A carbide slag-based low-carbon cementitious material and a preparation method thereof

Abstract

The application provides a calcium carbide slag-based low-carbon gel material and a preparation method thereof, and belongs to the technical field of building materials; the sodium lignosulfonate is chemically modified through sulfonation and polyethylene glycol 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 regulator is applied to a calcium carbide slag system, the modified lignin skeleton can efficiently disperse particles and chelate calcium ions, and the long-term fluidity and controllable setting time of the slurry are achieved; with the progress of the hydration reaction, the C-S-H nanoparticles anchored thereon act as heterogeneous crystal nuclei to guide the generation 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, 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 carbide slag-based low-carbon cementitious material and a preparation method thereof. BACKGROUND

[0002] At present, the preparation of low-carbon cementitious materials from industrial solid wastes has become a research hotspot in the field of building materials. 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, 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 carbide slag. First, the problem of out-of-control reaction kinetics: the high alkalinity and high concentration of calcium ions provided by 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 carbide slag-based low-carbon cementitious 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, guiding 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 carbide slag system, the modified lignin skeleton can efficiently disperse particles and chelate calcium ions, and the long-term fluidity of the slurry and the controllable setting time are achieved. 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 cementitious material, which comprises:

[0007] S1: preparing a sodium lignosulfonate solution, adjusting the pH value thereof, and then heating, adding a sodium sulfite and formaldehyde solution to obtain a reaction liquid A, and reacting to obtain a modified lignin solution; under nitrogen protection, adding sodium hydroxide to obtain a reaction liquid B, adding epichlorohydrin after reaction to obtain a reaction liquid C, adding polyethylene glycol for continuous reaction, cooling, and adjusting the pH value to neutral to obtain a grafted modified lignin solution; adding a sodium silicate solution to obtain a mixed solution, and stirring and mixing to obtain a reaction liquid D;

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

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

[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 this 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 this 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 this range are also applicable.

[0013] In some optional embodiments, the amount of sodium sulfite fed is 10-30% of the mass of the lignosulfonic 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 values not listed in the range are also applicable.

[0014] In some optional embodiments, the amount of formaldehyde solution fed is 5-15% of the mass of the lignosulfonic 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 values not listed in the 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, and other values not listed in the range are also applicable.

[0016] In some optional embodiments, the reaction of the reaction liquid A is carried out for 2-4 h to obtain a modified lignin solution, for example, it can be carried out for 2.0 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h, 3.0 h, 3.2 h, 3.4 h, 3.6 h, 3.8 h, or 4.0 h, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0017] In some optional embodiments, the modified lignin solution is added with sodium hydroxide at 50-60°C to obtain a reaction liquid 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, and other values not listed in the 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, and other values not listed in the range are also applicable.

[0019] In some optional embodiments, the reaction liquid B is reacted for 1-2 hours after the addition of epichlorohydrin to obtain a reaction liquid C, for example, the reaction can be carried out for 1.0 hour, 1.1 hour, 1.2 hour, 1.3 hour, 1.4 hour, 1.5 hour, 1.6 hour, 1.7 hour, 1.8 hour, 1.9 hour or 2.0 hour, but not only limited to the listed values, other values not listed in the range of values 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 not only limited to the listed values, other values not listed in the range of values are also applicable.

[0021] In some optional embodiments, the reaction liquid C is reacted for 3-5 hours after the addition of polyethylene glycol to continue the reaction, for example, the reaction can be carried out 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 not only limited to the listed values, other values not listed in the range of values 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 not only limited to the listed values, other values not listed in the range of values are also applicable.

[0023] In some optional embodiments, the ratio of the solid content of lignin in the mixed solution to the solid content of silicon dioxide 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 not only limited to the listed values, other values not listed in the range of values 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 not only limited to the listed values, other values not listed in the range of values are also applicable.

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

[0026] As a preferred technical solution of the present application, in step S2, the molar ratio of calcium element to silicon element 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 not only limited to the listed values, other values not listed in the range are also applicable.

[0027] In some optional embodiments, the reaction solution E is stirred for 1-3h, for example, it can be 1.0h, 1.2h, 1.4h, 1.6h, 1.8h, 2.0h, 2.2h, 2.4h, 2.6h, 2.8h or 3.0h, but not only limited to the listed values, other values not listed in the range are also applicable.

[0028] As a preferred technical solution of the present application, in step S3, the specific surface area of the carbide slag is 400-500m 2 / kg, for example, it can 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 only limited to the listed values, other values not listed in the range are also applicable.

[0029] In some optional embodiments, the specific surface area of the ore powder is 400-550m 2 / kg, for example, it can be 400m 2 / kg, 415m 2 / kg, 430m 2 / kg, 445m2 / kg, 460 m 2 / kg, 475 m 2 / kg, 490 m 2 / kg, 505 m 2 / kg, 520 m 2 / kg, 535 m 2 / kg, or 550 m 2 / kg, but not only the listed values, other values within the range are also applicable.

[0030] In some optional embodiments, the specific surface area of the fly ash is 350-500 m 2 / kg, for example, can be 350 m 2 / kg, 365 m 2 / kg, 380 m 2 / kg, 395 m 2 / kg, 410 m 2 / kg, 425 m 2 / kg, 440 m 2 / kg, 455 m 2 / kg, 470 m 2 / kg, 485 m 2 / kg, or 500 m 2 / kg, but not only the listed values, other values within the range are also applicable.

[0031] In some optional embodiments, the mass ratio of the carbide slag, the mineral powder and the fly ash is (60-70):(25-35):(5-15), for example, 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 not only the listed values, other values within the range are also applicable.

[0032] In some optional embodiments, the feeding amount of the lignin-CSH regulator is 1.2-1.6% of the total mass of the carbide slag, the mineral powder and the fly ash, for example, 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 not only the listed values, other values within the range are also applicable.

[0033] In some optional embodiments, the mass ratio of the water to the total mass of the carbide slag, the mineral powder and the fly ash is (0.3-0.35):1, for example, 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, and other unlisted values within the range are also applicable.

[0034] In a second aspect, the present application provides a carbide slag-based low-carbon cementitious material.

[0035] The present application regulates the reaction process and microstructure of a high-content carbide slag-based cementitious system by preparing a lignin-CSH nanohybrid material.

[0036] In the preparation process of the regulating agent (S1-S2), the present application first chemically modifies sodium lignosulfonate. The sulfonation treatment in S1 aims to increase the density of sulfonic acid groups on the skeleton, thereby increasing the negative charge and hydrophilicity of the macromolecule. Subsequent grafting of the polyethylene glycol hydrophilic segment introduces a flexible polyethylene glycol long chain on the lignin skeleton through etherification. These two modifications together endow the lignin molecule with dispersion stability in subsequent high ionic strength aqueous solutions. The synergistic effect of the strengthened electrostatic repulsion and the introduced steric hindrance effect inhibits the curling and sedimentation of the molecular chain in the presence of high-valence cations (such as Ca 2+ ). On this basis, S2 utilizes the modified lignin molecular network as a template. Its rich polar functional groups have the ability to complex and locally enrich calcium ions and silicate, which limits the nucleation and growth of C-S-H in the microenvironment of the lignin molecule. This in-situ co-precipitation process is conducive to the formation of uniform nanoscale C-S-H particles and their anchoring on the lignin skeleton through chemical bonding or strong physical adsorption, ultimately forming a composite structure of inorganic nanoparticles supported by an organic skeleton.

[0037] When this regulating agent is applied to a carbide slag-based cementitious system (S3-S4), its multifunctionality is manifested. At the initial stage of slurry mixing, the molecular skeleton of modified lignin, with its size, high negative charge and steric hindrance effect of the polyethylene glycol side chain, will quickly adsorb on the surface of particles such as carbide slag and mineral powder, forming an adsorption layer and physically hindering the flocculation between particles, thereby imparting good fluidity to the slurry. At the same time, the functional groups such as sulfonic acid groups and carboxyl groups on the skeleton can form temporary complexes with the large amount of free Ca 2+ produced by the dissolution of carbide slag, effectively reducing the initial activity of Ca 2+ in the liquid phase and delaying the rapid dissolution of silicate and aluminate minerals and the subsequent precipitation rate of C-S-H gel, thereby regulating the setting time of the system.

[0038] As the hydration reaction proceeds, the focus of the regulating agent shifts from liquid phase regulation to the construction of solid phase microstructure. Since the regulating agent has been uniformly distributed on the surface of the reaction particles in advance, the C-S-H nanoparticles carried thereon become ideal heterogeneous nucleation sites for the newly generated hydration products. This provides the system with a large number of dispersed low-energy barrier nucleation substrates, guiding the hydration products to be generated in a more fine and dispersed manner rather than forming coarse crystal aggregates. This helps to form a more dense and uniform gel network microstructure. In the later stage of hardening, the entire organic-inorganic hybrid molecule is integrated into the inorganic cementitious matrix. Among them, the rigid C-S-H nanoparticles act as nano-fillers, filling the small pores between the gels and improving the density of the matrix. The flexible lignin molecular skeleton, on the other hand, acts as a micro-bridge between different gel clusters, can dissipate part of the energy under stress and inhibit the propagation of micro-cracks.

[0039] The present application realizes the regulation of the entire process of the carbide slag-based cementitious material from the macroscopic workability to the microstructure formation by introducing the lignin-CSH regulating agent, and systematically improves the overall performance of the material.

[0040] Compared with the prior art, the present application has the following beneficial effects:

[0041] The present application introduces the lignin-CSH regulating agent, which can effectively cooperate with the fluidity and setting time of the slurry. The unique molecular structure of the regulating agent simultaneously endows the slurry with excellent dispersibility and controllable retarding effect, ensuring that the slurry can still maintain good workability for a long time under the strong alkaline environment of high content of carbide slag, meeting the requirements of actual construction operation;

[0042] In the regulating agent introduced in the present application, the in-situ grown C-S-H nanoparticles can act as heterogeneous crystal nuclei in the early stage of hydration, guiding the hydration products to form a more fine and dense gel network. This systematic optimization of the microstructure at the nanoscale improves the density of the hardened body, thereby effectively enhancing the early strength and long-term strength of the material;

[0043] The present application forms a uniform and dense microstructure inside the hardened body of the cementitious material, and due to the introduction of the organic skeleton in the regulating agent, it plays a bridging and toughening role at the nanoscale. This reduces the shrinkage channels caused by water migration on the one hand, and inhibits the propagation of micro-cracks on the other hand, making the material exhibit low drying shrinkage and good crack resistance, improving its long-term volume stability and durability. DETAILED DESCRIPTION

[0044] The technical solutions of the present application will be described in detail below with specific examples. The examples described herein are specific embodiments of the present application, which are used to illustrate the concept of the present application; all the descriptions are explanatory and exemplary, and should not be understood as limiting the embodiments of the present application and the protection scope of the present application. In addition to the examples described herein, those skilled in the art can also employ other technical solutions that are obvious based on the content disclosed in the claims and the description of the present application, which include technical solutions that employ any obvious substitutions and modifications to the examples described herein.

[0045] The chemical reagents used in the examples and comparative examples of the present application are all commercially available products without further purification or treatment.

[0046] Example 1

[0047] The present example provides a carbide slag-based low-carbon cementitious material and a preparation method thereof, and the preparation method of the carbide slag-based low-carbon cementitious material specifically comprises the following steps:

[0048] S1: A sodium lignosulfonate solution with a mass fraction of 18wt.% is prepared, and after adjusting the pH value to 12, it is heated to 85℃, and then sodium sulfite with a dosage of 25% of the mass of lignosulfonic acid and formaldehyde solution with a concentration of 38wt.% and a dosage of 12% of the mass of lignosulfonic acid are added to obtain reaction liquid A, and the reaction is carried out for 3.5h to obtain a modified lignin solution; under the protection of nitrogen, sodium hydroxide is added at 58℃ to obtain reaction liquid B, wherein the molar ratio of sodium hydroxide to sodium lignosulfonate is 2.2:1, and after the addition of epichlorohydrin, the reaction is carried out for 1.8h to obtain reaction liquid C, wherein the molar ratio of epichlorohydrin to sodium lignosulfonate is 1.4:1, and then polyethylene glycol is added for further reaction for 4.5h, wherein the molar ratio of polyethylene glycol to epichlorohydrin is 1.6:1, and then the solution is cooled and the pH value is adjusted to neutral to obtain a grafted and modified lignin solution; sodium silicate solution is added to obtain a mixed solution, wherein the ratio of the solid content of lignin to the solid content of silicon dioxide in the mixed solution is 1:1.8, the concentration of the sodium silicate solution is 42wt.%, and the mixed solution is stirred for 0.8h to obtain reaction liquid D;

[0049] S2: The calcium nitrate solution is added dropwise into reaction liquid D at room temperature to obtain reaction liquid E, wherein the molar ratio of calcium element to silicon element is 1.0:1, and the stirring and aging is carried out for 2.5h to obtain a suspension, which is then centrifuged, washed and dried to obtain a lignin-CSH regulator;

[0050] S3: The carbide slag with a specific surface area of 480m 2 / kg, the mineral powder with a specific surface area of 500m 2 / kg, and the mineral powder with a specific surface area of 450m 2The fly ash and the lignin-CSH regulator at 0.5 g / kg are placed in a mixer to perform dry mixing to obtain a composite dry powder; wherein the mass ratio of the carbide slag, the mineral powder and the fly ash is 65:30:10, and the lignin-CSH regulator is added in an amount of 1.5% of the total mass of the carbide slag, the mineral powder and the fly ash; water is added to perform wet stirring to obtain a slurry, wherein the mass ratio of the water to the total mass of the carbide slag, the mineral powder and the fly ash is 0.33:1, and the slurry is injected into a mold, and after exhaust and standard curing, the slurry is demolded to obtain the carbide slag-based low-carbon cementing material.

[0051] Example 2

[0052] The present embodiment provides a carbide slag-based low-carbon cementing material and a preparation method thereof, and the preparation method of the carbide slag-based low-carbon cementing material specifically comprises the following steps:

[0053] S1: a sodium lignosulfonate solution with a mass fraction of 10wt.% is prepared, and after the pH value of the solution is adjusted to 13, the solution is heated to 70℃, and then sodium sulfite in an amount of 10% of the mass of the sodium lignosulfonate and a formaldehyde solution in an amount of 5% of the mass of the sodium lignosulfonate are added to obtain a reaction liquid A, wherein the concentration of the formaldehyde solution is 35wt.%, and the reaction liquid A is reacted for 2h to obtain a modified lignin solution; under the protection of nitrogen, the reaction liquid A is heated to 50℃, and then sodium hydroxide is added to obtain a reaction liquid B, wherein the molar ratio of the sodium hydroxide to the sodium lignosulfonate is 1.5:1, and after the addition of epichlorohydrin, the reaction liquid B is reacted for 1h to obtain a reaction liquid C, wherein the molar ratio of the epichlorohydrin to the sodium lignosulfonate is 1:1, and then polyethylene glycol is added to continue the reaction for 3h, wherein the molar ratio of the polyethylene glycol to the epichlorohydrin is 1.2:1, and then the reaction liquid C is cooled and the pH value is adjusted to neutral to obtain a grafted modified lignin solution; a sodium silicate solution is added to obtain a mixed solution, wherein the ratio of the solid content of the lignin to the solid content of the silicon dioxide in the mixed solution is 1:1, the concentration of the sodium silicate solution is 35wt.%, and the mixed solution is stirred and mixed for 0.5h to obtain a reaction liquid D;

[0054] S2: a calcium nitrate solution is added dropwise into the reaction liquid D at room temperature to obtain a reaction liquid E, wherein the molar ratio of the calcium element to the silicon element is 1.2:1, and the reaction liquid E is stirred and aged for 1h to obtain a suspension, and then the suspension is centrifuged, washed and dried to obtain the lignin-CSH regulator;

[0055] S3: the carbide slag with a specific surface area of 400m 2 / kg of the fly ash, the mineral powder with a specific surface area of 400m 2 / kg of the fly ash, the mineral powder with a specific surface area of 400m 2The fly ash and the lignin-CSH regulator at 0.5 kg are placed in a mixer to perform dry mixing to obtain a composite dry powder; a mass ratio of the carbide slag, the mineral powder and the fly ash is 70:25:15, and a feeding amount of the lignin-CSH regulator is 1.2% of a total mass of the carbide slag, the mineral powder and the fly ash; water is added to perform wet stirring to obtain a slurry, a mass ratio of the water to the total mass of the carbide slag, the mineral powder and the fly ash is 0.3:1, the slurry is injected into a mold, exhaust, standard curing and demolding are performed to obtain the carbide slag-based low-carbon cementing material.

[0056] Example 3

[0057] The present embodiment provides a carbide slag-based low-carbon cementing material and a preparation method thereof, and the preparation method of the carbide slag-based low-carbon cementing material specifically includes the following steps:

[0058] S1: a sodium lignosulfonate solution with a mass fraction of 15wt.% is prepared, after the pH value of the sodium lignosulfonate solution is adjusted to 11.5, the sodium lignosulfonate solution is heated to 80℃, sodium sulfite with a feeding amount of 20% of the mass of the lignosulfonic acid and a formaldehyde solution with a feeding amount of 8% of the mass of the lignosulfonic acid are added to obtain a reaction liquid A, the concentration of the formaldehyde solution is 37wt.%, and the reaction liquid A is reacted for 3h to obtain a modified lignin solution; under the protection of nitrogen, sodium hydroxide is added to a reaction liquid B at 55℃, a molar ratio of the sodium hydroxide to the sodium lignosulfonate is 1.8:1, after the addition of epichlorohydrin, the reaction liquid B is reacted for 1.2h to obtain a reaction liquid C, a molar ratio of the epichlorohydrin to the sodium lignosulfonate is 1.1:1, polyethylene glycol is added to continue the reaction for 3.5h, a molar ratio of the polyethylene glycol to the epichlorohydrin is 1.4:1, the reaction liquid C is cooled and the pH value is adjusted to neutral to obtain a grafted modified lignin solution; a sodium silicate solution is added to obtain a mixed solution, a ratio of the lignin solid content to the silicon dioxide solid content in the mixed solution is 1:1.5, the concentration of the sodium silicate solution is 40wt.%, and the mixed solution is stirred and mixed for 0.7h to obtain a reaction liquid D;

[0059] S2: a calcium nitrate solution is added dropwise to the reaction liquid D at room temperature to obtain a reaction liquid E, a molar ratio of calcium to silicon is 1.1:1, and the reaction liquid E is stirred and aged for 2h to obtain a suspension, the suspension is centrifuged, washed and dried to obtain the lignin-CSH regulator;

[0060] S3: the carbide slag with a specific surface area of 450m 2 / kg of the fly ash, the mineral powder with a specific surface area of 450m 2 / kg of the fly ash, the mineral powder with a specific surface area of 450m 2The fly ash and the lignin-CSH regulator at 0.5 kg are placed in a mixer to perform dry mixing to obtain a composite dry powder; wherein the mass ratio of the carbide slag, the mineral powder and the fly ash is 68:28:12, and the lignin-CSH regulator is added in an amount of 1.4% of the total mass of the carbide slag, the mineral powder and the fly ash; water is added to perform wet stirring to obtain a slurry, wherein the mass ratio of the water to the total mass of the carbide slag, the mineral powder and the fly ash is 0.32:1, and the slurry is injected into a mold, and after exhaust and standard curing, the slurry is demolded to obtain a carbide slag-based low-carbon cementing material.

[0061] Example 4

[0062] The present embodiment provides a carbide slag-based low-carbon cementing material and a preparation method thereof, and the preparation method of the carbide slag-based low-carbon cementing material specifically comprises the following steps:

[0063] S1: a sodium lignosulfonate solution with a mass fraction of 20wt.% is prepared, and after the pH value of the solution is adjusted to 11, the solution is heated to 90℃, and then sodium sulfite in an amount of 30% of the mass of the lignosulfonic acid and a formaldehyde solution in an amount of 15% of the mass of the lignosulfonic acid are added to obtain a reaction liquid A, wherein the concentration of the formaldehyde solution is 40wt.%, and the reaction liquid A is reacted for 4h to obtain a modified lignin solution; under the protection of nitrogen, the reaction liquid A is heated to 60℃, and then sodium hydroxide is added to obtain a reaction liquid B, wherein the molar ratio of the sodium hydroxide to the sodium lignosulfonate is 2.5:1, and then epichlorohydrin is added to the reaction liquid B to react for 2h to obtain a reaction liquid C, wherein the molar ratio of the epichlorohydrin to the sodium lignosulfonate is 1.5:1, and then polyethylene glycol is added to continue the reaction for 5h, wherein the molar ratio of the polyethylene glycol to the epichlorohydrin is 1.8:1, and then the reaction liquid C is cooled and the pH value is adjusted to neutral to obtain a grafted modified lignin solution; a sodium silicate solution is added to obtain a mixed solution, wherein the ratio of the solid content of the lignin to the solid content of the silicon dioxide in the mixed solution is 1:2, the concentration of the sodium silicate solution is 45wt.%, and the mixed solution is stirred and mixed for 1h to obtain a reaction liquid D;

[0064] S2: a calcium nitrate solution is added dropwise to the reaction liquid D at room temperature to obtain a reaction liquid E, wherein the molar ratio of the calcium element to the silicon element is 0.8:1, and the reaction liquid E is stirred and aged for 3h to obtain a suspension, and then the suspension is centrifuged, washed and dried to obtain a lignin-CSH regulator;

[0065] S3: the carbide slag with a specific surface area of 500m 2 / kg of the fly ash, the mineral powder with a specific surface area of 550m 2 / kg of the fly ash, and the mineral powder with a specific surface area of 500m 2The fly ash and the lignin-CSH regulator at 0.5 kg are placed in a mixer for dry mixing to obtain a composite dry powder; wherein the mass ratio of the carbide slag, the mineral powder and the fly ash is 60:35:5, and the lignin-CSH regulator is added in an amount of 1.6% of the total mass of the carbide slag, the mineral powder and the fly ash; water is added for wet stirring to obtain a slurry, wherein the mass ratio of the water to the total mass of the carbide slag, the mineral powder and the fly ash is 0.35:1, and the slurry is injected into a mold, and after exhaust and standard curing, the carbide slag-based low-carbon cementitious material is demolded.

[0066] Comparative Example 1

[0067] The present comparative example provides a carbide slag-based low-carbon cementitious material, which is different from Example 1 in that no lignin-CSH regulator is added, and other operation steps and process parameters are exactly the same as those of Example 1.

[0068] Comparative Example 2

[0069] The present comparative example provides a carbide slag-based low-carbon cementitious material, which is different from Example 1 in that no lignin-CSH regulator is added, and the grafting modified lignin solution in S1 is prepared separately and dried into a modified lignin powder, and the C-S-H nano powder is prepared separately, and the two are physically mixed and directly used, and other operation steps and process parameters are exactly the same as those of Example 1.

[0070] Comparative Example 3

[0071] The present comparative example provides a carbide slag-based low-carbon cementitious material, which is different from Example 1 in that the polyethylene glycol grafting step in S1 is omitted, and other operation steps and process parameters are exactly the same as those of Example 1.

[0072] Comparative Example 4

[0073] The present comparative example provides a carbide slag-based low-carbon cementitious material, which is different from Example 1 in that the grafting modified lignin solution is directly prepared and dried to obtain the grafting modified lignin, and other operation steps and process parameters are exactly the same as those of Example 1.

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

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

[0076] The setting time of the mortar is tested using a Vicat apparatus: the mold is taken out of the humidity curing box and placed under the test needle, and when the test needle vertically sinks into the cement paste by 4mm±1mm from the bottom plate, the initial setting state is reached. When the test needle sinks into the test body by 0.5mm, the final setting state is reached.

[0077] The flexural strength and compressive strength of the samples cured for 28 days were tested using a DY-208JC full-automatic pressure testing machine, and the loading rate of the compressive test was set to 2400 N / s ± 200 N / s, and the loading rate of 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 cementitious materials of Examples 1-4 and Comparative Examples 1-4

[0080]

[0081] From the test results of Example 1 and Comparative Example 1, it can be seen that without adding the lignin-CSH regulator, the slurry coagulates, the fluidity cannot be measured, the setting time is extremely short, and the hardened body strength is extremely low. This is because the high dosage of carbide slag provides excessively high initial alkalinity and calcium ion concentration, greatly accelerating the dissolution of the silicon-aluminum components in the mineral powder and fly ash and the subsequent precipitation reaction of C-(A)-S-H gel, resulting in a loss of control of the reaction kinetics. The slurry cannot form a uniform flow state, quickly loses operability, and the final hardened body has serious macroscopic defects due to non-dense particle accumulation and encapsulation of a large number of bubbles, and thus cannot form an effective strength bearing structure, so the flexural and compressive strengths are at an extremely low level.

[0082] From the test results of Example 1 and Comparative Example 2, it can be seen that without adding the lignin-CSH regulator, the grafting modified lignin solution in S1 is prepared separately and dried into a modified lignin powder, and the C-S-H nano powder is prepared separately, and both are physically mixed according to the solid content ratio in Example 1, resulting in a decrease in fluidity, setting time control, and final mechanical properties. This is because the physical mixing of the components cannot form the unique synergistic structure of in-situ synthesis. The intrinsic connection of molecular anchoring is missing, and the C-S-H nanoparticles will agglomerate in the strong electrolyte slurry, greatly reducing their effective specific surface area and dispersibility as heterogeneous nucleation, and thus the heterogeneous nucleation efficiency decreases, resulting in a decrease in flexural and compressive strengths. At the same time, the agglomeration of nanoparticles increases the viscosity of the slurry, resulting in poor fluidity; the regulation of calcium ions by modified lignin is also weakened due to the interference of nanoparticles, affecting the setting time.

[0083] From the test results of Example 1 and Comparative Example 3, it can be seen that the polyethylene glycol grafting step in S1 is omitted, and C-S-H nanoparticles are directly grown in the modified lignin solution in-situ, and the polyethylene glycol hydrophilic segment grafting step is omitted, resulting in a decrease in slurry fluidity and a decrease in final mechanical properties. The reason is that the lignin modified only by sulfonation mainly relies on electrostatic repulsion to maintain dispersion. In a high calcium ion concentration environment, a large number of Ca 2+The double electric layer on the surface of the particles will be compressed, and the negative charge of the sulfonic acid group will be partially neutralized by the "calcium bridge" effect, thereby weakening the electrostatic repulsion. Without the steric hindrance effect provided by the long chain of polyethylene glycol, the dispersion capacity of the regulator under high ionic strength decreases, resulting in poor slurry fluidity. The decrease in slurry dispersion affects the uniform arrangement and hydration environment of the particles, and further affects the strength of the final hardened body.

[0084] As can be seen from the test results of Example 1 and Comparative Example 4, the graft-modified lignin solution is directly prepared and dried to obtain the graft-modified lignin without the in-situ growth step of C-S-H. Although the slurry has excellent fluidity and longer setting time, the flexural and compressive strengths are reduced. This is because the regulator only has excellent dispersion and retarding functions, and lacks the core role of heterogeneous nucleation. Without the guidance of C-S-H nanocrystals, the nucleation energy barrier of the hydration product is high, the generation process is slow and disordered, and the quality of the final gel network is poor. The improvement of fluidity and the extension of setting time may be due to the stronger dispersion and retarding capacity, but this cannot be converted into effective microstructure and mechanical strength.

[0085] The above merely provides a specific implementation of the present application, but the protection scope of the present application is not limited thereto. It should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily conceived by those skilled in the art, and all such changes and replacements fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for preparing a carbide slag-based low-carbon cementitious material, characterized in that, The preparation method comprises: S1: preparing a sodium lignosulfonate solution, adjusting the pH value and heating, adding sodium sulfite and formaldehyde solution to obtain reaction liquid A, and reacting to obtain a modified lignin solution; under nitrogen protection, adding sodium hydroxide to obtain reaction liquid B, adding epichlorohydrin to react to obtain reaction liquid C, adding polyethylene glycol to continue the reaction, cooling and adjusting the pH value to neutral to obtain a grafted modified lignin solution; adding a sodium silicate solution to obtain a mixed solution, and stirring to obtain reaction liquid D; S2: adding a calcium nitrate solution to reaction liquid D at room temperature to obtain reaction liquid E, stirring and aging to obtain a suspension, centrifuging, washing and drying to obtain a lignin-CSH regulator; S3: placing carbide slag, mineral powder, fly ash and the lignin-CSH regulator in a mixer to perform dry mixing to obtain a composite dry powder; adding water to perform wet stirring to obtain a slurry, pouring the slurry into a mold, exhausting, standard curing and demolding to obtain a carbide slag-based low-carbon cementitious material.

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

3. A method of preparing a carbide slag-based low carbon cementitious 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. A method of preparing a carbide slag-based low carbon cementitious 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 the lignin solid content in the mixed solution to the silicon dioxide solid content in the sodium silicate solution is 1:(1-2).

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

1.

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

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

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

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

1.

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

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