Chitosan-based temperature-sensitive concrete water reducing agent as well as preparation method and application thereof

Abstract

The invention discloses a novel chitosan-based temperature-sensitive concrete water reducing agent and a preparation method and application thereof, the lower critical solution temperature (LCST) of the chitosan-based temperature-sensitive concrete water reducing agent is in the range of 40-80 DEG C, and the lower critical temperature-sensitive stimulation-response process of the chitosan-based temperature-sensitive concrete water reducing agent is essentially changed along with the temperature. The dissolution-aggregation behavior of water reducing agent molecules in an aqueous solution is caused by the mutual competitive action among side chains consisting of alkyl polyoxyethylene groups on the side chains, chitosan groups, polyoxyethylene groups and-COO-on a main chain or among the side chains, the side groups and dissolved water. When hydration heat or friction stir results in the temperature Tgt of the material; during LCST, due to the action relation, the chitosan-based temperature-sensitive concrete water reducing agent is agglomerated in a cement concrete pore liquid to form a micelle-shaped structure, the aggregation of adsorbed cement particles and aggregates is more compact, and along with the release of hydration reaction heat, the working performance of the concrete under the change of internal temperature is actively micro-regulated and controlled; the strength of the concrete can be remarkably improved, and the condition that the concrete cracks due to temperature rise thermal expansion stress is improved.

Description

Technical Field

[0001] This invention belongs to the field of concrete admixture technology, specifically relating to a chitosan-based temperature-sensitive concrete water-reducing agent disclosed for the first time, its preparation method, and its application. Background Technology

[0002] Admixtures have become an indispensable component of concrete. The rapid development of modern concrete technology relies heavily on the application of high-performance water-reducing agents; even low dosages of admixtures can significantly impact the workability of concrete. The research, development, and production of concrete water-reducing agents involve multiple fields, and their development has undergone generations of evolution from ordinary water-reducing agents to high-efficiency water-reducing agents to high-performance water-reducing agents. Currently, the mainstream water-reducing agent on the market is the polycarboxylate-based high-performance water-reducing agent, characterized by low dosage, high water reduction rate, strong dispersibility, and minimal slump loss over time. The main chain of polycarboxylate-based water-reducing agents is linked by the side groups -COO... - With Ca on the surface of cement particles 2+ Polycarboxylate superplasticizers adsorb onto the surface of particles through complexation or electrostatic forces, forming an electrostatic layer that creates repulsive interactions between particles. Simultaneously, long PEG side chains extend into the cement pore liquid, forming an adsorption layer. This steric hindrance inhibits flocculation between cement particles, improving the dispersibility of the paste. Furthermore, polycarboxylate superplasticizers can further improve and ensure better workability and strength of concrete mixtures through the selection of functional monomers, the acid / ether ratio of raw materials, and the design of molecular topology.

[0003] Concrete is a mixture composed of coarse / fine aggregates, cementitious materials, mineral powder, admixtures and mixing water. Since the heat dissipation inside concrete is slow, a large amount of heat generated by the cement hydration reaction will lead to too large temperature difference between the inside and outside, and then generate temperature stress. When the temperature stress exceeds the compressive strength of concrete, temperature cracks will occur, seriously affecting the durability and integrity of the structure. Currently, the common means to improve this problem are: ① using low-heat cement or reducing the cement dosage (such as adding mineral admixtures or water reducers) to reduce the generation of hydration heat; ② using ice water for mixing or cooling the aggregates to reduce the initial temperature of the slurry; ③ embedding cooling water pipes or increasing the heat preservation and moisture preservation layer to reduce the temperature of concrete. Among the above means, although using low-heat cement or reducing the cement dosage can reduce the hydration heat, there are problems of high cost and reduction of the early strength of concrete, and for large-volume concrete structures, there may still be a large absolute temperature rise and temperature difference between the inside and outside, and the problem cannot be fundamentally solved; other methods can only simply cool the concrete structure, but they are still only treating the symptoms rather than the root cause: the heat preservation and moisture preservation layer can only be laid on the surface of the concrete, which not only cannot reduce the highest temperature in the internal core area, but may even have the opposite effect; embedding cooling water pipes requires precise control of the cooling rate. If the water flow control is improper, it may lead to too large temperature difference between the inside and outside or too fast cooling rate, instead causing cracks, and stress concentration is likely to occur around the water pipes, affecting the structural reliability. In summary, there is no effective solution to the temperature rise problem in the existing technology. Summary of the Invention

[0004] Aiming at the problem of hydration heat release and temperature rise of concrete, the present invention for the first time designs and synthesizes a chitosan-based thermosensitive concrete water reducer with lower critical solution temperature (LCST) characteristics.

[0005] In addition, the present invention also provides a preparation method and application of the above chitosan-based thermosensitive concrete water reducer.

[0006] The technical solution of the present invention is as follows:

[0007] A chitosan-based thermosensitive concrete water reducer has a structure shown in formula (A1):

[0008]

[0009] Formula (A1);

[0010] Wherein, -Z1 is -H or -COOH; -R, -Z2, -Z3, -Z4 and -Z5 are respectively -H or -CH3; 20 ≤ p4 ≤ 150; 0 < p5 ≤ 50; g-link is an ether bond or an ester bond; X is an alkyl group with 4 to 50 carbon atoms; Y is -NH2 or -OH.

[0011] In some preferred embodiments, the above-mentioned chitosan-based thermosensitive concrete water-reducing agent is prepared by free radical polymerization of the following components by weight percentage: 0.05~4wt% chitosan, 0.8~15wt% first monomer, 20~40wt% second monomer, 2~8wt% acrylic acid, 10 -3 ~3wt% third monomer, 0.02~1.2wt% mercaptopropionic acid, 0.1~6wt% redox initiation system, balance water;

[0012] Chitosan can be directly introduced into free radical polymerization; or, chitosan can be introduced into free radical polymerization through modification.

[0013] The first monomer is selected from at least one of (meth)allyl alkyl polyoxyethylene ether, (meth)acrylate alkyl polyoxyethylene ester and maleic alkyl polyoxyethylene ester, wherein the alkyl group of the first monomer is C4 to C50 alkyl.

[0014] The second monomer is an unsaturated polyoxyethylene ether and / or an unsaturated polyoxyethylene ester, with an average molecular weight of 880 to 6600.

[0015] The third monomer is (meth)allyl glycidyl ether and / or (meth)acrylate glycidyl ester.

[0016] In some preferred embodiments, the viscosity of chitosan is 5~1000 mPa·s, and the degree of deacetylation of chitosan is ≥75%.

[0017] In some preferred embodiments, the viscosity of chitosan is 5~500 mPa·s, and the degree of deacetylation of chitosan is ≥90%.

[0018] In some preferred embodiments, the redox initiation system consists of H2O2 and ascorbic acid.

[0019] The preparation method of the above-mentioned chitosan-based thermosensitive concrete water-reducing agent involves introducing chitosan in a modified manner. The preparation method includes the following steps: dissolving chitosan and a third monomer in water and stirring at room temperature for 10 hours to prepare an aqueous solution with a chitosan concentration of no more than 3 wt%. Then, dissolving the first monomer, acrylic acid, and the second monomer in the aqueous solution containing chitosan and the third monomer, followed by adding mercaptopropionic acid and a redox initiation system, and reacting for 1 to 3 hours, during which the system temperature is controlled not to exceed 70°C, thus completing the preparation.

[0020] The preparation method of the above-mentioned chitosan-based thermosensitive concrete water-reducing agent involves introducing chitosan in a modified manner during or after the free radical polymerization reaction. The preparation method includes the following steps: preparing a chitosan aqueous solution with a concentration of no more than 3 wt%; then dissolving the first monomer, acrylic acid, the second monomer, and the third monomer in the remaining water; then adding mercaptopropionic acid and a redox initiation system, initiating and reacting for 0.5 to 3 hours; adding the chitosan aqueous solution during or after the polymerization reaction, and continuing the reaction for 1 to 10 hours, controlling the system temperature to not exceed 70°C throughout the process.

[0021] The preparation method of the above-mentioned chitosan-based thermosensitive concrete water-reducing agent involves directly introducing chitosan into a free radical polymerization reaction. The preparation method includes the following steps: dissolving chitosan, the first monomer, the second monomer, the third monomer, and acrylic acid in water, then adding mercaptopropionic acid and a redox initiation system, initiating and reacting for 2 to 10 hours, during which the system temperature is controlled not to exceed 70°C, and the product is obtained.

[0022] The above-mentioned chitosan-based thermosensitive concrete water-reducing agent is used to improve the later-stage segregation and bleeding phenomenon and to increase the compressive strength of concrete.

[0023] A concrete water-reducing agent composite comprising the above-mentioned chitosan-based thermosensitive concrete water-reducing agent.

[0024] The present invention has at least the following beneficial effects:

[0025] This invention provides a chitosan-based thermosensitive concrete water-reducing agent disclosed for the first time, with a lower critical temperature response (LCST) in the range of 40–80°C. Its LCST essentially involves changes in temperature caused by the interaction of alkyl polyoxyethylene groups on the side chain, the chitosan group, the polyoxyethylene group, and the -COO group on the main chain. - The competitive interactions between the side chains and side groups, or between the side chains, side groups, and dissolved water, lead to the dissolution-aggregation behavior of water-reducing agent molecules in aqueous solutions. When the temperature of the material T > LCST due to hydration heat or stirring friction, this interaction causes the chitosan-based thermosensitive concrete water-reducing agent to abruptly change from a dissolved state to a coagulated state in the concrete pore fluid, forming a micellar structure. This may also make the adsorbed cement particles and aggregates more densely aggregated. As the hydration reaction proceeds, it actively micro-regulates the workability of concrete under internal temperature changes, thereby significantly improving the strength of concrete and mitigating cracking caused by thermal expansion due to temperature rise. Attached Figure Description

[0026] Figure 1 The graph shows the relationship between the transmittance of the aqueous solution of the chitosan-based thermosensitive concrete water-reducing agent prepared in Examples 1 and 4 and temperature (λ = 640 nm). Detailed Implementation

[0027] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0028] In the following examples, unless otherwise specified, the water used can be one or more of distilled water, purified water, drinking water, and tap water; the detection methods in the following examples are conventional detection methods unless otherwise specified; the reagents in the following examples are commercially available unless otherwise specified. The term "(methyl)" in the text indicates that methyl is optional; for example, glycidyl methacrylate can be selected as glycidyl methacrylate or glycidyl acrylate. The common polycarboxylate superplasticizer used in Example 7 is ZS-M90M manufactured by Zhongshi (Fujian) New Building Materials Technology Co., Ltd.

[0029] The specific operation of "adding the mercaptopropionic acid and the redox initiation system" in the claim is as follows: dissolving ascorbic acid in a small amount of water, and then adding it, along with H2O2 and mercaptopropionic acid, to the reaction system.

[0030] Example 1

[0031] In this embodiment, the following raw materials were used for preparation: 0.8g of chitosan (degree of deacetylation 85%, viscosity 20mPa·s); 2.5g of the first monomer, which is alkyl polyoxyethylene methacrylate (CH2C(CH3)CO-(OCH2CH2)). m -OC n1 H n2 n1=14, n2=29, m=9~11); the second monomer 30g is an unsaturated polyoxyethylene ether, specifically isopentenyl alcohol polyoxyethylene ether (M). n =2400); the third monomer 0.3g, which is glycidyl (meth)acrylate; acrylic acid 5.5g; chain transfer agent mercaptopropionic acid 0.35g; redox initiation system, including 0.35g H2O2 and 0.2g ascorbic acid; water 60g.

[0032] First, chitosan and the third monomer were dissolved in 56g of water and stirred for 10 hours to prepare an aqueous solution. Then, the first monomer, the second monomer, and acrylic acid were dissolved in the aqueous solution to obtain a monomer solution. Ascorbic acid was first dissolved in 4g of water, and then added to the monomer solution along with H2O2 and mercaptopropionic acid to initiate and react for 3 hours. During the reaction, the system temperature was controlled not to exceed 50℃, thus obtaining the chitosan-based thermosensitive concrete water-reducing agent.

[0033] When the concentration of chitosan-based thermosensitive concrete water-reducing agent is 2.5 mg / mL, its LCST is measured to be 55.6℃.

[0034] Example 2

[0035] In this embodiment, the following raw materials were used for preparation: 0.2 g of chitosan with a degree of deacetylation of 90% and a viscosity of 10 mPa·s; 0.18 g of chitosan with a degree of deacetylation of 80% and a viscosity of 500 mPa·s; and 2.5 g of the first monomer, which is allyl hexadecane polyoxyethylene ether (wherein: -(OCH2CH2)). m -, m=20); the second monomer 35g, is an allyl polyoxyethylene ether of the unsaturated polyoxyethylene ether class (M n =2400); the third monomer 0.02g, which is methyl allyl glycidyl ether; acrylic acid 3g; chain transfer agent mercaptopropionic acid 0.3g; redox initiation system, including 0.5g H2O2 and 0.3g ascorbic acid; water 71g.

[0036] First, two types of chitosan with different viscosities and degrees of deacetylation were mixed and dissolved in 30g of water to prepare a chitosan aqueous solution. Then, the first monomer, the second monomer, the third monomer, and acrylic acid were dissolved in 35g of water to obtain a monomer solution. Next, ascorbic acid was dissolved in 6g of water, and then added to the monomer solution along with H2O2 and mercaptopropionic acid to initiate and react for 2 hours. Finally, the chitosan aqueous solution was added to the reaction system and the reaction continued for 5 hours. The temperature of the system was controlled not to exceed 55℃ throughout the process, thus obtaining a chitosan-based thermosensitive concrete water-reducing agent.

[0037] When the concentration of chitosan-based temperature-sensitive concrete water-reducing agent is 2.5 mg / mL, its LCST is measured to be 60℃.

[0038] Example 3

[0039] In this embodiment, the following raw materials were used for preparation: 0.6g of chitosan (80% deacetylation, viscosity 150mPa·s); 7g of the first monomer, which is maleic acid monoalkyl polyoxyethylene ester (HOOCCHCHCO-(OCH2CH2)). m -OC n1 H n2 n1=18, n2=37, m=7-15); the second monomer is 28g, which is an unsaturated polyoxyethylene ether of the isopentenyl alcohol polyoxyethylene ether type (M n =2400); the third monomer 0.3g, which is glycidyl acrylate; acrylic acid 6g; chain transfer agent mercaptopropionic acid 0.3g; redox initiation system, including 0.5g H2O2 and 0.3g ascorbic acid; water 57g.

[0040] First, chitosan, the first monomer, and the second monomer are dissolved in 52g of water to obtain a monomer solution. Then, acrylic acid and the third monomer are dissolved in the monomer solution. Next, ascorbic acid is dissolved in 5g of water, and then added to the monomer solution along with H2O2 and mercaptopropionic acid. The reaction is initiated and carried out for 6.5h. During the reaction, the system temperature is controlled not to exceed 55℃, thus obtaining the chitosan-based thermosensitive concrete water-reducing agent.

[0041] When the concentration of chitosan-based thermosensitive concrete water-reducing agent is 2.5 mg / mL, its LCST is measured to be 67.3℃.

[0042] Example 4

[0043] In this embodiment, the following raw materials were used for preparation: 0.3g chitosan (92% deacetylation, viscosity 10mPa·s); the first monomer was 2g hexadecyl polyoxyethylene methacrylate (CH2C(CH3)CO-(OCH2CH2)). m -OC n1 H n2 (n1=16, n2=33, m=8-12) and 2g allyl octadecyl polyoxyethylene ether (CH2CHCH2-(OCH2CH2) m’ -OC n1’ H n2’ n1'=18, n2'=37, m'=5-8); the second monomer is 26g, which is 13g of unsaturated polyoxyethylene ether isopentenyl alcohol polyoxyethylene ether (M). n =2400) and 13g of unsaturated polyoxyethylene esters of methacrylate polyoxyethylene ester (M n =2400); the third monomer 0.3g, which is glycidyl methacrylate; acrylic acid 7g; chain transfer agent mercaptopropionic acid 0.1g; redox initiation system, including 0.2g H2O2 and 0.1g ascorbic acid; water 62g.

[0044] First, chitosan was dissolved in 20g of water to obtain a chitosan aqueous solution. Next, the first, second, and third monomers and acrylic acid were dissolved in 40g of water to obtain a monomer solution. Ascorbic acid was dissolved in 2g of water, and then added to the monomer solution along with H₂O₂ and mercaptopropionic acid, initiating the reaction for 0.5h. Finally, the chitosan aqueous solution was added to the reaction system, and the reaction continued for 7h with stirring, maintaining the temperature of the reaction system below 60℃ throughout the process, thus obtaining a chitosan-based thermosensitive concrete water-reducing agent.

[0045] When the concentration of chitosan-based temperature-sensitive concrete water-reducing agent is 2.5 mg / mL, its LCST is measured to be 60.5℃.

[0046] Example 5

[0047] In this embodiment, the following raw materials are used for preparation: 1 g of chitosan (degree of deacetylation 75%, viscosity 100 mPa·s); 15 g of the first monomer, which is octadecyl polyoxyethylene methacrylate (CH2C(CH3)CO-(OCH2CH2) m -OC n1 H n2 , n1 = 18, n2 = 37, m = 8); 35 g of the second monomer, which is isopentenyl polyoxyethylene ether (M n = 2400); 0.6 g of the third monomer, which is allyl glycidyl ether; 4.5 g of acrylic acid; 0.3 g of the chain transfer agent mercaptopropionic acid; a redox initiation system, including 0.3 g of H2O2 and 0.3 g of ascorbic acid; 66 g of water.

[0048] First, chitosan, the first monomer, the second monomer, acrylic acid and the third monomer are added to 63 g of water and stirred until dissolved to obtain a monomer solution. Ascorbic acid is dissolved in 3 g of water, and then it, together with H2O2 and mercaptopropionic acid, is added to the monomer solution to initiate the polymerization of the monomers and react for 6 h. During the reaction process, the temperature of the system is controlled not to exceed 55 °C, and thus the chitosan-based thermosensitive concrete water reducer is obtained.

[0049] When the concentration of the chitosan-based thermosensitive concrete water reducer is 2.5 mg / mL, its LCST is measured to be 67 °C.

[0050] Example 6 Thermosensitive properties of the chitosan-based thermosensitive concrete water reducer

[0051] The chitosan-based thermosensitive concrete water reducers obtained in Example 1 and Example 4 are prepared into an aqueous solution with a concentration of 2.5 mg / mL, and the change of the transmittance of the solution with temperature is measured (λ = 640 nm). The results are as Figure 1 shown.

[0052] It can be seen that the lower critical solution temperature of the chitosan-based thermosensitive concrete water reducer prepared in Example 1 is 55.6 °C, and the lower critical solution temperature of the chitosan-based thermosensitive concrete water reducer prepared in Example 4 is 60.5 °C.

[0053] When the solution temperature T < LCST, the chitosan-based thermosensitive concrete water reducer has good dissolution and dispersion performance in the aqueous solution, the solution is almost transparent, and the macroscopic manifestation is that the solution is transparent.

[0054] When the solution temperature T > LCST, the solubility of the chitosan-based temperature-sensitive concrete water-reducing agent decreases abruptly. This is because as the temperature increases, the dispersed phase state of the chitosan-based temperature-sensitive concrete water-reducing agent changes, leading to critical aggregation and the formation of micelles. Macroscopically, this manifests as a sudden increase in turbidity and a drop in transmittance to almost zero. This verifies the temperature-responsive characteristics of the chitosan-based temperature-sensitive concrete water-reducing agent. Based on the exothermic characteristics of the hydration reaction process in cement concrete, this chitosan-based temperature-sensitive water-reducing agent has value in engineering applications in improving the later-stage bleeding and segregation problems of concrete mixtures and mitigating stress cracking in concrete caused by the temperature rise due to hydration heat.

[0055] Example 7: Effects of Chitosan-Based Thermosensitive Concrete Water-Reducing Agent on Concrete Workability and Strength

[0056] The effects of this chitosan-based thermosensitive concrete water-reducing agent on the workability and strength of concrete were investigated. The specific test method was as follows: the dosage of the water-reducing agent (ordinary polycarboxylate water-reducing agent or concrete water-reducing agent composite obtained by mixing ordinary polycarboxylate water-reducing agent with chitosan-based thermosensitive water-reducing agent) was adjusted to make the initial slump of the concrete basically the same, and then the changes in slump and fluidity after 120 minutes were measured.

[0057] The concrete grade was C30 (non-pumped), with a sand ratio of 44 wt%, water content of 155 kg, sand of 821 kg, aggregate of 1065 kg, cement (P.O42.5) of 172 kg, fly ash of 66 kg, mineral powder of 92 kg, and a water-cement ratio of 0.5. The admixture dosage was 2.2 wt%, and the concentration of the concrete water-reducing agent composite was 12.5 wt%, with the chitosan-based thermosensitive concrete water-reducing agent accounting for 10-50 wt% of the total mass. The test results are shown in Table 1.

[0058] Table 1. Effects of admixtures on the workability and strength of concrete

[0059]

[0060] It can be seen that the slump of concrete using ordinary polycarboxylate superplasticizer decreased from 200 mm to 120 mm after 120 minutes, a decrease of 40%; while the slump of concrete using concrete superplasticizer composite decreased to 70 mm, showing a large slump loss and less spread than ordinary polycarboxylate superplasticizer. However, the application of chitosan-based thermosensitive superplasticizer in concrete significantly improves the compressive strength of concrete (>20%). This may be because the hydrophobic large alkyl segments in the side branches of the chitosan-based thermosensitive superplasticizer reduce the viscosity of the cement pore fluid, making the slurry more fluid and the particles more densely packed; on the other hand, after the cement generates heat of hydration, the chitosan-based thermosensitive concrete superplasticizer actively responds, dissipating some of the heat of hydration, changing the dispersion state of the concrete superplasticizer composite on the surface of the hydration products and in the pore fluid, and to a certain extent inhibiting the destructive effect of thermal expansion stress induced by concrete materials.

[0061] The test results show that the concrete with the admixture of concrete water-reducing agent composite has higher strength. Therefore, chitosan-based thermosensitive water-reducing agent can effectively improve the compressive strength grade of concrete.

[0062] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A chitosan-based temperature-sensitive concrete water-reducing agent, characterized in that, has a structure as shown in formula (A1): ； Formula (A1); wherein -Z1 is -H or -COOH; -R, -Z2, -Z3, -Z4 and -Z5 are each independently selected from -H or -CH3; 20 < p4 < 150; 0 < p5 < 50; g-link is an ether bond or an ester bond; X is an alkyl-C n H 2n+1 , 4 < n < 50; Y is -NH2 or -OH.

2. The chitosan-based temperature-sensitive concrete water reducer according to claim 1, wherein, 0.05 to 4 wt% chitosan, 0.8 to 15 wt% first monomer, 20 to 40 wt% second monomer, 2 to 8 wt% acrylic acid, 10 -3 ~3 wt% third monomer, 0.02 to 1.2 wt% mercaptopropionic acid, 0.1 to 6 wt% redox initiation system, and the balance water; The chitosan is directly introduced into the free radical polymerization reaction, or the chitosan is introduced into the free radical polymerization reaction in a modified manner. The first monomer is selected from at least one of (methyl) allyl alkyl polyoxyethylene ether, (methyl) acrylate alkyl polyoxyethylene ester and maleic acid alkyl polyoxyethylene ester, and the alkyl group of the first monomer is a C4-C50 alkyl group. The second monomer is an unsaturated polyoxyethylene ether and / or an unsaturated polyoxyethylene ester, and the average molecular weight of the second monomer is 880-6600. The third monomer is (methyl) allyl glycidyl ether and / or (methyl) acrylate glycidyl ester.

3. The chitosan-based temperature-sensitive concrete water reducer according to claim 2, wherein The viscosity of the chitosan is 5-1000 mPa·s, and the deacetylation degree of the chitosan is ≥ 75%.

4. The chitosan-based temperature-sensitive concrete water reducer according to claim 3, wherein, The viscosity of the chitosan is 5-500 mPa·s, and the deacetylation degree of the chitosan is ≥ 90%.

5. The chitosan-based temperature-sensitive concrete water reducer according to claim 2, wherein the chitosan is chitosan having a degree of deacetylation of 85% or more. The oxidation-reduction initiation system is composed of H2O2 and ascorbic acid.

6. The method for preparing the chitosan-based temperature-sensitive concrete water reducer according to any one of claims 2-5, characterized in that, The chitosan is introduced in a modified manner, and the preparation method comprises the following steps: dissolving the chitosan and the third monomer in water, stirring at room temperature for 10 h, preparing a water solution with a chitosan concentration of not more than 3 wt%, then dissolving the first monomer, the acrylic acid and the second monomer in the water solution containing the chitosan and the third monomer, then adding the mercaptopropionic acid and the oxidation-reduction initiation system, and reacting for 1-3 h, during which the temperature of the system is controlled to be not more than 70°C.

7. The method for preparing the chitosan-based temperature-sensitive concrete water reducer according to any one of claims 2-5, characterized in that, The chitosan is introduced in a modified manner, and the preparation method comprises the following steps: preparing a chitosan water solution with a concentration of not more than 3 wt%, then dissolving the first monomer, the acrylic acid, the second monomer and the third monomer in the remaining water, then adding the mercaptopropionic acid and the oxidation-reduction initiation system, initiating and reacting for 0.5-3 h, adding the chitosan water solution during or after the completion of the polymerization reaction, and continuing to react for 1-10 h, during which the temperature of the system is controlled to be not more than 70°C.

8. The method for preparing the chitosan-based temperature-sensitive concrete water reducer according to any one of claims 2-5, characterized in that, The chitosan is directly introduced into the free radical polymerization reaction, and the preparation method comprises the following steps: dissolving the chitosan, the first monomer, the second monomer, the third monomer and the acrylic acid in water, then adding the mercaptopropionic acid and the oxidation-reduction initiation system, initiating and reacting for 2-10 h, during which the temperature of the system is controlled to be not more than 70°C.

9. The chitosan-based temperature-sensitive concrete water reducing agent in any one of claims 2-5 is applied to improve the late segregation bleeding phenomenon and improve the compressive strength of concrete.

10. A concrete water reducing agent compound, characterized by, The chitosan-based temperature-sensitive concrete water reducing agent in any one of claims 1-5.

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