Novel freeze-thaw-resistant high-strength thermal-insulation cement-based material for alpine regions

Abstract

The invention discloses a novel freeze-thaw-resistant high-strength thermal-insulation cement-based material for alpine regions. The novel freeze-thaw-resistant high-strength thermal-insulation cement-based material comprises the following parts: an air entraining agent, carbon nanotubes, PO ordinary Portland cement, expanded perlite and the like. In a cold region, in order to improve the freeze-thaw resistance of the cement-based material, an air entraining agent is generally used to form tiny bubbles in the cement-based material, and the bubbles can buffer volume expansion when water is frozen in a freeze-thaw cycle, so that the damage to the structure of the cement-based material is reduced. Meanwhile, the carbon nano tubes are used as reinforcing materials, so that the toughness and the strength of the cement-based material can be improved, the expansion of microcracks is prevented, and the elastic modulus of the cement-based material is reduced, so that the overall performance of the cement-based material is enhanced. In addition, by adding the expanded perlite, the influence of external temperature change on the interior of the cement-based material and the interior of a building can be reduced, the temperature in the building can be kept stable, energy consumption is reduced, and the durability and safety of the structure are improved.

Description

Technical Field

[0001] The invention belongs to the field of new multifunctional materials, and mainly relates to a new type of freeze-thaw resistant, high-strength thermal insulation cement-based material for use in high-cold areas. Background Art

[0002] In high-altitude cold regions, cement-based buildings often suffer from severe tests of freezing, cracking and freezing and thawing. The root cause of this phenomenon lies in the interaction between water intrusion and temperature changes. When water penetrates into the tiny pores and cracks of cement-based materials and encounters a low-temperature environment, the water molecules will condense into ice and expand in volume by about 9%. This volume expansion induces huge internal stresses inside the cement-based materials. Once these stresses exceed the tensile limit of the cement-based materials, cracks will be generated and expanded. These newly generated cracks provide channels for more water to penetrate, thereby exacerbating the destructive effects of the freeze-thaw cycle.

[0003] The freeze-thaw cycle itself is a repetitive process, where water in cement-based materials undergoes alternating changes of freezing and melting. Each such cycle will accumulate stress inside the cement-based material. Over time, the accumulation of these stresses will eventually destroy the microstructure of the cement-based material, manifesting as surface peeling, weakening of strength, and a decline in overall performance.

[0004] In addition, the thermal insulation performance of cement-based buildings is particularly critical in high-altitude cold regions. If the thermal insulation measures are insufficient, the temperature difference between the inside and outside of the building will become significant, and the external low temperature will quickly penetrate into the building, causing the internal temperature to drop. This drop in temperature makes it easier for the moisture inside the cement-based materials to freeze, thereby increasing the risk of freeze cracking and freeze-thaw. Therefore, in order to ensure the durability and stability of cement-based buildings in high-altitude cold regions, effective thermal insulation measures must be taken and the freeze-thaw resistance of cement-based materials must be optimized to withstand the challenges brought by extreme climatic conditions.

[0005] In order to improve the strength of materials, reduce the impact of freeze-thaw cycles, and increase the service life of cement-based building materials in high-altitude cold regions, various countries have adopted various measures, such as selecting suitable cementitious materials according to different environments, selecting suitable water-cement ratios and sand ratios, applying protective coatings on the surface of cement-based materials to prevent freeze-thaw effects of cement-based materials, and using antifreeze agents to resist freeze-thaw effects.

[0006] However, there is currently no means that can simultaneously and effectively solve the problems of insufficient material strength and thermal insulation caused by freeze-thaw cycles in buildings in high-cold areas. Therefore, it is necessary to find an effective solution that can not only suppress the impact of low temperature on cement-based materials, but also solve the problem of poor thermal insulation performance of cement-based materials in high-cold areas and have higher material strength.

[0007] The present invention discloses a new type of freeze-thaw resistant, high-strength thermal insulation cement-based material for use in high-cold areas, which is composed of expanded perlite, carbon nanotubes, air-entraining agent, PO ordinary Portland cement and other parts. Among them, reducing the impact of external temperature changes on the interior of cement-based materials and the interior of buildings helps to maintain the temperature inside the building stable, reduce energy consumption, and improve the durability and safety of the structure. Carbon nanotubes are used to enhance toughness, prevent the expansion of microcracks, improve the compressive and flexural strength of cement-based materials, reduce the elastic modulus of cement-based materials, and play a role in toughening cement-based materials. Air-entraining agents are used to form tiny bubbles in cement-based materials. These bubbles can buffer the volume expansion when water freezes during freeze-thaw cycles, thereby reducing damage to the structure of cement-based materials. Summary of the invention

[0008] The present invention aims to solve the problems that existing cement-based materials have poor thermal insulation effects in cold areas and are susceptible to freeze-thaw effects, resulting in reduced lifespan. The present invention designs and discloses a new type of freeze-thaw resistant, high-strength thermal insulation cement-based material for use in high-cold areas, and uses a shelling process and secondary mixing technology to treat hydrophobic expanded perlite aggregate. First, soak the perlite in water for about 5 minutes, and dry it until the surface is dry after it is close to saturation. Subsequently, the cement and water are mixed and stirred, and the pre-wetted perlite is added for secondary stirring to ensure that the surface of the perlite is evenly covered with cement slurry. After stirring is completed, the mixture is placed and allowed to stand naturally for 6 hours to form an expanded perlite aggregate wrapped in a hard shell.

[0009] According to some embodiments of the present invention, a new type of freeze-thaw resistant, high-strength thermal insulation cement-based material for high-cold areas, a QM-QX2 all-round planetary ball mill is used to refine carbon nanotubes, using a ball-to-material ratio of 40:1 and running at 200rpm for 3 hours. Afterwards, polyvinyl pyrrolidone (PVP) is used as a surfactant to improve the dispersibility of carbon nanotubes. The operating steps include: dissolving PVP in water, adding ball-milled carbon nanotubes, stirring for 10 minutes, and then standing for 3 hours to form a uniform carbon nanotube aqueous dispersion. The preparation of this dispersion significantly improves the flexural strength and ultimate strain capacity of cement-based materials, because carbon nanotubes can effectively prevent crack expansion and absorb destructive energy.

[0010] According to some embodiments of the present invention, a new type of freeze-thaw resistant, high-strength thermal insulation cement-based material for use in high-cold areas, wherein the air-entraining agent is a modified rosin compound. When the air-entraining agent is added in a small amount, a large number of closed and tiny bubbles can be formed in the concrete. These bubbles become more stable over time, and during the pouring and vibration process, the loss rate of the air content gradually decreases.

[0011] According to some embodiments of the present invention, a new type of freeze-thaw resistant, high-strength thermal insulation cement-based material for high-cold areas, wherein the water-cement ratio of the PO ordinary Portland cement cement-based material is 0.34, water is mixed with a polycarboxylic acid high-efficiency water reducer, and stirred evenly with a glass rod. Pour cement and an aqueous solution containing a polycarboxylic acid high-efficiency water reducer into a stirring pot, first stir at a low speed for 30 seconds, then stir at a high speed for 150 seconds, then add the prepared expanded perlite aggregate, carbon nanotube dispersion and air entraining agent and continue stirring, first stir at a low speed for 30 seconds, then stir at a high speed for 90 seconds, to make a cement-based material, and place it indoors for standard maintenance.

[0012] According to some embodiments of the present invention, a new type of freeze-thaw resistant, high-strength thermal insulation cement-based material for use in high-cold areas can inhibit the reduction of life caused by freeze-thaw effects and thus reduce economic losses. Compared with the prior art, the present invention is characterized by:

[0013] (1) A new type of freeze-thaw resistant, high-strength thermal insulation cement-based material for use in high-cold areas. The strength of the cement-based material is higher than that of normal sewage pipe cement-based materials, which can reduce the cracking of cement-based materials and increase the service life of cement-based materials in cold areas.

[0014] (2) A new type of freeze-thaw-resistant, high-strength thermal insulation cement-based material used in high-altitude cold regions can maintain the temperature inside buildings and thus reduce the energy loss used for insulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the principle of a new type of freeze-thaw resistant, high-strength thermal insulation cement-based material used in high-cold areas in the implementation of the present invention.

[0016] Item numbers in the figure: 1-cement-based material, 1-1 expanded perlite, 1-2 carbon nanotubes, 1-3 air entraining agent, 1-4PO ordinary Portland cement.

[0017] Figure 2 This is a schematic diagram of an enlarged electron microscope of expanded perlite, a new type of freeze-thaw resistant, high-strength thermal insulation cement-based material used in high-cold areas in the implementation of the present invention.

[0018] Figure 3 This is a schematic diagram of an enlarged electron microscope image of carbon nanotubes in a new type of freeze-thaw resistant, high-strength thermal insulation cement-based material used in high-cold areas in the implementation of the present invention.

[0019] Figure 4 The figure is a schematic diagram of the EDS energy spectrum of the distribution of various elements in a new type of freeze-thaw resistant, high-strength thermal insulation cement-based material used in high-cold areas in the implementation of the present invention.

[0020] Figure 5 This is a total element distribution spectrum of a new type of freeze-thaw resistant, high-strength thermal insulation cement-based material used in high-cold areas in the implementation of the present invention. DETAILED DESCRIPTION

[0021] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limitations on the present invention. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0022] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0023] Combination Figure 1 The invention discloses a novel freeze-thaw resistant, high-strength thermal insulation cement-based material for use in high-cold areas, which is made of the following raw materials in percentage by weight: expanded perlite particles (1-1) as aggregate are added in an amount of 120% of the weight of cement, carbon nanotubes (1-2) account for 0.5% to 2% of the weight of cement, and air entraining agent (1-3) accounts for 0.05% to 0.2% of the weight of cement.

[0024] Combination Figure 2 The present invention discloses a new type of freeze-thaw resistant, high-strength thermal insulation cement-based material for use in high-cold areas. From the enlarged schematic diagram of expanded perlite (1-1) in an electron microscope, it can be seen that the expanded perlite (1-1) is a lightweight material with a large number of closed pores. These pores not only reduce the density of the material, but also significantly improve the thermal insulation performance due to its low thermal conductivity. Air is an excellent insulator in a static state, and the high porosity inside the expanded perlite (1-1) further enhances this thermal insulation effect, making it difficult for heat to be conducted through the material. In addition, the lightweight characteristics of the expanded perlite (1-1) simplify the construction process and reduce the deadweight of the building. At the same time, its chemical stability ensures a long-term and stable thermal insulation effect, while enhancing the durability and safety of the building.

[0025] Combination Figure 3The present invention discloses a new type of freeze-thaw resistant, high-strength thermal insulation cement-based material for use in high-cold areas. From the enlarged schematic diagram of carbon nanotubes in an electron microscope, it can be seen that the diameter range of carbon nanotubes (1-2) is 1-50nm and the length range is 0.5-10μm. Carbon nanotubes can significantly enhance the tensile strength of cement-based materials due to their extremely high strength and elastic modulus. When water freezes at low temperatures and causes volume expansion, the presence of carbon nanotubes can better resist the resulting internal stress, thereby reducing the formation of cracks. In the freeze-thaw cycle, carbon nanotubes can disperse and absorb local stress concentration, reduce the direct impact of stress on cement-based materials, thereby delaying or preventing the expansion of cracks, and have excellent energy absorption capacity. They can absorb and dissipate part of the energy during the freeze-thaw process, reducing damage to cement-based materials. The interface modification between carbon nanotubes and the cement matrix can improve the bonding strength of the interface, enhance the overall performance of cement-based materials, and make them more resistant to freeze-thaw effects.

[0026] Combination Figure 4 The present invention discloses a novel freeze-thaw resistant, high-strength thermal insulation cement-based material for use in high-cold areas. From the enlarged schematic diagram of carbon nanotubes in an electron microscope, it can be seen that when rosin-based air-entraining agents are added to concrete mixtures, they first dissolve in water to form a solution containing active molecules. These molecules have a special chemical structure, one end is hydrophilic and the other end is hydrophobic, so that they can form a stable monomolecular film at the interface between water and air. During the mixing of concrete, air is naturally drawn into the mixture. When these air come into contact with the solution containing air-entraining agents (1-4), the air-entraining agent (1-4) molecules quickly gather on the surface of the bubbles, reducing the surface tension of the bubbles, thereby promoting the formation and stability of the bubbles. The size of these bubbles is usually controlled between 50 and 200 microns, and they are evenly distributed in the concrete to form a microscopic bubble network. These tiny bubbles still maintain their structure after the concrete hardens, and they form tiny buffer spaces inside the concrete. These spaces can provide additional elasticity when concrete is subjected to external pressure, freeze-thaw cycles or other stresses, reduce the occurrence of cracks, and improve the crack resistance and durability of concrete. In addition, the presence of bubbles can also reduce the density of concrete and reduce the permeability of water, thereby further improving the waterproof performance and overall quality of concrete and achieving the purpose of reducing economic losses.

Claims

1. A new type of freeze-thaw resistant, high-strength thermal insulation cement-based material for use in high-cold areas, characterized by: The cement-based material (1) is prepared by mixing expanded perlite (1-1), carbon nanotubes (1-2), an air entraining agent (1-3) and PO ordinary Portland cement (1-4) in a certain proportion and then casting them together; wherein the expanded perlite (1-1) is used to maintain a constant temperature inside a building, thereby saving energy used to maintain the temperature inside the building; the carbon nanotubes (1-2) can improve the toughness and strength of the cement-based material, prevent the spread of microcracks, and enhance its compression and flexural resistance, while reducing the elastic modulus of the material, thereby enhancing the toughness of the cement; the air entraining agent (1-3) is used to generate tiny bubbles in the cement-based material, and these bubbles can buffer the volume expansion of water when it freezes during the freeze-thaw cycle; and the PO ordinary Portland cement (1-4) is used as a cement binder.

2. The novel freeze-thaw resistant, high-strength thermal insulation cement-based material for use in alpine regions according to claim 1, characterized in that: Expanded perlite (1-1) is obtained by preheating and roasting perlite ore. This patent uses hydrophobic expanded perlite material.

3. The novel freeze-thaw resistant, high-strength thermal insulation cement-based material for use in alpine regions according to claim 1, characterized in that: Carbon nanotubes (1-2), with diameters ranging from 1 to 50 nanometers and lengths ranging from 0.5 to 10 micrometers, significantly enhance the mechanical strength and crack resistance of cement-based materials with their excellent mechanical properties.

4. The novel freeze-thaw resistant, high-strength thermal insulation cement-based material for use in alpine regions according to claim 1, characterized in that: After optimization, the proportion of each component in the material is as follows: expanded perlite particles (1-1) as aggregate account for 120% of the cement weight, carbon nanotubes (1-2) account for 0.5% to 2% of the cement weight, air entraining agent (1-3) account for 0.05% to 0.2% of the cement weight, and the cement water-cement ratio is 0.34.

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