Slag powder-fly ash cementing material with ferric silicate as excitant

Abstract

The invention discloses a slag powder-fly ash cementing material taking ferric silicate as an exciting agent, and belongs to the technical field of building materials. The cementing material consists of the following components in percentage by weight: 30-50% of slag powder, 2-15% of gypsum, 15-20% of fly ash, 10-15% of slag powder, 10-15% of limestone powder and 3-8% of iron silicate. The preparation method comprises the following steps: raw material pretreatment and grading, sectional energy optimization grinding and controllable hydration activation aging. Iron silicate and gypsum are utilized to form an acidic destruction-sulfate reconstruction composite excitation system, the activity of slag and fly ash is synergistically excited, and the problems that a traditional alkali-excited material is low in early strength, difficult in condensation behavior regulation and control, insufficient in durability and concentrated in hydration heat release are effectively solved. The obtained product has the characteristics of high early strength, good working performance, strong sulfate attack resistance and low hydration heat, and is suitable for high-performance green building materials and mass concrete engineering.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a slag powder-fly ash cementitious material using ferrosilicon as an activator. Background Technology

[0002] Slag and fly ash are typical industrial solid wastes, and their resource utilization has attracted much attention in the building materials industry. Traditionally, slag-fly ash-based polymers or cementitious materials are prepared using methods such as alkali activation or sulfate activation to achieve large-scale disposal and high-performance conversion of solid waste.

[0003] However, existing technologies still have certain limitations: commonly used strong alkali activators (such as sodium hydroxide, water glass, etc.) can effectively activate the activity of siliceous alumina raw materials, but they often lead to violent early hydration reactions, short setting time, poor construction adaptability, and are prone to later shrinkage cracking; while sulfate activators (such as gypsum) have limited early activation efficiency for slag when used alone, making it difficult to achieve the ideal strength development rate, especially with insufficient activation effect on fly ash, resulting in low early strength of the material.

[0004] Furthermore, the hydration products of traditional alkali-activated cementitious materials are mostly high-alkalinity systems, posing challenges to long-term durability; their hydration heat release is concentrated, easily leading to temperature stress cracks in large-volume concrete applications. Although existing technologies have attempted to improve performance by using multiple activators in combination or mechanical activation, it remains difficult to achieve an effective balance among multiple objectives such as early strength, workability, durability, and hydration heat control.

[0005] Therefore, there is an urgent need to develop a new activation system and supporting preparation process that can efficiently and synergistically activate the activity of slag and fly ash under mild conditions, overcome the technical bottlenecks in existing technologies such as slow early strength development, difficulty in controlling condensation behavior, and insufficient durability, while taking into account the characteristics of low heat and low environmental load, so as to meet the high performance and functional requirements of modern green building materials. Summary of the Invention

[0006] In view of this, the present invention aims to provide a slag powder-fly ash cementitious material with ferric silicate as an activator, so as to solve or alleviate the technical problems existing in the prior art.

[0007] The technical solution of this invention is implemented as follows: a slag powder-fly ash cementitious material using ferric silicate as an activator, composed of the following components by weight percentage: slag powder: 30-50%; gypsum: 2-15%; fly ash: 15-20%; slag powder: 10-15%; limestone powder: 10-15%; ferric silicate: 3-8%; The sum of the weight percentages of all components is 100%. In the above embodiments, the components are composed of the following weight percentages: slag powder: 40%; gypsum: 10%; fly ash: 19%; slag powder: 11%; limestone powder: 16%; and ferric silicate: 5%.

[0008] In the above embodiments, the slag powder is obtained by grinding granulated blast furnace slag, and its specific surface area is not less than 400 m². 2 / kg, density is 2.8-3.0 g / cm³ 3 .

[0009] In the above embodiments, the gypsum is any one or a combination of two of desulfurized gypsum and phosphogypsum, with a crystal water content of not less than 15% and an SO3 content of ≥35%.

[0010] In the above embodiments, the slag powder is obtained by grinding circulating fluidized bed boiler slag, and its total SiO2+Al2O3+Fe2O3 content is not less than 70%, and its moisture content is not greater than 1%.

[0011] In the above embodiments, the limestone powder contains no less than 85% CaCO3 and has a fineness Dv50 of no more than 20 μm.

[0012] In the above embodiments, the iron silicate is an industrial by-product iron silicate with a FeSiO3 content of not less than 90% and a particle size D90 ≤ 45μm.

[0013] A method for preparing a slag powder-fly ash cementitious material using ferric silicate as an activator includes the following steps: S1. Raw material pretreatment and classification: S1.1 Dry the slag powder and furnace slag powder at 100-110℃ until the moisture content is <1.0%, and then classify them by air classifier, and select particles with a particle size Dv50 of 15-25μm as the main material A; S1.2 After drying the gypsum at a low temperature of 60-70℃ until the moisture content is less than 5%, place it together with ferrosilicon in a vibrating screen and mix it at a frequency of 200-300 times / min for 5-10 minutes to form activator composite material B; S2. Segmented energy-optimized grinding: S2.1 First stage coarse grinding and activation: The main material A obtained in step S1.1 and the activator composite material B, accounting for 60%-80% of the total weight, are fed into a high-energy ball mill. Under the conditions of mill speed of 28-32 r / min, ball-to-material ratio of 6:1, and filling rate of 30%, grinding is carried out for 18-22 min to obtain a specific surface area of ​​270-290 m². 2 Intermediate C per kg; S2.2 Second Stage Fine Grinding Integration: Intermediate C, fly ash, limestone powder, and the remaining activator composite material B are fed into a high-efficiency vortex classifier vertical mill, with a system air volume of 5500-6500 m³ / h. 3 Compound grinding is carried out under the conditions of 280-320 r / min for classifier, with the outlet temperature controlled not to exceed 75℃, and the total grinding time 35-45 min, until the specific surface area of ​​the final product reaches 350-360 m². 2 / kg, and the particle size distribution Span value [(Dv90-Dv10) / Dv50] is less than 1.8, to obtain semi-finished product D; S3. Controllable hydration activation aging: The semi-finished product D is transported to an aging chamber with humidity control and aged for 36-48 hours at a temperature of 38-42℃ and a relative humidity of 65-75%. During this period, compressed air is used to pulse-turn every 12 hours, with a turning air pressure of 0.15-0.25MPa and each turning lasting for 3-5 minutes, finally obtaining the gelling material.

[0014] In the above embodiment, the grinding media used in the high-energy ball mill in step S2.1 are chromium alloy steel balls with diameters of 10mm, 15mm and 20mm mixed in a mass ratio of 3:5:2.

[0015] In the above embodiments, the characteristic is that: in step S2.2, the temperature of the material exiting the mill is controlled by spraying atomized water, and the amount of atomized water added is 0.5%-1.0% of the total weight of the material.

[0016] The embodiments of the present invention have the following advantages due to the adoption of the above technical solutions: A composite activating system is constructed using industrial by-product ferric silicate and gypsum. The slightly acidic environment provided by the hydrolysis of ferric silicate efficiently destroys the glassy structure of slag and fly ash. This, combined with the sulfate activating effect provided by gypsum, enhances the early strength development rate of cementitious materials. At the same time, it avoids the problems of excessively rapid setting and poor construction adaptability caused by traditional strong alkali activators.

[0017] By compounding slag powder, fly ash, furnace slag powder and limestone powder in a specific ratio, not only can the efficient resource utilization of bulk industrial solid waste be achieved, but also the chemical and physical effects of each component can work together to optimize particle size distribution, improve system density, improve the workability of slurry and reduce the water requirement for standard consistency.

[0018] The hydration products of the cementitious material described in this invention are mainly C-(A)-SH gel with a low calcium-to-silicon ratio. The system has low alkalinity and very little calcium hydroxide content, which are the main reaction substrates for eliminating sulfate attack. Therefore, it has excellent long-term durability, especially its resistance to sulfate attack is significantly better than that of traditional silicate cement.

[0019] The activation system and segmented grinding-aging process make the hydration process mild and the heat release gradual. The total heat release is significantly lower than that of ordinary Portland cement, which effectively reduces the risk of cracking caused by temperature stress. It is particularly suitable for large-volume concrete projects, and at the same time achieves synergistic optimization of multiple performance indicators such as early strength, workability, durability and heat of hydration.

[0020] The above overview is for illustrative purposes only and is not intended to be limiting in any way. Detailed Implementation

[0021] The invention will be more readily understood by referring to the following detailed description of preferred embodiments and included examples. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In case of conflict, the definitions in this specification shall prevail.

[0022] As used herein, the terms “prepared from” and “comprising” are synonymous. The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0023] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0024] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including the ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0025] The singular form includes the plural objects of discussion unless the context clearly indicates otherwise. "Optional" or "any one" means that the matter or event described thereafter may or may not occur, and the description includes both the possibility that the event occurs and the possibility that the event does not occur.

[0026] Approximate terms used in the specification and claims to modify quantities indicate that the invention is not limited to that specific quantity, but also includes acceptable modifications close to that quantity that do not alter the relevant essential function. Correspondingly, the use of "about," "approximately," etc., to modify a numerical value means that the invention is not limited to that precise value. In some instances, approximate terms may correspond to the precision of the instrument used to measure the value. In this application's specification and claims, scope definitions can be combined and / or interchanged, unless otherwise stated, these scopes include all subscopes contained therein.

[0027] Furthermore, the indefinite articles “a” and “an” preceding the elements or components of this invention do not impose any limitation on the quantity (i.e., number of times) of the elements or components. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers to the singular form.

[0028] Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0029] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the experimental materials and test strains used in the following examples were purchased from commercial channels.

[0030] A slag powder-fly ash cementitious material using ferric silicate as an activator, comprising the following components by weight percentage: slag powder: 30-50%; gypsum: 2-15%; fly ash: 15-20%; slag powder: 10-15%; limestone powder: 10-15%; ferric silicate: 3-8%. The sum of the weight percentages of all components is 100%. In this embodiment, slag powder, fly ash, and furnace slag powder are used as the main cementitious active materials, gypsum and ferric silicate are used as activators, and limestone powder is used as a filler and functional adjustment material.

[0031] The slag powder is made from granulated blast furnace slag, which has a glassy structure formed by rapid cooling and is rich in highly active calcium, silicon, and aluminum components (CaO, SiO2, Al2O3). Under the action of an activator, it rapidly depolymerizes and recombines to form gel products such as hydrated calcium silicate (CSH) and hydrated calcium aluminate (CAH) to ensure the strength of the cementitious material.

[0032] The vitreous SiO2 and Al2O3 in fly ash react slowly in the early stages, but in the later stages (usually after 28 days), they undergo a secondary hydration reaction with Ca(OH)2 generated in the gel material, generating additional CSH gel, which continuously increases the later strength and makes the strength development curve more stable. At the same time, the microspheres abundant in fly ash can effectively improve the rheological properties of the slurry, reduce water demand, and improve the density and impermeability of the material.

[0033] The slag powder is made from circulating fluidized bed boiler slag, which contains high levels of amorphous SiO2 and Al2O3, and its function is similar to that of slag and fly ash.

[0034] Gypsum, produced by dissolving The gypsum reacts with the active Al2O3 in the slag to form ettringite (AFt). Eettringite is a needle-like crystal that provides significant early strength and helps compensate for shrinkage. Simultaneously, an appropriate amount of gypsum can slow down the setting rate of the slag, allowing sufficient time for construction.

[0035] Ferrous silicate (FeSiO3) can hydrolyze in the presence of water, creating slightly acidic conditions that can efficiently disrupt the Si-O-Si and Si-O-Al network structures of slag and fly ash glass, causing them to dissolve and release active ions, which greatly promotes the formation of subsequent hydration products.

[0036] Meanwhile, the introduced iron element can participate in the hydration products, such as forming iron-containing C-(A)-SH gels or other iron phases, which can have a positive impact on certain properties of the material (such as corrosion resistance and early strength).

[0037] In addition, ferric silicate (FeSiO3) and gypsum can form a highly efficient composite excitation of "acid destruction-sulfate reconstruction", which is more efficient than traditional single excitation agents.

[0038] Limestone powder can fill the gaps between active particles, making the structure more compact and reducing porosity, thereby improving strength and durability. At the same time, limestone powder (CaCO3) is not completely inert and can react with hydrated aluminates to form a carboaluminate phase, which helps stabilize early-stage ettringite and prevents it from transforming into monosulfide-type hydrated calcium sulfoaluminate (AFm) in the later stages, thus promoting the stable development of early strength.

[0039] Furthermore, the slag powder is obtained by grinding granulated blast furnace slag, and its specific surface area is not less than 400 m². 2 / kg, density is 2.8-3.0 g / cm³ 3 .

[0040] Slag powder is granulated blast furnace slag with a high content of amorphous glass, and its amorphous structure is the material basis for its potential hydraulic activity.

[0041] Its ≥400 m 2 The high specific surface area of ​​the slag powder (approximately 0.5 kg / kg) allows for finer particle size, which accelerates and deepens the interfacial reaction with the sulfate activator (gypsum) and acidic activator (ferric silicate). In this embodiment, the high specific surface area of ​​the slag powder ensures effective mechanical activation during the first stage of coarse grinding activation (S2.1) in the "segmented energy-optimized grinding" process, increasing its surface energy and providing conditions for subsequent efficient hydration.

[0042] Its 2.8-3.0 g / cm 3 The density indicates that it has a stable chemical composition and mineral composition, which ensures the quality stability and compositional consistency of the slag powder, thereby keeping the alkalinity coefficient and quality coefficient of the selected slag powder in a high-activity and stable range.

[0043] The gypsum is any one or a combination of two of desulfurized gypsum and phosphogypsum, with a crystal water content of not less than 15% and an SO3 content of ≥35%.

[0044] In this embodiment, desulfurized gypsum or phosphogypsum is used as a sulfate activator, which is not only low in cost, but also solves the problem of disposal of large quantities of industrial solid waste, demonstrating the environmental value and economic benefits of this technical solution.

[0045] Calcium sulfate dihydrate (CaSO4·2H2O) is the core active phase for gypsum to exert its sulfate-activating effect. Its theoretical crystal water content is about 20.9%. Therefore, in this embodiment, the gypsum used must be mainly in the form of calcium sulfate dihydrate to avoid the loss of a large amount of crystal water due to excessive calcination or weathering, which would transform it into hemihydrate gypsum (CaSO4·0.5H2O) or anhydrous gypsum (CaSO4).

[0046] During implementation, gypsum dihydrate exhibits moderate reactivity, providing a stable and continuous [response]. The supply, in conjunction with the acidic activation effect of ferrosilicon, forms a synergistic effect, jointly activating the slag powder and fly ash. If the water of crystallization is too low, i.e. there is a large amount of anhydrous gypsum, its hydration rate is too fast, which will lead to abnormal setting and cracking. Or if there is a large amount of hemihydrate gypsum, it is easy to prehydrate and clump during storage and grinding, which will destroy the uniformity of the subsequent "S1.2 and ferrosilicon blending" and interfere with the stability of the "S3 controllable hydration activation aging" process.

[0047] SO3 provides sulfate ions to gypsum ( The effective component of calcium sulfate dihydrate is approximately 46.5% SO3. In this embodiment, the SO3 content is ≥35%, which ensures that the raw material has sufficient effective stimulating components and indirectly limits the content of impurities (such as phosphorus and fluorine impurities that may be contained in phosphogypsum; chloride ions and unreacted calcium carbonate that may be contained in desulfurized gypsum).

[0048] During implementation, sufficient SO3 content is the stoichiometric basis for the formation of adequate ettringite and its contribution to early strength. If the SO3 content is insufficient, the sulfate activation effect is weakened, failing to effectively complement the ferrosilicon activation, thus preventing the early strength of the cementitious material from reaching the expected level. Simultaneously, controlling impurity content can prevent impurities from adversely interfering with the hydration process (such as delaying setting or disrupting the structure of hydration products), ensuring the reliability and reproducibility of the cementitious material's performance.

[0049] The slag powder is made by grinding circulating fluidized bed boiler slag, with a total SiO2+Al2O3+Fe2O3 content of not less than 70% and a moisture content of not more than 1%.

[0050] Due to its unique combustion conditions, slag powder contains more potentially active amorphous aluminosilicates in its mineral composition, and usually contains calcium-based compounds introduced by in-furnace desulfurization.

[0051] SiO2, Al2O3, and Fe2O3 participate in alkaline-activated or sulfate-activated reactions to generate gel products such as hydrated calcium silicate (CSH), hydrated calcium aluminate, and hydrated calcium iron aluminate.

[0052] In this embodiment, the active components of slag powder synergistically combine with those of blast furnace slag powder and fly ash to form the reaction basis of the entire cementitious network. Its specific chemical components can react with the SO4 provided by gypsum. 2- The reaction generates ettringite, optimizing the pore structure of the cementitious material. The total content of SiO2, Al2O3, and Fe2O3 is no less than 70%, ensuring their effective participation in complex hydration reactions and achieving the expected synergistic enhancement effect.

[0053] Its moisture content is no more than 1%, ensuring that all subsequent grinding and mixing processes proceed efficiently and smoothly. In this embodiment, the low moisture content setting can prevent a sharp drop in grinding efficiency and an increase in energy consumption caused by damp materials adhering to the mill and grinding media in "S2.1 First Stage Coarse Grinding Activation"; in addition, in "S1.2" and subsequent feeding and mixing processes, it can prevent the damp slag powder from clumping together, which would prevent it from mixing evenly with gypsum, ferric silicate and other activators and components, resulting in uneven local reactions.

[0054] The limestone powder contains no less than 85% CaCO3 and has a fineness Dv50 of no more than 20μm.

[0055] CaCO3 can participate in hydration reactions, reacting with hydrated aluminates (from slag and fly ash) to form aluminocarbonate phases, which helps stabilize early hydration products—ettringite. At the same time, the high CaCO3 content ensures the stability and predictability of its chemical properties, preventing excessive impurities (such as clay, SiO2, etc.) from interfering with the main hydration process due to their different water absorption and reactivity, or negatively impacting the workability (rheological properties) and setting time of the slurry.

[0056] Its fineness Dv50 is no greater than 20μm, which enables it to exert the micro-aggregate filling effect. In this embodiment, limestone powder of this fineness can fill the gaps between active particles such as slag powder and furnace slag powder with a certain particle size distribution generated by "S2.1 first stage coarse grinding activation", thereby reducing the porosity of the cementitious material and increasing its bulk density and compactness.

[0057] Ferric silicate is an industrial by-product of ferric silicate, with a FeSiO3 content of not less than 90% and a particle size D90≤45μm.

[0058] Specifically, its FeSiO3 content is not less than 90%. Under the condition of high FeSiO3 content, FeSiO3 can undergo sufficient hydrolysis in the hydration environment to provide an acidic environment, thereby efficiently breaking the Si-O-Si and Si-O-Al covalent bonds in the glassy structure of slag and fly ash, causing them to depolymerize and release active ions (Ca). 2+ , , ).

[0059] Meanwhile, the FeSiO2 content is not less than 90%, and the total amount of impurities is ≤10%, so as to avoid excessive impurities (such as other metal salts, unreacted oxides, etc.) from causing unpredictable interference to the hydration process, such as possible slowing or accelerating coagulation or adverse effects on long-term durability.

[0060] Its particle size D90≤45μm, when mixed with gypsum in the process of “S1.2 and gypsum”, can achieve highly uniform mixing with gypsum particles at the microscale to form a homogeneous “activator composite material B”, which can ensure that the subsequent activation effect occurs uniformly in the entire cementitious material and prevent local overreaction or underreaction caused by agglomeration or uneven distribution.

[0061] Meanwhile, the particle size D90≤45μm gives FeSiO3 a larger specific surface area, significantly increasing the contact area between iron silicate and water, accelerating its hydrolysis process, and enabling the acid activation effect to be started quickly and uniformly, working efficiently and synergistically with the sulfate activation effect of gypsum.

[0062] Moreover, this particle size allows it to successfully participate in the "S2.1 first stage coarse grinding activation", achieving full contact with the newly formed highly active surface while undergoing mechanical activation.

[0063] A method for preparing a slag powder-fly ash cementitious material using ferric silicate as an activator includes the following steps: S1. Raw material pretreatment and classification: S1.1 Dry the slag powder and furnace slag powder at 100-110℃ until the moisture content is <1.0%, and then classify them by air classifier, and select particles with a particle size Dv50 of 15-25μm as the main material A; During implementation, a drying temperature of 100-110℃, higher than the boiling point of water, effectively removes adsorbed water and some interlayer water from the slag powder and furnace slag powder, ensuring drying efficiency. Simultaneously, this temperature is lower than the glass transition temperature of the glassy phase of slag and furnace slag, preventing overheating from causing structural relaxation of the active glass and loss of potential chemical activity, thus preserving the material's reaction potential while removing moisture.

[0064] A moisture content of less than 1.0% provides a prerequisite for the efficient and stable execution of all subsequent grinding and mixing processes. Specifically, in "S2.1 First Stage Coarse Grinding and Activation," the dry material has good flowability, effectively avoiding the "pasting" phenomenon caused by wet material adhering to the inner wall of the mill and the grinding media, ensuring that the machinery can be used efficiently for material crushing and activation. Moreover, the dry powder is easy to flow and disperse, ensuring that the main material A and the subsequent activator composite material B can achieve uniform mixing at the microscale in S2.1.

[0065] A particle size Dv50 of 15-25 μm provides a uniform and suitable particle size distribution for the "S2.1 First Stage Coarse Grinding Activation". If the initial particle size of the raw material is too coarse, it will significantly increase the load and time of the first stage grinding. Moreover, particles in this particle size range have a high specific surface area and reactivity, while also having good flowability and packing properties, which is conducive to sufficient and uniform contact and reaction with the activator in subsequent processes.

[0066] S1.2 After drying the gypsum at a low temperature of 60-70℃ until the moisture content is less than 5%, place it together with ferrosilicon in a vibrating screen and mix it at a frequency of 200-300 times / min for 5-10 minutes to form activator composite material B; Low-temperature drying is used to perform stability pretreatment on gypsum (sulfate activator) to protect the crystal structure and chemical activity of gypsum dihydrate (CaSO4·2H2O). During implementation, the temperature is controlled below 70℃ to effectively prevent phase transformation of gypsum dihydrate and ensure that its dihydrate compound form enters the subsequent process.

[0067] Its moisture content is less than 5%, which can remove free water from gypsum and prevent the wet gypsum powder from clumping when mixed with ultrafine iron silicate powder (D90≤45μm), which would prevent the two from being mixed evenly and thus result in uneven mixing of the activator.

[0068] Meanwhile, it adopts a vibrating screen mixing method. The high-frequency micro-amplitude vibration of the vibrating screen can generate efficient shearing and diffusion effects on the powder, which can evenly disperse iron silicate into gypsum. It can effectively break the soft agglomeration that iron silicate particles may cause due to van der Waals forces, achieve uniform mixing of the two, and avoid the mixing dead corners or unevenness that may be caused by ordinary stirring.

[0069] The resulting activator composite material B is a homogeneous mixture, ensuring uniform distribution of gypsum and acidic activator (ferric silicate), guaranteeing a synergistic activation effect during subsequent grinding and hydration processes. Furthermore, in "S2.1 First Stage Coarse Grinding Activation," the homogeneous activator composite material B is added in stages, ensuring uniform contact between the activator and the main material A, allowing the activation reaction to proceed synchronously and consistently, thereby improving the homogeneity and stability of the cementitious material's properties.

[0070] S2. Segmented energy-optimized grinding: S2.1 First stage coarse grinding and activation: The main material A obtained in step S1.1 and the activator composite material B, accounting for 60%-80% of the total weight, are fed into a high-energy ball mill. Under the conditions of mill speed of 28-32 r / min, ball-to-material ratio of 6:1, and filling rate of 30%, grinding is carried out for 18-22 min to obtain a specific surface area of ​​270-290 m². 2 Intermediate C per kg; This step achieves the initial coupling of mechanical activation and chemical activation by synergistically treating the pretreated active ingredient A with most of the composite activator B under specific high-energy mechanical force conditions, generating a pre-activated intermediate C.

[0071] Specifically, mechanical activation increases the specific surface area of ​​materials through the mechanical force of high-energy ball milling. At the same time, it generates lattice defects and distortions within the particles and stores a large amount of surface energy, putting them in a thermodynamically unstable and highly active state, thereby enhancing their chemical reaction potential.

[0072] While mechanical activation is being performed, activator composite material B, accounting for 60%-80% of the total weight, is added, so that the newly generated highly active surface can immediately come into contact with the sulfate activator (gypsum) and the acidic activator (ferric silicate), achieving synergy and superposition of mechanical activation and chemical activation.

[0073] During implementation, a mill speed of 28-32 r / min, below the critical speed, ensures that the grinding media (steel balls) are mainly in a cascading state rather than being thrown, so that the motion is dominated by grinding and friction. This is conducive to continuous and gentle shearing and grinding of the material, thereby achieving effective mechanical activation rather than simple impact crushing, which is beneficial to obtaining ideal particle morphology and surface condition.

[0074] A ball-to-material ratio of 6:1 ensures that a unit mass of material is equipped with a large amount of grinding media, guaranteeing sufficient collision and grinding contact points. This ensures that there is enough mechanical energy for the activation and refinement of the material, thereby improving grinding efficiency and activation level.

[0075] The 30% filling rate, combined with the ball-to-material ratio, provides reasonable movement space for the grinding media, ensuring good media movement trajectory and energy transmission efficiency, and avoiding energy waste or insufficiency caused by overfilling.

[0076] Furthermore, the grinding media used in the high-energy ball mill are 10mm, 15mm and 20mm chromium alloy steel balls mixed in a mass ratio of 3:5:2.

[0077] Different sizes of grinding media during ball milling: Φ10mm chromium alloy steel balls: provide grinding force. Their large quantity and large total surface area effectively fill the gaps between the large and medium-sized balls, performing fine grinding and friction on the material, increasing surface defects in the particles, and achieving mechanical activation.

[0078] Φ15mm chromium alloy steel balls: serving as the primary medium, balancing impact and grinding forces. They mainly grind materials while also participating in impact crushing to increase the specific surface area of ​​the materials.

[0079] Φ20mm chromium alloy steel balls: primarily provide impact force. Their large mass results in high kinetic energy during movement, enabling effective impact crushing of materials and pulverizing larger agglomerates and particles.

[0080] In addition, the ratio of grinding media of different sizes ensures a reasonable spatial distribution of media of different sizes in the grinding chamber, forming an efficient crushing-grinding collaborative network, minimizing the probability of "empty collisions" and maximizing the use of input mechanical energy for material crushing and activation.

[0081] S2.2 Second Stage Fine Grinding Integration: Intermediate C, fly ash, limestone powder, and the remaining activator composite material B are fed into a high-efficiency vortex classifier vertical mill, with a system air volume of 5500-6500 m³ / h. 3Compound grinding is carried out under the conditions of 280-320 r / min for classifier, with the outlet temperature controlled not to exceed 75℃, and the total grinding time 35-45 min, until the specific surface area of ​​the final product reaches 350-360 m². 2 / kg, and the particle size distribution Span value [(Dv90-Dv10) / Dv50] is less than 1.8, to obtain semi-finished product D; During implementation, fly ash and limestone powder are added all at once to prevent them from participating in the high-energy ball milling in step S2.1, thus protecting the spherical morphology of the fly ash (which is beneficial for flowability) and the fineness of the limestone powder. Simultaneously, the remaining activator composite material B (accounting for 20%-40% of the total) is added to achieve phased addition of the activator. This prevents all the activator from reacting excessively in one stage and ensures a uniform distribution of the activator in the final product, providing a reaction basis for step S3.

[0082] The mill exit temperature is ≤75℃ to prevent harmful phase transformation of materials (especially gypsum). Dihydrate gypsum begins to dehydrate and lose its water of crystallization above 80℃, transforming into hemihydrate or anhydrous gypsum, thus completely changing its hydration properties and setting effect.

[0083] Furthermore, the temperature exiting the mill is controlled by spraying atomized water, with the amount of atomized water added being 0.5%-1.0% of the total weight of the material.

[0084] By using atomized water spraying, liquid water can be dispersed into extremely fine droplets, thereby increasing its specific surface area. After entering the vertical mill system, it can quickly come into contact with high-temperature materials and airflow, and uniformly and rapidly remove the large amount of mechanical heat energy generated during the grinding process through efficient evaporation and heat absorption.

[0085] An addition of 0.5%-1.0% can prevent localized materials from undergoing pre-hydration reactions with the activator (especially gypsum and ferric silicate) due to accidental overwetting during the grinding process. Pre-hydration will consume the effective activating components, change the surface properties of the material, potentially lead to runaway in step S3, and affect the setting time and strength development of the final product.

[0086] Meanwhile, after evaporation, this amount of additive can reduce the impact on the dryness and good flowability of the material, thereby preventing the material from adhering to the inside of the mill and classifier, and ensuring the continuous and stable operation of the grinding-classification system.

[0087] S3. Controllable hydration activation aging: The semi-finished product D is transported to an aging chamber with humidity control and aged for 36-48 hours at a temperature of 38-42℃ and a relative humidity of 65-75%. During this period, compressed air is used to pulse-turn every 12 hours, with a turning air pressure of 0.15-0.25MPa and each turning lasting for 3-5 minutes, finally obtaining the gelling material.

[0088] A temperature of 38-42℃, higher than room temperature, effectively accelerates the reaction rate between the activator and the active component, shortening the overall time to reach the predetermined performance indicators. Simultaneously, this temperature range is lower than high temperatures (such as above 80℃), avoiding the transformation or decomposition of hydration products (such as ettringite) and potential negative impacts on the durability of the final product. Therefore, it ensures that the hydration reaction proceeds smoothly and rapidly in the expected direction.

[0089] A relative humidity of 65-75% ensures sufficient water molecules to participate in the reaction. Simultaneously, it avoids the presence of liquid water, which could lead to material clumping and wall formation, thus disrupting the material's homogeneity. Furthermore, this humidity range allows water molecules to contact the material particle surface in a gaseous state, initiating the reaction at the interface, resulting in a gentler and more controllable process.

[0090] The time control of 36-48 hours ensures that a sufficient number of active particles in the cementitious material can undergo preliminary hydration, consume some of the heat during the intense reaction period, generate early hydration products, and stabilize the reactivity of the entire cementitious material.

[0091] This step consumes the early reaction heat of the material, avoiding the risk of cracking caused by concentrated heat release during user operation. Its setting time and strength development curves become stable and predictable.

[0092] In practical implementation, the activator can also be iron phosphate or a mixture of iron silicate and iron phosphate to improve the strength.

[0093] Example 1 This invention provides a slag powder-fly ash cementitious material using ferric silicate as an activator, comprising the following components by weight percentage: slag powder: 30%; gypsum: 15%; fly ash: 20%; furnace slag powder: 15%; limestone powder: 15%; ferric silicate: 5%. Specifically, the slag powder is obtained by grinding granulated blast furnace slag, and its specific surface area is not less than 400 m². 2 / kg, density is 2.8 g / cm³ 3 .

[0094] The gypsum is any one or a combination of two of desulfurized gypsum and phosphogypsum, with a crystal water content of not less than 15% and an SO3 content of ≥35%.

[0095] The slag powder is made by grinding circulating fluidized bed boiler slag, with a total SiO2+Al2O3+Fe2O3 content of not less than 70% and a moisture content of not more than 1%.

[0096] The limestone powder contains no less than 85% CaCO3 and has a fineness Dv50 of no more than 20μm.

[0097] Ferric silicate is an industrial by-product of ferric silicate, with a FeSiO3 content of not less than 90% and a particle size D90 ≤ 45μm.

[0098] A method for preparing a slag powder-fly ash cementitious material using ferric silicate as an activator includes the following steps: S1. Raw material pretreatment and classification: S1.1 Dry the slag powder and furnace slag powder at 100℃ until the moisture content is <1.0%, and then classify them by air classifier. Select particles with a particle size Dv50 of 15μm as the main material A. S1.2 After drying the gypsum at a low temperature of 60℃ until the moisture content is less than 5%, place it together with ferrosilicon in a vibrating screen and mix it at a frequency of 200 times / min for 5 minutes to form activator composite material B; S2. Segmented energy-optimized grinding: S2.1 First stage coarse grinding and activation: The main material A obtained in step S1.1 and the activator composite material B, accounting for 60%-80% of the total weight, are fed into a high-energy ball mill. Under the conditions of mill speed of 28 r / min, ball-to-material ratio of 6:1, and filling rate of 30%, grinding is carried out for 18 min to obtain a specific surface area of ​​270 m². 2 Intermediate C per kg; Furthermore, the grinding media used in the high-energy ball mill are 10mm, 15mm and 20mm chromium alloy steel balls mixed in a mass ratio of 3:5:2.

[0099] S2.2 Second Stage Fine Grinding Integration: Intermediate C, fly ash, limestone powder, and the remaining activator composite material B are fed into a high-efficiency vortex classifier vertical mill, with a system air volume of 5500 m³ / h. 3 Compound grinding is carried out under the conditions of 280-320 r / min for the classifier, controlling the outlet temperature to not exceed 75℃, and the total grinding time to 35-45 min, until the specific surface area of ​​the final product reaches 350 m². 2 / kg, and the particle size distribution Span value [(Dv90-Dv10) / Dv50] is less than 1.8, to obtain semi-finished product D; Furthermore, the temperature of the material exiting the mill is controlled by spraying atomized water, with the amount of atomized water added being 0.5% of the total weight of the material.

[0100] S3. Controllable hydration activation aging: The semi-finished product D is transported to an aging chamber with humidity control and aged for 36 hours at a temperature of 38°C and a relative humidity of 65%. During this period, compressed air is used to pulse-turn the material every 12 hours at a pressure of 0.15 MPa for 3 minutes each time, and the final gelling material is obtained.

[0101] Example 2 A slag powder-fly ash cementitious material using ferric silicate as an activator, comprising the following components by weight percentage: slag powder: 40%; gypsum: 10%; fly ash: 19%; slag powder: 11%; limestone powder: 15%; ferric silicate: 5%. The sum of the weight percentages of all components is 100%. Specifically, the slag powder is obtained by grinding granulated blast furnace slag, and its specific surface area is not less than 400 m². 2 / kg, density is 2.9 g / cm³ 3 .

[0102] The gypsum is any one or a combination of two of desulfurized gypsum and phosphogypsum, with a crystal water content of not less than 15% and an SO3 content of ≥35%.

[0103] The slag powder is made by grinding circulating fluidized bed boiler slag, with a total SiO2+Al2O3+Fe2O3 content of not less than 70% and a moisture content of not more than 1%.

[0104] The limestone powder contains no less than 85% CaCO3 and has a fineness Dv50 of no more than 20μm.

[0105] The iron silicate mentioned is an industrial by-product iron silicate with a FeSiO3 content of not less than 90% and a particle size D90 ≤ 45μm.

[0106] A method for preparing a slag powder-fly ash cementitious material using ferric silicate as an activator includes the following steps: S1. Raw material pretreatment and classification: S1.1 Dry the slag powder and furnace slag powder at 105℃ until the moisture content is <1.0%, and then classify them by air classifier. Select particles with a particle size Dv50 of 20μm as the main material A. S1.2 After drying the gypsum at a low temperature of 65℃ until the moisture content is less than 5%, it is placed together with ferric silicate in a vibrating screen and mixed at a frequency of 250 times / min for 8 minutes to form activator composite material B; S2. Segmented energy-optimized grinding: S2.1 First stage coarse grinding and activation: The main material A obtained in step S1.1 and the activator composite material B, accounting for 70% of the total weight, are fed into a high-energy ball mill. Under the conditions of mill speed of 30 r / min, ball-to-material ratio of 6:1, and filling rate of 30%, grinding is carried out for 20 min to obtain a specific surface area of ​​280 m². 2 Intermediate C per kg; Furthermore, the grinding media used in the high-energy ball mill are 10mm, 15mm and 20mm chromium alloy steel balls mixed in a mass ratio of 3:5:2.

[0107] S2.2 Second Stage Fine Grinding Integration: Intermediate C, fly ash, limestone powder, and the remaining activator composite material B are fed into a high-efficiency vortex classifier vertical mill, with a system air volume of 6000 m³ / h. 3 Compound grinding was carried out under the conditions of 300 r / min classifier speed, with the outlet temperature controlled not to exceed 75℃, and the total grinding time was 40 min, until the specific surface area of ​​the final product reached 355 m². 2 / kg, and the particle size distribution Span value [(Dv90-Dv10) / Dv50] is less than 1.8, to obtain semi-finished product D; Furthermore, the temperature of the material exiting the mill is controlled by spraying atomized water, with the amount of atomized water added being 0.8% of the total weight of the material.

[0108] S3. Controllable hydration activation aging: The semi-finished product D is transported to an aging chamber with humidity control and aged for 42 hours at a temperature of 40°C and a relative humidity of 70%. During this period, compressed air is used to pulse-turn every 12 hours, with a turning air pressure of 0.2 MPa and each turning lasting for 4 minutes, finally obtaining the gelling material.

[0109] Example 3 A slag powder-fly ash cementitious material using ferric silicate as an activator, comprising the following components by weight percentage: slag powder: 49%; gypsum: 10%; fly ash: 15%; slag powder: 10%; limestone powder: 11%; ferric silicate: 5%. The sum of the weight percentages of all components is 100%. Specifically, it is composed of the following components by weight percentage: slag powder: 40%; gypsum: 10%; fly ash: 19%; slag powder: 10%; limestone powder: 16%; and ferric silicate: 5%.

[0110] The slag powder is obtained by grinding granulated blast furnace slag, and its specific surface area is not less than 400 m². 2 / kg, density is 3.0 g / cm³ 3 .

[0111] The gypsum is any one or a combination of two of desulfurized gypsum and phosphogypsum, with a crystal water content of not less than 15% and an SO3 content of ≥35%.

[0112] The slag powder is made by grinding circulating fluidized bed boiler slag, with a total SiO2+Al2O3+Fe2O3 content of not less than 70% and a moisture content of not more than 1%.

[0113] The limestone powder contains no less than 85% CaCO3 and has a fineness Dv50 of no more than 20μm.

[0114] The iron silicate mentioned is an industrial by-product iron silicate with a FeSiO3 content of not less than 90% and a particle size D90 ≤ 45μm.

[0115] A method for preparing a slag powder-fly ash cementitious material using ferric silicate as an activator includes the following steps: S1. Raw material pretreatment and classification: S1.1 Dry the slag powder and furnace slag powder at 110℃ until the moisture content is <1.0%, and then classify them by air classifier. Select particles with a particle size Dv50 of 25μm as the main material A. S1.2 After drying the gypsum at a low temperature of 70℃ until the moisture content is less than 5%, place it together with ferrosilicon in a vibrating screen and mix it at a frequency of 300 times / min for 5-10 minutes to form activator composite material B. S2. Segmented energy-optimized grinding: S2.1 First stage coarse grinding and activation: The main material A obtained in step S1.1 and the activator composite material B, accounting for 80% of the total weight, are fed into a high-energy ball mill. Under the conditions of mill speed of 32 r / min, ball-to-material ratio of 6:1, and filling rate of 30%, grinding is carried out for 22 min to obtain a specific surface area of ​​2290 m². 2 Intermediate C per kg; Furthermore, the grinding media used in the high-energy ball mill are 10mm, 15mm and 20mm chromium alloy steel balls mixed in a mass ratio of 3:5:2.

[0116] S2.2 Second Stage Fine Grinding Integration: Intermediate C, fly ash, limestone powder, and the remaining activator composite material B are fed into a high-efficiency vortex classifier vertical mill, with a system air volume of 6500 m³ / h. 3 Compound grinding was carried out under the conditions of 320 r / min classifier speed, with the outlet temperature controlled not to exceed 75℃, and the total grinding time was 45 min, until the specific surface area of ​​the final product reached 360 m². 2 / kg, and the particle size distribution Span value [(Dv90-Dv10) / Dv50] is less than 1.8, to obtain semi-finished product D; Furthermore, the temperature exiting the mill is controlled by spraying atomized water, with the amount of atomized water added being 0.5%-1.0% of the total weight of the material.

[0117] S3. Controllable hydration activation aging: The semi-finished product D is transported to an aging chamber with humidity control and aged for 48 hours at a temperature of 42°C and a relative humidity of 75%. During this period, compressed air is used to pulse-turn the material every 12 hours at a pressure of 0.25 MPa for 3-5 minutes each time, and the final gelling material is obtained.

[0118] Experimental Example 1 (Comparative Test on the Development of Mechanical Properties): 1.1 Experimental Objective: By using standardized testing methods, the flexural strength and compressive strength of the "slag powder-fly ash cementitious material with ferric silicate as activator" (experimental group) proposed in this invention were compared and evaluated with the reference cement, traditional alkali-activated materials and ferric silicate-free materials at different curing ages, so as to quantitatively demonstrate the advantages of this invention in mechanical properties, especially early strength and development stability.

[0119] 1.2 Experimental Materials and Grouping:

[0120] 1.3 Test Procedure 1.3.1 Mortar Preparation: Mixing ratio: mortar mass ratio is 1:3 (cementing material: standard sand), water-cement ratio (W / B) is 0.5.

[0121] Note: For control group B, "water" includes water in the alkaline activator solution to ensure a consistent final water-to-gel ratio of 0.5.

[0122] Mixing: Use a planetary cement mortar mixer and mix according to the standard procedure.

[0123] 1.3.2 Specimen molding: The mixed mortar was divided into two layers and poured into a triple mold measuring 40mm × 40mm × 160mm.

[0124] Each layer is compacted 60 times on a vibration table (frequency 60 times / minute, amplitude 0.75mm).

[0125] Scrape off any excess adhesive and smooth the surface.

[0126] 1.3.3 Maintenance: The molded specimens were placed in a constant temperature and humidity curing chamber (temperature 20±1°C, relative humidity ≥90%) for 24±2 hours.

[0127] After demolding, the specimens were immediately placed in saturated lime water at a temperature of 20±1°C and cured until the specified age.

[0128] 1.3.4 Strength Test: After curing for 3, 7, 28, and 90 days respectively, the specimens were removed from the curing water for strength testing.

[0129] First, use a flexural testing machine (lever ratio of 1:50) to apply a uniform load at a rate of 50±10 N / s and determine the flexural strength (Rf).

[0130] The six broken prism halves were immediately subjected to a compressive strength test. The side surface of the half prism was used as the compression surface for the compressive strength test, with a compression area of ​​40 mm × 40 mm. The load was uniformly applied at a rate of 2400 ± 200 N / s until failure, and the compressive strength (Rc) was recorded.

[0131] For each age group, at least 3 specimens should be tested, and the strength value should be the average of 6 compressive strength results (if one exceeds the average by ±10%, it should be discarded and the average of the remaining 5 should be taken).

[0132] 1.4 Experimental Data Table 1: Flexural and compressive strength data of each experimental group at different ages

[0133] 1.5 Experimental Conclusions and Data Analysis Compared with the benchmark cement (control group A): Early strength (3 days): The 3-day compressive strength of the experimental group (28.5 MPa) was significantly higher than that of the control group A (25.8 MPa), exceeding it by approximately 10.5%. This indicates that the activation system of the present invention is highly efficient and the hydration reaction starts rapidly.

[0134] Later strength (28 / 90 days): The 28-day and 90-day compressive strength of the experimental group (62.1 MPa / 70.8 MPa) far exceeded that of the control group A (49.3 MPa / 53.5 MPa), by approximately 26% and 32% respectively. This demonstrates that the material of this invention not only develops strength rapidly in the early stages but also has strong potential for strength growth in the later stages, and its final performance is far superior to that of traditional cement.

[0135] Compared with traditional alkali-activated materials (control group B): Early strength (3 days): The 3-day compressive strength of the experimental group (28.5 MPa) far exceeded that of the control group B (16.2 MPa), by nearly 76%. This solves the problem of low early strength in traditional alkali-activated geopolymers.

[0136] Later strength: The strength of the two groups was similar at 28 days and 90 days, but the experimental group still had a certain advantage, indicating that the present invention can guarantee its later performance while ensuring early strength.

[0137] Compared with the iron-free group (control group C): The experimental group showed superior strength compared to the control group (C) at all age stages. For example, the experimental group's 3-day compressive strength was 191% higher than that of the control group (C), and the experimental group's 28-day compressive strength was still 60% higher than that of the control group (C).

[0138] 1.6 Summary: This invention relates to a slag powder-fly ash cementitious material using ferric silicate as an activator. It combines the advantages of high early-stage strength of traditional cement and high late-stage strength of traditional geopolymers, while overcoming the latter's slow early-stage strength development. Its superior performance stems directly from the high efficiency and synergistic effect of the "acidic degradation-sulfate reconstruction" composite activating system composed of ferric silicate and gypsum.

[0139] This material not only has better mechanical properties than ordinary cement, but also has better early strength than traditional alkali-activated materials.

[0140] Experimental Example 2 (Workability and Condensation Time Test): 2.1 Experimental Objective The standard consistency water requirement and setting time of the cementitious material of this invention were determined and compared with those of benchmark cement and traditional alkali-activated materials to evaluate its workability, thereby demonstrating the advantages of the material of this invention in terms of low water requirement and reasonable setting time, thus possessing excellent construction adaptability.

[0141] 2.2 Experimental Materials and Grouping:

[0142] 2.3 Test Procedure (Based on GB / T 1346-2011) 2.3.1 Determination of standard consistency water requirement: Instrument preparation: Adjust the Vicat apparatus so that the pointer is at zero when the test rod touches the glass plate.

[0143] Mixing: Weigh 500g of the cementitious material to be tested and pour it into the mixing pot. Use the fixed water volume method for preliminary estimation, and then adjust the water volume around the estimated value. Use a cement paste mixer to complete the mixing according to the standard procedure (low speed 120s, stop for 15s, then high speed 120s).

[0144] Mold loading and testing: Immediately pour the prepared neat pulp into the mold placed on the glass plate. Use a knife to tamp, vibrate, and scrape off the excess pulp, then smooth the surface. Move the mold along with the glass plate to the Vicat apparatus, lower the test rod until it contacts the surface of the neat pulp, tighten the screw, and then suddenly loosen it, allowing the test rod to sink freely into the neat pulp.

[0145] Result determination: Record the distance between the test rod and the glass plate 30 seconds after the test rod stops sinking or is released. When the test rod sinks to a depth of 6mm ± 1mm, the consistency of the neat cement paste is the standard consistency, and the mixing water consumption at this point is the standard consistency water consumption (P), calculated as a percentage of the cement mass.

[0146] Each sample should be tested at least twice, and the average value should be taken.

[0147] 2.3.2 Determination of setting time: Instrument replacement: After completing the standard consistency test, immediately insert the paste knife into the mold several times, then gently vibrate it several times and scrape it smooth. Then immediately place the mold into a moisture curing chamber for curing.

[0148] Initial setting test: Record the time from the start of water addition. The first test should begin 30 minutes after curing. During the test, replace the test rod of the Vicat apparatus's initial setting needle (coarse needle). Remove the mold from the moisture curing chamber and place it under the needle, lowering the needle to contact the paste surface. Tighten the screw and then suddenly loosen it, allowing the needle to sink freely and vertically into the paste.

[0149] Measurement frequency: Initially, measurements were taken every 5 minutes. As initial setting approached, measurements were taken every 2 minutes.

[0150] Initial setting determination: When the test needle sinks to 4mm ± 1mm ​​from the bottom plate, the cement has reached the initial setting state. Record this time as the initial setting time.

[0151] Final setting test: After the initial setting test is completed, immediately rotate the mold along with the slurry 180° so that the final setting surface is facing up, and then put it back into the curing box.

[0152] Replace the Vicat apparatus with a final coagulation needle (fine needle with a ring attachment). When the final coagulation is approaching, measure every 5-10 minutes.

[0153] Final setting determination: When the test needle sinks into the slurry by no more than 0.5 mm, it is considered to have reached the final setting state. Record this time, which is the final setting time.

[0154] 2.4 Experimental Data Table 2: Water Requirement and Setting Time for Standard Consistency in Each Test Group

[0155] 2.5 Experimental Conclusions and Data Analysis: 2.5.1 Standard consistency water requirement analysis: The water requirement of the experimental group (24.5%) was the lowest among all groups, even lower than that of the traditional alkali activation group (control group B, 25.0%) and the benchmark cement group (control group A, 27.0%).

[0156] This demonstrates that the material of this invention possesses excellent workability. The low water requirement is primarily due to the "ball effect" of the fly ash microspheres, which significantly improves the rheological properties of the slurry. The material system, after segmented grinding, has high bulk density, low porosity, and requires less filling water.

[0157] Low water demand can reduce the water-cement ratio when preparing concrete, directly improving the strength and durability of the final product, or achieving better fluidity with the same amount of admixtures.

[0158] 2.5.2 Condensation Time Analysis: Compared with control group A, the initial and final setting times of the experimental group (105 / 155 min) were both shortened by approximately 40 min compared to control group A (145 / 195 min). This indicates that the activation system of the present invention has higher reactivity, which can accelerate the construction progress, shorten the demolding time, and improve the formwork turnover rate.

[0159] Compared with control group B, the traditional alkali-activated material in control group B sets quickly (initial setting time 40 min), resulting in a very short construction window that easily leads to construction difficulties and quality accidents. In contrast, the setting time of control group B (105 / 155 min) is much longer than that of control group B, more than 2.5 times longer, leaving sufficient time for construction operations such as mixing, transportation, pouring, and vibration.

[0160] Compared to control group C: the slurry in the group without ferric silicate (control group C) hardly solidified within 6 hours, remaining in a soft plastic state. This demonstrates, from the opposite perspective, the core activating effect of ferric silicate. Without the acidic environment provided by ferric silicate to disrupt the glassy structure, the reaction cannot be effectively initiated, and the slurry cannot solidify and harden.

[0161] 2.5.3 Condensation Time Interval Analysis: The time interval from initial setting to final setting was approximately 45-50 minutes for each group, indicating that the rate of strength development was similar once setting began. The setting process in the experimental group was stable and controllable, with no abnormal slow or rapid setting phenomena.

[0162] 2.6 Summary This invention achieves a balance between low water demand and setting time in a slag powder-fly ash cementitious material using ferric silicate as an activator. The low water demand endows it with excellent rheological properties, which is beneficial for the formulation of high-performance concrete.

[0163] Its reasonable and controllable setting time (approximately 1.75-2.6 hours) makes it far more adaptable to construction than traditional alkali-activated materials that set too quickly, while also setting faster than ordinary cement, thus meeting the efficiency requirements of modern construction.

[0164] Test Example 3 (Durability Test - Resistance to Sulfate Attack): 3.1 Experimental Objective: In a simulated harsh sulfate erosion environment, the strength retention rate and morphological changes of the cementitious mortar specimens of the present invention were quantitatively tested after long-term immersion, and compared with the reference material to evaluate its long-term durability and demonstrate its inherent durability advantage due to its unique hydration products.

[0165] 3.2 Experimental Materials and Grouping: Experimental group: Materials of this invention; Control group A: Ordinary Portland cement PO 42.5 3.3 Experimental Procedure: 3.3.1 Specimen preparation: Prepare mortar specimens of 40mm × 40mm × 160mm with a mortar-to-sand ratio of 1:3 and a water-to-cement ratio of 0.5.

[0166] After molding, the molded product is cured in a standard curing chamber (20±1°C, RH>90%) for 24 hours before demolding.

[0167] Immediately after demolding, the specimens were placed in saturated lime water at (20±1)℃ and cured for 28 days.

[0168] 3.3.2 Initial Strength Test: After 28 days of curing, remove at least three specimens, dry the surface moisture, and immediately conduct flexural and compressive strength tests. The strength value is recorded as follows: (Initial strength).

[0169] 3.3.3 Immersion in corrosive environments: The remaining specimens were divided into two batches: Erosion group: Immersed in 5% (mass concentration) anhydrous sodium sulfate (Na2SO4) solution.

[0170] Baseline group: Immersed in pure water at 20±1℃ (to deduct the effect of normal age-related strength growth).

[0171] The soaking solution should be changed every 4 weeks to maintain a constant solution concentration.

[0172] The soaking container should be sealed with a lid and placed in a constant temperature water bath at 20±2℃ to prevent water evaporation and concentration changes.

[0173] 3.3.4 Long-term performance monitoring: After the preset soaking period (90 days (about 3 months) or 150 days (about 5 months)), at least 3 specimens were taken out from the erosion solution and pure water, respectively.

[0174] Wipe the surface dry with a damp cloth, first perform a flexural strength test, and then use the fractured specimen to perform a compressive strength test.

[0175] Record erosion group intensity Strength of the same period underwater reference group .

[0176] Carefully observe and record signs of deterioration such as peeling, cracking, and deformation on the surface of the specimen.

[0177] 3.3.5 Data Processing: The corrosion resistance coefficient (K) is a key indicator for evaluating resistance to sulfate attack, and is calculated using the following formula:

[0178] in, For the strength of the erosion group specimens, The strength of the underwater benchmark group of specimens of the same age is represented by K. K > 100% indicates that the strength is still increasing; K < 100% indicates that the strength has regressed, and the lower the value, the more severe the corrosion damage.

[0179] 3.4 Experimental Data Table 3: Test data on resistance to sulfate attack

[0180] 3.5 Experimental Conclusions and Data Analysis 3.5.1 Performance Degradation Comparison Analysis: Experimental group: After 150 days of long-term sulfate erosion, its corrosion resistance coefficient K remained at 102.2%, its strength did not decrease, and it was slightly higher than that of the water-cured specimens during the same period. This indicates that the material of this invention was not only not damaged by sulfate erosion, but its hydration reaction continued, and its structure continued to densify.

[0181] Control group A: Its corrosion resistance coefficient K decreased significantly with immersion time, from 91.8% after 90 days to 79.5% after 150 days, and the strength reduction was severe, indicating that the material structure had been substantially damaged.

[0182] 3.5.2 Mechanism Analysis: The deterioration of control group A stemmed from the large amount of highly alkaline calcium hydroxide (CH) and high calcium-to-silica CSH gel produced during its hydration. CH reacts with sulfate to form expansive gypsum, while the aluminum phase in the CSH gel reacts with sulfate to form even more destructive secondary ettringite. Internal expansion stress leads to cracking and crumbling.

[0183] The superior resistance of the experimental materials of this invention stems from their hydration product system: Low alkalinity environment: The hydrolysis of ferric silicate provides a slightly acidic environment, resulting in low alkalinity of the system and almost no generation of CH, thus eliminating the reaction substrate for gypsum formation.

[0184] Stable hydration products: Its core hydration product is a C-(A)-SH gel with a low calcium-to-silicon ratio (C / S), which has a more stable structure, low aluminum content, and is not prone to destructive reactions with sulfates.

[0185] Stability of ettringite: Under conditions of sufficient gypsum and active aluminum source, the ettringite generated in the early stages of this invention is stable. Furthermore, the introduction of limestone powder can generate aluminocarbonate, further stabilizing the early structure and preventing its conversion to monosulfide calcium sulfoaluminate (AFm).

[0186] 3.5.3 Surface morphology verification: After 150 days, the experimental group specimens had clear edges and intact surfaces, while the control group specimen A showed signs of surface brittleness and erosion. The macroscopic phenomena were highly consistent with the mechanical data, further confirming the above analysis.

[0187] 3.6 Summary The sulfate resistance test obtained comparative data with significant differences through accelerated simulation of long-term immersion.

[0188] The experimental results fully demonstrate that: The slag powder-fly ash cementitious material with ferric silicate as an activator provided by this invention has the characteristics of generating low alkalinity and high stability products due to its hydration chemistry, which gives it inherent and excellent resistance to sulfate attack.

[0189] Experimental Example 4 (Heat of Hydration Analysis): 4.1 Experimental Objective This experiment used isothermal calorimetry to quantitatively monitor the heat flow rate and cumulative heat release of the cementitious material of this invention in the early stage of hydration (72 hours), and compared it with a reference cement. The purpose was to demonstrate from the perspective of hydration kinetics that the material of this invention has the characteristics of slow hydration heat release and low total heat release, providing key data support for its application in large-volume concrete engineering and effectively suppressing the risk of temperature stress cracking.

[0190] 4.2 Experimental Materials and Grouping Experimental group: Materials of this invention; Control group A: Ordinary Portland cement PO 42.5; 4.3 Test Procedure 4.3.1 Instrument Preparation: An isothermal conduction calorimeter was used, with the test chamber temperature preset and stabilized at 20.0 ± 0.1 °C.

[0191] Prepare dedicated ampoules and reference bottles, ensuring they are clean and dry.

[0192] 4.3.2 Sample preparation: Accurately weigh 5.000 ± 0.005 g of the dry gelling material powder to be tested and place it in a sample ampoule.

[0193] Using a precision pipette, weigh out the appropriate amount of deionized water (2.500 g) at a water-to-gel ratio (W / B) of 0.5 and place it in a small plastic bottle (syringe) with a cap.

[0194] Place the syringe filled with good water into the fixed position inside the calorimeter.

[0195] 4.3.3 Initial Equilibrium: Place the sample ampoules containing the dry powder and the reference ampoules together into the test chamber of the calorimeter.

[0196] Equilibrate at 20°C for at least 30 minutes until the thermal flux baseline stabilizes to eliminate thermal interference introduced by operation.

[0197] 4.3.3 Injection and Measurement: The instrument software remotely controls the injection of water from the syringe into the sample ampoule, and uses the built-in micro stirrer to quickly stir (about 60 seconds) to ensure initial uniform mixing.

[0198] From the moment water is injected, the data acquisition system automatically and continuously records the heat flow changes of the sample chamber relative to the reference chamber at a high frequency (e.g., 1 point / minute), and monitors it continuously for 72 hours.

[0199] The instrument software automatically integrates the heat flow curve and calculates the cumulative heat release (J / g).

[0200] Repeatability: Each sample group was tested at least twice to ensure the repeatability of the results. The final data were averaged.

[0201] 4.4 Experimental Data: Table 4: Comparison of Key Characteristics of Heat of Hydration (Test conditions: 20°C, W / B=0.5)

[0202] 4.5 Experimental Conclusions and Data Analysis: 4.5.1 Analysis of heat release rate: Initial wetting peak: The initial peak value of the experimental group (120 mW / g) was much lower than that of the control group A (250 mW / g). This indicates that the initial dissolution and hydration reaction intensity on the surface of the dry powder particles of the present invention is significantly lower than that of silicate cement, and the initial chemical activity is controllable.

[0203] Main exothermic peak: The main peak of the experimental group not only appeared about 6 hours later, but its peak intensity (3.8 mW / g) was also 32% lower than that of the control group A (5.6 mW / g). This indicates that the hydration process of the material of the present invention is more gradual and mild, avoiding concentrated exothermic reactions.

[0204] 4.5.2 Total heat release analysis: During the 72-hour period, the cumulative heat release in the experimental group was 245 J / g, while that in the control group A was 355 J / g, a decrease of approximately 31%. Lower heat release significantly reduces the internal temperature rise of the gelation system under adiabatic or large-volume conditions.

[0205] 4.5.3 Mechanism Analysis: The exothermic characteristics of control group A are due to the rapid dissolution and high hydration activity of its clinker minerals (C3S, C3A).

[0206] The exothermic characteristics of the experimental materials of this invention are determined by their excitation reaction mechanism: Differences in reaction pathways: Its hydration is a solid-phase reaction activation-dissolution-repolymerization process between activators (ferric silicate, gypsum) and active glass (slag, fly ash), which is inherently slower than the direct hydrolysis and dissolution of OPC clinker minerals.

[0207] Lack of highly exothermic phases: There are no instantaneously highly exothermic minerals such as C3A and C3S in the system.

[0208] Slightly acidic environment: The microenvironment provided by the hydrolysis of ferric silicate may inhibit the rapid exothermic reaction to some extent.

[0209] 4.6 Summary The hydration heat analysis experiment obtained clear and repeatable data through high-precision isothermal calorimetry.

[0210] The experimental results fully demonstrate that: The slag powder-fly ash cementitious material with ferric silicate as an activator provided by this invention has the significant characteristics of a slow exothermic rate, a delayed exothermic peak, and a low total heat release during its hydration process.

[0211] This characteristic is inherent in its physicochemical properties based on industrial solid waste and a unique composite activator. The lower exothermic level means that in large-volume concrete components, the core temperature peak caused by the accumulation of heat of hydration will be significantly reduced, thereby reducing the internal and external temperature difference and the resulting thermal stress, and effectively suppressing the formation of temperature cracks.

[0212] In summary, this performance advantage, combined with the high strength and high durability demonstrated in the aforementioned test examples, constitutes the core competitive advantage and innovation of the present invention in the application of large-volume concrete projects (such as dams, foundation slabs, bridge piers, etc.) that require low heat and low cracking risk, reflecting its important industrial practical value.

[0213] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in the present invention, and these should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be defined by the scope of the claims.

Claims

1. A slag powder-fly ash cementitious material using ferric silicate as an activator, characterized in that, Composed of the following components by weight percentage Composition: Slag powder: 30-50%; Gypsum: 2-15%; Fly ash: 15-20%; Slag powder: 10-15%; Limestone powder: 10-15%; Ferric silicate: 3-8%; The sum of the weight percentages of each component is 100%.

2. The slag powder-fly ash cementitious material using ferric silicate as an activator according to claim 1, characterized in that, Composed of the following components by weight percentage composition: Slag powder: 40%; Gypsum: 10%; Fly ash: 19%; Slag powder: 10%; Limestone powder: 15%, ferric silicate: 5%.

3. The slag powder-fly ash cementitious material with ferric silicate as an activator according to claim 1, characterized in that: The slag powder is obtained by grinding granulated blast furnace slag, and its specific surface area is not less than 400 m². 2 / kg, density is 2.8-3.0 g / cm³ 3 .

4. The slag powder-fly ash cementitious material with ferric silicate as an activator according to claim 1, characterized in that: The gypsum is any one or a combination of two of desulfurized gypsum and phosphogypsum, with a crystal water content of not less than 15% and an SO3 content of ≥35%.

5. The slag powder-fly ash cementitious material with ferric silicate as an activator according to claim 1, characterized in that: The slag powder is made by grinding circulating fluidized bed boiler slag, with a total SiO2+Al2O3+Fe2O3 content of not less than 70% and a moisture content of not more than 1%.

6. The slag powder-fly ash cementitious material with ferric silicate as an activator according to claim 1, characterized in that: The limestone powder contains no less than 85% CaCO3 and has a fineness Dv50 of no more than 20μm.

7. The slag powder-fly ash cementitious material with ferric silicate as an activator according to claim 1, characterized in that: The iron silicate mentioned is an industrial by-product iron silicate with a FeSiO3 content of not less than 90% and a particle size D90 ≤ 45μm.

8. A method for preparing a slag powder-fly ash cementitious material using ferric silicate as an activator, characterized in that, Includes the following steps: S1. Raw material pretreatment and classification: S1.1 Dry the slag powder and furnace slag powder at 100-110℃ until the moisture content is <1.0%, and then classify them by air classifier, and select particles with a particle size Dv50 of 15-25μm as the main material A; S1.2 After drying the gypsum at a low temperature of 60-70℃ until the moisture content is less than 5%, place it together with ferrosilicon in a vibrating screen and mix it at a frequency of 200-300 times / min for 5-10 minutes to form activator composite material B; S2. Segmented energy-optimized grinding: S2.1 First stage coarse grinding and activation: The main material A obtained in step S1.1 and the activator composite material B, accounting for 60%-80% of the total weight, are fed into a high-energy ball mill. Under the conditions of mill speed of 28-32 r / min, ball-to-material ratio of 6:1, and filling rate of 30%, grinding is carried out for 18-22 min to obtain a specific surface area of ​​270-290 m². 2 Intermediate C per kg; S2.2 Second Stage Fine Grinding Integration: Intermediate C, fly ash, limestone powder, and the remaining activator composite material B are fed into a high-efficiency vortex classifier vertical mill, with a system air volume of 5500-6500 m³ / h. 3 Compound grinding is carried out under the conditions of 280-320 r / min for classifier, with the outlet temperature controlled not to exceed 75℃, and the total grinding time 35-45 min, until the specific surface area of ​​the final product reaches 350-360 m². 2 / kg, and the particle size distribution Span value [(Dv90-Dv10) / Dv50] is less than 1.8, to obtain semi-finished product D; S3. Controllable hydration activation aging: The semi-finished product D is transported to an aging chamber with humidity control and aged for 36-48 hours at a temperature of 38-42℃ and a relative humidity of 65-75%. During this period, compressed air is used to pulse-turn every 12 hours, with a turning air pressure of 0.15-0.25MPa and each turning lasting for 3-5 minutes, finally obtaining the gelling material.

9. The feature of claim 8 is that: the grinding media used in the high-energy ball mill in step S2.1 are chromium alloy steel balls with diameters of Φ10mm, Φ15mm and Φ20mm mixed in a mass ratio of 3:5:

2.

10. The method for preparing a slag powder-fly ash cementitious material using ferric silicate as an activator according to claim 8, characterized in that: In step S2.2, the temperature of the material exiting the mill is controlled by spraying atomized water. The amount of atomized water added is 0.5%-1.0% of the total weight of the material.

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