CN112125569B - Response type concrete antifreeze agent and preparation method and application thereof - Google Patents
Response type concrete antifreeze agent and preparation method and application thereof Download PDFInfo
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- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
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- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
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Abstract
The invention relates to a response type concrete antifreeze agent and a preparation method and application thereof, wherein the preparation method of the antifreeze agent comprises the following steps: 1) adding NaOH and urea into water to obtain a NaOH/urea solution; 2) adding hydroxyethyl cellulose and carboxylated chitosan into a NaOH/urea solution to obtain a cellulose/chitosan solution; adding polyvinyl alcohol and chitin into a NaOH/urea solution to obtain a polyvinyl alcohol/chitin solution; 3) uniformly mixing the cellulose/chitosan solution and the polyvinyl alcohol/chitin solution and removing bubbles to obtain the response type concrete antifreeze agent; when the response type concrete antifreeze agent is applied, the response type concrete antifreeze agent is added into the concrete mixture, and the mixing amount of the response type concrete antifreeze agent is 2-10% of the mass of the cementing material. Compared with the prior art, the invention can effectively reduce the freeze-thaw damage of the concrete and improve the service life of the concrete material under the condition of temperature alternation.
Description
Technical Field
The invention belongs to the technical field of building materials, and relates to a response type concrete antifreeze agent, and a preparation method and application thereof.
Background
The concrete freeze-thaw damage refers to that the integrity of the service performance and the appearance of the concrete material is damaged under the action of freeze-thaw cycles. The frost resistance of the concrete is one of important indexes of the durability of the concrete, the internal structure of the concrete is damaged under the action of low-temperature freeze-thaw cycle, the durability is reduced, the quality of the whole project is greatly influenced, and the service life and the service performance of the project are obviously reduced.
The concrete freezing and thawing damage process is a complex physical change process, most researches at present think that the frost resistance of the concrete is related to water in pores and microcracks inside the concrete, when the environmental temperature is lower, water freezes at low temperature, the volume expands, supercooled water can migrate, and the existence of larger internal stress causes the gradual expansion and enlargement of the pores and the microcracks inside the concrete and even the mutual communication, thereby causing the reduction of the strength and further causing the damage of the concrete structure.
The measures commonly used at present for improving the frost resistance of concrete are as follows: using air entraining agent, compacting by vibration, optimizing the mixing proportion, and the like. The use limiting factors of the measures are more, the construction is complex, the mechanical property is negatively influenced, and the application is greatly limited.
Disclosure of Invention
The invention aims to provide a response type concrete antifreeze agent, and a preparation method and application thereof, which can effectively reduce the freeze-thaw damage of concrete and prolong the service life of a concrete material under the condition of temperature alternation.
The purpose of the invention can be realized by the following technical scheme:
a preparation method of a response type concrete antifreeze agent comprises the following steps:
1) adding NaOH and urea into water to obtain a NaOH/urea solution;
2) adding hydroxyethyl cellulose and carboxylated chitosan into a NaOH/urea solution to obtain a cellulose/chitosan solution; adding polyvinyl alcohol and chitin into a NaOH/urea solution to obtain a polyvinyl alcohol/chitin solution;
3) and uniformly mixing the cellulose/chitosan solution and the polyvinyl alcohol/chitin solution, and removing bubbles to obtain the response type concrete antifreeze agent.
Further, in the step 1), in the NaOH/urea solution, the solvent is water, the mass percent of NaOH is 1-3%, and the mass percent of urea is 3-5%.
Further, in the step 2), the preparation process of the cellulose/chitosan solution specifically comprises the following steps: adding hydroxyethyl cellulose into NaOH/urea solution at 35-45 ℃, stirring, adding carboxylated chitosan, performing ultrasonic dispersion, and sequentially freezing and thawing to obtain the cellulose/chitosan solution.
Furthermore, the fineness of the hydroxyethyl cellulose is more than or equal to 90 mu m, the stirring time is 5-15min, and the ultrasonic power is more than or equal to 160W; the freezing temperature is between 25 ℃ below zero and 15 ℃ below zero, and the time is 10 to 15 hours; the thawing temperature is 35-45 ℃; the mass percentage of the hydroxyethyl cellulose in the cellulose/chitosan solution is 5-7%; the carboxylated chitosan is carboxymethyl chitosan, and the mass percentage of the carboxylated chitosan in the cellulose/chitosan solution is 0.5-1.5%.
Further, in the step 2), the preparation process of the polyvinyl alcohol/chitin solution specifically comprises the following steps: adding polyvinyl alcohol into water at 75-85 ℃, cooling to below 50 ℃ after the polyvinyl alcohol is completely dissolved, mixing with NaOH/urea solution, adding chitin, and uniformly stirring to obtain the polyvinyl alcohol/chitin solution.
Further, the stirring temperature is 35-45 ℃ and the stirring time is 5-10 min; the mass percentage of the polyvinyl alcohol in the polyvinyl alcohol/chitin solution is 5-7%; the mass percentage of the chitin in the polyvinyl alcohol/chitin solution is 0.5-1.5%.
Further, in the step 3), the mass ratio of the cellulose/chitosan solution to the polyvinyl alcohol/chitin solution is 3 (1-9), and the mixture is stirred for 10-20min after being mixed; the method for removing the bubbles comprises the following steps: firstly, ultrasonic treatment is adopted, and then the mixture is placed in a vacuum box to eliminate residual bubbles; the ultrasonic power is more than or equal to 300W, the ultrasonic time is 15-20min, and the vacuum degree in the vacuum box is less than or equal to 60 Pa.
The response type concrete antifreeze agent is prepared by adopting the method.
The application of the response type concrete antifreeze agent is characterized in that the response type concrete antifreeze agent is added into a concrete mixture, and the mixing amount of the response type concrete antifreeze agent is 2-10% of the mass of a cementing material. And adding mixing water for 1min, then adding the antifreeze agent into the concrete mixture, and stirring and forming.
Further, the application process comprises the following steps:
s1) adding the response type concrete antifreeze agent into the concrete mixture, and stirring and forming;
s2) maintaining for 20-28h (preferably 24h) under natural conditions, and then removing the mould to obtain a concrete test block;
s3) placing the concrete test block in Ca (OH)2Curing in the saturated solution for 20-28h (preferably 24 h);
s4) carrying out freeze-thaw cycle treatment on the concrete test block;
s5) continued maintenance under standard conditions (to age 24 d).
In step S4), the freeze-thaw cycle processing process includes: freeze-thaw cycle for 7 times with a period of 24h, including freezing for 12h + thawing for 12h, i.e. freezing at-15 deg.C for 12h, and then non-flowing Ca (OH) at 18-22 deg.C2Thawing the saturated solution for 12 h. The freeze-thaw cycle treatment is used for forming polymer gel with certain strength in situ in the concrete.
The invention innovatively utilizes response type high-molecular polymer hydrogel as the concrete antifreeze agent by means of the ultrastrong sensitivity of the intelligent response material to the environment. The response type hydrogel is a functional polymer material integrating water absorption, water retention and slow release, is a special 'soft and wet' material with a three-dimensional network structure and certain mechanical strength, can retain a large amount of water in the material without dissolving, and can swell in water. The intelligent response type polymer can respond to the change of the external environment temperature to generate the conformation transformation, thereby causing the change of the physicochemical property of the polymer, and under the excitation action of the proper environment temperature, the polymer can generate the volume phase change.
The formation condition of the temperature response type polymer is freeze-thaw cycle, is consistent with the condition when concrete is subjected to freeze-thaw damage, has similarity with service conditions, and has the condition of forming porous and mechanical strength hydrogel in the concrete under the condition of the freeze-thaw cycle. Meanwhile, the hydrogel is a material with a three-dimensional network structure, has the characteristic of softness and wetness and good compatibility, and can be well adapted to a concrete system.
According to the concrete freeze-thaw damage mechanism and induction conditions and the unique physicochemical properties of the hydrogel expressed under the suitable excitation conditions, the invention finds the suitable raw material proportion and the preparation and use process, successfully utilizes the carboxylated chitosan, the hydroxyethyl cellulose, the chitin, the polyvinyl alcohol, the urea and the NaOH as the raw materials, and combines the suitable reaction temperature and the process method to prepare the polymer material with the temperature response. The method is characterized in that four high molecular polymers of carboxylated chitosan, hydroxyethyl cellulose, chitin and polyvinyl alcohol are taken as a crosslinking main body, a source solution is formed in a system taking urea and NaOH as media in a physical crosslinking mode, a high molecular chain correspondingly changes in motion under the condition of freeze-thaw cycle to form a gel-state substance, functional groups in the high molecular polymers such as carboxyl, hydroxyl, amino and the like endow a temperature response function, and the internal structure of the polymers is changed in a design temperature range and subjected to phase change behavior and mechanical property by combining with chemical environmental parameters of the media. The invention also successfully introduces the temperature response type hydrogel solution into the concrete, and the hydrogel is formed in situ in the hardened cement paste, so that the microstructure in the concrete is improved, and the frost resistance of the concrete in a freeze-thaw environment is improved.
Compared with the prior art, the invention has the following characteristics:
1) the concrete antifreeze agent is prepared from easily-obtained raw materials with low cost, is a response type hydraulic collagen solution, is simple in use method, can be directly doped into a concrete mixture, and has fewer using limiting factors and simpler and more convenient construction compared with the traditional method of compacting by vibration and using an air entraining agent.
2) According to the invention, the in-situ generation of the hydrogel in the concrete is realized through freeze-thaw cycle and physical crosslinking, and the hydrogel can relieve freeze-thaw damage to the concrete in the concrete, and experiments show that the strength of the concrete doped with the hydrogel antifreeze agent is at least 5MPa higher than that of the concrete not doped with the hydrogel antifreeze agent after 50-300 freeze-thaw cycle experiments.
Drawings
FIG. 1 is a graph showing the test of the mass loss rate of concrete freeze-thawing in example 1;
FIG. 2 is a graph showing the relative dynamic elastic modulus test of concrete freeze-thaw in example 1.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.
Example 1:
a response type concrete antifreeze agent comprises main raw materials of carboxylated chitosan, hydroxyethyl cellulose, chitin, polyvinyl alcohol, urea and sodium hydroxide, and is shown in the following table 1:
TABLE 1 reagents used in the assay
The raw solution was designed according to the ratio of the antifreeze to give the following table 2:
TABLE 2 proportioning design of antifreeze raw solution
The antifreeze agent can be prepared by uniformly mixing the cellulose/chitosan original solution and the PVA/chitin original solution, and two formulas (mass ratio) for preparing the antifreeze agent are selected and shown in Table 3:
TABLE 3 antifreeze ratio
Raw materials for preparing common concrete: P.O 42.5.5 Portland cement; the natural river sand is medium sand with fineness modulus of 2.7, and each index meets the standard specification requirement of building sand (GB/T14684-2011); pebbles with 5-40mm continuous gradation are selected, and all indexes meet the standard specification requirements of building pebbles and gravels (GB/T14685-2011). The mixing water directly uses pure tap water, and each index meets the standard specification requirement of concrete mixing water standard (JGJ 63-2006). The mix proportion design is carried out according to the design rule of common concrete mix proportion (JGJ55-2011), and the designed strength grade of the concrete is C40. The fit ratios are shown in table 4:
TABLE 4 concrete mix proportions
The process comprises the following steps:
s1, preparing a solution containing 2 wt% of NaOH and 4 wt% of urea;
s2 adding hydroxyethyl cellulose (fineness not less than 90 μm) into the solution prepared in S1 under water bath heating at 40 deg.C, magnetically stirring for 10min under water bath heating, adding carboxymethyl chitosan, and performing ultrasonic treatment at 180W for 2min to rapidly disperse the reagent. Then putting the solution into a freezer for freezing for 12h at (-20 ℃), and then carrying out accelerated thawing under the water bath heating condition of 40 ℃ to obtain a cellulose/chitosan solution stock solution;
s3, dissolving polyvinyl alcohol in deionized water under the condition of heating and stirring in a water bath at the temperature of 80 ℃, heating in the water bath until the polyvinyl alcohol is completely dissolved, then cooling the polyvinyl alcohol solution to the temperature below 50 ℃, adding the solution prepared in the step S1, uniformly mixing the polyvinyl alcohol solution and the solution, adding chitin, heating in the water bath at the temperature of 40 ℃, and simultaneously stirring in a vortex type stirrer at a high speed for 5min to prepare a PVA/chitin solution;
and S4, mixing the cellulose/chitosan solution and the PVA/chitin solution prepared in the S2 and the S3 according to the mass ratio of 1:1 and 1:3 respectively at room temperature, and stirring the mixture in a mechanical vortex type stirrer at an accelerated speed for 10min at a medium-high speed. Then eliminating bubbles in the liquid by ultrasonic treatment, wherein the ultrasonic power is 360W, the ultrasonic time is controlled to be 20min, the residual bubbles are eliminated in a vacuum environment, and the vacuum degree is 20Pa, so that the hydrogel antifreeze agent is finally obtained;
s5, mixing an antifreeze agent with the mass fraction of 8 wt% and 10 wt% of the mass of the cement into the common concrete according to the design of the mixing proportion, and mixing the antifreeze agent into the concrete mixture after adding the mixing water for 1min in the stirring process;
s6, curing for 24h under natural conditions after forming and removing the die;
s7 placing the concrete test block in Ca (OH) after removing the mould2Curing in the saturated solution for 24 hours;
s8, performing freeze-thaw treatment on the concrete test block, wherein the freeze-thaw cycle time is set as follows: freezing for 12 h/thawing for 12h, freezing at-15 deg.C for 12h, and then freezing at 20 + -2 deg.C in the presence of non-flowing Ca (OH)2Thawing in the saturated solution for 12h, wherein the cycle period of one time is 24h, and the test freeze-thaw cycle times are 7;
and S9, curing to the specified age under standard conditions.
TABLE 5 antifreeze agent-doped concrete antifreeze property test mixing proportion
The test is carried out according to a freeze-thaw test method specified in standard of test methods for long-term performance and durability of ordinary concrete (GBT 50082-; taking out the test piece from a curing room at the age of 24 days of freezing and thawing, putting the test piece into water at the temperature of (20 +/-2) DEG C for soaking for 4 days, taking out the test piece at the age of 28 days, and performing a freezing and thawing cycle test; in the freezing and thawing process, the central temperature of the test piece is controlled to be (-18 +/-2) DEG C at the lowest temperature, to be (5 +/-2) DEG C at the highest temperature, and the freezing and thawing cycle time is controlled to be 2.5h +/-4 h. When the relative dynamic elastic modulus is lower than 60% or the mass loss rate exceeds 5%, the freeze-thaw test is stopped. The results of the tests performed on 5 groups in table 5 are shown in fig. 1 and 2. It can be seen that when the doping amount of the antifreeze agent is 8% and 10%, the doping amount of the antifreeze agent can reduce the mass loss rate of concrete and the reduction of the relative dynamic elastic modulus when the antifreeze agent undergoes the same freeze-thaw cycle times, which indicates that the doping amount of the response type concrete antifreeze agent can obviously improve the frost resistance of the concrete.
Example 2:
a response type concrete antifreeze agent is prepared by the following steps:
1) adding NaOH and urea into water to obtain a NaOH/urea solution;
2) adding hydroxyethyl cellulose and carboxylated chitosan into a NaOH/urea solution to obtain a cellulose/chitosan solution; adding polyvinyl alcohol and chitin into a NaOH/urea solution to obtain a polyvinyl alcohol/chitin solution;
3) and uniformly mixing the cellulose/chitosan solution and the polyvinyl alcohol/chitin solution, and removing bubbles to obtain the response type concrete antifreeze agent.
In the step 1), in the NaOH/urea solution, the solvent is water, the mass percent of NaOH is 1%, and the mass percent of urea is 5%.
In the step 2), the preparation process of the cellulose/chitosan solution is specifically as follows: adding hydroxyethyl cellulose into NaOH/urea solution at 35 ℃, stirring, adding carboxylated chitosan, performing ultrasonic dispersion, and sequentially freezing and thawing to obtain cellulose/chitosan solution. The fineness of the hydroxyethyl cellulose is 200 mu m, the stirring time is 5min, and the ultrasonic power is 300W; the freezing temperature is-25 ℃ and the time is 15 h; the thawing temperature is 35 ℃; the mass percentage of the hydroxyethyl cellulose in the cellulose/chitosan solution is 7 percent; the carboxylated chitosan is carboxymethyl chitosan, and the mass percentage of the carboxylated chitosan in the cellulose/chitosan solution is 0.5%.
The preparation process of the polyvinyl alcohol/chitin solution specifically comprises the following steps: adding polyvinyl alcohol into water at 85 ℃, cooling to 30 ℃ after the polyvinyl alcohol is completely dissolved, mixing with NaOH/urea solution, adding chitin, and uniformly stirring to obtain polyvinyl alcohol/chitin solution. Stirring at 35 deg.C for 10 min; the mass percentage of the polyvinyl alcohol in the polyvinyl alcohol/chitin solution is 5 percent; the mass percentage of the chitin in the polyvinyl alcohol/chitin solution is 1.5%.
In the step 3), the mass ratio of the cellulose/chitosan solution to the polyvinyl alcohol/chitin solution is 3:1, and the mixture is stirred for 20 min; the method for removing the bubbles comprises the following steps: firstly, ultrasonic treatment is adopted, and then the mixture is placed in a vacuum box to eliminate residual bubbles; the ultrasonic power is 300W, the ultrasonic time is 20min, and the vacuum degree in the vacuum box is 10 Pa.
The application of the response type concrete antifreeze agent is characterized in that the response type concrete antifreeze agent is added into a concrete mixture, and the mixing amount of the response type concrete antifreeze agent is 10% of the mass of a cementing material.
The application process comprises the following steps:
s1) adding the response type concrete antifreeze agent into the concrete mixture, and stirring and forming;
s2) maintaining for 20h under natural conditions, and then removing the mould to obtain a concrete test block;
s3) placing the concrete test block in Ca (OH)2Curing in the saturated solution for 28 h;
s4) carrying out freeze-thaw cycle treatment on the concrete test block;
s5) continuing the curing under standard conditions.
Example 3:
a response type concrete antifreeze agent is prepared by the following steps:
1) adding NaOH and urea into water to obtain a NaOH/urea solution;
2) adding hydroxyethyl cellulose and carboxylated chitosan into a NaOH/urea solution to obtain a cellulose/chitosan solution; adding polyvinyl alcohol and chitin into a NaOH/urea solution to obtain a polyvinyl alcohol/chitin solution;
3) and uniformly mixing the cellulose/chitosan solution and the polyvinyl alcohol/chitin solution, and removing bubbles to obtain the response type concrete antifreeze agent.
In the step 1), in the NaOH/urea solution, the solvent is water, the mass percent of NaOH is 3%, and the mass percent of urea is 3%.
In the step 2), the preparation process of the cellulose/chitosan solution is specifically as follows: adding hydroxyethyl cellulose into a NaOH/urea solution at 45 ℃, stirring, adding carboxylated chitosan, performing ultrasonic dispersion, and sequentially freezing and thawing to obtain a cellulose/chitosan solution. The fineness of the hydroxyethyl cellulose is 90 mu m, the stirring time is 15min, and the ultrasonic power is 160W; the freezing temperature is-15 ℃ and the time is 10 h; the thawing temperature is 45 ℃; the mass percentage of the hydroxyethyl cellulose in the cellulose/chitosan solution is 5 percent; the carboxylated chitosan is carboxymethyl chitosan, and the mass percentage of the carboxylated chitosan in the cellulose/chitosan solution is 1.5%.
The preparation process of the polyvinyl alcohol/chitin solution specifically comprises the following steps: adding polyvinyl alcohol into water at 75 ℃, cooling to 50 ℃ after the polyvinyl alcohol is completely dissolved, mixing with NaOH/urea solution, adding chitin, and uniformly stirring to obtain polyvinyl alcohol/chitin solution. Stirring at 45 deg.C for 5 min; the mass percentage of the polyvinyl alcohol in the polyvinyl alcohol/chitin solution is 7 percent; the mass percentage of the chitin in the polyvinyl alcohol/chitin solution is 0.5 percent.
In the step 3), the mass ratio of the cellulose/chitosan solution to the polyvinyl alcohol/chitin solution is 1:3, and the mixture is stirred for 10 min; the method for removing the bubbles comprises the following steps: firstly, ultrasonic treatment is adopted, and then the mixture is placed in a vacuum box to eliminate residual bubbles; the ultrasonic power is 500W, the ultrasonic time is 15min, and the vacuum degree in the vacuum box is 60 Pa.
The application of the response type concrete antifreeze agent is characterized in that the response type concrete antifreeze agent is added into a concrete mixture, and the mixing amount of the response type concrete antifreeze agent is 2% of the mass of a cementing material.
The application process comprises the following steps:
s1) adding the response type concrete antifreeze agent into the concrete mixture, and stirring and forming;
s2) maintaining for 28h under natural conditions, and then removing the mould to obtain a concrete test block;
s3) placing the concrete test block in Ca (OH)2Curing in the saturated solution for 20 h;
s4) carrying out freeze-thaw cycle treatment on the concrete test block;
s5) continuing the curing under standard conditions.
Example 4:
a response type concrete antifreeze agent is prepared by the following steps:
1) adding NaOH and urea into water to obtain a NaOH/urea solution;
2) adding hydroxyethyl cellulose and carboxylated chitosan into a NaOH/urea solution to obtain a cellulose/chitosan solution; adding polyvinyl alcohol and chitin into a NaOH/urea solution to obtain a polyvinyl alcohol/chitin solution;
3) and uniformly mixing the cellulose/chitosan solution and the polyvinyl alcohol/chitin solution, and removing bubbles to obtain the response type concrete antifreeze agent.
In the step 1), in the NaOH/urea solution, the solvent is water, the mass percent of NaOH is 2%, and the mass percent of urea is 4%.
In the step 2), the preparation process of the cellulose/chitosan solution is specifically as follows: adding hydroxyethyl cellulose into NaOH/urea solution at 40 ℃, stirring, adding carboxylated chitosan, performing ultrasonic dispersion, and sequentially freezing and thawing to obtain cellulose/chitosan solution. The fineness of the hydroxyethyl cellulose is 120 mu m, the stirring time is 10min, and the ultrasonic power is 200W; the freezing temperature is-20 ℃ and the time is 12 h; the thawing temperature is 40 ℃; the mass percentage of the hydroxyethyl cellulose in the cellulose/chitosan solution is 6 percent; the carboxylated chitosan is carboxymethyl chitosan, and the mass percentage of the carboxylated chitosan in the cellulose/chitosan solution is 1%.
The preparation process of the polyvinyl alcohol/chitin solution specifically comprises the following steps: adding polyvinyl alcohol into water at 80 ℃, cooling to 40 ℃ after the polyvinyl alcohol is completely dissolved, mixing with NaOH/urea solution, adding chitin, and uniformly stirring to obtain polyvinyl alcohol/chitin solution. Stirring at 40 deg.C for 7 min; the mass percentage of the polyvinyl alcohol in the polyvinyl alcohol/chitin solution is 6 percent; the mass percentage of the chitin in the polyvinyl alcohol/chitin solution is 1 percent.
In the step 3), the mass ratio of the cellulose/chitosan solution to the polyvinyl alcohol/chitin solution is 1:1, and the mixture is stirred for 15 min; the method for removing the bubbles comprises the following steps: firstly, ultrasonic treatment is adopted, and then the mixture is placed in a vacuum box to eliminate residual bubbles; the ultrasonic power is 350W, the ultrasonic time is 17min, and the vacuum degree in the vacuum box is 30 Pa.
The application of the response type concrete antifreeze agent is characterized in that the response type concrete antifreeze agent is added into a concrete mixture, and the mixing amount of the response type concrete antifreeze agent is 6% of the mass of a cementing material.
The application process comprises the following steps:
s1) adding the response type concrete antifreeze agent into the concrete mixture, and stirring and forming;
s2) maintaining for 24h under natural conditions, and then removing the mould to obtain a concrete test block;
s3) placing the concrete test block in Ca (OH)2Curing in the saturated solution for 24 hours;
s4) carrying out freeze-thaw cycle treatment on the concrete test block;
s5) continuing the curing under standard conditions.
The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.
Claims (8)
1. A preparation method of a response type concrete antifreeze agent is characterized by comprising the following steps:
1) adding NaOH and urea into water to obtain a NaOH/urea solution;
2) adding hydroxyethyl cellulose and carboxylated chitosan into a NaOH/urea solution to obtain a cellulose/chitosan solution; adding polyvinyl alcohol and chitin into a NaOH/urea solution to obtain a polyvinyl alcohol/chitin solution;
3) uniformly mixing the cellulose/chitosan solution and the polyvinyl alcohol/chitin solution and removing bubbles to obtain the response type concrete antifreeze agent;
in the step 2), the preparation process of the cellulose/chitosan solution specifically comprises the following steps: adding hydroxyethyl cellulose into a NaOH/urea solution at 35-45 ℃, stirring, adding carboxylated chitosan, performing ultrasonic dispersion, and sequentially freezing and thawing to obtain the cellulose/chitosan solution;
in the step 2), the preparation process of the polyvinyl alcohol/chitin solution specifically comprises the following steps: adding polyvinyl alcohol into water at 75-85 ℃, cooling to below 50 ℃ after the polyvinyl alcohol is completely dissolved, mixing with NaOH/urea solution, adding chitin, and uniformly stirring to obtain the polyvinyl alcohol/chitin solution.
2. The method for preparing the response type concrete antifreeze agent according to claim 1, wherein in the step 1), the solvent is water, the mass percent of NaOH is 1-3%, and the mass percent of urea is 3-5%.
3. The preparation method of the response type concrete antifreeze agent according to claim 1, wherein the fineness of the hydroxyethyl cellulose is more than or equal to 90 μm, the stirring time is 5-15min, and the ultrasonic power is more than or equal to 160W; the freezing temperature is between 25 ℃ below zero and 15 ℃ below zero, and the time is 10 to 15 hours; the thawing temperature is 35-45 ℃; the mass percentage of the hydroxyethyl cellulose in the cellulose/chitosan solution is 5-7%; the carboxylated chitosan is carboxymethyl chitosan, and the mass percentage of the carboxylated chitosan in the cellulose/chitosan solution is 0.5-1.5%.
4. The method for preparing the response type concrete antifreeze agent according to claim 1, wherein the stirring temperature is 35-45 ℃ and the time is 5-10 min; the mass percentage of the polyvinyl alcohol in the polyvinyl alcohol/chitin solution is 5-7%; the mass percentage of the chitin in the polyvinyl alcohol/chitin solution is 0.5-1.5%.
5. The preparation method of the response type concrete antifreeze agent according to claim 1, wherein in the step 3), the mass ratio of the cellulose/chitosan solution to the polyvinyl alcohol/chitin solution is 3 (1-9), and the mixture is stirred for 10-20 min; the method for removing the bubbles comprises the following steps: firstly, ultrasonic treatment is adopted, and then the mixture is placed in a vacuum box to eliminate residual bubbles; the ultrasonic power is more than or equal to 300W, the ultrasonic time is 15-20min, and the vacuum degree in the vacuum box is less than or equal to 60 Pa.
6. A responsive concrete antifreeze agent, characterized in that it is prepared by the method of any of claims 1 to 5.
7. The use of a responsive concrete antifreeze according to claim 6 wherein said responsive concrete antifreeze is added to the concrete mixture in an amount of from 2 to 10% by weight of cementitious material.
8. The use of a responsive concrete antifreeze agent according to claim 7, wherein said use comprises the steps of:
s1) adding the response type concrete antifreeze agent into the concrete mixture, and stirring and forming;
s2) maintaining for 20-28h under natural conditions, and then removing the mould to obtain a concrete test block;
s3) placing the concrete test block in Ca (OH)2Curing in saturated solution20-28h；
S4) carrying out freeze-thaw cycle treatment on the concrete test block;
s5) continuing the curing under standard conditions.
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