CN114455882B - Preparation method and application of multifunctional nano composite material for concrete - Google Patents
Preparation method and application of multifunctional nano composite material for concrete Download PDFInfo
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- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
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- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
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Abstract
The invention discloses a preparation method and application of a multifunctional nano composite material for concrete, which comprises the following steps: firstly, biomass waste is utilized and subjected to oriented catalytic depolymerization-polymerization under the hydrothermal condition and the action of a metal-solid acid bifunctional catalyst to prepare carbon quantum dots; modifying the surface of the carbon quantum dot in advance by using a ligand; and finally, forming thin-layer silicon dioxide on the surfaces of the carbon quantum dots through directional hydrolysis of silane, and then calcining to obtain the multifunctional nano composite material for the concrete, wherein the carbon quantum dots are wrapped by the porous thin-layer silicon dioxide. The retarding effect of the nano composite material for concrete is superior to that of the traditional retarder sodium gluconate. Meanwhile, the nano composite material can enable the joint of the aggregate and the cementing material to be attached more tightly, the strength of the concrete 7 d and 28 d is improved by 17% compared with that of a reference sample, and the nano composite material also has fluorescent property and can be used as an auxiliary material of a fluorescent pavement in ecological pervious concrete or other similar purposes.
Description
Technical Field
The invention relates to the technical field of concrete admixtures, in particular to a preparation method and application of a multifunctional nano composite material for concrete.
Background
The strategies of 'carbon peak reaching' and 'carbon neutralization' provide new requirements for the development of the green building industry. The green energy-saving carbon-reducing building material is used as a foundation of engineering construction, the green energy-saving carbon-reducing level is selected as a building material, the influence is huge due to the existence of scale effect, and the green building material with obvious carbon-reducing or carbon-fixing effect is the key for researching, producing and popularizing. The preparation and application of novel nanomaterials are the most active research direction in the field of new material research nowadays. At present, the nano material mainly comprises organic, inorganic, metal, nonmetal and other types, in recent years, the literature and patents for preparing the nano material by utilizing agricultural wastes are increased correspondingly, and the nano material is taken as a microscopic material in a transition area between a macroscopic substance and an atomic cluster, and has a surface effect, a quantum granulation effect, a small-size effect and a macroscopic tunnel effect which are not possessed by the macroscopic substance material. With the development of nanotechnology, researchers at home and abroad are trying to add nanoscale materials into concrete materials to enable the concrete materials to have special mechanical behaviors and properties. At present, the application of nano silicon dioxide, graphene oxide and carbon nanotubes in concrete is reported in many documents and patents, and the strength of concrete can be improved to a great extent by the materials under the condition of low doping amount of the materials. However, the problems that the nano material is expensive and cannot be applied in large scale in practical engineering, and the water solubility is poor and cannot be uniformly dispersed in concrete, so that a stress concentration region appears at an aggregate in a hardened cement-based material and a region with weak exposure performance is easily caused exist are solved. Therefore, the synthesis of the cheap nano material with good hydrophilicity by utilizing the biomass raw material has great significance for the development of modern concrete.
The nano silicon dioxide has a filling effect and a volcanic ash effect, and can promote the strength of mortar or concrete to increase. But the application of the nano silicon dioxide in many fields is limited due to poor dispersibility, and in order to improve the dispersibility, patent CN108947290A reports that a polycarboxylic acid water reducing agent is used for modifying the nano silicon dioxide to improve the dispersion degree of the nano silicon dioxide in a cement system; patent CN110845872A reports that ethanol is used as a solvent, and silane coupling agent is used for modification, so that the dispersibility and stability of the modified ethanol are improved; although the above two patents improve the dispersibility of silica to a certain extent, the size of the silica is increased accordingly, and there is a limit to increase the compactness. Patent CN104628422A reports a method of coating nano particles with silica to make cement or concrete have wave-absorbing property and dense chamber surface, which shows that nano material with smaller coating size can also give other functions besides the original specific function of nano material. The carbon quantum dots are zero-dimensional nano materials, have strong hydrophilicity, are cheap and easy to obtain, and have simple synthesis method. Carbon quantum dots as a novel nano material have been widely applied in the fields of biomarkers, photocatalysis, biosensors and the like. And relatively little application in concrete materials. Patent CN111943595A reports a preparation method of high-strength white concrete, in which carbon quantum dots are added to improve the strength of the concrete. However, the carbon quantum dots are small in size and easy to agglomerate, so that the improvement of the concrete strength by using the carbon quantum dots alone is limited.
Disclosure of Invention
1. The technical problem to be solved is as follows:
in order to solve the technical problems, the invention provides a preparation method and application of a multifunctional nano composite material for concrete. In addition, the multifunctional nano composite material for concrete also has fluorescence property, and can be used as an auxiliary material of a fluorescent pavement in ecological pervious concrete or other similar purposes.
2. The technical scheme is as follows:
a preparation method of a nano composite material for multifunctional concrete is characterized by comprising the following steps: the method comprises the following steps:
the method comprises the following steps: preparing carbon quantum dots; mixing biomass waste and a metal-solid acid bifunctional catalyst in a preset proportion with water, transferring the mixture to a hydrothermal reaction kettle, reacting at a preset temperature for a preset time, depolymerizing internal chemical bonds of the biomass waste under the action of metal active sites in the catalyst to generate water-soluble organic small molecules, and directionally polymerizing the water-soluble organic small molecules under the action of acid sites in the catalyst to generate water-soluble carbon quantum dots; filtering the solution after the reaction to obtain a filtrate, freeze-drying the filtrate, and grinding to obtain solid powder, namely solid carbon quantum dot powder; wherein the mass ratio of the biomass waste to the metal acid bifunctional catalyst to the water is 1: 0.02 to 0.1:1.5 to 5.
Step two: pre-modifying the surface of the carbon quantum dot; dissolving the freeze-dried solid carbon quantum dot powder in a certain amount of water, adding a ligand solution, and stirring for a period of time, wherein in the process, the ligand is adsorbed on the surface of the carbon quantum dot to obtain a carbon quantum dot solution protected by the ligand; wherein the mass ratio of the solid carbon quantum dot powder to the ligand is 1: 0.05 to 0.2.
Step three: preparing a nano composite material; adding 25% ammonia water solution into the carbon quantum dot solution protected by the ligand prepared in the second step, stirring, then slowly dropwise adding tetraethyl orthosilicate solution, stirring, and hydrolyzing at room temperature for a preset time and stopping; freeze-drying the prepared liquid, and grinding to obtain solid powder; transferring the solid powder into a muffle furnace, and calcining to obtain porous thin-layer silicon dioxide coated carbon quantum dots, namely the multifunctional nano composite material for concrete; wherein the mass ratio of the carbon quantum dots protected by the ligand to the ammonia water to the tetraethyl orthosilicate is 1:0.03 to 0.3:0.02 to 0.1.
Further, the biomass waste is one or more of straw, rice hull, rice straw, wheat straw, corncob, bagasse, wood powder, branches and leaves, waste wood and peanut shell or a combination of two or more of the straw, the rice hull, the rice straw, the wheat straw, the corncob, the bagasse, the wood powder and the branches and leaves.
Further, the metal-solid acid bifunctional catalyst is a supported catalyst, and the carrier is one of alumina, a molecular sieve, hydrotalcite and montmorillonite; the metal is one of transition metals and noble metals such as iron, cobalt, nickel, palladium, ruthenium and the like.
Further, the reaction temperature of the hydrothermal reaction kettle in the first step is 150-400 ℃, and the reaction time is 1-3 h.
Further, the water-soluble organic small molecules in the step one comprise water-soluble organic molecules containing acid, alcohol, ammonia, ketone and phenol.
Further, the time for freeze drying the filtrate in the step one is 24 to 96 hours.
Further, the ligand in the second step is one of 3-mercaptopropyltriethoxysilane, (3-mercaptopropyl) trimethoxysilane, 3-mercaptopropylethyl sulfide and 3-mercaptopropylmethyldimethoxysilane.
Further, the freeze-dried solid carbon quantum dot powder in the second step is dissolved in a certain amount of water, wherein the mass ratio of the solid carbon quantum dot powder to the water is 1:3 to 5; and the stirring time in the second step is 0.5 to 5 hours.
Further, the hydrolysis time in the third step is 0.5 to 24 hours, the calcining temperature is 200 to 500 ℃, and the calcining time is 0.5 to 5 hours.
The application of the multifunctional nano composite material for concrete is characterized in that: the nano material can be used as a concrete retarder, a later strength reinforcing agent and an auxiliary material of a fluorescent pavement in ecological pervious concrete.
3. Has the beneficial effects that:
(1) Compared with graphene oxide and carbon nanotubes which are used as concrete modifiers, the multifunctional concrete nanocomposite prepared by the method disclosed by the invention can enhance the later strength of concrete to a certain extent, but has the advantages of low cost, simple production process, environmental friendliness and the like, and has a wide application prospect.
(2) Compared with graphene oxide and carbon nanotubes as concrete modifiers, the multifunctional concrete nanocomposite prepared by the invention has the advantages of good water solubility and uniform distribution, does not cause the problem of overhigh local strength, and is easier to construct.
(3) The multifunctional nano composite material for concrete prepared by the invention contains more functional groups such as carboxyl, sulfonic group, carbonyl, hydroxyl, amino and the like, so that the hydration rate of cement is delayed, the composite material has a good retarding effect, and the later strength can be improved.
(4) The nano composite material for the multifunctional concrete prepared by the invention has relatively stable fluorescence performance, and can be used as an auxiliary material of a fluorescent pavement in ecological pervious concrete or other similar purposes.
Drawings
FIG. 1 is a schematic view illustrating a process for preparing a nanocomposite for multifunctional concrete according to the present invention;
fig. 2 is a fluorescent picture of the nanocomposite for multifunctional concrete prepared in embodiment 2.
Detailed Description
A preparation method of a nano composite material for multifunctional concrete is characterized by comprising the following steps: the method comprises the following steps:
the method comprises the following steps: preparing carbon quantum dots; mixing biomass waste and a metal-solid acid bifunctional catalyst in a preset proportion by using water, transferring the mixture to a hydrothermal reaction kettle, reacting at a preset temperature for a preset time, depolymerizing internal chemical bonds of the biomass waste under the action of metal active sites in the catalyst to generate water-soluble organic small molecules, and directionally polymerizing the water-soluble organic small molecules under the action of acid sites in the catalyst to generate water-soluble carbon quantum dots; filtering the solution after the reaction to obtain a filtrate, freeze-drying the filtrate, and grinding to obtain solid powder, namely solid carbon quantum dot powder; wherein the mass ratio of the biomass waste to the metal acid bifunctional catalyst to the water is 1: 0.02 to 0.1:1.5 to 5.
Step two: pre-modifying the surface of the carbon quantum dot; dissolving the freeze-dried solid carbon quantum dot powder in a certain amount of water, adding a ligand solution, and stirring for a period of time, wherein in the process, the ligand is adsorbed on the surface of the carbon quantum dot to obtain a carbon quantum dot solution protected by the ligand; wherein the mass ratio of the solid carbon quantum dot powder to the ligand is 1: 0.05 to 0.2.
Step three: preparing a nano composite material; adding 25% ammonia water solution into the carbon quantum dot solution protected by the ligand prepared in the second step, stirring, then slowly dropwise adding tetraethyl orthosilicate solution, stirring, and hydrolyzing at room temperature for a preset time and stopping; freeze-drying the prepared liquid, and grinding to obtain solid powder; transferring the solid powder into a muffle furnace, and calcining to obtain porous thin-layer silicon dioxide coated carbon quantum dots, namely the multifunctional nano composite material for concrete; wherein the mass ratio of the carbon quantum dots protected by the ligand to the ammonia water to the tetraethyl orthosilicate is 1:0.03 to 0.3:0.02 to 0.1.
Further, the biomass waste is one or a combination of two or more of straw, rice hull, rice straw, wheat straw, corn cob, bagasse, wood powder, branches and leaves, waste wood and peanut shell.
Further, the metal-solid acid bifunctional catalyst is a supported catalyst, and the carrier is one of alumina, a molecular sieve, hydrotalcite and montmorillonite; the metal is one of transition metals and noble metals such as iron, cobalt, nickel, palladium, ruthenium and the like.
Further, the reaction temperature of the hydrothermal reaction kettle in the step one is 150-400 ℃, and the reaction time is 1-3 h.
Further, the water-soluble organic small molecules in the step one comprise water-soluble organic molecules containing acid, alcohol, ammonia, ketone and phenol.
Further, the time for freeze drying the filtrate in the step one is 24 to 96 hours.
Furthermore, the ligand in the second step is one of 3-mercaptopropyltriethoxysilane, (3-mercaptopropyl) trimethoxysilane, 3-mercaptopropylethylsulfide and 3-mercaptopropylmethyldimethoxysilane which contain mercaptosilane.
Further, the freeze-dried solid carbon quantum dot powder in the second step is dissolved in a certain amount of water, wherein the mass ratio of the solid carbon quantum dot powder to the water is 1:3 to 5; and the stirring time in the second step is 0.5 to 5 hours.
Further, the hydrolysis time in the third step is 0.5 to 24 hours, the calcining temperature is 200 to 500 ℃, and the calcining time is 0.5 to 5 hours.
The application of the multifunctional nano composite material for concrete is characterized in that: the nano material can be used as a concrete retarder, a later strength reinforcing agent and an auxiliary material of a fluorescent pavement in ecological pervious concrete.
Example 1
1) Weighing 5.0 g of straw, 5.0 g of rice hull and 0.2 g of iron-loaded alumina, adding into 50.0 g of water, uniformly mixing, transferring into a hydrothermal reaction kettle, reacting at 200 ℃ for 2 hours, carrying out suction filtration to obtain brown filtrate, carrying out freeze drying on the filtrate for 96 hours, and grinding to obtain brown solid powder.
2) 5.0 g of the freeze-dried solid carbon quantum dot powder was dissolved in 15.0 g of water, 0.5 g of (3-mercaptopropyl) trimethoxysilane was added, and the mixture was stirred at normal temperature for 0.5 hour and then stopped.
3) And taking 20.0g of the carbon quantum dot solution protected by the ligand, adding 0.6 g of 25% ammonia water solution into the carbon quantum dot solution, stirring the mixture evenly, slowly dropwise adding 1.0 g of tetraethyl orthosilicate solution, and hydrolyzing the mixture at room temperature for 12 hours. And freeze-drying and grinding the solution to obtain brown solid powder, transferring the brown solid powder into a muffle furnace, and calcining the powder for 3 hours at 150 ℃ in an ambient atmosphere to obtain the multifunctional nano composite material for the concrete, wherein the porous thin-layer silicon dioxide wraps the carbon quantum dots.
Example 2
1) Weighing 7.0 g of corncob, 5.0 g of bagasse and 0.5 g of nickel-loaded molecular sieve, adding into 18.0 g of water, uniformly mixing, transferring into a hydrothermal reaction kettle, reacting at 400 ℃ for 1 h, performing suction filtration to obtain brown filtrate, freeze-drying the filtrate for 40 h, and grinding to obtain brown solid powder.
2) 5.0 g of the freeze-dried solid carbon quantum dot powder was dissolved in 20.0g of water, 0.5 g of 3-mercaptopropylethyl sulfide was added thereto, and the mixture was stirred at normal temperature for 2 hours and then stopped.
3) And (3) taking 20.0g of the carbon quantum dot solution protected by the ligand, adding 4 g of 25% ammonia water solution, stirring uniformly, slowly dropwise adding 2.0 g of tetraethyl orthosilicate solution, and hydrolyzing at room temperature for 18 h. And (3) freeze-drying and grinding the solution to obtain brown solid powder, transferring the brown solid powder into a muffle furnace, and calcining the powder for 2 hours at 400 ℃ in an ambient atmosphere to obtain the multifunctional nano composite material for the concrete, wherein the porous thin-layer silicon dioxide wraps the carbon quantum dots.
Example 3
1) Weighing 7.0 g of rice straw, 5.0 g of wheat straw and 0.8 g of hydrotalcite loaded with palladium, adding the mixture into 30.g of water, uniformly mixing, transferring the mixture into a hydrothermal reaction kettle, reacting at 250 ℃ for 2.5 hours, carrying out suction filtration to obtain brown filtrate, carrying out freeze drying on the filtrate for 24 hours, and grinding to obtain brown solid powder.
2) 5.0 g of the freeze-dried solid carbon quantum dot powder is dissolved in 30.g of water, 0.8 g of 3-mercaptopropyltriethoxysilane is added, and stirring is carried out for 5 hours at normal temperature, and then stopping.
3) And (3) taking 20.0g of the carbon quantum dot solution protected by the ligand, adding 6 g of 25% ammonia water solution, uniformly stirring, slowly dropwise adding 0.4 g of tetraethyl orthosilicate solution, and hydrolyzing at room temperature for 18 h. And freeze-drying and grinding the solution to obtain brown solid powder, transferring the brown solid powder into a muffle furnace, and calcining the powder for 2.5 hours at 300 ℃ in an ambient atmosphere to obtain the multifunctional nano composite material for the concrete, wherein the porous thin-layer silicon dioxide wraps the carbon quantum dots.
Example 4
1) Weighing 6.0 g of wood powder, 4.0 g of branches and leaves and 1 g of cobalt-loaded molecular sieve, adding 50.0 g of water, uniformly mixing, transferring into a hydrothermal reaction kettle, reacting at 280 ℃ for 3 h, carrying out suction filtration to obtain brown filtrate, carrying out freeze drying on the filtrate for 32 h, and grinding to obtain brown solid powder.
2) 5.0 g of the above-mentioned freeze-dried solid carbon quantum dot powder was dissolved in 25.0 g of water, and 0.2 g of 3-mercaptopropylmethyldimethoxysilane was added thereto, and the mixture was stirred at normal temperature for 1 hour, and then stopped.
3) And (3) taking 20.0g of the ligand-protected carbon quantum dot solution, adding 3.6 g of 25% ammonia water solution, stirring uniformly, slowly dropwise adding 1.2 g of tetraethyl orthosilicate solution, and hydrolyzing at room temperature for 20 hours, and stopping. And (3) freeze-drying and grinding the solution to obtain brown solid powder, transferring the brown solid powder into a muffle furnace, and calcining the powder for 2 hours at 350 ℃ in an ambient atmosphere to obtain the multifunctional nano composite material for the concrete, wherein the porous thin-layer silicon dioxide wraps the carbon quantum dots.
Example 5
1) Firstly weighing 5.0 g of waste wood, 6.0 g of peanut shell and 0.8 g of montmorillonite loaded with ruthenium, adding the waste wood, the peanut shell and the montmorillonite into 25.0 g of water, uniformly mixing, transferring the mixture into a hydrothermal reaction kettle, reacting at 300 ℃ for 2.5 hours, carrying out suction filtration to obtain brown filtrate, carrying out freeze drying on the filtrate for 24 hours, and grinding to obtain brown solid powder.
2) 5.0 g of the above-mentioned freeze-dried solid carbon quantum dot powder was dissolved in 30.0 g of water, 1 g of 3-mercaptopropylmethyldimethoxysilane was added thereto, and the mixture was stirred at room temperature for 2 hours, and then the reaction was stopped.
3) And (3) taking 20.0g of the ligand-protected carbon quantum dot solution, adding 2.5 g of 25% ammonia water solution, stirring uniformly, slowly dropwise adding 2.0 g of tetraethyl orthosilicate solution, and hydrolyzing at room temperature for 12 hours and stopping. And (3) freeze-drying and grinding the solution to obtain brown solid powder, transferring the brown solid powder into a muffle furnace, and calcining the powder for 2.5 hours at 300 ℃ in an ambient atmosphere to obtain the multifunctional concrete nano composite material with the porous thin-layer silicon dioxide coated with the carbon quantum dots.
Performance test
1. Cement setting time test
The cement setting time testing method is carried out according to a method specified in GB 1346-2011 'cement standard consistency water consumption, setting time and stability testing method', a retarder is commonly used for inhibiting the concrete loss caused by the over-rapid hydration of cement to be faster when the temperature in summer is higher, so the initial setting time and the final setting time of the retarder are measured at the high temperature (50 +/-1) DEG C, and the traditional retarder sodium gluconate is used as a comparison sample.
Note: the mixing amount refers to the mass fraction of the admixture in the cementing material.
It can be seen from the data that the retarding effect of the nano-materials prepared in examples 1 to 5 is better than that of sodium gluconate.
2. Concrete setting time and compressive strength test
The concrete setting time test method is carried out according to the method specified in GB/T50080-2002 standard of common concrete mixture performance test methods, curing is carried out in a moisture curing box with the temperature of 20 +/-1 ℃ and the relative humidity of not less than 90%, and the initial setting time and the final setting time are measured. The concrete strength test is carried out according to the method specified in GB 8076 to 2008 concrete admixture and GB/T50081 to 2002 ordinary concrete mechanical property test method.
Note: the mixing amount refers to the mass fraction of the admixture in the cementing material.
According to the data, the setting time of the concrete added with different nano materials is superior to that of sodium gluconate, wherein the initial setting time of the nano material prepared in the example 2 is prolonged by 50 min compared with a blank sample, the final setting time is prolonged by 86 min, and the retarding effect is excellent. It can be found that the strength of the sample added with the nano material test block at 1 d is slightly lower than that of the sample added with sodium gluconate, mainly because the sample has a certain retardation effect, the strength of the sample at 3 d/7 d/28 d is higher than that of the sample added with sodium gluconate, and the strength of the nano material prepared in example 2 is relatively highest.
Note: the mixing amount refers to the mass fraction of the admixture in the cementing material.
From the above data, it can be seen that the compressive strength of the nanomaterial prepared in example 2 at three different ages of 3 d/7 d/28 d is improved to different extents, and the strength of the nanomaterial increases with the increase of the doping amount (0.02 to 0.08%), but if the doping amount is too high (0.1%), the strength of the nanomaterial decreases relatively at the later stage, so that the optimum doping amount of the nanomaterial is 0.08% of the cementitious material. The 3 d strength can be improved by 9.8% at most, and the 7 d and 28 d strengths can be improved by more than 17%.
3. Test for fluorescence Properties
The fluorescence properties of the novel fluorescent nanocomposite prepared in example 2 were irradiated by an ultraviolet lamp with an excitation wavelength of 365 nm, as shown in fig. 2. As can be seen from fig. 2, when the ultraviolet lamp is used for irradiation, the silica-coated carbon quantum dots have obvious fluorescent properties, and can be used as an auxiliary material of a fluorescent pavement in ecological water-permeable concrete or other similar applications.
Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (7)
1. A preparation method of a nano composite material for multifunctional concrete is characterized by comprising the following steps: the method comprises the following steps:
the method comprises the following steps: preparing carbon quantum dots; mixing biomass waste and a metal-solid acid bifunctional catalyst in a preset proportion with water, transferring the mixture to a hydrothermal reaction kettle, reacting at a preset temperature for a preset time, depolymerizing internal chemical bonds of the biomass waste under the action of metal active sites in the catalyst to generate water-soluble organic small molecules, and directionally polymerizing the water-soluble organic small molecules under the action of acid sites in the catalyst to generate water-soluble carbon quantum dots; filtering the solution after the reaction to obtain a filtrate, freeze-drying the filtrate, and grinding to obtain solid powder, namely solid carbon quantum dot powder; wherein the mass ratio of the biomass waste to the metal acid bifunctional catalyst to the water is 1: 0.02 to 0.1:1.5 to 5;
step two: pre-modifying the surface of the carbon quantum dot; dissolving the freeze-dried solid carbon quantum dot powder in a certain amount of water, adding a ligand solution, and stirring for a period of time, wherein in the process, the ligand is adsorbed on the surface of the carbon quantum dot to obtain a carbon quantum dot solution protected by the ligand; wherein the mass ratio of the solid carbon quantum dot powder to the ligand is 1: 0.05 to 0.2;
step three: preparing a nano composite material; adding 25% ammonia water solution into the carbon quantum dot solution protected by the ligand prepared in the second step, stirring, then slowly dropwise adding tetraethyl orthosilicate solution, stirring, and hydrolyzing at room temperature for a preset time and stopping; freeze-drying the prepared liquid, and grinding to obtain solid powder; transferring the solid powder into a muffle furnace, and calcining to obtain porous thin-layer silicon dioxide coated carbon quantum dots, namely the multifunctional nano composite material for concrete; wherein the mass ratio of the carbon quantum dots protected by the ligand to the ammonia water to the tetraethyl orthosilicate is 1:0.03 to 0.3:0.02 to 0.1;
the ligand in the second step is one of 3-mercaptopropyltriethoxysilane, (3-mercaptopropyl) trimethoxysilane, 3-mercaptopropylethylsulfide and 3-mercaptopropylmethyldimethoxysilane which contain mercaptosilane;
dissolving the freeze-dried solid carbon quantum dot powder in a certain amount of water, wherein the mass ratio of the solid carbon quantum dot powder to the water is 1:3 to 5; and the stirring time in the second step is 0.5 to 5 hours.
2. The method for preparing a multifunctional nanocomposite for concrete according to claim 1, wherein the method comprises the following steps: the biomass waste is one or more of straw, rice hull, rice straw, wheat straw, corncob, bagasse, wood powder, branches and leaves, waste wood and peanut shell.
3. The method for preparing a multifunctional nanocomposite for concrete according to claim 1, wherein the method comprises the following steps: the metal-solid acid bifunctional catalyst is a supported catalyst, and the carrier is one of alumina, molecular sieve, hydrotalcite and montmorillonite; the metal is one of iron, cobalt, nickel, palladium and ruthenium.
4. The method for preparing a multifunctional nanocomposite for concrete according to claim 1, wherein the method comprises the following steps: the reaction temperature of the hydrothermal reaction kettle in the first step is 150-400 ℃, and the reaction time is 1-3 h.
5. The method for preparing a multifunctional nanocomposite for concrete according to claim 1, wherein: the water-soluble organic micromolecules in the step one comprise water-soluble organic molecules containing acid, alcohol, ammonia, ketone and phenol.
6. The method for preparing a multifunctional nanocomposite for concrete according to claim 1, wherein the method comprises the following steps: the time for freeze drying the filtrate in the step one is 24 to 96 hours.
7. The method for preparing a multifunctional nanocomposite for concrete according to claim 1, wherein: the hydrolysis time in the third step is 0.5 to 24 hours, the calcining temperature is 200 to 500 ℃, and the calcining time is 0.5 to 5 hours.
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