Carbide slag-based low-carbon gel material and preparation method thereof

Abstract

The invention provides a carbide slag-based low-carbon gel material and a preparation method thereof, and belongs to the technical field of building materials. According to the invention, sodium lignin sulfonate is chemically modified through sulfonation and polyethylene glycol chain segment grafting, and the modified lignin is used as a molecular template to form an organic-inorganic nanocomposite with integrated structure and function; when the regulating agent is applied to a carbide slag system, the modified lignin skeleton can efficiently disperse particles and chelate calcium ions, so that long-acting fluidity and controllable coagulation time of slurry are synergistically realized; along with the proceeding of the hydration reaction, the anchored C-S-H nano-particles serve as heterogeneous crystal nucleuses to guide generation of a compact and uniform gel network; finally, the whole hybrid molecule is integrated into a hardened matrix, the rigid C-S-H nanoparticles play a role in filling and reinforcing, and the flexible lignin skeleton plays a role in bridging and toughening, so that the comprehensive performance of the final material is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building materials, and relates to a calcium carbide slag-based low-carbon gel material and a preparation method thereof. BACKGROUND

[0002] At present, the preparation of low-carbon gel materials from industrial solid waste has become a research hotspot in the field of building materials. Calcium carbide slag, as the main by-product of the acetylene chemical industry, is mainly composed of calcium hydroxide and has the characteristics of high calcium and high alkali, and is a potential high-quality raw material for replacing cement and activating mineral activity. However, calcium carbide slag has some deficiencies in high-dosage applications, which limits the scale and value of its resource utilization.

[0003] The existing technology mainly faces two core problems when using high-dosage calcium carbide slag. First, the problem of out-of-control reaction kinetics: the high alkalinity and high concentration of calcium ions provided by calcium carbide slag can excessively activate the dissolution of siliceous and aluminous materials such as mineral powder and fly ash, leading to uncontrollable flash setting of the slurry, which loses its fluidity and operability. Second, the problem of inferiority of the microstructure of the hardened body: even if the setting time is controlled by adding conventional retarders, the out-of-control reaction process will still lead to the formation of a loose network structure with high porosity and many defects, in which the C-S-H gel is coarse and unevenly distributed. This inferior microstructure directly leads to a series of performance defects such as extremely low early strength, weak late strength growth, large volume shrinkage, and easy cracking. SUMMARY

[0004] To solve the above problems, the application provides a calcium carbide slag-based low-carbon gel material and a preparation method thereof. The application chemically modifies sodium lignosulfonate by sulfonation and polyethylene glycol chain grafting, and uses the synergistic effect of electrostatic repulsion and steric hindrance to give it excellent dispersion stability in a high-calcium and high-alkali environment. Subsequently, using the modified lignin as a molecular template, the functional groups of the modified lignin are used to enrich calcium ions and silicate species, and guide the in-situ generation and anchoring of hydrated calcium silicate on the skeleton, forming an organic-inorganic nanocomposite with integrated structure and function. When the regulator is applied to the calcium carbide slag system, the modified lignin skeleton can efficiently disperse particles and chelate calcium ions, and cooperatively achieve long-term fluidity and controllable setting time of the slurry. With the progress of the hydration reaction, the anchored C-S-H nanoparticles act as heterogeneous nuclei and guide the formation of a dense and uniform gel network. Finally, the entire hybrid molecule is integrated into the hardened matrix, the rigid C-S-H nanoparticles play a filling and reinforcing role, and the flexible lignin skeleton plays a bridging and toughening effect, thereby improving the overall performance of the final material.

[0005] To achieve this purpose, the application adopts the following technical solutions:

[0006] In a first aspect, the present application provides a preparation method of carbide slag-based low-carbon gel material, which comprises:

[0007] S1: a sodium lignosulfonate solution is prepared, and after adjusting the pH value thereof, the solution is heated, sodium sulfite and formaldehyde solution are added to obtain a reaction liquid A, and a modified lignin solution is obtained by reaction; under nitrogen protection, sodium hydroxide is added to obtain a reaction liquid B, and after adding epichlorohydrin, a reaction liquid C is obtained by reaction, and polyethylene glycol is added for continuous reaction, and the reaction liquid is cooled and adjusted to neutral pH to obtain a grafted modified lignin solution; a sodium silicate solution is added to obtain a mixed solution, and the mixed solution is stirred to obtain a reaction liquid D;

[0008] S2: a calcium nitrate solution is added dropwise to the reaction liquid D at room temperature to obtain a reaction liquid E, and a suspension is obtained by stirring and aging, and the suspension is centrifuged, washed and dried to obtain a lignin-CSH regulator;

[0009] S3: the carbide slag, the mineral powder, the fly ash and the lignin-CSH regulator are placed in a mixer for dry mixing to obtain a composite dry powder; water is added for wet stirring to obtain a slurry, and the slurry is injected into a mold, and after exhaust, standard curing and demolding, a carbide slag-based low-carbon gel material is obtained.

[0010] As a preferred technical solution of the present application, in step S1, the mass fraction of the sodium lignosulfonate solution is 10-20 wt.%, for example, it can be 10 wt.%, 11 wt.%, 12 wt.%, 13 wt.%, 14 wt.%, 15 wt.%, 16 wt.%, 17 wt.%, 18 wt.%, 19 wt.% or 20 wt.%, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0011] In some optional embodiments, the pH value of the sodium lignosulfonate solution is adjusted to 11-13, for example, it can be adjusted to 11.0, 11.2, 11.4, 11.6, 11.8, 12.0, 12.2, 12.4, 12.6, 12.8 or 13.0, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0012] In some optional embodiments, the sodium lignosulfonate solution is heated to 70-90℃ after adjusting the pH value, for example, it can be heated to 70℃, 72℃, 74℃, 76℃, 78℃, 80℃, 82℃, 84℃, 86℃, 88℃ or 90℃, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0013] In some optional embodiments, the amount of sodium sulfite fed is 10-30% of the mass of lignin sulfonic acid, for example, it can be 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28% or 30%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0014] In some optional embodiments, the amount of formaldehyde solution added is 5-15% of the mass of lignin sulfonic acid, for example, it can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0015] In some optional embodiments, the concentration of the formaldehyde solution is 35-40 wt.%, for example, it can be 35.0 wt.%, 35.5 wt.%, 36.0 wt.%, 36.5 wt.%, 37.0 wt.%, 37.5 wt.%, 38.0 wt.%, 38.5 wt.%, 39.0 wt.%, 39.5 wt.% or 40.0 wt.%, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0016] In some optional embodiments, the reaction solution A is reacted for 2-4 hours to obtain a modified lignin solution, for example, for 2.0 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3.0 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours, or 4.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0017] In some optional embodiments, the modified lignin solution is added with sodium hydroxide at 50-60°C to obtain reaction solution B. For example, it can be added at 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C or 60°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0018] In some optional embodiments, the molar ratio of sodium hydroxide to sodium lignosulfonate is (1.5-2.5):1, for example, it can be 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1 or 2.5:1, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0019] In some optional embodiments, reaction solution B is reacted with epichlorohydrin for 1-2 hours to obtain reaction solution C. For example, the reaction time can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, or 2.0h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0020] In some optional embodiments, the molar ratio of epichlorohydrin to sodium lignosulfonate is (1-1.5):1, for example, it can be 1.00:1, 1.05:1, 1.10:1, 1.15:1, 1.20:1, 1.25:1, 1.30:1, 1.35:1, 1.40:1, 1.45:1 or 1.50:1, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0021] In some optional embodiments, the reaction solution C is added to polyethylene glycol and the reaction continues for 3-5 hours, for example, for 3.0 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours, 4.0 hours, 4.2 hours, 4.4 hours, 4.6 hours, 4.8 hours, or 5.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0022] In some optional embodiments, the molar ratio of polyethylene glycol to epichlorohydrin is (1.2-1.8):1, for example, it can be 1.20:1, 1.26:1, 1.32:1, 1.38:1, 1.44:1, 1.50:1, 1.56:1, 1.62:1, 1.68:1, 1.74:1 or 1.80:1, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0023] In some optional embodiments, the ratio of lignin solids content in the mixed solution to silica solids content in the sodium silicate solution is 1:(1-2), for example, it can be 1:1.0, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2.0, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0024] In some optional embodiments, the concentration of the sodium silicate solution is 35-45 wt.%, for example, it can be 35 wt.%, 36 wt.%, 37 wt.%, 38 wt.%, 39 wt.%, 40 wt.%, 41 wt.%, 42 wt.%, 43 wt.%, 44 wt.%, or 45 wt.%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0025] In some optional embodiments, the mixing time of the mixed solution is 0.5-1 h, for example, it can be 0.50 h, 0.55 h, 0.60 h, 0.65 h, 0.70 h, 0.75 h, 0.80 h, 0.85 h, 0.90 h, 0.95 h or 1.00 h, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0026] As a preferred embodiment of the present invention, in step S2, the molar ratio of calcium to silicon in the reaction solution E is (0.8-1.2):1, for example, it can be 0.80:1, 0.84:1, 0.88:1, 0.92:1, 0.96:1, 1.00:1, 1.04:1, 1.08:1, 1.12:1, 1.16:1 or 1.20:1, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] In some optional embodiments, the reaction solution E is stirred and aged for 1-3 hours, for example, 1.0h, 1.2h, 1.4h, 1.6h, 1.8h, 2.0h, 2.2h, 2.4h, 2.6h, 2.8h or 3.0h, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0028] As a preferred embodiment of the present invention, in step S3, the specific surface area of ​​the carbide slag is 400-500 m². 2 / kg, for example, could be 400m 2 / kg, 410m 2 / kg, 420m 2 / kg, 430m 2 / kg, 440m 2 / kg, 450m 2 / kg, 460m 2 / kg, 470m 2 / kg, 480m 2 / kg, 490m 2 / kg or 500m 2 / kg, but not limited to the listed values; other unlisted values ​​within this range also apply.

[0029] In some optional embodiments, the specific surface area of ​​the mineral powder is 400-550 m². 2 / kg, for example, could be 400m 2 / kg, 415m 2 / kg, 430m 2 / kg, 445m2 / kg, 460m 2 / kg, 475m 2 / kg, 490m 2 / kg, 505m 2 / kg, 520m 2 / kg, 535m 2 / kg or 550m 2 / kg, but not limited to the listed values; other unlisted values ​​within this range also apply.

[0030] In some optional embodiments, the specific surface area of ​​the fly ash is 350-500 m². 2 / kg, for example, could be 350m 2 / kg, 365m 2 / kg, 380m 2 / kg, 395m 2 / kg, 410m 2 / kg, 425m 2 / kg, 440m 2 / kg, 455m 2 / kg, 470m 2 / kg, 485m 2 / kg or 500m 2 / kg, but not limited to the listed values; other unlisted values ​​within this range also apply.

[0031] In some optional embodiments, the mass ratio of carbide slag, mineral powder, and fly ash is (60-70):(25-35):(5-15), for example, it can be (60, 61, 62, 63, 64, 65, 66, 67, 68, 69 or 70):(25, 26, 27, 28, 29, 30, 31, 32, 33, 34 or 35):(5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15), but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0032] In some optional embodiments, the amount of lignin-CSH regulator fed is 1.2-1.6% of the total mass of carbide slag, mineral powder and fly ash, for example, it can be 1.20%, 1.24%, 1.28%, 1.32%, 1.36%, 1.40%, 1.44%, 1.48%, 1.52%, 1.56% or 1.60%, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0033] In some optional embodiments, the mass ratio of water to the total mass of carbide slag, mineral powder and fly ash is (0.3-0.35):1, for example, it can be 0.300:1, 0.305:1, 0.310:1, 0.315:1, 0.320:1, 0.325:1, 0.330:1, 0.335:1, 0.340:1, 0.345:1 or 0.350:1, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0034] Secondly, the present invention provides a carbide slag-based low-carbon gel material.

[0035] This application describes the preparation of a lignin-CSH nano-hybrid material to regulate the reaction process and microstructure of a high-dosage carbide slag-based cementitious system.

[0036] In the preparation process of the regulator (S1-S2), this application first chemically modifies sodium lignin sulfonate. The sulfonation treatment in step S1 aims to increase the density of sulfonic acid groups on its backbone, thereby enhancing the negative charge and hydrophilicity of the macromolecule. Subsequent grafting of hydrophilic polyethylene glycol segments introduces flexible polyethylene glycol long chains onto the lignin backbone through an etherification reaction. These two modification steps together endow lignin molecules with dispersion stability in subsequent high-ion-concentration aqueous solutions. The enhanced electrostatic repulsion and the introduced steric hindrance synergistically suppress the dispersion of molecular chains in high-valent cations (such as Ca²⁺). 2+ The S2 step utilizes a modified lignin molecular network as a template, where CSH undergoes curling and aggregation in the presence of lignin. Its abundant polar functional groups possess the ability to complex and locally enrich calcium ions and silicates, thus confining CSH nucleation and growth within the micro-environment of lignin molecules. This in-situ co-precipitation process facilitates the formation of uniformly sized nanoscale CSH particles, anchoring them to the lignin framework through chemical bonding or strong physical adsorption, ultimately forming a composite structure where an organic framework supports inorganic nanoparticles.

[0037] When this regulator is applied to a carbide slag-based cementitious system (S3-S4), its multifunctionality becomes apparent. In the initial stage of slurry mixing, the modified lignin molecular framework, due to its size, high negative charge, and the steric hindrance effect of the polyethylene glycol side chains, rapidly adsorbs onto the surface of carbide slag, mineral powder, and other particles, forming an adsorption layer. This physically hinders flocculation between particles, thus imparting good fluidity to the slurry. Simultaneously, the sulfonic acid and carboxyl functional groups on the framework can react with the large amount of free Ca produced by the dissolution of carbide slag. 2+ The formation of a temporary complex effectively reduces the Ca concentration in the liquid phase. 2+ The initial activity of the CSH gel slowed down the rapid dissolution of aluminosilicate minerals and the subsequent precipitation rate of CSH gel, thereby regulating the setting time of the system.

[0038] As the hydration reaction proceeds, the regulator's role shifts from liquid-phase control to the construction of solid-phase microstructures. Since the regulator is pre-distributed uniformly on the surface of the reactant particles, the CSH nanoparticles mounted on them become ideal heterogeneous nucleation sites for newly generated hydration products. This provides the system with a large number of dispersed, low-energy-barrier nucleation substrates, guiding the formation of hydration products in a finer, more diffuse manner, rather than forming large crystalline aggregates. This contributes to the formation of a denser and more uniform gel network microstructure. In the later stages of hardening, the entire organic-inorganic hybrid molecule is integrated into the inorganic gel matrix. The rigid CSH nanoparticles act as nanofillers, filling the tiny pores between gels and increasing the matrix density. Meanwhile, the flexible lignin molecular framework runs through the different gel clusters, acting as a microscopic bridge, dissipating some energy under stress and inhibiting the propagation of microcracks.

[0039] This application achieves full-process control of calcium carbide slag-based gel materials, from macroscopic working performance to microstructure formation, by introducing lignin-CSH regulator, thereby systematically improving the overall performance of the materials.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] This application introduces a lignin-CSH regulator, which can effectively synergistically regulate the fluidity and setting time of the slurry. The unique molecular structure of this regulator also endows the slurry with excellent dispersibility and controllable retarding effect, ensuring that the slurry can maintain good working performance for a long time in a highly alkaline environment with high dosage of carbide slag, thus meeting the requirements of actual construction operations.

[0042] In the regulator introduced in this application, the in-situ grown CSH nanoparticles can act as heterogeneous nuclei in the early stages of hydration, guiding the hydration products to form a finer and denser gel network. This systematic optimization of the microstructure at the nanoscale improves the density of the hardened body, thereby effectively enhancing both the early and long-term strength of the material.

[0043] In this application, the hardened gel material forms a uniform and dense microstructure, and the introduction of the organic framework in the regulator plays a bridging and toughening role at the nanoscale. This reduces shrinkage channels caused by moisture migration and inhibits the propagation of microcracks, resulting in a lower drying shrinkage rate and good crack resistance, thus improving its long-term volume stability and durability. Detailed Implementation

[0044] The technical solution of the present invention will be described in detail below with reference to specific embodiments. The embodiments described herein are specific implementations of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be construed as limiting the implementation of the present invention or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of this application. These technical solutions include technical solutions that employ any obvious substitutions and modifications made to the embodiments described herein.

[0045] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone further purification or processing.

[0046] Example 1

[0047] This embodiment provides a calcium carbide slag-based low-carbon gel material and its preparation method. The preparation method of the calcium carbide slag-based low-carbon gel material specifically includes the following steps:

[0048] S1: Prepare a sodium lignosulfonate solution with a mass fraction of 18 wt.%, adjust its pH to 12, heat to 85℃, add sodium sulfite (25% of the mass of lignosulfonate) and formaldehyde solution (12% of the mass of lignosulfonate) to obtain reaction solution A, where the concentration of formaldehyde solution is 38 wt.%, react for 3.5 h to obtain modified lignin solution; under nitrogen protection, at 58℃, add sodium hydroxide to obtain reaction solution B, where the molar ratio of sodium hydroxide to sodium lignosulfonate is 2.2:1, add... After reacting with epichlorohydrin for 1.8 h, reaction solution C was obtained, in which the molar ratio of epichlorohydrin to sodium lignosulfonate was 1.4:1. Polyethylene glycol was added and the reaction continued for 4.5 h, in which the molar ratio of polyethylene glycol to epichlorohydrin was 1.6:1. After cooling and adjusting the pH to neutral, a grafted lignin-modified lignin solution was obtained. Sodium silicate solution was added to obtain a mixed solution, in which the ratio of lignin solid content to silica solid content in the mixed solution was 1:1.8, and the concentration of sodium silicate solution was 42 wt.%. After stirring and mixing for 0.8 h, reaction solution D was obtained.

[0049] S2: Calcium nitrate solution was added dropwise to reaction solution D at room temperature to obtain reaction solution E, wherein the molar ratio of calcium to silicon was 1.0:1. After stirring and aging for 2.5 h, a suspension was obtained. The suspension was then centrifuged, washed, and dried to obtain lignin-CSH regulator.

[0050] S3: A specific surface area of ​​480m² 2 / kg of carbide slag, with a specific surface area of ​​500m² 2 / kg of mineral powder, with a specific surface area of ​​450m² 2 / kg of fly ash and lignin-CSH regulator are placed in a mixer for dry mixing to obtain composite dry powder; the mass ratio of carbide slag, mineral powder and fly ash is 65:30:10, and the amount of lignin-CSH regulator is 1.5% of the total mass of carbide slag, mineral powder and fly ash; water is added for wet mixing to obtain slurry, wherein the mass ratio of water to the total mass of carbide slag, mineral powder and fly ash is 0.33:1, which is poured into a mold, degassed, and cured according to standard before demolding to obtain carbide slag-based low-carbon gel material.

[0051] Example 2

[0052] This embodiment provides a calcium carbide slag-based low-carbon gel material and its preparation method. The preparation method of the calcium carbide slag-based low-carbon gel material specifically includes the following steps:

[0053] S1: Prepare a 10 wt.% sodium lignosulfonate solution, adjust its pH to 13, heat to 70℃, add 10% sodium sulfite (by mass of lignosulfonate) and 5% formaldehyde (by mass of lignosulfonate) to obtain reaction solution A, where the formaldehyde concentration is 35 wt.%. React for 2 hours to obtain a modified lignin solution. Under nitrogen protection, add sodium hydroxide at 50℃ to obtain reaction solution B, where the molar ratio of sodium hydroxide to sodium lignosulfonate is 1.5:1. After adding epichlorohydrin, the reaction proceeds for 1 hour to obtain reaction solution C, in which the molar ratio of epichlorohydrin to sodium lignosulfonate is 1:1. Polyethylene glycol is then added, and the reaction continues for 3 hours, in which the molar ratio of polyethylene glycol to epichlorohydrin is 1.2:1. The mixture is cooled and the pH is adjusted to neutral to obtain a grafted lignin solution. Sodium silicate solution is then added to obtain a mixed solution, in which the ratio of lignin solids to silica solids is 1:1, and the concentration of the sodium silicate solution is 35 wt.%. The mixture is stirred for 0.5 hours to obtain reaction solution D.

[0054] S2: Calcium nitrate solution was added dropwise to reaction solution D at room temperature to obtain reaction solution E, in which the molar ratio of calcium to silicon was 1.2:1. After stirring and aging for 1 hour, a suspension was obtained. The suspension was then centrifuged, washed, and dried to obtain lignin-CSH regulator.

[0055] S3: A surface area of ​​400 m² 2 / kg of carbide slag, with a specific surface area of ​​400m² 2 / kg of mineral powder, with a specific surface area of ​​350m² 2 / kg of fly ash and lignin-CSH regulator are placed in a mixer for dry mixing to obtain composite dry powder; the mass ratio of carbide slag, mineral powder and fly ash is 70:25:15, and the amount of lignin-CSH regulator is 1.2% of the total mass of carbide slag, mineral powder and fly ash; water is added for wet mixing to obtain slurry, wherein the mass ratio of water to the total mass of carbide slag, mineral powder and fly ash is 0.3:1, which is poured into a mold, degassed, and cured according to standard before demolding to obtain carbide slag-based low-carbon gel material.

[0056] Example 3

[0057] This embodiment provides a calcium carbide slag-based low-carbon gel material and its preparation method. The preparation method of the calcium carbide slag-based low-carbon gel material specifically includes the following steps:

[0058] S1: Prepare a 15 wt.% sodium lignin sulfonate solution, adjust its pH to 11.5, heat to 80℃, add 20% sodium sulfite (by mass of lignin sulfonate) and 8% formaldehyde (by mass of lignin sulfonate) to obtain reaction solution A, where the formaldehyde concentration is 37 wt.%. React for 3 hours to obtain a modified lignin solution; under nitrogen protection, at 55℃, add sodium hydroxide to obtain reaction solution B, where the molar ratio of sodium hydroxide to sodium lignin sulfonate is 1.8:1. After reacting with epichlorohydrin for 1.2 h, reaction solution C was obtained, in which the molar ratio of epichlorohydrin to sodium lignosulfonate was 1.1:1. Polyethylene glycol was added and the reaction continued for 3.5 h, in which the molar ratio of polyethylene glycol to epichlorohydrin was 1.4:1. After cooling and adjusting the pH to neutral, a grafted lignin-modified lignin solution was obtained. Sodium silicate solution was added to obtain a mixed solution, in which the ratio of lignin solid content to silica solid content in the mixed solution was 1:1.5, and the concentration of sodium silicate solution was 40 wt.%. After stirring and mixing for 0.7 h, reaction solution D was obtained.

[0059] S2: Calcium nitrate solution was added dropwise to reaction solution D at room temperature to obtain reaction solution E, wherein the molar ratio of calcium to silicon was 1.1:1. After stirring and aging for 2 hours, a suspension was obtained. The suspension was then centrifuged, washed, and dried to obtain lignin-CSH regulator.

[0060] S3: A surface area of ​​450m² 2 / kg of carbide slag, with a specific surface area of ​​450m² 2 / kg of mineral powder, with a specific surface area of ​​400m² 2 / kg of fly ash and lignin-CSH regulator are placed in a mixer for dry mixing to obtain composite dry powder; the mass ratio of carbide slag, mineral powder and fly ash is 68:28:12, and the amount of lignin-CSH regulator is 1.4% of the total mass of carbide slag, mineral powder and fly ash; water is added for wet mixing to obtain slurry, the mass ratio of water to the total mass of carbide slag, mineral powder and fly ash is 0.32:1, the slurry is poured into a mold, degassed, and cured according to standard before demolding to obtain carbide slag-based low-carbon gel material.

[0061] Example 4

[0062] This embodiment provides a calcium carbide slag-based low-carbon gel material and its preparation method. The preparation method of the calcium carbide slag-based low-carbon gel material specifically includes the following steps:

[0063] S1: Prepare a 20 wt.% sodium lignosulfonate solution, adjust its pH to 11, heat to 90℃, add 30% sodium sulfite (by mass of lignosulfonate) and 15% formaldehyde (by mass of lignosulfonate) to obtain reaction solution A, where the formaldehyde concentration is 40 wt.%. React for 4 hours to obtain a modified lignin solution. Under nitrogen protection, add sodium hydroxide at 60℃ to obtain reaction solution B, where the molar ratio of sodium hydroxide to sodium lignosulfonate is 2.5:1. After adding epichlorohydrin, the reaction proceeds for 2 hours to obtain reaction solution C, in which the molar ratio of epichlorohydrin to sodium lignosulfonate is 1.5:1. Polyethylene glycol is then added and the reaction continues for 5 hours, in which the molar ratio of polyethylene glycol to epichlorohydrin is 1.8:1. The mixture is cooled and the pH is adjusted to neutral to obtain a grafted modified lignin solution. Sodium silicate solution is added to obtain a mixed solution, in which the ratio of lignin solid content to silica solid content in the mixed solution is 1:2, and the concentration of sodium silicate solution is 45 wt.%. The mixture is stirred and mixed for 1 hour to obtain reaction solution D.

[0064] S2: Calcium nitrate solution was added dropwise to reaction solution D at room temperature to obtain reaction solution E, wherein the molar ratio of calcium to silicon was 0.8:1. The mixture was stirred and aged for 3 hours to obtain a suspension, which was then centrifuged, washed, and dried to obtain lignin-CSH regulator.

[0065] S3: A surface area of ​​500m² 2 / kg of carbide slag, with a specific surface area of ​​550m² 2 / kg of mineral powder, with a specific surface area of ​​500m² 2 / kg of fly ash and lignin-CSH regulator are placed in a mixer for dry mixing to obtain composite dry powder; the mass ratio of carbide slag, mineral powder and fly ash is 60:35:5, and the amount of lignin-CSH regulator is 1.6% of the total mass of carbide slag, mineral powder and fly ash; water is added for wet mixing to obtain slurry, the mass ratio of water to the total mass of carbide slag, mineral powder and fly ash is 0.35:1, the slurry is poured into a mold, degassed, and cured according to standard before demolding to obtain carbide slag-based low-carbon gel material.

[0066] Comparative Example 1

[0067] This comparative example provides a calcium carbide slag-based low-carbon gel material. The difference between this example and Example 1 is that no lignin-CSH regulator is added, while the other operating steps and process parameters are exactly the same as in Example 1.

[0068] Comparative Example 2

[0069] This comparative example provides a carbide slag-based low-carbon gel material. The difference from Example 1 is that no lignin-CSH regulator is added. The grafted modified lignin solution in S1 is prepared separately and dried into modified lignin powder. CSH nanoparticles are prepared separately and used directly after physical mixing. Other operation steps and process parameters are exactly the same as in Example 1.

[0070] Comparative Example 3

[0071] This comparative example provides a calcium carbide slag-based low-carbon gel material. The difference from Example 1 is that the polyethylene glycol grafting step in S1 is omitted, while the other operation steps and process parameters are exactly the same as in Example 1.

[0072] Comparative Example 4

[0073] This comparative example provides a calcium carbide slag-based low-carbon gel material. The difference from Example 1 is that the grafted modified lignin solution is directly prepared and dried to obtain grafted modified lignin. Other operation steps and process parameters are exactly the same as in Example 1.

[0074] The performance of the carbide slag-based low-carbon gel materials of Examples 1-4 and Comparative Examples 1-4 was tested, and the specific process is as follows:

[0075] The fluidity of mortar is determined according to GB / T 2419-2005;

[0076] The setting time of mortar was tested using a Vicat apparatus: The test mold was removed from the moisture curing chamber and placed under the test needle. Initial setting was achieved when the needle penetrated vertically into the cement paste to a distance of 4mm ± 1mm ​​from the bottom slab. Final setting was achieved when the needle penetrated 0.5mm into the specimen.

[0077] The flexural and compressive strengths of samples cured for 28 days were tested using a DY-208JC fully automatic pressure testing machine. The loading rate for the compressive test was set to 2400 N / s ± 200 N / s, and the loading rate for the flexural test was set to 50 N / s ± 10 N / s.

[0078] The test results are shown in Table 1.

[0079] Table 1. Performance test results of carbide slag-based low-carbon gel materials in Examples 1-4 and Comparative Examples 1-4

[0080]

[0081] The test results from Example 1 and Comparative Example 1 show that without the addition of lignin-CSH regulator, the slurry flash-sets, its fluidity cannot be measured, its setting time is extremely short, and the strength of the hardened body is extremely low. This is because the high content of carbide slag provides excessively high initial alkalinity and calcium ion concentration, which greatly accelerates the dissolution of silica-alumina components in mineral powder and fly ash and the subsequent precipitation reaction of C-(A)-SH gel, leading to uncontrolled reaction kinetics. The slurry cannot form a uniform flow state and quickly loses its workability. The hardened body that is ultimately formed has serious macroscopic defects due to the loose particle packing and the inclusion of a large number of air bubbles, and cannot form an effective load-bearing structure. Therefore, its flexural and compressive strengths are both at extremely low levels.

[0082] The test results from Example 1 and Comparative Example 2 show that without the addition of the lignin-CSH regulator, preparing the grafted modified lignin solution in S1 separately, drying it into modified lignin powder, and preparing CSH nanoparticles separately, followed by physical mixing of the two according to the solid content ratio in Example 1, resulted in a decrease in fluidity, setting time control, and final mechanical properties. This is because the physically mixed components cannot form the synergistic structure unique to in-situ synthesis. Lacking the intrinsic molecular anchoring, CSH nanoparticles agglomerate in the strong electrolyte slurry, significantly reducing their effective specific surface area and dispersibility as heterogeneous nuclei, thus decreasing heterogeneous nucleation efficiency and consequently reducing flexural and compressive strength. Simultaneously, the agglomeration of nanoparticles increases the viscosity of the slurry, leading to poorer fluidity; the regulatory effect of modified lignin on calcium ions is also weakened by the interference of nanoparticles, affecting the setting time.

[0083] The test results from Example 1 and Comparative Example 3 show that omitting the polyethylene glycol grafting step in S1 and directly growing CSH nanoparticles in situ in the modified lignin solution, thus omitting the grafting step of the hydrophilic segments of polyethylene glycol, leads to a decrease in slurry fluidity and ultimately a decline in mechanical properties. This is because lignin modified only by sulfonation mainly relies on electrostatic repulsion to maintain dispersion. In an environment with high calcium ion concentration, a large amount of Ca... 2+This compresses the electric double layer on the particle surface and may partially neutralize the negative charge of the sulfonic acid groups through "calcium bridging," thereby weakening the electrostatic repulsion. The lack of the crucial stabilizing mechanism provided by the long polyethylene glycol chains reduces the dispersibility of the regulator under high ionic strength, leading to poorer slurry flowability. Reduced slurry dispersibility affects the uniform distribution of particles and the hydration environment, thus impacting the strength of the final hardened body.

[0084] The test results from Example 1 and Comparative Example 4 show that directly preparing a graft-modified lignin solution and drying it to obtain graft-modified lignin, without the CSH in-situ growth step, resulted in excellent slurry flowability and a longer setting time, but reduced flexural and compressive strength. This is because the regulator only possesses excellent dispersing and retarding functions, lacking the core role of heterogeneous nucleation. Without the guidance of CSH nanocrystals, the nucleation energy barrier of the hydration products is high, the formation process is slow and disordered, and the final gel network is of poor quality. The increased flowability and prolonged setting time may actually be due to its stronger dispersing and retarding abilities, but this does not translate into effective microstructure and mechanical strength.

[0085] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a calcium carbide slag-based low-carbon gel material, characterized in that, The preparation method includes: S1: Prepare a sodium lignosulfonate solution, adjust its pH value, heat it, add sodium sulfite and formaldehyde solution to obtain reaction solution A, and react to obtain a modified lignin solution; under nitrogen protection, add sodium hydroxide to obtain reaction solution B, add epichlorohydrin and react to obtain reaction solution C, add polyethylene glycol to continue the reaction, cool and adjust the pH to neutral to obtain a grafted modified lignin solution; add sodium silicate solution to obtain a mixed solution, stir and mix to obtain reaction solution D; S2: Calcium nitrate solution was added dropwise to reaction solution D at room temperature to obtain reaction solution E. The solution was stirred and aged to obtain a suspension. The suspension was then centrifuged, washed, and dried to obtain lignin-CSH regulator. S3: Carbide slag, mineral powder, fly ash and lignin-CSH regulator are placed in a mixer for dry mixing to obtain composite dry powder; water is added for wet mixing to obtain slurry, which is then injected into a mold, degassed, cured according to standard, and demolded to obtain carbide slag-based low-carbon gel material.

2. The method for preparing a carbide slag-based low-carbon gel material according to claim 1, characterized in that, In S1: The amount of sodium sulfite added is 10-30% of the mass of lignin sulfonic acid; The amount of formaldehyde solution added is 5-15% of the mass of lignin sulfonic acid.

3. The method for preparing a carbide slag-based low-carbon gel material according to claim 1, characterized in that, In S1: The molar ratio of sodium hydroxide to sodium lignosulfonate is (1.5-2.5):1; The molar ratio of epichlorohydrin to sodium lignosulfonate is (1-1.5):

1.

4. The method for preparing a carbide slag-based low-carbon gel material according to claim 1, characterized in that, In S1: The molar ratio of polyethylene glycol to epichlorohydrin is (1.2-1.8):1; The ratio of lignin solids content in the mixed solution to silica solids content in the sodium silicate solution is 1:(1-2).

5. The method for preparing a carbide slag-based low-carbon gel material according to claim 1, characterized in that, In S2: The molar ratio of calcium to silicon in the reaction solution E is (0.8-1.2):

1.

6. The method for preparing a carbide slag-based low-carbon gel material according to claim 1, characterized in that, In S3: The specific surface area of ​​the carbide slag is 400-500 m² / kg.

7. The method for preparing a carbide slag-based low-carbon gel material according to claim 1, characterized in that, In S3: The specific surface area of ​​the mineral powder is 400-550 m² / kg.

8. The method for preparing a carbide slag-based low-carbon gel material according to claim 1, characterized in that, In S3: The specific surface area of ​​the fly ash is 350-500 m² / kg.

9. The method for preparing a carbide slag-based low-carbon gel material according to claim 1, characterized in that, In S3: The mass ratio of the carbide slag, mineral powder and fly ash is (60-70):(25-35):(5-15); The amount of lignin-CSH regulator added is 1.2-1.6% of the total mass of carbide slag, mineral powder and fly ash; The mass ratio of water to the total mass of carbide slag, mineral powder and fly ash is (0.3-0.35):

1.

10. A carbide slag-based low-carbon gel material prepared by the preparation method according to any one of claims 1-9.

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