Temperature control type shrinkage compensation admixture for concrete and application thereof

Abstract

The application discloses a temperature control type shrinkage compensating admixture for concrete and application thereof and belongs to the technical field of concrete admixtures. The admixture comprises the following components in percentage by mass: expansion component 52-70%, modifier 8-13%, temperature-sensitive controlled release component 10-15% and water-retaining component 10-20%; the modifier comprises aluminum phosphate and / or aluminum titanate; the temperature-sensitive controlled release component comprises a hydration heat inhibiting component and a temperature-sensitive polymer wrapped on the surface of the hydration heat inhibiting component, and the temperature-sensitive polymer is polymerized from N-isopropyl acrylamide and N,N-dimethyl acrylamide. The admixture effectively reduces the shrinkage of concrete and significantly reduces the generation of cracks in the above aspects by compensating shrinkage through the expansion component, reducing temperature shrinkage through the modifier and the temperature-sensitive controlled release component and promoting the closing effect of the temperature-sensitive controlled release component through the water-retaining component.

Description

Technical Field

[0001] This invention belongs to the field of concrete admixture technology, specifically relating to a temperature-controlled shrinkage-compensating admixture for concrete and its application. Background Technology

[0002] Concrete is a multi-component mixture that is prone to shrinkage and cracking during the reaction process, which in turn affects the durability and safety of concrete components. Common forms of concrete shrinkage include plastic shrinkage, autogenous shrinkage, thermal shrinkage, and drying shrinkage.

[0003] Early hydration of concrete generates a large amount of heat of hydration. When this heat cannot dissipate quickly enough, the internal temperature of the concrete rises rapidly, making it prone to thermal shrinkage during cooling. Concrete typically reaches its temperature peak within 1-2 days. In civil engineering projects, concrete structures with a grade less than C40 and a minimum cross-sectional dimension less than 1.0m commonly used have a temperature peak in the central part of the concrete that is generally between 40 and 60°C; while high-grade, large-volume concrete or those constructed in summer can even reach 60 to 80°C.

[0004] Currently, commonly used concrete expansion agents compensate for concrete shrinkage through micro-expansion, while hydration heat inhibitors reduce the heat of hydration, thereby reducing temperature drop and shrinkage. Although concrete expansion agents can compensate for shrinkage through expansion, they cannot address the inherent shrinkage nature of concrete. Hydration heat inhibitors react throughout the early stages of the process, reducing the concrete temperature peak, but also inhibiting the early reaction temperature and significantly delaying the peak temperature time, resulting in reduced early strength, poor temperature suppression, and prolonged setting time. Chinese patent CN109293266 A discloses a hydration heat-inhibiting type expansion fiber composite crack-resistant agent, comprising, by mass percentage: 93.5%–98% expansion component; 1.5%–6% hydration heat-inhibiting component; and 0.5%–1.5% basalt fiber. The expansion component is a mixture of lightly calcined magnesia expansion agent and calcareous expansion agent in a mass ratio of 1:10–10:1; the hydration heat-inhibiting component is a mixture of ester compounds and retarder in a mass ratio of 1:1–5:1. This crack-resistant agent can effectively reduce the temperature rise of the concrete hydration reaction and compensate for shrinkage in the early and middle-to-late stages of concrete, significantly reducing temperature cracks and enhancing the crack resistance of concrete. However, the effect of this crack-resistant agent on improving the restricted expansion rate of concrete is limited, and its effect on reducing the heat of hydration of cement is also limited; moreover, the hydration heat inhibiting component contains a retarder, which, while reducing the concrete temperature peak, also affects the normal hydration process of concrete, resulting in a longer setting time and lower early strength. In order to reduce the release rate of retarder in the early stage of concrete, Chinese patent CN116425452A discloses a temperature-controlled phase change release type hydration heat regulating material and its preparation method and application. The hydration heat regulating material is a core-shell structure, which includes a carrier loaded with cement hydration inhibitor and a coating formed by phase change wax on the surface of the carrier. The cement hydration inhibitor is a retarder, and the phase change wax is the shell material. The hydration heat control material provided by this invention can effectively control the total early heat release of concrete and the rate of cement hydration reaction, thereby reducing the maximum temperature rise inside the concrete and decreasing the temperature difference between its inside and outside, thus reducing temperature shrinkage cracks and lowering the risk of concrete cracking. However, the wax coating will be lost after it becomes liquid, and when it turns from liquid to solid, it cannot re-encapsulate the cement hydration inhibitor. The hydration heat inhibitor continues to work in the later stages, resulting in an excessively rapid temperature drop rate, which aggravates temperature shrinkage. At the same time, the effect of this hydration heat control material in reducing hydration heat is limited.

[0005] Therefore, there is an urgent need for an admixture that can effectively reduce the heat of hydration, match the temperature history of concrete, effectively reduce temperature drop shrinkage, and at the same time not affect the strength of concrete and the demolding time, so as to solve the problem of cracking caused by concrete shrinkage. Summary of the Invention

[0006] To address the shortcomings of the existing technology, one objective of this invention is to provide a temperature-controlled shrinkage-compensating admixture for concrete. This admixture can regulate the heat of hydration according to the concrete temperature history, effectively reducing the concrete temperature peak and temperature drop shrinkage, while not affecting the early strength of the concrete.

[0007] To achieve the above objectives, the specific technical solution of the present invention is as follows:

[0008] A temperature-controlled shrinkage compensating admixture for concrete comprises the following components in the indicated mass percentages: 52%–70% expansion component, 8%–13% modifier, 10%–15% temperature-sensitive controlled-release component, and 10%–20% water-retaining component.

[0009] The modifiers include aluminum phosphate and / or aluminum titanate;

[0010] The thermosensitive controlled-release component includes a hydration heat-inhibiting component and a thermosensitive polymer coated on the surface of the hydration heat-inhibiting component. The thermosensitive polymer is polymerized from N-isopropylacrylamide and N,N-dimethylacrylamide.

[0011] The temperature-sensitive controlled-release component of this invention can regulate the heat of hydration according to the temperature history of concrete, so that the inhibition effect of the heat of hydration matches the temperature history of concrete, thereby effectively regulating the heat of hydration, reducing temperature drop shrinkage, and not affecting the early strength of concrete. More importantly, the temperature-sensitive polymer of this invention can effectively enhance the temperature suppression effect of the heat of hydration inhibition component, so that the temperature-sensitive controlled-release component can significantly reduce the temperature peak of concrete. The specific principle is as follows: This invention encapsulates the surface of the heat of hydration inhibition component with a temperature-sensitive polymer, forming a core-shell structure with the heat of hydration inhibition component in the center and the temperature-sensitive polymer in the outer layer. The temperature-sensitive polymer realizes the "on / off" controlled-release effect of the heat of hydration inhibition component according to the temperature stimulus response. When admixtures are added to concrete, when the ambient temperature is above the LCST (Limited Time to Set) level, the temperature-sensitive polymer shrinks, causing the pores of the coating layer to enlarge and thus releasing the encapsulated heat-inhibiting components. This prevents the heat-inhibiting components from reacting prematurely, reducing heat release during the plastic stage and affecting setting time and early strength. When the ambient temperature is below the LCST level, the temperature-sensitive polymer swells and re-encapsulates the heat-inhibiting components, thus stopping their release. This ensures that the heat-inhibiting components will no longer be released after the temperature drops to the LCST level, effectively reducing the rate of temperature drop and further reducing temperature shrinkage.

[0012] The expansion component of this invention provides micro-expansion for concrete, compensating for shrinkage at various stages; the modifier can reduce the coefficient of thermal expansion of concrete, thereby reducing the amount of shrinkage of concrete when the internal temperature decreases; the water-retaining component provides internal curing for concrete on the one hand, and provides moisture for the swelling of the temperature-sensitive polymer above LCST on the other hand, promoting the shut-off effect of the temperature-sensitive controlled-release component.

[0013] The admixture of the present invention effectively reduces concrete shrinkage and significantly reduces the generation of cracks by means of expansion components to compensate for shrinkage, modifiers and temperature-sensitive controlled-release components to reduce temperature-induced shrinkage, and water-retaining components to promote the shut-off effect of temperature-sensitive controlled-release components.

[0014] Preferably, the lower critical phase transition temperature of the thermosensitive polymer is 40-50°C. When the temperature is higher than the lower critical phase transition temperature, the thermosensitive polymer shrinks and releases the heat of hydration inhibitory component. When the temperature is lower than the lower critical phase transition temperature, the thermosensitive polymer swells and encapsulates the heat of hydration inhibitory component.

[0015] Preferably, the mass ratio of the hydration heat-inhibiting component to the temperature-sensitive polymer is (3-6):1.

[0016] Preferably, the preparation method of the temperature-sensitive controlled-release component is as follows: the hydration heat-inhibiting component and the temperature-sensitive polymer are dispersed in an ethanol aqueous solution, stirred for 2-3 days, ultrasonically dispersed, centrifuged, and vacuum dried to obtain the temperature-sensitive controlled-release component.

[0017] Preferably, the molar ratio of N-isopropylacrylamide to N,N-dimethylacrylamide is (4-7):1.

[0018] Preferably, the specific surface area of ​​the temperature-sensitive controlled-release component is 200–500 m². 2 / kg.

[0019] Preferably, the hydration heat-inhibiting component is a starch derivative; the swelling component includes at least one of calcium oxide, magnesium oxide, and calcium sulfoaluminate.

[0020] Preferably, the water-retaining component includes at least one of polyacrylamide, carboxymethyl cellulose, bentonite, and zeolite powder.

[0021] Another object of the present invention is to provide the application of the temperature-controlled shrinkage compensating admixture in concrete, wherein the dosage of the temperature-controlled shrinkage compensating admixture is 8% to 12% of the mass of the cementitious material.

[0022] Compared with the prior art, the advantages of the present invention are:

[0023] (1) This invention utilizes the reversible shrinkage and swelling of a thermosensitive polymer. On the one hand, the thermosensitive polymer shrinks and releases the heat of hydration inhibitor when the temperature is above the LCST, ensuring that the heat of hydration inhibitor only begins to react above the LCST, avoiding premature reaction that reduces heat release during the plastic stage and affects setting time and early strength. On the other hand, the thermosensitive polymer swells and re-wraps the heat of hydration inhibitor when the temperature is below the LCST, ensuring that the heat of hydration inhibitor no longer releases after the temperature drops to the LCST, reducing the rate of temperature drop and further reducing temperature drop shrinkage. Thus, the thermosensitive controlled-release component of this invention can regulate the heat of hydration according to the concrete temperature history, matching the heat of hydration inhibition effect with the concrete temperature history, thereby effectively regulating the heat of hydration, reducing temperature drop shrinkage, and not affecting the early strength of the concrete. In addition, the thermosensitive polymer of this invention can effectively enhance the temperature suppression effect of the heat of hydration inhibitor, enabling the thermosensitive controlled-release component to significantly reduce the concrete temperature peak.

[0024] (2) The admixture of the present invention effectively reduces concrete shrinkage and significantly reduces the generation of cracks by means of expansion component to compensate shrinkage, modifier and temperature-sensitive controlled-release component to reduce temperature shrinkage, and water-retaining component to promote the shut-off effect of temperature-sensitive controlled-release component. Attached Figure Description

[0025] Figure 1 This is a temperature curve of the concrete core. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The present invention provides a temperature-controlled shrinkage-compensating admixture for concrete, comprising the following components in the indicated mass percentages: 52%–70% expansion component, 8%–13% modifier, 10%–15% temperature-sensitive controlled-release component, and 10%–20% water-retaining component.

[0028] The modifiers include aluminum phosphate and / or aluminum titanate;

[0029] The thermosensitive controlled-release component includes a hydration heat-inhibiting component and a thermosensitive polymer coated on the surface of the hydration heat-inhibiting component. The thermosensitive polymer is polymerized from N-isopropylacrylamide and N,N-dimethylacrylamide.

[0030] The preparation method of the temperature-controlled shrinkage-compensating admixture for concrete of the present invention is as follows: the expansion component, the modifier, the temperature-sensitive controlled-release component and the water-retaining component are added to a dry mixer and stirred evenly to obtain the temperature-controlled shrinkage-compensating admixture.

[0031] As an optional embodiment, the mass ratio of the heat-inhibiting hydration component to the thermosensitive polymer is (3-6):1; the heat-inhibiting hydration component includes at least one of pregelatinized starch, resistant dextrin, β-cyclodextrin, maltodextrin, or yellow dextrin; the swelling component includes at least one of calcium oxide, magnesium oxide, and calcium sulfoaluminate; and the water-retaining component includes at least one of polyacrylamide, carboxymethyl cellulose, bentonite, and zeolite powder.

[0032] In the following examples and comparative examples, the preparation method of the temperature-sensitive polymer is as follows:

[0033] N-Isopropylacrylamide and N,N-dimethylacrylamide (total amount 100 mmol) in different molar ratios were dissolved in anhydrous methanol. Then, 0.5 mmol of azobisisobutyronitrile (AIB) initiator and 1 mmol of mercaptoethylamine hydrochloride (Methylamine) capping agent were added to the solution. Free radical polymerization was carried out at 50–70 °C under a nitrogen atmosphere for 12–20 hours. After the reaction, the reaction solution was purified by precipitation with diethyl ether to remove residual monomers and other impurities. The sample was then vacuum dried at room temperature to constant weight to obtain a white powder, which is the thermosensitive polymer. Specifically, the free radical polymerization reaction temperature can be 60 °C for 16 hours.

[0034] The LCST of the prepared temperature-sensitive polymer was measured by a UV / VIS spectrophotometer. Since the change in transmittance is a function of temperature, the LCST of a polymer hydrogel or solution of a specific concentration is defined as the temperature at which the transmittance of the test sample drops to half of the initial value.

[0035] The polymer obtained by copolymerizing N-isopropylacrylamide and N,N-dimethylacrylamide contains both hydrophilic and hydrophobic groups. The interaction between these two groups causes the polymer to undergo a volume phase transition at a certain temperature, exhibiting thermosensitive characteristics. This temperature is called the lower critical phase transition temperature (LCST) of the polymer. By adjusting the ratio of N-isopropylacrylamide to N,N-dimethylacrylamide, the hydrophilic and hydrophobic components in the polymer backbone can be adjusted, and the LCST can be varied. The polymer swells below the LCST and shrinks above the LCST.

[0036] Example 1

[0037] This embodiment provides a temperature-controlled shrinkage-compensating admixture for concrete, comprising the following components by mass percentage: 60% magnesium oxide expanding agent, 10% aluminum phosphate, 15% temperature-sensitive controlled-release component, and 15% water-retaining component.

[0038] The preparation method of the temperature-sensitive controlled-release component is as follows:

[0039] Pregelatinized starch and thermosensitive polymer were dispersed in an aqueous ethanol solution at a mass ratio of 4:1 and stirred for 2.5 days to allow the thermosensitive polymer to coat the surface of the pregelatinized starch. Then, water was added for dilution, ultrasonic dispersion was performed, centrifugation was carried out, the upper liquid was discarded, the lower precipitate was retained, and the thermosensitive controlled-release component was obtained after vacuum drying.

[0040] The thermosensitive polymer is polymerized from N-isopropylacrylamide and N,N-dimethylacrylamide in a molar ratio of 7:1, and the low critical phase transition temperature of the thermosensitive polymer is 40℃.

[0041] The water-retaining component is a mixture of polyacrylamide and carboxymethyl cellulose in a mass ratio of 2:1.

[0042] The preparation method of the admixture in this embodiment is as follows: magnesium oxide expansion agent, aluminum phosphate, temperature-sensitive controlled-release component and water-retaining component are added to a dry mixer and stirred evenly to obtain a temperature-controlled shrinkage compensation admixture.

[0043] Example 2

[0044] The temperature-controlled shrinkage compensation additive in this embodiment is basically the same as that in Example 1, except that the temperature-sensitive polymer is polymerized from N-isopropylacrylamide and N,N-dimethylacrylamide in a molar ratio of 4:1, and the low critical phase transition temperature of the temperature-sensitive polymer is 50°C.

[0045] Example 3

[0046] The temperature-controlled shrinkage compensation additive in this embodiment is basically the same as that in Example 1, except that the additive in this embodiment includes the following components by mass percentage: 60% magnesium oxide expanding agent, 10% aluminum titanate, 15% temperature-sensitive controlled-release component, and 15% water-retaining component.

[0047] The preparation method of the temperature-sensitive controlled-release component is as follows:

[0048] β-cyclodextrin and thermosensitive polymer were dispersed in an aqueous ethanol solution at a mass ratio of 6:1 and stirred for 3 days to allow the thermosensitive polymer to coat the surface of β-cyclodextrin. Then, water was added for dilution, ultrasonic dispersion was performed, centrifugation was carried out, the upper liquid was discarded, the lower precipitate was retained, and the thermosensitive controlled-release component was obtained after vacuum drying.

[0049] The water-retaining component is a mixture of bentonite and zeolite powder in a mass ratio of 1:1.

[0050] Example 4

[0051] The temperature-controlled shrinkage compensation additive in this embodiment is basically the same as that in Example 1, except that the additive in this embodiment includes the following components by mass percentage: 70% magnesium oxide expanding agent, 10% aluminum titanate, 10% temperature-sensitive controlled-release component, and 10% water-retaining component.

[0052] Comparative Example 1

[0053] The additives in this comparative example include the following components by mass percentage: 75% magnesium oxide expanding agent, 10% aluminum phosphate, and 15% water-retaining component; the water-retaining component is a compound of polyacrylamide and carboxymethyl cellulose in a mass ratio of 2:1.

[0054] Compared to Example 1, the additive in this comparative example does not contain a temperature-sensitive controlled-release component.

[0055] Comparative Example 2

[0056] The additives in this comparative example include the following components by mass percentage: 60% magnesium oxide expanding agent, 10% aluminum phosphate, 15% pregelatinized starch, and 15% water-retaining component; the water-retaining component is a compound of polyacrylamide and carboxymethyl cellulose in a mass ratio of 2:1.

[0057] Compared to Example 1, the pregelatinized starch in this comparative example was not coated with a temperature-sensitive polymer.

[0058] Comparative Example 3

[0059] The additives in this comparative example are basically the same as those in Example 1, except that the additives in this comparative example include the following components by mass percentage: 60% stone powder, 10% aluminum phosphate, 15% temperature-sensitive controlled-release component, and 15% water-retaining component.

[0060] Compared to Example 1, this comparative example uses stone powder instead of magnesium oxide expander.

[0061] Comparative Example 4

[0062] The additives in this comparative example are basically the same as those in Example 1, except that the additives in this comparative example include the following components by mass percentage: 70% magnesium oxide expanding agent, 15% temperature-sensitive controlled-release component, and 15% water-retaining component.

[0063] Compared to Example 1, the additive in this comparative example does not contain aluminum phosphate.

[0064] Comparative Example 5

[0065] The additives in this comparative example are basically the same as those in Example 1, except that the additives in this comparative example include the following components by mass percentage: 75% magnesium oxide expander, 10% aluminum phosphate, and 15% thermosensitive controlled-release component.

[0066] Compared to Example 1, the additive in this comparative example does not contain water-retaining components.

[0067] Comparative Example 6

[0068] The additives in this comparative example are basically the same as those in Example 1. The difference is that this comparative example uses phase change wax instead of temperature-sensitive polymer. The phase change wax is coated on the surface of pregelatinized starch. The preparation method of the temperature-sensitive controlled-release component is as follows: paraffin wax with a phase change temperature of 40°C is sprayed onto the surface of pregelatinized starch at a mass fraction ratio of 1:4 at 60°C by spray drying. After cooling, the temperature-sensitive controlled-release component is obtained.

[0069] Test case

[0070] The temperature-controlled shrinkage compensating admixtures of the examples and comparative examples were incorporated into the concrete, and C40 grade concrete was prepared according to the standard JGJ55-2011 "Specification for Mix Proportion Design of Ordinary Concrete". The concrete mix proportions are shown in Table 1.

[0071] Table 1. Concrete mix proportions (kg / m³) 3 )

[0072] Group water cement Mineral powder fly ash river sand gravel Water reducing agent admixtures Example 165 285 85 17 740 1040 6.8 43 Blank group 165 285 85 60 740 1040 6.7 /

[0073] The cement used is commercially available ordinary Portland cement with a strength grade of P·O 42.5; the river sand has a mud content of 2.2%, a mud lump content of 0.21%, and a moisture content of 5%; the crushed stone uses a continuous gradation of 5-31.5mm, has a mud content of 0.57%, and a mud lump content of less than 0.1%; the water-reducing agent is a polycarboxylate water-reducing agent from Wuhan Sanyuan Special Building Materials Co., Ltd., with a water reduction rate of 15%.

[0074] The workability of concrete was tested according to GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures"; the compressive strength of concrete was tested according to GB / T 50081-2019 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete"; and the 7-day thermal expansion coefficient of concrete was tested according to the industry standard DL / T 5150-2017 "Test Procedure for Hydraulic Concrete". The test results are shown in Table 2.

[0075] Table 2 Workability and compressive strength of concrete

[0076]

[0077] As can be seen from the data in Table 2, compared with the control group, the compressive strength of concrete with the admixture of this invention is basically the same, without significant weakening, indicating that the temperature-controlled shrinkage-compensating admixture of this invention has virtually no effect on the compressive strength of concrete. However, compared with the control group, the compressive strength of Comparative Example 2 at 3d, 7d, and 28d all decreased to varying degrees, especially at 3d, where the decrease was the largest. This indicates that the hydration heat-inhibiting component without the temperature-sensitive polymer coating reduces the early strength of concrete and delays the demolding time.

[0078] Regarding the 7-day thermal expansion coefficient of concrete, compared with the blank group, the 7-day thermal expansion coefficient of concrete significantly decreased after incorporating the admixture of the present invention, indicating that the temperature-controlled shrinkage-compensating admixture of the present invention has a significant effect on reducing the 7-day thermal expansion coefficient of concrete; by comparing Example 1 and Comparative Example 4, it can be found that aluminum phosphate has a significant effect on reducing the 7-day thermal expansion coefficient of concrete.

[0079] Concrete specimens with a molding size of 100mm×100mm×300mm were tested in water at 20℃ according to GB / T 23439-2017 "Concrete Expansion Agent". The test results are shown in Table 3.

[0080] Table 3 Restricted Expansion Rate of Concrete / 10 -6

[0081] project 3d 7d 28d 56d Blank group -30 -50 -120 -118 Example 1 36 79 162 193 Example 2 34 77 159 190 Example 3 32 75 156 187 Example 4 45 94 175 211 Comparative Example 1 40 93 171 205 Comparative Example 2 28 70 154 187 Comparative Example 3 -25 -40 -100 -102 Comparative Example 4 31 72 144 168 Comparative Example 5 44 85 176 213 Comparative Example 6 33 75 157 185

[0082] As can be seen from the data in Table 2, the restricted expansion rate of the concrete in the blank group was negative, while the restricted expansion rate of the concrete after adding the admixture of the present invention was positive, indicating that the temperature-controlled shrinkage-compensating admixture of the present invention can play a micro-expansion role and compensate for the shrinkage of concrete. By comparing Example 1 and Comparative Example 3, it can be seen that the restricted expansion rate of the concrete in Comparative Example 3 was negative, indicating that the expansion component in the admixture played a shrinkage-compensating role.

[0083] The concrete mixture was poured into a mold with dimensions of 500mm×500mm×1000mm. The core temperature of the concrete was tested according to GB / T 51028-2015 "Technical Specification for Temperature Measurement and Control of Mass Concrete". The test results are shown in Table 4. Figure 1 As shown.

[0084] Table 4. Core temperature and cooling rate of concrete

[0085]

[0086]

[0087] Note: The temperature drop rate in the table represents the ratio of the temperature decrease from the highest temperature to 35℃ during the process of reducing the temperature at the core of the concrete to the time taken, i.e., (T... max -T 35℃ ) / t.

[0088] From Table 4 and Figure 1The data shows that, compared with the control group, the addition of the admixture of this invention significantly reduced the peak concrete temperature, slightly shortened or remained essentially unchanged the peak temperature time, and significantly reduced the temperature drop rate. This indicates that the temperature-controlled shrinkage-compensating admixture of this invention can significantly reduce the peak concrete temperature without delaying the peak temperature time, and can also significantly reduce the temperature drop rate, further reducing temperature shrinkage. Further comparison of Examples 1 and 2 reveals that when the molar ratio of N-isopropylacrylamide to N,N-dimethylacrylamide in the temperature-sensitive polymer is 7:1, the admixture has the best effect in reducing the peak concrete temperature.

[0089] Compared to Example 1, Comparative Example 1, which did not contain a temperature-sensitive controlled-release component, showed a significant increase in both the peak temperature and the rate of temperature drop in concrete, indicating that the temperature-sensitive controlled-release component played a key role in reducing the temperature peak. In Comparative Example 2, the surface of the heat-inhibiting component was not coated with a temperature-sensitive polymer, resulting in a significantly prolonged peak temperature time in concrete. This demonstrates that coating the surface of the heat-inhibiting component with a temperature-sensitive polymer effectively prevents premature reaction and reduced heat release during the plastic stage, delaying the peak temperature and thus avoiding problems such as low concrete strength and delayed formwork removal. Furthermore, comparing the peak temperatures of Example 1 and Comparative Example 2 reveals that coating the surface of the heat-inhibiting component with a temperature-sensitive polymer significantly improves its temperature-suppressing effect and reduces the peak temperature. This indicates that coating the surface of the heat-inhibiting component with a temperature-sensitive polymer not only solves the problem of delayed peak temperature time but also significantly enhances its temperature-suppressing effect, demonstrating a good synergistic effect. Comparative Example 5, which did not contain a water-retaining component, showed a significantly increased rate of temperature drop. This indicates that the water-retaining component helps provide swelling water for the temperature-sensitive polymer below the LCST, ensuring that the polymer remains in a "closed" state below the LCST and no longer releases the heat of hydration inhibitor. Comparative Example 6, which replaced the temperature-sensitive polymer with a phase change wax, showed a significant increase in both the peak temperature and the rate of temperature drop. This indicates that compared to the phase change wax, the temperature-sensitive polymer helps reduce the rate of temperature drop during the cooling phase, thereby reducing concrete thermal shrinkage, and can synergistically enhance the inhibitory effect of the heat of hydration inhibitor.

[0090] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A temperature controlled compensating shrinkage admixture for concrete, characterized by, It includes the following components by weight percentage: swelling component 52%~70%, modifier 8%~13%, thermosensitive controlled-release component 10%~15%, and water-retaining component 10%~20%; The modifiers include aluminum phosphate and / or aluminum titanate; The thermosensitive controlled-release component includes a hydration heat-inhibiting component and a thermosensitive polymer coated on the surface of the hydration heat-inhibiting component. The thermosensitive polymer is polymerized from N-isopropylacrylamide and N,N-dimethylacrylamide. The mass ratio of the hydration heat-inhibiting component to the thermosensitive polymer is (3~6):

1. The preparation method of the thermosensitive controlled-release component is as follows: the hydration heat inhibition component and the thermosensitive polymer are dispersed in an ethanol aqueous solution, stirred for 2-3 days, ultrasonically dispersed, centrifuged, and vacuum dried to obtain the thermosensitive controlled-release component; The hydration heat-inhibiting component is a starch derivative; the swelling component includes at least one of calcium oxide, magnesium oxide, and calcium sulfoaluminate.

2. The temperature-controlled shrinkage compensating admixture for concrete according to claim 1, characterized in that, The low critical phase transition temperature of the thermosensitive polymer is 40~50℃. When the temperature is higher than the low critical phase transition temperature, the thermosensitive polymer shrinks and releases the heat of hydration inhibitory component. When the temperature is lower than the low critical phase transition temperature, the thermosensitive polymer swells and encapsulates the heat of hydration inhibitory component.

3. The temperature-controlled shrinkage compensating admixture for concrete according to claim 1, characterized in that, The molar ratio of N-isopropylacrylamide to N,N-dimethylacrylamide is (4~7):

1.

4. A temperature-controlled shrinkage compensating admixture for concrete according to claim 1, characterized in that, The specific surface area of the temperature-sensitive controlled-release component is 200-500 m 2 / kg.

5. A temperature-controlled shrinkage compensating admixture for concrete according to claim 1, characterized in that, The water-retaining component includes at least one of polyacrylamide, carboxymethyl cellulose, bentonite, and zeolite powder.

6. The application of the temperature-controlled shrinkage-compensating admixture according to any one of claims 1 to 5 in concrete, characterized in that, The dosage of the temperature-controlled shrinkage compensation admixture is 8% to 12% of the mass of the cementitious material.

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