A nano calcium carbonate, alkali residue-based solid waste cementing material early strength agent, a preparation method and application thereof

Abstract

The application relates to the technical field of building material admixtures, and particularly discloses a nano calcium carbonate, alkali residue-based solid waste cementitious material early strength agent, a preparation method and application. The preparation method of the nano calcium carbonate comprises the following steps: reacting alkali residue and a chlorine-containing solution, performing solid-liquid separation, obtaining filtrate, adding an alcohol solvent into the filtrate, introducing carbon dioxide and nitrogen for carbonization reaction, and performing crystallization to obtain nano calcium carbonate. The growth process of the nano calcium carbonate crystal is controlled by controlling the conditions of the carbonization reaction and the flow rates of the nitrogen and the carbon dioxide, the method has the advantages of simple operation, the prepared nano calcium carbonate is applied to the alkali residue-based solid waste cementitious material early strength agent, the early strength, the initial setting time and the final setting time of the solid waste cementitious material can be improved, and a new idea is provided for the preparation of the alkali residue-based solid waste cementitious material early strength agent.

Description

Technical Field

[0001] This invention relates to the field of building material admixtures, and in particular to an early-strength agent for nano-calcium carbonate and alkali slag-based solid waste cementitious materials, its preparation method, and its application. Background Technology

[0002] Currently, the main ways to reduce carbon emissions in the cement industry include raw material substitution technology, energy efficiency management technology, and fuel substitution technology. Among these, raw material substitution technology is an important means of reducing carbon emissions in the cement industry.

[0003] Solid waste-based cementitious materials are hydraulic cementitious materials made from granulated blast furnace slag, steel slag, industrial by-product gypsum, and other industrial solid wastes through fine grinding. These materials can completely replace cement in applications such as concrete preparation and mine backfilling. However, compared to ordinary Portland cement, solid waste-based cementitious materials suffer from slow early hydration reactions, low strength, and long setting times, limiting their application in some projects. For example, in winter construction or projects with high construction schedule requirements, the cementitious material needs to reach a certain strength within a short time to meet the demands of subsequent construction processes. Currently available early-strength agents are not specifically designed for solid waste-based cementitious materials and cannot effectively solve the problem of insufficient early strength. Furthermore, the preparation processes of some early-strength agents are complex and costly, hindering large-scale application. Therefore, there is an urgent need to develop an early-strength agent and its preparation method to address the problems of insufficient early strength and long setting times encountered by existing early-strength agents in solid waste-based cementitious materials. Summary of the Invention

[0004] In view of this, the present invention provides a nano-calcium carbonate, an early-strength agent for alkali slag-based solid waste cementitious materials, its preparation method, and its application. The early-strength agent for alkali slag-based solid waste cementitious materials provided by the present invention effectively solves the problems of low early-stage strength and long setting time of solid waste cementitious materials while ensuring that the strength of the solid waste cementitious materials does not decrease in the later stages. At the same time, it reduces preparation costs and simplifies the preparation process, providing a new approach for the preparation of early-strength agents for alkali slag-based solid waste cementitious materials.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0006] This invention provides a method for preparing nano-calcium carbonate, comprising the following steps:

[0007] The alkaline residue and chlorine-containing solution are reacted, and the solid and liquid are separated to obtain the filtrate.

[0008] An alcohol solvent was added to the filtrate, and carbon dioxide and nitrogen were introduced to carry out a carbonization reaction and crystallization to obtain nano-calcium carbonate.

[0009] Currently, the preparation method of nano-calcium carbonate generally includes the following steps: grinding an alkaline residue suspension, an ion-promoting solvent, and grinding media together, removing the supernatant, and then mixing and grinding the slurry with a dispersant, plasticizer, and grinding media again. However, this preparation method has obvious disadvantages. The two grinding processes require the introduction of grinding media, which can easily introduce impurities due to wear, thus reducing the purity of the nano-calcium carbonate and affecting the early strength improvement of the cementitious material by the alkaline residue-based solid waste cementitious material's early strength. Secondly, the method is cumbersome, resulting in low preparation efficiency and increased energy consumption and production costs. Furthermore, since the dispersant may be destroyed and ineffective during the grinding process, there is a potential risk of particle agglomeration; using it in the alkaline residue-based solid waste cementitious material's early strength agent will reduce the performance of the agent.

[0010] During their research, the inventors discovered that mixing alkaline slag with a chlorine-containing solution to generate soluble CaCl2 allows for efficient dissolution of calcium and separation from impurities in the slag, thus improving the utilization rate of the slag. An alcohol solvent acts as a solvent in the reaction system, promoting the carbonation reaction; it also acts as a dispersant, ensuring uniform dispersion of the generated nano-calcium carbonate and preventing particle agglomeration. When carbon dioxide and nitrogen are introduced simultaneously, nitrogen can dilute the carbon dioxide concentration to a certain extent, controlling the carbonation reaction rate and thus the growth process of calcium carbonate crystals. Simultaneously, nitrogen can synergistically enhance propylene glycol, preventing localized supersaturation that could lead to particle agglomeration. This process yields high-purity, uniformly sized, and evenly dispersed nano-calcium carbonate. When applied as an early-strength agent in slag-based solid waste cementitious materials, it significantly improves the strength, initial setting time, and final setting time of the solid waste cementitious materials at various ages. Furthermore, the method for preparing nano-calcium carbonate provided by this invention not only achieves resource utilization of slag but also reduces the cost of solid waste treatment and production, making the preparation process both economical and environmentally friendly.

[0011] Preferably, the fineness of the alkali residue is 100 mesh to 500 mesh.

[0012] Preferably, the chlorine-containing solution is an ammonium chloride solution.

[0013] Preferably, the concentration of the chlorine-containing solution is 2 mol / L to 5 mol / L.

[0014] It should be further noted that the ammonium chloride solution is an aqueous solution of ammonium chloride.

[0015] Preferably, the alcohol solvent is propylene glycol.

[0016] Preferably, the mass-to-volume ratio of the alkaline residue to the chlorine-containing solution is 1 g:(4-5) mL.

[0017] This invention further limits the ratio of alkaline residue to chlorine-containing solution, which enables calcium ions in the alkaline residue to dissolve fully, thereby improving the utilization rate of the alkaline residue.

[0018] Preferably, the amount of alcohol solvent added is 5% to 7% of the mass of the alkali residue.

[0019] It should be further noted that the carbon dioxide and nitrogen are introduced simultaneously as a mixed gas.

[0020] Preferably, the volume ratio of carbon dioxide to nitrogen is (3-5):(5-7).

[0021] Preferably, the carbon dioxide flow rate is 0.3 L / min to 0.5 L / min.

[0022] The optimal flow rates of carbon dioxide and nitrogen are beneficial for further controlling the growth process of nano-calcium carbonate crystals, thereby obtaining nano-calcium carbonate with high purity, uniform particle size and uniform dispersion, and improving the early strength, initial setting time and final setting time of solid waste cementitious materials.

[0023] Preferably, the reaction temperature is 25°C to 30°C.

[0024] Preferably, the reaction time is 2h to 2.5h.

[0025] Preferably, the stirring rate during the reaction is 900 r / min to 950 r / min.

[0026] It should be further noted that after the reaction is completed, the reaction system is filtered, and an alcohol solvent is added to the filtrate.

[0027] Preferably, the carbonization reaction temperature is 30°C to 33°C.

[0028] Preferably, the carbonization reaction ends when the pH of the reaction system drops to 6-8.

[0029] Preferably, the crystallization is static crystallization.

[0030] Preferably, the crystallization temperature is 20°C to 22°C.

[0031] Preferably, the crystallization time is 30 min to 35 min.

[0032] It should be further noted that after crystallization, the reaction mixture needs to be centrifuged and dried.

[0033] This invention provides a nano-calcium carbonate, which is prepared by the above-described method for preparing nano-calcium carbonate.

[0034] This invention provides an early-strength agent for alkali slag-based solid waste cementitious materials, comprising the following raw material components by mass percentage: 40%–60% nano-calcium carbonate, 10%–35% modifier, and 10%–30% fly ash;

[0035] The modifier comprises an organic liquid phase and an inorganic solid phase, wherein the organic liquid phase is prepared by reacting triethanolamine and diethanol monoisopropanolamine; and the inorganic solid phase comprises calcium oxide and aluminum sulfate.

[0036] During the research process, the inventors discovered that triethanolamine or diethanolamine monoisopropanolamine, as commonly used components in early-strength agents for alkali slag-based solid waste cementitious materials, do not significantly improve the strength and setting time of solid waste cementitious materials, whether added alone or in combination. Therefore, the inventors broke away from existing approaches and prepared an organic liquid phase by reacting triethanolamine or diethanolamine monoisopropanolamine. This organic liquid phase has better dispersibility and surface activity, enabling it to effectively adsorb onto the particle surface of solid waste cementitious materials, reduce the surface energy between particles, promote particle dispersion, and accelerate the hydration reaction. This, in turn, improves the performance of the early-strength agent for alkali-based solid waste cementitious materials, significantly enhancing the early strength of the materials. Simultaneously, the organic liquid phase forms complexes with components in the solid waste cementitious materials, lowering the activation energy of the hydration reaction and allowing it to occur rapidly even at lower temperatures, further improving the early strength. Furthermore, the organic liquid phase complexes with the specific nano-calcium carbonate and fly ash of this invention. This not only prevents the agglomeration of nano-calcium carbonate, thus improving the performance of the early-strength agent for alkali-based solid waste cementitious materials, but also activates the dissolution of active components in fly ash, enhancing the early-strength performance of the materials. The synergistic effect of these three factors significantly improves the early strength, 28-day strength, and setting time of the solid waste cementitious materials.

[0037] The inorganic solid phase provided by this invention comprises calcium oxide and aluminum sulfate. Calcium oxide can rapidly increase the pH value of solid waste cementitious materials, promoting the hydration reaction of active substances such as fly ash, thus overcoming the problems of low early alkalinity, slow strength gain, and long setting time in solid waste cementitious materials. Calcium oxide can also react with active components in fly ash and aluminum sulfate to generate expansive hydration products such as ettringite, filling the voids in the solid waste cementitious materials, increasing their strength, and shortening the setting time. The organic liquid phase further promotes the formation and distribution of the generated hydration products, not only improving the strength of the solid waste cementitious materials but also shortening the setting time, greatly improving the performance of the early-strength agent for alkali-based solid waste cementitious materials.

[0038] In this invention, specific nano-calcium carbonate works synergistically with organic liquid phase, inorganic solid phase and fly ash to accelerate the early hydration process and improve early strength. When the alkaline slag-based solid waste cementitious material early strength agent provided by this invention is applied to solid waste cementitious materials, it not only improves early strength and 28-day strength but also shortens the setting time.

[0039] Preferably, the method for preparing the organic liquid phase includes the following steps:

[0040] Triethanolamine and diethanolamine monoisopropanolamine are added to a solvent, then a catalyst is added, and the mixture is heated to 120°C–140°C to react and obtain the organic liquid phase.

[0041] The method for preparing the organic liquid phase provided by this invention is simple to operate, and the prepared organic liquid phase has stable chemical properties, which can further improve the performance of the early strength agent of alkali slag-based solid waste cementitious materials.

[0042] Preferably, the solvent is toluene.

[0043] Preferably, the catalyst is p-toluenesulfonic acid.

[0044] Preferably, the mass ratio of triethanolamine to diethanolamine monoisopropanolamine is 1:(1 to 1.3).

[0045] Preferably, the amount of catalyst added is 1% to 5% of the total mass of the triethanolamine and diethanol monoisopropanolamine.

[0046] Preferably, the amount of solvent added is 200% to 250% based on the total mass of triethanolamine and diethanolmonoisopropanolamine being 100%.

[0047] Preferably, the reaction time is 5h to 6h.

[0048] Preferably, after the reaction is complete, the reaction system is cooled to room temperature, washed with water, and distilled under reduced pressure to obtain the organic liquid phase.

[0049] Preferably, the mass ratio of calcium oxide to aluminum sulfate is (3 + 3m) / (3 + 3m). Fa ω Fa ~5+3m Fa ω Fa ):(1~2), where m Fa ω represents the mass percentage of fly ash in the early-strength agent of alkali slag-based solid waste cementitious materials. Fa The percentage of Al2O3 in fly ash is represented by its mass.

[0050] By limiting the ratio of calcium oxide to aluminum sulfate, this invention can fully activate the activity of active substances such as fly ash under the premise of alkalinity of solid waste cementitious materials, generating secondary hydration products with cementitious properties. These products can fill the pores of cement stone, improve the density of the structure, enhance the early strength of solid waste cementitious materials, improve the 28-day strength, and shorten the setting time.

[0051] Preferably, the fineness of the inorganic solid phase is 200 mesh to 500 mesh.

[0052] Preferably, the mass ratio of the organic liquid phase to the inorganic solid phase is 3:(4-5).

[0053] This invention limits the ratio between the organic liquid phase and the inorganic solid phase, which can further improve the performance of the early strength agent of alkali slag-based solid waste cementitious materials, thereby improving the early strength and later strength of solid waste cementitious materials and shortening the setting time.

[0054] Preferably, the mass percentage of Al2O3 in the fly ash is 25% to 40%.

[0055] Preferably, the fly ash has a fineness of 400 mesh to 600 mesh and a loss on ignition of <8.0%.

[0056] This invention provides a method for preparing an early-strength agent for alkali slag-based solid waste cementitious materials, comprising the following steps:

[0057] The weighed nano-calcium carbonate, modifier, and fly ash are mixed evenly to obtain an early-strength agent for alkali slag-based solid waste cementitious materials.

[0058] The present invention also provides the application of the above-mentioned alkali slag-based solid waste cementitious material early strength agent or the alkali slag-based solid waste cementitious material early strength agent prepared by the above-mentioned method for preparing the alkali slag-based solid waste cementitious material early strength agent in solid waste cementitious materials.

[0059] The alkaline slag-based solid waste cementitious material early strength agent provided by this invention, when applied to solid waste cementitious materials, improves the early strength of solid waste cementitious materials and shortens the setting time, while also ensuring the later strength growth of solid waste cementitious materials. This realizes the resource utilization of industrial waste residue, reduces waste emissions, and has significant environmental and economic benefits. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0061] Example 1

[0062] This embodiment provides an early strength agent for alkali slag-based solid waste cementitious materials, comprising the following raw material components by mass percentage: 60% nano-calcium carbonate, 25% modifier, and 15% fly ash;

[0063] The modifier consists of an organic liquid phase and an inorganic solid phase in a mass ratio of 3:4;

[0064] The preparation method of nano-calcium carbonate includes the following steps:

[0065] Step 1: Dry the alkali residue in a 105℃ oven, grind and crush it to a fineness of 100 mesh, transfer the alkali residue (100g) into a reactor, add 2mol / L ammonium chloride aqueous solution (500mL), react at 25℃ for 2h, stir at a rate of 900r / min during the reaction, filter the reaction system after the reaction is completed to obtain the filtrate.

[0066] Step 2: Add propylene glycol (5g) to the filtrate, then pass a mixture of carbon dioxide and nitrogen (volume ratio of carbon dioxide to nitrogen is 3:7) at a flow rate of 0.3L / min (calculated as carbon dioxide). Carry out the carbonization reaction at 30℃, monitor the reaction solution, and stop the gas flow when the pH drops to 7-8. Let it stand at 20℃ for 30min to crystallize, centrifuge, and dry to obtain nano calcium carbonate.

[0067] The preparation method of organic liquid phase includes the following steps:

[0068] Triethanolamine (100g) and diethanolamine monoisopropanolamine (100g) were added to toluene (400g), and then p-toluenesulfonic acid (2g) was added. The mixture was heated to 130℃ and reacted for 5 hours until no more water was generated. After the reaction was completed, the reaction system was naturally cooled to room temperature, washed with water 3-4 times, and the toluene solvent was removed by vacuum distillation to obtain an organic liquid phase.

[0069] The mass ratio of calcium oxide to aluminum sulfate in the inorganic solid phase with a fineness of 200 mesh is (3 + 3 × 15% × 25%): 1.5, that is, the mass ratio of calcium oxide to aluminum sulfate is 3.1125: 1.5.

[0070] The fly ash contains 25% Al2O3 by mass, has a fineness of 500 mesh, and a loss on ignition of 6.5%.

[0071] Example 2

[0072] This embodiment provides an early strength agent for alkali slag-based solid waste cementitious materials, comprising the following raw material components by mass percentage: 40% nano-calcium carbonate, 30% modifier, and 30% fly ash;

[0073] The modifier consists of an organic liquid phase and an inorganic solid phase in a mass ratio of 3:5;

[0074] The preparation method of nano-calcium carbonate includes the following steps:

[0075] Step 1: Dry the alkali residue in a 105℃ oven, grind and crush it to a fineness of 400 mesh, transfer the alkali residue (100g) into a reactor, add 4mol / L ammonium chloride aqueous solution (400mL), react at 30℃ for 2.5h, stir at a rate of 950r / min during the reaction, filter the reaction system after the reaction is completed to obtain the filtrate;

[0076] Step 2: Add propylene glycol (6g) to the filtrate, then pass a mixture of carbon dioxide and nitrogen (volume ratio of carbon dioxide to nitrogen is 3.5:6.5) at a flow rate of 0.35L / min (calculated as carbon dioxide). Carry out the carbonization reaction at 33℃, monitor the reaction solution, and stop the gas flow when the pH drops to 6-7. Let it stand at 22℃ for 35min to crystallize, centrifuge, and dry to obtain nano calcium carbonate.

[0077] The preparation method of organic liquid phase includes the following steps:

[0078] Triethanolamine (100g) and diethanolamine monoisopropanolamine (120g) were added to toluene (440g), followed by p-toluenesulfonic acid (11g). The mixture was heated to 125℃ and reacted for 6 hours until no more water was generated. After the reaction was completed, the reaction system was naturally cooled to room temperature, washed with water 3-4 times, and the toluene solvent was removed by vacuum distillation to obtain an organic liquid phase.

[0079] The mass ratio of calcium oxide to aluminum sulfate in the inorganic solid phase with a fineness of 500 mesh is (4 + 3 × 30% × 37%): 1, that is, the mass ratio of calcium oxide to aluminum sulfate is 4.333: 1.5.

[0080] The fly ash contains 37% Al2O3 by mass, has a fineness of 600 mesh, and a loss on ignition of 5.5%.

[0081] Example 3

[0082] This embodiment provides an early strength agent for alkali slag-based solid waste cementitious materials, comprising the following raw material components by mass percentage: 50% nano-calcium carbonate, 30% modifier, and 20% fly ash;

[0083] The modifier consists of an organic liquid phase and an inorganic solid phase in a mass ratio of 3:5;

[0084] The preparation method of nano-calcium carbonate includes the following steps:

[0085] Step 1: Dry the alkali residue in a 105℃ oven, grind and crush it to a fineness of 500 mesh, transfer the alkali residue (80g) into a reactor, add 5mol / L ammonium chloride aqueous solution (320mL), react at 30℃ for 2h, stir at a rate of 920r / min during the reaction, filter the reaction system after the reaction is completed to obtain the filtrate.

[0086] Step 2: Add propylene glycol (7g) to the filtrate, then pass a mixture of carbon dioxide and nitrogen (volume ratio of carbon dioxide to nitrogen is 5:5) at a flow rate of 0.5L / min (calculated as carbon dioxide). Carry out the carbonization reaction at 30℃, monitor the reaction solution, and stop the gas flow when the pH drops to 6-7. Let it stand at 20℃ for 30min to crystallize, centrifuge, and dry to obtain nano calcium carbonate.

[0087] The preparation method of organic liquid phase includes the following steps:

[0088] Triethanolamine (100g) and diethanolamine monoisopropanolamine (130g) were added to toluene (575g), followed by p-toluenesulfonic acid (2.3g). The mixture was heated to 140℃ and reacted for 5.5h until no more water was generated. After the reaction was completed, the reaction system was naturally cooled to room temperature, washed with water 3-4 times, and the toluene solvent was removed by vacuum distillation to obtain an organic liquid phase.

[0089] The mass ratio of calcium oxide to aluminum sulfate in the inorganic solid phase with a fineness of 400 mesh is (5 + 3 × 20% × 38%): 1, that is, the mass ratio of calcium oxide to aluminum sulfate is 5.228: 1.5.

[0090] The fly ash contains 38% Al2O3 by mass, has a fineness of 500 mesh, and a loss on ignition of 4%.

[0091] Comparative Example 1

[0092] This comparative example provides an early strength agent. The difference between this comparative example and Example 1 lies in the preparation method of calcium carbonate; specifically, it includes the following:

[0093] The early strength agent comprises the following raw material components by weight percentage: 60% calcium carbonate particles, 25% modifier, and 15% fly ash;

[0094] The modifier consists of an organic liquid phase and an inorganic solid phase in a mass ratio of 3:4;

[0095] The method for preparing calcium carbonate granules includes the following steps:

[0096] Step 1: Dry the alkali residue in a 105℃ oven, grind and crush it to a fineness of 100 mesh, transfer the alkali residue (100g) into a reactor, add 2mol / L ammonium chloride aqueous solution (500mL), react at 25℃ for 2h, stir at a rate of 900r / min during the reaction, filter the reaction system after the reaction is completed to obtain the filtrate.

[0097] Step 2: Add propylene glycol (5g) to the filtrate, then introduce carbon dioxide at a flow rate of 0.3L / min and carry out the carbonation reaction at 30℃. Monitor the reaction solution and stop the gas flow when the pH drops to 7-8. Let it stand at 20℃ for 30min to crystallize, centrifuge, and dry to obtain calcium carbonate particles.

[0098] The preparation method of organic liquid phase includes the following steps:

[0099] Triethanolamine (100g) and diethanolamine monoisopropanolamine (100g) were added to toluene (400g), and then p-toluenesulfonic acid (2g) was added. The mixture was heated to 130℃ and reacted for 5 hours until no more water was generated. After the reaction was completed, the reaction system was naturally cooled to room temperature, washed with water 3-4 times, and the toluene solvent was removed by vacuum distillation to obtain an organic liquid phase.

[0100] The mass ratio of calcium oxide to aluminum sulfate in the inorganic solid phase with a fineness of 200 mesh is (3 + 3 × 15% × 25%): 1.5, that is, the mass ratio of calcium oxide to aluminum sulfate is 3.1125: 1.5.

[0101] The fly ash contains 25% Al2O3 by mass, has a fineness of 500 mesh, and a loss on ignition of 6.5%.

[0102] Comparative Example 2

[0103] This comparative example provides an early strength agent. The difference between this comparative example and Example 1 is that the organic liquid phase includes triethanolamine and diethanol monoisopropanolamine; specifically, it includes the following:

[0104] The early strength agent comprises the following raw material components by weight percentage: 60% nano-calcium carbonate, 25% modifier, and 15% fly ash;

[0105] The modifier consists of an organic liquid phase and an inorganic solid phase in a mass ratio of 3:4;

[0106] The preparation method of nano-calcium carbonate includes the following steps:

[0107] Step 1: Dry the alkali residue in a 105℃ oven, grind and crush it to a fineness of 100 mesh, transfer the alkali residue (100g) into a reactor, add 2mol / L ammonium chloride aqueous solution (500mL), react at 25℃ for 2h, stir at a rate of 900r / min during the reaction, filter the reaction system after the reaction is completed to obtain the filtrate.

[0108] Step 2: Add propylene glycol (5g) to the filtrate, then pass a mixture of carbon dioxide and nitrogen (volume ratio of carbon dioxide to nitrogen is 3:7) at a flow rate of 0.3L / min (calculated as carbon dioxide). Carry out the carbonization reaction at 30℃, monitor the reaction solution, and stop the gas flow when the pH drops to 7-8. Let it stand at 20℃ for 30min to crystallize, centrifuge, and dry to obtain nano calcium carbonate.

[0109] The organic liquid phase is a mixture of triethanolamine (100g) and diethanolamine monoisopropanolamine (100g);

[0110] The mass ratio of calcium oxide to aluminum sulfate in the inorganic solid phase with a fineness of 200 mesh is (3 + 3 × 15% × 25%): 1.5, that is, the mass ratio of calcium oxide to aluminum sulfate is 3.1125: 1.5.

[0111] The fly ash contains 25% Al2O3 by mass, has a fineness of 500 mesh, and a loss on ignition of 6.5%.

[0112] Comparative Example 3

[0113] This comparative example provides an early strength agent. The difference between this comparative example and Example 1 is that fly ash is replaced with an equal amount of slag powder; specifically, it includes the following:

[0114] The early strength agent comprises the following raw material components by weight percentage: 60% nano-calcium carbonate, 25% modifier, and 15% slag powder;

[0115] The modifier consists of an organic liquid phase and an inorganic solid phase in a mass ratio of 3:4;

[0116] The preparation method of nano-calcium carbonate includes the following steps:

[0117] Step 1: Dry the alkali residue in a 105℃ oven, grind and crush it to a fineness of 100 mesh, transfer the alkali residue (100g) into a reactor, add 2mol / L ammonium chloride aqueous solution (500mL), react at 25℃ for 2h, stir at a rate of 900r / min during the reaction, filter the reaction system after the reaction is completed to obtain the filtrate.

[0118] Step 2: Add propylene glycol (5g) to the filtrate, then pass carbon dioxide and nitrogen gas to obtain a mixed gas (volume ratio of carbon dioxide to nitrogen gas is 3:7). The flow rate is 0.3L / min for carbon dioxide. Carry out the carbonization reaction at 30℃, monitor the reaction solution, and stop the gas flow when the pH drops to 7-8. Let it stand at 20℃ for 30min to crystallize, centrifuge, and dry to obtain nano calcium carbonate.

[0119] The preparation method of organic liquid phase includes the following steps:

[0120] Triethanolamine (100g) and diethanolamine monoisopropanolamine (100g) were added to toluene (400g), and then p-toluenesulfonic acid (2g) was added. The mixture was heated to 130℃ and reacted for 5 hours until no more water was generated. After the reaction was completed, the reaction system was naturally cooled to room temperature, washed with water 3-4 times, and the toluene solvent was removed by vacuum distillation to obtain an organic liquid phase.

[0121] The mass ratio of calcium oxide to aluminum sulfate in the inorganic solid phase with a fineness of 200 mesh is (3 + 3 × 15% × 13.2%): 1.5, that is, the mass ratio of calcium oxide to aluminum sulfate is 3.0594: 1.5.

[0122] The slag powder contains 13.2% Al2O3 by mass and has a fineness of 500 mesh.

[0123] The early-strength agents prepared in Examples 1-3 and Comparative Examples 1-3 were mixed with solid waste cementitious materials, standard sand, and water, and the formulation was as follows:

[0124] 6.75g of early strength agent, 450g of solid waste cementitious material, 1350g of standard sand and 225g of water;

[0125] The proportions of solid waste cementitious materials are: 15% steel slag, 70% blast furnace slag, and 15% desulfurized gypsum.

[0126] The mortar was mixed, molded, and cured according to the method in GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)" and the strength was tested at 12h, 1d, 3d, and 28d. The test results of the strength and setting time of the mortar specimens are shown in Table 1.

[0127] Table 1

[0128]

[0129] As shown in Table 1, the early strength agent for alkali slag-based solid waste cementitious materials provided in the embodiments of the present invention can significantly improve the strength of solid waste cementitious materials at all ages, and at the same time shorten the setting time.

[0130] Comparative Example 1 altered the preparation method of calcium carbonate by not introducing nitrogen gas, which ultimately affected the dispersion, purity, and morphology of calcium carbonate particles, thereby influencing the strength and setting time of the solid waste cementitious material at various ages.

[0131] In Comparative Examples 2 and 3, after replacing the organic liquid phase or replacing the fly ash, the early strength agent of the prepared alkali slag-based solid waste cementitious material was applied to the solid waste cementitious material, and its strength at all ages was significantly reduced, and the setting time was also increased.

[0132] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An early-strength agent for alkali slag-based solid waste cementitious materials, characterized in that, It is composed of the following raw material components by mass percentage: 40%~60% nano-calcium carbonate, 25%~35% modifier and 10%~30% fly ash; The modifier is composed of an organic liquid phase and an inorganic solid phase in a mass ratio of 3:(4~5), wherein the inorganic solid phase is composed of calcium oxide and aluminum sulfate; the mass ratio of calcium oxide to aluminum sulfate is (3+3m) Fa ω Fa ~5+3m Fa ω Fa ): (1~2), where m Fa ω represents the mass percentage of fly ash in the early-strength agent of alkali slag-based solid waste cementitious materials. Fa The mass percentage of Al2O3 in fly ash; The fly ash contains 25% to 40% Al2O3 by mass. The method for preparing the organic liquid phase includes the following steps: Triethanolamine and diethanolamine monoisopropanolamine were added to a solvent, and then p-toluenesulfonic acid was added. The temperature was raised to 120℃~140℃ for reaction, and the reaction time was 5h~6h. After the reaction was completed, the reaction system was cooled to room temperature, washed with water, and distilled under reduced pressure to obtain the organic liquid phase. The mass ratio of triethanolamine to diethanolamine monoisopropanolamine is 1:(1~1.3). Based on the total mass of triethanolamine and diethanolamine monoisopropanolamine being 100%, the amount of p-toluenesulfonic acid added is 1% to 5%; The preparation method of the nano-calcium carbonate includes the following steps: The alkaline residue and ammonium chloride aqueous solution are reacted to generate soluble CaCl2. The solid and liquid are separated to obtain the filtrate. Propylene glycol was added to the filtrate, and carbon dioxide and nitrogen were introduced to carry out a carbonization reaction and crystallization to obtain nano-calcium carbonate; the volume ratio of carbon dioxide to nitrogen was (3~5):(5~7). The carbon dioxide flow rate is 0.3 L / min to 0.5 L / min.

2. The early-strength agent for alkali-based solid waste cementitious materials as described in claim 1, characterized in that, The mass-to-volume ratio of the alkaline residue and the ammonium chloride aqueous solution is 1 g: (4~5) mL, wherein the concentration of the ammonium chloride aqueous solution is 2 mol / L~5 mol / L.

3. The early-strength agent for alkali-based solid waste cementitious materials as described in claim 1, characterized in that, The amount of propylene glycol added is 5% to 7% of the mass of the alkali residue; and / or The carbonization reaction is carried out at a temperature of 30℃~33℃.

4. The early-strength agent for alkali-based solid waste cementitious materials as described in claim 1, characterized in that, The amount of solvent added is 200% to 250%, based on the total mass of triethanolamine and diethanol monoisopropanolamine being 100%.

5. A method for preparing an early-strength agent for alkali slag-based solid waste cementitious materials according to any one of claims 1 to 4, characterized in that, The steps include the following: The weighed nano-calcium carbonate, modifier and fly ash are mixed evenly to obtain an early strength agent for alkali slag-based solid waste cementitious materials. Based on the total mass of the nano-calcium carbonate, modifier, and fly ash as 100%, the mass percentage of the nano-calcium carbonate is 40%~60%, the mass percentage of the modifier is 25%~35%, and the mass percentage of the fly ash is 10%~30%. The modifier is composed of an organic liquid phase and an inorganic solid phase in a mass ratio of 3:(4~5), wherein the inorganic solid phase is composed of calcium oxide and aluminum sulfate; the mass ratio of calcium oxide to aluminum sulfate is (3+3m) Fa ω Fa ~5+3m Fa ω Fa ): (1~2), where m Fa ω represents the mass percentage of fly ash in the early-strength agent of alkali slag-based solid waste cementitious materials. Fa The mass percentage of Al2O3 in fly ash; The fly ash contains 25% to 40% Al2O3 by mass. The method for preparing the organic liquid phase includes the following steps: Triethanolamine and diethanolamine monoisopropanolamine were added to a solvent, and then p-toluenesulfonic acid was added. The temperature was raised to 120℃~140℃ for reaction, and the reaction time was 5h~6h. After the reaction was completed, the reaction system was cooled to room temperature, washed with water, and distilled under reduced pressure to obtain the organic liquid phase. The mass ratio of triethanolamine to diethanolamine monoisopropanolamine is 1:(1~1.3). Based on the total mass of triethanolamine and diethanolamine monoisopropanolamine being 100%, the amount of p-toluenesulfonic acid added is 1% to 5%; The preparation method of the nano-calcium carbonate includes the following steps: The alkaline residue and ammonium chloride aqueous solution are reacted to generate soluble CaCl2. The solid and liquid are separated to obtain the filtrate. Propylene glycol was added to the filtrate, and carbon dioxide and nitrogen were introduced to carry out a carbonization reaction and crystallization to obtain nano-calcium carbonate; the volume ratio of carbon dioxide to nitrogen was (3~5):(5~7). The carbon dioxide flow rate is 0.3 L / min to 0.5 L / min.

6. The application of the alkali slag-based solid waste cementitious material early strength agent according to any one of claims 1 to 4, or the alkali slag-based solid waste cementitious material early strength agent prepared by the preparation method of the alkali slag-based solid waste cementitious material early strength agent according to claim 5, in solid waste cementitious materials.

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