Preparation method of high-durability concrete anti-freezing additive

Abstract

The invention relates to the technical field of concrete additives, and discloses a preparation method of a high-durability concrete anti-freezing additive, and the preparation method comprises the following steps: placing a polycarboxylic acid water reducer, an early strength agent, an air entraining agent, peanut shell cellulose and an anti-freezing agent microcapsule in water, and fully stirring to obtain the anti-freezing additive; the anti-freezing additive comprises the following raw materials: a polycarboxylate superplasticizer, an early strength agent, an air entraining agent, peanut shell cellulose, an anti-freezing agent microcapsule and water, peanut shell cellulose and anti-freezing agent microcapsules are prepared to participate in the preparation process of the concrete anti-freezing additive, so that the prepared concrete anti-freezing additive can protect concrete in a low-temperature environment, the hydration effect of the concrete is improved, cracks generated due to incomplete hydration are reduced, and the strength of the concrete is effectively enhanced; the durability of the concrete is improved, so that the service life of the concrete is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete additives, and particularly relates to a preparation method of a high-durability concrete anti-freezing additive. Background Art

[0002] Concrete is a building material widely used in engineering construction, with excellent construction performance and compressive capacity, and plays a crucial role in the construction of large-scale infrastructure such as houses, roads, and bridges. However, in extreme weather and low-temperature environments, the hydration reaction of concrete is hindered, directly affecting the early strength of concrete, and the construction and maintenance of concrete face great challenges. How to improve the frost resistance of concrete in low-temperature environments has become an urgent problem to be solved.

[0003] Generally speaking, there are mainly two ways to prevent concrete from freezing. One is to add anti-freezing agents, and the other is to adopt measures such as heating or steam curing. In comparison, directly adding anti-freezing agents is simple to operate, does not rely on mechanical equipment, and has a wider range of use. However, currently, ordinary concrete anti-freezing agents generally have general anti-freezing performance when in use, and the effective time is short, and they cannot continuously promote the hydration process of concrete at low temperatures, resulting in a slow setting and hardening rate of concrete in low-temperature environments, low early strength, and affecting the durability of concrete.

[0004] The patent with the publication number CN105906229B discloses a preparation method of a multi-component composite low-dose concrete anti-freezing agent, which forms a synergistic effect through the combination of physical or chemical actions, and acts together from several aspects such as water reduction, air entrainment, freezing point reduction, and corrosion prevention in the concrete anti-freezing mechanism, improving the application performance of concrete. At the same time, through the adjustment and substitution of components, the dosage of the anti-freezing agent is reduced, meeting the requirements of green environmental protection. However, when this patent is actually used, the anti-freezing agent has no slow-release effect, and in a long-term low-temperature environment, it cannot continuously and effectively protect concrete from low-temperature damage, which may affect the durability of concrete. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method of a high-durability concrete anti-freezing additive, which solves the problems that ordinary concrete additives generally have general anti-freezing performance, short effective time, slow setting and hardening rate of concrete at low temperatures, resulting in a reduction in concrete strength and affecting the durability of concrete.

[0006] The purpose of the present invention can be achieved through the following technical solutions: A preparation method of a high-durability concrete anti-freezing additive, characterized by comprising the following steps: Put polycarboxylate superplasticizer, early strength agent, air-entraining agent, peanut shell cellulose, and antifreeze agent microcapsules into water, and stir at a speed of 80 - 90 r / min for 10 - 12 min to obtain an antifreeze additive.

[0007] In this solution, through the compound compatibility of polycarboxylate superplasticizer, early strength agent, air-entraining agent, peanut shell cellulose, and antifreeze microcapsules, while ensuring the fluidity of concrete, the early hydration efficiency of concrete in low-temperature environments is significantly improved. The molecular structure of polycarboxylate superplasticizer can be adsorbed on the surface of cement particles in an oriented manner to form a three-dimensional electrostatic repulsion force, effectively reducing the freezing point. The early strength agent shortens the setting time by catalyzing the hydration reaction and forms a buffer layer with the uniform microbubbles generated by the air-entraining agent. Peanut shell cellulose can generate stress pulling in concrete and provide a positioning anchor point for the antifreeze agent microcapsules. It can not only effectively reduce cracks but also promote the uniform dispersion of the antifreeze agent microcapsules during use, enabling them to exert excellent antifreeze effects. In this solution, the components of the prepared antifreeze additive produce a synergistic effect, effectively protecting concrete in low-temperature environments, promoting the hydration efficiency of concrete, enhancing the strength of concrete, and giving it a longer service life.

[0008] Furthermore, the high-durability concrete antifreeze additive comprises the following raw materials in parts by weight: 8 - 10 parts of polycarboxylate superplasticizer, 3 - 5 parts of early strength agent, 1 - 3 parts of air-entraining agent, 20 - 25 parts of peanut shell cellulose, 6 - 8 parts of antifreeze agent microcapsules, and 100 - 150 parts of water.

[0009] Furthermore, the polycarboxylate superplasticizer is any one of allyl polyoxyethylene ether and sodium methylallylsulfonate; the early strength agent is any one of triethanolamine and sodium sulfate; the air-entraining agent is any one of sodium dodecylbenzenesulfonate and sodium dodecyl sulfate.

[0010] Furthermore, the preparation of the peanut shell cellulose comprises the following steps: S1: Clean the peanut shells, place them in an oven at 80 - 85 °C for 20 - 25 min, take them out, crush, grind, and pass through a 100 - 150 mesh sieve to obtain peanut shell powder; S2: Place the peanut shell powder in a sodium hydroxide solution, heat it to 50 - 55 °C and stir for 1.5 - 2 h, add acetic acid to adjust the pH of the suspension to neutral, filter, wash, and dry to obtain the peanut shell cellulose precursor; S3: Place the peanut shell cellulose precursor in deionized water, ultrasonically disperse for 10 - 15 min, heat it to 70 - 75 °C, add acetic acid solution and sodium hypochlorite solution, stir for 1 - 1.5 h, then centrifuge to separate, collect the solid product, and obtain peanut shell cellulose after washing and drying.

[0011] In this scheme, peanut shells are washed and ground to obtain peanut shell powder, and then the peanut shell powder is subjected to alkali treatment and acid neutralization, which is beneficial to removing lignin in the peanut shells. After post-treatment, a peanut shell cellulose precursor is obtained, and then under the action of acetic acid solution and sodium hypochlorite solution, hemicellulose and impurities are removed, and peanut shell cellulose is obtained after the products are collected. When the peanut shell cellulose prepared by this process acts on concrete, it can effectively bridge micro cracks in the concrete, form a three-dimensional network structure, form stress pulling, and improve the compressive strength of the concrete material. In addition, the preparation of cellulose by peanut shells can realize the reuse of agricultural waste and reduce the pressure of agricultural waste treatment.

[0012] Furthermore, in step S2, the mass fraction of the sodium hydroxide solution is 10-12%.

[0013] Furthermore, in step S3, the mass fraction of the acetic acid solution is 3-5%, and the mass fraction of the sodium hypochlorite solution is 5-6%.

[0014] Furthermore, the preparation of the antifreeze agent microcapsules comprises the following steps: SS1: Place sodium chloride, calcium chloride and sodium nitrite in deionized water and stir thoroughly at a speed of 200-250r / min for 5-8min to form a mixed solution; SS2: Place dextran and 2,3-epoxypropyltrimethylammonium chloride in deionized water, add a catalyst, heat to 75-80°C and stir for 3-5 hours, remove the solvent by rotary evaporation and collect the product to obtain modified dextran; SS3: Add modified dextran to the mixed solution, stir at a speed of 300-350 r / min for 1-1.5 h to allow it to swell fully, use a freeze dryer to vacuum freeze-dry the mixed solution, grind it and sieve it to obtain antifreeze agent microcapsules.

[0015] In this solution, sodium chloride, calcium chloride, and sodium nitrite are compounded to form a mixed solution. Then, under the action of a catalyst, the hydroxyl groups in the dextran structure undergo a ring-opening reaction with the epoxy groups in the 2,3-epoxypropyltrimethylammonium chloride structure to obtain modified dextran. The modified dextran is added to the mixed solution, and after vacuum freeze-drying, antifreeze microcapsules are obtained. The core material of this kind of antifreeze microcapsule is a mixed solution of sodium chloride, calcium chloride, and sodium nitrite. Sodium chloride and calcium chloride can significantly lower the freezing point of water and can effectively prevent water from freezing at low temperatures in concrete, avoiding the occurrence of microcracks inside the concrete due to freezing expansion force, significantly enhancing the frost resistance of the concrete, and enhancing the durability of the concrete. At the same time, the addition of sodium nitrite can not only further enhance the antifreeze ability of the concrete but also effectively reduce the possibility of steel bar corrosion in the concrete, improving the durability of the concrete. Using modified dextran as the shell layer of the antifreeze agent microcapsule can protect the antifreeze agent composite solution, facilitating its storage and transportation. At the same time, it can be slowly released during use, prolonging the action time and avoiding premature consumption. Moreover, the surface of this kind of modified dextran contains multiple quaternary ammonium groups, which can have an adsorption effect with peanut shell cellulose, helping to enhance the interfacial bonding force between the microcapsule and the material matrix, promoting the dispersion of the microcapsule in the concrete. Combining with the slow-release effect of the microcapsule, it can effectively improve the stability and durability of the antifreeze effect of this kind of antifreeze agent microcapsule in the concrete, improve the hydration effect of the concrete, and significantly enhance the strength of the concrete.

[0016] Further, in step SS1, the mass ratio of sodium chloride, calcium chloride, and sodium nitrite is 1 - 3:1.2 - 1.8:0.5 - 0.7.

[0017] Further, in step SS2, the catalyst is boron trifluoride diethyl ether.

[0018] Further, in step SS3, the temperature of the vacuum freeze-drying is -40 to -50 °C, and the time is 24 - 48 h.

[0019] Further, in step SS3, the sieving after grinding is sieving through a 100 - 200 mesh sieve after grinding.

[0020] The beneficial effects of the present invention: In the present invention, cellulose from peanut shells and antifreeze microcapsules are prepared and involved in the preparation process of a concrete antifreeze additive, enabling the prepared concrete antifreeze additive to protect the concrete in a low-temperature environment, enhancing the hydration effect of the concrete, reducing cracks caused by incomplete hydration, effectively enhancing the strength of the concrete. At the same time, the microcapsule slow-release technology is adopted to place the effective components of the antifreeze agent in the microcapsules. When used in concrete, the microcapsules are squeezed and broken, slowly releasing the antifreeze agent, prolonging the action time of the antifreeze agent. In a long-term low-temperature environment, it can effectively provide continuous and excellent antifreeze effect for the concrete, further enhancing the strength of the concrete and improving the durability of the concrete, thereby prolonging the service life of the concrete.

[0021] Of course, not necessarily all the advantages described above need to be achieved simultaneously for any product implementing the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for describing the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0023] Figure 1 It is a flowchart for the preparation of the antifreeze additive of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, rather than all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0025] The preparation methods of cellulose from peanut shells and antifreeze microcapsules in the following embodiments and comparative examples of the present invention are as follows: I. Preparation of Cellulose from Peanut Shells S1: Clean 30 g of peanut shells, place them in an oven at 80 °C for 20 min, take them out, crush, grind and pass through a 100-mesh sieve to obtain peanut shell powder; S2: Place the peanut shell powder in 60 ml of a sodium hydroxide solution with a mass fraction of 10%, heat to 50 °C and stir for 1.5 h, add acetic acid to adjust the pH of the suspension to neutral, filter, wash and dry to obtain the precursor of cellulose from peanut shells; S3: Place the peanut shell cellulose precursor in 80 ml of deionized water, ultrasonically disperse it for 10 min, heat it up to 70 °C, add 6 ml of acetic acid solution with a mass fraction of 3% and 10 ml of sodium hypochlorite solution with a mass fraction of 5%, stir for 1 h and then centrifuge to separate, collect the solid product, and obtain peanut shell cellulose after washing and drying.

[0026] II. Preparation of antifreeze microcapsules SS1: Place 2 g of sodium chloride, 1.5 g of calcium chloride, and 0.6 g of sodium nitrite in 80 ml of deionized water, and stir well at a rotation speed of 200 r / min for 5 min to form a mixed solution; SS2: Place 5 g of dextran and 5.8 g of 2,3-epoxypropyltrimethylammonium chloride in 65 ml of deionized water, add 0.5 g of boron trifluoride diethyl ether, heat it up to 75 °C and stir well for 3 h, rotate and evaporate to remove the solvent, and collect the product to obtain modified dextran; SS3: Add 5.5 g of modified dextran to the mixed solution, stir at a rotation speed of 300 r / min for 1 h to make it fully swell, use a freeze dryer to vacuum freeze-dry the mixed solution at -40 °C for 24 h, and pass through a 100-mesh sieve after grinding to obtain antifreeze microcapsules. Example 1

[0027] Preparation of antifreeze additive Place 8 parts of allyl polyoxyethylene ether, 3 parts of sodium sulfate, 1 part of sodium dodecylbenzenesulfonate, 20 parts of peanut shell cellulose, and 6 parts of antifreeze microcapsules in 100 parts of water, and stir at a rotation speed of 80 r / min for 10 min to obtain an antifreeze additive. Example 2

[0028] Preparation of antifreeze additive Place 9 parts of sodium methallylsulfonate, 4 parts of triethanolamine, 2 parts of sodium dodecyl sulfate, 22 parts of peanut shell cellulose, and 7 parts of antifreeze microcapsules in 125 parts of water, and stir at a rotation speed of 85 r / min for 11 min to obtain an antifreeze additive. Example 3

[0029] Preparation of antifreeze additive Place 10 parts of allyl polyoxyethylene ether, 5 parts of sodium sulfate, 3 parts of sodium dodecylbenzene sulfonate, 25 parts of peanut shell cellulose, and 8 parts of sodium chloride, calcium chloride, and sodium nitrite with a mass ratio of 2:1.5:0.6 in 150 parts of water, and stir at a rotation speed of 90 r / min for 12 min to obtain an antifreeze additive.

[0030] Comparative Example 1 Preparation of antifreeze additive 9 parts of sodium methallylsulfonate, 4 parts of triethanolamine, 2 parts of sodium dodecyl sulfate, and 7 parts of antifreeze microcapsules were placed in 125 parts of water and stirred at 85 r / min for 11 min to obtain an antifreeze additive.

[0031] Comparative Example 2 Preparation of Antifreeze Additive 9 parts of sodium methallylsulfonate, 4 parts of triethanolamine, 2 parts of sodium dodecyl sulfate, and 22 parts of peanut shell cellulose were placed in 125 parts of water and stirred at 85 r / min for 11 min to obtain an antifreeze additive.

[0032] Comparative Example 3 Preparation of Antifreeze Additive 9 parts of sodium methallylsulfonate, 4 parts of triethanolamine, 2 parts of sodium dodecyl sulfate, and 22 parts of peanut shell cellulose were placed in 125 parts of water and stirred at 85 r / min for 11 min to obtain an antifreeze additive.

[0033] Performance Testing 200 kg of ordinary Portland cement, 1000 kg of crushed stone, 350 kg of river sand, 50 kg of fly ash, and 70 kg of mineral powder were mixed and stirred evenly, divided into 6 portions, and 2 kg of the antifreeze additives prepared in Example 1 - Example 3 and Comparative Example 1 - Comparative Example 3 were added respectively. After thorough mixing and stirring, they were placed in a mold and demolded after 48 h at room temperature to obtain block-shaped concrete. It was cured for 7 days under the conditions of -5°C, -10°C, and -15°C as samples; the mechanical properties of the frozen samples were tested with reference to the standard GB / T50081 - 2019; the freezing conditions of the samples were observed at -15°C after 7 days and 15 days of curing to judge the antifreeze aging effect of the samples; the specific test results are shown in the following table:

[0034] As can be seen from the above table, the samples prepared in Example 1 - Example 3 all have good low-temperature resistance. In the sample prepared in Comparative Example 1, the added antifreeze additive did not contain peanut shell cellulose and did not form a network structure in the concrete, so the compressive strength in Comparative Example 1 is inferior to that in the examples. In the sample prepared in Comparative Example 2, the added antifreeze additive did not contain antifreeze microcapsules, so the sample prepared in Comparative Example 2 has poor antifreeze ability and shows freezing in a low-temperature environment. In the sample prepared in Comparative Example 3, the antifreeze component was directly added to the added antifreeze additive without microencapsulation treatment. The antifreeze effect of this sample is good, but the antifreeze aging effect is short, and it is difficult to protect the concrete in a low-temperature environment for a long time.

[0035] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0036] The above content is only an example and illustration of the concept of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific embodiments or use similar methods for substitution, as long as they do not deviate from the scope defined by the concept of the invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a highly durable concrete antifreeze additive, characterized in that: The following steps are involved: The polycarboxylate water reducer, early strength agent, air entraining agent, peanut shell cellulose and antifreeze agent microcapsules are placed in water, and stirred at a speed of 80-90 r / min for 10-12 minutes to obtain an antifreeze additive.

2. The method for preparing a highly durable concrete antifreeze additive according to claim 1, characterized in that: The highly durable concrete antifreeze additive comprises the following raw materials in parts by weight: 8-10 parts of polycarboxylic acid water reducer, 3-5 parts of early strength agent, 1-3 parts of air entraining agent, 20-25 parts of peanut shell cellulose, 6-8 parts of antifreeze agent microcapsules, and 100-150 parts of water.

3. The method for preparing a highly durable concrete antifreeze additive according to claim 1, characterized in that: The polycarboxylate water reducer is any one of propylene polyoxyethylene ether and sodium methacrylate sulfonate; the early strength agent is any one of triethanolamine and sodium sulfate; the air entraining agent is any one of sodium dodecylbenzene sulfonate and sodium dodecyl sulfate.

4. The method for preparing a highly durable concrete antifreeze additive according to claim 1, characterized in that: The preparation of peanut shell cellulose comprises the following steps: S1: Clean the peanut shells, place them in an oven at 80-85°C for 20-25 minutes, take them out, crush them, and grind them through a 100-150 mesh sieve to obtain peanut shell powder; S2: placing peanut shell powder in a sodium hydroxide solution, heating to 50-55° C. and stirring for 1.5-2 hours, adding acetic acid to adjust the pH of the suspension to neutral, filtering, washing, and drying to obtain a peanut shell cellulose precursor; S3: placing the peanut shell cellulose precursor in deionized water, ultrasonically dispersing for 10-15 minutes, heating to 70-75°C, adding acetic acid solution and sodium hypochlorite solution, stirring for 1-1.5 hours and then centrifuging to collect the solid product, washing and drying to obtain peanut shell cellulose.

5. The method for preparing a highly durable concrete antifreeze additive according to claim 4, characterized in that: In step S2, the mass fraction of the sodium hydroxide solution is 10-12%.

6. The method for preparing a highly durable concrete antifreeze additive according to claim 4, characterized in that: In step S3, the mass fraction of the acetic acid solution is 3-5%, and the mass fraction of the sodium hypochlorite solution is 5-6%.

7. The method for preparing a highly durable concrete antifreeze additive according to claim 1, characterized in that: The preparation of the antifreeze agent microcapsules comprises the following steps: SS1: Place sodium chloride, calcium chloride and sodium nitrite in deionized water and stir thoroughly at a speed of 200-250r / min for 5-8min to form a mixed solution; SS2: Place dextran and 2,3-epoxypropyltrimethylammonium chloride in deionized water, add a catalyst, heat to 75-80°C and stir for 3-5 hours, remove the solvent by rotary evaporation and collect the product to obtain modified dextran; SS3: Add modified dextran to the mixed solution, stir at a speed of 300-350 r / min for 1-1.5 h to allow it to swell fully, use a freeze dryer to vacuum freeze-dry the mixed solution, grind it and sieve it to obtain antifreeze agent microcapsules.

8. The method for preparing a highly durable concrete antifreeze additive according to claim 7, characterized in that: In step SS2, the catalyst is boron trifluoride etherate.

9. The method for preparing a highly durable concrete antifreeze additive according to claim 7, characterized in that: In step SS3, the vacuum freeze drying is carried out at a temperature of -40 to -50°C for 24 to 48 hours.

10. The method for preparing a highly durable concrete antifreeze additive according to claim 7, characterized in that: In step SS3, the sieving after grinding is to pass through a 100-200 mesh sieve after grinding.

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