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CN-121974575-A - Carbonized wet-milled steel slag-lithium slag-based composite admixture and application thereof

CN121974575ACN 121974575 ACN121974575 ACN 121974575ACN-121974575-A

Abstract

The invention relates to a carbonized wet-ground steel slag-lithium slag based composite admixture and application thereof, belonging to the technical field of solid waste recycling and green building materials. The composite admixture is liquid slurry prepared from steel slag powder and lithium slag powder through carbonization-wet grinding synergistic activation technology. The main process is to synchronously carry out mechanical grinding and chemical carbonization reaction, and assist micro-bubbles generated by decomposing ammonium bicarbonate to strengthen mass transfer. In the process, free oxide in the steel slag is converted into stable carbonate, a silicon-aluminum network of the lithium slag is depolymerized, and the two are cooperated to generate compact calcite, ettringite, AFm-like gelling products and the like, so that the activity of the material is improved, and meanwhile, the problems of poor stability and high sulfur expansion risk are fundamentally solved. The product can be used as a functional liquid cementing material, and can be added in place of part of mixing water during concrete stirring, and the high-performance low-carbon concrete can be prepared after curing, so that the large-scale high-value utilization of steel slag and lithium slag is realized.

Inventors

  • HUANG YIXIONG
  • WANG ZIJIE
  • XIONG LONG
  • GUO YULIN
  • YANG SHIXU
  • ZHANG SHICHAO

Assignees

  • 中建西部建设集团第八(上海)有限公司

Dates

Publication Date
20260505
Application Date
20260408

Claims (10)

  1. 1. The carbonized wet-milled steel slag-lithium slag based composite admixture is characterized by being liquid slurry prepared by synchronous carbonization-wet milling reaction of the following components in parts by weight, water and optionally a polycarboxylic acid high-efficiency water reducer, wherein the mass ratio of liquid to solid in the liquid slurry is (1.5-2.5): 1; 60-70 parts of lithium slag powder; 30-40 parts of steel slag powder; 1-3 parts of ammonium bicarbonate.
  2. 2. The composite admixture according to claim 1, wherein the steel slag powder has an initial median particle diameter D 50 of 45-55 μm, the lithium slag powder has an initial median particle diameter D 50 of 25-35 μm, and the slurry solid phase obtained after carbonization wet milling has a median particle diameter D 50 of 3-5 μm.
  3. 3. The composite admixture according to claim 1 or 2, wherein the original chemical composition of the steel slag powder comprises ：SiO 2 14.0-18.0%、Al 2 O 3 4.0-6.0%、Fe 2 O 3 24.0-28.0%、CaO36.0-40.0%、MgO6.0-8.0%; in mass fraction based on the total weight of the steel slag powder and the original chemical composition of the lithium slag powder comprises in mass fraction based on the total weight of the lithium slag powder ：SiO 2 56.0-60.0%、Al 2 O 3 18.0-22.0%、Fe 2 O 3 1.0-2.0%、CaO6.0-8.0%、SO 3 6.0-8.0%.
  4. 4. The composite admixture according to claim 1 or 2, wherein the polycarboxylic acid type high efficiency water reducer accounts for 0.3-0.5% of the total solid mass in the composite admixture.
  5. 5. A method of preparing the composite admixture of any one of claims 1-4, comprising the steps of: s1, premixing raw materials, namely uniformly dry-mixing lithium slag powder and steel slag powder to obtain a mixture; s2, carbonization-wet milling activation, namely transferring the mixture obtained in the step S1 into a closed grinding tank of a ball mill, adding water to adjust the liquid-solid mass ratio to 1.5-2.5, introducing carbon dioxide gas with the purity not lower than 99.5% into the grinding tank, stably maintaining the gauge pressure in the tank at 0.1-0.3MPa through a pressure control system, adding ammonium bicarbonate and a polycarboxylic acid high-efficiency water reducer accounting for 0.3-0.5% of the total mass of solids into a grinding system before starting the ball mill, and synchronously carrying out mechanical grinding and carbonization reaction on the materials, wherein the whole process lasts for 40-60min; S3, post-treatment of the product, namely taking out the obtained uniform and stable slurry after the reaction is finished, and sealing and storing the slurry for later use.
  6. 6. The process according to claim 5, wherein in step S2, the grinding medium used is zirconia balls, and the ratio of the total mass to the mass of the mixture obtained in step S1 is (1-2): 1.
  7. 7. The preparation method according to claim 6, wherein the particle size of the zirconia grinding balls is in the range of 0.6-1.4mm, and the sum of the stacking volume of the zirconia grinding balls and the slurry volume formed by the mixture obtained in the step S1 and water accounts for 60% -75% of the effective volume of the ball milling tank.
  8. 8. Use of a composite admixture according to any one of claims 1-4 as a functional liquid cement for the preparation of high performance low carbon concrete.
  9. 9. The use of claim 8, wherein the composite admixture is added in place of a portion of the mix water during concrete mixing.
  10. 10. The preparation method of the high-performance low-carbon coagulation is characterized by comprising the following steps of: a1, preparing the components, namely preparing the composite admixture as a liquid cementing material together with cement clinker, aggregate and an additive according to any one of claims 1-4; A2, controlling the adding and mixing amount of the slurry, namely directly adding the composite admixture into stirring equipment and replacing part of mixing water in the process of stirring concrete, wherein the adding amount of the composite admixture is 15-20% of the total gel material mass by the mass of solid phase contained in the slurry; A3, homogenizing and stirring, namely supplementing the rest mixing water and the additive, wherein the total stirring time is not less than 120 seconds until a uniform and segregation-free concrete mixture is obtained; and A4, molding and curing, namely pouring, vibrating and compacting the mixture, and curing to finally prepare the high-performance low-carbon concrete.

Description

Carbonized wet-milled steel slag-lithium slag-based composite admixture and application thereof Technical Field The invention belongs to the technical field of building materials, relates to the technology of solid waste recycling and green building materials, and in particular relates to a carbonized wet-milled steel slag-lithium slag-based composite admixture and application thereof. Background The limestone is consumed in a large amount and CO 2 is released in the silicate cement production process, and the limestone is one of main sources of carbon emission in the building field. In order to realize low carbonization development, the preparation of mineral admixtures by using industrial solid wastes to replace part of cement clinker has become an important technical path for reducing the carbon footprint. Steel slag and lithium slag are typical bulk solid wastes, have large yield and low utilization rate, but are widely studied for cement-based materials in recent years because of the potential gelling component. The main components of the steel slag are CaO and SiO 2, and the steel slag contains hydraulic minerals such as dicalcium silicate and the like. However, because the cooling is slow after smelting, C 2 S exists in a gamma crystal form with stable thermodynamics, the hydration activity is obviously lower than that of beta-C 2 S in common cement, and meanwhile, the steel slag contains more inert RO phases, so that the steel slag is difficult to participate in hydration reaction. The more remarkable problem is that the concrete often contains free calcium oxide and free magnesium oxide, is slowly hydrated in the later period of concrete hardening, generates volume expansion, influences long-term volume stability and limits engineering application safety. The lithium slag is mainly amorphous SiO 2 and Al 2O3, has a certain volcanic ash activity, but lacks self-hydraulicity, and needs to rely on an external alkaline environment to excite a reaction, so that early strength development is slow. The content of SO 3 in partial lithium slag is higher, and the sulfate excitation function can be exerted when the amount is proper, but the excessive amount can increase the water demand of the slurry, deteriorate the workability, induce the formation of delay ettringite under the condition of temperature and humidity change, and cause irreversible expansion cracking. In addition, the lithium slag particles are thicker, the interior is porous, the compactness of the matrix is easy to be weakened when the specific surface area is large but the reaction is insufficient, and the adverse effects on the durability such as the impermeability, the freezing resistance and the like of the concrete are generated. In view of the obvious defect of single solid waste performance, the preparation of the composite mineral admixture by compounding the steel slag and the lithium slag becomes a feasible strategy. This strategy aims at improving the overall gelling performance and reducing the clinker dosage by complementing the chemical composition and the physical characteristics of the two. However, the prior art schemes still have shortcomings in terms of activity excitation efficiency, volume stability control and engineering applicability. For example, chinese patent application CN117105554a discloses a process for preparing lithium slag and steel slag co-ground to 400-500 mesh, and controlling the mixture SO 3 to be 3.0% or less to reduce the risk of expansion. According to the scheme, particle refinement and component dilution are realized by means of physical grinding, but effective chemical activation is not carried out on inert gamma-C 2 S and RO phases in steel slag, and the risk of delay ettringite generation in long-term service in a high-sulfate environment cannot be eliminated, so that the early activity of the admixture is limited to be improved, and the effect of improving microstructure compactness and durability is insufficient. The Chinese patent CN115724608B adopts phosphoric acid/alcohol solution and organic silane coupling agent to modify the surface of steel slag, and is compounded with AOD slag, nickel-iron slag, fly ash and a small amount of lithium slag. Although the reactivity is improved to a certain extent, the process is complex, the reagent cost is high, the introduction of organic matters possibly brings environmental burden, the industrialized popularization is not facilitated, meanwhile, the lithium slag is low in proportion, and the synergistic effect of the lithium slag and the steel slag is not fully excavated. The Chinese patent CN114213051B uses the sulfate with 4.2-5.8% of the specific lithium slag to excite the activity of the steel slag. The method has strict requirements on raw material sources and poor adaptability, and the system has higher sulfate content and still has the risk of delaying ettringite formation to initiate expansion. In addition, effective control measures are not a