Search

CN-121973310-A - Preparation method of graphene modified low-carbon concrete

CN121973310ACN 121973310 ACN121973310 ACN 121973310ACN-121973310-A

Abstract

The application relates to a preparation method of graphene modified low-carbon concrete, which relates to the technical field of concrete, and comprises the steps of calcining mixed solid waste particles at a low temperature to induce surface defects, and chemically grafting epoxy functional graphene on the surface of the solid waste through a silane coupling agent to prepare modified composite powder; preparing slurry of compact layer and porous layer, layering, injecting into mould, applying DC electric field to induce the directional enrichment of charged particles at interface between layers, and finally performing in-situ solidification of variable frequency microwave pulse to the formed blank body, and alternately performing high-frequency excitation and low-frequency relaxation. According to the application, the dispersibility and interfacial binding force of graphene are improved through a chemical anchoring network, interlayer binding of a gradient structure is enhanced by electric field induction, internal hot cracks are avoided through a variable frequency microwave process, and the mechanical property and durability of the high-solid-waste-content concrete are obviously improved.

Inventors

  • ZHANG KAIFENG
  • TONG XIAOGEN
  • Zhang taikang
  • Zhao Rixiu
  • HU YUBO
  • LIU JIANGFEI
  • YAO YUAN

Assignees

  • 中建西部建设第九有限公司

Dates

Publication Date
20260505
Application Date
20260304

Claims (10)

  1. 1. The preparation method of the graphene modified low-carbon concrete is characterized by comprising the following steps of: S1, mixing fly ash and slag powder to obtain mixed solid waste, calcining the mixed solid waste at 420-480 ℃, and preserving heat for 45-90 minutes to obtain activated solid waste particles with activated surface defects; S2, mixing the epoxy functionalized graphene dispersion liquid containing a dispersing agent and a silane coupling agent with the activated solid waste particles, enabling graphene sheets to be anchored on the surfaces of the activated solid waste particles through a mechanical shearing action, and drying to obtain graphene modified solid waste composite powder; S3, mixing cement, fine aggregate, water, a water reducer and the graphene modified solid waste composite powder to prepare compact layer first slurry; Adding a foaming agent on the basis of the components of the first slurry of the compact layer to prepare a second slurry of the porous layer; S4, injecting the first slurry of the compact layer into the outer layer of the die, and injecting the second slurry of the porous layer into the inner layer of the die by adopting a layered injection molding process, wherein the thickness ratio of the first slurry of the compact layer to the second slurry of the porous layer is 1 to 3; applying a direct current electric field to the top and the bottom of the mould before the slurry is initially set, and inducing directional migration of particles to obtain a gradient structure concrete blank; s5, placing the gradient structure concrete blank in a microwave reaction cavity, and executing a variable frequency microwave pulse curing process, wherein the variable frequency microwave pulse curing process comprises a high-frequency excitation stage and a low-frequency relaxation stage which are alternately performed; transmitting a microwave with a frequency of 2450MHz in the high-frequency excitation stage, and transmitting a microwave with a frequency of 915MHz in the low-frequency relaxation stage or stopping microwave transmission; and circularly executing the high-frequency excitation stage and the low-frequency relaxation stage to prepare the graphene modified low-carbon concrete.
  2. 2. The preparation method of the graphene modified low-carbon concrete according to claim 1, wherein in the step S1, the mixed solid waste consists of fly ash and slag powder in a mass ratio of 2 to 1, and the temperature rise rate of the calcination treatment is 10-15 ℃ per minute.
  3. 3. The method for preparing graphene-modified low-carbon concrete according to claim 1, wherein in the step S2, the preparation process of the epoxy functionalized graphene dispersion liquid is as follows: Dispersing graphene oxide powder in a solvent, adding gamma-glycidyl ether oxypropyl trimethoxy silane accounting for 15-25% of the mass of the graphene oxide, adjusting the pH value to 3.5-4.5, and reacting at 60-75 ℃.
  4. 4. The method for preparing graphene-modified low-carbon concrete according to claim 1, wherein in the step S2, the mixing ratio of the activated solid waste particles to the epoxy functionalized graphene dispersion liquid is: Adding 50 to 100 milliliters of the epoxy functionalized graphene dispersion liquid into every 100 grams of the activated solid waste particles; the mechanical shearing action is carried out at a rotational speed of 2000 to 3000 revolutions per minute.
  5. 5. The method for preparing graphene-modified low-carbon concrete according to claim 1, wherein in the step S3, the dense layer first slurry comprises the following components in parts by weight: 40-50 parts of cement, 50-60 parts of graphene modified solid waste composite powder, 120-150 parts of fine aggregate, 28-32 parts of water and 0.8-1.2 parts of polycarboxylate water reducer.
  6. 6. The method for preparing graphene-modified low-carbon concrete according to claim 1, wherein in the step S3, the second slurry of the porous layer comprises, by weight, 40 to 50 parts of cement, 50 to 60 parts of graphene-modified solid waste composite powder, 100 to 120 parts of fine aggregate, 30 to 35 parts of water, 0.5 to 0.8 part of polycarboxylate water reducer, 0.5 to 1.5 parts of foaming agent, and 0.1 to 0.3 part of foam stabilizer.
  7. 7. The method for preparing graphene-modified low-carbon concrete according to claim 6, wherein the foaming agent is selected from hydrogen peroxide solution or sodium dodecyl sulfate with a concentration of 27.5% to 35%; the foam stabilizer is calcium stearate; the porosity of the porous layer second slurry after curing is 20% to 30%.
  8. 8. The method for preparing graphene-modified low-carbon concrete according to claim 1, wherein in the step S4, the direct current electric field is applied at a strength of 1.0 to 2.5 volts per cm for 3 to 5 minutes, and then is powered off and left for 2 to 4 hours.
  9. 9. The method for preparing graphene-modified low-carbon concrete according to claim 1, wherein in the step S5, the microwave power density of the high-frequency excitation stage is 3.0 to 5.0 watts per gram of green body, and the duration is 60 to 120 seconds; the duration of the low frequency relaxation phase is 180 seconds to 300 seconds.
  10. 10. The method for preparing graphene-modified low-carbon concrete according to claim 1, wherein in the step S5, the variable-frequency microwave pulse curing process is performed in a total cycle of 8 to 12 cycles, and the total treatment time is 40 to 90 minutes.

Description

Preparation method of graphene modified low-carbon concrete Technical Field The application relates to the technical field of concrete, in particular to a preparation method of graphene modified low-carbon concrete. Background The utilization of industrial solid wastes such as fly ash, slag and the like to replace cement clinker is a main way for realizing low carbonization of building materials. However, the chemical activity of industrial solid wastes is low, and high-proportion substitution tends to slow down early hydration rate of concrete, and influences early strength and microstructure compactness of materials. In order to improve the mechanical properties of high-doping-amount solid waste concrete, nano reinforcement by introducing graphene is a current research hot spot. However, the graphene sheets have larger specific surface area, are extremely easy to agglomerate due to the action of Van der Waals force in the cement paste, and are difficult to uniformly disperse. Meanwhile, the surface of the graphene is chemically inert, and is combined with inorganic hydration products mainly by physical adsorption, so that the capability of the interface for transferring stress is weak, and the further improvement of the strength of the composite material is limited. In the aspects of forming and curing processes, although the traditional microwave heating technology can obviously shorten the curing period, continuous high-frequency energy input can lead to rapid vaporization of moisture in the concrete in a short time. When the internal vapor pressure exceeds the tensile strength of the matrix, microscopic thermal cracks are induced, destroying the integrity of the material. In addition, for functionally graded concrete with layered design, due to the difference in shrinkage of different layer materials, conventional curing methods tend to produce stress concentrations at the interface between layers, resulting in reduced interlayer bond strength and even delamination. Disclosure of Invention The application aims to provide a preparation method of graphene modified low-carbon concrete, which solves the technical problems that the existing high-solid waste mixed concrete has insufficient mechanical properties due to graphene agglomeration and weak interface bonding, and the traditional microwave curing process is easy to cause internal thermal cracking and poor interlayer bonding of a gradient structure. The preparation method of the graphene modified low-carbon concrete comprises the following steps: s1, mixing the fly ash and the slag powder according to a specified proportion to obtain mixed solid waste. The mixed solid waste is placed in a heating apparatus, calcined at a temperature of 420 to 480 degrees celsius, and maintained at that temperature for 45 to 90 minutes. In the process, the residual carbon and volatile impurities on the surfaces of the solid waste particles are removed by high-temperature heat treatment. Meanwhile, the thermal stress effect causes lattice distortion on the surfaces of the solid waste particles to form surface defect sites with higher reactivity, and the activated solid waste particles are obtained. S2, mixing the epoxy functionalized graphene dispersion liquid containing the dispersing agent and the silane coupling agent with the activated solid waste particles. Under the action of mechanical shearing force, the graphene sheets are contacted with the activated solid waste particles. Based on the chemical bonding action between the active functional groups on the surface of the epoxy functionalized graphene and the defect sites on the surface of the activated solid waste particles and the physical coating action of graphene sheets on the particles, the graphene sheets are anchored on the surface of the activated solid waste particles. And drying to obtain the graphene modified solid waste composite powder. The structure establishes a heat conduction and electric conduction connection path among the solid waste particles. S3, preparing a first slurry of the compact layer and a second slurry of the porous layer respectively based on rheology and pore structure design. Mixing cement, fine aggregate, water, a water reducing agent and graphene modified solid waste composite powder to prepare compact layer first slurry. And adding a foaming agent on the basis of the components of the first slurry of the compact layer, and preparing the second slurry of the porous layer by utilizing the gas generating effect of the foaming agent. S4, injecting first slurry of a compact layer into the outer layer space of the die and injecting second slurry of a porous layer into the inner layer space of the die by adopting a layered injection molding process. The thickness ratio of the dense layer first slurry to the porous layer second slurry was controlled to be 1 to 3. And at the stage that the slurry finishes pouring but is not initially set, a direct current electric field is applied to th