A gradient self-activating low-carbon cement and a preparation method thereof

Abstract

This invention discloses a gradient self-excited low-carbon cement and its preparation method, comprising the following raw materials in parts by weight: 15-20 parts of early-age self-excited cementitious material with a particle size of 0.1-10 μm and a specific surface area of ​​1150-1250 m². 2 / kg, uniformity coefficient >1.1; 45-50 parts of middle-aged self-stimulating cementitious material, particle specific surface area 380-400m² 2 / kg, uniformity coefficient > 1.1, R 45μm Silica residue <5%; 20-25 parts of long-term self-activating cementitious material, particle specific surface area 480-550 m² 2 / kg, uniformity coefficient > 1.1, R 45μm Residue on sieve <2%; 10-15 parts of rheology-active material, particle specific surface area 240-300 m² 2 / kg, uniformity coefficient > 0.9, R 45μm The residue on the sieve is less than 40%. This invention achieves a gradient self-excitation effect from early age to long age, ensuring the mechanical properties of low-carbon cement throughout its entire service life.

Description

A gradient self-excited low-carbon cement and its preparation method Technical Field

[0001] This invention belongs to the field of cement preparation technology, and particularly relates to a gradient self-excited low-carbon cement and its preparation method. Background Technology

[0002] During cement production, the combustion of fossil fuels such as coal and the decomposition of limestone raw materials emit large amounts of carbon dioxide. Using blended materials to partially replace cement clinker and reducing the proportion of clinker in cement is one of the most effective technical means to reduce carbon emissions in the cement industry at present. At the same time, the preparation and application of low-clinker, low-carbon cement can also achieve large-scale, resource-based utilization of industrial waste, resulting in significant economic and social benefits.

[0003] However, due to the significant differences in grindability and reactivity of the various raw material components in low-clinker and low-carbon cement, the following problems still exist in their preparation and application:

[0004] (1) Currently, cement is still prepared by co-grinding clinker, gypsum, and admixtures. Among them, high-activity admixtures and clinker have poor grindability, while low-activity admixtures and gypsum have good grindability. This makes it difficult to grind high-activity admixtures and clinker into fine powder during co-grinding, and the reactivity cannot be fully utilized. Low-activity admixtures and gypsum are ground too finely, resulting in high water demand and poor performance of cement. This effect is further amplified in low-carbon cement with high admixture content, resulting in an unreasonable match between the particle size and cementitious activity of each raw material component in low-carbon cement, which limits the cementitious activity of clinker and high-activity admixtures.

[0005] (2) The activation of pozzolanic activity in cement blends depends on the strong alkaline environment formed by the hydration of cement clinker. However, the significant reduction in clinker content in low-carbon cement leads to insufficient alkalinity formed by early hydration of cement, making it difficult to fully activate the activity of blends. As a result, the pozzolanic reaction is suppressed, resulting in low early-age strength of low-carbon cement and slow strength development in the middle and long-age stages. The mechanical properties throughout the entire service life cannot be guaranteed, which seriously restricts the engineering application of low-carbon cement.

[0006] Therefore, there is an urgent need to develop a low-carbon cement with low clinker and its preparation method. By optimizing the matching of particle size and cementitious activity among different raw materials, the reactivity of clinker and admixtures can be fully utilized to significantly improve the early strength of low-carbon cement and promote the early, middle and long-term strength development of low-carbon cement. This is of great significance for expanding the application market of low-carbon cement and reducing carbon emissions in the cement industry. Summary of the Invention

[0007] To address the problems of limited reactivity of raw materials and slow strength development in existing low-carbon cement preparation processes, this invention provides a gradient self-activated low-carbon cement and its preparation method. Based on graded grinding technology, this invention optimizes the particle size distribution and gelling activity matching of cement raw materials, maximizing the gelling activity and synergistic activation reaction capacity of each cement component at different ages. This achieves a gradient self-activated effect from early to long age, ensuring the mechanical properties of low-carbon cement throughout its entire service life.

[0008] The present invention is achieved as follows: a gradient self-excited low-carbon cement, comprising the following raw materials in parts by weight: 15-20 parts of early-age self-excited cementitious material; 45-50 parts of middle-age self-excited cementitious material; 20-25 parts of long-age self-excited cementitious material; and 10-15 parts of rheology-active material.

[0009] In the above technical solution, preferably, the early-age self-activated cementitious material comprises silicate cement clinker, granulated blast furnace slag, and a particle modifier. The mass ratio of silicate cement clinker to granulated blast furnace slag is 1:3 to 1:5. The dosage of the particle modifier is 2 to 5% of the mass of silicate cement clinker in the early-age self-activated cementitious material. The particle size range of the early-age self-activated cementitious material is 0.1 to 10 μm, and the particle specific surface area is 1150 to 1250 m². 2 / kg, uniformity coefficient >1.1.

[0010] In the above technical solution, it is further preferred that the particle modifier is industrial grade diethanol monoisopropanolamine or diisopropylethylamine, with an effective ingredient content ≥85%.

[0011] In the above technical solution, preferably, the middle-aged self-activated cementitious material comprises silicate cement clinker and gypsum, the mass ratio of silicate cement clinker to gypsum is 93-97:3-7, and the particle specific surface area of ​​the middle-aged self-activated cementitious material is 380-400 m². 2 / kg, uniformity coefficient > 1.1, R 45μm Residue on sieve <5%.

[0012] In the above technical solution, preferably, the long-term self-activating cementitious material is one of fly ash, steel slag, furnace slag, phosphorus slag, lithium slag, carbide slag, and municipal solid waste incineration bottom ash, and the particle specific surface area of ​​the long-term self-activating cementitious material is 480-550 m². 2 / kg, uniformity coefficient > 1.1, R 45μm Residue on sieve <2%.

[0013] In the above technical solution, preferably, the rheology-active material is quartz sand or limestone, and the particle specific surface area of ​​the rheology-active material is 240-300 m². 2 / kg, uniformity coefficient > 0.9, R 45μm Residue on sieve <40%.

[0014] In the above technical solutions, preferably, the 3-day activity index of the early-age self-stimulating cementitious material is ≥100%; the 28-day activity index of the long-age self-stimulating cementitious material is 65% to 80%; and the rheologically active material has no activity requirement.

[0015] This invention provides a method for preparing the above-mentioned gradient self-excited low-carbon cement, comprising the following steps:

[0016] Step 1: Mix and homogenize the raw materials in the early-age self-excited cementitious material according to the specified ratio, grind them together, and classify and sort them to the target particle size;

[0017] The raw materials in the middle-aged self-activated cementitious material are mixed and homogenized in a limited proportion and then ground together to the target particle size.

[0018] Long-term self-initiated cementitious materials are individually ground to the target particle size;

[0019] The rheology-active materials are individually ground to the target particle size;

[0020] Step 2: Mix and homogenize early-age self-activated cementitious materials, middle-age self-activated cementitious materials, long-age self-activated cementitious materials and rheology-active materials in a predetermined ratio to prepare gradient self-activated low-carbon cement.

[0021] This invention proposes a novel design and preparation concept for low-carbon cement. By controlling particle size and cementitious activity, it prepares early-, mid-, and long-term self-activated cementitious materials in a graded manner, and constructs a gradient self-activated low-carbon cement system through matched optimization design. During its hydration process, this low-carbon cement initially relies on the vigorous hydration reaction of the early-age self-activated cementitious materials to rapidly develop early strength, compensating for the slow early strength development caused by low clinker content. Simultaneously, it releases a large number of silicon / aluminum tetrahedral units, increasing the early ion activity and supersaturation of the pore solution, promoting the nucleation and growth of hydration products, and stimulating the hydration reaction of the mid-age self-activated cementitious materials, accelerating the mid-term strength development of the low-carbon cement. This process continues, further increasing the alkalinity of the pore solution in the later stages of hydration, promoting the depolymerization of inert aluminosilicate tetrahedra in the long-age self-activated cementitious materials, synergistically stimulating the reaction of the long-age self-activated cementitious materials, strengthening the low-carbon cement matrix, achieving stable long-term strength growth, and improving the durability of cement-based materials.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0023] (1) Compared with ordinary silicate cement produced by traditional methods, the gradient self-excited low-carbon cement prepared by this invention can reduce clinker usage by 30-45% and reduce overall carbon emissions by 220-250 kg / t, resulting in significant economic and environmental benefits.

[0024] (2) The gradient self-excited low-carbon cement prepared by the present invention can achieve a 3-day compressive strength of 23.8-25.1 MPa, a 7-day compressive strength of 34.9-38.3 MPa, a 28-day compressive strength of 48.4-52.1 MPa, and a 90-day compressive strength of 55.9-60.4 MPa on the basis of significantly reducing clinker usage and overall carbon emissions. It has the mechanical property advantages of rapid early and mid-term strength development and stable long-term strength development, and solves the key problem of slow early strength development of low clinker cement.

[0025] (3) The gradient self-excited low-carbon cement prepared by the present invention introduces rheological active materials to broaden the particle size distribution of low-carbon cement and optimize the particle gradation. The water consumption for standard consistency of cement is reduced by 0.5% to 2.0% compared with ordinary silicate cement and by 4.0% to 5.5% compared with low clinker cement prepared by co-grinding. The workability of cement is significantly improved. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0027] Example 1:

[0028] Preparation of early-age self-excited cementitious materials: Silicate cement clinker, granulated blast furnace slag, and industrial-grade diethanol monoisopropanolamine were mixed and homogenized at a mass ratio of 1:3:0.02, then ground and graded to a particle size range of 0.1–10 μm and a particle specific surface area of ​​1200 m². 2 / kg;

[0029] Preparation of medium-aged self-excited cementitious materials: Silicate cement clinker and gypsum were mixed and homogenized at a mass ratio of 93:7, and then ground together until the particle specific surface area was 400 m². 2 / kg;

[0030] Preparation of long-term self-activated cementitious materials: Fly ash was separately ground to a particle specific surface area of ​​500 m². 2 / kg;

[0031] Preparation of rheology-active materials: Limestone was ground separately to a specific surface area of ​​250 m². 2 / kg;

[0032] Preparation of gradient self-excited low-carbon cement (raw materials in parts by weight): 15 parts of early-age self-excited cementitious material, 50 parts of middle-age self-excited cementitious material, 25 parts of long-age self-excited cementitious material and 10 parts of rheology-active material are thoroughly mixed and homogenized to obtain gradient self-excited low-carbon cement.

[0033] Example 2:

[0034] Preparation of early-age self-excited cementitious materials: Silicate cement clinker, granulated blast furnace slag, and industrial-grade diethanol monoisopropanolamine were mixed and homogenized at a mass ratio of 1:5:0.02, then ground and graded to a particle size range of 0.1–10 μm and a particle specific surface area of ​​1200 m². 2 / kg;

[0035] Preparation of medium-aged self-excited cementitious materials: Silicate cement clinker and gypsum were mixed and homogenized at a mass ratio of 95:5, and then ground together until the particle specific surface area was 380 m². 2 / kg;

[0036] Preparation of long-term self-activated cementitious materials: Steel slag was separately ground to a particle specific surface area of ​​480 m². 2 / kg;

[0037] Preparation of rheology-active materials: Limestone was ground separately to a specific surface area of ​​280 m². 2 / kg;

[0038] Preparation of gradient self-excited low-carbon cement (raw materials in parts by weight): 20 parts of early-age self-excited cementitious material, 45 parts of middle-age self-excited cementitious material, 20 parts of long-age self-excited cementitious material and 15 parts of rheology-active material are thoroughly mixed and homogenized to obtain gradient self-excited low-carbon cement.

[0039] Example 3:

[0040] Preparation of early-age self-excited cementitious materials: Silicate cement clinker, granulated blast furnace slag, and industrial-grade diethanol monoisopropanolamine were mixed and homogenized at a mass ratio of 1:5:0.05, then ground and graded to a particle size range of 0.1–10 μm and a particle specific surface area of ​​1250 m². 2 / kg;

[0041] Preparation of medium-aged self-activated cementitious materials: Silicate cement clinker and gypsum were mixed and homogenized at a mass ratio of 95:5, and then ground together until the particle specific surface area was 390 m². 2 / kg;

[0042] Preparation of long-term self-activated cementitious materials: The slag was separately ground to a particle specific surface area of ​​540 m². 2 / kg;

[0043] Preparation of rheology-active materials: Limestone was ground separately to a specific surface area of ​​240 m². 2 / kg;

[0044] Preparation of gradient self-excited low-carbon cement (raw materials in parts by weight): 17 parts of early-age self-excited cementitious material, 48 parts of middle-age self-excited cementitious material, 22 parts of long-age self-excited cementitious material and 13 parts of rheology-active material were thoroughly mixed and homogenized to obtain gradient self-excited low-carbon cement.

[0045] Example 4:

[0046] Preparation of early-age self-excited cementitious materials: Silicate cement clinker, granulated blast furnace slag, and industrial-grade diisopropylethylamine were mixed and homogenized at a mass ratio of 1:3:0.05, then ground and graded to a particle size range of 0.1–10 μm and a particle specific surface area of ​​1180 m². 2 / kg;

[0047] Preparation of medium-aged self-activated cementitious materials: Silicate cement clinker and gypsum were mixed and homogenized at a mass ratio of 95:5, and then ground together until the particle specific surface area was 390 m². 2 / kg;

[0048] Preparation of long-term self-activated cementitious materials: Fly ash was ground separately to a particle specific surface area of ​​540 m². 2 / kg;

[0049] Preparation of rheology-active materials: Quartz sand was separately ground to a specific surface area of ​​280 m². 2 / kg;

[0050] Preparation of gradient self-excited low-carbon cement (raw materials in parts by weight): 19 parts of early-age self-excited cementitious material, 46 parts of middle-age self-excited cementitious material, 22 parts of long-age self-excited cementitious material and 13 parts of rheology-active material were thoroughly mixed and homogenized to obtain gradient self-excited low-carbon cement.

[0051] Example 5:

[0052] Preparation of early-age self-excited cementitious materials: Silicate cement clinker, granulated blast furnace slag, and industrial-grade diisopropylethylamine were mixed and homogenized at a mass ratio of 1:3:0.02, then ground and graded to a particle size range of 0.1–10 μm and a particle specific surface area of ​​1230 m². 2 / kg;

[0053] Preparation of medium-aged self-excited cementitious materials: Silicate cement clinker and gypsum were mixed and homogenized at a mass ratio of 97:3, and then ground together until the particle specific surface area was 380 m². 2 / kg;

[0054] Preparation of long-term self-activated cementitious materials: Steel slag was separately ground to a particle specific surface area of ​​550 m². 2 / kg;

[0055] Preparation of rheology-active materials: Limestone was ground separately to a specific surface area of ​​240 m². 2 / kg;

[0056] Preparation of gradient self-excited low-carbon cement (raw materials in parts by weight): 16 parts of early-age self-excited cementitious material, 49 parts of middle-age self-excited cementitious material, 20 parts of long-age self-excited cementitious material and 15 parts of rheology-active material were thoroughly mixed and homogenized to obtain gradient self-excited low-carbon cement.

[0057] Example 6:

[0058] Preparation of early-age self-excited cementitious materials: Silicate cement clinker, granulated blast furnace slag, and industrial-grade diethanol monoisopropanolamine were mixed and homogenized at a mass ratio of 1:3:0.02, then ground and graded to a particle size range of 0.1–10 μm and a particle specific surface area of ​​1190 m². 2 / kg;

[0059] Preparation of medium-aged self-excited cementitious materials: Silicate cement clinker and gypsum were mixed and homogenized at a mass ratio of 95:5, and then ground together until the particle specific surface area was 400 m². 2 / kg;

[0060] Preparation of long-term self-activated cementitious materials: Fly ash was ground separately to a particle specific surface area of ​​550 m². 2 / kg;

[0061] Preparation of rheology-active materials: Quartz sand was separately ground to a specific surface area of ​​260 m². 2 / kg;

[0062] Preparation of gradient self-excited low-carbon cement (raw materials in parts by weight): 20 parts of early-age self-excited cementitious material, 48 parts of middle-age self-excited cementitious material, 22 parts of long-age self-excited cementitious material and 10 parts of rheology-active material are thoroughly mixed and homogenized to obtain gradient self-excited low-carbon cement.

[0063] Comparative Example 1 (Ordinary Portland Cement):

[0064] PO42.5 ordinary Portland cement conforming to GB175-2007 "General Portland Cement".

[0065] Comparative Example 2 (Preparation of low clinker cement by co-grinding):

[0066] By weight, 50 parts silicate cement clinker, 2.5 parts gypsum, 15 parts granulated blast furnace slag, 22.5 parts fly ash, and 10 parts limestone are ground together to a particle size distribution of 380 m² / g. 2 / kg, to produce low clinker cement.

[0067] Comparative Example 3 (Preparation of low clinker cement by co-milling with particle modifier):

[0068] By weight, 50 parts of silicate cement clinker, 2.5 parts of gypsum, 15 parts of granulated blast furnace slag, 22.5 parts of fly ash, 10 parts of limestone, and 0.01 parts of particle modifier are ground together to a particle specific surface area of ​​380 m². 2 / kg, to obtain low clinker cement with added particle modifier.

[0069] The cements prepared in Examples 1 to 6 and Comparative Examples 1 to 3 were subjected to performance tests. The 3-day, 7-day, 28-day, and 90-day flexural and compressive strengths of the cement were tested according to GB / T17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)". The standard consistency water requirement, setting time, and soundness of the cement were tested according to GB / T1346-2011 "Test Method for Standard Consistency Water Requirement, Setting Time, and Soundness of Cement". The test results are shown in Table 1.

[0070] Table 1 Cement performance data

[0071]

[0072]

[0073] As shown in Table 1, the gradient self-excited low-carbon cement prepared by this invention can achieve a 3-day compressive strength of 23.8–25.1 MPa, a 7-day compressive strength of 34.9–38.3 MPa, a 28-day compressive strength of 48.4–52.1 MPa, and a 90-day compressive strength of 55.9–60.4 MPa, while significantly reducing clinker usage and overall carbon emissions. It combines the advantages of rapid early and mid-term strength development with stable long-term strength development, solving the key problem of slow early strength development in low-clinker cement. Furthermore, the gradient self-excited low-carbon cement prepared by this invention introduces rheologically active materials to broaden the particle size distribution and optimize particle gradation. The standard consistency water requirement is reduced by 0.5%–2.0% compared to ordinary silicate cement, by 4.0%–5.5% compared to low-clinker cement prepared by co-milling, and by 3.3%–4.8% compared to low-clinker cement prepared by co-milling with particle modifiers. The workability of the cement is significantly improved.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. 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. Such 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.

Claims

1. A gradient self-excited low-carbon cement, characterized in that: The raw materials include the following parts by weight: 15-20 parts of early-age self-activated cementitious material; 45-50 parts of middle-age self-activated cementitious material; 20-25 parts of long-age self-activated cementitious material; and 10-15 parts of rheology-active material. The early-age self-activated cementitious material comprises silicate cement clinker, granulated blast furnace slag, and a particle modifier. The mass ratio of silicate cement clinker to granulated blast furnace slag is 1:3 to 1:5, and the particle modifier dosage is 2-5% of the mass of silicate cement clinker in the early-age self-activated cementitious material. The particle size range of the early-age self-activated cementitious material is 0.1-10 μm, and the particle specific surface area is 1150-1250 m². 2 / kg, 3d activity index ≥100%; the particle modifier is industrial grade diethanol monoisopropanolamine or diisopropylethylamine; the middle-aged self-activated cementitious material comprises silicate cement clinker and gypsum, with a mass ratio of silicate cement clinker to gypsum of 93~97:3~7; the particle specific surface area of ​​the middle-aged self-activated cementitious material is 380~400 m² / kg. 2 / kg; the long-term self-activating cementitious material is one of fly ash, steel slag, furnace slag, phosphorus slag, lithium slag, carbide slag, and municipal solid waste incineration bottom ash; the particle specific surface area of ​​the long-term self-activating cementitious material is 480~550m². 2 / kg, 28d activity index of 65%~80%; the rheologically active material is quartz sand or limestone; the rheologically active material has no activity requirement, and the particle specific surface area of ​​the rheologically active material is 240~300m². 2 / kg.

2. The gradient self-excited low-carbon cement according to claim 1, characterized in that: The uniformity coefficient of early-age self-excited cementitious materials is >1.

1.

3. The gradient self-excited low-carbon cement according to claim 1, characterized in that: The effective ingredient content of the particulate modifier is ≥85%.

4. The gradient self-excited low-carbon cement according to claim 1, characterized in that: The uniformity coefficient of middle-aged self-activated cementitious materials is >1.1, R 45μm Residue on sieve <5%.

5. The gradient self-excited low-carbon cement according to claim 1, characterized in that: The uniformity coefficient of long-term self-activated cementitious materials is >1.1, R 45μm Residue on sieve <2%.

6. The gradient self-excited low-carbon cement according to claim 1, characterized in that: The uniformity coefficient of the rheologically active material is >0.9, R 45μm Residue on sieve <40%.

7. A method for preparing gradient self-excited low-carbon cement according to any one of claims 1-6, characterized in that: Includes the following steps: Step 1: Mix and homogenize all raw materials in the early-age self-activated cementitious material according to a specified ratio, grind them together, and classify them to the target particle size; mix and homogenize all raw materials in the middle-age self-activated cementitious material according to a specified ratio and grind them together to the target particle size; grind the long-age self-activated cementitious material separately to the target particle size; grind the rheology-active material separately to the target particle size; Step 2: Mix and homogenize the early-age self-activated cementitious material, middle-age self-activated cementitious material, long-age self-activated cementitious material, and rheology-active material according to a predetermined ratio to prepare gradient self-activated low-carbon cement.

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