Road and bridge heavy-load-resistant concrete and preparation method thereof

Abstract

The application discloses a kind of road bridge heavy load resistance concrete and preparation method thereof, it is related to concrete technical technical field, belongs to patent classification number C04B28 / 00.Concrete preparation method is first polypropylene fiber is immersed and activated by potassium permanganate acid solution, then is treated with aminopropyl triethoxysilane, interface modification fiber is obtained, the interface modification fiber is made into suspension, mixed with the premix liquid of nanometer silicon dioxide containing aqueous epoxy resin emulsion, carries out reaction and obtains fiber reinforced composite material, metakaolin is mixed with silica fume, adds aqueous polyurethane, carboxylated multi-walled carbon nanotube high-speed shearing, spray drying is obtained interface enhancement microsphere, finally cement, machine-made sand, granite crushed stone, mineral powder and fiber reinforced material dry mixing, add polycarboxylic acid water reducing agent solution high-speed stirring, then add microsphere medium-speed stirring, the concrete is obtained.The concrete prepared by the application has excellent mechanical strength, thereby realizing heavy load resistance performance.

Description

Technical Field

[0001] This invention relates to the field of concrete technology and belongs to patent classification number C04B28 / 00, specifically to a heavy-load resistant concrete for road and bridge construction and its preparation method. Background Technology

[0002] With the rapid development of the marine economy and cross-sea transportation construction, the demand for marine road and bridge projects (such as cross-sea bridges and connecting bridges for submarine tunnels) is increasing. These projects operate in marine environments with high salt spray and high humidity for extended periods and must withstand continuous or intermittent heavy loads from heavy vehicles and construction machinery, placing stringent requirements on the mechanical properties and structural stability of concrete materials.

[0003] Currently, marine cement is widely used in offshore road and bridge projects to prepare concrete, initially meeting the basic durability requirements of the marine environment. However, existing concrete formulation designs based on marine cement often focus more on optimizing durability properties such as resistance to chloride ion attack and freeze-thaw cycles, lacking sufficient specificity for the core requirements of heavy loads. This results in the compressive strength, flexural strength, and fatigue resistance of the concrete failing to fully match the actual engineering needs. Specifically, under long-term heavy loads, concrete structures are prone to early cracking, surface spalling, and accumulation of internal micro-damage, which not only shortens the service life of offshore road and bridges but also significantly increases later maintenance costs and safety risks. Summary of the Invention

[0004] The purpose of this invention is to provide a heavy-load resistant concrete for road and bridge construction and its preparation method, thereby addressing the technical problem of insufficient mechanical strength in marine cement concrete mentioned in the background art. The concrete prepared by this invention possesses excellent mechanical strength, thus achieving heavy-load resistance.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for preparing heavy-load resistant concrete for road and bridge construction, characterized by comprising the following steps:

[0007] S1. Polypropylene fibers are impregnated in an acidic potassium permanganate solution, and after washing and drying, surface-activated fibers are obtained. The surface-activated fibers are then immersed in a γ-aminopropyltriethoxysilane solution for reaction, and after filtration and drying, interface-modified fibers are obtained.

[0008] S2. Add the interface-modified fiber to water and stir to disperse it evenly to obtain a suspension; disperse nano-silica in waterborne epoxy resin emulsion, then add the above suspension, stir evenly, then add triethylenediamine, heat to react, filter and dry to obtain fiber-reinforced composite material.

[0009] S3. The composite mineral powder is obtained by ball milling metakaolin and silica fume together. The composite mineral powder is mixed with water and stirred into a slurry. Aqueous polyurethane emulsion and carboxylated multi-walled carbon nanotube dispersion are added. After high-speed shear dispersion, a mixed slurry is obtained. After spray drying, interface-reinforced microspheres are obtained.

[0010] S4. Dry-mix silicate cement, manufactured sand, granite crushed stone, mineral powder and fiber-reinforced composite material together; add polycarboxylate superplasticizer and water to form a solution and add it to the mixer, and obtain fresh cement mortar by high-speed mixing; finally add interface-reinforced microspheres and obtain heavy-load concrete for road and bridge after medium-speed mixing.

[0011] In this invention, the mechanical strength of the road and bridge is improved from two aspects, thereby enhancing its resistance to heavy loads. Firstly, a fiber-reinforced system is constructed to fundamentally improve the toughness and crack resistance of concrete, enabling it to withstand the enormous stress and impact generated by heavy loads. Specifically, polypropylene fibers are oxidized using a potassium permanganate acidic solution, introducing active functional groups such as hydroxyl and carboxyl groups onto their inert surface. Then, γ-aminopropyltriethoxysilane is used as a molecular bridge; the silanol group at one end condenses with the active groups on the fiber surface, while the amino group at the other end reacts with the subsequent epoxy resin, thus establishing a strong chemical bond between the fiber and the polymer coating layer, greatly improving the interfacial bonding force. Finally, an aqueous epoxy resin / nano silica hybrid coating layer is constructed on the fiber surface. After curing, the epoxy resin forms a tough, continuous phase, imparting excellent adhesion and toughness, while the nano silica particles act as rigid reinforcement points, further enhancing the hardness, wear resistance, and mechanical interlocking force with the cement matrix of the coating layer. Figure 1 The SEM image of the fiber-reinforced composite material prepared in this invention shows that the fiber surface exhibits a rough microstructure. After this modification, when the fibers are uniformly dispersed in concrete, they can not only effectively inhibit the initiation of microcracks, but also cross cracks. Through their high tensile strength and strong interfacial bond with the matrix, they can disperse and transfer concentrated stress, dissipate fracture energy, and thus significantly improve the ultimate flexural strength, impact toughness, and fatigue life of concrete, avoiding the brittle failure commonly seen in heavy-load road bridges.

[0012] On the other hand, the organic-inorganic synergistic effect enhances the density and integrity of the matrix, thereby optimizing load transfer efficiency. Specifically, metakaolin and silica fume were combined by ball milling to obtain mineral powders with ultra-high specific surface area and volcanic ash activity. These active minerals were then blended with waterborne polyurethane emulsion and carboxylated carbon nanotubes through high-speed shearing. The waterborne polyurethane served as the organic binder and toughening phase, and the active groups on its molecular chains could react with the hydroxyl groups on the mineral surface and cement hydration products. The carbon nanotubes served as nano-reinforcing fibers, embedded within the material due to their large specific surface area and strength. After spray drying, functionally integrated microspheres were formed. When microspheres are incorporated into concrete, they react in the hydration environment: the mineral components undergo continuous pozzolanic reaction, consuming Ca(OH)2 to generate more CSH gel, significantly reducing the porosity of the interfacial transition zone and improving its density and hardness; simultaneously, waterborne polyurethane demulsifies, forms a film, and solidifies, synergistically with carbon nanotubes to form an organic-inorganic interpenetrating tough network within the interfacial transition zone. This network can efficiently bridge microcracks, disperse stress concentration, and significantly improve the bond strength between aggregates and cement paste. This multi-layered synergistic effect, from chemical densification to physical toughening, allows the load to be transferred more evenly and effectively throughout the system when concrete is subjected to heavy loads, reducing local stress concentration and thus exhibiting higher compressive strength, flexural strength, and excellent durability.

[0013] Preferably, in step S1, the concentration of the acidic potassium permanganate solution is 0.05–0.1 mol / L.

[0014] Preferably, the polypropylene fiber is impregnated in an acidic potassium permanganate solution for 10 to 20 minutes.

[0015] Preferably, in step S2, the amount of nano-silica added is 10-15 wt% of the aqueous epoxy resin emulsion.

[0016] Preferably, in step S2, the reaction temperature is 65-70°C and the reaction time is 2-3 hours.

[0017] Preferably, in step S3, the mass ratio of metakaolin to silica fume is 10:3 to 6.

[0018] Preferably, in step S3, the mass ratio of the composite mineral powder to the waterborne polyurethane emulsion is 6:1 to 2.

[0019] Preferably, in step S4, the fiber-reinforced composite material is pretreated by immersing it in potassium silicate for impregnation, followed by filtration and heat curing.

[0020] In the technical solution of this invention, the team discovered through in-depth research that metakaolin and silica fume, as highly active mineral admixtures, greatly accelerate the hydration reaction and continuously consume calcium hydroxide, breaking the chemical balance of the hydration system. This causes cement minerals to continuously dissolve to replenish calcium ions and hydroxide ions, thereby maintaining the ultra-high alkalinity of the pore fluid for a long time. The strong alkaline environment will attack the polymer coating on the fiber surface, causing the polymer molecular chains to break, ultimately losing the protection and toughening effect on the fiber, thus weakening the improvement effect of fiber-reinforced composite materials on the mechanical strength of concrete. To address this technical problem, this invention further processes the fiber-reinforced composite material. After impregnation with potassium silicate solution, the fibers decompose during the heating and curing process, forming a dense inorganic silicate gel protective layer on the surface and shallow layer of the epoxy resin coating. This silicate gel is essentially homologous to the cement hydration environment and possesses excellent alkali resistance. It effectively blocks the direct contact and erosion of the internal organic epoxy resin by high concentrations of hydroxide and calcium ions in the cement pore liquid, thereby significantly delaying its hydrolytic degradation process. Simultaneously, this inorganic layer exhibits excellent chemical compatibility and adhesion to the cement matrix, not only preventing its own corrosion but also further enhancing the interfacial bonding between the fiber and concrete, thus ensuring its long-term durability in harsh alkaline environments.

[0021] Preferably, the mass concentration of the potassium silicate is 3-5%.

[0022] A type of heavy-load resistant concrete for road and bridge construction is prepared by the method described above.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] (1) By modifying the surface and constructing an epoxy resin / nano silica hybrid coating layer on the fiber surface, the interfacial bonding force between the fiber and the concrete matrix is ​​greatly enhanced, which significantly improves the tensile strength, flexural strength, impact toughness and fatigue life of the concrete, and can effectively inhibit the generation and propagation of cracks.

[0025] (2) The active mineral powders (metakaolin, silica fume) in the interface-enhanced microspheres undergo a pozzolanic reaction to chemically fill the pores; at the same time, waterborne polyurethane and carbon nanotubes form an organic-inorganic interpenetrating network, which physically toughens the microspheres. The two work synergistically to significantly reduce porosity and improve density, hardness and load transfer efficiency.

[0026] (3) By subjecting the fiber-reinforced composite material to potassium silicate post-treatment, an alkali-resistant inorganic protective layer is formed on its surface, which effectively blocks the erosion of organic resin by the high-alkali environment of concrete, solves the problem of easy hydrolysis and deterioration of the coating layer caused by high-activity mineral admixture, and thus ensures the long-term stability of the reinforcement effect. Attached Figure Description

[0027] Figure 1This is a SEM image of the surface of the fiber-reinforced composite material prepared in this invention. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] A method for preparing heavy-load resistant concrete for road and bridge construction includes the following steps:

[0031] Step 1: Weigh 10.0g of polypropylene fiber (12mm in length) and place it in a beaker. Prepare 600mL of a 0.08mol / L acidic potassium permanganate solution (obtained by dissolving potassium permanganate in sulfuric acid solution). Pour the solution into the beaker to completely submerge the fiber under a constant temperature water bath at 35℃. Turn on the magnetic stirrer and react at a constant temperature of 200 rpm for 15 minutes. After the reaction is complete, filter the mixture and wash the filter cake repeatedly with deionized water until the effluent is neutral. Transfer the washed fiber to a 70℃ forced-air drying oven and dry for 120 minutes to obtain activated polypropylene fiber.

[0032] Prepare 300 mL of a 2% γ-aminopropyltriethoxysilane ethanol solution, adjust the pH of the solution to 5.0 using glacial acetic acid, and then pour it into a beaker to ensure that the fibers are completely submerged. Place the beaker in an ultrasonic cleaner and treat it at 50℃ and 300W for 35 min. After treatment, filter the solution and transfer the resulting fibers to a 100℃ forced-air drying oven for curing for 60 min to obtain interface-modified fibers.

[0033] Step 2: Place 10.0g of interface-modified fiber in a three-necked flask, add 400mL of deionized water, and start a mechanical stirrer at 300r / min to disperse it evenly, obtaining a suspension. In another beaker, weigh 50.0g of aqueous epoxy resin emulsion (50% solid content), and slowly add 6.5g of nano-silica under stirring in a high-speed shear disperser (10000 rpm), continuing shear dispersion for 30min to obtain a uniform and stable nano-SiO2 / epoxy resin premix. Slowly pour this premix into the suspension in the three-necked flask, maintaining stirring at 300r / min for 30min to mix evenly. Then add 1.0g of triethylenediamine catalyst, raise the reaction system to 68℃, and continue stirring at this temperature for 2.5h. After the reaction is complete, filter the mixture, transfer the fiber to a 100℃ vacuum drying oven, and dry to constant weight to obtain the fiber-reinforced composite material.

[0034] 10.0 g of fiber-reinforced composite material was immersed in 300 mL of a 4.5% potassium silicate aqueous solution for 10 min, with slight stirring during the process to ensure complete impregnation. Excess solution was then removed by suction filtration using a Buchner funnel. The filter cake was transferred to a 100°C forced-air drying oven for curing for 60 min, allowing potassium silicate to form a dense, alkali-resistant protective layer on the surface of the fiber coating, thus obtaining the pretreated fiber-reinforced composite material.

[0035] Step 3: Weigh 80.0g of metakaolin and 40g of silica fume, and place them together in a planetary ball mill. Mill at 350 rpm for 4 hours. After milling, a highly active composite mineral powder is obtained. Transfer 120.0g of the composite mineral powder to the hopper of a high-speed shear disperser, slowly add 200mL of deionized water, and initially stir at 1000 rpm for 5 minutes to form a uniform slurry. Then, add 35g of aqueous polyurethane emulsion (solid content approximately 50%) and 50.0g of a 2wt% carboxylated multi-walled carbon nanotube aqueous dispersion. Rapidly increase the shear speed to 5000 rpm and continuously shear disperse for 30 minutes to obtain a mixed slurry. Transfer the mixed slurry to the feed tank of a centrifugal spray dryer for spray drying to obtain interface-reinforced microspheres.

[0036] Step 4: Weigh 15.0 kg of 42.5R ordinary Portland cement, 30.0 kg of manufactured sand (medium sand, fineness modulus 2.8), 40.0 kg of granite crushed stone (5-20 mm continuous gradation), 4.8 kg of S95 grade mineral powder, and 100.0 g of pretreated fiber-reinforced composite material. Add all materials to a mixer and dry mix at low speed (15 r / min) for 3 minutes. Weigh 1.2 kg of polycarboxylate-based high-performance water-reducing agent (20% solid content) and 6.8 kg of water into a beaker, mix thoroughly to prepare a water-reducing agent solution. While the mixer continues to run at low speed, open the feed port and slowly pour in the water-reducing agent solution within 1 minute. Then increase the mixer speed to high speed (35 r / min) and mix for 5 minutes to obtain a freshly mixed cement mortar with good fluidity, uniformity, and no lumps. Finally, 80.0g of interface-enhanced microspheres were evenly added to the mixer through the feed port. The mixer speed was then adjusted to medium speed (25r / min), and the mixture was stirred for 4 minutes to obtain the final product.

[0037] Example 2

[0038] A method for preparing heavy-load resistant concrete for road and bridge construction includes the following steps:

[0039] Step 1: Weigh 10.0g of polypropylene fiber (12mm in length) and place it in a beaker. Prepare 600mL of a 0.08mol / L acidic potassium permanganate solution (obtained by dissolving potassium permanganate in sulfuric acid solution). Pour the solution into the beaker to completely submerge the fiber under a constant temperature water bath at 35℃. Turn on the magnetic stirrer and react at a constant temperature of 200 rpm for 15 minutes. After the reaction is complete, filter the mixture and wash the filter cake repeatedly with deionized water until the effluent is neutral. Transfer the washed fiber to a 70℃ forced-air drying oven and dry for 120 minutes to obtain activated polypropylene fiber.

[0040] Prepare 300 mL of a 2% γ-aminopropyltriethoxysilane ethanol solution, adjust the pH of the solution to 5.0 using glacial acetic acid, and then pour it into a beaker to ensure that the fibers are completely submerged. Place the beaker in an ultrasonic cleaner and treat it at 50℃ and 300W for 35 min. After treatment, filter the solution and transfer the resulting fibers to a 100℃ forced-air drying oven for curing for 60 min to obtain interface-modified fibers.

[0041] Step 2: Place 10.0g of interface-modified fiber in a three-necked flask, add 400mL of deionized water, and start a mechanical stirrer at 300r / min to disperse it evenly, obtaining a suspension. In another beaker, weigh 50.0g of aqueous epoxy resin emulsion (50% solid content), and slowly add 5.5g of nano-silica under stirring in a high-speed shear disperser (10000 rpm), continuing shear dispersion for 30min to obtain a uniform and stable nano-SiO2 / epoxy resin premix. Slowly pour this premix into the suspension in the three-necked flask, maintaining stirring at 300r / min for 30min to mix evenly. Then add 1.0g of triethylenediamine catalyst, raise the reaction system to 68℃, and continue stirring at this temperature for 2.5h. After the reaction is complete, filter the mixture, transfer the fiber to a 100℃ vacuum drying oven, and dry to constant weight to obtain the fiber-reinforced composite material.

[0042] 10.0 g of fiber-reinforced composite material was immersed in 300 mL of a 3.5% potassium silicate aqueous solution for 10 min, with slight stirring during the process to ensure complete impregnation. Excess solution was then removed by vacuum filtration using a Buchner funnel. The filter cake was transferred to a 100°C forced-air drying oven for curing for 60 min, allowing potassium silicate to form a dense, alkali-resistant protective layer on the surface of the fiber coating, thus obtaining the pretreated fiber-reinforced composite material.

[0043] Step 3: Weigh 80.0g of metakaolin and 30g of silica fume, and place them together in a planetary ball mill. Mill at 350 rpm for 4 hours. After milling, a highly active composite mineral powder is obtained. Transfer 120.0g of the composite mineral powder to the hopper of a high-speed shear disperser, slowly add 200mL of deionized water, and initially stir at 1000 rpm for 5 minutes to form a uniform slurry. Then, add 25g of aqueous polyurethane emulsion (solid content approximately 50%) and 50.0g of a 2wt% carboxylated multi-walled carbon nanotube aqueous dispersion. Rapidly increase the shear speed to 5000 rpm and continuously shear disperse for 30 minutes to obtain a mixed slurry. Transfer the mixed slurry to the feed tank of a centrifugal spray dryer for spray drying to obtain interface-reinforced microspheres.

[0044] Step 4: Weigh 15.0 kg of 42.5R ordinary Portland cement, 30.0 kg of manufactured sand (medium sand, fineness modulus 2.8), 40.0 kg of granite crushed stone (5-20 mm continuous gradation), 4.8 kg of S95 grade mineral powder, and 100.0 g of pretreated fiber-reinforced composite material. Add all materials to a mixer and dry mix at low speed (15 r / min) for 3 minutes. Weigh 1.2 kg of polycarboxylate-based high-performance water-reducing agent (20% solid content) and 6.8 kg of water into a beaker, mix thoroughly to prepare a water-reducing agent solution. While the mixer continues to run at low speed, open the feed port and slowly pour in the water-reducing agent solution within 1 minute. Then increase the mixer speed to high speed (35 r / min) and mix for 5 minutes to obtain a freshly mixed cement mortar with good fluidity, uniformity, and no lumps. Finally, 80.0g of interface-enhanced microspheres were evenly added to the mixer through the feed port. The mixer speed was then adjusted to medium speed (25r / min), and the mixture was stirred for 4 minutes to obtain the final product.

[0045] Example 3

[0046] A method for preparing heavy-load resistant concrete for road and bridge construction includes the following steps:

[0047] Step 1: Weigh 10.0g of polypropylene fiber (12mm in length) and place it in a beaker. Prepare 600mL of a 0.08mol / L acidic potassium permanganate solution (obtained by dissolving potassium permanganate in sulfuric acid solution). Pour the solution into the beaker to completely submerge the fiber under a constant temperature water bath at 35℃. Turn on the magnetic stirrer and react at a constant temperature of 200 rpm for 15 minutes. After the reaction is complete, filter the mixture and wash the filter cake repeatedly with deionized water until the effluent is neutral. Transfer the washed fiber to a 70℃ forced-air drying oven and dry for 120 minutes to obtain activated polypropylene fiber.

[0048] Prepare 300 mL of a 2% γ-aminopropyltriethoxysilane ethanol solution, adjust the pH of the solution to 5.0 using glacial acetic acid, and then pour it into a beaker to ensure that the fibers are completely submerged. Place the beaker in an ultrasonic cleaner and treat it at 50℃ and 300W for 35 min. After treatment, filter the solution and transfer the resulting fibers to a 100℃ forced-air drying oven for curing for 60 min to obtain interface-modified fibers.

[0049] Step 2: Place 10.0g of interface-modified fiber in a three-necked flask, add 400mL of deionized water, and start a mechanical stirrer at 300r / min to disperse it evenly, obtaining a suspension. In another beaker, weigh 50.0g of aqueous epoxy resin emulsion (50% solid content), and slowly add 6.0g of nano-silica under stirring in a high-speed shear disperser (10000 rpm), continuing shear dispersion for 30min to obtain a uniform and stable nano-SiO2 / epoxy resin premix. Slowly pour this premix into the suspension in the three-necked flask, maintaining stirring at 300r / min for 30min to mix evenly. Then add 1.0g of triethylenediamine catalyst, raise the reaction system to 68℃, and continue stirring at this temperature for 2.5h. After the reaction is complete, filter the mixture, transfer the fiber to a 100℃ vacuum drying oven, and dry to constant weight to obtain the fiber-reinforced composite material.

[0050] 10.0 g of fiber-reinforced composite material was immersed in 300 mL of a 4% potassium silicate aqueous solution for 10 min, with slight stirring during the process to ensure complete impregnation. Excess solution was then removed by suction filtration using a Buchner funnel. The filter cake was transferred to a 100°C forced-air drying oven for curing for 60 min, allowing potassium silicate to form a dense, alkali-resistant protective layer on the surface of the fiber coating, thus obtaining the pretreated fiber-reinforced composite material.

[0051] Step 3: Weigh 80.0g of metakaolin and 35g of silica fume, and place them together in a planetary ball mill. Mill at 350 rpm for 4 hours. After milling, a highly active composite mineral powder is obtained. Transfer 120.0g of the composite mineral powder to the hopper of a high-speed shear disperser, slowly add 200mL of deionized water, and initially stir at 1000 rpm for 5 minutes to form a uniform slurry. Then, add 30g of aqueous polyurethane emulsion (solid content approximately 50%) and 50.0g of a 2wt% carboxylated multi-walled carbon nanotube aqueous dispersion. Rapidly increase the shear speed to 5000 rpm and continuously shear disperse for 30 minutes to obtain a mixed slurry. Transfer the mixed slurry to the feed tank of a centrifugal spray dryer for spray drying to obtain interface-reinforced microspheres.

[0052] Step 4: Weigh 15.0 kg of 42.5R ordinary Portland cement, 30.0 kg of manufactured sand (medium sand, fineness modulus 2.8), 40.0 kg of granite crushed stone (5-20 mm continuous gradation), 4.8 kg of S95 grade mineral powder, and 100.0 g of pretreated fiber-reinforced composite material. Add all materials to a mixer and dry mix at low speed (15 r / min) for 3 minutes. Weigh 1.2 kg of polycarboxylate-based high-performance water-reducing agent (20% solid content) and 6.8 kg of water into a beaker, mix thoroughly to prepare a water-reducing agent solution. While the mixer continues to run at low speed, open the feed port and slowly pour in the water-reducing agent solution within 1 minute. Then increase the mixer speed to high speed (35 r / min) and mix for 5 minutes to obtain a freshly mixed cement mortar with good fluidity, uniformity, and no lumps. Finally, 80.0g of interface-enhanced microspheres were evenly added to the mixer through the feed port. The mixer speed was then adjusted to medium speed (25r / min), and the mixture was stirred for 4 minutes to obtain the final product.

[0053] Example 4

[0054] A method for preparing heavy-load resistant concrete for road and bridge construction includes the following steps:

[0055] Step 1: Weigh 10.0g of polypropylene fiber (12mm in length) and place it in a beaker. Prepare 600mL of a 0.10mol / L acidic potassium permanganate solution (obtained by dissolving potassium permanganate in sulfuric acid solution). Pour the solution into the beaker to completely submerge the fiber under a constant temperature water bath at 35℃. Turn on the magnetic stirrer and react at a constant temperature of 200 rpm for 10 minutes. After the reaction is complete, filter the mixture and wash the filter cake repeatedly with deionized water until the effluent is neutral. Transfer the washed fiber to a 70℃ forced-air drying oven and dry for 120 minutes to obtain activated polypropylene fiber.

[0056] Prepare 300 mL of a 2% γ-aminopropyltriethoxysilane ethanol solution, adjust the pH of the solution to 5.0 using glacial acetic acid, and then pour it into a beaker to ensure that the fibers are completely submerged. Place the beaker in an ultrasonic cleaner and treat it at 50℃ and 300W for 35 min. After treatment, filter the solution and transfer the resulting fibers to a 100℃ forced-air drying oven for curing for 60 min to obtain interface-modified fibers.

[0057] Step 2: Place 10.0g of interface-modified fiber in a three-necked flask, add 400mL of deionized water, and start a mechanical stirrer at 300r / min to disperse it evenly, obtaining a suspension. In another beaker, weigh 50.0g of aqueous epoxy resin emulsion (50% solid content), and slowly add 7.5g of nano-silica under stirring in a high-speed shear disperser (10000 rpm), continuing shear dispersion for 30min to obtain a uniform and stable nano-SiO2 / epoxy resin premix. Slowly pour this premix into the suspension in the three-necked flask, maintaining stirring at 300r / min for 30min to mix evenly. Then add 1.0g of triethylenediamine catalyst, raise the reaction system to 70℃, and continue stirring at this temperature for 3h. After the reaction is complete, filter the mixture, transfer the fiber to a 100℃ vacuum drying oven, and dry to constant weight to obtain the fiber-reinforced composite material.

[0058] 10.0 g of fiber-reinforced composite material was immersed in 300 mL of a 5% potassium silicate aqueous solution for 10 min, with slight stirring during the process to ensure complete impregnation. Excess solution was then removed by suction filtration using a Buchner funnel. The filter cake was transferred to a 100°C forced-air drying oven for curing for 60 min, allowing potassium silicate to form a dense, alkali-resistant protective layer on the surface of the fiber coating, thus obtaining the pretreated fiber-reinforced composite material.

[0059] Step 3: Weigh 80.0g of metakaolin and 48g of silica fume, and place them together in a planetary ball mill. Mill at 350 rpm for 4 hours. After milling, a highly active composite mineral powder is obtained. Transfer 120.0g of the composite mineral powder to the hopper of a high-speed shear disperser, slowly add 200mL of deionized water, and initially stir at 1000 rpm for 5 minutes to form a uniform slurry. Then, add 40g of aqueous polyurethane emulsion (solid content approximately 50%) and 50.0g of a 2wt% carboxylated multi-walled carbon nanotube aqueous dispersion. Rapidly increase the shear speed to 5000 rpm and continuously shear disperse for 30 minutes to obtain a mixed slurry. Transfer the mixed slurry to the feed tank of a centrifugal spray dryer for spray drying to obtain interface-reinforced microspheres.

[0060] Step 4: Weigh 15.0 kg of 42.5R ordinary Portland cement, 30.0 kg of manufactured sand (medium sand, fineness modulus 2.8), 40.0 kg of granite crushed stone (5-20 mm continuous gradation), 4.8 kg of S95 grade mineral powder, and 100.0 g of pretreated fiber-reinforced composite material. Add all materials to a mixer and dry mix at low speed (15 r / min) for 3 minutes. Weigh 1.2 kg of polycarboxylate-based high-performance water-reducing agent (20% solid content) and 6.8 kg of water into a beaker, mix thoroughly to prepare a water-reducing agent solution. While the mixer continues to run at low speed, open the feed port and slowly pour in the water-reducing agent solution within 1 minute. Then increase the mixer speed to high speed (35 r / min) and mix for 5 minutes to obtain a freshly mixed cement mortar with good fluidity, uniformity, and no lumps. Finally, 80.0g of interface-enhanced microspheres were evenly added to the mixer through the feed port. The mixer speed was then adjusted to medium speed (25r / min), and the mixture was stirred for 4 minutes to obtain the final product.

[0061] Example 5

[0062] A method for preparing heavy-load resistant concrete for road and bridge construction includes the following steps:

[0063] Step 1: Weigh 10.0g of polypropylene fiber (12mm in length) and place it in a beaker. Prepare 600mL of a 0.05mol / L acidic potassium permanganate solution (obtained by dissolving potassium permanganate in sulfuric acid solution). Pour the solution into the beaker to completely submerge the fiber under a constant temperature water bath at 35℃. Turn on the magnetic stirrer and react at a constant temperature of 200 rpm for 20 minutes. After the reaction is complete, filter the mixture and wash the filter cake repeatedly with deionized water until the effluent is neutral. Transfer the washed fiber to a 70℃ forced-air drying oven and dry for 120 minutes to obtain activated polypropylene fiber.

[0064] Prepare 300 mL of a 2% γ-aminopropyltriethoxysilane ethanol solution, adjust the pH of the solution to 5.0 using glacial acetic acid, and then pour it into a beaker to ensure that the fibers are completely submerged. Place the beaker in an ultrasonic cleaner and treat it at 50℃ and 300W for 35 min. After treatment, filter the solution and transfer the resulting fibers to a 100℃ forced-air drying oven for curing for 60 min to obtain interface-modified fibers.

[0065] Step 2: Place 10.0g of interface-modified fiber in a three-necked flask, add 400mL of deionized water, and start a mechanical stirrer at 300r / min to disperse it evenly, obtaining a suspension. In another beaker, weigh 50.0g of aqueous epoxy resin emulsion (50% solid content), and slowly add 5.0g of nano-silica under stirring in a high-speed shear disperser (10000 rpm), continuing shear dispersion for 30min to obtain a uniform and stable nano-SiO2 / epoxy resin premix. Slowly pour this premix into the suspension in the three-necked flask, maintaining stirring at 300r / min for 30min to mix evenly. Then add 1.0g of triethylenediamine catalyst, raise the reaction system to 65℃, and continue stirring at this temperature for 2h. After the reaction is complete, filter the mixture, transfer the fiber to a 100℃ vacuum drying oven, and dry to constant weight to obtain the fiber-reinforced composite material.

[0066] 10.0 g of fiber-reinforced composite material was immersed in 300 mL of a 3% potassium silicate aqueous solution for 10 min, with slight stirring during the process to ensure complete impregnation. Excess solution was then removed by suction filtration using a Buchner funnel. The filter cake was transferred to a 100°C forced-air drying oven for curing for 60 min, allowing potassium silicate to form a dense, alkali-resistant protective layer on the surface of the fiber coating, thus obtaining the pretreated fiber-reinforced composite material.

[0067] Step 3: Weigh 80.0g of metakaolin and 24g of silica fume, and place them together in a planetary ball mill. Mill at 350 rpm for 4 hours. After milling, a highly active composite mineral powder is obtained. Transfer 120.0g of the composite mineral powder to the hopper of a high-speed shear disperser, slowly add 200mL of deionized water, and initially stir at 1000 rpm for 5 minutes to form a uniform slurry. Then, add 20g of aqueous polyurethane emulsion (solid content approximately 50%) and 50.0g of a 2wt% carboxylated multi-walled carbon nanotube aqueous dispersion. Rapidly increase the shear speed to 5000 rpm and continuously shear disperse for 30 minutes to obtain a mixed slurry. Transfer the mixed slurry to the feed tank of a centrifugal spray dryer for spray drying to obtain interface-reinforced microspheres.

[0068] Step 4: Weigh 15.0 kg of 42.5R ordinary Portland cement, 30.0 kg of manufactured sand (medium sand, fineness modulus 2.8), 40.0 kg of granite crushed stone (5-20 mm continuous gradation), 4.8 kg of S95 grade mineral powder, and 100.0 g of pretreated fiber-reinforced composite material. Add all materials to a mixer and dry mix at low speed (15 r / min) for 3 minutes. Weigh 1.2 kg of polycarboxylate-based high-performance water-reducing agent (20% solid content) and 6.8 kg of water into a beaker, mix thoroughly to prepare a water-reducing agent solution. While the mixer continues to run at low speed, open the feed port and slowly pour in the water-reducing agent solution within 1 minute. Then increase the mixer speed to high speed (35 r / min) and mix for 5 minutes to obtain a freshly mixed cement mortar with good fluidity, uniformity, and no lumps. Finally, 80.0g of interface-enhanced microspheres were evenly added to the mixer through the feed port. The mixer speed was then adjusted to medium speed (25r / min), and the mixture was stirred for 4 minutes to obtain the final product.

[0069] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that steps 1 and 2 are omitted, that is, no pretreated fiber-reinforced composite material is added to the concrete.

[0070] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that the pretreated fiber-reinforced composite material is replaced with an equal mass of polypropylene fibers.

[0071] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that the fiber-reinforced composite material is not treated with potassium silicate.

[0072] Comparative Example 4: The difference between Comparative Example 4 and Example 1 is that step 3 is omitted, that is, no interface-reinforcing microspheres are added to the concrete.

[0073] Performance testing

[0074] 1. Compressive Strength Test: Referring to the "Standard for Test Methods of Physical and Mechanical Properties of Concrete" (GB / T 50081-2019), the concrete mixtures of each embodiment and comparative example were prepared into 150mm×150mm×150mm cubic specimens and cured for 28 days in a standard curing chamber at a temperature of (20±2)℃ and a relative humidity ≥95%. After curing, compressive strength tests were conducted using an electro-hydraulic servo pressure testing machine at a loading rate of (0.5±0.1) MPa / s. Three parallel specimens were tested in each group, and the arithmetic mean was taken as the final compressive strength value. The test results are shown in Table 1.

[0075] 2. Flexural Strength Test: Prismatic specimens measuring 40mm × 40mm × 160mm were prepared according to GB / T 50081-2019. After standard curing for 28 days, flexural strength tests were conducted on a universal testing machine using the three-point bending method. The support span was 100mm, and the loading rate was controlled at (0.05 ± 0.02) MPa / s. The maximum load at specimen fracture was recorded, and the flexural strength was calculated using the formula. Three specimens were tested in each group, and the average value was taken. The test results are shown in Table 1.

[0076] 3. Impact resistance test: Referring to the drop hammer impact test method in the "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete" (GB / T50082-2009), 100mm×100mm×400mm cuboid specimens were prepared. After standard curing for 28 days, impact tests were conducted using a drop hammer impact testing machine (drop hammer mass 10kg, drop distance 500mm). The impact energy (initial crack toughness) at the first visible crack appeared in the specimen was recorded. Five specimens were tested in each group, and the average value was taken. The test results are shown in Table 1.

[0077] 4. Long-term mechanical strength stability test: 150mm×150mm×150mm cubic specimens cured for 28 days were immersed in tap water for 180 days. After immersion, the specimens were removed, dried, and their compressive strength was tested. The ratio of the 180-day compressive strength to the 28-day compressive strength was calculated, which is the long-term mechanical strength retention rate. Three specimens were used in each group, and the average value was taken. The test results are shown in Table 1.

[0078] Table 1:

[0079]

[0080] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing heavy-load resistant concrete for road and bridge construction, characterized in that, Includes the following steps: S1. Polypropylene fibers are impregnated in an acidic potassium permanganate solution, and after washing and drying, surface-activated fibers are obtained. The surface-activated fibers are then immersed in a γ-aminopropyltriethoxysilane solution for reaction, and after filtration and drying, interface-modified fibers are obtained. S2. Add the interface-modified fiber to water and stir to disperse it evenly to obtain a suspension; disperse nano-silica in waterborne epoxy resin emulsion, then add the above suspension, stir evenly, then add triethylenediamine, heat to react, filter and dry to obtain fiber-reinforced composite material. S3. The composite mineral powder is obtained by ball milling metakaolin and silica fume together. The composite mineral powder is mixed with water and stirred into a slurry. Aqueous polyurethane emulsion and carboxylated multi-walled carbon nanotube dispersion are added. After high-speed shear dispersion, a mixed slurry is obtained. After spray drying, interface-reinforced microspheres are obtained. S4. Dry mix silicate cement, manufactured sand, granite crushed stone, mineral powder and fiber-reinforced composite material together; After preparing a solution of polycarboxylate superplasticizer and water, the solution is added to a mixer and stirred at high speed to obtain fresh cement mortar; finally, interface-reinforcing microspheres are added and stirred at medium speed to obtain heavy-load concrete for road and bridge construction.

2. The method for preparing heavy-load resistant concrete for road and bridge construction according to claim 1, characterized in that, In step S1, the concentration of the acidic potassium permanganate solution is 0.05–0.1 mol / L; The polypropylene fiber is immersed in an acidic potassium permanganate solution for 10 to 20 minutes.

3. The method for preparing heavy-load resistant concrete for road and bridge construction according to claim 1, characterized in that, In step S2, the amount of nano-silica added is 10-15 wt% of the aqueous epoxy resin emulsion.

4. The method for preparing heavy-load resistant concrete for road and bridge construction according to claim 1, characterized in that, In step S2, the reaction temperature is 65-70℃ and the reaction time is 2-3 hours.

5. The method for preparing heavy-load resistant concrete for road and bridge construction according to claim 1, characterized in that, In step S3, the mass ratio of metakaolin to silica fume is 10:3 to 6.

6. The method for preparing heavy-load resistant concrete for road and bridge construction according to claim 1, characterized in that, In step S3, the mass ratio of composite mineral powder to waterborne polyurethane emulsion is 6:1 to 2.

7. The method for preparing heavy-load resistant concrete for road and bridge construction according to claim 1, characterized in that, In step S4, the fiber-reinforced composite material undergoes pretreatment: the fiber-reinforced composite material is immersed in potassium silicate for impregnation, and then filtered and cured by heating to obtain the final product.

8. The method for preparing heavy-load resistant concrete for road and bridge construction according to claim 7, characterized in that, The mass concentration of potassium silicate is 3-5%.

9. A type of heavy-load resistant concrete for road and bridge construction, characterized in that, It is prepared by the method described in any one of claims 1-8.

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