Super-high early-strength special cementitious material and preparation method thereof

Abstract

The application discloses a kind of super-high early-strength special cementitious materials and preparation method thereof, the cementitious material is made of silicate cement clinker and gypsum grinding, and the mortar compressive strength of cementitious material satisfies: 1d≥20MPa, 3d≥38MPa, 28d≥58MPa.Silicate cement clinker, C3S total mass ratio is ≥65%, and M3 type C3S accounts for the mass ratio of all C3S≥65%.Silicate cement clinker is prepared by raw material and M3 type C3S seed crystal by high-temperature calcination.The application realizes super-high early-strength and stable growth of later strength by M3 type C3S seed crystal induction and complex mineralizer cooperation, directional enrichment high-activity M3 type C3S crystal, can satisfy the construction demand of full-scene steam-free curing.

Description

Technical Field

[0001] This invention relates to the field of cement-based cementitious materials technology, specifically to an ultra-high early strength special cementitious material and its preparation method. Background Technology

[0002] With the rapid development of modern infrastructure projects such as prefabricated buildings, wind power foundations, and precast pipe piles, and With the increasing prevalence of specialized engineering scenarios such as emergency road repairs, construction during low-temperature seasons, emergency tunnel reinforcement, and rapid port restoration, the market is placing higher demands on the early strength, setting speed, and ease of construction of cement-based cementitious materials. Engineering practice urgently requires a special cementitious material that can achieve "no steam curing required, rapid hardening and early strength, and stable performance" to shorten construction cycles and reduce energy consumption.

[0003] Currently, the 1-day compressive strength of ordinary Portland cement (OPC) is typically only 10-15 MPa. Its early strength development is slow and cannot meet the needs of rapid construction. It must be accompanied by high-temperature steam curing or autoclaving processes, which leads to high energy consumption, carbon emissions and equipment investment.

[0004] To improve early strength performance, existing technologies mainly adopt the following modification paths, but all of them have obvious defects: (1) Increasing the content of tricalcium aluminate (C3A): This will lead to concentrated hydration heat, poor volume stability of the hardened body in the later stage, and easy cracking and durability problems. (2) Adding chemical early strength agents: This may cause steel corrosion or disordered crystal form of hydration products, and generally results in early strength reaching the standard, later strength shrinkage, uneven hydration, and shortened service life of components. (3) Ultrafine grinding: This has extremely high energy consumption, high cost, and limited strength improvement and poor performance stability.

[0005] Meanwhile, existing modification technologies suffer from problems such as crude component ratios and limited ion modification, resulting in weak application scenarios. They cannot simultaneously meet the diverse construction needs of prefabricated products, pipe piles, and wind power hybrid towers, and are difficult to adapt to the integrated use requirements of high-end infrastructure projects, which require maintenance-free operation, ultra-high early strength, high strength, and high stability.

[0006] Core mineralogical studies have shown that tricalcium silicate (C3S) is the core mineral determining cement strength. Among them, the M3 crystal form of C3S is characterized by numerous lattice defects, low hydration activation energy, and rapid early hydration rate, making it an ideal crystal form for achieving ultra-high early strength. However, existing technologies struggle to directionally and efficiently enrich highly active M3-type C3S in industrial clinker, and there is a lack of a comprehensive crystal form control scheme from raw meal preparation to clinker cooling.

[0007] Therefore, developing a special cementitious material with controllable crystal form, excellent early strength, stable later strength, and the ability to achieve steam curing-free operation is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides an ultra-high early strength special cementitious material and its preparation method.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention provides an ultra-high early strength special cementitious material, which is made by grinding silicate cement clinker and gypsum powder, wherein the silicate clinker does not contain any early strength additives; The compressive strength of the mortar of the cementitious material meets the following requirements: 1d≥20MPa, 3d≥38MPa, 28d≥58MPa; The mineral composition of silicate cement clinker meets the following requirements: C3S accounts for ≥65% of the total mass, of which M3 type C3S accounts for ≥65% of the total mass of C3S.

[0010] Furthermore, the lime saturation coefficient of silicate cement clinker is KH=0.960±0.02, the silica ratio is SM=2.5±0.1, and the aluminum ratio is IM=1.7±0.1; the f-CaO content in silicate cement clinker is ≤2.0%.

[0011] Furthermore, silicate cement clinker contains the following characteristic chemical components by mass fraction: alkali content 0.6~1.0%, MgO content 1.35~1.50%, F - Content 0.15~0.20%, P2O5 content 0.20~0.25%, SO3 content 0.8~1.2%.

[0012] Furthermore, silicate cement clinker is prepared by high-temperature calcination of raw meal and M3 type C3S seed crystals. The raw meal consists of the following components by mass percentage: 78-85% calcium raw materials, 6-10% silica raw materials, 2-8% aluminum raw materials, 0.5-3.0% iron raw materials, 3-6% composite mineralizer, and M3 type C3S seed crystals account for 0.5%-2% of the total mass of the raw meal, and are added externally.

[0013] Furthermore, the calcareous raw material is a mixture of limestone and high-alkali, high-sulfur white mud; the siliceous raw material is selected from sandstone or silica; the aluminous raw material is a mixture of high-sulfur, high-alumina lithium slag and high-sulfur slag; the ferrous raw material is selected from copper slag or sulfuric acid slag; and the composite mineralizer is a mixture of yellow phosphorus slag and fluorite tailings.

[0014] Furthermore, in the composite mineralizer, yellow phosphorus slag accounts for 1.0 to 4.0% of the total mass of raw meal, and fluorite tailings account for 0.5 to 3.0% of the total mass of raw meal.

[0015] Furthermore, the calcareous raw material is a mixture of limestone and high-alkali, high-sulfur white mud in a mass ratio of 5:1, with the high-alkali, high-sulfur white mud containing 0.5-1.5% SO3 and 0.5-1.0% alkali; the aluminous raw material is a mixture of high-sulfur, high-aluminum lithium slag and high-sulfur cave slag in a mass ratio of 1:2, with the high-sulfur, high-aluminum lithium slag containing 1.0%-6.0% SO3 and 20-30% Al2O3, and the high-sulfur cave slag containing 0.5%-4.0% SO3.

[0016] In this invention, the raw materials contain phosphorus (P source) from yellow phosphorus slag, fluorite tailings from fluorite tailings from fluorite tailings from fluorite tailings from fluorite tailings, and sulfur (S source) from high-alkali, high-sulfur white mud, high-sulfur, high-alumina lithium slag, and high-sulfur cave slag from the raw materials themselves. These three elements together constitute a PFS-assisted mineralization system. During the calcination of silicate cement clinker, P, F, and S ions work synergistically to lower the liquid phase formation temperature and viscosity, promoting the full development of C3S crystals at lower temperatures. Simultaneously, ion doping further optimizes the C3S crystal lattice structure and enhances its hydration activity. The P, F, and S elements are introduced from the raw materials themselves, eliminating the need for additional S-containing mineralizers.

[0017] Furthermore, the M3 type C3S seed crystal is a high-purity nano-seed crystal or a low-cost alternative seed crystal; The purity of the high-purity nanocrystal seeds is >95%, the mass percentage of M3-type C3S is >90%, the particle size is 50~200nm, and the high-purity nanocrystal seeds account for 0.5%~1.5% of the total mass of the raw material; The low-cost alternative seed crystal is M3-type C3S enriched ultrafine powder obtained by ultrafine grinding of silicate cement clinker. The total mass of C3S in the ultrafine powder is ≥65%, the mass ratio of M3-type C3S to all C3S is ≥65%, the particle size is 0.2~0.5μm, and the ultrafine powder accounts for 1.0%~2.0% of the total mass of raw meal.

[0018] This invention provides a low-cost alternative seed crystal material for reuse after the silicate cement clinker has been ultrafinely ground. Specifically, it utilizes the highly active M3-type C3S crystals already enriched in the previous batch of silicate cement clinker, grinding them to submicron level and using them as seed crystals for the next batch of raw materials, providing a heterogeneous nucleation substrate for the formation of M3-type C3S. Since the low-cost alternative seed crystal and the clinker are different physical forms of the same substance (the seed crystal is a 0.2~0.5μm ultrafine powder, while the final clinker is a conventional powder with a specific surface area of ​​350±10m² / kg), this reuse does not introduce new impurity components and can completely replace high-purity nano-seed crystals, achieving low-cost industrial continuous production.

[0019] Furthermore, high-purity nanocrystal seeds are prepared through the following steps: (1) Raw material ratio: Weigh CaCO3 and SiO2 in a molar ratio of 3:1, add 1.35% MgO and 1.0% α-Al2O3 of the total mass of CaCO3 and SiO2, and mix to obtain seed raw material powder; (2) Mixing and grinding: The seed crystal raw material powder was wet ball milled for 2 hours, and cooled once every 15 minutes at a speed of 500 rpm; after grinding, the resulting slurry was dried at 105℃ for 6 hours to obtain dried lumps; (3) High-temperature solid-phase calcination: The dried agglomerate was placed in a platinum crucible and calcined in two steps: the temperature was raised to 1000℃ at 8℃ / min and held for 60 min, and then raised to 1600℃ at 8℃ / min and held for 120 min. (4) Rapid cooling: After calcination, the crucible is rapidly cooled by directly blowing compressed air through it; (5) Ultrafine grinding: The cooled product is ultrafine ground by air jet mill to a particle size of 50~200nm to obtain the high-purity nano crystal seeds.

[0020] This invention employs a solid-state reaction method to prepare high-purity nanocrystal seeds. First, CaCO3 and SiO2 are weighed in a molar ratio of 3:1. This molar ratio corresponds to the theoretical calcium-silicon ratio of tricalcium silicate (C3S) (3CaO·SiO2). This proportion ensures the solid-state reaction proceeds fully towards C3S formation, yielding the maximum proportion of C3S crystals. Then, 1.35% MgO and 1.0% α-Al2O3 are added to the total mass of the above system. The 1.35% MgO is the decisive factor in ensuring the stable existence of C3S in the M3 crystal form, while the 1.0% α-Al2O3 assists in maximizing the formation of M3-type C3S; MgO... 2+ Al 3+ During the high-temperature solid-state reaction, the M3 crystals enter the C3S lattice, activating the crystal form and providing active sites, thus improving the hydration activity of the seed crystals. Then, wet ball milling ensures thorough mixing and refinement of the raw material powders, preventing premature reaction due to temperature rise during grinding; intermittent cooling avoids adverse effects of temperature rise on the raw material composition and structure. In the two-step calcination, the first step decomposes CaCO3 into highly active CaO and removes CO2; the second step allows CaO and SiO2 to fully generate C3S crystals through a solid-state reaction. Compressed air purging and rapid cooling "freeze" the M3 crystal form formed at high temperature to room temperature, preventing the M3 crystal form from transforming into a less active crystal form during slow cooling, and combining with Mg... 2+ Al 3+ The activation and stabilization effects on the M3 crystal form together ensure a high proportion of M3-type C3S in the seed crystals. Ultrafine grinding to nanoscale particle size using an air jet mill provides ample nucleation sites for the seed crystals during subsequent raw material calcination, lowering the free energy barrier for M3-type C3S crystal nucleation and inducing preferential growth of C3S in the clinker with the M3 crystal form.

[0021] A second aspect of this invention provides a method for preparing the above-mentioned ultra-high early strength special cementitious material, comprising the following steps: S1. The calcium-based raw materials, silica-based raw materials, aluminum-based raw materials, iron-based raw materials, and composite mineralizers are pretreated separately. The pretreatment includes drying, crushing, and grinding until the residue on a 0.08mm square-hole sieve is greater than 25%. S2. Weigh the pretreated raw materials and composite mineralizer according to the proportion, and add M3 type C3S seed crystals externally. Mix and grind until the residue on a 0.08mm square hole sieve is ≤18% to obtain a mixture. S3. The mixture is subjected to high-temperature calcination. The calcination process is as follows: the temperature is raised to 950℃ at a rate of 8~12℃ / min and held for 25~35min, then raised to 1450℃ and held for 30~45min to obtain calcined clinker. S4. Rapidly cool the calcined clinker to below 200°C at a rate of ≥80°C / min to obtain cooled clinker; S5. Grind the cooled clinker together with gypsum (5% by weight of the cooled clinker) until the specific surface area is 350±10m². 2 / kg, to obtain the ultra-high early strength silicate cementitious material.

[0022] This invention achieves homogenization, controls material fineness, and improves sinterability by mixing and grinding various raw materials, composite mineralizers, and M3-type C3S seed crystals. S3 is heated to 950℃ at a rate of 8-12℃ / min and held at that temperature to fully decompose the carbonates and release CO2; it rapidly passes through the 980-1050℃ crystal phase transformation sensitive range to avoid the formation of undesirable crystal forms; the temperature is further increased to 1450℃ and held for 30-45 minutes, allowing acidic oxides such as CaO and SiO2 to generate clinker minerals through solid-phase reaction and liquid-phase sintering. During this process, the seed crystals induce C3S to preferentially grow in the M3 crystal form, and sufficient holding ensures complete crystal development.

[0023] In this invention, S4 rapidly cools the clinker to below 200°C at a rate of ≥80°C / min, allowing the clinker to quickly cross the M3→M1 crystal phase transition temperature range. This prevents the highly active M3-type C3S formed at high temperatures from transforming into a less active crystal form during the slow cooling process, thus locking the M3 crystal form to room temperature and ensuring the early strength activity of the clinker. At the same time, it inhibits secondary crystallization and grain coarsening of C3S.

[0024] Compared with the prior art, the present invention has the following beneficial effects: 1. Superior Early Strength Performance: This invention significantly enhances the early hydration rate of cementitious materials by controlling the clinker's three ratios (temperature, viscosity, and hydration rate), incorporating M3-type C3S seed crystals to induce crystallization, and combining this with composite mineralizer doping and rapid quenching. The M3-type C3S seed crystals provide heterogeneous nucleation sites for C3S, lowering the crystallization barrier and preferentially inducing its precipitation, thus dominating directional nucleation. Composite mineralizer doping regulates liquid phase viscosity and ion migration rate, stabilizing the M3 crystal form and inhibiting its transformation to the M1 crystal form. Rapid quenching locks in the high-temperature stable M3 phase, solidifying the crystal structure. Through synergistic effects, highly active M3-type C3S is enriched, accelerating early hydration, significantly improving 1-day strength, and ensuring steady strength development in later stages, achieving a perfect balance between early strength and high strength.

[0025] 2. Achieves fully autoclaving-free construction, reducing costs and increasing efficiency, and promoting green and low-carbon practices: The cementitious material of this invention does not rely on complex curing processes such as high-temperature autoclaving and high-pressure autoclaving. Its enriched, highly active M3-type C3S has sufficient hydration driving force at room temperature, enabling rapid formation of CSH gel and a dense, hardened skeleton. No high-temperature autoclaving is required to activate hydration; natural curing at room temperature is sufficient to meet the strength requirements of various cement products and infrastructure components. Simultaneously, the clinker of this invention exhibits excellent early-strength characteristics, significantly advancing the demolding window for components, eliminating the autoclaving and settling process, reducing process waiting time, and shortening the overall product production cycle by more than 30%. It also eliminates the need for autoclaving equipment and energy investment, enabling autoclaving-free, green, large-scale production.

[0026] 3. Strong controllability of crystal form, excellent performance stability and durability: This invention innovatively adopts the core process of in-situ induced calcination of raw material crystal seeds + rapid quenching to lock crystals, precisely controlling the generation, development and retention of M3-type C3S crystals, fundamentally avoiding the problems of concentrated heat release during hydration, drying shrinkage cracking, and loose structure in traditional cement. Simultaneously, the synergistic modification of P, F, and S ions (where S is introduced from high-alkali, high-sulfur white mud, high-sulfur, high-alumina lithium slag, and high-sulfur slag itself) optimizes the C3S crystal form in the clinker, enhancing its hydration activity. During the hydration process, the synergistic doping of P, F, and S ions alters the morphology of CSH gel and the formation rate of ettringite, inhibiting the precipitation of coarse and harmful crystals, refining the hydration product grains, and reducing internal porosity, thereby constructing a continuous and dense hydration framework, optimizing the microstructure of the hardened slurry, improving the density and volume stability of the hardened body, effectively improving the long-term durability of components, and adapting to various harsh construction environments.

[0027] 4. High utilization rate of solid waste resources and wide adaptability of raw materials: This invention innovatively combines various industrial solid wastes and tailings such as high-alkali and high-sulfur white mud, high-sulfur and high-alumina lithium slag, high-sulfur cave slag, copper slag, yellow phosphorus slag, and fluorite tailings as raw materials to replace traditional natural mineral raw materials, significantly reducing mineral resource consumption. The solid waste resource utilization rate is high, the production cost is low, and the raw materials are highly adaptable to industrial solid wastes from different production areas, which facilitates large-scale industrial promotion and application.

[0028] 5. Strong adaptability to multiple scenarios and wide range of applications: This invention utilizes the ultra-high early strength performance of clinker itself, and can meet the demolding strength requirements of precast components without the addition of early strength agents or steam curing treatment. It can be directly adapted to the three major precast building material scenarios of precast cement products, wind power hybrid towers, and precast pipe piles (traditionally, these products are usually prepared by adding early strength agents to ordinary cement or steam curing). At the same time, it can meet the needs of special emergency projects such as road emergency repair, low temperature construction, tunnel emergency reinforcement, and port rapid repair. It has comprehensive applicable scenarios and extremely high market application value. Attached Figure Description

[0029] Figure 1 The image shows the XRD fitting results of the ultra-high early strength special cementitious material prepared in Example 1. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0031] In this embodiment of the invention, high-purity nanocrystal seeds are prepared in advance.

[0032] High-purity nano-M3-C3S seeds were prepared via a solid-state reaction method, as follows: (1) Raw material ratio: Weigh CaCO3 and SiO2 in a molar ratio of 3:1, add 1.35% MgO and 1.0% α-Al2O3 of the total mass of CaCO3 and SiO2, and mix to obtain seed raw material powder; (2) Mixing and grinding: The seed crystal raw material powder was wet ball milled for 2 hours, and cooled once every 15 minutes at a speed of 500 rpm; after grinding, the resulting slurry was dried at 105℃ for 6 hours to obtain dried lumps; (3) High-temperature solid-state calcination: The dried agglomerate was placed in a platinum crucible and calcined as follows: the temperature was increased to 1000℃ at 8℃ / min and held for 60min, and then increased to 1600℃ at 8℃ / min and held for 120min. (4) Rapid cooling: After calcination, the crucible is rapidly cooled by directly blowing compressed air through it; (5) Ultrafine grinding: The cooled product is ultrafine ground by air jet mill to a particle size of 50~200nm to obtain high-purity nano crystal seeds, which are then sealed and stored for later use.

[0033] Testing revealed that the prepared high-purity nano M3-C3S seed crystals had a purity of >95% and a mass percentage of M3-type C3S of >90%.

[0034] Example 1: This example uses high-purity nanocrystalline seeds and synergistic mineralizers to prepare ultra-high early strength special cementitious materials. The proportions of its silicate cement clinker (the percentages of each component are based on the total mass of raw meal) are as follows: 82% calcareous raw materials (including 68.33% limestone and 13.67% high-alkali and high-sulfur white mud, with a mass ratio of 5:1). Siliceous raw material (sandstone) 7.5%; Aluminum raw materials (of which high-sulfur, high-alumina lithium slag 1.5% and high-sulfur slag 3.0%, mass ratio = 1:2) 4.5%; Iron-based raw materials (copper slag) 1.5%; 4.5% composite mineralizer (of which 3.0% is yellow phosphorus slag and 1.5% is fluorite tailings); M3 type C3S seed crystals (high-purity nano-seed crystals) account for 1.5% of the total mass of raw materials and are added externally.

[0035] The preparation method of ultra-high early strength special cementitious materials is as follows: S1. The above-mentioned calcareous raw materials (limestone, high-alkali and high-sulfur white mud), siliceous raw materials (sandstone), aluminous raw materials (high-sulfur and high-alumina lithium slag, high-sulfur slag), iron raw materials (copper slag) and composite mineralizers (yellow phosphorus slag, fluorite tailings) are pretreated respectively. The pretreatment includes drying, crushing and grinding until the residue on a 0.08mm square hole sieve is greater than 25%. S2. Weigh the pretreated raw materials (calcareous raw materials, siliceous raw materials, aluminum raw materials, and iron raw materials), composite mineralizer, and M3 type C3S seed crystals (high-purity nano-seed crystals) according to the above proportions, mix and grind until the residue on a 0.08mm square hole sieve is ≤18%, and obtain the mixture. S3. The mixture is subjected to high-temperature calcination. The calcination process is as follows: the temperature is increased to 950℃ at a rate of 10℃ / min and held for 30min, and then increased to 1450℃ at a rate of 10℃ / min and held for 40min to obtain calcined clinker. S4. Rapidly cool the calcined clinker to below 200°C at a rate of ≥80°C / min to obtain cooled clinker; S5. Grind the cooled clinker together with gypsum (5% by weight of the cooled clinker) until the specific surface area is 350±10m². 2 / kg, to obtain ultra-high early strength silicate cementitious material.

[0036] Chemical analysis, phase analysis, and physical property testing were performed on the cementitious material obtained in Example 1. The test results showed that the total C3S content in the silicate cement clinker obtained in Example 1 was 76.5%, of which M3-type C3S accounted for 67.8% of the total C3S mass, and the f-CaO content was 1.95%. The clinker ratio values ​​met the following requirements: KH=0.960±0.02, SM=2.5±0.1, IM=1.7±0.1. Under standard curing conditions, the mortar's 1-day compressive strength was 24.6 MPa, its 3-day compressive strength was 42.3 MPa, and its 28-day compressive strength was 61.5 MPa. Example 2: This example uses a low-cost alternative to seed crystals and synergistic mineralizers to prepare ultra-high early strength special cementitious materials. The proportions of its silicate cement clinker (the percentages of each component are based on the total mass of raw meal) are as follows: 80% calcareous raw materials (of which limestone accounts for 66.67% and high-alkali and high-sulfur white mud accounts for 13.33%, with a mass ratio of 5:1). Silica raw material (silica) 9%; Aluminum raw materials (of which high-sulfur, high-aluminum lithium slag 2.0% and high-sulfur slag 4.0%, mass ratio = 1:2) 6%; Iron-based raw material (sulfuric acid slag) 1.0%; 4.0% composite mineralizer (of which 3.0% is yellow phosphorus slag and 1.0% is fluorite tailings); M3 type C3S seed crystals (low-cost alternative seed crystals) account for 1.2% of the total mass of raw materials and are added externally.

[0037] The preparation method of ultra-high early strength special cementitious materials is as follows: S1. The above-mentioned calcareous raw materials (limestone, high-alkali and high-sulfur white mud), siliceous raw materials (silica), aluminous raw materials (high-sulfur and high-alumina lithium slag, high-sulfur slag), iron raw materials (sulfuric acid slag) and composite mineralizers (yellow phosphorus slag, fluorite tailings) are pretreated respectively. The pretreatment includes drying, crushing and grinding until the residue on a 0.08mm square hole sieve is greater than 25%. S2. Weigh the pretreated raw materials (calcareous raw materials, siliceous raw materials, aluminum raw materials, and iron raw materials), composite mineralizer, and M3 type C3S seed crystals (low-cost alternative seed crystals) according to the above proportions, mix and grind until the residue on a 0.08mm square hole sieve is ≤18%, to obtain a mixture; S3. The mixture is subjected to high-temperature calcination. The calcination process is as follows: the temperature is increased to 950℃ at a rate of 10℃ / min and held for 30min, and then increased to 1450℃ at a rate of 10℃ / min and held for 40min to obtain calcined clinker. S4. Rapidly cool the calcined clinker to below 200°C at a rate of ≥80°C / min to obtain cooled clinker; S5. Grind the cooled clinker together with gypsum (5% by weight of the cooled clinker) until the specific surface area is 350±10m². 2 / kg, to obtain ultra-high early strength silicate cementitious material.

[0038] Testing revealed that the total C3S content in the silicate cement clinker obtained in Example 2 was 72.5%, of which M3-type C3S accounted for 66.5% of the total C3S by mass, and the f-CaO content was 1.55%. Under standard curing conditions, the mortar exhibited a 1-day compressive strength of 22.8 MPa, a 3-day compressive strength of 40.1 MPa, and a 28-day compressive strength of 59.8 MPa.

[0039] Comparative Example 1 differs from Example 1 only in that M3-C3S seed crystals are not added to the silicate cement clinker (i.e., the amount of M3-C3S seed crystals is 0), while the other proportions and preparation processes are the same as in Example 1.

[0040] Testing revealed that the total C3S content in the silicate cement clinker obtained in Comparative Example 1 was 63.5%, with M3-type C3S accounting for 52.3% of the total C3S mass, and the f-CaO content was 2.35%. Under standard curing conditions, the mortar exhibited a 1-day compressive strength of 16.2 MPa, a 3-day compressive strength of 30.5 MPa, and a 28-day compressive strength of 53.2 MPa.

[0041] Comparative Example 2 differs from Example 1 only in that no composite mineralizer is added to the raw meal of silicate cement clinker (i.e., the content of yellow phosphorus slag and fluorite tailings is 0), while the proportions of other raw materials and the preparation process are the same as in Example 1.

[0042] Testing revealed that the total C3S content in the silicate cement clinker obtained in Comparative Example 2 was 62.8%, with M3-type C3S accounting for 50.1% of the total C3S mass, and the f-CaO content was 2.85%. Under standard curing conditions, the mortar's 1-day compressive strength was 15.8 MPa, its 3-day compressive strength was 29.1 MPa, and its 28-day compressive strength was 51.5 MPa.

[0043] The mineral composition, f-CaO content, and mechanical property test results of the cementitious materials obtained in each embodiment and comparative example are summarized in Table 1.

[0044] Table 1 Performance test results of each embodiment and comparative example

[0045] As shown in Table 1, the total C3S content and the proportion of M3-type C3S in the cementitious materials obtained in Examples 1-2 of this invention are significantly higher than those in Comparative Example 1 without M3-type C3S seed crystals and Comparative Example 2 without composite mineralizer, while the free calcium oxide content is lower. Regarding mechanical properties, the 1-day, 3-day, and 28-day compressive strengths of Examples 1-2 are significantly better than those of Comparative Examples 1-2, indicating that M3-C3S seed crystals and composite mineralizer have a significant synergistic promoting effect on the formation and enrichment of M3-type C3S, and both are indispensable.

[0046] The phase composition of the cementitious material obtained in Example 1 was analyzed using X-ray diffraction, and quantitative phase analysis was performed using the Rietveld full-spectrum fitting method. Figure 1 The XRD patterns and full-spectrum fitting results show that the M3 type C3S content in the silicate cement clinker obtained in Example 1 is 51.9% (76.5% × 67.8%).

[0047] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention used to illustrate the technical solutions of the present invention, and are not intended to limit the invention, nor are they intended to limit the patent scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. That is to say, any changes or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but whose technical problems are still consistent with the present invention, should be included within the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields are similarly included within the patent protection scope of the present invention.

Claims

1. A special cementitious material with ultra-high early strength, characterized in that, It is made from silicate cement clinker and gypsum powder, and the silicate clinker does not contain any early strength admixtures; The compressive strength of the mortar of the cementitious material meets the following requirements: 1d≥20MPa, 3d≥38MPa, 28d≥58MPa; The mineral composition of silicate cement clinker meets the following requirements: C3S accounts for ≥65% of the total mass, of which M3 type C3S accounts for ≥65% of the total mass of C3S.

2. The ultra-high early strength special cementitious material according to claim 1, characterized in that, The lime saturation coefficient of silicate cement clinker is KH=0.960±0.02, the silica ratio is SM=2.5±0.1, and the aluminum ratio is IM=1.7±0.1; the f-CaO content in silicate cement clinker is ≤2.0%.

3. The ultra-high early strength special cementitious material according to claim 1, characterized in that, Silicate cement clinker contains the following characteristic chemical components by mass fraction: alkali content 0.6~1.0%, MgO content 1.35~1.50%, F - Content 0.15~0.20%, P2O5 content 0.20~0.25%, SO3 content 0.8~1.2%.

4. The ultra-high early strength special cementitious material according to claim 1, characterized in that, Silicate cement clinker is prepared by high-temperature calcination of raw meal and M3 type C3S seed crystals. The raw meal consists of the following components by mass percentage: 78-85% calcium raw materials, 6-10% silica raw materials, 2-8% aluminum raw materials, 0.5-3.0% iron raw materials, 3-6% composite mineralizer, and M3 type C3S seed crystals account for 0.5%-2% of the total mass of the raw meal, and are added externally.

5. The ultra-high early strength special cementitious material according to claim 4, characterized in that, The calcareous raw material is a mixture of limestone and high-alkali, high-sulfur white mud; the siliceous raw material is selected from sandstone or silica; the aluminous raw material is a mixture of high-sulfur, high-alumina lithium slag and high-sulfur cave slag; the ferrous raw material is selected from copper slag or sulfuric acid slag; and the composite mineralizer is a mixture of yellow phosphorus slag and fluorite tailings.

6. The ultra-high early strength special cementitious material according to claim 5, characterized in that, In the composite mineralizer, yellow phosphorus slag accounts for 1.0~4.0% of the total mass of raw meal, and fluorite tailings account for 0.5~3.0% of the total mass of raw meal.

7. The ultra-high early strength special cementitious material according to claim 5, characterized in that, The calcareous raw material is a mixture of limestone and high-alkali, high-sulfur white mud in a mass ratio of 5:

1. The high-alkali, high-sulfur white mud contains 0.5-1.5% SO3 and 0.5-1.0% alkali. The aluminous raw material is a mixture of high-sulfur, high-alumina lithium slag and high-sulfur cave slag in a mass ratio of 1:

2. The high-sulfur, high-alumina lithium slag contains 1.0%-6.0% SO3 and 20-30% Al2O3, while the high-sulfur cave slag contains 0.5%-4.0% SO3.

8. The ultra-high early strength special cementitious material according to claim 4, characterized in that, M3 type C3S seed crystals are high-purity nano-seed crystals or low-cost alternative seed crystals; The purity of the high-purity nanocrystal seeds is >95%, the mass percentage of M3-type C3S is >90%, the particle size is 50~200nm, and the high-purity nanocrystal seeds account for 0.5%~1.5% of the total mass of the raw material; The low-cost alternative seed crystal is M3-type C3S enriched ultrafine powder obtained by ultrafine grinding of silicate cement clinker. The total mass of C3S in the ultrafine powder is ≥65%, the mass ratio of M3-type C3S to all C3S is ≥65%, the particle size is 0.2~0.5μm, and the ultrafine powder accounts for 1.0%~2.0% of the total mass of raw meal.

9. The ultra-high early strength special cementitious material according to claim 8, characterized in that, High-purity nanocrystal seeds are prepared through the following steps: (1) Weigh CaCO3 and SiO2 in a molar ratio of 3:1, add 1.35% MgO and 1.0% α-Al2O3 of the total mass of CaCO3 and SiO2, and mix to obtain seed raw material powder; (2) The seed crystal raw material powder was wet ball milled for 2 hours, and cooled once every 15 minutes at a speed of 500 rpm; after milling, the resulting slurry was dried at 105℃ for 6 hours to obtain dried lumps; (3) Place the dried agglomerate in a platinum crucible and perform two-step calcination: raise the temperature to 1000℃ at 8℃ / min and hold for 60min, then raise the temperature to 1600℃ at 8℃ / min and hold for 120min. (4) After calcination, the crucible is rapidly cooled by directly blowing compressed air through it; (5) The cooled product is ultra-finely ground using an air jet mill to a particle size of 50~200nm to obtain the high-purity nano crystal seeds.

10. A method for preparing an ultra-high early strength silicate cementitious material as described in any one of claims 1-9, characterized in that, Includes the following steps: S1. The calcium-based raw materials, silica-based raw materials, aluminum-based raw materials, iron-based raw materials, and composite mineralizers are pretreated separately. The pretreatment includes drying, crushing, and grinding until the residue on a 0.08mm square-hole sieve is greater than 25%. S2. Weigh the pretreated raw materials and composite mineralizer according to the proportion, and add M3 type C3S seed crystals externally. Mix and grind until the residue on a 0.08mm square hole sieve is ≤18% to obtain a mixture. S3. The mixture is subjected to high-temperature calcination. The calcination process is as follows: the temperature is raised to 950℃ at a rate of 8~12℃ / min and held for 25~35min, then raised to 1450℃ and held for 30~45min to obtain calcined clinker. S4. Rapidly cool the calcined clinker to below 200°C at a rate of ≥80°C / min to obtain cooled clinker; S5. Grind the cooled clinker together with gypsum (5% by weight of the cooled clinker) until the specific surface area is 350±10m². 2 / kg, to obtain the ultra-high early strength silicate cementitious material.

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