Low-carbon ultra-high performance UHPC (Ultra High Performance Concrete) as well as preparation method and application thereof

Abstract

The invention relates to the technical field of ultra-high-performance concrete, in particular to low-carbon ultra-high-performance UHPC (Ultra High Performance Concrete) as well as a preparation method and application thereof. Comprising the following raw materials in parts by weight: 60-80 parts of fly ash, 40-60 parts of granulated blast furnace slag powder, 30-50 parts of an alkali activator, 100-130 parts of quartz sand, 1-3 parts of a water reducing agent, 5-15 parts of a modified reinforcing agent, 5-20 parts of nano kaolin, 1-5 parts of photocatalytic modified fibers and 10-20 parts of water. According to the invention, on the basis of replacing cement with geopolymer materials such as fly ash and slag powder and greatly reducing carbon emission, through compounding of the alkali-activated geopolymer material, the multi-scale nano-material modified reinforcing agent and the nano-kaolin, and synergistic optimization of grain composition and interface structure, the concrete realizes ultrahigh compressive strength, and has excellent compressive strength. The brittleness of the material is obviously improved, and excellent toughness is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ultra-high performance concrete, in particular to a low-carbon ultra-high performance UHPC concrete, a preparation method and application thereof. BACKGROUND

[0002] Ultra-high performance concrete (UHPC) has great application potential in infrastructure, landmark buildings and special structures due to its excellent mechanical properties, superior durability and high toughness. Traditional UHPC relies on a large amount of cement and silica fume as cementitious materials, which has huge energy consumption and high carbon emissions in the production process, which is contrary to the global green and low-carbon development trend. In order to reduce environmental load, it has become an important research direction to prepare low-carbon ultra-high performance UHPC concrete by completely replacing cement with industrial solid wastes such as fly ash and slag using geopolymer technology.

[0003] The existing geopolymer-based UHPC still has some problems: the brittleness of the geopolymer matrix is large, and the toughness is lower than that of traditional cement-based UHPC. Therefore, the present application provides a low-carbon ultra-high performance UHPC concrete, a preparation method and application thereof. SUMMARY

[0004] The purpose of the present application is to provide a preparation method of low-carbon ultra-high performance UHPC concrete. The low-carbon ultra-high performance UHPC concrete prepared by the present application not only has ultra-high compressive strength and excellent fracture toughness, realizes high performance of mechanics and durability, but also has significant photocatalytic self-cleaning and air purification ability, effectively improving the environmental functionality and green performance of the material.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0006] In a first aspect, the present application provides a low-carbon ultra-high performance UHPC concrete, comprising the following raw materials by weight: 60-80 parts of fly ash, 40-60 parts of granulated blast furnace slag powder, 30-50 parts of alkali activator, 100-130 parts of quartz sand, 1-3 parts of water reducing agent, 5-15 parts of modified reinforcing agent, 5-20 parts of nano kaolin, 1-5 parts of photocatalytic modified fiber, and 10-20 parts of water.

[0007] Further, the nano kaolin is prepared by the following method: the kaolin is crushed in a jaw crusher, and kaolin particles below 200 mesh are screened out, then triethanolamine is added and stirred for 10-20 min, and then the powder is crushed in an airflow pulverizer, and the crushing is stopped when D50 is reduced to 50-100 nm, the obtained product is calcined at 600-800℃ for 2-3h, and then naturally cooled to room temperature to obtain nano kaolin, wherein the mass of triethanolamine is 0.3%-1% of the mass of kaolin particles.

[0008] Further, the modified reinforcing agent is prepared by the following method:

[0009] S1: the vermiculite is pretreated and mixed with a hydrochloric acid solution, the pretreated vermiculite and the hydrochloric acid solution are stirred and reacted at 60-80℃ for 4-6h, and then cooled to room temperature to obtain a first mixed solution, wherein the solid-liquid ratio of the pretreated vermiculite and the hydrochloric acid solution is 1g:(8-12)mL, and the concentration of the hydrochloric acid solution is 1-3mol / L;

[0010] S2: the first mixed solution is centrifuged at a speed of 8000-12000rpm for 5-10min, the precipitate is obtained by centrifugal separation treatment, and the precipitate is washed with deionized water to obtain a hydrogen-based vermiculite filter cake;

[0011] S3: the hydrogen-based vermiculite filter cake is mixed with deionized water at a solid-liquid ratio of 1g:(50-100)mL, and is treated by an ultrasonic cell crusher at a power of 800-1200W for 1-2h to obtain a modified reinforcing agent.

[0012] Further, the pretreatment method of the vermiculite is as follows: the vermiculite is crushed, and vermiculite particles of 40-80mesh are screened out, the vermiculite particles are calcined at 850-950℃ for 5-15s, and then ground to a particle size of less than 50μm to obtain pretreated vermiculite.

[0013] The pretreatment of the vermiculite refers to a physical process of significantly expanding the volume of the natural layered structure of the vermiculite by high-temperature calcination process, which is used as an efficient internal curing agent in the present application, and can improve the hydration efficiency of the cementing material, reduce the use amount of cement with high carbon footprint, and directly reduce the implicit carbon content of UHPC while ensuring the same or better performance.

[0014] Further, the photocatalytic modified fiber is prepared by the following method: the polyvinyl alcohol fiber is surface pretreated to obtain an aminated fiber, the aminated fiber is immersed in a polystyrene sulfonic acid sodium aqueous solution for 10-30min, taken out and washed with deionized water, then immersed in a graphite phase carbon nitride quantum dot water dispersion liquid for 0.5-1h, and taken out and dried at 60-80℃ for 2-4h to obtain a photocatalytic modified fiber.

[0015] Further, the graphite phase carbon nitride quantum dot water dispersion is prepared by the following method: mixing thiourea and melamine at a mass ratio of 1:(0.5-2) to obtain a mixture, adding deionized water to the mixture to obtain a suspension, reacting the suspension at 150-200 DEG C for 1-4 h, cooling after the reaction, and performing centrifugal separation treatment to obtain supernatant, and purifying the supernatant by dialysis to obtain the graphite phase carbon nitride quantum dot water dispersion, wherein the solid-liquid ratio of the mixture to deionized water is 1 g:(2-10) mL.

[0016] Further, the polyvinyl alcohol fiber surface pretreatment method is as follows: mixing silane coupling agent KH550 and anhydrous ethanol at a mass ratio of 5:95, adding deionized water, stirring for 10-20 min, adding 1-2 drops of acetic acid, stirring for 10-20 min, sealing and standing at room temperature for 2-4 h to obtain a silane coupling agent ethanol solution, immersing polyvinyl alcohol fiber in the silane coupling agent ethanol solution, soaking for 10-30 min, and taking out, and solidifying at 60-80 DEG C for 1-2 h to obtain aminated fiber.

[0017] Further, the concentration of the sodium polystyrene sulfonate aqueous solution is 1-3 mg / mL.

[0018] Further, the alkali activator is a mixture of water glass and sodium hydroxide at a mass ratio of 1:(0.8-1.2).

[0019] In a second aspect, the application provides a preparation method of low-carbon ultra-high performance UHPC concrete, characterized in that the method comprises the following steps:

[0020] Step one: adding fly ash, granulated blast furnace slag powder, nano kaolin, quartz sand, modified reinforcing agent, water reducing agent and water into a stirrer, dry mixing for 1-2 min, and stirring at a speed of 60-80 rpm for 3-5 min to obtain a premix;

[0021] Step two: adding an alkali activator to the premix obtained in step one, stirring at a speed of 40-60 rpm for 1-2 min, adding photocatalytic modified fiber, and stirring at a speed of 5-15 rpm for 1-2 min to obtain a mixed slurry;

[0022] Step three: pouring the mixed slurry obtained in step two into a mold, vibrating and compacting, covering a preservative film, and standing and curing at 20-25 DEG C for 24-48 h to demold, and then transferring into hot water at 60-80 DEG C for curing for 3-7 days to obtain the low-carbon ultra-high performance UHPC concrete.

[0023] Compared with the prior art, the application has the following beneficial effects:

[0024] 1. In the present application, fly ash and slag powder, which are geopolymeric materials, are used to replace cement, thereby greatly reducing carbon emissions. Through the compounding of alkali-activated geopolymeric materials with multi-scale nanomaterial modification enhancers and nano-kaolin, the particle size distribution and interface structure are synergistically optimized, so that the concrete can achieve ultra-high compressive strength while significantly improving the brittleness of the material and obtaining excellent toughness.

[0025] 2. In the present application, the nano-kaolin is treated with acid and ultrasonic stripping to prepare a stable dispersion of slurry-like enhancer, effectively solving the industry problem of easy agglomeration of nanomaterials in concrete, ensuring the full play of the nanoeffect, and at the same time ensuring the uniform dispersion of fibers in the viscous geopolymer slurry, avoiding the phenomenon of clumping, so that the product performance is stable and reliable.

[0026] 3. The photocatalytic modified fiber of the present application introduces amino groups on the fiber surface through pretreatment with a silane coupling agent, and then uses the electrostatic self-assembly effect between polyelectrolyte and quantum dots to firmly and uniformly anchor graphite phase carbon nitride quantum dots on the fiber surface, which forms a three-dimensional photocatalytic network throughout the system inside the concrete. When exposed to light, the quantum dots on the surface of the fiber are excited to produce strong oxidizing substances, which can efficiently degrade nitrogen oxide pollutants in contact, and endow the concrete with sustained self-cleaning and air purification capabilities. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 A flowchart of a preparation method of low-carbon ultra-high performance UHPC concrete is proposed. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0029] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below.

[0030] Embodiment 1:

[0031] Preparation of alkali activator: water glass and sodium hydroxide are compounded at a mass ratio of 1:0.8.

[0032] Preparation of nano-kaolin: kaolin was crushed in a jaw crusher, and kaolin particles below 200 mesh were screened out. Triethanolamine was added and stirred for 10 min, and then the mixture was crushed in an airflow crusher. The crushing was stopped when D50 was reduced to 50 nm. The obtained product was calcined at 600 DEG C for 2 h, and then naturally cooled to room temperature to obtain nano-kaolin. The mass of triethanolamine was 0.3% of the mass of kaolin particles.

[0033] Pre-treatment of vermiculite: the vermiculite was crushed and treated, and vermiculite particles of 40-80 mesh were screened out. The vermiculite particles were calcined at 850 DEG C for 5 s, and then ground to a particle size of less than 50 μm to obtain pre-treated vermiculite.

[0034] Preparation of modified reinforcing agent:

[0035] S1: the pre-treated vermiculite was mixed with 1 mol / L hydrochloric acid solution, and the pre-treated vermiculite and the hydrochloric acid solution were stirred at 60 DEG C for 4 h. After the reaction was completed, the mixture was cooled to room temperature to obtain a first mixture. The solid-liquid ratio of the pre-treated vermiculite and the hydrochloric acid solution was 1 g:8 mL.

[0036] S2: the first mixture was centrifuged at a speed of 8000-12000 rpm for 5-10 min to obtain a precipitate. The precipitate was washed with deionized water to obtain a hydrogen-based vermiculite filter cake.

[0037] S3: the hydrogen-based vermiculite filter cake was mixed with deionized water at a solid-liquid ratio of 1 g:(50-100) mL, and ultrasonic treatment was performed on the mixture using an ultrasonic cell crusher at a power of 800-1200 W for 1-2 h to obtain a modified reinforcing agent.

[0038] Preparation of graphite phase carbon nitride quantum dot aqueous dispersion: thiourea and melamine were mixed at a mass ratio of 1:0.5 to obtain a mixture. Deionized water was added to the mixture to obtain a suspension. The suspension was reacted at 150 DEG C for 1 h, and then naturally cooled. After the reaction was completed, the supernatant was obtained by centrifugal separation, and the supernatant was purified by dialysis to obtain a graphite phase carbon nitride quantum dot aqueous dispersion. The solid-liquid ratio of the mixture and the deionized water was 1 g:2 mL.

[0039] Surface pre-treatment of polyvinyl alcohol fiber: silane coupling agent KH550 and anhydrous ethanol were mixed at a mass ratio of 5:95, deionized water was added, and stirred for 10 min. 1-2 drops of acetic acid were added, and stirred for 10 min. The mixture was sealed and placed at room temperature for 2 h to obtain a silane coupling agent ethanol solution. The polyvinyl alcohol fiber was immersed in the silane coupling agent ethanol solution for 10 min, and then taken out and solidified at 60 DEG C for 1 h to obtain an aminated fiber.

[0040] Preparation of photocatalytic modified fiber: the polyvinyl alcohol fiber is subjected to surface pretreatment to obtain an amino fiber, the amino fiber is immersed in a 1 mg / mL aqueous solution of polystyrene sodium sulfonate for 10 min, taken out and washed with deionized water, after the washing is completed, the fiber is immersed in a graphite phase carbon nitride quantum dot water dispersion for 0.5 h, taken out and dried at 60℃ for 2 h to obtain the photocatalytic modified fiber.

[0041] Raw material preparation: 60 parts of fly ash, 40 parts of granulated blast furnace slag powder, 30 parts of alkali activator, 100 parts of quartz sand, 1 part of water reducing agent, 5 parts of modified reinforcing agent, 5 parts of nano kaolin, 1 part of photocatalytic modified fiber, and 10 parts of water.

[0042] Preparation of low-carbon ultra-high performance UHPC concrete:

[0043] Step one: the fly ash, granulated blast furnace slag powder, nano kaolin, quartz sand, modified reinforcing agent, water reducing agent, and water are added into a stirrer, dry mixed for 1 min, stirred at a speed of 60 rpm for 3 min to obtain a premix;

[0044] Step two: the alkali activator is added into the premix obtained in step one, stirred at a speed of 40 rpm for 1 min, the photocatalytic modified fiber is added, stirred at a speed of 5 rpm for 1 min to obtain a mixed slurry;

[0045] Step three: the mixed slurry obtained in step two is injected into a mold, vibrated and compacted, covered with plastic wrap, demolded after being placed and cured at 20℃ for 24 h, and then transferred into hot water at 60℃ for curing for 3 days to obtain the low-carbon ultra-high performance UHPC concrete.

[0046] Example 2:

[0047] Preparation of alkali activator: the water glass and sodium hydroxide are compounded according to a mass ratio of 1:1 to obtain the alkali activator.

[0048] Preparation of nano kaolin: the kaolin is crushed in a jaw crusher, and kaolin particles below 200 mesh are screened out, then triethanolamine is added and stirred for 15 min, and then the mixture is pulverized in an airflow pulverizer, and the pulverization is stopped when D50 is reduced to 75 nm, the obtained product is calcined at 700℃ for 2.5 h, and then naturally cooled to room temperature to obtain the nano kaolin, and the mass of the triethanolamine is 0.7% of the mass of the kaolin particles.

[0049] Pre-treatment of vermiculite: the vermiculite is crushed, and vermiculite particles of 40-80 mesh are screened out, then the vermiculite particles are calcined at 900℃ for 10 s, and then ground to a particle size of less than 50 μm to obtain the pre-treated vermiculite.

[0050] Preparation of modified reinforcing agent:

[0051] S1: the vermiculite is mixed with 2 mol / L hydrochloric acid solution after pretreatment, the pretreated vermiculite and the hydrochloric acid solution are stirred at 70 DEG C for 5h, and then cooled to room temperature to obtain a first mixture, wherein the solid-liquid ratio of the pretreated vermiculite and the hydrochloric acid solution is 1g:10 mL;

[0052] S2: the first mixture is centrifuged at a speed of 10000 rpm for 7 min, and the precipitate is obtained by washing the precipitate with deionized water to obtain a hydrogen-based vermiculite filter cake;

[0053] S3: the hydrogen-based vermiculite filter cake is mixed with deionized water at a solid-liquid ratio of 1g:75 mL, and is treated by ultrasonic cell crusher at a power of 1000 W for 1.5h to obtain a modified reinforcing agent.

[0054] Preparation of graphite phase carbon nitride quantum dot water dispersion: thiourea and melamine are mixed at a mass ratio of 1:1 to obtain a mixture, deionized water is added to the mixture to obtain a suspension, the suspension is reacted at 175 DEG C for 2.5h, and then naturally cooled, centrifuged and treated, and the supernatant is obtained by centrifugal separation treatment, and the supernatant is purified by dialysis to obtain a graphite phase carbon nitride quantum dot water dispersion, wherein the solid-liquid ratio of the mixture and the deionized water is 1g:6 mL.

[0055] Surface pretreatment of polyvinyl alcohol fiber: silane coupling agent KH550 and anhydrous ethanol are mixed at a mass ratio of 5:95, deionized water is added, stirred for 15 min, 1-2 drops of acetic acid are added, stirred for 15 min, and sealed at room temperature for 3h to obtain a silane coupling agent ethanol solution. The polyvinyl alcohol fiber is immersed in the silane coupling agent ethanol solution for 20 min, and then taken out and solidified at 70 DEG C for 1.5h to obtain an aminated fiber.

[0056] Preparation of photocatalytic modified fiber: the polyvinyl alcohol fiber is surface pretreated to obtain an aminated fiber, the aminated fiber is immersed in a 2mg / mL polystyrene sodium sulfonate aqueous solution for 15 min, taken out and washed with deionized water, and then immersed in a graphite phase carbon nitride quantum dot water dispersion for 1h, taken out and dried at 70 DEG C for 3h to obtain a photocatalytic modified fiber.

[0057] Raw material preparation: 70 parts of fly ash, 50 parts of granulated blast furnace slag powder, 40 parts of alkali activator, 120 parts of quartz sand, 2 parts of water reducing agent, 8 parts of modified reinforcing agent, 10 parts of nano kaolin, 3 parts of photocatalytic modified fiber, and 15 parts of water.

[0058] Preparation of low-carbon ultra-high performance UHPC concrete:

[0059] Step one: add fly ash, granulated blast furnace slag powder, nano kaolin, quartz sand, modified reinforcing agent, water reducing agent and water into a blender, dry mix for 2 min, stir at a speed of 70 rpm for 4 min, and prepare a premix;

[0060] Step two: add alkali activator to the premix obtained in step one, stir at a speed of 50 rpm for 2 min, add photocatalytic modified fiber, stir at a speed of 10 rpm for 2 min, and prepare a mixed slurry;

[0061] Step three: pour the mixed slurry obtained in step two into a mold, vibrate to compact, cover with plastic wrap, and let it stand at 23°C for 36 hours before demolding. After demolding, transfer it to hot water at 70°C for 5 days of curing to obtain low-carbon ultra-high performance UHPC concrete.

[0062] Example 3:

[0063] Preparation of alkali activator: mix water glass and sodium hydroxide at a mass ratio of 1:1.2 to obtain the alkali activator.

[0064] Preparation of nano kaolin: crush kaolin in a jaw crusher, screen out kaolin particles below 200 mesh, add triethanolamine, stir for 20 min, then transfer to an air jet pulverizer for pulverization. Stop pulverization when D50 is reduced to 100 nm. Calcine the obtained product at 800°C for 3 hours, and naturally cool to room temperature to obtain nano kaolin. The mass of triethanolamine is 1% of the mass of kaolin particles.

[0065] Pre-treatment of vermiculite: crush vermiculite, screen out vermiculite particles of 40-80 mesh, calcine the vermiculite particles at 950°C for 15 seconds, then grind to a particle size of less than 50 μm to obtain pre-treated vermiculite.

[0066] Preparation of modified reinforcing agent:

[0067] S1: mix the pre-treated vermiculite with 3 mol / L hydrochloric acid solution, stir the mixture at 80°C for 6 hours, cool to room temperature after the reaction is completed, and obtain a first mixture. The solid-liquid ratio of pre-treated vermiculite to hydrochloric acid solution is 1g:12mL.

[0068] S2: centrifuge the first mixture at a speed of 12000 rpm for 10 min, wash the obtained precipitate with deionized water to obtain a hydrogen-based vermiculite filter cake.

[0069] S3: mix the hydrogen-based vermiculite filter cake with deionized water at a solid-liquid ratio of 1g:100mL, and use an ultrasonic cell pulverizer to treat for 2 hours at a power of 1200W to obtain a modified reinforcing agent.

[0070] Preparation of the graphite phase carbon nitride quantum dot water dispersion: a mixture of thiourea and melamine is prepared in a mass ratio of 1:2, deionized water is added to the mixture to prepare a suspension, the suspension is reacted at 200°C for 4h, and after the reaction is completed, it is naturally cooled, centrifugal separation treatment is carried out, and the supernatant obtained by centrifugal separation treatment is dialyzed and purified to obtain the graphite phase carbon nitride quantum dot water dispersion, wherein the solid-liquid ratio of the mixture to deionized water is 1g:10mL.

[0071] Surface pretreatment of polyvinyl alcohol fibers: a silane coupling agent KH550 is mixed with anhydrous ethanol in a mass ratio of 5:95, deionized water is added, stirred for 20 min, 1-2 drops of acetic acid are added, stirred for 20 min, and sealed at room temperature for 4h to obtain a silane coupling agent ethanol solution. The polyvinyl alcohol fibers are immersed in the silane coupling agent ethanol solution for 30 min, and after being taken out, they are cured at 80°C for 2h to obtain aminated fibers.

[0072] Preparation of photocatalytic modified fibers: the surface of the polyvinyl alcohol fibers is pretreated with the silane coupling agent ethanol solution to obtain aminated fibers, the aminated fibers are immersed in a 3mg / mL aqueous solution of polystyrene sulfonate sodium for 30 min, taken out and rinsed with deionized water, and after rinsing, they are immersed in the graphite phase carbon nitride quantum dot water dispersion for 1h, and taken out and dried at 80°C for 4h to obtain photocatalytic modified fibers.

[0073] Raw material preparation: 80 parts of fly ash, 60 parts of granulated blast furnace slag powder, 50 parts of alkali activator, 130 parts of quartz sand, 3 parts of water reducing agent, 15 parts of modified reinforcing agent, 20 parts of nano kaolin, 5 parts of photocatalytic modified fibers, and 20 parts of water.

[0074] Preparation of low-carbon ultra-high performance UHPC concrete:

[0075] Step one: add fly ash, granulated blast furnace slag powder, nano kaolin, quartz sand, modified reinforcing agent, water reducing agent, and water into a blender, dry mix for 2 min, and stir at a speed of 80 rpm for 5 min to obtain a premix;

[0076] Step two: add alkali activator to the premix obtained in step one, stir at a speed of 60 rpm for 2 min, and add photocatalytic modified fibers, stir at a speed of 15 rpm for 2 min to obtain a mixed slurry;

[0077] Step three: pour the mixed slurry obtained in step three into a mold, vibrate to compact, cover with plastic wrap, and let it stand at 25°C for 48h before demolding. After demolding, it is transferred to hot water at 80°C for 7 days of curing to obtain low-carbon ultra-high performance UHPC concrete.

[0078] Comparative Example 1:

[0079] The low-carbon ultra-high performance UHPC concrete and the preparation method thereof provided by the present comparative example are basically the same as those of example 1, and the main difference is that the addition of the modified reinforcing agent is cancelled.

[0080] Comparative Example 2:

[0081] The low-carbon ultra-high performance UHPC concrete and the preparation method thereof provided by the present comparative example are basically the same as those of example 1, and the main difference is that the same amount of vermiculite powder purchased from Shanghai Puzhen Biotechnology Co., Ltd. is used to replace the modified reinforcing agent, and the item number is 13081193182.

[0082] Comparative Example 3:

[0083] The low-carbon ultra-high performance UHPC concrete and the preparation method thereof provided by the present comparative example are basically the same as those of example 1, and the main difference is that the ordinary Portland cement is used to replace the fly ash and slag powder system in an equal amount, and the alkali activator is cancelled, the traditional cement-based UHPC preparation process is adopted, and the ordinary polyvinyl alcohol fiber is used.

[0084] Performance test: the performance of the polymeric power cable insulation prepared by example 1, example 2, example 3, comparative example 1, comparative example 2, comparative example 3 and comparative example 4 is tested, and the test data are recorded in the following table:

[0085] Sample Compressive strength (MPa) Flexural strength (MPa) Example 1 157.9 29.3 Example 2 158.7 30.1 Example 3 158.9 29.8 Comparative Example 1 135.2 22.1 Comparative Example 2 142.6 24.7 Comparative Example 3 156.9 26.5

[0086] In the performance test, the compressive strength test is based on GB / T 50081-2016, and the cubic test block is used, and the test is carried out after 28 days of maintenance, and the flexural strength test is based on GB / T 50081-2016, and the prism test block is used, and the test is carried out after 28 days of maintenance.

[0087] As can be seen from the data of comparative example 1 in the table, the compressive strength of comparative example 1 is significantly reduced due to the complete absence of the modified reinforcing agent, which confirms the key reinforcing effect of the modified reinforcing agent in the system. The mechanism is that the nanometer vermiculite after acid treatment and ultrasonic peeling presents a morphology of layer peeling and surface activation, and its huge specific surface area and surface functional groups can realize excellent nano-filling effect in the three-dimensional network structure of the geopolymer, and at the same time, these nanometer layers can form strong interfacial bonding with the polymer product, effectively blocking the crack propagation, thereby improving the compressive bearing capacity and flexural toughness of the material.

[0088] As can be seen from the data of comparative example 2 in the table, the compressive effect of comparative example 2 using unmodified vermiculite powder is far inferior to that of the present application. The unmodified vermiculite cannot be fully peeled and activated, and it is easy to agglomerate in the matrix and has weak interfacial bonding, so it cannot fully play the nano-enhancing effect.

[0089] From the data of the comparative example 3 in the table, it can be seen that the comparative example 3 adopts a traditional cement system, although the compressive strength is acceptable, but the bending toughness is lower than that of the embodiment of the application, and it does not have functionality at all. After abandoning the cement, the system of the application couples a plurality of modified materials through alkali activation technology, and the mechanical properties do not decrease, but rather exceed in toughness, which embodies the successful synergy of multiple effects such as geopolymer material, interface enhancement of acid modified nanometer vermiculite, micro-filling of nanometer kaolin and toughening of functionalized fiber.

[0090] From the comparison and analysis of the related data in the table, it can be seen that the low-carbon ultra-high performance UHPC concrete prepared by the application not only has excellent mechanical properties and durability, but also has significant photocatalytic self-cleaning and air purification capacity. Therefore, it is shown that the low-carbon ultra-high performance UHPC concrete and the preparation method thereof provided by the application have a broader market prospect and are more suitable for promotion.

[0091] In the description of the present specification, the description of the terms "one embodiment", "example", "specific example" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are contained in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0092] The preferred embodiments of the application disclosed above are only used to help explain the application. The preferred embodiments do not describe all the details, nor limit the application to the specific embodiments described. Obviously, many modifications and changes can be made according to the content of the present specification. The present specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the application, so that those skilled in the art can well understand and utilize the application. The application is limited only by the claims and their full scope and equivalents.

Claims

1. A low-carbon ultra-high performance UHPC concrete, characterized in that, The raw materials include the following parts by weight: 60-80 parts fly ash, 40-60 parts granulated blast furnace slag powder, 30-50 parts alkali activator, 100-130 parts quartz sand, 1-3 parts water-reducing agent, 5-15 parts modifier and reinforcing agent, 5-20 parts nano kaolin, 1-5 parts photocatalytic modified fiber, and 10-20 parts water; The alkaline activator is prepared by mixing water glass and sodium hydroxide at a mass ratio of 1:(0.8-1.2).

2. The low-carbon ultra-high performance UHPC concrete according to claim 1, characterized in that, The nano-kaolin is prepared by the following method: kaolin is crushed in a jaw crusher, and kaolin particles with a mesh size of less than 200 are screened out. Triethanolamine is added and stirred for 10-20 minutes. Then, it is transferred to an air jet mill for further pulverization. Pulverization is stopped when the D50 drops to 50-100 nm. The resulting product is calcined at 600-800℃ for 2-3 hours and then naturally cooled to room temperature to obtain nano-kaolin. The mass of triethanolamine is 0.3%-1% of the mass of the kaolin particles.

3. The low-carbon ultra-high performance UHPC concrete according to claim 1, characterized in that, The modified reinforcing agent is prepared by the following method: S1: Vermiculite is pretreated and then mixed with hydrochloric acid solution. The pretreated vermiculite and hydrochloric acid solution are stirred and reacted at 60-80℃ for 4-6 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain the first mixture. The solid-liquid ratio of the pretreated vermiculite to the hydrochloric acid solution is 1g:(8-12)mL, and the concentration of the hydrochloric acid solution is 1-3mol / L. S2: The first mixture is centrifuged to obtain a precipitate, and the precipitate is washed with deionized water to obtain a hydrogen-based vermiculite filter cake; S3: Mix hydrogen-based vermiculite filter cake with deionized water at a solid-liquid ratio of 1g:(50-100)mL, and sonicate for 1-2 hours using an ultrasonic cell disruptor to obtain the modified enhancer.

4. The low-carbon ultra-high performance UHPC concrete according to claim 3, characterized in that, The pretreatment method for vermiculite is as follows: the vermiculite is crushed and screened to obtain vermiculite particles of 40-80 mesh. The vermiculite particles are calcined at 850-950℃ for 5-15 seconds and then ground until the particle size is less than 50μm to obtain pretreated vermiculite.

5. The low-carbon ultra-high performance UHPC concrete according to claim 1, characterized in that, The photocatalytic modified fiber is prepared by the following method: after surface pretreatment of polyvinyl alcohol fiber, aminated fiber is obtained. The aminated fiber is immersed in sodium polystyrene sulfonate aqueous solution for 10-30 min, taken out and rinsed with deionized water. After rinsing, it is immersed in graphite phase carbon nitride quantum dot aqueous dispersion for 0.5-1 h, taken out and dried to obtain photocatalytic modified fiber.

6. The low-carbon ultra-high performance UHPC concrete according to claim 5, characterized in that, The graphite-phase carbon nitride quantum dot aqueous dispersion is prepared by the following method: thiourea and melamine are mixed at a mass ratio of 1:(0.5-2) to obtain a mixture. Deionized water is added to the mixture to obtain a suspension. The suspension is reacted at 150-200℃ for 1-4 hours. After the reaction is completed, the mixture is cooled and centrifuged to obtain a supernatant. The supernatant is then purified by dialysis to obtain the graphite-phase carbon nitride quantum dot aqueous dispersion, wherein the solid-liquid ratio of the mixture to deionized water is 1 g : (2-10) mL.

7. The low-carbon ultra-high performance UHPC concrete according to claim 5, characterized in that, The surface pretreatment method for the polyvinyl alcohol fiber is as follows: silane coupling agent KH550 and anhydrous ethanol are mixed at a mass ratio of 5:95, deionized water is added, and the mixture is stirred for 10-20 minutes. Then, 1-2 drops of acetic acid are added, and the mixture is stirred for 10-20 minutes. The mixture is then sealed and allowed to stand at room temperature for 2-4 hours to obtain a silane coupling agent ethanol solution. The polyvinyl alcohol fiber is then immersed in the silane coupling agent ethanol solution for 10-30 minutes. After removal, the fiber is cured at 60-80℃ for 1-2 hours to obtain an aminated fiber.

8. The low-carbon ultra-high performance UHPC concrete according to claim 5, characterized in that, in, The concentration of sodium polystyrene sulfonate aqueous solution is 1-3 mg / mL.

9. A method for preparing low-carbon ultra-high performance UHPC concrete according to any one of claims 1-8, characterized in that, Includes the following steps: Step 1: Add fly ash, granulated blast furnace slag powder, nano kaolin, quartz sand, modifier, water-reducing agent and water to a mixer and mix to obtain a premix. Step 2: Add alkali activator to the premix obtained in Step 1, stir, add photocatalytic modified fiber, and continue stirring to obtain mixed slurry; Step 3: Pour the mixed slurry obtained in Step 2 into the mold, vibrate to compact it, cover with plastic wrap, and let it stand for curing at 20-25℃ for 24-48 hours before demolding. After demolding, transfer it to hot water at 60-80℃ for curing for 3-7 days to obtain low-carbon ultra-high performance UHPC concrete.

10. The application of low-carbon ultra-high performance UHPC concrete prepared by the method described in claim 9 in infrastructure, landmark buildings and special structures.

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