Moisturizing and crack-resistant high-ductility concrete and preparation method thereof

Abstract

The present invention relates to the technical field of concrete preparation, specifically to a moisture-retaining and crack-resistant high-ductility concrete and a preparation method thereof, wherein the components of the moisture-retaining and crack-resistant high-ductility concrete include: 350-450 parts of ordinary Portland cement, 200-300 parts of fly ash, 30-50 parts of silica ash, 250-350 parts of quartz sand, 0.5-1 parts of water reducer, 10-20 parts of expansion agent, 0.1-0.3 parts of retarder, 0.5-1 parts of thixotropic lubricant, 0.2-0.7 parts of modified nanomaterials, 0.7-3 parts of modified composite curing agent, 5-10 parts of anti-cracking agent, 5-12 parts of polymer fiber, and 180-220 parts of water. The present invention has the characteristics of high moisture retention and high water retention, helps to maintain its internal humidity balance, reduces cracks caused by drying shrinkage, improves the durability of concrete, and significantly reduces the risk of cracking of concrete during hardening, makes the concrete structure more complete, and improves the safety and service life of the structure.

Description

Technical Field

[0001] The invention relates to the technical field of concrete preparation, in particular to a moisture-retaining, crack-resistant, high-ductility concrete and a preparation method thereof. Background Art

[0002] High-ductility concrete has unique technical advantages in the field of seismic reinforcement and reconstruction of rural houses. Its tensile and strain hardening properties significantly improve the safety of the reconstructed buildings. However, its high amount of cementitious materials also brings certain cracking risks, especially in specific environments, such as dry and windy, high temperature, and long sunshine time. On the one hand, in a dry environment, the moisture inside the high-ductility concrete will be lost to the outside through the pores, resulting in drying shrinkage. When the tensile stress generated by drying shrinkage exceeds the tensile strength of the high-ductility concrete, cracks will be generated. These cracks will not only affect the appearance, but also reduce its durability and provide channels for the invasion of harmful substances from the outside. On the other hand, in the cement hydration process, sufficient water is crucial to ensure the hydration of cement, especially for high-ductility concrete, which has a high content of cementitious materials. The water-deficient environment seriously affects the continuous hydration of cementitious materials in high-ductility concrete. Sprinkling water can only partially solve the problem of dryness and water shortage in the early stage, and insufficient hydration will significantly affect the growth of strength and durability of high-ductility concrete, which is not conducive to the stable use of the structure.

[0003] As an advanced reinforcement material, high-ductility concrete has been widely used in the national primary and secondary school earthquake-resistant reinforcement and rural dilapidated housing renovation projects, as well as industrial building renovation and reinforcement, cultural relics protection and reinforcement, etc. High-ductility concrete has high strength, high toughness and high damage resistance. Its tensile deformation capacity can reach more than 100 times that of ordinary concrete. It is called "bendable concrete". When using high-ductility concrete to reinforce a house, it is only necessary to apply about 1.5 cm thick high-ductility concrete to the connection between the load-bearing brick columns and the wall columns of the house. Even in an earthquake, the house will not collapse easily. Moreover, this technology is simple to construct and has a short construction period. It can save 70% of the construction period and materials and 30% of the construction cost.

[0004] However, some problems have been found in practical applications. The higher content of cementitious materials in high-ductility concrete leads to higher autogenous shrinkage. Although the higher tensile properties of high-ductility concrete can limit the occurrence of cracks to a certain extent, when the drying shrinkage is large, the sum of the tensile stress generated by the autogenous shrinkage and drying shrinkage of high-ductility concrete will exceed the tensile properties of high-ductility concrete itself, thus causing cracks. During summer construction, higher temperatures and longer sunshine hours lead to greater drying shrinkage of high-ductility concrete during construction, and cracking increases significantly, especially in the extremely hot environment in Xinjiang and other places, which seriously affects the safe use of the structure. Summary of the invention

[0005] In view of the deficiencies of the prior art, the object of the present invention is to provide a moisture-retaining, crack-resistant, high-ductility concrete and a preparation method thereof.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A moisture-retaining, crack-resistant, high-ductility concrete comprises the following components in parts by mass: 350-450 parts of ordinary Portland cement, 200-300 parts of fly ash, 30-50 parts of silica fume, 250-350 parts of quartz sand, 0.5-1 parts of water reducer, 10-20 parts of expansion agent, 0.1-0.3 parts of retarder, 0.5-1 parts of thixotropic lubricant, 0.2-0.7 parts of modified nanomaterials, 0.7-3 parts of composite curing agent, 5-10 parts of anti-cracking agent, 5-12 parts of polymer fiber and 180-220 parts of water.

[0008] Preferably, the modified composite curing agent is prepared by the following steps:

[0009] S11. Mixing sodium silicate and wood fiber in a blender at a mass ratio of 1:1 at a temperature of 18-20° C. for 15-20 min to obtain a preliminary mixture;

[0010] S12. Add starch-grafted sodium acrylate and cellulose ether in an amount equal to the mass of sodium silicate to the preliminary mixture, and continue stirring at 60-80° C. for 10-15 minutes to obtain a modified composite curing agent.

[0011] Preferably, during the preparation of the modified composite curing agent, the stirring speed is 60-80 r / min.

[0012] Preferably, the modified nanomaterial is prepared by the following steps:

[0013] S21. The polyacrylate dispersant and anhydrous ethanol are mixed in a mass ratio of 1:1-1.5 and stirred to obtain a solvent containing a dispersant;

[0014] S22. The mass of 15-20% of nano-silicon powder and 20-25% of carbon nanotubes of a polyacrylate dispersant was gradually added to a solvent containing a dispersant, stirred evenly, and then ultrasonically dispersed using an ultrasonic processor at a frequency of 70-80kHZ for 3-5min to obtain a nanosuspension;

[0015] S23. Filter the nano suspension through a filter membrane to remove undispersed particles and impurities to obtain a pure modified nano material mixture, and then place it in a vacuum drying oven, dry it at 100-120°C for 25-30 minutes, and then crush it to obtain the modified nano material.

[0016] Preferably, during the preparation of the modified nanomaterial, the stirring speed is 250-300 r / min.

[0017] Preferably, the water reducer is a polycarboxylate water reducer.

[0018] Preferably, the expansion agent is a calcium-magnesium composite expansion agent.

[0019] Preferably, the polymer fiber is an ultra-high molecular weight synthetic fiber.

[0020] Preferably, the retarder comprises sodium gluconate and borax in a mass ratio of 1:1-1.5.

[0021] A method for preparing a moisture-retaining, crack-resistant, high-ductility concrete, used to prepare the above-mentioned moisture-retaining, crack-resistant, high-ductility concrete, comprises the following steps:

[0022] S1. Ordinary Portland cement, fly ash, silica fume, quartz sand, water reducer, expansion agent, retarder, thixotropic lubricant and anti-cracking agent were sequentially added to the mixer for dry mixing, the stirring speed was set to 60-80r / min, the stirring time was 3-5min, and a high ductility concrete premix was obtained;

[0023] S2. Add water and the prepared modified composite curing agent to the high ductility concrete premix and stir thoroughly, first at a stirring speed of 60-80r / min for 2-3min, then at a stirring speed of 100-120r / min for 1-2min to obtain a uniformly stirred mixture;

[0024] S3. The modified nanomaterials and polymer fibers are evenly added to the uniformly stirred mixture, the stirring speed is set to 100-120 r / min, and the stirring time is set to 3-5 min to obtain a moisture-retaining, crack-resistant, high-ductility concrete.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention modifies the composite curing agent to have good moisture retention performance. By modifying the composite curing agent, the moisture-retaining, crack-resistant, high-ductility concrete can effectively retain internal moisture and reduce water evaporation under extremely hot conditions. This not only ensures the smooth progress of the construction process and avoids construction difficulties caused by excessive water loss of concrete, but also after the concrete hardens, the high moisture retention and high water retention properties help maintain its internal humidity balance, reduce cracks caused by drying shrinkage, and improve the durability of the concrete.

[0027] 2. Enhanced anti-cracking performance. The retarder reduces the hydration heat release rate and the internal stress caused by temperature changes. The stable three-dimensional structure formed by the anti-cracking agent effectively inhibits the shrinkage of the material. The two work together to significantly reduce the risk of concrete cracking during the hardening process, making the concrete structure more complete and improving the safety and service life of the structure.

[0028] 3. Improved mechanical and durability properties. The modified nanomaterials prepared by nano-silicon powder and carbon nanotubes through technical means have improved the density, tensile strength and toughness of concrete. This allows concrete to exhibit better mechanical properties when bearing loads, while enhancing its ability to resist external erosion factors (such as chemical erosion, physical wear, etc.), extending the service life of high-ductility concrete and reducing maintenance and replacement costs. Composite curing agents and water-retaining agent materials provide a continuous water source for cement hydration, ensuring the full hydration of cement, thereby improving the strength of concrete. At the same time, due to the reduction of the generation and expansion of cracks, the channels for external harmful substances to invade the interior of the concrete are effectively blocked, reducing the probability of durability problems such as steel bar corrosion and concrete carbonization. In addition, the use of mineral admixtures has further improved the microstructure of concrete and improved its resistance to chemical erosion. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a process flow chart of the preparation of the moisture-retaining, crack-resistant, high-ductility concrete of the present invention;

[0030] Figure 2 The figure is a flow chart of the preparation process of the modified composite curing agent of the present invention;

[0031] Figure 3 The present invention is a flow chart of the preparation process of the modified nanomaterial. DETAILED DESCRIPTION

[0032] The present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] See also Figure 1-3 , the present invention provides a technical solution:

[0034] In the following embodiments, a moisture-retaining, crack-resistant, high-ductility concrete is prepared from ordinary Portland cement, fly ash, silica fume, quartz sand, water-reducing agent, expansion agent, retarder, thixotropic lubricant, modified nanomaterial, modified composite curing agent, anti-cracking agent, water-retaining agent, polymer fiber and water. The modified nanomaterial is prepared from nano silicon powder and carbon nanotubes, and the modified composite curing agent is prepared from silicate curing agent, fiber material, starch grafted sodium acrylate and cellulose ether. Ordinary Portland cement, as the main cementitious material, supports the development of the early and mid-term mechanical properties of high-ductility concrete. Fly ash, as the main auxiliary cementitious material, can effectively reduce the early hydration heat of the matrix on the one hand, and ensure the stable growth of the late performance of the matrix on the other hand, and can improve the durability to a certain extent. Silica fume can not only improve the density of the matrix, improve the mechanical and durability properties, but also has a significant effect on adjusting the slurry construction performance. Water reducer is used to adjust the construction performance and mechanical properties, expansion agent is used to compensate for the shrinkage deformation of high ductility concrete, retarder can ensure that the slurry has enough constructible specimens in a hot environment, and thixotropic lubricant can reduce the resistance during plastering and improve construction efficiency. Modified nanomaterials are prepared from carbon nanotubes and nano silicon powder, which significantly improve the mechanical and durability properties of high ductility concrete. Cellulose ether can adjust the viscosity of the slurry to ensure effective bonding between the slurry and the foundation surface. Composite curing agent is prepared by mixing silicate materials and fiber materials, which can react with the hydration products in the matrix to produce hydrated calcium silicate gel, fill the pores of the matrix, improve the mechanical properties and durability of the structure, and effectively improve the water retention of the matrix and promote the continuous hydration of the cementitious material. Anti-cracking agent can form a stable three-dimensional structure in the high ductility concrete matrix, effectively inhibit the cracking of the matrix, and water retaining agent can ensure that the slurry has sufficient moisture retention time in a high temperature environment, which is convenient for layered construction and finishing. Polymer fibers can effectively improve the toughness and deformation capacity of the matrix, ensuring that the matrix exhibits multi-crack cracking and strain hardening characteristics after being loaded, and can limit the generation and development of cracks to a certain extent.

[0035] The weight proportion of each component in the present invention can ensure that the working performance, mechanical properties and durability of high-ductility concrete reach the best state. Among them, the water reducer is a polycarboxylate water reducer; the expansion agent is a calcium-magnesium composite expansion agent; and the retarder component includes sodium gluconate and borax. The polycarboxylate water reducer interacts with ions in water to form a surfactant, the calcium-magnesium composite expansion agent reacts with water to form a colloidal substance, the colloidal substance includes magnesium hydroxide and calcium hydroxide, the colloidal substance fills the micropores inside the concrete, and the sodium gluconate and borax react with the colloidal substance to form calcium gluconate and calcium borate.

[0036] Anti-cracking agent can form a multi-dimensional structure with water, which can effectively reduce the capillary pressure and surface shrinkage tension, and can significantly reduce the self-shrinkage and shrinkage in the cement system. Anti-cracking agent is an inorganic medium. After the cement-based material is mixed with water, the water has a high surface tension, and shrinkage stress will be generated in the system during the early evaporation of water. After adding anti-cracking agent, it can be quickly dispersed in the slurry and form a three-dimensional structure with water, effectively reducing the capillary and surface shrinkage tension. As the cement hydration proceeds, the multi-dimensional structure will become more stable. After the matrix hardens, the multi-dimensional structure can significantly improve the mortar's crack resistance and improve the durability of the material.

[0037] Polymer fibers are ultra-high molecular weight synthetic fibers. Ultra-high molecular weight synthetic fibers have extremely high tensile strength and deformation capacity, and are the key raw materials for achieving the unique characteristics of high-ductility concrete that are different from ordinary concrete. They have good alkali resistance and can maintain long-term stable operation in a strong alkaline environment. Moreover, the extremely high tensile properties of ultra-high molecular weight synthetic fibers can resist the high autogenous shrinkage and drying shrinkage of high-ductility concrete, and to a certain extent limit the generation and development of cracks. After the matrix cracks, the ultra-high molecular weight synthetic fibers can cross the cracks and continue to transfer loads, ultimately helping high-ductility concrete to achieve the characteristics of multi-crack cracking and stable absorption of kinetic energy, and also giving the material ultra-high deformation capacity.

[0038] In a method for preparing a moisture-retaining, crack-resistant, high-ductility concrete of the present invention, nano-silicon powder and carbon nanotubes are modified, and modified nano-materials are obtained by mixing, drying, and the like. It is understandable that nano-materials are prone to agglomeration due to their high surface energy or strong van der Waals forces, which affects their performance and application. Therefore, it is necessary to perform surface modification on the nano-materials to improve their dispersibility and functionality, and ultrasonic treatment helps the nano-materials to be evenly dispersed in the solvent. In the process of preparing nano-silicon powder and carbon nanotubes into nano-suspensions, the dispersion effect in the solvent is crucial. Dispersants can help nano-materials to be better dispersed in the solvent. According to the characteristics of nano-silicon powder and carbon nanotubes, polyacrylate dispersants and anhydrous ethanol are selected as dispersants to ensure that the nano-materials are evenly dispersed in the solvent. Among them, the polyacrylate dispersant and anhydrous ethanol are stirred evenly to obtain a solvent containing a dispersant. It is understandable that nano-silicon powder has a high specific surface area and surface activity, and is often easy to agglomerate. Therefore, when preparing a suspension, it is necessary to ensure that the nano-silicon powder can be evenly dispersed in the solvent. Polyacrylate dispersants can help nano-silicon powder disperse better in the solvent. Carbon nanotubes are prepared into a suspension, and a suitable dispersant is also required to ensure their dispersion effect in the solvent, and anhydrous ethanol has the corresponding effect. Therefore, polyacrylate dispersants and anhydrous ethanol are selected as dispersants for the two nanomaterials to help form a uniform and stable suspension. Ultrasonic treatment helps to break the agglomeration between nanomaterials, helps nanomaterials to be evenly dispersed in the solvent, and can promote them to form a more stable and uniform nanosuspension. There are a certain number of unevenly dispersed particles and impurities in the prepared nanosuspension, which need to be purified by filtration. In order to facilitate the use of nanomaterials in high-ductility concrete, it is necessary to prepare them into granular or powdered nanomaterials by methods such as drying and crushing.

[0039] In a method for preparing a moisture-retaining, crack-resistant, high-ductility concrete of the present invention, silicate materials, fiber materials, starch-grafted sodium acrylate and cellulose ether are mixed in a certain proportion to prepare a modified composite curing agent. It is understandable that the silicate curing agent can react with calcium hydroxide in the matrix soil to generate a hydrated calcium silicate gel with water-retaining properties. This gel can fill the pores of the matrix, improve the density and strength of the matrix, and reduce the evaporation of water, thereby playing a curing role. However, the water retention rate of silicate curing agents is low, and the internal curing effect is biased. Fiber materials such as wood fiber, as internal curing materials with excellent performance, can significantly improve the shortcomings of silicate curing agents. Cellulose ether and starch-grafted sodium acrylate can increase the viscosity of silicate curing agents, thereby further enhancing their water retention, reducing water evaporation and water seepage, and ensuring that the concrete retains sufficient moisture during construction and hardening to maintain the hydration reaction of cement. The prepared modified composite curing agent can effectively improve the internal structure of the matrix, enhance density and durability, reduce the risk of cracking, and extend the service life of the material.

[0040] In the preparation method of a moisture-retaining, crack-resistant, high-ductility concrete of the present invention, various raw materials are first dry-mixed in order to evenly distribute the various raw materials in the high-ductility concrete system, and then water and curing agents are added to quickly mix them evenly, and the stirring speed and time are controlled. The modified nanomaterials and polymer fibers have a more obvious effect on the working performance of the slurry, so they are added after other materials are evenly stirred to avoid excessively high stirring speeds and long stirring times, which affect the effective functioning of the modified nanomaterials and polymer fibers.

[0041] It should be noted that in step S1, ordinary Portland cement, fly ash, silica fume, quartz sand, water reducer, expansion agent, retarder, thixotropic lubricant and anti-cracking agent are sequentially added to the mixer for dry mixing, and the stirring speed is set to 60-80r / min, and the stirring time is 3-5min to obtain a high ductility concrete premix. It is understandable that the properties of cement-based raw materials will not change even if they are stirred for a long time. Dry mixing in advance can make various raw materials evenly distributed, so that when adding water and stirring, each component can react quickly with water to play its due effect, avoid the purpose of achieving uniform mixing by methods such as accelerating the stirring speed and extending the stirring time, and reduce the dependence on the stirring equipment.

[0042] Steps S2 and S3 add water and the prepared modified composite curing agent to the high ductility concrete premix and stir thoroughly, first stir at a stirring speed of 60-80r / min for 2-3min, and then stir at a stirring speed of 100-120r / min for 1-2min to obtain a uniformly stirred mixture. The modified nanomaterials and polymer fibers are uniformly added to the uniformly stirred mixture, the stirring speed is set to 100-120r / min, and the stirring time is set to 3-5min to obtain a moisture-retaining and crack-resistant high ductility concrete. It is understandable that the modified nanomaterials have a large specific surface area, a high water demand, and a long polymer fiber size, which will affect the difficulty of mixing the slurry. In order to improve the mixing efficiency and reduce the dependence on mixing equipment and mixing methods, a segmented mixing method is adopted. The premix is ​​first fully mixed with water, and then the modified nanomaterials and polymer fibers are added. This not only reduces the difficulty of mixing, but also reduces the mixing time of the modified nanomaterials and polymer fibers, avoiding the occurrence of agglomeration, uneven dispersion, etc. due to excessively fast mixing speed or excessively long mixing time.

[0043] Example 1

[0044] S101. 35kg of ordinary Portland cement, 20kg of fly ash, 3kg of silica fume, 25kg of quartz sand, 0.05kg of water reducer: polycarboxylate water reducer, 1kg of expansion agent: calcium magnesium composite expansion agent, 0.01kg of retarder: sodium gluconate and borax in a mass ratio of 1:1, 0.05kg of thixotropic lubricant and 0.5kg of anti-cracking agent were added to the mixer in sequence for dry mixing, the stirring speed was set to 60r / min, the stirring time was 3min, and a high ductility concrete premix was obtained;

[0045] S1011. Mixing sodium silicate and wood fiber in a blender at a mass ratio of 1:1 at 18° C. for 15 min to obtain a preliminary mixture;

[0046] S1012. Adding starch-grafted sodium acrylate and cellulose ether in an amount equal to the mass of sodium silicate to the preliminary mixture, stirring was continued at 60° C. for 10 min to obtain a modified composite curing agent;

[0047] S102. Add 18kg of water and 0.07kg of the prepared modified composite curing agent to the high ductility concrete premix and stir thoroughly, first at a stirring speed of 60r / min for 2min, then at a stirring speed of 100r / min for 1min to obtain a uniformly stirred mixture;

[0048] S1021. The polyacrylate dispersant and anhydrous ethanol are mixed in a mass ratio of 1:1 and stirred to obtain a solvent containing a dispersant;

[0049] S1022. 15% of the mass of the polyacrylate dispersant and 20% of the carbon nanotubes were gradually added to the solvent containing the dispersant, stirred evenly, and then ultrasonically dispersed using an ultrasonic processor, the frequency was set to 70kHZ, and the ultrasonic treatment time was 3min to obtain a nanosuspension;

[0050] S1023. The nano suspension is filtered through a filter membrane to remove undispersed particles and impurities to obtain a pure modified nanomaterial mixture, which is then placed in a vacuum drying oven, dried at 100° C. for 25 min, and then pulverized to obtain a modified nanomaterial;

[0051] S103. Evenly add 0.02kg of modified nanomaterials and 0.5kg of polymer fibers into the uniformly stirred mixture, set the stirring speed to 100r / min, and set the stirring time to 3min to obtain moisture-retaining, crack-resistant, and highly ductile concrete, which is then poured into the prepared mold for molding. During the molding process, the concrete needs to be vibrated on a vibration table, compacted and smoothed, and cured after demolding for 24 hours. The curing temperature is 18°C ​​and the curing humidity is 95%.

[0052] Example 2

[0053] S201. 45kg of ordinary Portland cement, 30kg of fly ash, 5kg of silica fume, 35kg of quartz sand, 0.1kg of water reducer: polycarboxylate water reducer, 2kg of expansion agent: calcium magnesium composite expansion agent, 0.03kg of retarder: sodium gluconate and borax in a mass ratio of 1:1.5, 0.1kg of thixotropic lubricant and 1kg of anti-cracking agent were added to the mixer in sequence for dry mixing, the stirring speed was set to 80r / min, the stirring time was 5min, and a high ductility concrete premix was obtained;

[0054] S2011. Mixing sodium silicate and wood fiber in a blender at a mass ratio of 1:1 at 20°C for 20 min to obtain a preliminary mixture;

[0055] S2012. Adding starch grafted sodium acrylate and cellulose ether in an amount equal to the mass of sodium silicate to the preliminary mixture, stirring was continued at 80° C. for 15 min to obtain a modified composite curing agent;

[0056] S202. Add 22kg of water and 0.3kg of the prepared modified composite curing agent to the high ductility concrete premix and stir thoroughly, first at a stirring speed of 80r / min for 3min, then at a stirring speed of 120r / min for 2min to obtain a uniform mixture;

[0057] S2021. The polyacrylate dispersant and anhydrous ethanol are mixed in a mass ratio of 1:1.5 and stirred to obtain a solvent containing a dispersant;

[0058] S2022. 20% of the mass of the polyacrylate dispersant and 25% of the carbon nanotubes were gradually added to the solvent containing the dispersant, stirred evenly, and then ultrasonically dispersed using an ultrasonic processor, the frequency was set to 80kHZ, and the ultrasonic treatment time was 5min to obtain a nanosuspension;

[0059] S2023. The nano suspension is filtered through a filter membrane to remove undispersed particles and impurities to obtain a pure modified nanomaterial mixture, which is then placed in a vacuum drying oven, dried at 120° C. for 30 min, and then pulverized to obtain a modified nanomaterial;

[0060] S203. Evenly add 0.07kg of modified nanomaterials and 1.2kg of polymer fibers into the uniformly stirred mixture, set the stirring speed to 120r / min, and set the stirring time to 5min to obtain moisture-retaining, crack-resistant, and highly ductile concrete, which is then poured into the prepared mold for molding. During the molding process, the concrete needs to be vibrated on a vibration table, compacted and smoothed, and cured after demolding for 24 hours. The curing temperature is 22°C and the curing humidity is 99%.

[0061] Example 3

[0062] S301. 38kg of ordinary Portland cement, 23kg of fly ash, 3.5kg of silica fume, 28.5kg of quartz sand, 0.06kg of water reducer: polycarboxylate water reducer, 1.2kg of expansion agent: calcium magnesium composite expansion agent, 0.02kg of retarder: sodium gluconate and borax in a mass ratio of 1:1.2, 0.06kg of thixotropic lubricant and 0.6kg of anti-cracking agent were added to the mixer in sequence for dry mixing, the stirring speed was set to 65r / min, the stirring time was 3.5min, and a high ductility concrete premix was obtained;

[0063] S3011. Sodium silicate and wood fiber were mixed in a mixer at a mass ratio of 1:1 at 20° C. for 16 min to obtain a preliminary mixture;

[0064] S3012. Add starch grafted sodium acrylate and cellulose ether in an amount equal to the mass of sodium silicate to the preliminary mixture, and continue stirring at 65° C. for 11 minutes to obtain a modified composite curing agent;

[0065] S302. 19kg of water and 0.1kg of the prepared modified composite curing agent were added to the high ductility concrete premix and stirred thoroughly, first at a stirring speed of 65r / min for 2.5min, then at a stirring speed of 105r / min for 1.5min to obtain a uniform mixture;

[0066] S3021. The polyacrylate dispersant and anhydrous ethanol are mixed in a mass ratio of 1:1.1 and stirred to obtain a solvent containing a dispersant;

[0067] S3022. 16% of the mass of the polyacrylate dispersant and 21% of the carbon nanotubes were gradually added to the solvent containing the dispersant, stirred evenly, and then ultrasonically dispersed using an ultrasonic processor, the frequency was set to 72kHZ, and the ultrasonic treatment time was 3.5min to obtain a nanosuspension;

[0068] S3023. The nano suspension is filtered through a filter membrane to remove undispersed particles and impurities to obtain a pure modified nanomaterial mixture, which is then placed in a vacuum drying oven, dried at 105° C. for 26 min, and then pulverized to obtain a modified nanomaterial;

[0069] S303. Evenly add 0.03kg of modified nanomaterials and 0.6kg of polymer fibers into the uniformly stirred mixture, set the stirring speed to 105r / min, and set the stirring time to 3.5min to obtain moisture-retaining, crack-resistant, and highly ductile concrete, which is then poured into the prepared mold for molding. During the molding process, the concrete needs to be vibrated on a vibration table, compacted and smoothed, and cured after demolding for 24 hours. The curing temperature is 19°C and the curing humidity is 96%.

[0070] Example 4

[0071] S401. 41kg of ordinary Portland cement, 25kg of fly ash, 4kg of silica fume, 31kg of quartz sand, 0.07kg of water reducer: polycarboxylate water reducer, 1.6kg of expansion agent: calcium magnesium composite expansion agent, 0.02kg of retarder: sodium gluconate and borax in a mass ratio of 1:1.3, 0.07kg of thixotropic lubricant and 0.7kg of anti-cracking agent were added to the mixer in sequence for dry mixing, the stirring speed was set to 70r / min, the stirring time was 4min, and a high ductility concrete premix was obtained;

[0072] S4011. Sodium silicate and wood fiber were mixed in a mixer at a mass ratio of 1:1 at a temperature of 19° C. for 17 min to obtain a preliminary mixture;

[0073] S4012. Adding starch grafted sodium acrylate and cellulose ether in an amount equal to the mass of sodium silicate to the preliminary mixture, stirring was continued at 70° C. for 13 min to obtain a modified composite curing agent;

[0074] S402. Add 20kg of water and 0.18kg of the prepared modified composite curing agent to the high ductility concrete premix and stir thoroughly, first at a stirring speed of 70r / min for 2.5min, then at a stirring speed of 110r / min for 1.5min to obtain a uniformly stirred mixture;

[0075] S4021. The polyacrylate dispersant and anhydrous ethanol are mixed in a mass ratio of 1:1.2 and stirred to obtain a solvent containing a dispersant;

[0076] S4022. 17% of the mass of the polyacrylate dispersant and 23% of the carbon nanotubes were gradually added to the solvent containing the dispersant, stirred evenly, and then ultrasonically dispersed using an ultrasonic processor, the frequency was set to 75kHZ, and the ultrasonic treatment time was 4min to obtain a nanosuspension;

[0077] S4023. The nano suspension is filtered through a filter membrane to remove undispersed particles and impurities to obtain a pure modified nanomaterial mixture, which is then placed in a vacuum drying oven, dried at 110° C. for 27 min, and then pulverized to obtain a modified nanomaterial;

[0078] S403. Evenly add 0.05kg of modified nanomaterials and 1kg of polymer fibers into the uniformly stirred mixture, set the stirring speed to 110r / min, and set the stirring time to 4min to obtain moisture-retaining, crack-resistant, and highly ductile concrete, which is then poured into the prepared mold for molding. During the molding process, the concrete needs to be vibrated on a vibration table, compacted and smoothed, and cured after demolding for 24 hours. The curing temperature is 20°C and the curing humidity is 97%.

[0079] Example 5

[0080] S501. 43kg of ordinary Portland cement, 28kg of fly ash, 4.5kg of silica fume, 33kg of quartz sand, 0.09kg of water reducer: polycarboxylate water reducer, 1.9kg of expansion agent: calcium magnesium composite expansion agent, 0.02kg of retarder: sodium gluconate and borax in a mass ratio of 1:1.4, 0.09kg of thixotropic lubricant and 0.9kg of anti-cracking agent were added to the mixer in sequence for dry mixing, the stirring speed was set to 75r / min, the stirring time was 4.5min, and a high ductility concrete premix was obtained;

[0081] S5011. Sodium silicate and wood fiber were mixed in a mixer at a mass ratio of 1:1 at a temperature of 19° C. for 19 min to obtain a preliminary mixture;

[0082] S5012. Add starch grafted sodium acrylate and cellulose ether in an amount equal to the mass of sodium silicate to the preliminary mixture, and continue stirring at 75° C. for 14 min to obtain a modified composite curing agent;

[0083] S502. Add 21kg of water and 0.25kg of the prepared modified composite curing agent to the high ductility concrete premix and stir thoroughly, first at a stirring speed of 75r / min for 2.5min, then at a stirring speed of 115r / min for 1.5min to obtain a uniform mixture;

[0084] S5021. The polyacrylate dispersant and anhydrous ethanol are mixed in a mass ratio of 1:1.4 and stirred to obtain a solvent containing a dispersant;

[0085] S5022. 18% of the mass of the polyacrylate dispersant and 24% of the carbon nanotubes were gradually added to the solvent containing the dispersant, stirred evenly, and then ultrasonically dispersed using an ultrasonic processor, the frequency was set to 78kHZ, and the ultrasonic treatment time was 4.5min to obtain a nanosuspension;

[0086] S5023. The nano suspension is filtered through a filter membrane to remove undispersed particles and impurities to obtain a pure modified nanomaterial mixture, which is then placed in a vacuum drying oven, dried at 115° C. for 29 min, and then pulverized to obtain a modified nanomaterial;

[0087] S503. Evenly add 0.06kg of modified nanomaterials and 1.1kg of polymer fibers into the uniformly stirred mixture, set the stirring speed to 115r / min, and set the stirring time to 4.5min to obtain moisture-retaining, crack-resistant, and highly ductile concrete, which is then poured into the prepared mold for molding. During the molding process, the concrete needs to be vibrated on a vibration table, compacted and smoothed, and cured after demolding for 24 hours. The curing temperature is 21°C and the curing humidity is 98%.

[0088] Comparative Example 1

[0089] S101. 35kg of ordinary Portland cement, 20kg of fly ash, 3kg of silica fume, 25kg of quartz sand, 0.05kg of water reducer: polycarboxylate water reducer, 1kg of expansion agent: calcium magnesium composite expansion agent, 0.01kg of retarder: sodium gluconate and borax in a mass ratio of 1:1, 0.05kg of thixotropic lubricant and 0.5kg of anti-cracking agent were added to the mixer in sequence for dry mixing, the stirring speed was set to 60r / min, the stirring time was 3min, and a high ductility concrete premix was obtained;

[0090] S102. 18kg of water and 0.07kg of Subot Ereducer-301 concrete curing agent were added to the high ductility concrete premix and stirred thoroughly. The mixture was stirred at a stirring speed of 60r / min for 2min and then at a stirring speed of 100r / min for 1min to obtain a uniform mixture.

[0091] S1021. The polyacrylate dispersant and anhydrous ethanol are mixed in a mass ratio of 1:1 and stirred to obtain a solvent containing a dispersant;

[0092] S1022. 15% of the mass of the polyacrylate dispersant and 20% of the carbon nanotubes were gradually added to the solvent containing the dispersant, stirred evenly, and then ultrasonically dispersed using an ultrasonic processor, the frequency was set to 70kHZ, and the ultrasonic treatment time was 3min to obtain a nanosuspension;

[0093] S1023. The nano suspension is filtered through a filter membrane to remove undispersed particles and impurities to obtain a pure modified nanomaterial mixture, which is then placed in a vacuum drying oven, dried at 100° C. for 25 min, and then pulverized to obtain a modified nanomaterial;

[0094] S103. Evenly add 0.02kg of modified nanomaterials and 0.5kg of polymer fibers into the uniformly stirred mixture, set the stirring speed to 100r / min, and set the stirring time to 3min to obtain moisture-retaining, crack-resistant, and highly ductile concrete, which is then poured into the prepared mold for molding. During the molding process, the concrete needs to be vibrated on a vibration table, compacted and smoothed, and cured after demolding for 24 hours. The curing temperature is 18°C ​​and the curing humidity is 95%.

[0095] Comparative Example 2

[0096] S101. 35kg of ordinary Portland cement, 20kg of fly ash, 3kg of silica fume, 25kg of quartz sand, 0.05kg of water reducer: polycarboxylate water reducer, 1kg of expansion agent: calcium magnesium composite expansion agent, 0.01kg of retarder: sodium gluconate and borax in a mass ratio of 1:1, 0.05kg of thixotropic lubricant and 0.5kg of anti-cracking agent were added to the mixer in sequence for dry mixing, the stirring speed was set to 60r / min, the stirring time was 3min, and a high ductility concrete premix was obtained;

[0097] S1011. Mixing sodium silicate and wood fiber in a blender at a mass ratio of 1:1 at 18° C. for 15 min to obtain a preliminary mixture;

[0098] S1012. Adding starch-grafted sodium acrylate and cellulose ether in an amount equal to the mass of sodium silicate to the preliminary mixture, stirring was continued at 60° C. for 10 min to obtain a modified composite curing agent;

[0099] S102. Add 18kg of water and 0.07kg of the prepared modified composite curing agent to the high ductility concrete premix and stir thoroughly, first at a stirring speed of 60r / min for 2min, then at a stirring speed of 100r / min for 1min to obtain a uniformly stirred mixture;

[0100] S103. Evenly add 0.01kg nano silicon powder, 0.01kg carbon nanotubes and 0.5kg polymer fibers into the uniformly stirred mixture, set the stirring speed to 100r / min, set the stirring time to 3min, and obtain moisture-retaining, crack-resistant and highly ductile concrete, which is then poured into the prepared mold for molding. During the molding process, the concrete needs to be vibrated on a vibration table, and then compacted and smoothed. After demolding for 24 hours, it is cured at a temperature of 18°C ​​and a humidity of 95%.

[0101] Performance Test:

[0102] Comparative Example 1 replaces the modified composite curing agent with a conventional curing agent compared to Example 1. Comparative Example 2 omits the modification process of nano silicon powder and carbon nanotubes compared to Example 1, and directly adds them to the stirred mixture for comparison with Example 1. The moisture-retaining, crack-resistant, high-ductility concrete prepared in the above Examples 1-5 and Comparative Examples 1-2 was tested for performance according to JC / T 2461 "Test Method for Mechanical Properties of High-ductility Fiber Reinforced Cement-based Composite Materials", and the results are shown in Tables 1-3 below:

[0103] Table 1 60d strength of moisture-retaining and crack-resistant high-ductility concrete

[0104]

[0105] Table 2 Equivalent bending toughness and equivalent bending strength of moisture-retaining and crack-resistant high-ductility concrete

[0106]

[0107] Table 3 Number of cracks within the gauge length, average crack spacing and average crack width of moisture-retaining and crack-resistant high-ductility concrete

[0108]

[0109] From the data comparison between Example 1 and Comparative Example 2 in Table 1, it can be seen that the modified nanomaterial can significantly improve the cubic compressive strength and ultimate tensile strength of the moisture-retaining and crack-resistant high-ductility concrete. This is because the nano-silicon powder can effectively fill the gaps between cement particles and the tiny pores and microcracks inside the high-ductility concrete. This filling effect significantly reduces the porosity of the high-ductility concrete, improves the density and homogeneity, and thus enhances the compressive strength of the high-ductility concrete. In addition, the nano-silicon powder also has a high volcanic ash activity and can react chemically with the calcium hydroxide produced during the cement hydration process to generate additional calcium silicate gel (CSH). These newly generated calcium silicate gel particles will be evenly dispersed in the cement paste, further filling the pores and microcracks, improving the density and enhancing the compressive strength of the high-ductility concrete. Carbon nanotubes have extremely high specific strength and specific modulus, and their tensile strength can reach 200GPa. The addition of carbon nanotubes can significantly improve the strength and toughness of high-ductility concrete, and enhance its tensile strength, compressive strength and impact resistance. In addition, carbon nanotubes can also weaken the microcracks caused by the shrinkage of cement-based materials through bridging, inhibit the invasion of harmful media, and improve durability.

[0110] Polymer fibers can significantly increase the ultimate elongation of moisture-retaining, crack-resistant, high-ductility concrete and improve its toughness. Ultra-high molecular weight polyethylene fibers have extremely high strength and modulus. When added to high-ductility concrete, these fibers can form a three-dimensional mesh structure inside the matrix. This structure can effectively transfer and disperse stress, so that when the matrix is ​​subjected to external loads, the stress can be more evenly distributed throughout the material, rather than concentrated in a local area. When cracks appear in the high-ductility concrete matrix, polyethylene fibers can span the cracks and act as a bridge to prevent further expansion of the cracks, which can significantly improve the tensile strength.

[0111] From the data comparison of Example 1 and Comparative Example 1 in Table 1, it can be seen that the modified composite curing agent can effectively improve the compressive and tensile strength of the moisture-retaining and crack-resistant high-ductility concrete. Sodium silicate can react with calcium hydroxide in the high-ductility concrete matrix to produce hydrated calcium silicate gel with water-retaining properties, thereby filling the pores inside the matrix, improving the density of the matrix, and thus improving its compressive and tensile strength. At the same time, the modified composite curing agent has an excellent water-retaining effect. During the period of strength growth of the high-ductility concrete, the water required for the cement hydration reaction can be replenished in time, the degree of cement hydration can be improved, the density and durability of the matrix can be improved, and the mechanical properties of the matrix can be improved.

[0112] Combining the experimental data in Table 1 with Table 2, it can be seen that the cube compressive strength is directly related to the peak load in the toughness test of the moisture-retaining and crack-resistant high-ductility concrete. When the polymer fiber content is the same, the higher the peak load, the smaller the μ0.85 deflection value, the matrix ductility is slightly reduced, but the equivalent bending strength is improved to a certain extent. The increase in the polymer fiber content can significantly improve the μ0.85 deflection value and equivalent bending toughness of high-ductility concrete. This is because when the high-ductility concrete is subjected to load, the polymer fiber can absorb and dissipate a large amount of energy through its high toughness and high elastic modulus, which helps to reduce stress concentration and damage inside the concrete.

[0113] It can be seen from Table 3 that the anti-cracking agent and polymer fiber can increase the number of cracks within the gauge length and improve the ductility of the matrix to a certain extent.

[0114] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A moisture-retaining, crack-resistant, high-ductility concrete, characterized in that: The following components are included in parts by mass: 350-450 parts of ordinary Portland cement, 200-300 parts of fly ash, 30-50 parts of silica fume, 250-350 parts of quartz sand, 0.5-1 parts of water reducer, 10-20 parts of expansion agent, 0.1-0.3 parts of retarder, 0.5-1 parts of thixotropic lubricant, 0.2-0.7 parts of modified nanomaterial, 0.7-3 parts of modified composite curing agent, 5-10 parts of anti-cracking agent, 5-12 parts of polymer fiber, and 180-220 parts of water; Wherein, the modified composite curing agent is prepared by the following steps: S11. Mixing sodium silicate and wood fiber in a blender at a mass ratio of 1:1 at a temperature of 18-20° C. for 15-20 min to obtain a preliminary mixture; S12. Adding starch grafted sodium acrylate and cellulose ether in an amount equal to the mass of sodium silicate to the preliminary mixture, stirring was continued at 60-80°C for 10-15min to obtain a modified composite curing agent; The modified nanomaterial is prepared by the following steps: S21. The polyacrylate dispersant and anhydrous ethanol are mixed in a mass ratio of 1:1-1.5 and stirred to obtain a solvent containing a dispersant; S22. The mass of 15-20% of nano-silicon powder and 20-25% of carbon nanotubes of a polyacrylate dispersant was gradually added to a solvent containing a dispersant, stirred evenly, and then ultrasonically dispersed using an ultrasonic processor at a frequency of 70-80kHZ for 3-5min to obtain a nanosuspension; S23. Filter the nano suspension through a filter membrane to remove undispersed particles and impurities to obtain a pure modified nano material mixture, and then place it in a vacuum drying oven, dry it at 100-120°C for 25-30 minutes, and then crush it to obtain the modified nano material.

2. The moisture-retaining, crack-resistant, high-ductility concrete according to claim 1, characterized in that: During the preparation of the modified composite curing agent, the stirring speed is 60-80r / min.

3. The moisture-retaining, crack-resistant, high-ductility concrete according to claim 1, characterized in that: During the preparation of the modified nanomaterials, the stirring speed is 250-300 r / min.

4. The moisture-retaining, crack-resistant, high-ductility concrete according to claim 1, characterized in that: The water reducer is a polycarboxylate water reducer.

5. The moisture-retaining, crack-resistant, high-ductility concrete according to claim 1, characterized in that: The expansion agent is a calcium-magnesium composite expansion agent.

6. The moisture-retaining, crack-resistant, high-ductility concrete according to claim 1, characterized in that: The polymer fiber is an ultra-high molecular weight synthetic fiber.

7. The moisture-retaining, crack-resistant, high-ductility concrete according to claim 1, characterized in that: The retarder comprises sodium gluconate and borax in a mass ratio of 1:1-1.

5.

8. A method for preparing a moisture-retaining, crack-resistant, high-ductility concrete, for preparing a moisture-retaining, crack-resistant, high-ductility concrete according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Ordinary Portland cement, fly ash, silica fume, quartz sand, water reducer, expansion agent, retarder, thixotropic lubricant and anti-cracking agent were sequentially added to the mixer for dry mixing, the stirring speed was set to 60-80r / min, the stirring time was 3-5min, and a high ductility concrete premix was obtained; S2. Add water and the prepared modified composite curing agent to the high ductility concrete premix and stir thoroughly, first at a stirring speed of 60-80r / min for 2-3min, then at a stirring speed of 100-120r / min for 1-2min to obtain a uniformly stirred mixture; S3. The modified nanomaterials and polymer fibers are evenly added to the uniformly stirred mixture, the stirring speed is set to 100-120 r / min, and the stirring time is set to 3-5 min to obtain a moisture-retaining, crack-resistant, high-ductility concrete.

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