High-freezing-resistance super-hydrophobic rubber cement mortar and preparation method thereof

Abstract

The invention discloses high-freezing-resistance super-hydrophobic rubber cement mortar and a preparation method thereof, and belongs to the technical field of building materials.The high-freezing-resistance super-hydrophobic rubber cement mortar is prepared from, by weight, 176-220 parts of water, 400 parts of cement, 540-630 parts of sand, 26-30 parts of rubber particles, 40 parts of silica fume and 60-66 parts of polydimethylsiloxane. Under the condition of not adding other substances, through the synergistic effect of the rubber particles, the polydimethylsiloxane and the silica fume, the freezing resistance and super-hydrophobicity of the cement mortar can be greatly improved, and the healthy service life of buildings in cold regions is remarkably prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and particularly relates to a highly frost-resistant super-hydrophobic rubber cement mortar and a preparation method thereof. Background Art

[0002] In cold regions, concrete freeze-thaw damage is one of the main reasons for the premature failure of concrete buildings. In these areas, concrete damage is mostly related to freeze-thaw effects, which affect the service life, engineering quality, safety, etc. of buildings. Freeze-thaw effects directly lead to damage to the internal structure of concrete, making the concrete material structure loose and the mechanical properties degraded. In particular, when concrete is subjected to freeze-thaw environments with high water content, the destructive effects caused by uneven frost heave forces and frost heave deformations will have a significant impact on the strength and structural safety of concrete.

[0003] At present, the anti-seepage measures for concrete include: adding dense fillers, traditional sealing coatings, super-hydrophobic coatings, etc. By adding dense fillers, the density of concrete can be increased, the porosity can be reduced, and it has high impermeability, but its workability is poor and it is not easy to construct. Traditional sealing coatings form a dense protective film on the surface of concrete by brushing or spraying, isolating the concrete from external moisture. This method has a significant waterproof effect, but the bonding interface between the coating material and the concrete does not have the ability to resist freezing, and it is easy to form a "double skin" after freezing and thawing. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a highly frost-resistant super-hydrophobic rubber cement mortar and a preparation method thereof. The highly frost-resistant super-hydrophobic rubber cement mortar of the present invention has the characteristics of super-hydrophobicity, high impermeability, high frost resistance and green environmental protection, which can greatly reduce freeze-thaw damage and significantly extend the healthy service life of buildings in cold regions.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention:

[0007] The invention provides a high-freeze-resistant super-hydrophobic rubber cement mortar, which is composed of the following raw materials in parts by weight: 176-220 parts of water, 400 parts of cement, 540-630 parts of sand, 26-30 parts of rubber particles, 40 parts of microsilica powder and 60-66 parts of polydimethylsiloxane.

[0008] The addition of rubber particles can introduce "solid pores" and "air pores", providing a release space for the hydrostatic pressure, osmotic pressure and expansion pressure caused by the freezing of cement mortar, avoiding the defects of cracking of the cement matrix due to stress concentration, thereby improving the antifreeze performance of rubber cement mortar, which is equivalent to the effect of air entraining agent. However, the effect of rubber particles on the compressive strength of rubber cement mortar is negative. Polydimethylsiloxane reduces the water absorption rate of rubber cement mortar, thereby reducing the saturation of rubber cement mortar in the early stage of freeze-thaw, which is conducive to reducing the freeze-thaw damage of rubber cement mortar. Polydimethylsiloxane is also a low surface energy material that can reduce the surface energy of the coating, making the coating surface not easily wetted by water, thereby obtaining superhydrophobic properties. The addition of polydimethylsiloxane increases the contact angle between the coating surface and water and reduces the rolling angle, showing excellent superhydrophobic properties. The flexible Si-O-Si skeleton contained in polydimethylsiloxane can properly resist external impact, and its lower viscosity makes the modified rubber cement mortar have better impermeability. Polydimethylsiloxane has an inhibitory effect on cement hydration, which makes the initial strength of cement mortar lower. The addition of microsilica powder has the effect of filling pores, reducing "air pores", improving the compactness of rubber cement mortar and thus recovering the compressive strength of rubber cement mortar; on the other hand, it can stimulate cement hydration and eliminate the inhibitory effect of polydimethylsiloxane on cement hydration. In short, the present invention can greatly improve the frost resistance and super hydrophobicity of cement mortar through the synergistic effect of rubber particles, polydimethylsiloxane and microsilica powder without adding other substances.

[0009] Adding an appropriate amount of rubber particles can improve the fluidity of rubber cement mortar, but when the amount added is too large, the fluidity of rubber cement mortar will decrease, and the cohesiveness and water retention will deteriorate.

[0010] Furthermore, the highly frost-resistant super-hydrophobic rubber cement mortar is composed of the following raw materials in parts by weight: 176-200 parts of water, 400 parts of cement, 540-600 parts of sand, 26-28 parts of rubber particles, 40 parts of microsilica powder and 60-63 parts of polydimethylsiloxane.

[0011] Furthermore, the fineness modulus of the sand is 3.0-3.2. Preferably, the sand is river sand. Sand with this fineness modulus can improve the strength and wear resistance of the coating.

[0012] Furthermore, the particle size of the rubber particles is 60 meshes. The addition of rubber particles of this particle size can better improve the toughness and antifreeze performance of concrete. Rubber particles of this particle size can absorb part of the stress generated during the freeze-thaw process, reduce the expansion of cracks, and thus better improve the durability of concrete.

[0013] Furthermore, the microsilica powder is a spherical particle with a diameter of 1 μm. Microsilica powder of this particle size can fill the micropores in the cement mortar, improve its density, reduce water penetration, and thus enhance the freeze-thaw resistance. At the same time, the addition of microsilica powder of this particle size can also improve the strength and wear resistance of the coating.

[0014] The second technical solution of the present invention:

[0015] The invention provides a method for preparing the highly frost-resistant super-hydrophobic rubber cement mortar, comprising the following steps: accurately weighing each raw material according to the weight proportion, firstly mixing water and cement, and stirring evenly; then adding sand, rubber particles and microsilica powder while stirring, and continuing to stir evenly; and finally adding polydimethylsiloxane and stirring evenly.

[0016] Furthermore, the preparation method of the highly frost-resistant super-hydrophobic rubber cement mortar comprises the following steps: accurately weighing each raw material according to the weight proportion, first mixing water and cement, and stirring at a speed of 60 rpm for 30 seconds; then adding sand, rubber particles and microsilica powder while stirring, and stirring at a speed of 60 rpm for 60 seconds; finally adding polydimethylsiloxane, and stirring at a speed of 60 rpm for 90 seconds.

[0017] Adding raw materials in stages has at least the following advantages: (1) Improving mixing uniformity: It ensures that each component has enough time to mix with other components, thereby improving mixing uniformity. This is particularly important for the uniform distribution of components such as rubber particles, microsilica powder and polydimethylsiloxane, because the uniform distribution of these components directly affects the physical properties and durability of the final product. (2) Reducing material waste: Adding raw materials in stages can more accurately control the amount of each component, reducing material waste caused by adding too much or too little at one time. (3) Improving construction efficiency: Step-by-step mixing can reduce energy consumption and time during the mixing process, because each component can be processed according to its optimal mixing time and speed, rather than all components being mixed at the same time under the same conditions. (4) Improving workability: Step-by-step mixing helps improve the workability of mortar, such as workability, fluidity and anti-sagging. This is crucial for operations such as spreading and pumping during construction. (5) Improving strength and durability: Through step-by-step mixing, the hydration process of cement can be better controlled, thereby improving the strength and durability of the final product. (6) Reduce environmental impact: Step-by-step mixing can reduce dust and noise pollution at the construction site because the amount of water added and the mixing time during the mixing process can be more accurately controlled, reducing the impact on the environment. (7) Optimize material properties: Step-by-step mixing can be optimized according to the characteristics of different materials. For example, by adjusting the order and time of adding rubber particles and microsilica powder, the frost resistance and superhydrophobicity of rubber cement mortar can be improved. (8) Improve material stability: Step-by-step mixing helps to improve the stability of the material, especially when adding polydimethylsiloxane. Step-by-step addition can better control its dispersion in the mortar, thereby improving the superhydrophobicity.

[0018] Since the surface of cement mortar is a porous hydrophilic structure, water and salt can easily penetrate into the interior of cement mortar. Under the influence of cold climate environment, freeze-thaw disease is easily induced in the interior of cement mortar. According to the hydrostatic pressure theory and osmotic pressure theory of freeze-thaw degradation, during the freezing process of water in the large pores of cement mortar, the water phase changes to the ice phase and the volume expands. On the one hand, the unfrozen water is forced to transfer to the small pores, generating hydrostatic pressure, causing the cracking and development of the original cracks in the cement mortar; on the other hand, it causes the concentration of the solution in the pores to increase, and the concentration difference between the large and small pores is generated, causing the transfer of water from small pores to large pores, generating osmotic pressure, causing the cracks in the cement mortar to crack and break. Therefore, improving the anti-seepage performance of cement mortar can improve its anti-freeze performance. The super-hydrophobic coating method uses silane and siloxane with low surface energy as the main materials, and forms a highly hydrophobic cement mortar surface layer by surface coating or internal mixing, which can effectively improve the anti-freeze and anti-permeability of cement mortar. However, the bonding performance of the hydrophobic coating of the coating method and cement mortar is poor (same as traditional sealing coating). In order to solve the above problems, the present invention adopts the internal mixing method (cement-based super-hydrophobic coating) to improve the bonding strength, avoid the phenomenon of "two layers of skin" easily formed after freezing and thawing, and make the modified rubber cement mortar have better frost resistance and super-hydrophobicity. Rubber particles can provide deformation space for the volume expansion caused by water freezing, effectively alleviate the internal stress concentration of rubber cement mortar, greatly reduce the occurrence and development of cracks, thereby reducing the frost heave disease of rubber cement mortar; microsilica powder can fill the micropores in rubber cement mortar, improve the pore structure, and improve the impermeability of rubber cement mortar; polydimethylsiloxane can enhance the hydrophobicity of the surface and internal pore walls of rubber cement mortar, thereby reducing the capillary water absorption of rubber cement mortar, thereby improving the anti-seepage performance of rubber cement mortar.

[0019] Compared with the prior art, the present invention has the following advantages and technical effects:

[0020] (1) The present invention provides a highly frost-resistant super-hydrophobic rubber cement mortar, which has the characteristics of high impermeability and high frost resistance, and can significantly extend the healthy service life of buildings in cold regions.

[0021] (2) The present invention provides a highly frost-resistant super-hydrophobic rubber cement mortar, which, as a cement-based material, has strong bonding properties with concrete.

[0022] (3) The present invention provides a highly frost-resistant super-hydrophobic rubber cement mortar having the characteristic of super-hydrophobicity.

[0023] (4) The highly frost-resistant super-hydrophobic rubber cement mortar provided by the present invention is green, environmentally friendly and low-cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0025] Figure 1 The water absorption test results of the cement mortar prepared in Example 1 and Comparative Examples 1 to 3 are shown. DETAILED DESCRIPTION

[0026] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0027] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0028] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0029] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0030] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0031] Unless otherwise specified, the room temperature in the present invention is 25±2°C.

[0032] All raw materials used in the examples of the present invention are commercially available.

[0033] Unless otherwise specified, the “parts” used in the embodiments of the present invention are “parts by weight”.

[0034] In the embodiments of the present invention, the preparation method of the coating is not limited, as long as the target coating thickness can be achieved. As an example, some typical embodiments of the present invention are coated on the concrete surface by scraping.

[0035] In the embodiments and comparative examples of the present invention, the rubber particles are all crushed from waste automobile tire outer rubber, and the cost is low.

[0036] In the embodiments and comparative examples of the present invention, the cement is 42.5 grade composite silicate cement (composite silicate cement (P.C42.5) of Tapai Group).

[0037] It should be pointed out that the matters not described in detail in the present invention are conventional operating means in the art and are not the focus of the present invention.

[0038] The technical solution of the present invention is further illustrated by the following embodiments.

[0039] Example 1

[0040] The present embodiment provides a highly frost-resistant super-hydrophobic rubber cement mortar, which is composed of the following raw material components in parts by weight: 200 parts of water, 400 parts of cement, 590 parts of sand (river sand with a fineness modulus of 3.0-3.2), 28 parts of rubber particles with a particle size of 60 mesh, 40 parts of microsilica powder (spherical particles) with a diameter of 1 μm, and 63 parts of polydimethylsiloxane.

[0041] The preparation method of the highly frost-resistant super-hydrophobic rubber cement mortar of this embodiment is as follows: accurately weigh each raw material according to the above weight proportions, first add water and cement into a mixing container, and stir at a speed of 60rpm for 30s; then add sand, rubber particles and microsilica powder while stirring, and stir at a speed of 60rpm for 60s; finally add polydimethylsiloxane, and stir at a speed of 60rpm for 90s to obtain a mixture. The mixture is poured into a mold of 70.7mm×70.7mm×70.7mm, and after 1 day, the mold is removed to form a cubic mortar specimen of 70.7mm×70.7mm×70.7mm, and standard curing (temperature 20±3℃, humidity>99%) is performed for 28 days.

[0042] Example 2

[0043] The present embodiment provides a highly frost-resistant super-hydrophobic rubber cement mortar, which is composed of the following raw material components in parts by weight: 220 parts of water, 400 parts of cement, 540 parts of sand (river sand with a fineness modulus of 3.0-3.2), 26 parts of rubber particles with a particle size of 60 mesh, 40 parts of microsilica powder and 60 parts of polydimethylsiloxane.

[0044] The preparation method of the highly frost-resistant super-hydrophobic rubber cement mortar in this embodiment is the same as that in Example 1.

[0045] Example 3

[0046] The present embodiment provides a highly frost-resistant super-hydrophobic rubber cement mortar, which is composed of the following raw material components in parts by weight: 176 parts of water, 400 parts of cement, 550 parts of sand (river sand with a fineness modulus of 3.0-3.2), 30 parts of rubber particles with a particle size of 60 mesh, 40 parts of microsilica powder (spherical particles) with a diameter of 1 μm, and 62 parts of polydimethylsiloxane.

[0047] The preparation method of the highly frost-resistant super-hydrophobic rubber cement mortar in this embodiment is the same as that in Example 1.

[0048] Example 4

[0049] The present embodiment provides a highly frost-resistant super-hydrophobic rubber cement mortar, which is composed of the following raw material components in parts by weight: 200 parts of water, 400 parts of cement, 630 parts of sand (river sand with a fineness modulus of 3.0-3.2), 30 parts of rubber particles with a particle size of 60 mesh, 40 parts of microsilica powder (spherical particles) with a diameter of 1 μm, and 66 parts of polydimethylsiloxane.

[0050] The preparation method of the highly frost-resistant super-hydrophobic rubber cement mortar in this embodiment is the same as that in Example 1.

[0051] Comparative Example 1

[0052] This comparative example provides an ordinary cement mortar, which is composed of the following raw material components in parts by weight: 200 parts of water, 400 parts of cement and 600 parts of sand (river sand with a fineness modulus of 3.0-3.2).

[0053] The preparation method of ordinary cement mortar in this comparative example is as follows: accurately weigh the raw materials according to the above weight proportions, add 400 parts of water and cement into a mixing container, stir at a speed of 60rpm for 30s; then add sand while stirring, stir at a speed of 60rpm for 60s to obtain a mixture. Pour the mixture into a mold of 70.7mm×70.7mm×70.7mm, remove the mold after 1 day to make a cubic mortar specimen of 70.7mm×70.7mm×70.7mm, and perform standard curing (temperature 20±3℃, humidity>99%) for 28 days.

[0054] Comparative Example 2

[0055] The present comparative example provides a rubber cement mortar, which is composed of the following raw material components in parts by weight: 200 parts of water, 400 parts of cement, 540 parts of sand (river sand with a fineness modulus of 3.0-3.2) and 26 parts of rubber particles with a particle size of 60 meshes.

[0056] The preparation method of the rubber cement mortar of this comparative example is as follows: accurately weigh the raw materials according to the above weight proportions, first add water and cement into a mixing container, stir at a speed of 60rpm for 30s; then add sand and rubber particles while stirring, stir at a speed of 60rpm for 60s to obtain a mixture. Pour the mixture into a test mold of 70.7mm×70.7mm×70.7mm, remove the mold after 1 day to make a cubic mortar specimen of 70.7mm×70.7mm×70.7mm, and perform standard curing (temperature 20±3℃, humidity>99%) for 28 days.

[0057] Comparative Example 3

[0058] The present comparative example provides a super-hydrophobic rubber cement mortar, which is composed of the following raw material components in parts by weight: 200 parts of water, 400 parts of cement, 540 parts of sand (river sand with a fineness modulus of 3.0-3.2), 26 parts of rubber particles with a particle size of 60 mesh, and 60 parts of polydimethylsiloxane.

[0059] The preparation method of the super-hydrophobic rubber cement mortar in this comparative example is as follows: each raw material is accurately weighed according to the above weight parts, first water and cement are added to a mixing container, and stirred at a speed of 60rpm for 30s; then sand and rubber particles are added while stirring, and stirred at a speed of 60rpm for 60s; finally polydimethylsiloxane is added and stirred at a speed of 60rpm for 90s to obtain a mixture. The mixture is poured into a test mold of 70.7mm×70.7mm×70.7mm, and the mold is removed after 1 day to form a cubic mortar specimen of 70.7mm×70.7mm×70.7mm, and standard curing (temperature 20±3℃, humidity>99%) is performed for 28 days.

[0060] Performance Test:

[0061] Taking the cement mortar prepared in Example 1 and Comparative Examples 1-3 as an example, the performance of the cement mortar was tested, including:

[0062] (1) Contact angle test: The contact angle of the coating is tested using a contact angle measuring instrument of model KRUSSDSA100. The larger the contact angle, the stronger the hydrophobicity and the better the anti-seepage ability.

[0063] The contact angle results are shown in Table 1.

[0064] Table 1 Contact angle comparison

[0065] Comparison object Contact Angle Example 1 131° Comparative Example 1 46° Comparative Example 2 48° Comparative Example 3 130°

[0066] It can be seen from Table 1 that the contact angle of the highly frost-resistant super-hydrophobic rubber cement mortar of the present invention is improved by 172.9% compared with the ordinary cement mortar.

[0067] (2) Water absorption rate: The test is carried out in accordance with the test method of "Standard for Test Methods for Basic Properties of Building Mortar" (JGJ / T70-2009). The lower the water absorption rate, the better the anti-seepage ability.

[0068] The water absorption test results are as follows: Figure 1 As shown, from Figure 1 It can be seen that the high frost resistance super-hydrophobic rubber cement mortar prepared in Example 1 of the present invention has the smallest water absorption rate, which is close to that of the super-hydrophobic rubber cement mortar, and much smaller than that of the ordinary cement mortar and the rubber cement mortar.

[0069] (2) Compressive strength after 30 freeze-thaw cycles: The test was carried out in accordance with the test method of Standard Test Method for Basic Properties of Building Mortar (JGJ / T70-2009).

[0070] The test results of the compressive strength loss rate after freeze-thaw are shown in Table 2.

[0071] Table 2 Comparison of compressive strength loss rate after 30 freeze-thaw cycles

[0072] Comparison object Compressive strength loss rate / % Example 1 0.09 Comparative Example 1 0.49 Comparative Example 2 0.25 Comparative Example 3 0.22

[0073] Note: In Table 2, the compressive strength loss rate is the ratio of the difference between the compressive strength of cement mortar before freeze-thaw and the compressive strength after freeze-thaw to the compressive strength before freeze-thaw.

[0074] As can be seen from Table 2, the high frost resistance and super hydrophobic rubber cement mortar of Example 1 of the present invention has the smallest compressive strength loss after 30 freeze-thaw cycles, and the ordinary cement mortar has the largest compressive strength loss after 30 freeze-thaw cycles, followed by rubber cement mortar and super hydrophobic cement mortar, indicating that the high frost resistance and super hydrophobic rubber cement mortar of Example 1 has the best antifreeze performance, which is much greater than that of ordinary cement mortar.

[0075] There is no significant difference in performance between the highly frost-resistant super-hydrophobic rubber cement mortar prepared in Examples 2-4 and that in Example 1.

[0076] The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A highly frost-resistant super-hydrophobic rubber cement mortar, characterized in that: Calculated by weight, the composition is composed of the following raw materials: 176-220 parts of water, 400 parts of cement, 540-630 parts of sand, 26-30 parts of rubber particles, 40 parts of microsilica powder and 60-66 parts of polydimethylsiloxane.

2. The highly frost-resistant super-hydrophobic rubber cement mortar according to claim 1, characterized in that: Calculated by weight, it is composed of the following raw materials: 176-200 parts of water, 400 parts of cement, 540-600 parts of sand, 26-28 parts of rubber particles, 40 parts of microsilica powder and 60-63 parts of polydimethylsiloxane.

3. The highly frost-resistant super-hydrophobic rubber cement mortar according to claim 2, characterized in that: The fineness modulus of the sand is 3.0-3.

2.

4. The highly frost-resistant super-hydrophobic rubber cement mortar according to claim 2, characterized in that: The particle size of the rubber particles is 60 meshes.

5. The highly frost-resistant super-hydrophobic rubber cement mortar according to claim 2, characterized in that: The microsilica powder is spherical particles with a diameter of 1 μm.

6. A method for preparing the highly frost-resistant super-hydrophobic rubber cement mortar according to any one of claims 1 to 5, characterized in that: The method comprises the following steps: accurately weighing each raw material according to the weight proportion, firstly mixing water and cement and stirring evenly; then adding sand, rubber particles and microsilica powder while stirring and continuing to stir evenly; finally adding polydimethylsiloxane and stirring evenly.

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