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CN-121990778-A - Bayer process red mud-based baking-free ceramsite and preparation method and application thereof

CN121990778ACN 121990778 ACN121990778 ACN 121990778ACN-121990778-A

Abstract

The application belongs to the technical field of solid waste ceramsite, and particularly relates to a Bayer process red mud-based baking-free ceramsite, and a preparation method and application thereof. The baking-free ceramsite comprises a core part and a shell part, wherein the core part comprises Bayer process red mud, fly ash, steel slag micro powder and gypsum, the shell part comprises Bayer process red mud, slag cement, silica fume and a composite activator, the composite activator comprises sodium hydroxide and water glass, the barrel pressure intensity of the baking-free ceramsite is more than or equal to 3.5MPa, and the stacking density of the baking-free ceramsite is less than or equal to 1000kg/m 3 . The obtained gradient ceramsite is subjected to main load by a high-strength shell layer in a barrel pressure test, and the porous structure of the core layer inhibits the increase of the overall density, so that the barrel pressure intensity is more than or equal to 3.5MPa, the stacking density is less than or equal to 1000kg/m 3 , sintering and extra lightweight aggregate are avoided, a traditional path of 'strength-density synchronous increase' is jumped out, and an creative thought for constructing a functional gradient by the activity difference of industrial solid wastes is formed.

Inventors

  • GAO JIANYANG
  • QIN NIANYONG
  • LI FENGKE
  • YUAN CHONGLIANG
  • FAN GUANG
  • HU MUQIU
  • HUANG ENJIE

Assignees

  • 中铝山东有限公司

Dates

Publication Date
20260508
Application Date
20251216

Claims (10)

  1. 1. The Bayer process red mud-based baking-free ceramsite is characterized in that the baking-free ceramsite consists of a core part and a shell part; the core comprises Bayer process red mud, fly ash, steel slag micropowder and gypsum; the shell part comprises Bayer process red mud, slag cement, silica fume and a composite excitant; the composite excitant consists of sodium hydroxide and sodium silicate; the cylinder pressure strength of the baking-free ceramsite is more than or equal to 3.5MPa, and the bulk density is less than or equal to 1000kg/m 3 .
  2. 2. The baking-free ceramic aggregate according to claim 1, wherein the total blending amount of the bayer process red mud is 50-70 wt% based on the total mass of the baking-free ceramic aggregate.
  3. 3. The burn-free ceramsite of claim 1, wherein the core portion and the shell portion are bonded by an interfacial hydration reaction, and the shell portion has a thickness of 0.5mm to 2mm.
  4. 4. The baking-free ceramsite according to claim 1, wherein the mass ratio of sodium hydroxide to water glass in the composite activator is 1:1-1:3.
  5. 5. The baking-free ceramsite according to claim 1, wherein the specific surface area of the bayer process red mud is 30m 2 /g–50m 2 /g and the water content is less than or equal to 10wt%.
  6. 6. A method of preparing bayer process red mud-based baking-free ceramsite according to any one of claims 1 to 5, comprising: Drying and screening Bayer process red mud to obtain pretreated red mud; mixing the pretreated red mud, the fly ash, the steel slag micropowder and the gypsum, and adding water to stir to obtain a plastic core material; granulating the plastic core material to obtain wet core balls; Mixing the pretreated red mud, slag cement, silica fume and a composite activator, and adding water to stir to obtain shell slurry; coating the shell part slurry on the surface of the wet core ball to obtain a gradient wet ball; And sequentially carrying out normal-temperature rest curing and steam curing on the gradient wet spheres to obtain the Bayer process red mud-based baking-free ceramsite.
  7. 7. The method according to claim 6, wherein the steam curing is performed at a temperature of 60-80 ℃ for 12-24 hours, and the heating rate of the steam curing is less than or equal to 20 ℃ per hour.
  8. 8. The method according to claim 6, wherein the wet core spheres have a particle size of 4mm to 18mm.
  9. 9. The method of claim 6, wherein the plastic core material has a plasticity index of 10-15 and the shell portion slurry has a fluidity of 180-220 mm.
  10. 10. Use of the baking-free ceramic aggregate according to any one of claims 1 to 5 as a building thermal insulation aggregate or a water treatment filter material, wherein when the baking-free ceramic aggregate is used as the water treatment filter material, the baking-free ceramic aggregate is soaked in 5wt% hydrochloric acid solution for 2 hours and then washed to be neutral.

Description

Bayer process red mud-based baking-free ceramsite and preparation method and application thereof Technical Field The application belongs to the technical field of solid waste ceramsite, and particularly relates to a Bayer process red mud-based baking-free ceramsite, and a preparation method and application thereof. Background The red mud is a large amount of solid waste discharged by the aluminum industry, 0.8-1.5t of red mud is generated every 1t of aluminum oxide, the annual discharge amount is more than ten millions of tons, the pH is 10-13, and the long-term storage occupies the land and causes soil alkalization and heavy metal pollution. The traditional ceramsite is fired at high temperature by clay, so that high-quality mineral products are consumed, and the energy consumption and the carbon emission are high. The stacking density of the existing red mud ceramsite is more than 1100kg/m 3 when the cylinder pressure is more than 3MPa due to a homogeneous formula, the normal-temperature hydration reaction needs to be maintained for 7-14 days, the red mud doping amount is generally lower than 30wt%, the solid waste utilization rate is low, and the high-alkali red mud is easy to erode in an acidic environment, so that the application of water treatment is limited. Disclosure of Invention The embodiment of the application provides a Bayer process red mud-based baking-free ceramsite, a preparation method and application thereof, and aims to solve the technical problem of how to prepare gradient ceramsite with increased cylinder pressure intensity but not increased bulk density by using Bayer process red mud baking-free. In a first aspect, the embodiment of the application provides a Bayer process red mud-based baking-free ceramsite, which consists of a core part and a shell part in a gradient structure; the core comprises Bayer process red mud, fly ash, steel slag micropowder and gypsum; the shell part comprises Bayer process red mud, slag cement, silica fume and a composite excitant; the composite excitant consists of sodium hydroxide and sodium silicate; the cylinder pressure strength of the baking-free ceramsite is more than or equal to 3.5MPa, and the bulk density is less than or equal to 1000kg/m 3. Optionally, the total doping amount of the Bayer process red mud is 50-70 wt% based on the total mass of the baking-free ceramsite. Optionally, the core portion and the shell portion are bonded by an interfacial hydration reaction, and the shell portion has a thickness of 0.5mm to 2mm. Optionally, the mass ratio of the sodium hydroxide to the sodium silicate in the composite activator is 1:1-1:3. Optionally, the specific surface area of the Bayer process red mud is 30m 2/g–50m2/g, and the water content is less than or equal to 10wt%. In a second aspect, an embodiment of the present application provides a method for preparing bayer process red mud-based baking-free ceramsite according to any one of the first aspect, which is characterized in that the method includes: Drying and screening Bayer process red mud to obtain pretreated red mud; mixing the pretreated red mud, the fly ash, the steel slag micropowder and the gypsum, and adding water to stir to obtain a plastic core material; granulating the plastic core material to obtain wet core balls; Mixing the pretreated red mud, slag cement, silica fume and a composite activator, and adding water to stir to obtain shell slurry; coating the shell part slurry on the surface of the wet core ball to obtain a gradient wet ball; And sequentially carrying out normal-temperature rest curing and steam curing on the gradient wet spheres to obtain the Bayer process red mud-based baking-free ceramsite. Optionally, the temperature of the steam curing is 60-80 ℃ and the time is 12-24 hours, and the temperature rising rate of the steam curing is less than or equal to 20 ℃ per hour. Optionally, the wet core spheres have a particle size of 4mm to 18mm. Optionally, the plastic core material has a plasticity index of 10-15, and the shell portion slurry has a fluidity of 180-220 mm. In a third aspect, an embodiment of the present application provides a use of the baking-free ceramic aggregate according to any one of the first aspect as a building insulation aggregate or a water treatment filter material, wherein when the baking-free ceramic aggregate is used as the water treatment filter material, the baking-free ceramic aggregate is soaked in a 5wt% hydrochloric acid solution for 2 hours and then washed with water to be neutral. Compared with the prior art, the technical scheme provided by the embodiment of the application has the following advantages: Because bayer process red mud has low self-gelation activity and narrow grain size distribution, the bayer process red mud is a key factor for the contradiction that the baking-free ceramsite is required to increase the stacking density by the pressure intensity of a cylinder, and a core-shell gradient structure is constructed in th