Preparation method of low-carbon hydration temperature rise inhibitor

Abstract

The invention discloses a preparation method of a low-carbon hydration temperature rise 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, adding water for quenching, and then sequentially carrying out rotary evaporation and drying to obtain phosphorylated kraft lignin; and (2) dissolving the phosphorylated 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, reacting for 2-6 hours, and cooling to room temperature to obtain the low-carbon hydration temperature rise inhibitor. The invention also comprises the low-carbon hydration temperature rise inhibitor prepared by the method. The inhibitor provided by the invention has a good hydration temperature rise effect, can reduce the cracking risk of concrete caused by temperature drop shrinkage, and avoids cracking.

Description

Technical Field

[0001] The invention relates to the technical field of concrete admixtures, and in particular to a method for preparing a low-carbon hydration temperature rise inhibitor. Background Art

[0002] The hydration reaction of cement is an exothermic reaction. This heat release, coupled with the low thermal conductivity of concrete, means that there may be huge temperature differences in large-volume concrete, causing a large difference in its setting time at different temperatures, resulting in crystallization defects and cracking risks, which in turn affect the durability of concrete. In the process of social development, large-volume concrete is widely used in many fields due to its advantages, and cement hydration can easily cause temperature cracks. Therefore, the development of cement hydration temperature rise inhibitors has become a key focus of concrete admixtures in recent years, which is of great significance to ensuring the quality of concrete construction and structural safety.

[0003] There are many shortcomings of the hydration temperature rise inhibitors currently on the market. In the application scenario of large-volume concrete, taking the construction of large bridge pier foundations as an example, even if inhibitors are used, the internal temperature will still rise to a certain extent. Only the heating rate is reduced, which cannot fundamentally eliminate the temperature rise problem. When in a high-temperature environment, such as construction during high-temperature periods in summer, the performance of the inhibitor will be significantly limited, and it is difficult to effectively control the magnitude of the hydration temperature rise. From the perspective of the impact on concrete performance, it may delay the formation of early concrete strength, which is undoubtedly an obstacle to meeting the requirements for construction tasks that have urgent strength requirements such as rapid demoulding of prefabricated components. More importantly, some inhibitors may introduce certain components that pose a potential threat to durability into concrete, resulting in a decrease in the impermeability and frost resistance of concrete, thereby affecting the long-term stability and service life of concrete structures. In addition, with the growth of population and the increase in demand for energy and chemical materials, the demand for chemical polymers has increased sharply. Human beings are facing the dual pressures of resource shortages and environmental pollution, so green and low-carbon development is crucial.

[0004] Therefore, there is an urgent need in the art to develop a concrete hydration heat inhibitor that is simple to prepare, green and low-carbon, and has excellent performance. It can achieve the purpose of anti-cracking by inhibiting the hydration temperature rise effect and reducing the risk of cracking caused by temperature drop shrinkage of concrete. Summary of the invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a method for preparing a low-carbon hydration temperature rise inhibitor, which has a good hydration temperature rise effect, can reduce the risk of cracking of concrete caused by temperature drop shrinkage, and avoid cracking.

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

[0007] (1) dissolving kraft lignin in tetrahydrofuran, then adding a base catalyst at room temperature, then adding a phosphating agent, heating to the solvent reflux state, maintaining for 8 hours, cooling to room temperature, adding water to quench, and then sequentially subjecting to rotary evaporation and drying to obtain phosphonylated kraft lignin;

[0008] The reaction process is:

[0009]

[0010] (2) dissolving the phosphonylated kraft lignin and polyformaldehyde obtained in step (1) in a mixed solvent, adding an alkali catalyst at room temperature, stirring at 200-500 r / min, heating to 60-70° C. for reaction for 2-6 hours, and cooling to room temperature to obtain a low-carbon hydration temperature rise inhibitor.

[0011] The reaction process is:

[0012]

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

[0014] Furthermore, in step (1), the phosphating agent is one of diammonium phosphate, phosphoric acid, tetraphosphoric acid, trimethyl phosphite and triethyl phosphite.

[0015] Furthermore, in step (1), water is added to quench the excess phosphating agent, tetrahydrofuran is removed by rotary evaporation, and the mixture is dried at 75°C.

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

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

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

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

[0020] The present invention also provides a low-carbohydrate temperature rise inhibitor prepared by the preparation method of the low-carbohydrate temperature rise inhibitor.

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

[0022] 1. Kraft lignin is a three-dimensional network polymer composed of phenylpropane units connected by ether bonds and carbon-carbon bonds. It has air entraining properties and can introduce tiny and evenly distributed bubbles into concrete, improving the concrete's impermeability and freeze-thaw resistance, thereby enhancing the durability of concrete and extending the service life of concrete structures. In addition, Kraft lignin contains a variety of active functional groups, among which functional groups such as phenolic hydroxyl groups can give it a certain antioxidant capacity. And Kraft lignin has a certain surface activity, which can improve the workability of concrete.

[0023] 2. After phosphonylation, lignin can slow down the cement hydration reaction rate and reduce the hydration heat release rate. The main principles are as follows: (1) Formation of a protective film: Phosphonyl compounds can form a protective film on the surface of cement particles, preventing cement particles from fully contacting with 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, thereby achieving the effect of reducing 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 cement hydration. Phosphonyl groups may adsorb on the surface of crystal nuclei, preventing the further growth and development of crystal nuclei, making the cement hydration reaction unable to proceed rapidly, thereby reducing the generation of hydration heat.

[0024] 3. After the polycondensation reaction of lignin and aldehydes, the inhibitory effect on cement hydration is enhanced. The principle is as follows: (1) Formation of steric hindrance: After the polycondensation 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, thereby delaying the cement hydration process; (2) Consumption of hydroxyl groups: The polycondensation reaction consumes some hydroxyl groups in lignin, and hydroxyl groups can react with calcium ions in cement to promote hydration. After the number of hydroxyl groups decreases, the charge distribution on the surface of cement particles changes, and the electrostatic repulsion between particles increases. (1) Adding water to the cement particles disperses them and makes them less likely to agglomerate to form hydration products, thus inhibiting cement hydration; (2) 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 contact with water, and 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, thus hindering the migration and diffusion of water inside the cement, reducing the chance of cement contact with 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, their molecular chains can form complexes with ions in cement hydration products, delaying the formation and growth of cement crystal nuclei, thus inhibiting cement hydration.

[0025] 4. Lignin is a natural high molecular polymer with a wide range of sources. It can be extracted from paper industry waste, etc. It can achieve effective resource recycling, reduce waste emissions, and comply with environmental protection concepts. In addition, the raw material cost of lignin-based admixtures is relatively low. Its main raw material, Kraft lignin, is a by-product of the papermaking and pulping process. It is abundant in sources and relatively cheap. Secondly, lignin-based admixtures are non-toxic and harmless, and are non-flammable and non-explosive hazardous goods. They are highly safe during storage, transportation, and use, and will not cause harm to humans and the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The hydration temperature rise performance test results of the mortars of Examples 1-7 and Comparative Examples 1-4 are shown. DETAILED DESCRIPTION

[0027] The principles and features of the present invention are described below, and the examples are only used to explain the present invention and are not used to limit the scope of the present invention. If no specific conditions are specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0028] Example 1

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

[0030] (1) 10 parts of kraft lignin are dissolved in 30 parts of tetrahydrofuran, and then 0.2 parts of a base catalyst (sodium hydroxide) are added at room temperature, followed by 1 part of a phosphating agent (ammonium dihydrogen phosphate), and the mixture is heated to the solvent reflux state, maintained for 8 hours, cooled to room temperature, and water is added to quench the excess phosphating agent, and tetrahydrofuran is removed by rotary evaporation, and dried at 75° C. to obtain phosphonylated kraft lignin;

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

[0032] Example 2

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

[0034] (1) 10 parts of kraft lignin are dissolved in 30 parts of tetrahydrofuran, and then 0.2 parts of a base catalyst (sodium hydroxide) are added at room temperature, followed by 2 parts of a phosphating agent (trimethyl phosphite), and the mixture is heated to a solvent reflux state, maintained for 8 hours, cooled to room temperature, and water is added to quench the excess phosphating agent, and tetrahydrofuran is removed by rotary evaporation, and dried at 75° C. to obtain phosphonylated kraft lignin;

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

[0036] Example 3

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

[0038] (1) 10 parts of kraft lignin are dissolved in 30 parts of tetrahydrofuran, and then 0.2 parts of a base catalyst (potassium hydroxide) is added at room temperature, followed by 3 parts of a phosphating agent (trimethyl phosphite), and the mixture is heated to a solvent reflux state, maintained for 8 hours, cooled to room temperature, and water is added to quench the excess phosphating agent, and tetrahydrofuran is removed by rotary evaporation, and dried at 75° C. to obtain phosphonylated kraft lignin;

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

[0040] Example 4

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

[0042] (1) 10 parts of kraft lignin are dissolved in 30 parts of tetrahydrofuran, and then 0.2 parts of a base catalyst (sodium hydroxide) are added at room temperature, followed by 1 part of a phosphating agent (ammonium dihydrogen phosphate), and the mixture is heated to the solvent reflux state, maintained for 8 hours, cooled to room temperature, and water is added to quench the excess phosphating agent, and tetrahydrofuran is removed by rotary evaporation, and dried at 75° C. to obtain phosphonylated kraft lignin;

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

[0044] Example 5

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

[0046] (1) 10 parts of kraft lignin are dissolved in 30 parts of tetrahydrofuran, and then 0.2 parts of a base catalyst (sodium hydroxide) are added at room temperature, followed by 1 part of a phosphating agent (ammonium dihydrogen phosphate), and the mixture is heated to the solvent reflux state, maintained for 8 hours, cooled to room temperature, and water is added to quench the excess phosphating agent, and tetrahydrofuran is removed by rotary evaporation, and dried at 75° C. to obtain phosphonylated kraft lignin;

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

[0048] Example 6

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

[0050] (1) 10 parts of kraft lignin are dissolved in 30 parts of tetrahydrofuran, and then 0.2 parts of a base catalyst (sodium hydroxide) are added at room temperature, followed by 1 part of a phosphating agent (ammonium dihydrogen phosphate), and the mixture is heated to the solvent reflux state, maintained for 8 hours, cooled to room temperature, and water is added to quench the excess phosphating agent, and tetrahydrofuran is removed by rotary evaporation, and dried at 75° C. to obtain phosphonylated kraft lignin;

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

[0052] Example 7

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

[0054] (1) 10 parts of kraft lignin are dissolved in 30 parts of tetrahydrofuran, and then 0.2 parts of a base catalyst (sodium hydroxide) are added at room temperature, followed by 1 part of a phosphating agent (ammonium dihydrogen phosphate), and the mixture is heated to the solvent reflux state, maintained for 8 hours, cooled to room temperature, and water is added to quench the excess phosphating agent, and tetrahydrofuran is removed by rotary evaporation, and dried at 75° C. to obtain phosphonylated kraft lignin;

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

[0056] Comparative Example 1

[0057] Comparative Example 1 is a blank control group, without adding low-carb temperature rise inhibitor.

[0058] Comparative Example 2

[0059] Commercially available hydration temperature rise inhibitor.

[0060] Comparative Example 3

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

[0062] Dissolve 10 parts of kraft lignin in 30 parts of tetrahydrofuran, then add 0.2 parts of base catalyst (sodium hydroxide) at room temperature, then add 1 part of phosphating agent (monoammonium phosphate), heat to the solvent reflux state, maintain for 8 hours, cool to room temperature, add water to quench the excess phosphating agent, remove tetrahydrofuran by rotary evaporation, and dry at 75°C to obtain phosphonylated kraft lignin; directly use it as a hydration temperature rise inhibitor.

[0063] Comparative Example 4

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

[0065] Dissolve 10 parts of kraft lignin and 5 parts of polyformaldehyde with a polymerization degree of 8-100 in 30 parts of a mixed solvent (deionized water and ethanol mass ratio of 27:3), add 0.2 parts of an alkali catalyst (sodium hydroxide) at room temperature, stir at 300 r / min, heat to 60°C for 4 hours, and cool to room temperature to obtain a hydration temperature rise inhibitor.

[0066] Test Example 1

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

[0068] The above test results are shown in Table 1-2 and Figure 1 shown.

[0069] Table 1 Hydration temperature rise performance test results of mortars of Examples 1-7 and Comparative Examples 1-4

[0070]

[0071] Table 2 Test results of hydration temperature rise performance of concrete of 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. The temperature rise of each example can be reduced by about 15°C compared with the example without the inhibitor (Comparative Example 1) at a dosage of 1%. Figure 1 It can be seen 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] It can be seen from Table 2 that the low-carbon hydration temperature rise inhibitor of the present invention cannot significantly delay the setting time of concrete. The 3-day compressive strength of each embodiment is equivalent to that of Comparative Example 1, and the 7-day compressive strength is 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 principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a low-carbohydrate temperature rise inhibitor, characterized in that: The following steps are involved: (1) dissolving kraft lignin in tetrahydrofuran, then adding a base catalyst at room temperature, then adding a phosphating agent, heating to the solvent reflux state, maintaining for 8 hours, cooling to room temperature, adding water to quench, and then sequentially subjecting to rotary evaporation and drying to obtain phosphonylated kraft lignin; (2) dissolving the phosphonylated kraft lignin and polyformaldehyde obtained in step (1) in a mixed solvent, adding an alkali catalyst at room temperature, stirring at 200-500 r / min, heating to 60-70° C. for reaction for 2-6 hours, and cooling to room temperature to obtain a low-carbon hydration temperature rise inhibitor.

2. The method for preparing the low-carbohydrate temperature rise inhibitor according to claim 1, characterized in that: In step (1), the mass ratio of kraft lignin, tetrahydrofuran, alkali catalyst and phosphating agent is 10:30:0.1-0.3:1-3.

3. The method for preparing the low-carbohydrate temperature rise inhibitor according to claim 1, characterized in that: In step (1), the phosphating agent is one of diammonium phosphate, phosphoric acid, tetraphosphoric acid, trimethyl phosphite and triethyl phosphite.

4. The method for preparing the low-carbohydrate temperature rise inhibitor according to claim 1, characterized in that: In step (1), water is added to quench the excess phosphating agent, tetrahydrofuran is removed by rotary evaporation, and the mixture is dried at 75°C.

5. The method for preparing the low-carbohydrate temperature rise inhibitor according to claim 1, characterized in that: In step (2), the mass ratio of phosphonylated kraft lignin, paraformaldehyde, mixed solvent and alkali catalyst is 10:5-15:30:0.1-0.

3.

6. The method for preparing the low-carbohydrate temperature rise inhibitor according to claim 1, characterized in that: In step (2), the degree of polymerization of the paraformaldehyde is 8-30.

7. The method for preparing the low-carbohydrate temperature rise inhibitor according to claim 1, characterized in that: In step (2), the mixed solvent is prepared by mixing deionized water and ethanol in a mass ratio of 27:

3.

8. The method for preparing the low-carbohydrate temperature rise inhibitor according to claim 1, characterized in that: In step (1) and step (2), the base catalyst is one of sodium hydroxide, potassium hydroxide, calcium hydroxide, triethylamine and N,N-dimethylacetamide.

9. The low-carbohydrate temperature rise inhibitor prepared by the method for preparing the low-carbohydrate temperature rise inhibitor according to any one of claims 1 to 8.

Images