A method for preparing a low-carbohydrate thermal rise inhibitor

Abstract

The application discloses a preparation method of a low-carbohydrate hydration temperature inhibitor, and relates to the technical field of concrete admixtures; the preparation method comprises the following steps: (1) dissolving Kraft lignin in tetrahydrofuran, then adding an alkali catalyst at room temperature, then adding a phosphating reagent, heating to a solvent reflux state, keeping for 8 hours, cooling to room temperature, quenching by adding water, and then sequentially performing rotary evaporation and drying to obtain phosphinylated Kraft lignin; (2) dissolving the phosphinylated Kraft lignin obtained in the step (1) and paraformaldehyde in a mixed solvent, adding an alkali catalyst at room temperature, stirring, heating to 60-70 DEG C and reacting for 2-6 hours, and cooling to room temperature to obtain the low-carbohydrate hydration temperature inhibitor. The application further includes the low-carbohydrate hydration temperature inhibitor prepared by the above method. The inhibitor has a good hydration temperature rising effect, can reduce the cracking risk of concrete caused by temperature drop shrinkage, and avoids cracking.

Description

Technical Field

[0001] This invention relates to the field of concrete admixture technology, specifically to a method for preparing a low-carbon hydration temperature rise inhibitor. Background Technology

[0002] The hydration reaction of cement is an exothermic reaction. This heat release, coupled with the low thermal conductivity of concrete, means that large-volume concrete may experience significant temperature differences, leading to substantial variations in setting time at different temperatures. This can result in crystallization defects, increasing the risk of cracking and ultimately affecting the durability of the concrete. In the course of social development, large-volume concrete is widely used in many fields due to its advantageous properties. However, cement hydration is prone to causing temperature cracks. Therefore, the development of cement hydration temperature rise inhibitors has become a key focus in concrete admixtures in recent years, and is of great significance for ensuring the quality of concrete construction and structural safety.

[0003] Currently available hydration temperature rise inhibitors have several shortcomings. In large-volume concrete applications, taking the construction of large bridge pier foundations as an example, even with the use of inhibitors, the internal temperature will still rise to some extent; only the rate of temperature rise is reduced, and the problem cannot be fundamentally eliminated. In high-temperature environments, such as during summer construction, the performance of inhibitors is significantly limited, making it difficult to effectively control the magnitude of hydration temperature rise. From the perspective of its impact on concrete performance, it may delay the formation of early concrete strength, which is undoubtedly an obstacle to meeting the requirements of construction tasks with urgent strength demands, such as rapid demolding of precast components. More importantly, some inhibitors may introduce components into the concrete that pose a potential threat to durability, leading to a decrease in the concrete's impermeability and frost resistance, thereby affecting the long-term stability and service life of the concrete structure. Furthermore, with population growth and increasing demand for energy and chemical materials, the demand for chemical polymers is increasing dramatically. Humanity faces the dual pressures of resource scarcity and environmental pollution, making green and low-carbon development crucial.

[0004] Therefore, there is an urgent need in this field to develop a concrete hydration heat inhibitor that is simple to prepare, green and low-carbon, and has excellent performance. By inhibiting the hydration temperature rise, it can reduce the risk of cracking caused by temperature drop and shrinkage in concrete, thereby achieving the purpose of crack resistance. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a method for preparing a low-carbon hydration temperature rise inhibitor. This inhibitor has a good hydration temperature rise effect, which can reduce the risk of cracking in concrete caused by temperature drop shrinkage and prevent cracking.

[0006] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for preparing a low-carbonization temperature rise inhibitor is provided, comprising the following steps:

[0007] (1) Dissolve kraft lignin in tetrahydrofuran, then add an alkaline catalyst at room temperature, then add a phosphating agent, heat to the solvent reflux state, maintain for 8 hours, cool to room temperature, quench with water, and then successively evaporate and dry to obtain phosphonylated kraft lignin.

[0008] The reaction process is as follows:

[0009]

[0010] (2) Dissolve the phosphonyl lignin and paraformaldehyde obtained in step (1) in a mixed solvent, add an alkaline catalyst at room temperature, stir at 200-500 r / min, heat to 60-70℃ for 2-6 h, cool to room temperature to obtain a low carbon hydration temperature rise inhibitor.

[0011] The reaction process is as follows:

[0012]

[0013] Furthermore, in step (1), the mass ratio of Kraft lignin, tetrahydrofuran, alkaline catalyst and phosphating agent is 10:30:0.1-0.3:1-3.

[0014] Furthermore, in step (1), the phosphating agent is one of the following: ammonium dihydrogen phosphate, phosphoric acid, tetraphosphate, trimethyl phosphite, and triethyl phosphite.

[0015] Further, in step (1), excess phosphating agent is quenched with water, tetrahydrofuran is removed by rotary evaporation, and the product is dried at 75°C.

[0016] Furthermore, in step (2), the mass ratio of phosphonyl lignin, paraformaldehyde, mixed solvent and alkaline catalyst is 10:5-15:30:0.1-0.3.

[0017] Furthermore, in step (2), the degree of polymerization of paraformaldehyde is 8-30.

[0018] Furthermore, in step (2), the mixed solvent is composed of deionized water and ethanol mixed in a mass ratio of 27:3.

[0019] Furthermore, in steps (1) and (2), the alkaline catalyst is one of sodium hydroxide, potassium hydroxide, calcium hydroxide, triethylamine, and N,N-dimethylacetamide.

[0020] The present invention also provides a low-carbon hydration temperature rise inhibitor prepared by the above-mentioned method.

[0021] The present invention has the following beneficial effects:

[0022] 1. Kraft lignin is a three-dimensional network polymer composed of phenylpropane units linked by ether and carbon-carbon bonds. It possesses air-entraining properties, introducing tiny, uniformly distributed air bubbles into concrete, improving its impermeability and freeze-thaw resistance, thereby enhancing its durability and extending the service life of concrete structures. Furthermore, Kraft lignin contains various active functional groups, including phenolic hydroxyl groups, which endow it with certain antioxidant capabilities. Kraft lignin also exhibits surface activity, improving the workability of concrete.

[0023] 2. After lignin is phosphonylated, it can slow down the cement hydration reaction rate and reduce the hydration heat release rate. The main principles are as follows: (1) Formation of protective film: Phosphonyl compounds can form a protective film on the surface of cement particles, preventing cement particles from fully contacting water, slowing down the hydration reaction rate of cement, and thus reducing the release rate of hydration heat; (2) Complexation: Phosphonyl groups can complex with metal ions in cement hydration products to form relatively stable complexes, reducing the number of ions that can participate in the hydration reaction, thereby delaying the hydration process of cement and reducing the hydration heat; (3) Adsorption: Phosphonyl groups have strong polarity and can be adsorbed on the surface of cement particles, changing the surface properties and charge distribution of cement particles, increasing the electrostatic repulsion between cement particles, improving dispersibility, hindering the agglomeration of cement particles and the formation of hydration products, and achieving the effect of reducing the hydration heat; (4) Delaying the formation and growth of crystal nuclei: The presence of phosphonyl groups will affect the formation and growth of crystal nuclei during the cement hydration process. It may be adsorbed on the surface of crystal nuclei, preventing the further growth and development of crystal nuclei, so that the hydration reaction of cement cannot proceed quickly, thereby reducing the generation of hydration heat.

[0024] 3. The condensation reaction of lignin and aldehydes enhances the inhibitory effect on cement hydration. The principle is as follows: (1) Formation of steric hindrance: After condensation of lignin and aldehydes, the molecular structure becomes larger and more complex, forming a thicker covering film on the surface of cement particles, which hinders the contact between cement particles and water, making it difficult for cement particles to fully hydrate, thus delaying the cement hydration process; (2) Consumption of hydroxyl groups: The condensation reaction consumes some of the hydroxyl groups in lignin, and hydroxyl groups can interact with calcium ions in cement to promote hydration. After their number decreases, the charge distribution on the surface of cement particles changes, and the electrostatic repulsion between particles increases. Adding cement particles disperses them, making them less likely to agglomerate and form hydration products, thus inhibiting cement hydration; (3) Changing the pore structure of cement: the condensation products fill the pores between cement particles, making the pores inside the cement smaller and more evenly distributed, hindering the migration and diffusion of water inside the cement, reducing the chance of cement contacting water, and thus inhibiting cement hydration; (4) Adsorption and retarding effect: the polar groups in the condensation products can be adsorbed on the surface of cement particles, preventing cement particles from contacting water. At the same time, its molecular chains can form complexes with the ions in the cement hydration products, delaying the formation and growth of cement crystal nuclei and inhibiting cement hydration.

[0025] 4. Lignin is a natural high-molecular polymer with wide availability. It can be extracted from waste materials in the papermaking industry, enabling effective resource reuse, reducing waste emissions, and aligning with environmental protection principles. Furthermore, the raw material cost of lignin-based additives is relatively low. Their main raw material, Kraft lignin, is a byproduct of the papermaking pulping process, with abundant sources and low prices. Secondly, lignin-based additives are non-toxic and harmless, and are not flammable or explosive hazardous materials. They offer high safety during storage, transportation, and use, and will not cause harm to human health or the environment. Attached Figure Description

[0026] Figure 1 The results are the hydration temperature rise performance test results of the mortars in Examples 1-7 and Comparative Examples 1-4. Detailed Implementation

[0027] The principles and features of this invention are described below. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0028] Example 1

[0029] A low-carbonation temperature rise inhibitor, the preparation method of which includes the following steps:

[0030] (1) Dissolve 10 parts of Kraft lignin in 30 parts of tetrahydrofuran, then add 0.2 parts of alkaline catalyst (sodium hydroxide) at room temperature, then add 1 part of phosphating agent (ammonium dihydrogen phosphate), heat to solvent reflux state, maintain for 8 hours, cool to room temperature, add water to quench excess phosphating agent, remove tetrahydrofuran by rotary evaporation, and dry at 75°C to obtain phosphonylated Kraft lignin;

[0031] (2) Dissolve 10 parts of phosphonylated kraft lignin obtained in step (1) and 5 parts of paraformaldehyde with a degree of polymerization of 8-12 in 30 parts of mixed solvent (deionized water and ethanol in a mass ratio of 27:3), add 0.2 parts of alkaline catalyst (sodium hydroxide) at room temperature, stir at 300 r / min, heat to 60 °C for 4 h, cool to room temperature, and obtain a low-carbon hydration temperature rise inhibitor.

[0032] Example 2

[0033] A low-carbonation temperature rise inhibitor, the preparation method of which includes the following steps:

[0034] (1) Dissolve 10 parts of Kraft lignin in 30 parts of tetrahydrofuran, then add 0.2 parts of alkaline catalyst (sodium hydroxide) at room temperature, then add 2 parts of phosphating agent (trimethyl phosphite), heat to solvent reflux state, maintain for 8 hours, cool to room temperature, add water to quench excess phosphating agent, remove tetrahydrofuran by rotary evaporation, and dry at 75°C to obtain phosphonylated Kraft lignin;

[0035] (2) Dissolve 10 parts of phosphonylated kraft lignin obtained in step (1) and 5 parts of paraformaldehyde with a degree of polymerization of 8-12 in 30 parts of mixed solvent (deionized water and ethanol in a mass ratio of 27:3), add 0.2 parts of alkaline catalyst (sodium hydroxide) at room temperature, stir at 300 r / min, heat to 60 °C for 4 h, cool to room temperature, and obtain a low-carbon hydration temperature rise inhibitor.

[0036] Example 3

[0037] A low-carbonation temperature rise inhibitor, the preparation method of which includes the following steps:

[0038] (1) Dissolve 10 parts of Kraft lignin in 30 parts of tetrahydrofuran, then add 0.2 parts of alkaline catalyst (potassium hydroxide) at room temperature, then add 3 parts of phosphating agent (trimethyl phosphite), heat to solvent reflux state, maintain for 8 hours, cool to room temperature, add water to quench excess phosphating agent, remove tetrahydrofuran by rotary evaporation, and dry at 75°C to obtain phosphonylated Kraft lignin;

[0039] (2) Dissolve 10 parts of phosphonylated kraft lignin obtained in step (1) and 5 parts of paraformaldehyde with a degree of polymerization of 8-12 in 30 parts of mixed solvent (deionized water and ethanol in a mass ratio of 27:3), add 0.2 parts of alkaline catalyst (potassium hydroxide) at room temperature, stir at 300 r / min, heat to 70 °C for 4 h, cool to room temperature to obtain a low carbon hydration temperature rise inhibitor.

[0040] Example 4

[0041] A low-carbonation temperature rise inhibitor, the preparation method of which includes the following steps:

[0042] (1) Dissolve 10 parts of Kraft lignin in 30 parts of tetrahydrofuran, then add 0.2 parts of alkaline catalyst (sodium hydroxide) at room temperature, then add 1 part of phosphating agent (ammonium dihydrogen phosphate), heat to solvent reflux state, maintain for 8 hours, cool to room temperature, add water to quench excess phosphating agent, remove tetrahydrofuran by rotary evaporation, and dry at 75°C to obtain phosphonylated Kraft lignin;

[0043] (2) Dissolve 10 parts of phosphonylated kraft lignin obtained in step (1) and 10 parts of paraformaldehyde with a degree of polymerization of 8-12 in 30 parts of mixed solvent (deionized water and ethanol in a mass ratio of 27:3), add 0.2 parts of alkaline catalyst (sodium hydroxide) at room temperature, stir at 300 r / min, heat to 60 °C for 4 h, cool to room temperature, and obtain a low-carbon hydration temperature rise inhibitor.

[0044] Example 5

[0045] A low-carbonation temperature rise inhibitor, the preparation method of which includes the following steps:

[0046] (1) Dissolve 10 parts of Kraft lignin in 30 parts of tetrahydrofuran, then add 0.2 parts of alkaline catalyst (sodium hydroxide) at room temperature, then add 1 part of phosphating agent (ammonium dihydrogen phosphate), heat to solvent reflux state, maintain for 8 hours, cool to room temperature, add water to quench excess phosphating agent, remove tetrahydrofuran by rotary evaporation, and dry at 75°C to obtain phosphonylated Kraft lignin;

[0047] (2) Dissolve 10 parts of phosphonylated kraft lignin obtained in step (1) and 15 parts of paraformaldehyde with a degree of polymerization of 8-12 in 30 parts of mixed solvent (deionized water and ethanol in a mass ratio of 27:3), add 0.2 parts of alkaline catalyst (sodium hydroxide) at room temperature, stir at 300 r / min, heat to 60 °C for 4 h, cool to room temperature, and obtain a low-carbon hydration temperature rise inhibitor.

[0048] Example 6

[0049] A low-carbonation temperature rise inhibitor, the preparation method of which includes the following steps:

[0050] (1) Dissolve 10 parts of Kraft lignin in 30 parts of tetrahydrofuran, then add 0.2 parts of alkaline catalyst (sodium hydroxide) at room temperature, then add 1 part of phosphating agent (ammonium dihydrogen phosphate), heat to solvent reflux state, maintain for 8 hours, cool to room temperature, add water to quench excess phosphating agent, remove tetrahydrofuran by rotary evaporation, and dry at 75°C to obtain phosphonylated Kraft lignin;

[0051] (2) Dissolve 10 parts of phosphonylated kraft lignin obtained in step (1) and 5 parts of paraformaldehyde with a degree of polymerization of 10-20 in 30 parts of mixed solvent (deionized water and ethanol in a mass ratio of 27:3), add 0.2 parts of alkaline catalyst (sodium hydroxide) at room temperature, stir at 300 r / min, heat to 60 °C for 4 h, cool to room temperature, and obtain a low-carbon hydration temperature rise inhibitor.

[0052] Example 7

[0053] A low-carbonation temperature rise inhibitor, the preparation method of which includes the following steps:

[0054] (1) Dissolve 10 parts of Kraft lignin in 30 parts of tetrahydrofuran, then add 0.2 parts of alkaline catalyst (sodium hydroxide) at room temperature, then add 1 part of phosphating agent (ammonium dihydrogen phosphate), heat to solvent reflux state, maintain for 8 hours, cool to room temperature, add water to quench excess phosphating agent, remove tetrahydrofuran by rotary evaporation, and dry at 75°C to obtain phosphonylated Kraft lignin;

[0055] (2) Dissolve 10 parts of phosphonylated kraft lignin obtained in step (1) and 5 parts of paraformaldehyde with a degree of polymerization of 20-30 in 30 parts of mixed solvent (deionized water and ethanol in a mass ratio of 27:3), add 0.2 parts of alkaline catalyst (sodium hydroxide) at room temperature, stir at 300 r / min, heat to 60 °C for 4 h, cool to room temperature, and obtain a low-carbon hydration temperature rise inhibitor.

[0056] Comparative Example 1

[0057] Comparative Example 1 was a blank control group, without the addition of low-carbonation temperature rise inhibitors.

[0058] Comparative Example 2

[0059] Commercially available hydration temperature rise inhibitors.

[0060] Comparative Example 3

[0061] A hydration temperature rise inhibitor, the preparation method of which includes the following steps:

[0062] Ten parts of Kraft lignin were dissolved in 30 parts of tetrahydrofuran, and then 0.2 parts of an alkaline catalyst (sodium hydroxide) were added at room temperature. Next, 1 part of a phosphating agent (ammonium dihydrogen phosphate) was added, and the mixture was heated to reflux and maintained for 8 hours. After cooling to room temperature, excess phosphating agent was quenched with water, tetrahydrofuran was removed by rotary evaporation, and the mixture was dried at 75°C to obtain phosphonylated Kraft lignin, which was directly used as an inhibitor of hydration temperature rise.

[0063] Comparative Example 4

[0064] A hydration temperature rise inhibitor, the preparation method of which includes the following steps:

[0065] Ten parts of Kraft lignin and five parts of paraformaldehyde with a degree of polymerization of 8-100 were dissolved in 30 parts of a mixed solvent (deionized water and ethanol in a mass ratio of 27:3). 0.2 parts of an alkaline catalyst (sodium hydroxide) were added at room temperature, and the mixture was stirred at 300 r / min and heated to 60 °C for 4 h. After cooling to room temperature, a hydration temperature rise inhibitor was obtained.

[0066] Experimental Example 1

[0067] According to the test method of JC / T 2608-2021 "Inhibitors of Hydration Temperature Rise in Concrete", the hydration temperature rise inhibitors of Examples 1-7 and Comparative Examples 1-4 were added to mortar and concrete, respectively, and the specific dosages are shown in Table 1. The hydration temperature rise performance of the mortar and the setting time and compressive strength of the concrete were tested. The cement used for the mortar was reference cement PI 42.5, the sand was standard sand, and the water was tap water. The cement used for the concrete test was reference cement PI 42.5, the fine aggregate was river sand with a fineness modulus of 2.5, the coarse aggregate was 5-20mm continuously graded crushed stone, and the water was tap water.

[0068] The test results are shown in Tables 1-2 and 2-2. Figure 1 As shown.

[0069] Table 1. Test results of hydration temperature rise performance of mortars in Examples 1-7 and Comparative Examples 1-4.

[0070]

[0071] Table 2. Test results of hydration temperature rise performance of concrete in Examples 1-7 and Comparative Examples 1-4.

[0072]

[0073]

[0074] As shown in Table 1, the low-carbon hydration temperature rise inhibitor of the present invention can significantly reduce the hydration temperature rise. In each embodiment, at a dosage of 1%, compared to no inhibitor (Comparative Example 1), the temperature rise is reduced by approximately 15°C. Combined with... Figure 1 It is understood that the low-carbon hydration temperature rise inhibitor of the present invention can prolong the hydration induction period of concrete, reduce the hydration temperature rise of concrete, and prolong the deceleration period, thereby making the heat release of concrete more uniform.

[0075] As shown in Table 2, the low-carbon hydration temperature rise inhibitor of the present invention does not significantly delay the setting time of concrete. The 3-day compressive strength of each embodiment is comparable to that of Comparative Example 1, and the 7-day compressive strength is even higher.

[0076] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a low-carbonization temperature rise inhibitor, characterized in that, Includes the following steps: (1) Dissolve Kraft lignin in tetrahydrofuran, then add an alkaline catalyst at room temperature, then add a phosphating agent, heat to the solvent reflux state, maintain for 8 h, cool to room temperature, quench with water, and then successively evaporate and dry to obtain phosphonylated Kraft lignin. (2) Dissolve the phosphonyl lignin and paraformaldehyde obtained in step (1) in a mixed solvent, add an alkaline catalyst at room temperature, stir at 200-500 r / min, heat to 60-70 ℃ for 2-6 h, cool to room temperature to obtain a low carbon hydration temperature rise inhibitor; the degree of polymerization of paraformaldehyde is 8-30; the mixed solvent is composed of deionized water and ethanol in a mass ratio of 27:

3.

2. The preparation method of the low-carbonization temperature rise inhibitor as described in claim 1, characterized in that, In step (1), the mass ratio of Kraft lignin, tetrahydrofuran, alkaline catalyst and phosphating agent is 10:30:0.1-0.3:1-3.

3. The preparation method of the low-carbon hydration temperature rise inhibitor as described in claim 1, characterized in that, In step (1), the phosphating agent is one of the following: ammonium dihydrogen phosphate, phosphoric acid, tetraphosphate, trimethyl phosphite, and triethyl phosphite.

4. The preparation method of the low-carbon hydration temperature rise inhibitor as described in claim 1, characterized in that, In step (1), excess phosphating agent is quenched with water, tetrahydrofuran is removed by rotary evaporation, and the product is dried at 75 °C.

5. The preparation method of the low-carbon hydration temperature rise inhibitor as described in claim 1, characterized in that, In step (2), the mass ratio of phosphonyl lignin, paraformaldehyde, mixed solvent and alkaline catalyst is 10:5-15:30:0.1-0.

3.

6. The preparation method of the low-carbon hydration temperature rise inhibitor as described in claim 1, characterized in that, In steps (1) and (2), the alkaline catalyst is one of sodium hydroxide, potassium hydroxide, calcium hydroxide, triethylamine, and N,N-dimethylacetamide.

7. The low-carbon hydration temperature rise inhibitor prepared by the method of any one of claims 1-6.

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