table 2.

[0063] Table 2 Performance Test Results

[0064] 1-day decrease in peak adiabatic temperature rise (°C) 7-day adiabatic temperature rise peak decrease (°C) Condensation time (h) 28-day compressive strength ratio (%) benchmark group / / 7.5 / Example 1 10 10 9.5 120 Example 2 8 8 9.0 115 Example 3 5 5 8.8 108 Comparative Example 1 / 15 28.0 70 Comparative Example 2 / 12 15.1 93 Comparative Example 3 0 0 7.4 100

[0065] Note: " / " in the table represents no detected value.

[0066] Combining Examples 1-3 and the baseline group, it can be seen that the examples begin to inhibit the temperature rise of concrete from day 1, and the setting time is slightly delayed. The compressive strength at 28 days is increased, indicating that the pH slow-release heat of hydration inhibitor of the present invention can effectively reduce the heat of hydration of cement and improve the mechanical properties of concrete.

[0067] Compared to Example 1, Comparative Example 1 is a product without polyacrylic acid, which lacks pH-responsive slow-release properties. This means that sorbitol dissolved in the solution is also released. No adiabatic temperature rise peak was observed at 1 day, but a peak appeared at 7 days, indicating an excessively strong retarding effect and a decrease in compressive strength. Comparative Example 2 is a product without allyl polyoxyethylene ether 500. No adiabatic temperature rise peak was observed at 1 day, but a peak appeared at 7 days, indicating a faster release rate compared to Example 1, a longer setting time, and a reduced strength. Comparative Example 3 involves replacing sorbitol with dextrin in the microsphere loading. Since dextrin is insoluble in methanol, it was not loaded onto the microspheres and therefore lacked hydration heat inhibition. The setting time was essentially the same as the baseline, and the strength remained unchanged.

[0068] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A pH-controlled release microsphere, characterized in that, The product comprises the following components in parts by weight: 0.1-5 parts octadecyl acrylate, 1-10 parts Span 80, 1-10 parts Tween 60, 60-80 parts white oil, 1-30 parts acrylic acid, 1-10 parts allyl polyoxyethylene ether 500, 0.0001-5 parts N,N-methylenebisacrylamide, 20-40 parts deionized water, 0.0001-0.1 parts tert-butyl hydroperoxide, and 0.001-0.1 parts sodium metabisulfite.

2. The pH-controlled microspheres according to claim 1, characterized in that, The pH-controlled release microspheres comprise the following components in parts by weight: 1-3 parts octadecyl acrylate, 3 parts Span 80, 2 parts Tween 60, 60 parts white oil, 30 parts acrylic acid, 1-5 parts allyl polyoxyethylene ether 500, 0.005-0.01 parts N,N-methylenebisacrylamide, 30 parts deionized water, 0.001 parts tert-butyl hydroperoxide, and 0.01 parts sodium metabisulfite.

3. A method for preparing pH-controlled microspheres as described in claim 1 or 2, characterized in that, Includes the following steps: Octadecyl acrylate, Span 80, and Tween 60 were dissolved in white oil to obtain the oil phase; Acrylic acid, allyl polyoxyethylene ether 500, and N,N-methylenebisacrylamide were dissolved in deionized water to obtain an aqueous phase. The oil phase and the aqueous phase were mixed, emulsified, and stirred. Then, tert-butyl hydrogen peroxide was added under a nitrogen atmosphere to react. Finally, sodium metabisulfite was added and the reaction was stirred. After the reaction was completed, the mixture was filtered, washed, and dried to obtain a white granular powder, namely pH slow-release microspheres.

4. The method for preparing pH sustained-release microspheres according to claim 3, characterized in that, The emulsification conditions were: emulsification at 5000 rpm for 20 minutes.

5. The method for preparing pH sustained-release microspheres according to claim 3, characterized in that, After adding tert-butyl hydroperoxide and reacting for 20 minutes, sodium metabisulfite is added, and the reaction is continued with stirring for 2-4 hours.

6. A pH-responsive sustained-release hydration heat inhibitor, characterized in that, The product comprises the following components in parts by weight: 10-60 parts of the pH-controlled microspheres as described in claim 1 or 2, 5-20 parts of sorbitol, and 60-100 parts of methanol.

7. The pH-responsive sustained-release hydration heat inhibitor according to claim 6, characterized in that, The pH-responsive sustained-release hydration heat inhibitor comprises the following components in parts by weight: 10-20 parts pH-response microspheres, 20 parts sorbitol, and 60 parts methanol.

8. A method for preparing a pH-responsive sustained-release hydration heat inhibitor as described in claim 6 or 7, characterized in that, Includes the following steps: Sorbitol and pH-controlled release microspheres were added to methanol, stirred, filtered, and dried to obtain a white granular powder, namely a pH-responsive controlled-release hydration heat inhibitor.

9. The application of a pH-responsive slow-release hydration heat inhibitor as described in claim 6 or 7 as an admixture in concrete materials.

10. The application according to claim 9, characterized in that, The dosage of the pH-responsive slow-release hydration heat inhibitor is 0.1-3% of the mass of the cementitious material.