Temperature-sensitive concrete anti-freezing microspheres and anti-freezing concrete and preparation method thereof

Abstract

The present application relates to a kind of temperature-sensitive concrete anti-freezing microspheres and anti-freezing concrete and its preparation method, the phase transition point temperature of the microsphere is 25-35 ℃;The microsphere includes the following weight parts components: N-isopropyl acrylamide monomer 4-6 parts, tertiary butyl acrylate monomer 0.5-2.0 parts, crosslinking agent 0.05-0.20 parts, water 45-55 parts, emulsifier 3-5 parts, solvent 120-200 parts and initiator 0.3-0.4 parts.Compared with prior art, the present application relieves the expansion pressure and osmotic pressure generated by water freezing in freeze-thaw process, and can respond to temperature in time, water absorption ratio and phase transition point temperature can be adjusted, significantly improve the freeze-thaw damage resistance of concrete, meet the anti-freezing demand of concrete in various freeze-thaw environments.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of civil engineering and construction materials, and relates to a temperature-sensitive concrete anti-freezing microsphere and an anti-freezing concrete and a preparation method thereof. BACKGROUND

[0002] Freeze-thaw damage is one of the main reasons for the damage and failure of concrete structures in cold regions, and the main damage forms are frost heaving cracking and freeze-thaw spalling of concrete, which seriously affects the safety and durability of building structures. The common method for improving the frost resistance of concrete in engineering is to add air entraining agents to introduce a proper amount of fine and closed air bubbles to alleviate the static water pressure and osmotic pressure generated in the internal of concrete by freeze-thaw cycles, so as to inhibit the occurrence and development of freeze-thaw damage in the internal of concrete. The common air entraining agent is essentially a kind of surfactant, which forms and stabilizes a large number of micro air bubbles in the mixing process of concrete, so that air pores exist in the internal of hardened concrete. However, many factors such as the composition of the mixture, the water-cement ratio, the temperature, the mixing time and even the atmospheric pressure can affect the air entraining effect such as the number, size and distribution of air bubbles, so that the frost resistance of concrete shows obvious differences, which brings great difficulty to the engineering quality control in extreme environments.

[0003] In order to solve the above problems, a water-absorbing polymer anti-freezing microsphere has appeared in recent years. The anti-freezing microsphere is distributed in the fresh mixture to absorb water and swell, and forms a cavity in the hardened cement matrix by losing water and shrinking, so as to alleviate the volume expansion pressure and osmotic pressure generated by water freezing in the freeze-thaw cycle. However, most of the water-absorbing polymers used at present do not have the response ability to temperature. The N-isopropyl acrylamide temperature-sensitive hydrogel can respond to the surrounding temperature, but its phase transition point temperature is relatively high, and its adaptability to low temperature environment is insufficient. Moreover, the temperature-sensitive hydrogel used at present is in the form of large particles, which will have a great negative impact on the strength of concrete after being mixed into the concrete. Therefore, how to prepare a kind of microsphere which can respond to the environmental temperature, and how to design and control the phase transition point temperature and particle size of the microsphere to improve the freeze-thaw damage resistance of concrete, will be extremely crucial for the application of concrete in plain high-cold regions and low-pressure high-altitude environments with complex environmental conditions.

[0004] Patent CN106316192A discloses the application of a temperature-sensitive hydrogel in improving the freeze-thaw resistance of concrete. The raw materials for preparing the concrete include temperature-sensitive hydrogel, cement, aggregate and water. The patent mixes the temperature-sensitive hydrogel into the concrete, which can significantly reduce the mass loss of the concrete and improve the damage resistance of the concrete without affecting the mechanical properties of the concrete. However, the phase transition point temperature of the hydrogel used in the patent is relatively high, which limits its adaptability to low temperature environment. In addition, the hydrogel used in the patent does not have a spherical structure, and its negative impact on the strength of concrete still has room for improvement. SUMMARY

[0005] The present application aims to provide a temperature-sensitive concrete anti-freezing microsphere and an anti-freezing concrete and a preparation method thereof to overcome at least one of the defects of the prior art.

[0006] The object of the present application can be achieved by the following technical solutions.

[0007] One of the technical solutions of the present application is to provide a temperature-sensitive concrete anti-freezing microsphere, wherein the phase transition point temperature of the microsphere is 25-35 ℃.

[0008] The microsphere comprises the following components by weight: 4-6 parts of N-isopropyl acrylamide monomer, 0.5-2.0 parts of tert-butyl acrylate monomer, 0.05-0.20 parts of crosslinking agent, 45-55 parts of water, 3-5 parts of emulsifier, 120-200 parts of solvent and 0.3-0.4 parts of initiator.

[0009] Further, the crosslinking agent comprises N,N'-methylene bisacrylamide, octadecyl methacrylate, ethylene glycol dimethacrylate or diethylene glycol dimethacrylate.

[0010] Further, the emulsifier comprises the following components by weight: 1.5-2.5 parts of Span80 and 1.5-2.5 parts of Tween80, and the solvent comprises n-hexane, cyclohexane or heptane.

[0011] Further, the initiator comprises ammonium persulfate, potassium persulfate, benzoyl peroxide or azobisisobutyronitrile.

[0012] One of the technical solutions of the present application is to provide a preparation method of a temperature-sensitive concrete anti-freezing microsphere, which comprises the following steps.

[0013] (1.1) Dissolve the N-isopropyl acrylamide monomer, the tert-butyl acrylate monomer and the crosslinking agent in water, seal and protect by introducing inert gas, mix until the monomers are completely dissolved, and obtain a dispersion phase solution;

[0014] (1.2) Dissolve the emulsifier in the solvent, seal and protect by introducing inert gas, mix, and obtain a continuous phase solution;

[0015] (1.3) Add the dispersion phase solution to the continuous phase solution, seal and protect by introducing inert gas, mix at constant temperature, add the initiator, keep the constant temperature condition, and react to obtain the temperature-sensitive concrete anti-freezing microsphere.

[0016] As a preferred technical solution, the inert gas in steps (1.1), (1.2) and (1.3) includes nitrogen or helium.

[0017] Furthermore, in step (1.1), the mixing temperature is room temperature and the time is 10-20 min.

[0018] As a preferred technical solution, the mixing or reaction stirring speed is 400-700 r / min.

[0019] Furthermore, in step (1.2), the mixing temperature is room temperature and the time is 5-15 min.

[0020] Furthermore, in step (1.3), the mixing temperature is 60-80 ℃ and the time is 20-60 min;

[0021] The reaction temperature is 60-80 ℃, and the time is 4-12 h.

[0022] One of the technical solutions of the present invention is to provide a frost-resistant concrete, wherein the frost-resistant concrete incorporates the aforementioned temperature-sensitive concrete frost-resistant microspheres, and the frost-resistant concrete comprises the following components by weight: 0.9-3.6 parts of temperature-sensitive concrete frost-resistant microspheres, 1450-1500 parts of aggregate, 420-480 parts of cement, and 120-140 parts of water.

[0023] As a preferred technical solution, the mass content of the temperature-sensitive concrete antifreeze microspheres is 0.2-0.8% of the cement mass.

[0024] As a preferred technical solution, the cement includes 42.5 silicate cement, 42.5R silicate cement, 42.5 ordinary silicate cement or 42.5R ordinary silicate cement, with a standard consistency of 25-30% and qualified stability.

[0025] As a preferred technical solution, the aggregate comprises the following components by weight: 350-380 parts of fine aggregate and 1100-1120 parts of coarse aggregate.

[0026] As a preferred technical solution, the fine aggregate includes natural sand or manufactured sand, with a fineness modulus of 3.7-2.0, a mud content of 2.0-3.0%, and an apparent density of 2600-2700 kg / m³. 3 The bulk density is 1400-1450 kg / m³ 3 .

[0027] As a preferred technical solution, the coarse aggregate comprises gravel or crushed stone with a particle size distribution of 10-31.5 mm, a crushing index of 7-8%, and an apparent density of 2650-2700 kg / m³. 3 The mud content is 0.2-1.0%.

[0028] One of the technical solutions of the present application is to provide a preparation method of anti-freezing concrete, which comprises the following steps:

[0029] (2.1) mixing the temperature-sensitive concrete anti-freezing microspheres, aggregates and cement to be uniform;

[0030] (2.2) adding water to the mixture and mixing to be uniform to obtain the anti-freezing concrete.

[0031] As a preferred technical solution, the mixing time in step (2.1) is 10-30 min.

[0032] As a preferred technical solution, the mixing time in step (2.2) is 4-5 min.

[0033] The temperature-sensitive anti-freezing microspheres introduced into the concrete system by the present application are a kind of polymers with high water absorption capacity, which can form pores in situ after being mixed into the cement matrix, relieve the expansion pressure and osmotic pressure generated by water freezing during the freeze-thaw process, and respond to temperature in time, fully exert the advantages of water gel water absorption ratio and adjustable pore size (by adjusting the synthesis process parameters of the microspheres and designing the particle size of the microspheres), thus significantly improving the freeze-thaw damage resistance of the concrete.

[0034] The present application introduces temperature-sensitive anti-freezing microspheres into the concrete system to release water during the cement hydration process, and then form closed pores in situ, which can relieve the expansion pressure and osmotic pressure generated by water freezing during the freeze-thaw cycle, and improve the freeze-thaw damage resistance of the concrete. Under low temperature conditions, the temperature-sensitive anti-freezing microspheres can absorb water in the cement matrix, reduce the content of freezable free water; when the temperature rises, they can quickly release water, promote cement hydration, refine the pore structure, enhance the matrix strength, and synergistically improve the frost resistance of the concrete. By adjusting the proportion of raw materials, the water absorption ratio and phase transition point temperature of the temperature-sensitive anti-freezing microspheres can be designed to meet the frost resistance requirements of the concrete in various freeze-thaw environments.

[0035] Compared with the prior art, the present application has the following beneficial effects:

[0036] (1) The present application uses the volume shrinkage pore-forming of the temperature-sensitive concrete anti-freezing microspheres to relieve the expansion pressure and osmotic pressure generated by water freezing during the freeze-thaw process, improve the frost resistance of the concrete, and the pore-forming process is not affected by environmental pressure and the like, and the pore-forming effect is stable; the temperature-sensitive concrete anti-freezing microspheres used in the present application can respond to temperature in real time, fully exert the advantages of water gel water absorption under low temperature conditions, reduce the content of freezable free water in the cement matrix; under the condition of rising temperature, they can quickly release water, promote cement hydration, refine the pore structure, enhance the matrix strength, and comprehensively improve the durability of the concrete;

[0037] (2) The temperature-sensitive concrete anti-freezing microspheres are mixed in the concrete, and spherical pores can be formed in situ, and the dome effect of the spherical pores can reduce the influence of the microspheres on the mechanical properties of the concrete;

[0038] (3) The temperature-sensitive concrete anti-freezing microspheres have the advantages of strong designability of response temperature, wide application environment, and can be designed according to the structural durability requirements, and stably formed in the concrete, and are not only suitable for high-cold areas in plains, but also have good use effect under complex environmental conditions such as low air pressure and high altitude. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 The figure is the water absorption capacity of the temperature-sensitive concrete anti-freezing microspheres with different phase transition point temperatures under variable temperature conditions in the embodiment of the present application;

[0040] Figure 2 The figure is the mass loss comparison of the concrete in the embodiment and the comparative example;

[0041] Figure 3 The figure is the relative dynamic elastic modulus comparison of the concrete in the embodiment and the comparative example;

[0042] Figure 4 The figure is the compressive strength comparison of the concrete in the embodiment and the comparative example. DETAILED DESCRIPTION

[0043] The present application will be described in detail below in combination with specific embodiments. The present embodiment is implemented on the premise of the technical scheme of the present application, and detailed implementation modes and specific operation processes are given, but the protection scope of the present application is not limited to the following embodiments.

[0044] The equipment used in the following embodiments is conventional equipment in the art unless otherwise specified; the reagents used are commercially available products or prepared by conventional methods in the art unless otherwise specified, and the methods not described in detail in the following embodiments can be realized by conventional experimental methods in the art.

[0045] Example 1:

[0046] An anti-freezing concrete, wherein the mass content of the temperature-sensitive concrete anti-freezing microspheres is 0.2% of the mass of the cement;

[0047] The phase transition point temperature of the temperature-sensitive concrete anti-freezing microspheres is 35 ℃;

[0048] The cement is 42.5R ordinary portland cement, the standard consistency is 28.8%, and the stability is qualified;

[0049] The fine aggregate is natural sand with a fineness modulus of 2.8, a clay content of 2.5%, and an apparent density of 2650 kg / m 3 ; 3 ;

[0050] The coarse aggregate is gravel with a particle size distribution of 10-31.5 mm, a crushing index of 7.5%, an apparent density of 2690 kg / m 3 , and a clay content of 0.5%.

[0051] The preparation method of the anti-freezing concrete is as follows:

[0052] (1) 5 g of N-isopropyl acrylamide monomer, 0.7 g of tert-butyl acrylate monomer and 0.1 g of N,N'-methylenebisacrylamide are dissolved in 50 g of deionized water, nitrogen is introduced for sealing protection, stirring is performed at room temperature at a speed of 400 r / min for 20 min until the monomers are completely dissolved, a dispersed phase solution is obtained; 2 g of Span80 and 2 g of Tween80 are dissolved in 150 g of n-hexane, nitrogen is introduced for sealing protection, stirring is performed at room temperature at a speed of 400 r / min for 10 min, a continuous phase solution is obtained; the dispersed phase solution is added to the continuous phase solution, nitrogen is introduced for sealing protection, stirring is performed at a constant temperature of 70 ℃ at a speed of 400 r / min for 30 min, 0.35 g of ammonium persulfate is added, and reaction is performed at a constant temperature of 70 ℃ and a speed of 400 r / min for 6 h, to obtain temperature-sensitive concrete anti-freezing microspheres;

[0053] (2) 0.9 g of the temperature-sensitive concrete anti-freezing microspheres obtained in step (1), 370 g of fine aggregate, 1110 g of coarse aggregate and 450 g of cement are mixed for 20 min until uniform;

[0054] (3) 135 g of water is added to the mixture obtained in step (2), and stirring is performed for 5 min until uniform, to obtain the anti-freezing concrete.

[0055] Example 2:

[0056] An anti-freezing concrete, wherein the mass content of the temperature-sensitive concrete anti-freezing microspheres is the same as that in example 1.

[0057] The difference lies in that the phase transition point temperature of the temperature-sensitive concrete anti-freezing microspheres is 28 ℃.

[0058] The requirements for cement, fine aggregate and coarse aggregate are the same as those in example 1.

[0059] The method for preparing the anti-freezing concrete is different from the above in that 5 g of N-isopropyl acrylamide monomer, 1.5 g of t-butyl acrylate monomer and 0.1 g of N,N'-methylene bisacrylamide are dissolved in 50 g of deionized water, and the rest of the material dosages and the process are the same as in Example 1.

[0060] Example 3:

[0061] An anti-freezing concrete, wherein the mass content of the temperature-sensitive concrete anti-freezing microspheres is the same as in Example 1.

[0062] The difference is that the phase transition point temperature of the temperature-sensitive concrete anti-freezing microspheres is 25℃.

[0063] The requirements for cement, fine aggregate and coarse aggregate are the same as in Example 1.

[0064] The method for preparing the anti-freezing concrete is different from the above in that 5 g of N-isopropyl acrylamide monomer, 2.0 g of t-butyl acrylate monomer and 0.1 g of N,N'-methylene bisacrylamide are dissolved in 50 g of deionized water, and the rest of the material dosages and the process are the same as in Example 1.

[0065] Example 4:

[0066] An anti-freezing concrete, wherein the difference is that the mass content of the temperature-sensitive concrete anti-freezing microspheres is 0.4% of the mass of the cement.

[0067] The phase transition point temperature of the temperature-sensitive concrete anti-freezing microspheres, and the requirements for cement, fine aggregate and coarse aggregate are the same as in Example 1.

[0068] The method for preparing the anti-freezing concrete is different from the above in that 1.8 g of the temperature-sensitive concrete anti-freezing microspheres obtained in step (1), 370 g of fine aggregate, 1110 g of coarse aggregate and 450 g of cement are mixed for 20 min until uniform, and the rest of the material dosages and the process are the same as in Example 1.

[0069] Example 5:

[0070] An anti-freezing concrete, wherein the difference is that the mass content of the temperature-sensitive concrete anti-freezing microspheres is 0.6% of the mass of the cement.

[0071] The phase transition point temperature of the temperature-sensitive concrete anti-freezing microspheres, and the requirements for cement, fine aggregate and coarse aggregate are the same as in Example 1.

[0072] The preparation method of the anti-freezing concrete is different from the above, wherein 2.7 g of the temperature-sensitive concrete anti-freezing microspheres obtained in step (1), 370 g of fine aggregate, 1110 g of coarse aggregate and 450 g of cement are mixed for 20 min until uniform, and the dosages and procedures of the remaining materials are the same as in example 1.

[0073] Example 6:

[0074] An anti-freezing concrete, wherein the difference is that the mass content of the temperature-sensitive concrete anti-freezing microspheres is 0.8% of the mass of the cement;

[0075] The phase transition point temperature of the temperature-sensitive concrete anti-freezing microspheres, and the requirements for the cement, fine aggregate and coarse aggregate are the same as in example 1.

[0076] The preparation method of the anti-freezing concrete is different from the above, wherein 3.6 g of the temperature-sensitive concrete anti-freezing microspheres obtained in step (1), 370 g of fine aggregate, 1110 g of coarse aggregate and 450 g of cement are mixed for 20 min until uniform, and the dosages and procedures of the remaining materials are the same as in example 1.

[0077] Comparative example:

[0078] A concrete and a preparation method thereof, the specific steps are as follows:

[0079] (1) 370 g of fine aggregate, 1110 g of coarse aggregate and 450 g of cement are mixed for 20 min until uniform;

[0080] (2) 135 g of water is added to the mixture obtained in step (1), and mixed for 5 min until uniform to obtain the concrete.

[0081] After the prepared concrete is standardly maintained for 28 d, a freeze-thaw cycle comparison test is performed, the mass loss rate and the relative dynamic elastic modulus of the concrete are detected after 180 freeze-thaw cycles according to the quick freezing method in GB / T 50082-2009 “Standard for Testing Methods of Long-term Performance and Durability of Ordinary Concrete”, and the mechanical properties of the concrete are detected according to GB / T 50081-2019 “Standard for Testing Methods of Mechanical Properties of Ordinary Concrete”.

[0082] As shown in Figure 1 The phase transition point temperatures of the temperature-sensitive concrete anti-freezing microspheres of the present embodiment are 35 ℃, 28 ℃ and 25 ℃ respectively, when the temperature-sensitive concrete anti-freezing microspheres are below the phase transition point temperature, the water absorption ratio is 70-90 times, and when the temperature-sensitive concrete anti-freezing microspheres are above the phase transition point temperature, the water absorption ratio gradually decreases to 40 times, which indicates that the temperature-sensitive concrete anti-freezing microspheres can absorb more water under low temperature conditions, reduce the content of free water available for freezing in the concrete, and gradually release water during the heating process to promote cement hydration.

[0083] As shown in Figure 2 The quality loss of the concrete of the present embodiment is significantly lower than that of the concrete without the temperature-sensitive concrete anti-freezing microspheres; the quality loss of the concrete decreases as the phase transition temperature of the temperature-sensitive concrete anti-freezing microspheres decreases; the quality loss of the concrete decreases as the content of the temperature-sensitive concrete anti-freezing microspheres increases, which all show that the incorporation of the temperature-sensitive concrete anti-freezing microspheres can significantly reduce the quality loss of the concrete.

[0084] As shown in Figure 3 The relative dynamic elastic modulus of the concrete of the present embodiment is significantly higher than that of the concrete without the temperature-sensitive concrete anti-freezing microspheres; the relative dynamic elastic modulus of the concrete increases as the phase transition temperature of the temperature-sensitive concrete anti-freezing microspheres decreases; the relative dynamic elastic modulus of the concrete slightly increases as the content of the temperature-sensitive concrete anti-freezing microspheres increases, which all show that the incorporation of the temperature-sensitive concrete anti-freezing microspheres can significantly improve the relative dynamic elastic modulus of the concrete.

[0085] As shown in Figure 4 The incorporation of the temperature-sensitive concrete anti-freezing microspheres has little effect on the compressive performance of the concrete.

[0086] Therefore, the performance of the concrete of the present embodiment incorporating the temperature-sensitive concrete anti-freezing microspheres against freeze-thaw damage is significantly better than that of the concrete without the temperature-sensitive concrete anti-freezing microspheres, and the freeze-thaw damage resistance of the concrete is further improved as the phase transition temperature of the temperature-sensitive concrete anti-freezing microspheres decreases and the content of the temperature-sensitive concrete anti-freezing microspheres increases.

[0087] The above description of the embodiments is for the purpose of enabling a person of ordinary skill in the art to understand and use the present application. Those skilled in the art can easily make various modifications to the embodiments and apply the general principles described herein to other embodiments without inventive labor. Therefore, the present application is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present application without departing from the scope of the present application shall be considered within the scope of the present application.

Claims

1. A type of frost-resistant concrete, characterized in that, The antifreeze concrete incorporates thermosensitive concrete antifreeze microspheres, and the antifreeze concrete comprises the following components by weight: 0.9-3.6 parts thermosensitive concrete antifreeze microspheres, 1450-1500 parts aggregate, 420-480 parts cement, and 120-140 parts water; The phase transition temperature of the microspheres is 25-35 ℃; The microspheres comprise the following components by weight: 4-6 parts of N-isopropylacrylamide monomer, 0.5-2.0 parts of tert-butyl acrylate monomer, 0.05-0.20 parts of crosslinking agent, 45-55 parts of water, 3-5 parts of emulsifier, 120-200 parts of solvent, and 0.3-0.4 parts of initiator; The emulsifier comprises the following components in parts by weight: 1.5-2.5 parts of Span80 and 1.5-2.5 parts of Tween80, and the solvent comprises n-hexane, cyclohexane, or heptane; The method for preparing the temperature-sensitive concrete antifreeze microspheres includes the following steps: (1.1) Dissolve N-isopropylacrylamide monomer, tert-butyl acrylate monomer and crosslinking agent in water, mix them to obtain a dispersed phase solution; (1.2) Dissolve the emulsifier in the solvent and mix to obtain a continuous phase solution; (1.3) The dispersed phase solution is added to the continuous phase solution, mixed at a constant temperature, an initiator is added, and the reaction is carried out under constant temperature conditions to obtain thermosensitive concrete antifreeze microspheres; In step (1.1), the mixing temperature is room temperature and the time is 10-20 min; In step (1.2), the mixing temperature is room temperature and the time is 5-15 min; In step (1.3), the mixing temperature is 60-80 ℃ and the time is 20-60 min; The reaction temperature is 60-80 ℃, and the time is 4-12 h.

2. The antifreeze concrete according to claim 1, characterized in that, The crosslinking agent includes N,N'-methylenebisacrylamide, octadecyl methacrylate, ethylene glycol dimethacrylate, or diethylene glycol dimethacrylate.

3. The antifreeze concrete according to claim 1, characterized in that, The initiator includes ammonium persulfate, potassium persulfate, benzoyl peroxide, or azobisisobutyronitrile.

4. A method for preparing frost-resistant concrete as described in any one of claims 1 to 3, characterized in that, The method includes the following steps: (2.1) Mix the temperature-sensitive concrete antifreeze microspheres, aggregates and cement; (2.2) Add water to the mixture and mix to obtain antifreeze concrete.

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