Road and bridge heavy load resistant concrete and preparation method thereof

Abstract

The invention discloses road and bridge anti-heavy load concrete and a preparation method thereof, relates to the technical field of concrete technology, and belongs to the patent classification number C04B28 / 00. The preparation method of the concrete comprises the following steps: firstly, impregnating and activating polypropylene fibers with a potassium permanganate acid solution, then treating with aminopropyltriethoxysilane to obtain interface modified fibers, preparing a suspension from the interface modified fibers, mixing with a premixed solution of nano silicon dioxide containing a water-borne epoxy resin emulsion, and reacting to obtain a fiber reinforced composite material; the preparation method comprises the following steps: mixing metakaolin and silica fume, adding waterborne polyurethane and carboxylated multi-walled carbon nanotubes, carrying out high-speed shearing, carrying out spray drying to obtain interface reinforced microspheres, carrying out dry mixing on cement, machine-made sand, granite gravel, mineral powder and a fiber reinforced material, adding a polycarboxylic acid water reducer solution, carrying out high-speed stirring, adding the microspheres, and carrying out medium-speed stirring to obtain the concrete. The concrete prepared by the invention has excellent mechanical strength, so that the heavy load resistance is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete, belongs to the patent classification number C04B28 / 00, and specifically relates to a road and bridge heavy-load-resistant concrete and a preparation method thereof. BACKGROUND

[0002] With the rapid development of marine economy and cross-sea traffic construction, the construction demand of offshore road and bridge engineering (such as cross-sea bridges, seabed tunnel connecting bridges and the like) is increasing. Such engineering is long-term served in the marine environment with high salt fog and high humidity, and needs to bear the heavy load of heavy vehicles, engineering machinery and the like, which continuously or intermittently acts, and puts forward strict requirements on the mechanical properties and structural stability of the concrete material.

[0003] At present, the marine cement is used as a cementing material to prepare the concrete for the offshore road and bridge engineering, so as to preliminarily meet the basic durability requirement in the marine environment. However, the existing concrete formula design based on the marine cement often focuses more on the optimization of the durability performance such as chloride ion resistance and freeze-thaw resistance, and lacks the pertinence to the core requirement of heavy-load resistance, which leads to the difficulty of the concrete in fully matching the actual engineering requirement in terms of the compressive strength, the flexural strength and the fatigue resistance. Specifically, under the long-term heavy load, the concrete structure is prone to early cracking, surface spalling, internal micro-damage accumulation and the like, which not only shortens the service life of the offshore road and bridge, but also greatly increases the later maintenance cost and safety risk. SUMMARY

[0004] The present application aims to provide a road and bridge heavy-load-resistant concrete and a preparation method thereof, so as to solve the technical problem of the insufficient mechanical strength of the marine cement concrete in the background technology. The concrete prepared by the present application has excellent mechanical strength, thereby realizing the heavy-load resistance performance.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme: A preparation method of a road and bridge heavy-load-resistant concrete, characterized in that the method comprises the following steps: S1, polypropylene fibers are immersed in a potassium permanganate acid solution for treatment, and after washing and drying, surface-activated fibers are obtained. The surface-activated fibers are immersed in a γ-aminopropyl triethoxysilane solution for reaction, and after filtration and drying, interface-modified fibers are obtained; S2, the interface-modified fibers are added into water and stirred to be uniformly dispersed, so as to obtain a suspension. Nano-silica is dispersed in an aqueous epoxy resin emulsion, and then the above-mentioned suspension is added, stirred to be uniform, and then triethylenediamine is added for heating reaction. After filtration and drying, a fiber-reinforced composite material is obtained. S3, ball milling metakaolin and silica fume to obtain a composite mineral powder, mixing the composite mineral powder with water to obtain a slurry, adding water-based polyurethane emulsion and carboxylated multi-walled carbon nanotube dispersion, obtaining a mixed slurry after high-speed shearing dispersion, and obtaining interface enhanced microspheres by spray drying; S4, dry mixing silicate cement, machine-made sand, granite crushed stone, mineral powder and fiber reinforced composite material; preparing a solution of polycarboxylic acid type water reducing agent and water, adding it into a mixer, and obtaining freshly mixed cement mortar by high-speed stirring; finally, adding interface enhanced microspheres, and obtaining road and bridge heavy load resistant concrete by medium-speed stirring.

[0006] In the technical scheme of the present application, the mechanical strength of the road and bridge is improved from two aspects, thereby improving the heavy load resistance. On the one hand, a fiber reinforced system is constructed to essentially improve the toughness and crack resistance of the concrete to cope with the huge stress and impact generated by heavy load. Specifically, the polypropylene fiber is oxidized by potassium permanganate acid solution to introduce active functional groups such as hydroxyl and carboxyl groups on the inert surface of the fiber, then gamma-aminopropyl triethoxysilane is used as a molecular bridge, the silicon alcohol group at one end of the molecular bridge condenses with the active groups on the surface of the fiber, and the amino group at the other end reacts with the subsequent epoxy resin, thereby establishing a firm chemical bond between the fiber and the polymer coating layer, greatly improving the interfacial bonding force. Finally, a water-based epoxy resin / nano-silicon dioxide hybrid coating layer is constructed on the surface of the fiber, and the epoxy resin forms a tough continuous phase after curing, which gives excellent adhesion and toughness, and the nano-silicon dioxide particles act as rigid reinforcing points to further improve the hardness, wear resistance and mechanical interlocking force of the coating layer with the cement matrix. Figure 1 The SEM image of the surface of the fiber reinforced composite material prepared in the present application can be observed to present a rough microstructure on the surface of the fiber. After modification, the fiber uniformly dispersed in the concrete can not only effectively hinder the initiation of microcracks, but also can cross the cracks, disperse and transmit the concentrated stress, consume fracture energy, thereby significantly improving the ultimate flexural strength, impact toughness and fatigue life of the concrete, and avoiding the brittle failure commonly seen in heavy load road and bridge.

[0007] On the other hand, the matrix density and integrity are improved by the organic-inorganic synergistic effect, thereby optimizing the load transfer efficiency. Specifically, the metakaolin and silica fume are compounded by ball milling to obtain a mineral powder with ultra-high specific surface area and pozzolanic activity. The active mineral is blended with the waterborne polyurethane emulsion and carboxylated carbon nanotubes by high-speed shearing. The waterborne polyurethane serves as an organic binder and toughening phase, and the active groups on the molecular chain thereof can react with the mineral surface hydroxyl groups and cement hydration products. The carbon nanotubes serve as nanometer reinforcing fibers and are embedded in the mineral powder through their large specific surface area and strength. After spray drying, the functional integrated microspheres are formed. When the microspheres are incorporated into concrete, the following reactions occur in the hydration environment: the mineral components continuously undergo pozzolanic reactions, consume Ca(OH)2 to generate more C-S-H gel, greatly reduce the porosity of the interfacial transition zone, and improve the density and hardness thereof; at the same time, the waterborne polyurethane is broken into a film and solidified, and cooperates with the carbon nanotubes to form an organic-inorganic interpenetrating tough network in the interfacial transition zone. This network can efficiently bridge microcracks, disperse stress concentration, and significantly improve the bonding strength between the aggregate and the cement paste. The multiple synergistic effects from chemical densification to physical toughening enable the load to be more uniformly and effectively transferred in the entire system when the concrete bears heavy load, thereby reducing local stress concentration and macroscopically exhibiting higher compressive strength, flexural strength, and excellent durability.

[0008] Preferably, the concentration of the potassium permanganate acid solution in step S1 is 0.05-0.1 mol / L.

[0009] Preferably, the polypropylene fibers are immersed in the potassium permanganate acid solution for 10-20 min.

[0010] Preferably, the amount of the nano-silica added in step S2 is 10-15 wt% of the waterborne epoxy resin emulsion.

[0011] Preferably, the reaction temperature in step S2 is 65-70°C, and the reaction time is 2-3 h.

[0012] Preferably, the mass ratio of the metakaolin to the silica fume in step S3 is 10:3-6.

[0013] Preferably, the mass ratio of the composite mineral powder to the waterborne polyurethane emulsion in step S3 is 6:1-2.

[0014] Preferably, the fiber-reinforced composite material is pretreated by immersing the fiber-reinforced composite material in potassium silicate for immersion treatment, filtering, and heating and solidification.

[0015] In the technical scheme of the present application, it is found by the present application team that, as high-activity mineral admixtures, metakaolin and silica fume greatly accelerate the hydration reaction and continuously consume calcium hydroxide, break the chemical balance of the hydration system, and promote the continuous dissolution of cement minerals to supplement calcium ions and hydroxide ions, thereby long-term maintaining the super-high alkalinity of the pore solution. The strong alkaline environment attacks the polymer coating on the surface of the fiber, causing the molecular chain of the polymer to break, and ultimately losing the protection and toughening effect on the fiber, thereby weakening the improvement effect of the fiber reinforced composite material on the mechanical strength of the concrete. To solve this technical problem, the fiber reinforced composite material is further treated, and after the fiber is immersed in the potassium silicate solution, a dense inorganic silicate gel protective layer is formed on the surface and the superficial layer of the epoxy resin coating layer during the heating and curing process. The silicate gel is essentially homologous to the cement hydration environment, has excellent alkali resistance, can effectively block the direct contact and erosion of the high-concentration hydroxide ions and calcium ions in the cement pore solution on the internal organic epoxy resin, thereby greatly delaying the hydrolysis and degradation process. At the same time, the inorganic layer has excellent chemical compatibility and adhesion with the cement matrix, not only avoids corrosion itself, but also further enhances the interfacial bonding between the fiber and the concrete, thereby ensuring the long-term durability of the fiber in the harsh alkaline environment.

[0016] Preferably, the mass concentration of the potassium silicate is 3-5%.

[0017] A road and bridge heavy-load-resistant concrete prepared by the method.

[0018] Compared with the prior art, the present application has the following advantages: (1) The surface is modified and an epoxy resin / nano-silicon dioxide hybrid coating layer is constructed on the surface of the fiber, which greatly enhances the interfacial bonding force between the fiber and the concrete matrix, significantly improves the tensile, bending and impact toughness and fatigue life of the concrete, and effectively inhibits the generation and expansion of cracks; (2) The active mineral powder (metakaolin and silica fume) in the interfacial enhancement microspheres undergoes a pozzolanic reaction to chemically fill the pores; at the same time, the waterborne polyurethane and carbon nanotubes form an organic-inorganic interpenetrating network to physically toughen. The synergistic effect of the two greatly reduces the porosity, improves the compactness, hardness and load transfer efficiency; (3) The fiber reinforced composite material is further treated with potassium silicate, and an alkali-resistant inorganic protective layer is formed on the surface of the fiber, which effectively blocks the erosion of the high-alkali environment of the concrete on the organic resin, solves the problem of easy hydrolysis and degradation of the coating layer caused by high-activity mineral admixtures, and ensures the long-term stability of the reinforcing effect. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 SEM image of the surface of the fiber reinforced composite material prepared by the present application. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0021] Embodiment 1 A preparation method of a road-bridge heavy-load-resistant concrete comprises the following steps: Step 1: 10.0 g of polypropylene fibers (length 12 mm) are weighed and placed in a beaker, and 600 mL of a potassium permanganate acid solution (obtained by dissolving potassium permanganate in a sulfuric acid solution) with a concentration of 0.08 mol / L is prepared, and the solution is poured into the beaker to completely immerse the fibers under the condition of a constant-temperature water bath at 35 ℃. A magnetic stirrer is started, and the constant-temperature reaction is carried out at a rotating speed of 200 rpm for 15 min. After the reaction is completed, suction filtration is carried out, and the filter cake is repeatedly washed with deionized water until the effluent is neutral. The washed fibers are transferred to a blast drying oven at 70 ℃, and are dried for 120 min to obtain active polypropylene fibers.

[0022] A 300 mL γ-aminopropyltriethoxysilane ethanol solution with a concentration of 2% is prepared, and glacial acetic acid is used to adjust the pH value of the solution to 5.0, and then the solution is poured into the beaker to ensure that the fibers are completely immersed. The beaker is placed in an ultrasonic cleaner, and is treated at 50 ℃ and a power of 300 W for 35 min. After the treatment is completed, suction filtration is carried out, and the obtained fibers are transferred to a blast drying oven at 100 ℃ for solidification for 60 min to obtain interface-modified fibers.

[0023] Step 2: 10.0 g of the interface-modified fibers are placed in a three-necked flask, 400 mL of deionized water is added, and a mechanical stirrer is started to uniformly disperse the fibers at a rotating speed of 300 r / min to obtain a suspension. Another beaker is taken, 50.0 g of a water-based epoxy resin emulsion (solid content 50%) is weighed, and 6.5 g of nano-silicon dioxide is slowly added under the stirring of a high-speed shearing disperser (10000 rpm) to continuously disperse for 30 min to obtain a uniform and stable nano-SiO2 / epoxy resin premix. The premix is slowly poured into the suspension in the three-necked flask, and is uniformly mixed under the stirring at a rotating speed of 300 r / min for 30 min. Then, 1.0 g of a catalyst triethylenediamine is added, the reaction system is heated to 68 ℃, and the stirring reaction is continuously carried out at this temperature for 2.5 h. After the reaction is completed, suction filtration is carried out, and the fibers are transferred to a vacuum drying oven at 100 ℃ for drying to a constant weight to obtain fiber-reinforced composite materials.

[0024] 10.0 g of fiber-reinforced composite material was immersed in 300 mL of a 4.5% mass concentration potassium silicate aqueous solution, soaked for 10 min, and slightly stirred to ensure complete immersion. After that, the excess solution was removed by suction filtration with a Buchner funnel, and the filter cake was transferred to a 100°C air drying oven for heating and curing for 60 min, so that the potassium silicate formed a dense alkali-resistant protective layer on the outer surface of the fiber coating layer, obtaining a pretreated fiber-reinforced composite material.

[0025] Step 3: 80.0 g of metakaolin and 40 g of silica fume were weighed and placed in a planetary ball mill, and ball milled at a speed of 350 r / min for 4 h. After ball milling, a high-activity composite mineral powder was obtained. 120.0 g of the composite mineral powder was transferred to the barrel of a high-speed shearing disperser, and 200 mL of deionized water was slowly added. The initial stirring was carried out at a speed of 1000 r / min for 5 min to form a uniform slurry. Then 35 g of water-based polyurethane emulsion (solid content about 50%) and 50.0 g of carboxylated multi-walled carbon nanotube water dispersion solution with a concentration of 2 wt% were added in turn. The speed of the shearing machine was quickly increased to 5000 r / min, and high-speed shearing dispersion was continued for 30 min to obtain a mixed slurry. The mixed slurry was transferred into the feed tank of a centrifugal spray dryer for spray drying, and interface-enhanced microspheres were obtained.

[0026] Step 4: 15.0 kg of 42.5R ordinary Portland cement, 30.0 kg of machine-made 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 were weighed and put into a mixer for dry mixing at a low speed (15 r / min) for 3 min. 1.2 kg of polycarboxylate-based high-performance superplasticizer (solid content 20%) and 6.8 kg of water were mixed in a beaker to prepare a superplasticizer solution. Under the condition that the mixer continues to run at a low speed, the feeding port was opened, and the superplasticizer solution was slowly poured in within 1 min. Then the speed of the mixer was increased to high speed (35 r / min), and the mixture was stirred for 5 min to obtain freshly mixed cement mortar with good fluidity, uniformity and no clumping. Finally, 80.0 g of interface-enhanced microspheres were uniformly added to the mixer through the feeding port, and then the speed of the mixer was adjusted to medium speed (25 r / min) and continued to stir for 4 min.

[0027] Example 2 A method for preparing a road and bridge heavy load-resistant concrete, comprising the following steps: Step 1: 10.0 g of polypropylene fibers (length 12 mm) were weighed into a beaker, and a 600 mL acidic potassium permanganate solution (0.08 mol / L) was prepared (potassium permanganate was dissolved in a sulfuric acid solution) and poured into the beaker to completely immerse the fibers at 35°C in a constant temperature water bath. A magnetic stirrer was started at a speed of 200 rpm for 15 min, and after the reaction was completed, the filter cake was washed repeatedly with deionized water until the effluent was neutral. The washed fibers were transferred to a 70°C air drying oven and dried for 120 min to obtain active polypropylene fibers.

[0028] A 300 mL solution of γ-aminopropyltriethoxysilane in ethanol was prepared at a concentration of 2%, and the pH of the solution was adjusted to 5.0 using glacial acetic acid, and then poured into the beaker to ensure complete immersion of the fibers. The beaker was placed in an ultrasonic cleaner and treated at 50°C and 300W power for 35 min. After the treatment was completed, the filter cake was transferred to a 100°C air drying oven and solidified for 60 min to obtain interface-modified fibers.

[0029] Step 2: 10.0 g of interface-modified fibers were placed in a three-necked flask, 400 mL of deionized water was added, and a mechanical stirrer was started at a speed of 300 r / min to disperse uniformly to obtain a suspension. Another beaker was prepared, 50.0 g of water-based epoxy resin emulsion (solid content 50%) was weighed, and 5.5 g of nano-silicon dioxide was slowly added under the stirring of a high-speed shearing disperser (10000 rpm) for 30 min to obtain a uniform and stable nano-SiO2 / epoxy resin premix. The premix was slowly poured into the suspension in the three-necked flask, and stirring was maintained at 300 r / min for 30 min to mix uniformly. Then 1.0 g of catalyst triethylenediamine was added, and the reaction system was heated to 68°C. The stirring was continued at this temperature for 2.5 h, and after the reaction was completed, the filter cake was transferred to a 100°C vacuum drying oven to dry to constant weight to obtain a fiber-reinforced composite material.

[0030] 10.0 g of the fiber-reinforced composite material was immersed in 300 mL of a 3.5% mass concentration potassium silicate aqueous solution for 10 min with slight stirring to ensure complete impregnation. Then the excess solution was removed by a Buchner funnel, and the filter cake was transferred to a 100°C air drying oven for heating and solidification for 60 min to form a dense alkali-resistant protective layer of potassium silicate on the outer surface of the fiber coating layer to obtain a pretreated fiber-reinforced composite material.

[0031] Step 3: 80.0 g of metakaolin and 30 g of silica fume were weighed and placed in a planetary ball mill, and ball-milled at a speed of 350 r / min for 4 h. After ball-milling, a high-activity composite mineral powder was obtained. 120.0 g of the composite mineral powder was transferred to the barrel of a high-speed shearing disperser, and 200 mL of deionized water was slowly added. The mixture was initially stirred at a speed of 1000 r / min for 5 min to form a uniform slurry. Then, 25 g of water-based polyurethane emulsion (solid content of about 50%) and 50.0 g of carboxylated multi-walled carbon nanotube water dispersion solution (concentration of 2 wt%) were added in sequence. The speed of the shearing machine was quickly increased to 5000 r / min, and the mixture was continuously sheared and dispersed at high speed for 30 min to obtain a mixed slurry. The mixed slurry was transferred to a feed tank of a centrifugal spray dryer for spray drying to obtain interface-enhanced microspheres.

[0032] Step 4: 15.0 kg of 42.5R ordinary portland cement, 30.0 kg of machine-made sand (medium sand, fineness modulus of 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 were weighed and placed in a mixer. The mixture was dry-mixed at a low speed (15 r / min) for 3 min. 1.2 kg of polycarboxylate-based high-performance superplasticizer (solid content of 20%) and 6.8 kg of water were mixed in a beaker to prepare a superplasticizer solution. While the mixer was continuously running at a low speed, the superplasticizer solution was slowly poured into the mixer through the feeding port within 1 min. Then, the speed of the mixer was increased to a high speed (35 r / min), and the mixture was stirred for 5 min to obtain a freshly mixed cement mortar with good fluidity and uniformity without clumping. Finally, 80.0 g of interface-enhanced microspheres was uniformly added to the mixer through the feeding port, and then the speed of the mixer was adjusted to a medium speed (25 r / min) for continuous stirring for 4 min.

[0033] Example 3 A method for preparing a road and bridge heavy-load-resistant concrete, comprising the following steps: Step 1: 10.0 g of polypropylene fiber (length of 12 mm) was weighed and placed in a beaker, and a 600 mL potassium permanganate acid solution (concentration of 0.08 mol / L) was prepared (potassium permanganate was dissolved in a sulfuric acid solution to obtain). The solution was poured into the beaker to completely immerse the fiber under the condition of a 35°C constant-temperature water bath. A magnetic stirrer was started, and the stirring speed was set to 200 rpm. The constant-temperature reaction was carried out for 15 min. After the reaction was completed, the filter cake was washed repeatedly with deionized water until the effluent was neutral. The washed fiber was transferred to a 70°C air-drying oven and dried for 120 min to obtain active polypropylene fiber.

[0034] A 300 mL solution of γ-aminopropyltriethoxysilane in ethanol with a concentration of 2% was prepared, and the pH of the solution was adjusted to 5.0 using glacial acetic acid. The solution was then poured into a beaker to ensure that the fibers were completely immersed. The beaker was placed in an ultrasonic cleaner and treated at 50°C and a power of 300 W for 35 min. After the treatment, the fibers were transferred to a 100°C air-drying oven and solidified for 60 min to obtain the interface-modified fibers.

[0035] Step 2: 10.0 g of the interface-modified fibers were placed in a three-necked flask, 400 mL of deionized water was added, and a mechanical stirrer was started at a speed of 300 r / min to disperse the fibers uniformly to obtain a suspension. Another beaker was prepared, 50.0 g of an aqueous epoxy resin emulsion (solid content of 50%) was weighed, and 6.0 g of nano-silicon dioxide was slowly added under the stirring of a high-speed shearing disperser (10000 rpm) to obtain a uniform and stable nano-SiO2 / epoxy resin premix. The premix was slowly poured into the suspension in the three-necked flask, and the mixture was stirred at a speed of 300 r / min for 30 min to ensure uniform mixing. Then, 1.0 g of a catalyst, triethylenediamine, was added, and the reaction system was heated to 68°C. The reaction was continuously stirred at this temperature for 2.5 h. After the reaction was completed, the fibers were transferred to a 100°C vacuum drying oven and dried to a constant weight to obtain the fiber-reinforced composite material.

[0036] 10.0 g of the fiber-reinforced composite material was immersed in 300 mL of a 4% potassium silicate aqueous solution, and the immersion was performed for 10 min with slight stirring to ensure complete impregnation. Then, the excess solution was removed by suction filtration using a Buchner funnel, and the filter cake was transferred to a 100°C air-drying oven and heated and solidified for 60 min to form a dense alkali-resistant protective layer of potassium silicate on the outer surface of the fiber coating layer to obtain the pretreated fiber-reinforced composite material.

[0037] Step 3: 80.0 g of metakaolin and 35 g of silica fume were placed in a planetary ball mill and ball-milled at a speed of 350 r / min for 4 h. After the ball milling, a high-activity composite mineral powder was obtained. 120.0 g of the composite mineral powder was transferred to the feed tank of a high-speed shearing disperser, 200 mL of deionized water was slowly added, and the mixture was initially stirred at a speed of 1000 r / min for 5 min to form a uniform slurry. Then, 30 g of an aqueous polyurethane emulsion (solid content of about 50%) and 50.0 g of a carboxylated multi-walled carbon nanotube aqueous dispersion solution with a concentration of 2 wt% were sequentially added. The speed of the shearing disperser was quickly increased to 5000 r / min, and the mixture was continuously sheared and dispersed at a high speed for 30 min to obtain a mixed slurry. The mixed slurry was transferred to the feed tank of a centrifugal spray dryer for spray drying to obtain the interface-reinforced microspheres.

[0038] Step 4: Take 15.0 kg of 42.5R ordinary portland cement, 30.0 kg of machine-made 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. Put all the materials into the mixer together and dry mix at low speed (15 r / min) for 3 min. Take 1.2 kg of polycarboxylate-based high-performance water reducing agent (solid content 20%) and 6.8 kg of water in a beaker, mix well, and prepare a water reducing agent solution. With the mixer running at low speed, open the feeding port and slowly pour in the water reducing agent solution within 1 min. Then increase the speed of the mixer to high speed (35 r / min) and mix for 5 min to obtain well-fluidized and uniformly mixed fresh cement mortar without clumps. Finally, add 80.0 g of interface-enhancing microspheres to the mixer through the feeding port, then adjust the speed of the mixer to medium speed (25 r / min) and continue mixing for 4 min.

[0039] Example 4 A method for preparing a road and bridge heavy load-resistant concrete, comprising the following steps: Step 1: Take 10.0 g of polypropylene fiber (length 12 mm) and place it in a beaker. Prepare 600 mL of 0.10 mol / L potassium permanganate acid solution (dissolve potassium permanganate in sulfuric acid solution) and immerse the fiber completely in the solution in a 35°C constant temperature water bath. Start the magnetic stirrer at 200 rpm and react for 10 min. After the reaction is complete, perform suction filtration and wash the filter cake repeatedly with deionized water until the effluent is neutral. Transfer the washed fiber to a 70°C air drying oven and dry for 120 min to obtain active polypropylene fiber.

[0040] Prepare 300 mL of 2% γ-aminopropyltriethoxysilane ethanol solution and adjust the pH of the solution to 5.0 using glacial acetic acid. Then pour the solution into the beaker to ensure that the fiber is completely immersed. Place the beaker in an ultrasonic cleaner and treat it at 50°C and 300W power for 35 min. After treatment, perform suction filtration and transfer the obtained fiber to a 100°C air drying oven for solidification for 60 min to obtain interface-modified fiber.

[0041] Step 2: 10.0 g of the interface modified fiber was placed in a three-necked flask, 400 mL of deionized water was added, and a mechanical stirrer was started at a speed of 300 r / min to disperse it uniformly to obtain a suspension. Another beaker was taken, 50.0 g of the waterborne epoxy resin emulsion (solid content 50%) was weighed, and 7.5 g of nano-silicon dioxide was slowly added under the stirring of a high-speed shearing disperser (10000 rpm), and shearing dispersion was continued for 30 min to obtain a uniform and stable nano-SiO2 / epoxy resin premix. The premix was slowly poured into the suspension in the three-necked flask, and stirring was maintained at 300 r / min for 30 min to mix uniformly. Then 1.0 g of the catalyst triethylenediamine was added, the reaction system was heated to 70°C, and stirring was continued at this temperature for 3 h. After the reaction was completed, filtration was performed, the fiber was transferred to a 100°C vacuum drying oven for drying to constant weight, and a fiber-reinforced composite material was obtained.

[0042] 10.0 g of the fiber-reinforced composite material was immersed in 300 mL of a 5% mass concentration potassium silicate aqueous solution, and soaked for 10 min with slight stirring to ensure complete immersion. Then the excess solution was removed by suction filtration with a Buchner funnel, and the filter cake was transferred to a 100°C air drying oven for heating and curing for 60 min to form a dense alkali-resistant protective layer of potassium silicate on the outer surface of the fiber coating layer, and a pretreated fiber-reinforced composite material was obtained.

[0043] Step 3: 80.0 g of metakaolin and 48 g of silica fume were placed in a planetary ball mill together, and ball milled at a speed of 350 r / min for 4 h. After ball milling, a high-activity composite mineral powder was obtained, 120.0 g of the composite mineral powder was transferred to the feed tank of a high-speed shearing disperser, 200 mL of deionized water was slowly added, and initial stirring was performed at a speed of 1000 r / min for 5 min to form a uniform slurry. Then 40 g of a waterborne polyurethane emulsion (solid content about 50%) and 50.0 g of a carboxylated multi-walled carbon nanotube water dispersion solution with a concentration of 2 wt% were added in sequence. The speed of the shearing machine was quickly increased to 5000 r / min, and high-speed shearing dispersion was continued for 30 min to obtain a mixed slurry. The mixed slurry was transferred to the feed tank of a centrifugal spray dryer for spray drying to obtain interface-reinforced microspheres.

[0044] Step 4: Take 15.0 kg of 42.5R ordinary portland cement, 30.0 kg of machine-made 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. Put all the materials into the mixer together and dry mix at low speed (15 r / min) for 3 min. Take 1.2 kg of polycarboxylate-based high-performance water reducing agent (solid content 20%) and 6.8 kg of water in a beaker, mix well, and prepare a water reducing agent solution. With the mixer continuously running at low speed, open the feeding port, slowly pour in the water reducing agent solution within 1 min, then increase the mixer speed to high speed (35 r / min), and mix for 5 min to obtain well-fluidized, uniform and lump-free freshly mixed cement mortar. Finally, add 80.0 g of interface enhancement microspheres to the mixer through the feeding port, then adjust the mixer speed to medium speed (25 r / min), and continue mixing for 4 min.

[0045] Example 5 A method for preparing a road and bridge heavy load-resistant concrete, comprising the following steps: Step 1: Take 10.0 g of polypropylene fiber (length 12 mm) and place it in a beaker, prepare 600 mL of 0.05 mol / L potassium permanganate acid solution (dissolve potassium permanganate in sulfuric acid solution), and immerse the fiber completely in the solution in a 35°C constant temperature water bath. Start the magnetic stirrer and set the speed to 200 rpm for constant temperature reaction for 20 min. After the reaction is completed, perform suction filtration and wash the filter cake repeatedly with deionized water until the effluent is neutral. Transfer the washed fiber to a 70°C air drying oven and dry for 120 min to obtain active polypropylene fiber.

[0046] Prepare 300 mL of 2% γ-aminopropyltriethoxysilane ethanol solution, adjust the pH of the solution to 5.0 using glacial acetic acid, then pour it into the beaker to ensure that the fiber is completely immersed. Place the beaker in an ultrasonic cleaner and treat it at 50°C and 300W power for 35 min. After treatment, perform suction filtration and transfer the obtained fiber to a 100°C air drying oven for solidification for 60 min to obtain interface modified fiber.

[0047] Step 2: 10.0 g of the interface modified fiber was placed in a three-necked flask, 400 mL of deionized water was added, and a mechanical stirrer was started at a speed of 300 r / min to disperse it uniformly to obtain a suspension. Another beaker was taken, 50.0 g of the waterborne epoxy resin emulsion (solid content 50%) was weighed, and 5.0 g of nano-silicon dioxide was slowly added under the stirring of a high-speed shearing disperser (10000 rpm), and shearing dispersion was continued for 30 min to obtain a uniform and stable nano-SiO2 / epoxy resin premix. The premix was slowly poured into the suspension in the three-necked flask, and stirring was maintained at 300 r / min for 30 min to mix it uniformly. Then 1.0 g of the catalyst triethylenediamine was added, the reaction system was heated to 65°C, and stirring was continued at this temperature for 2 h. After the reaction was completed, filtration was performed, the fiber was transferred to a 100°C vacuum drying oven for drying to constant weight, and a fiber-reinforced composite material was obtained.

[0048] 10.0 g of the fiber-reinforced composite material was immersed in 300 mL of a 3% potassium silicate aqueous solution, and soaked for 10 min with slight stirring to ensure complete immersion. Then the excess solution was removed by suction filtration with a Buchner funnel, and the filter cake was transferred to a 100°C air drying oven for heating and curing for 60 min to form a dense alkali-resistant protective layer of potassium silicate on the outer surface of the fiber coating layer, and a pretreated fiber-reinforced composite material was obtained.

[0049] Step 3: 80.0 g of metakaolin and 24 g of silica fume were placed in a planetary ball mill together, and ball milled at a speed of 350 r / min for 4 h. After ball milling, a high-activity composite mineral powder was obtained, 120.0 g of the composite mineral powder was transferred to the feed tank of a high-speed shearing disperser, 200 mL of deionized water was slowly added, and initial stirring was performed at a speed of 1000 r / min for 5 min to form a uniform slurry. Then 20 g of a waterborne polyurethane emulsion (solid content about 50%) and 50.0 g of a carboxylated multi-walled carbon nanotube water dispersion solution with a concentration of 2 wt% were added in sequence. The speed of the shearing machine was quickly increased to 5000 r / min, and high-speed shearing dispersion was continued for 30 min to obtain a mixed slurry. The mixed slurry was transferred to the feed tank of a centrifugal spray dryer for spray drying to obtain interface-reinforced microspheres.

[0050] Step 4: Take 15.0 kg of 42.5R ordinary portland cement, 30.0 kg of machine-made 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. Put all the materials into the mixer together and dry mix at low speed (15 r / min) for 3 min. Take 1.2 kg of polycarboxylate high-performance water reducing agent (solid content 20%) and 6.8 kg of water in a beaker, mix well, and prepare a water reducing agent solution. With the mixer running at low speed, open the feeding port and slowly pour in the water reducing agent solution within 1 min, then increase the mixer speed to high speed (35 r / min) and mix for 5 min to obtain well-fluidized and uniformly mixed fresh cement mortar. Finally, add 80.0 g of interface-enhancing microspheres to the mixer through the feeding port, then adjust the mixer speed to medium speed (25 r / min) and continue mixing for 4 min.

[0051] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that steps 1 and 2 are omitted, i.e. no pretreated fiber reinforced composite is added to the concrete.

[0052] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that the pretreated fiber reinforced composite is replaced by an equal amount of polypropylene fiber.

[0053] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that the fiber reinforced composite is not treated with potassium silicate.

[0054] Comparative Example 4: The difference between Comparative Example 4 and Example 1 is that step 3 is omitted, i.e. no interface-enhancing microspheres are added to the concrete.

[0055] Performance Test 1. Compressive strength test: According to the "Standard Test Methods for Physical and Mechanical Properties of Concrete" (GB / T 50081-2019), the concrete mixtures of each example and comparative example were made into 150 mm x 150 mm x 150 mm cubes, and were cured in a standard curing box at a temperature of (20±2) °C and a relative humidity of ≥95% for 28 days. After curing, the compressive strength test was performed using an electro-hydraulic servo pressure testing machine at a loading rate of (0.5±0.1) MPa / s. Three parallel specimens were tested for each group, and the arithmetic mean value was taken as the final compressive strength value. The test results are shown in Table 1.

[0056] 2. Flexural strength test: According to GB / T 50081-2019, prism specimens with a size of 40mmx40mmx160mm were prepared, and after standard curing for 28d, the flexural test was carried out on a universal testing machine by three-point bending method, with a support span of 100mm and a loading rate control of (0.05±0.02) MPa / s. The maximum load at the time of specimen fracture was recorded, and the flexural strength was calculated according to the formula. There were 3 specimens in each group, and the average value was taken. The test results are shown in Table 1.

[0057] 3. Impact resistance test: According to the drop hammer impact method in the Standard Test Methods for Long-term Properties and Durability of Ordinary Concrete (GB / T 50082-2009), rectangular specimens with a size of 100mmx100mmx400mm were prepared, and after standard curing for 28d, the impact test was carried out using a drop hammer impact testing machine (drop hammer mass 10kg, drop distance 500mm). The impact work at which the first visible crack appeared (initial crack toughness) was recorded. There were 5 specimens in each group, and the average value was taken. The test results are shown in Table 1.

[0058] 4. Long-term mechanical strength stability test: The 150mmx150mmx150mm cubic specimens cured for 28d were immersed in tap water, and after continuous immersion for 180d, the specimens were taken out, dried and tested for compressive strength. The ratio of the 180d compressive strength to the 28d compressive strength was calculated, which was the long-term mechanical strength retention rate. There were 3 specimens in each group, and the average value was taken. The test results are shown in Table 1.

[0059] Table 1: Although the present application 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 replacements to part of the technical features, as long as they are within the spirit and principles of the present application. Any modification, equivalent replacement, improvement, etc. made shall be included in the protection scope of the present application.

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, Prepared by the method described in any one of claims 1-8.

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