A low-carbon, low-clinker cement based on a dual-excitation system and its preparation method

Abstract

This invention belongs to the field of cement preparation technology, specifically relating to a low-carbon, low-clinker cement based on a dual-activation system and its preparation method. The raw materials, by dry weight, include: 38-52 parts fly ash, 15-25 parts slag, 5-10 parts carbide slag, 5-10 parts desulfurized gypsum, 3-10 parts lithium slag, 8-18 parts silicate clinker, 5-12 parts sulfate-activated clinker, and 0.05-0.3 parts grinding aid. This invention uses fly ash-based solid waste active powder as the main component, and constructs a dual-activation system with silicate and sulfate clinker: silicate provides an alkaline calcium environment, while sulfate synergistically activates solid waste hydration with desulfurized gypsum and carbide slag, forming a C-S-H, C-A-S-H, ettringite, and micro-filled composite structure. This effectively reduces clinker content, improves solid waste utilization, and enhances the early and late-stage strength and stability of low-clinker cement.

Description

Technical Field

[0001] This invention belongs to the field of cement preparation technology, specifically relating to a low-carbon, low-clinker cement based on a dual-excitation system and its preparation method. Background Technology

[0002] Cement-based materials are widely used in building construction, road engineering, precast components, and infrastructure development. Traditional silicate cement is mainly produced by high-temperature calcination of raw materials such as limestone and clay to form clinker, which is then ground together with components such as gypsum. Although its technology is mature and its performance is stable, the clinker production process is energy-intensive and accompanied by significant carbon emissions. With the increasing demands for green building materials and the resource utilization of industrial solid waste, reducing the amount of cement clinker used and increasing the utilization ratio of industrial solid waste in cementitious materials have become important development directions in the cement materials field.

[0003] Industrial solid wastes such as fly ash, slag, carbide slag, desulfurized gypsum, and lithium slag contain certain amounts of silicon, aluminum, calcium, and sulfur, possessing potential value as raw materials or auxiliary components for cementitious materials. Fly ash can provide a source of aluminosilicate activity, slag has potential hydraulic properties, carbide slag can serve as a calcium source and alkaline regulating component, desulfurized gypsum can provide sulfate, and lithium slag can supplement aluminosilicate activity. Using these solid wastes in low-clinker cement systems is beneficial for reducing clinker consumption and improving the resource utilization level of solid waste. However, existing high-solid-waste-content cementitious materials still have certain shortcomings. The activity release of solid waste materials such as fly ash is relatively slow; when they replace cement or clinker in a high proportion, problems such as insufficient early strength, delayed setting and hardening process, and unstable later-stage strength development can easily occur. Different solid waste raw materials have significant differences in chemical composition, particle morphology, grindability, and reactivity. If only simple mixing or ordinary co-grinding methods are used, it is easy to lead to uneven component distribution, unreasonable powder gradation, insufficient activation of solid waste powder, or excessive refinement of clinker components, which in turn affects the workability of slurry, strength development, and system stability.

[0004] Some existing technologies promote solid waste reactions by adding alkali activators, sulfate activators, or other chemical admixtures. However, these methods may suffer from high costs, difficulty in controlling alkali content, insufficient construction adaptability, and limited compatibility with conventional cement concrete systems. For low-clinker cement, relying solely on a small amount of silicate clinker to provide the hydration environment is insufficient to fully activate high-proportion solid waste powders; simply increasing the sulfate component may lead to uncoordinated hydration reactions or fluctuations in setting properties. Therefore, how to improve the cementitious contribution of solid waste powders while considering early strength, later strength, workability, and stability under lower clinker dosage conditions through reasonable solid waste activation, dual-activation system construction, and powder gradation control remains a key technical problem to be solved in the preparation of low-carbon, low-clinker cement. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a low-carbon, low-clinker cement based on a dual-activation system and its preparation method. Using physically activated fly ash-based composite solid waste active powder as the main cementitious component, silicate clinker and sulfate-activated clinker are introduced under conditions of low clinker dosage to construct a "silicate-sulfate" dual-activation system. Silicate clinker provides early silicate hydration products and an alkaline calcium environment. Sulfate-activated clinker, in combination with desulfurized gypsum, carbide slag, and other components, forms sulfate-activated reaction conditions, allowing solid waste components such as fly ash, water slag, and lithium slag to further participate in the hydration reaction based on micro-filling and nucleation effects. This forms a composite cementitious system composed of CSH gel, CASH gel, ettringite, and a micro-particle filling structure. This improves the early strength, later strength development, and system stability of low-clinker cement while reducing clinker dosage and increasing the utilization rate of solid waste.

[0006] The technical effects described in this invention are achieved through the following technical solutions: The first aspect of the present invention is to provide a low-carbon, low-clinker cement based on a dual-activation system, which, by dry weight, comprises the following raw materials: 38-52 parts fly ash, 15-25 parts water slag, 5-10 parts carbide slag, 5-10 parts desulfurized gypsum, 3-10 parts lithium slag, 8-18 parts silicate clinker, 5-12 parts sulfate activated clinker, and 0.05-0.3 parts grinding aid.

[0007] Preferably, the fly ash serves as the main aluminosilicate component, providing a source of active SiO2 and Al2O3; the slag serves as a potential hydraulic active component, participating in the hydration reaction under alkaline calcium conditions; and the carbide slag serves as a calcium source and alkalinity regulating component, supplementing the calcium content. 2+ It also increases the alkalinity of the system; the desulfurized gypsum, as a sulfate adjusting component, is used to provide SO4. 2- The lithium slag serves as a supplementary component for aluminum-silicon activity, used in conjunction with fly ash and water slag to form a composite aluminum-silicon active system. Preferably, the total SiO2 and Al2O3 content in the fly ash is not less than 50 wt%, and the loss on ignition is not more than 8 wt%; the water slag is granulated blast furnace slag powder or water-quenched slag, and the total CaO, SiO2, and Al2O3 content is not less than 70 wt%; the Ca(OH)2 content in the carbide slag is not less than 60 wt%; the CaSO4·2H2O content in the desulfurized gypsum is not less than 70 wt%; and the total SiO2 and Al2O3 content in the lithium slag is not less than 50 wt%. Preferably, the silicate clinker is ordinary silicate cement clinker, which is used to provide silicate mineral phases such as tricalcium silicate and dicalcium silicate, and to form silicate hydration products and an alkaline calcium environment during the hydration process; Preferably, the sulfate-activated clinker is sulfoaluminate cement clinker; the sulfoaluminate cement clinker contains a calcium sulfoaluminate mineral phase to provide the aluminate reaction phase, and reacts with SO4 provided by desulfurization gypsum. 2- and Ca in the system 2+ Together, they promote the formation of the ettringite framework in the early stages of hydration. It is understood that, provided that the aluminate reaction phase can be provided and the conditions for forming a sulfate-activated reaction with the desulfurized gypsum are met, the sulfate-activated clinker can also be a sulfoaluminate clinker containing a calcium sulfoaluminate mineral phase. Preferably, the grinding aid is selected from one or more of triethanolamine, triisopropanolamine, ethylene glycol, diethylene glycol, propylene glycol, glycerin, lignin sulfonate grinding aids, and polycarboxylate grinding aids; Preferably, when the amount of each raw material is selected within the above-mentioned weight range, the mass ratio of silicate clinker to sulfate activated clinker must be 1:0.6 to 0.75, and the total amount of the two must account for 12 to 28 wt% of the total amount of low-carbon, low-clinker cement solid raw materials excluding grinding aids; so as to ensure that the material still has stable early hydration reaction and later strength development ability while reducing the amount of clinker. A second aspect of the present invention is to provide a method for preparing low-carbon, low-clinker cement based on a dual-excitation system, comprising the following steps: S1: Fly ash, water slag, carbide slag, desulfurized gypsum and lithium slag are dried, cleaned and screened to obtain pretreated fly ash, water slag, carbide slag, desulfurized gypsum and lithium slag; and the pretreated desulfurized gypsum is divided into first desulfurized gypsum and second desulfurized gypsum. S2: Weigh the pretreated fly ash, water slag, carbide slag, lithium slag and first desulfurization gypsum according to the proportion, add some grinding aid and then mix, grind and classify to obtain fly ash-based composite solid waste active powder. S3: Silicate clinker, sulfate activated clinker, and second desulfurized gypsum are mixed in proportion, and the remaining grinding aid is added for joint grinding and classification to obtain a dual-activated clinker component; S4: Cool the fly ash-based composite solid waste active powder obtained in step S2 and the dual-activated clinker component obtained in step S3 to no higher than 45°C, then mix them in proportion and perform secondary homogenization to obtain low-carbon, low-clinker cement. Preferably, in step S1, the drying temperature of the fly ash, water slag, carbide slag and lithium slag is 50-80℃; the drying temperature of the desulfurized gypsum is 40-55℃. Preferably, in step S1, the moisture content of each solid waste raw material after drying is controlled to be ≤2.5%; wherein, the desulfurized gypsum is divided into first desulfurized gypsum and second desulfurized gypsum in subsequent steps; the first desulfurized gypsum is used to prepare fly ash-based composite solid waste active powder, and the second desulfurized gypsum is used to prepare dual-activated clinker components; Preferably, the first desulfurized gypsum accounts for 25-45% of the total mass of the desulfurized gypsum, and the second desulfurized gypsum accounts for 55-75% of the total mass of the desulfurized gypsum; Preferably, in step S2, the specific surface area of ​​the fly ash-based composite solid waste active powder is 850–950 m². 2 / kg; This step can improve the surface activity of fly ash, water slag and lithium slag, increase particle surface defects and nucleation sites, and make carbide slag and first desulfurization gypsum uniformly distributed in the composite powder, thereby providing calcium source, alkaline environment and partial sulfate adjustment conditions for subsequent hydration reaction. Preferably, in steps S2 and S3, the grinding is carried out using a ball mill, vertical mill, vibratory mill, or air jet mill; after grinding, the powder is classified by a dynamic classifier or air jet classifier so that the obtained powder meets the corresponding specific surface area requirements. Preferably, in step S3, the specific surface area of ​​the dual-activated clinker component is 450–650 m². 2 / kg; In step S3, silicate clinker is used to provide silicate hydration products and an alkaline calcium environment, while sulfate-activated clinker is used to provide the aluminate reaction phase, and reacts with SO4 provided by the second desulfurization gypsum. 2- and Ca in the system 2+ The combined effect enables the formation of an ettringite framework in the early stages of hydration and promotes further reaction of the aluminum and silicon components in the fly ash-based composite solid waste active powder. Preferably, the grinding aid is added in two steps; based on the total mass of the grinding aid, 60-70 wt% of the grinding aid is added in step S2, and 30-40 wt% of the grinding aid is added in step S3; by allowing a higher proportion of the grinding aid to participate in the refining process of fly ash-based composite solid waste active powder, the dispersion and refining efficiency of fly ash, water slag, and lithium slag can be improved; by allowing a lower proportion of the grinding aid to participate in the grinding process of dual-activated clinker components, excessive refining of clinker components can be avoided, which could lead to increased water demand or excessively rapid coagulation. Preferably, in step S4, the specific operation of the secondary homogenization is as follows: in a twin-shaft zero-gravity mixer, the material temperature is controlled not to exceed 45°C, and dry mixing is performed at a speed of 35-55 rpm for 8-15 minutes; then the mixture is sent into a pneumatic homogenization chamber and homogenized with dry compressed air at 0.05-0.15 MPa for 6-12 minutes. Preferably, in step S4, after secondary homogenization, samples are taken from the upper, middle, and lower parts of the finished material and from different discharge times, and the difference in 45μm sieve residue between any two sampling points is no more than 2 percentage points. Preferably, in step S4, the specific surface area of ​​the final cement product is not less than 550 m². 2 / kg, with a residue of no more than 10% on a 45μm sieve.

[0008] The beneficial effects of this invention are as follows: This invention uses fly ash, water slag, carbide slag, desulfurized gypsum, and lithium slag to form a fly ash-based composite solid waste system, and incorporates silicate clinker and sulfate-activated clinker to construct a dual-activated reaction system. Unlike ordinary solid waste admixtures that simply replace cement, this invention, through pretreatment, segmented grinding, and specific surface area control of the solid waste components, enables the aluminum and silicon active components in fly ash, water slag, and lithium slag to participate more fully in the hydration reaction under conditions of lower clinker dosage. Fly ash and lithium slag provide sources of active SiO2 and Al2O3, water slag can exert potential hydraulic reactions in an alkaline calcium environment, carbide slag can supplement the calcium source and adjust the alkalinity of the system, and desulfurized gypsum can provide sulfate ions and participate in the formation of early hydration products. This is beneficial for improving the reactivity and cementing contribution of high-proportion solid waste powders in a low-clinker system.

[0009] This invention divides desulfurized gypsum into two parts, a first desulfurized gypsum and a second desulfurized gypsum, which are added at different grinding stages. The first desulfurized gypsum is ground together with fly ash, water slag, carbide slag, and lithium slag. This improves the dispersion uniformity of sulfate regulating components in the composite solid waste active powder and allows for a closer spatial contact between the calcium source provided by the carbide slag, the sulfate provided by the desulfurized gypsum, and the fly ash-based aluminum-silicon components. The second desulfurized gypsum is ground together with silicate clinker and sulfate-activated clinker. This improves the contact efficiency between the sulfate components and the clinker mineral phases, making it easier for them to participate in the formation of early hydration products such as ettringite in the early stages of hydration. This segmented configuration avoids problems such as uneven sulfate distribution, insufficient early reaction, or excessively rapid local reaction caused by adding desulfurized gypsum alone, thus improving the hydration coordination of low-clinker cement systems.

[0010] In this invention, silicate clinker provides silicate hydration products and an alkaline calcium environment, while sulfate-activated clinker provides the aluminate reaction phase and, together with desulfurized gypsum, carbide slag, and other components, constitutes the sulfate-activated reaction conditions. The CSH gel formed by silicate clinker hydration and the alkaline calcium environment promote the gradual dissolution of active aluminum-silicon components from fly ash, slag, and lithium slag; the sulfate-activated clinker and the SO4 provided by desulfurized gypsum... 2- and Ca in the system 2+ Together, they promote the early formation of the ettringite framework. Their synergistic effect can reduce clinker usage while simultaneously ensuring both early strength development and later strength growth.

[0011] This invention grinds fly ash-based composite solid waste active powder to a high specific surface area, giving it good filling effect, nucleation effect, and potential reactivity. Simultaneously, it controls the dual-activated clinker components within a relatively moderate specific surface area range, allowing the clinker components to maintain a relatively stable hydration release rate and reducing the risk of increased water demand, excessively rapid setting, or decreased slurry fluidity due to over-refining of all materials. By creating differentiated fineness control between the fly ash-based composite solid waste active powder and the dual-activated clinker components, the fine solid waste powder facilitates filling the interparticle pores and provides nucleation sites for hydration product deposition, thereby improving slurry packing density and enhancing the fluidity, construction adaptability, and molding stability of cement slurry and concrete mixtures. Through batch addition of grinding aids, a higher proportion of the grinding aid participates in the refining process of the fly ash-based composite solid waste active powder, improving the dispersion and grinding efficiency of fly ash, water slag, and lithium slag; while a lower proportion of the grinding aid participates in the grinding process of the dual-activated clinker components, thus controlling the degree of refinement of the clinker components. This grinding aid distribution method helps to improve the activity of solid waste powder while reducing the risk of increased water demand and difficulty in coagulation control caused by excessive grinding of clinker components, thus maintaining a good balance between the degree of solid waste activation, clinker hydration rate and slurry rheological properties.

[0012] Furthermore, this invention employs a two-stage homogenization process combining biaxial gravity-free mixing and pneumatic homogenization, resulting in a more uniform distribution of fly ash-based composite solid waste active powder and dual-activated clinker components in the finished cement. This helps reduce fineness differences and component fluctuations between different batches or sampling locations. A more uniform powder distribution improves the reaction consistency of the dual-activated system during hydration, reducing localized sulfate excess, insufficient calcium source, or delayed solid waste powder reaction, thus contributing to more stable setting properties, strength development, and volume stability. Attached Figure Description

[0013] Figure 1 The following are the 72-hour hydration heat curves for cement samples used in the examples and comparative examples. Figure 1 a represents the hydration heat release rate curve over 72 hours. Figure 1 b represents the cumulative heat release curve over 72 hours; Figure 2 The XRD patterns of cement samples after 28 days of hydration are shown for the examples and comparative examples. Detailed Implementation

[0014] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Unless otherwise specified, the raw materials involved in the present invention are purchased through conventional commercial channels. Experimental methods without specific conditions are conventional methods and conditions well known in the art, or according to the conditions recommended by the instrument manufacturer.

[0015] Example 1: A low-carbon, low-clinker cement based on a dual-excitation system, which, by dry weight, comprises the following raw materials: 45 parts fly ash, 20 parts water slag, 7 parts carbide slag, 8 parts desulfurized gypsum, 6 parts lithium slag, 12 parts ordinary silicate cement clinker, 8 parts sulfoaluminate cement clinker, and 0.15 parts triethanolamine.

[0016] The preparation of the low-carbon, low-clinker cement of the dual-activation system includes the following steps: S1: Fly ash, water slag, carbide slag, and lithium slag are dried at 65℃, and desulfurized gypsum is dried at 50℃. Then, impurities are removed and the mixture is screened to obtain pretreated fly ash, water slag, carbide slag, desulfurized gypsum, and lithium slag with a moisture content of ≤2.5%. The pretreated desulfurized gypsum is then divided into first desulfurized gypsum and second desulfurized gypsum. S2: Weigh out pretreated fly ash, water slag, carbide slag, lithium slag, and 35% of the total mass of desulfurized gypsum according to the specified proportions. Add 65 wt% of triethanolamine (the total mass of grinding aid) and then mix and grind in a ball mill and classify using an air classifier to obtain a specific surface area of ​​950 m². 2 / kg of fly ash-based composite solid waste active powder; S3: Ordinary silicate cement clinker, sulfoaluminate cement clinker, and 65% of the total mass of desulfurized gypsum (secondary desulfurized gypsum) are mixed in a certain proportion, and the remaining 35 wt% of triethanolamine is added. The mixture is then subjected to ball milling and air classifier treatment to obtain a product with a specific surface area of ​​550 m² / g. 2 / kg of dual-activated clinker components; S4: After cooling the fly ash-based composite solid waste active powder obtained in step S2 and the dual-activated clinker components obtained in step S3 to no higher than 45°C, they are mixed in proportion and dry-mixed for 12 minutes at a speed of 45 rpm in a twin-shaft gravity-free mixer, with the material temperature controlled to be no higher than 45°C. Then the mixture is sent to an air homogenization chamber and homogenized with dry compressed air at 0.1 MPa for 10 minutes to obtain low-carbon, low-clinker cement. The specific surface area of ​​the final cement product shall not be less than 550 m². 2 / kg, with a residue of no more than 10% on a 45μm sieve.

[0017] Example 2: A low-carbon, low-clinker cement based on a dual-excitation system, which, by dry weight, comprises the following raw materials: 38 parts fly ash, 15 parts water slag, 5 parts carbide slag, 5 parts desulfurized gypsum, 3 parts lithium slag, 8 parts ordinary silicate cement clinker, 5 parts sulfoaluminate cement clinker, and 0.05 parts triisopropanolamine.

[0018] The preparation of the low-carbon, low-clinker cement of the dual-activation system includes the following steps: S1: Fly ash, water slag, carbide slag, and lithium slag are dried at 50℃, and desulfurized gypsum is dried at 40℃. Then, impurities are removed and the mixture is screened to obtain pretreated fly ash, water slag, carbide slag, desulfurized gypsum, and lithium slag with a moisture content of ≤2.5%. The pretreated desulfurized gypsum is then divided into first desulfurized gypsum and second desulfurized gypsum. S2: Weigh out pretreated fly ash, water slag, carbide slag, lithium slag, and 25% of the total mass of desulfurized gypsum according to the specified proportions. Add 60 wt% of triisopropanolamine (the total mass of the grinding aid) and then mix and grind in a vertical mill and classify using an air classifier to obtain a product with a specific surface area of ​​850 m². 2 / kg of fly ash-based composite solid waste active powder; S3: Ordinary silicate cement clinker, sulfoaluminate cement clinker, and 75% of the total mass of desulfurized gypsum (secondary desulfurized gypsum) are mixed in a certain proportion, and the remaining 40 wt% of triisopropanolamine is added. The mixture is then subjected to combined grinding in a vertical mill and classification using an air classifier to obtain a product with a specific surface area of ​​650 m² / g. 2 / kg of dual-activated clinker components; S4: After cooling the fly ash-based composite solid waste active powder obtained in step S2 and the dual-activated clinker components obtained in step S3 to no higher than 45°C, they are mixed in proportion and dry-mixed for 15 minutes at a speed of 35 rpm in a twin-shaft gravity-free mixer, with the material temperature controlled to be no higher than 45°C. Then, the mixture is sent to an air homogenization chamber and homogenized with dry compressed air at 0.05 MPa for 12 minutes to obtain low-carbon, low-clinker cement. The specific surface area of ​​the final cement product shall not be less than 550 m². 2 / kg, with a residue of no more than 10% on a 45μm sieve.

[0019] Example 3: A low-carbon, low-clinker cement based on a dual-excitation system, which, by dry weight, comprises the following raw materials: 52 parts fly ash, 25 parts water slag, 10 parts carbide slag, 10 parts desulfurized gypsum, 10 parts lithium slag, 18 parts ordinary silicate cement clinker, 12 parts sulfoaluminate cement clinker, and 0.3 parts propylene glycol.

[0020] The preparation of the low-carbon, low-clinker cement of the dual-activation system includes the following steps: S1: Fly ash, water slag, carbide slag, and lithium slag are dried at 80℃, and desulfurized gypsum is dried at 55℃. Then, impurities are removed and the mixture is screened to obtain pretreated fly ash, water slag, carbide slag, desulfurized gypsum, and lithium slag with a moisture content of ≤2.5%. The pretreated desulfurized gypsum is then divided into first desulfurized gypsum and second desulfurized gypsum. S2: Weigh out pretreated fly ash, water slag, carbide slag, lithium slag, and 45% of the total mass of desulfurized gypsum according to the specified proportions. Add 70 wt% of propylene glycol (the total mass of the grinding aid) and then mix and grind in a ball mill and classify using an air classifier to obtain a specific surface area of ​​950 m². 2 / kg of fly ash-based composite solid waste active powder; S3: Ordinary silicate cement clinker, sulfoaluminate cement clinker, and 55% (by weight of) secondary desulfurized gypsum are mixed in a specific ratio. The remaining 30 wt% propylene glycol is added, and the mixture is then subjected to ball milling and air classifier treatment to obtain a product with a specific surface area of ​​450 m². 2 / kg of dual-activated clinker components; S4: After cooling the fly ash-based composite solid waste active powder obtained in step S2 and the dual-activated clinker component obtained in step S3 to no higher than 45°C, they are mixed in proportion and dry-mixed for 8 minutes at a speed of 55 rpm in a twin-shaft gravity-free mixer, with the material temperature controlled to be no higher than 45°C. Then the mixture is sent to an air homogenization chamber and homogenized with dry compressed air at 0.15 MPa for 6 minutes to obtain low-carbon, low-clinker cement. The specific surface area of ​​the final cement product shall not be less than 550 m². 2 / kg, with a residue of no more than 10% on a 45μm sieve.

[0021] Comparative Example 1: Sulfate-activated clinker was removed and replaced with an equal mass of silicate clinker; the remaining raw material composition and steps were consistent with those in Example 1.

[0022] Comparative Example 2: The segmented grinding process was cancelled and replaced with a one-time common grinding. Instead of preparing fly ash-based composite solid waste active powder and dual-activated clinker components separately, fly ash, water slag, carbide slag, desulfurized gypsum, lithium slag, silicate clinker, sulfate activated clinker and grinding aid were added to the grinding equipment at one time for common grinding. After grinding, the mixture was homogenized to obtain low-carbon, low-clinker cement. The composition and steps of the remaining raw materials were consistent with those of Example 1.

[0023] Comparative Example 3: The desulfurized gypsum was not added in stages, but all of the desulfurized gypsum was added to step S3; the composition and steps of the remaining raw materials were consistent with those of Example 1.

[0024] Comparative Example 4: The mass ratio of silicate clinker to sulfate activated clinker was changed, with 15 parts of silicate clinker and 5 parts of sulfate activated clinker, while keeping the total amount of silicate clinker and sulfate activated clinker at 20 parts, consistent with Example 1; the composition of other raw materials and steps were consistent with Example 1.

[0025] Comparative Example 5: The total amount of silicate clinker and sulfate activated clinker was reduced, and the silicate clinker was adjusted to 6 parts and the sulfate activated clinker to 4 parts. The mass ratio of the two was kept the same as in Example 1. The 10 parts that were reduced were made up by composite solid waste active powder obtained by pre-grinding fly ash, water slag, carbide slag and lithium slag in the same mass ratio as in Example 1. The total amount of desulfurized gypsum and the distribution ratio of the first desulfurized gypsum and the second desulfurized gypsum were kept the same as in Example 1. The composition of other raw materials and steps were kept the same as in Example 1.

[0026] Comparative Example 6: The specific surface area of ​​the fly ash-based composite solid waste active powder in step S2 was controlled to be 600 m². 2 / kg, to make its fineness close to that of the dual-excitation clinker component obtained in step S3; the composition and steps of the remaining raw materials are consistent with those of Example 1.

[0027] Performance Testing: To verify the improved effects of the low-carbon, low-clinker cement based on the dual-excitation system of this invention on powder gradation control, construction adaptability, setting stability, early strength, later strength, hydration reaction coordination, and hydration product formation, the basic properties of the finished powder, mortar fluidity, standard consistency water requirement, setting time, soundness, mortar strength, heat of hydration, and XRD hydration products of the low-carbon, low-clinker cement obtained in the examples and comparative examples were tested. All samples were prepared using the same batch of raw materials. After being sealed and packaged, the finished cement was equilibrated at 20±2℃ for 24 hours before testing. Unless otherwise specified, each basic performance test was performed in triplicate, and the results were averaged.

[0028] To evaluate the effects of different preparation methods on the state and homogenization effect of the finished cement powder, cement samples obtained in Examples 1-3 and Comparative Examples 1-6 were tested for specific surface area, particle size distribution, 45μm sieve residue, and uniformity. Specific surface area was determined using the Blaine method according to GB / T 8074-2008; 45μm sieve residue was determined using the sieve analysis method according to GB / T 1345-2005; particle size distribution was determined using a laser particle size analyzer. Before particle size testing, the samples were dried in a vacuum drying oven at 40±2℃ for 2 hours, cooled to room temperature, and then tested using a dry dispersion method with a dispersion pressure controlled at 0.30MPa. The particle size distribution was recorded. 50 and D 90 To evaluate the effect of secondary homogenization, samples were taken from the upper, middle, and lower parts of the finished material, as well as at different discharge stages. The residue on a 45μm sieve at each sampling point was measured, and the maximum difference in residue on a 45μm sieve between different sampling points was calculated. The test results are shown in Table 1.

[0029] To evaluate the construction adaptability and setting stability of the low-carbon, low-clinker cement of this invention, samples obtained from Examples 1-3 and Comparative Examples 1-6 were tested for standard consistency water requirement, setting time, soundness, and mortar flowability. Standard consistency water requirement, initial setting time, final setting time, and soundness were tested according to GB / T 1346-2024; mortar flowability was tested according to GB / T2419-2005. In the mortar flowability test, the masses of the cement sample, ISO standard sand, and water were 450g, 1350g, and 225g, respectively, i.e., a fixed water-cement ratio of 0.5. Mixing, molding, table vibration, and expansion diameter measurement were performed under the same operating conditions. This test was used to evaluate the effects of different clinker ratios, desulfurized gypsum addition methods, segmented grinding methods, and particle size distributions on the water requirement, setting process, volume soundness, and mortar flowability of the cement system. The test results are shown in Table 2.

[0030] To evaluate the early and later strength development of the low-carbon, low-clinker cement of this invention, samples from Examples 1-3 and Comparative Examples 1-6 were subjected to cement mortar strength tests. The tests were conducted according to GB / T 17671-2021. Mortar specimens were 40mm × 40mm × 160mm prisms. The masses of cement sample, ISO standard sand, and water were 450g, 1350g, and 225g, respectively, i.e., the mass ratio of cementitious material to sand was 1:3, and the water-cement ratio was 0.5. After molding, the specimens were cured in a curing chamber at 20±1℃ and a relative humidity of not less than 90% for 24 hours. After demolding, they were placed in water at 20±1℃ and cured to the specified age. The compressive strength test ages were set at 3d, 7d, 28d, and 56d, and the flexural strength test ages were set at 3d and 28d. Table 3 records the 3d flexural strength, 28d flexural strength, 3d compressive strength, 7d compressive strength, 28d compressive strength, and 56d compressive strength of Examples 1-3 and Comparative Examples 1-6.

[0031] To further evaluate the effects of the dual-excitation system and segmented grinding method on the early hydration reaction process, isothermal hydration heat tests were conducted on Example 1 and Comparative Examples 1, 2, 3, and 5. The tests were performed according to the method for determining the heat of hydration of cement in GB / T 12959-2024. Specifically, 20g of cement sample from each group was weighed, and 10g of deionized water was added, with a water-cement ratio fixed at 0.5. The mixture was stirred at low speed for 60s using a cement paste mixer, stopped for 15s to scrape the sides, and then stirred at low speed for another 60s. The cement paste was then immediately poured into calorimetric ampoules and sealed. The test temperature was controlled at 20±0.1℃, and the hydration heat release rate and cumulative heat release were continuously recorded for 72 hours. The test results are shown below. Figure 1 ,in Figure 1 a represents the hydration heat release rate curve over 72 hours. Figure 1 b represents the cumulative heat release curve over 72 hours.

[0032] To evaluate the effects of different treatment methods on the composition of hydration products, XRD tests were conducted on 28-day hydration samples from Examples 1, 1, 2, 3, and 6. Specifically, 100g of each cement sample was weighed, 50g of deionized water was added, the water-cement ratio was fixed at 0.5, and the mixture was stirred thoroughly before being placed in a sealed mold. The mold was then cured for 24 hours at 20±2℃ and a relative humidity of not less than 95%. After demolding, the samples were sealed and cured for another 28 days. Upon reaching the required curing age, samples were taken, broken to less than 5mm, and representative fragments were immediately immersed in anhydrous ethanol to terminate hydration for 24 hours. Subsequently, the samples were dried in a vacuum drying oven at 40℃ for 24 hours (to avoid high temperature damage to particle morphology or initiation of hydration reactions), ground, and sieved through a 75μm sieve. The powder passing through the sieve was then used for XRD analysis. XRD testing was performed using Cu Kα rays at a tube voltage of 40 kV and a tube current of 40 mA. The scanning range was 5°–70° with a step size of 0.02° and a scanning speed of 5° / min. The test results are shown below. Figure 2 .

[0033] Table 1. Test results of basic powder properties of cement samples from the examples and comparative examples

[0034] Table 2. Test results of workability and setting stability of cement samples from the examples and comparative examples.

[0035] Table 3. Mortar strength test results of cement samples from the examples and comparative examples

[0036] From Tables 1-3 and Figures 1-2 It is evident that the overall performance of the embodiments is superior to that of the comparative examples. This is because the present invention does not rely solely on increasing the fineness of grinding or increasing the amount of clinker, but rather on the synergistic effect between fly ash-based composite solid waste active powder, silicate clinker, sulfate-activated clinker, desulfurized gypsum and carbide slag, enabling the low clinker system to simultaneously possess the functions of early skeleton formation, later gel filling and powder gradation optimization.

[0037] Based on the results in Tables 1-3, Example 1 exhibits better overall performance, primarily due to its use of a relatively balanced silicate-sulfate dual-excitation system. The silicate clinker, upon hydration, releases Ca... 2+ and OH -This provides an alkaline calcium environment for the glassy phase aluminosilicate components in fly ash, slag, and lithium slag. The SO4²⁻ provided by sulfoaluminate cement clinker and the calcium source provided by desulfurized gypsum, along with the calcium source from carbide slag, promote early AFt skeleton formation. Early AFt facilitates rapid establishment of the spatial skeleton, while CSH and CASH gels further fill pores and enhance matrix density during subsequent hydration. Therefore, Example 1 can balance early and later strength development. Example 2 exhibits a milder overall strength activation, with weaker activation of solid waste powder and clinker than Example 1, resulting in a relatively slower hydration structure establishment. However, due to the gentler reaction rhythm, it offers better construction fluidity. In Example 3, the solid waste powder has a higher activation level, and the amounts of sulfoaluminate clinker and silicate clinker are higher, leading to faster hydration and higher strength. However, its higher proportion of fine powder and stronger activation components increase water demand and shorten the construction window.

[0038] In Comparative Example 1, although the system could still form a certain CSH gel and alkaline calcium environment by relying on silicate clinker after the sulfate activation was removed, there was a lack of sufficient aluminate mineral phases to participate in the sulfate reaction, resulting in insufficient early AFt framework formation. This led to a decrease in the early structure establishment rate and weakened the promoting effect of sulfate activation on the dissolution and reaction of solid waste aluminum-silicon components. Therefore, its hydration heat peak, AFt characteristics, and intensity development were all lower than those of Example 1, indicating that single silicate activation is insufficient to fully support a high solid waste, low clinker system. Comparative Example 2 used a one-time co-grinding process. The grindability of different raw materials varied greatly, and one-time grinding easily caused insufficient activation of some solid waste components. At the same time, the particle size distribution and reaction release rate of clinker components were difficult to control. Solid waste powder could not provide sufficient nucleation sites and micro-filling effects, and clinker components could not form a stable spatial contact relationship with desulfurized gypsum and carbide slag. Therefore, the coordination of hydration reaction decreased, and the formation of C-(A)-SH gel and pore filling effects were insufficient. In Comparative Example 3, all desulfurized gypsum was added to the dual-activation clinker components, resulting in the sulfate regulating components mainly concentrated on the clinker side, while the fly ash-based composite solid waste active powder lacked a pre-dispersed sulfate source. This consequently affected SO4 levels. 2- Ca 2+The spatial contact between the gypsum and aluminum-silicon active components makes the sulfate reaction more likely to concentrate locally, and some gypsum cannot fully participate in the early AFt formation. As a result, although the early reaction can still occur, the distribution and structural uniformity of the hydration products are not as good as in Example 1, and the volume stability and strength development are affected to some extent. Comparative Example 4 kept the total amount of dual-activated clinker unchanged, but changed the ratio of silicate clinker to sulfate-activated clinker, making the sulfate-activated component relatively insufficient. This shows that when the sulfate-activated clinker is too low, the AFt formation channel is insufficient, and the early framework establishment and further reaction of aluminum-silicon components are limited; when the proportion of silicate clinker is too high, the system is more like ordinary silicate hydration, and it is difficult to fully reflect the synergistic effect of sulfate activation on the high solid waste system. After reducing the total amount of dual-activated clinker in Comparative Example 5, even with a high powder specific surface area, the corresponding strength improvement could not be obtained, indicating that powder refinement cannot replace the necessary chemical activation conditions. Insufficient total clinker will lead to Ca 2+ OH - In Comparative Example 6, the reaction conditions for aluminate mineral phases and sulfates were insufficient, making it difficult for the active components in fly ash, slag, and lithium slag to fully dissolve and participate in gel formation. This resulted in insufficient hydration driving force, a delayed main exothermic peak, reduced cumulative heat release, and limited strength development. After eliminating differentiated particle size control in Comparative Example 6, the fly ash-based composite solid waste powder failed to achieve sufficient ultrafine processing, leading to insufficient surface defects, nucleation sites, and micro-filling. When the solid waste powder was not sufficiently refined, its particle distribution was coarse, with reduced specific surface area and nucleation interface. The initiation of pozzolanic reaction and potential hydraulic reaction was slow, failing to effectively fill the pores between clinker particles and hydration products, and failing to provide sufficient nucleation interfaces for CSH, CASH, and AFt deposition. Therefore, even with the dual-excitation system still present, its hydration product generation efficiency and structural densification were significantly weaker than in Example 1.

[0039] Figure 1 The hydration heat results further illustrate that the performance differences among the groups mainly stem from variations in the early hydration reaction rate and degree. In Example 1, the coordinated action of silicate hydration, sulfate activation, and solid waste powder activation resulted in a more concentrated main exothermic peak and a higher cumulative heat release. Conversely, eliminating sulfate activation, eliminating segmented grinding, not segmenting desulfurized gypsum, or reducing the total clinker volume all weakened the early hydration driving force or delayed the reaction process to varying degrees. The changes in hydration heat corresponded to the strength results, indicating that the formation rate of early hydration products directly affects the subsequent mechanical property development.

[0040] Figure 2The XRD results further confirmed the above mechanism from the perspective of hydration products. In Example 1, the correlation characteristics of AFt and C-(A)-SH were more obvious, indicating that early skeleton products and later gel products were formed together; in Comparative Example 1, AFt was insufficient, reflecting the lack of sulfate activation channels; in Comparative Examples 2 and 6, clinker residues were more obvious, indicating that insufficient powder activation and particle size distribution would reduce the reaction utilization rate of clinker and solid waste components; in Comparative Example 3, residual gypsum was more prominent, indicating that the concentrated addition of desulfurized gypsum was not conducive to the full conversion of sulfate components. It can be seen that the main reason for the performance improvement is that the present invention, through the division of raw materials and process segmentation, enables the synergistic formation of AFt, CSH, CASH and fine particle filling structure.

[0041] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A low-carbon, low-clinker cement based on a dual-excitation system, characterized in that, Based on dry weight, its composition includes the following raw materials: 38-52 parts fly ash, 15-25 parts water slag, 5-10 parts calcium carbide slag, 5-10 parts desulfurized gypsum, 3-10 parts lithium slag, 8-18 parts silicate clinker, 5-12 parts sulfate activated clinker, and 0.05-0.3 parts grinding aid. The sulfate-activated clinker is a sulfoaluminate clinker containing calcium sulfoaluminate mineral phase; The mass ratio of silicate clinker to sulfate activated clinker is 1:0.6 to 0.75, and the total amount of silicate clinker and sulfate activated clinker accounts for 12 to 28 wt% of the total mass of low-carbon, low-clinker cement solids excluding grinding aids.

2. The low-carbon, low-clinker cement based on a dual-excitation system according to claim 1, characterized in that, The fly ash contains a total SiO2 and Al2O3 content of not less than 50 wt% and a loss on ignition of not more than 8 wt%; the slag is granulated blast furnace slag powder or water-quenched slag, with a total CaO, SiO2 and Al2O3 content of not less than 70 wt%; the carbide slag contains a Ca(OH)2 content of not less than 60 wt%; the desulfurized gypsum contains a CaSO4·2H2O content of not less than 70 wt%; and the lithium slag contains a total SiO2 and Al2O3 content of not less than 50 wt%.

3. The low-carbon, low-clinker cement based on a dual-excitation system according to claim 1, characterized in that, The silicate clinker is ordinary silicate cement clinker, and the sulfate activated clinker is sulfoaluminate cement clinker.

4. The low-carbon, low-clinker cement based on a dual-excitation system according to claim 1, characterized in that, The grinding aid is selected from one or more of triethanolamine, triisopropanolamine, ethylene glycol, diethylene glycol, propylene glycol, glycerin, lignin sulfonate grinding aids, and polycarboxylate grinding aids.

5. A method for preparing low-carbon, low-clinker cement based on a dual-excitation system according to any one of claims 1-4, characterized in that, Includes the following steps: S1: Fly ash, water slag, carbide slag, desulfurized gypsum and lithium slag are dried, cleaned and screened to obtain pretreated fly ash, water slag, carbide slag, desulfurized gypsum and lithium slag; and the pretreated desulfurized gypsum is divided into first desulfurized gypsum and second desulfurized gypsum. S2: Weigh the pretreated fly ash, water slag, carbide slag, lithium slag and first desulfurization gypsum according to the proportion, add some grinding aid and then mix, grind and classify to obtain fly ash-based composite solid waste active powder. S3: Silicate clinker, sulfate activated clinker, and second desulfurized gypsum are mixed in proportion, and the remaining grinding aid is added for joint grinding and classification to obtain a dual-activated clinker component; S4: Mix the fly ash-based composite solid waste active powder obtained in step S2 with the dual-activated clinker components obtained in step S3 in a certain proportion, and perform secondary homogenization to obtain low-carbon, low-clinker cement.

6. A method for preparing low-carbon, low-clinker cement based on a dual-excitation system according to claim 5, characterized in that, In step S1, the drying temperature of the fly ash, water slag, carbide slag, and lithium slag is 50–80°C; the drying temperature of the desulfurized gypsum is 40–55°C; the moisture content of each solid waste raw material after drying is controlled to be ≤2.5%; the desulfurized gypsum is divided into first desulfurized gypsum and second desulfurized gypsum in subsequent steps; the first desulfurized gypsum accounts for 25–45% of the total mass of desulfurized gypsum, and the second desulfurized gypsum accounts for 55–75% of the total mass of desulfurized gypsum.

7. A method for preparing low-carbon, low-clinker cement based on a dual-excitation system according to claim 5, characterized in that, In step S2, the specific surface area of ​​the fly ash-based composite solid waste active powder is 850–950 m². 2 / kg.

8. A method for preparing low-carbon, low-clinker cement based on a dual-excitation system according to claim 5, characterized in that, In step S3, the specific surface area of ​​the dual-activated clinker component is 450-650 m² / kg.

9. A method for preparing low-carbon, low-clinker cement based on a dual-excitation system according to claim 5, characterized in that, The grinding aid is added in two steps: 60-70 wt% of the grinding aid is added in step S2 and 30-40 wt% of the grinding aid is added in step S3, based on the total mass of the grinding aid.

10. A method for preparing low-carbon, low-clinker cement based on a dual-excitation system according to claim 5, characterized in that, In step S4, the specific operation of the secondary homogenization is as follows: add the fly ash-based composite solid waste active powder and the dual-activated clinker components into a twin-shaft zero-gravity mixer, control the material temperature to be no higher than 45°C, and dry mix at a speed of 35-55 rpm for 8-15 minutes. The mixture is then fed into a pneumatic homogenization chamber and homogenized for 6–12 minutes with dry compressed air at 0.05–0.15 MPa.

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