A dispersant for high-volume carbon-fixed steel slag powder cementitious materials and its preparation method

Abstract

This invention relates to the field of building materials technology, and more particularly to a dispersant for high-volume solid carbon steel slag powder cementitious materials and its preparation method. The dispersant is a multi-block comb polymer, and the main chain of the multi-block comb polymer, from one end to the other along the chain direction, sequentially includes a first rheology-regulating block R1, a steel slag affinity block S, a cement dispersion block C, and a second rheology-regulating block R2. This invention can be used to adjust the cohesiveness, bleeding tendency, and air content of high-volume solid carbon steel slag powder concrete, achieving directional recognition and selective adsorption on the surface of solid carbon steel slag powder. It also provides efficient dispersion and slump retention for cement clinker and hydration product particles. Simultaneously, this invention can reduce the viscosity of concrete, while avoiding bleeding and segregation. The air bubbles are small and dense, improving the fluidity and pumpability of the mixture, while ensuring good early strength and long-term durability.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a dispersant for high-volume carbon-fixed steel slag powder cementitious materials and its preparation method. Background Technology

[0002] As an important direction for the resource utilization of industrial solid waste, carbon-fixed steel slag powder has attracted widespread attention in the field of concrete auxiliary cementitious materials due to its wide availability, low cost, and certain potential cementitious activity. However, when the content of carbon-fixed steel slag powder exceeds 5%, it causes workability problems in concrete mixtures, which seriously restricts large-scale promotion. Among these problems, bleeding segregation and poor cohesion are among the most prominent engineering pain points. From a material perspective, after crushing and grinding, the solidified carbon steel slag powder exhibits significant irregularity in particle morphology, with sharp edges and a rough surface. Simultaneously, its particle size distribution is coarse (insufficient fine powder content and concentrated particle size distribution), resulting in poor compatibility with the particle size distribution of cement clinker and aggregates. This leads to increased porosity within the mixture, insufficient slurry encapsulation, and consequently, bleeding. Furthermore, the surface of solidified carbon steel slag powder contains numerous active sites and hydrophilic groups, giving it a significantly stronger water absorption capacity than traditional auxiliary cementitious materials such as slag powder and fly ash. This narrows the water demand sensitivity range of the mixture: insufficient water prevents adequate wetting of the steel slag particles, easily forming dry clumps, and increased inter-particle friction leads to deteriorated cohesion; excessive water disrupts the bonding balance between the slurry and aggregates, causing segregation and stratification problems such as aggregate settling and slurry floating. This problem directly leads to surface sanding and the formation of interconnected bleeding channels in the concrete after pouring. After hardening, this not only results in high porosity and insufficient density, but also further induces a decrease in strength, a decline in durability indicators such as impermeability and frost resistance, and even causes early structural cracks, seriously affecting project quality and service life. Therefore, developing targeted control technologies to address the bleeding segregation and poor cohesion issues of high-content solid carbon steel slag powder cementitious materials is a key technological breakthrough for promoting its efficient and stable application in concrete.

[0003] To increase the content of carbon-fixed steel slag in concrete while simultaneously considering strength and workability, researchers and engineers have conducted a series of exploratory studies related to admixtures. Chinese patent CN103979828B discloses a functional regulator for steel slag-based concrete admixtures. This technology uses a polyether-type polycarboxylate high-efficiency water-reducing agent combined with a composite active activator, retarder, and composite air-entraining agent. When the steel slag content reaches 40% or more, this "combination punch" of admixtures improves the workability and strength performance at various ages of fresh steel slag-based concrete. Chinese patent CN113979653A proposes... A steel slag cementitious material and its preparation method were proposed. Liquid admixtures such as polyethylene glycol, sorbitol, diethanol monoisopropanolamine, and polycarboxylic acid were introduced into the steel slag-based cementitious system to stimulate the activity of steel slag and improve the performance of the mixture. However, polycarboxylic acid was only regarded as a conventional water-reducing component. Chinese patent CN116177960A proposed a method for preparing ready-mixed concrete by wet carbon fixation of water slag. Under the premise that carbon-fixed water slag replaces part of the cement, the admixture is limited to one of naphthalene-based water-reducing agent or polycarboxylic acid water-reducing agent. It focuses more on the carbon fixation process and the improvement of water slag activity, without making a targeted breakthrough in the molecular structure of the water-reducing agent itself. In general, existing patented technologies focus primarily on pretreatment processes for steel slag or carbonized steel slag, the proportioning of cementitious materials, and composite admixture systems. Polycarboxylate superplasticizers are used as "general-purpose water-reducing components," relying mainly on dosage adjustments and empirical compounding with activators, retarders, and air-entraining agents to compensate for the workability deficiencies of high-dosage steel slag systems. They have not yet addressed the unique interfacial characteristics of carbonized steel slag powder, such as "high alkalinity, coexistence of multiphase minerals, multi-metal oxides, and carbonates," to construct specialized dispersants with steel slag affinity groups. Furthermore, they lack molecular structure design approaches to address the problems of "high water demand, severe sacrificial adsorption, and coexistence of bleeding segregation and poor cohesion" in high-dosage carbonized steel slag powder cementitious systems. No solutions have yet been proposed for these technical issues. Summary of the Invention

[0004] To address the problems in related technologies, this invention proposes a dispersant for high-volume carbon-fixed steel slag powder cementitious materials and its preparation method, thereby overcoming the aforementioned technical problems in existing related technologies. The purpose of this invention is to enrich the first rheology-regulating block R1 and the second rheology-regulating block R2 with sulfonic acid monomer D, zwitterionic monomer E, and hydrophobic regulating monomer F, which are used to adjust the cohesiveness, bleeding tendency, and air content of high-volume carbon-fixed steel slag powder concrete; the steel slag affinity block S is enriched with phosphorus-strong complexing monomer G and short-side-chain polyether macromonomer B1. This invention enables directional identification and selective adsorption of carbon-fixed steel slag powder on its surface. The cement dispersion block C is mainly composed of long-side-chain polyether macromonomer B2, unsaturated carboxylic acid monomer H, and alkoxysilane monomer I in a comb-like structure, providing efficient dispersion and slump retention for cement clinker and hydration product particles. When applied to a high-volume cementitious system where carbon-fixed steel slag powder replaces 30-50% of cement, the dispersant of this invention can reduce the viscosity of concrete, while avoiding bleeding and segregation. The bubbles are small and dense, improving the fluidity and pumping stability of the mixture.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a dispersant for high-volume solid carbon steel slag powder cementitious materials, wherein the dispersant is a multi-block comb polymer, and the main chain of the multi-block comb polymer includes, from one end to the other, a first rheology regulating block R1, a steel slag affinity block S, a cement dispersing block C, and a second rheology regulating block R2 in sequence along the chain direction; The dispersant satisfies the following conditions: (1) The first rheology control block R1 and the second rheology control block R2 can be random copolymers containing sulfonic acid monomer D, zwitterionic monomer E and hydrophobic control monomer F, respectively. The molar fractions of sulfonic acid monomer D, zwitterionic monomer E and hydrophobic control monomer F in the first rheology control block R1 and the second rheology control block R2 are denoted as d, e and f, respectively. (2) The steel slag affinity block S is a random copolymer of phosphorus-containing strong complexing monomer G and short-side chain polyether macromonomer B1, and the molar fractions of phosphorus-containing strong complexing monomer G and short-side chain polyether macromonomer B1 are g and b1, respectively. (3) The cement dispersion block C is a random copolymer of long side-chain polyether macromonomer B2, unsaturated carboxylic acid monomer H and alkoxysilane monomer I, and the molar fractions of the long side-chain polyether macromonomer B2, unsaturated carboxylic acid monomer H and alkoxysilane monomer I are b2, h and i, respectively; (4) d: e: f: g: b1: b2: h: i= (12~20): (4~8): 2: (2~6): (1~4): (1~2): (2~5): (1~2).

[0006] To achieve the above objectives, the present invention also provides the following technical solution: A method for preparing a dispersant for a high-volume carbon-fixed steel slag powder cementitious material includes the following steps: (1) Preparation of the first rheology-controlled block R1: 5 mol of deionized water and 0.001 mol of RAFT reagent were added to the reactor. Then, 0.06-0.10 mol of sulfonic acid monomer D, 0.02-0.04 mol of zwitterionic monomer E and 0.01 mol of hydrophobic control monomer F were added. Water-soluble initiator was added at 50-80℃ under the protection of inert gas N2 to carry out free radical polymerization in aqueous solution to obtain R1 block macromolecular chain with chain transfer structure at the end group. (2) Construction of steel slag affinity block S: In the R1 block macromolecular chain obtained in step (1), 0.02~0.06 mol of phosphorus-containing strong complexing monomer G and 0.01~0.04 mol of short side chain polyether macromonomer B1 are continuously added. At 50~80℃, 0.001~0.005 mol of water-soluble initiator is added and polymerization is continued for 0.5~3h to obtain R1–S block polymer with chain transfer structure at the end group; (3) Constructing cement-dispersed block C: In the R1–S block polymer obtained in step (2), add 0.01~0.02 mol of long side-chain polyether macromonomer B2, 0.02~0.05 mol of unsaturated carboxylic acid monomer H and 0.01~0.02 mol of alkoxysilane monomer I, and add 0.001~0.005 mol of water-soluble initiator at 55~85℃ for 1~4h to obtain R1–S–C block polymer with chain transfer structure at the end group; (4) Constructing the second rheologically controlled block R2: In the R1–S–C block polymer obtained in step (3), add 0.06~0.10 mol of sulfonic acid monomer D, 0.02~0.04 mol of zwitterionic monomer E and 0.01 mol of hydrophobic control monomer F, and add 0.001~0.005 mol of water-soluble initiator at 55~85℃ for 0.5~3h to obtain R1–S–C–R2 multiblock comb polymer; (5) Post-treatment: After the reaction is completed, continue to keep warm for 0.5~3h to reduce the residual monomer content, then cool to room temperature, adjust the pH to 4~7 with sodium hydroxide, freeze dry to obtain a light yellow solid, which is the dispersant for high-volume solid carbon steel slag powder cementitious materials.

[0007] Preferably, the water-soluble initiator is one or a combination of ammonium persulfate, sodium persulfate, potassium persulfate, a persulfate-sulfite complex initiation system, and azobisisobutyramidine hydrochloride.

[0008] Preferably, the controllable chain transfer agent RAFT reagent is one or more combinations of dithiobenzoate, trithiocarbonate, trithiocarbonate, and dithiocarbamate.

[0009] Preferably, the sulfonic acid monomer D is one or more combinations of 2-acrylamide-2-methylpropanesulfonic acid, 3-acrylamide-3-methylbutanesulfonic acid, 2-acryloyloxyethanesulfonic acid, 2-methacryloyloxyethanesulfonic acid, 2-sulfoethylmethacrylic acid, 3-sulfopropylmethacrylic acid, ethylene sulfonic acid, styrene sulfonic acid, and their salts.

[0010] Preferably, the zwitterionic monomer E is one or a combination of 2-methacryloyloxyethyl phosphoric acid choline, 2-acryloyloxyethyl phosphoric acid choline, carboxybetaine methacrylate, carboxybetaine acrylate, sulfobetaine methacrylate, and 3-(N,N-dimethyl(methacrylamidopropyl)ammonium)propanesulfonic acid betaine.

[0011] Preferably, the hydrophobic regulating monomer F is one or more combinations of lauryl methacrylate, stearyl methacrylate, 2-ethylhexyl acrylate, n-hexyl acrylate, dodecyl acrylate, styrene, p-methylstyrene, and isobornyl methacrylate.

[0012] Preferably, the phosphorus-containing strong complexing monomer G is one or more combinations of methacryloyloxyethide diphosphonic acid, acryloyloxyethide diphosphonic acid, methacryloylamino diphosphonic acid, glutamic acid diphosphonate methacrylate, 4-(bis(diethoxyphosphoryl)methyl)phenyl methacrylate, 2-hydroxyethyl methacrylate diphosphate, and allyl diphosphate.

[0013] Preferably, the short-chain polyether macromonomer B1 is one of polyether (meth)acrylate or vinyl ether with a number average molecular weight of 200-800 and a polyoxyethylene repeating unit number of 5-20; the long-chain polyether macromonomer B2 is one of polyether (meth)acrylate or vinyl ether with a number average molecular weight of 800-3000 and a polyoxyethylene repeating unit number of 20-70.

[0014] Preferably, the unsaturated carboxylic acid monomer H is one or more of acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, and their water-soluble salts; the alkoxysilane monomer I is one or more of 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-acryloyloxypropyltriethoxysilane, methacryloyloxymethyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(2-methoxyethoxy)silane, and allyltrimethoxysilane.

[0015] Compared with the prior art, the beneficial effects of the present invention are: (1) This invention is a dispersant for cementitious materials with high dosage of carbon-fixed steel slag powder and its preparation method. Through the design of R1–S–C–R2 multi-block comb structure, this invention realizes for the first time the spatial functional partitioning of rheological regulation-steel slag recognition-cement dispersion in the polycarboxylic acid dispersant molecule, so that the dispersant has clear interface orientation and synergistic effect in the system of high dosage of carbon-fixed steel slag powder. (2) This invention is a dispersant for high-volume solid carbon steel slag powder cementitious materials and its preparation method. It utilizes the synergistic effect of phosphorus-containing strong complexing monomer G in the affinity block S of steel slag and short-chain polyether macromonomer B1 to enrich the molecules on the surface of solid carbon steel slag powder without forming an excessively thick polymer layer. This inhibits sacrificial adsorption and avoids passivating the subsequent activity of steel slag, thus reserving sufficient reaction sites for steel slag to participate in hydration and carbonization reactions. (3) The present invention is a dispersant for a high-volume solid carbon steel slag powder cementitious material and its preparation method. The sulfonic acid monomer D, zwitterionic monomer E and hydrophobic regulating monomer F in the first rheology regulating block R1 and the second rheology regulating block R2 construct a rheology buffer zone, which not only ensures the fluidity required for high water reduction rate, but also improves cohesiveness and inhibits bleeding and segregation by adjusting the pore solution structure and interfacial tension, thus avoiding the phenomenon of large slump but severe segregation or rapid slump loss. (4) This invention is a dispersant for high-volume solid carbon steel slag powder cementitious materials and its preparation method. The long side chain polyether macromonomer B2 and unsaturated carboxylic acid monomer H in the cement dispersion block C provide a stable comb-shaped structure. Combined with the sulfonic acid monomer D and zwitterionic monomer E in the first rheology-controlled block R1 and the second rheology-controlled block R2, it can maintain molecular extension and good solubility in a pH>12 and high Ca²⁺ / Na⁺ environment, thereby improving slump retention performance. (5) This invention is a dispersant for cementitious materials with large dosage of solid carbon steel slag powder and its preparation method. The introduction of hydrophobic control monomer F reduces the stability of large bubbles in the dispersant, while the linear molecular structure improves the elasticity of small bubble liquid film. The multi-block structure forms a moderate lubrication layer + cohesive network in the flow field, which improves the rheological behavior and anti-clogging ability during the pumping process. (6) This invention is a dispersant for high-volume solid carbon steel slag powder cementitious materials and its preparation method. This invention adopts a sequential segmented polymerization process with water as the medium. It can be achieved on the basis of existing polycarboxylate dispersant production lines by adding chain transfer agent RAFT reagent and adjusting monomer feeding strategy. No complicated equipment modification is required, and it is suitable for industrial promotion. Detailed Implementation

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention.

[0017] Example 1 This invention proposes a technical solution for a dispersant for high-volume carbon-fixed steel slag powder cementitious materials and its preparation method: In a reactor equipped with a stirrer, reflux condenser, and nitrogen protection device, 5.0 mol of deionized water and 0.001 mol of benzyl dithiobenzoate RAFT reagent were added. After stirring until homogeneous, dissolved oxygen was removed by bubbling under nitrogen for 30 min. Subsequently, 0.08 mol of 2-acrylamide-2-methylpropanesulfonic acid (D), 0.03 mol of 2-methacryloyloxyethyl phosphocholine (E), and 0.01 mol of isoborneol methacrylate (F) were added sequentially. The temperature was raised to 65 °C, and 0.003 mol of ammonium persulfate was added dropwise as an initiator. The reaction was carried out under nitrogen protection for 2 h to obtain an aqueous solution of R1 block macromolecular chains with chain transfer structures at the end groups. Subsequently, a small amount of nitrogen was bubbled into the same reaction system, and 0.04 mol of methacryloyloxyethylidene diphosphonic acid (G) and 0.02 mol of a polyoxyethylene compound with a number average molecular weight of approximately 400 and approximately 9 repeating units were added. Polyoxyethylene methacrylate (B1) was added, followed by the addition of 0.002 mol of ammonium persulfate, and polymerization was initiated for 2 h to obtain an R1–S block polymer solution. While maintaining the system temperature at 70 °C, 0.015 mol of polyoxyethylene methacrylate (B2) with a number-average molecular weight of approximately 1500 and approximately 35 repeating units of polyoxyethylene, 0.03 mol of acrylic acid (H), and 0.015 mol of 3-methacryloyloxypropyltrimethoxysilane (I) were added, followed by the addition of 0.002 mol of ammonium persulfate and reaction for 2 h to obtain an R1–S–C block polymer. Finally, in the same reactor, 0.08 mol of 2-acrylamido-2-methylpropanesulfonic acid (D), 0.03 mol of 2-methacryloyloxyethyl phosphocholine (E), and 0.01 mol of isoborneol methacrylate (F) were added, followed by the addition of 0.002 mol of ammonium persulfate, and polymerization was carried out at 70 °C. The polymerization was continued for 1.5 h to obtain an aqueous solution of R1–S–C–R2 multiblock comb polymer. After heating was stopped, the solution was kept at a constant temperature for 1 h to reduce the residual monomer content. The solution was then cooled to room temperature, and the pH was adjusted to 6.0±0.5 with sodium hydroxide solution. The solution was then freeze-dried to remove moisture and obtain a light yellow solid powder, which is the dispersant for the high-dosage solid carbon steel slag powder cementitious material of this embodiment.

[0018] Example 2 5.0 mol of deionized water and 0.001 mol of 2-cyano-2-propyldodecyl trithiocarbonate (RAFT) reagent were added to a reactor. The mixture was stirred at room temperature for 20 min, then purged with nitrogen for 30 min. The temperature was raised to 60 °C, and 0.06 mol of 2-acryloyloxyethanesulfonic acid (D), 0.02 mol of carboxybetaine methacrylate (E), and 0.01 mol of lauryl methacrylate (F) were added to the system. Then, 0.003 mol of sodium persulfate was added as an initiator, and polymerization was carried out at 60 °C for 2 h to obtain the first rheology-controlled block prepolymer R1. Subsequently, 0.03 mol of methacryloyloxyethionide diphosphonic acid and 0.01 mol of glutamic acid diphosphonate methacrylate (total 0.04 mol, G) and 0.02 mol of polyoxyethylene methacrylate (B1) with a number average molecular weight of approximately 300 were added sequentially to the same reaction system, followed by the addition of 0.002 mol of... Sodium persulfate was polymerized at 65 °C for 2 h to obtain an R1–S block polymer. The temperature was further increased to 75 °C, and 0.02 mol of polyoxyethylene methacrylate (B2) with a number average molecular weight of approximately 2000, 0.04 mol of methacrylic acid (H), and 0.01 mol of 3-acryloyloxypropyltriethoxysilane (I) were added to the system. 0.002 mol of sodium persulfate was then added, and polymerization was continued at 75 °C for 2.5 h to obtain an R1–S–C block polymer. Subsequently, 0.09 mol of 2-acryloyloxyethanesulfonic acid (D), 0.03 mol of carboxybetaine methacrylate (E), and 0.01 mol of lauryl methacrylate (F) were added at 75 °C, and 0.002 mol of sodium persulfate was added to initiate polymerization for 1.5 h, yielding an aqueous solution of an R1–S–C–R2 multiblock comb polymer. After heating was stopped, stirring and maintaining the temperature for 1 hour were continued. After cooling to room temperature, the pH was adjusted to 4.5–5.5 with sodium hydroxide, and then freeze-dried to obtain the dispersant solid powder of this embodiment.

[0019] Example 3 5.0 mol of deionized water and 0.001 mol of S-propyl-N,N-diethyldithiocarbamate RAFT reagent were added to a 1 L reactor equipped with a mechanical stirrer and condenser. After stirring for 30 min under nitrogen protection, the mixture was heated to 65 °C, and 0.10 mol of 3-acrylamide-3-methylbutanesulfonic acid (D), 0.04 mol of sulfobetaine methacrylate (E), and 0.01 mol of 2-ethylhexyl acrylate (F) were added. Then, 0.004 mol of ammonium persulfate was added to initiate polymerization for 2 h, yielding the first rheology-controlled block R1 solution. In the same system, 0.05 mol of acryloyloxyethide diphosphonic acid (G) and 0.02 mol of polyoxyethylene methacrylate (B1) with a number-average molecular weight of approximately 600 were added sequentially, followed by the addition of 0.002 mol of ammonium persulfate. Polymerization was carried out at 70 °C for 2 h to obtain R1–S. Block polymers were prepared by heating the system to 80 °C and adding 0.02 mol of polyoxyethylene methacrylate (B2) with a number-average molecular weight of approximately 2400, 0.05 mol of itaconic acid (H), and 0.015 mol of methacryloyloxymethyltrimethoxysilane (I), followed by 0.002 mol of ammonium persulfate. The polymerization was carried out at 80 °C for 3 h to obtain the R1–S–C block polymer. Subsequently, 0.10 mol of 3-acrylamide-3-methylbutanesulfonic acid (D), 0.04 mol of sulfobetaine methacrylate (E), and 0.01 mol of 2-ethylhexyl acrylate (F) were added, followed by 0.002 mol of ammonium persulfate. The polymerization was carried out at 80 °C for 1.5 h to obtain an aqueous solution of the R1–S–C–R2 multiblock comb polymer. After stopping heating, stirring was continued for 1 h, and the mixture was cooled to room temperature. The pH was adjusted to 6.0 with sodium hydroxide. After freeze-drying, a light yellow powder is obtained, which is the dispersant of this embodiment.

[0020] Example 4 This invention proposes a technical solution for a dispersant and its preparation method for a high-dosage solid carbon steel slag powder cementitious material: 5.0 mol of deionized water and 0.001 mol of RAFT reagent (4-cyano-4-(ethyltrithiocarbonate-based)valerate) are added to a reactor. The mixture is stirred for 25 min under nitrogen protection, heated to 60 °C, and then 0.07 mol of 2-sulfoethyl methacrylate (D), 0.03 mol of 3-(N,N-dimethyl(methacrylamidopropyl)ammonium)propanesulfonic acid betaine (E), and 0.01 mol of styrene (F) are added. Subsequently, 0.003 mol of ammonium persulfate is added, and polymerization is carried out at 60 °C for 2 h to obtain a first rheology-controlled block polymer solution (R1). Then, 0.03 mol of 4-(bis(diethoxyphosphoryl)methyl)phenyl methacrylate (G) and 0.02 mol of a dispersant with a number average molecular weight of approximately 500 are added in a single step. Polyoxyethylene vinyl ether (B1) was polymerized with 0.002 mol of ammonium persulfate at 65 °C for 2 h to obtain R1–S block polymer. The temperature was further increased to 75 °C, and 0.015 mol of polyoxyethylene methacrylate (B2) with a number-average molecular weight of approximately 1800, 0.03 mol of fumaric acid (H), and 0.015 mol of vinyltrimethoxysilane (I) were added to the system. 0.002 mol of ammonium persulfate was added, and the reaction was carried out at 75 °C for 2.5 h to obtain R1–S–C block polymer. Then, 0.07 mol of 2-sulfoethyl methacrylate (D), 0.03 mol of 3-(N,N-dimethyl(methacrylamidopropyl)ammonium)propanesulfonate betaine (E), and 0.01 mol of styrene (F) were added to the reactor, and 0.002 mol of ammonium persulfate was added. The reaction was carried out at 75 °C. The polymerization was carried out for 1.0 h to obtain a multi-block comb polymer solution of R1–S–C–R2; after stopping the reaction, the solution was kept at a constant temperature for 0.5 h, cooled to room temperature, and the pH was adjusted to 5.0–6.0 with sodium hydroxide. The solution was then freeze-dried to obtain the solid dispersant product of this embodiment.

[0021] Example 5 This invention proposes a technical solution for a dispersant for high-volume carbon-fixed steel slag powder cementitious materials and its preparation method: In a reactor equipped with a stirrer and temperature control device, 5.0 mol of deionized water and 0.001 mol of bis(carboxymethyl)trithiocarbonate RAFT reagent were added. After stirring for 30 min under nitrogen protection, the mixture was heated to 65 °C. 0.09 mol of sodium ethylene sulfonate (D), 0.03 mol of carboxybenzene acrylate (E), and 0.01 mol of dodecyl acrylate (F) were added to the system, followed by 0.003 mol of ammonium persulfate. Polymerization was carried out at 65 °C for 2 h to obtain the first rheology-controlled block polymer solution R1. Subsequently, 0.04 mol of methacryloylamino bisphosphonic acid (G) and 0.02 mol of polyoxyethylene methacrylate (B1) with a number-average molecular weight of approximately 700 were added, followed by 0.002 mol of ammonium persulfate. Polymerization was carried out at 70 °C for 2 h to obtain the R1–S block polymer. Finally, 0.02 mol of... Polyoxyethylene methacrylate (B2) with a number average molecular weight of approximately 2200, 0.04 mol of acrylic acid (H), and a total of 0.02 mol of alkoxysilane monomer I (0.01 mol of 3-methacryloyloxypropyltriethoxysilane and 0.01 mol of vinyltriethoxysilane) were polymerized at 75 °C for 3 h to obtain an R1–S–C block polymer. Then, 0.09 mol of sodium ethylene sulfonate (D), 0.03 mol of carboxybetaine acrylate (E), and 0.01 mol of dodecyl acrylate (F) were added at 75 °C, followed by another 0.002 mol of ammonium persulfate. The polymer was then polymerized at 75 °C for 1.5 h to complete the second rheology-controlled block grafting, resulting in an R1–S–C–R2 multiblock comb polymer solution. After heating was stopped, stirring was continued for 1 hour. h, cooled to room temperature, pH adjusted to 4.5-6.5 with sodium hydroxide, and freeze-dried to obtain a pale yellow solid, which is the dispersant of this embodiment.

[0022] Applications and Performance To systematically evaluate the applicability of the five dispersants of this invention in high-dosage carbon-fixed steel slag powder cementitious systems and their performance differences compared with commercially available similar products, P·O 42.5 ordinary Portland cement was selected as the reference cementitious material. The carbon-fixed steel slag powder was steel slag powder pre-carbonized by CO2, with a specific surface area of ​​approximately 450 m² / kg. The fine aggregate was river sand (fineness modulus 2.7), and the coarse aggregate was crushed stone (particle size 5–20 mm). All concrete groups used the same mix proportions (by mass): total cementitious material 450 kg / m³, including 270 kg / m³ cement and 180 kg / m³ carbon-fixed steel slag powder (replacement rate 40%); water 150 kg / m³ (w / b = 0.33); sand 750 kg / m³; and aggregate 1040 kg / m³. Seven groups of experiments were set up: control group 1 was mixed with dispersant 1 of the cementitious system with large amount of solid carbon steel slag powder, control group 2 was mixed with dispersant 2 of the cementitious system with large amount of solid carbon steel slag powder, and dispersants P-1 to P-5 were prepared in Examples 1 to 5. The initial state of concrete mixtures was similar for each group of dispersants by adjusting the dosage. All other raw materials and mixing conditions were completely consistent.

[0023] Coarse and fine aggregates and all cementitious materials were added to a mixer and dry-mixed for 30 seconds. Then, the pre-dissolved dispersant solution and the remaining mixing water were added, and the mixture was stirred at low speed for 60 seconds, followed by high speed for 90 seconds. The performance of the fresh mix was tested immediately after mixing. Slump and slump spread were measured within 5 minutes of mixing, according to GB / T 50080. The concrete was then allowed to stand at room temperature for 30 minutes before a second slump measurement to evaluate slump retention performance. Simultaneously, the apparent cohesiveness and bleeding segregation of the mixture were visually observed and recorded (observing for obvious bleeding channels, aggregate settling, or paste floating). The air content of the concrete was tested using a pressure air content meter according to GB / T 50080. The compressive strength test used 150mm×150mm×150mm cubic specimens, with no fewer than 3 specimens per group. The specimens were cured under standard conditions of 20±2℃ and relative humidity ≥95% for 28 days according to GB / T 50081 before the compressive strength was determined. The impermeability was assessed according to the method specified in GB / T50082, with evaluation based on a combination of seepage height and impermeability grade. A comparison of the performance of different dispersant systems in high-volume carbon-fixing steel slag powder concrete is shown in Table 1 below.

[0024] Table 1. Performance Comparison of Different Dispersant Systems in Concrete with High-Concentration Carbon-Fixed Steel Slag Powder As shown in Table 1, under the conditions of a 40% replacement rate of carbon steel slag powder and a fixed water-cement ratio of 0.33, although the two commercially available dispersants can improve the initial slump and spread of concrete to a certain extent, their slump retention performance is generally poor. The slump loss within 30 minutes is still around 35-40 mm, and the mixture exhibits varying degrees of bleeding and local segregation, making it difficult to fundamentally eliminate the problem of "bleeding, segregation, and poor cohesion" in the high-volume carbon steel slag powder system. In contrast, the dispersants P-1 to P-5 in the embodiments of this invention can stably control the initial slump at 230-245 mm and the spread at 610-620 mm under the same water conditions, with overall fluidity superior to the control group. More importantly, the slump loss within 30 minutes is generally 20-22 mm less, demonstrating a significant slump retention ability and a significantly wider fluidity window for the mixture.

[0025] Based on the appearance and air content of the mixtures, the mixtures in the example group showed good apparent cohesiveness, with the slurry fully coating the aggregates. No obvious bleeding channels or aggregate settling were observed, and the air content remained stable in the range of 2.3% to 2.7%, with fine and uniformly distributed bubbles. In contrast, the control group had slightly lower air content but exhibited fine bleeding and local stratification. This indicates that ordinary dispersants are difficult to simultaneously achieve both dispersibility and anti-segregation properties in systems with high-dosage carbon-fixed steel slag powder. The dispersant of this invention, through the synergistic effect of the steel slag affinity segment, cement dispersion segment, and rheology / hydrophobicity control segment in the R1–S–C–R2 multi-block structure, effectively weakens the "sacrificial adsorption" on the surface of carbon-fixed steel slag powder, increasing the effective dispersant dosage. Furthermore, by appropriately controlling the air content and yield stress of the system, it significantly improves the cohesiveness and anti-bleeding properties of the mixture.

[0026] In terms of mechanics and durability, under the same water-cement ratio and cementitious material dosage, the 28-day compressive strength of the embodiments of the present invention was higher than that of the control group of commercially available polycarboxylate superplasticizers. Simultaneously, the impermeability was significantly higher than that of the control group. This indicates that the dispersant of the present invention significantly improves workability and anti-segregation performance while also enhancing the density and durability of concrete with high-dosage solid carbon steel slag powder. In summary, compared with existing commercially available similar products, the dispersant of the present invention exhibits superior comprehensive performance in high-dosage solid carbon steel slag powder cementitious systems, effectively expanding the usable dosage and engineering application range of solid carbon steel slag powder.

[0027] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A dispersant for high-volume carbon-fixing steel slag powder cementitious materials, characterized in that, The dispersant is a multi-block comb polymer, and the main chain of the multi-block comb polymer includes, from one end to the other along the chain direction, a first rheology-regulating block R1, a steel slag affinity block S, a cement dispersing block C, and a second rheology-regulating block R2. The dispersant satisfies the following conditions: (1) The first rheology control block R1 and the second rheology control block R2 can be random copolymers containing sulfonic acid monomer D, zwitterionic monomer E and hydrophobic control monomer F, respectively. The molar fractions of sulfonic acid monomer D, zwitterionic monomer E and hydrophobic control monomer F in the first rheology control block R1 and the second rheology control block R2 are denoted as d, e and f, respectively. (2) The steel slag affinity block S is a random copolymer of phosphorus-containing strong complexing monomer G and short-side chain polyether macromonomer B1, and the molar fractions of phosphorus-containing strong complexing monomer G and short-side chain polyether macromonomer B1 are g and b1, respectively. (3) The cement dispersion block C is a random copolymer of long side-chain polyether macromonomer B2, unsaturated carboxylic acid monomer H and alkoxysilane monomer I, and the molar fractions of the long side-chain polyether macromonomer B2, unsaturated carboxylic acid monomer H and alkoxysilane monomer I are b2, h and i, respectively; (4) d: e: f: g: b1: b2: h: i= (12~20): (4~8): 2: (2~6): (1~4): (1~2): (2~5): (1~2).

2. A method for preparing a dispersant for a high-volume carbon-fixing steel slag powder cementitious material as described in claim 1, characterized in that, Includes the following steps: (1) Preparation of the first rheology-controlled block R1: 5 mol of deionized water and 0.001 mol of RAFT reagent were added to the reactor. Then, 0.06-0.10 mol of sulfonic acid monomer D, 0.02-0.04 mol of zwitterionic monomer E and 0.01 mol of hydrophobic control monomer F were added. Water-soluble initiator was added at 50-80℃ under the protection of inert gas N2 to carry out free radical polymerization in aqueous solution to obtain R1 block macromolecular chain with chain transfer structure at the end group. (2) Construction of steel slag affinity block S: In the R1 block macromolecular chain obtained in step (1), 0.02~0.06 mol of phosphorus-containing strong complexing monomer G and 0.01~0.04 mol of short side chain polyether macromonomer B1 are continuously added. At 50~80℃, 0.001~0.005 mol of water-soluble initiator is added and polymerization is continued for 0.5~3h to obtain R1–S block polymer with chain transfer structure at the end group; (3) Constructing cement-dispersed block C: In the R1–S block polymer obtained in step (2), add 0.01~0.02 mol of long side-chain polyether macromonomer B2, 0.02~0.05 mol of unsaturated carboxylic acid monomer H and 0.01~0.02 mol of alkoxysilane monomer I, and add 0.001~0.005 mol of water-soluble initiator at 55~85℃ for 1~4h to obtain R1–S–C block polymer with chain transfer structure at the end group; (4) Constructing the second rheologically controlled block R2: In the R1–S–C block polymer obtained in step (3), add 0.06~0.10 mol of sulfonic acid monomer D, 0.02~0.04 mol of zwitterionic monomer E and 0.01 mol of hydrophobic control monomer F, and add 0.001~0.005 mol of water-soluble initiator at 55~85℃ for 0.5~3h to obtain R1–S–C–R2 multiblock comb polymer; (5) Post-treatment: After the reaction is completed, continue to keep warm for 0.5~3h to reduce the residual monomer content, then cool to room temperature, adjust the pH to 4~7 with sodium hydroxide, freeze dry to obtain a light yellow solid, which is the dispersant for high-volume solid carbon steel slag powder cementitious materials.

3. The method for preparing a dispersant for a high-volume solid carbon steel slag powder cementitious material according to claim 2, characterized in that, The water-soluble initiator is one or a combination of ammonium persulfate, sodium persulfate, potassium persulfate, persulfate-sulfite complex initiation system, and azobisisobutyramidine hydrochloride.

4. The method for preparing a dispersant for a high-volume solid carbon steel slag powder cementitious material according to claim 2, characterized in that, The controllable chain transfer agent RAFT reagent is one or more combinations of dithiobenzoate, trithiocarbonate, trithiocarbonate, and dithiocarbamate.

5. The method for preparing a dispersant for a high-volume solid carbon steel slag powder cementitious material according to claim 2, characterized in that, The sulfonic acid monomer D is one or more combinations of 2-acrylamide-2-methylpropanesulfonic acid, 3-acrylamide-3-methylbutanesulfonic acid, 2-acryloyloxyethanesulfonic acid, 2-methacryloyloxyethanesulfonic acid, 2-sulfoethylmethacrylic acid, 3-sulfopropylmethacrylic acid, ethylene sulfonic acid, styrene sulfonic acid, and their salts.

6. The method for preparing a dispersant for a high-volume carbon-fixing steel slag powder cementitious material according to claim 2, characterized in that, The zwitterionic monomer E is one or more combinations of 2-methacryloyloxyethyl phosphoric acid choline, 2-acryloyloxyethyl phosphoric acid choline, carboxybetaine methacrylate, carboxybetaine acrylate, sulfobetaine methacrylate, and 3-(N,N-dimethyl(methacrylamidopropyl)ammonium)propanesulfonic betaine.

7. The method for preparing a dispersant for a high-volume solid carbon steel slag powder cementitious material according to claim 2, characterized in that, The hydrophobic regulating monomer F is one or more combinations of lauryl methacrylate, stearyl methacrylate, 2-ethylhexyl acrylate, n-hexyl acrylate, dodecyl acrylate, styrene, p-methylstyrene, and isobornyl methacrylate.

8. The method for preparing a dispersant for a high-volume solid carbon steel slag powder cementitious material according to claim 2, characterized in that, The phosphorus-containing strong complexing monomer G is one or more combinations of methacryloyloxyethide diphosphonic acid, acryloyloxyethide diphosphonic acid, methacryloylamino diphosphonic acid, glutamic acid diphosphonate methacrylate, 4-(bis(diethoxyphosphoryl)methyl)phenyl methacrylate, 2-hydroxyethyl methacrylate diphosphate, and allyl diphosphate.

9. The method for preparing a dispersant for a high-volume carbon-fixing steel slag powder cementitious material according to claim 2, characterized in that, The short-chain polyether macromonomer B1 is one of polyether (meth)acrylate or vinyl ether with a number average molecular weight of 200-800 and a polyoxyethylene repeating unit number of 5-20; the long-chain polyether macromonomer B2 is one of polyether (meth)acrylate or vinyl ether with a number average molecular weight of 800-3000 and a polyoxyethylene repeating unit number of 20-70.

10. The method for preparing a dispersant for a high-volume solid carbon steel slag powder cementitious material according to claim 2, characterized in that, The unsaturated carboxylic acid monomer H is one or more of acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, and their water-soluble salts; the alkoxysilane monomer I is one or more of 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-acryloyloxypropyltriethoxysilane, methacryloyloxymethyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(2-methoxyethoxy)silane, and allyltrimethoxysilane.

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