Alkali-free activator high-strength solid waste-based cement and preparation method thereof

Abstract

The application provides a kind of alkali-free activator high-strength solid waste-based cement and a preparation method thereof, raw materials are Portland cement clinker 18-24 parts, wide distribution superfine mineral powder 75-80 parts, gypsum 1-1.5 parts; the characteristic particle size value De of wide distribution superfine mineral powder is less than 7.5 μm, and the uniformity coefficient n value is less than 0.9. The application uses wide distribution superfine mineral powder, uses the air-charged pressurized mixing method, and under the condition of not using alkali activator, the mineral powder incorporation amount is greater than or equal to 75%, which significantly increases the mineral powder addition amount, and each performance meets the requirements of ordinary Portland cement. The application solves the problems of ordinary solid waste-based cement, such as dependence on chemical activator to improve strength, low mineral powder incorporation amount, and unsuitable setting time and strength for construction environment. While effectively improving the utilization efficiency of mineral powder, the application can ensure that each performance of the alkali-free activator high-strength solid waste-based cement meets the current Portland cement specification.

Description

Technical Field

[0001] This invention relates to the field of building materials, specifically to a high-strength solid waste-based cement without alkali activator and its preparation method. Background Technology

[0002] Cement-based materials are currently the most widely used building materials in the world. With the development of environmental protection concepts, the high energy consumption and emissions associated with cement production are gradually attracting attention. Developing cement with a high content of solid waste (total solid waste ≥70%) is of great significance for achieving carbon reduction and emission reduction.

[0003] Mineral powder is an industrial solid waste from blast furnace ironmaking. Its main component is amorphous silica-alumina minerals, which have certain hydration activity and are widely used in modern cementitious materials. However, the application of mineral powder in solid waste-based cement still has the following limitations:

[0004] On the one hand, solid waste-based cement is limited by its low clinker content and low material system alkalinity, making it difficult to fully utilize the activity of mineral admixtures such as mineral powder in high-dosage systems. Therefore, solid waste-based cement often requires the addition of alkaline substances such as sodium hydroxide and sodium silicate as alkali activators. However, using alkali activators makes it difficult to control the cement alkalinity, easily leading to problems such as excessively short cement setting time, high slurry shear viscosity, poor paste flowability, large shrinkage, and easy cracking. For example, patent CN 114956614 A, published on August 30, 2022, discloses a slag cement based on sodium citrate-caustic alkali synergistic activation and its preparation method, with the slag cement paste flowability range of 140mm-160mm in the embodiment. Liquid alkali activators are expensive; they are generally added separately when using cement, which is not conducive to production and quality management; and liquid alkali activators are greatly affected by adsorbent substances in raw materials, easily resulting in fluctuations in performance.

[0005] On the other hand, the mineral powder content in existing cements is difficult to exceed 70%, and cement with a high mineral powder content cannot meet the performance requirements of ordinary Portland cement specifications. Patent CN111606584A, published on September 1, 2020, discloses a slag cement composed of the following components by weight percentage: clinker 30-60%, mineral powder 20-40%, gypsum 5-15%, auxiliary materials 5-12%, and activator 0.05-0.20%. Its mineral powder content is relatively low, only 20%-40%. Excessive slag content in cement leads to abnormally prolonged setting time and lower early strength; therefore, existing technologies typically add mineral powder exceeding 70%. The patent published on November 22, 2022, with publication number CN 115368033 A, discloses a non-calcined slag cement and its preparation method. Its final setting time is higher than 440 min, its initial setting time is higher than 300 min, and its 28-day compressive strength is lower than 45 MPa. This does not meet the requirements for cement setting time and strength in the ordinary Portland cement specification and is difficult to apply to actual engineering projects.

[0006] Furthermore, existing technologies often use processes such as air classification to prepare high specific surface area mineral powders, but the actual application of such ultrafine powders can lead to a significant increase in cement water demand and a significant decrease in the fluidity of cement paste. When using ordinary mixing or rotary mixing methods, ultrafine powders are prone to agglomeration and uneven dispersion, resulting in a decline in cement quality.

[0007] Therefore, it is essential to provide a type of cement that does not use alkali activators, has a large mineral powder content, and whose various properties meet the requirements of ordinary silicate cement. Summary of the Invention

[0008] The purpose of this invention is to provide a high-strength solid waste-based cement without alkali activators and its preparation method. Using broad-distribution ultrafine mineral powder and employing an aerated pressurized mixing method, the mineral powder incorporation amount is ≥75% without the use of additional alkali activators, significantly increasing the amount of mineral powder added while meeting the performance requirements of ordinary Portland cement. This invention solves the problems of ordinary solid waste-based cement, such as reliance on chemical activators to improve strength, low mineral powder incorporation, and setting time and strength incompatibility with construction environments. While effectively improving the utilization efficiency of mineral powder, this invention ensures that the performance of the high-strength solid waste-based cement without alkali activators meets current specifications for ordinary Portland cement.

[0009] The specific technical solution of this invention is as follows:

[0010] A high-strength solid waste-based cement without alkali activator comprises the following raw materials in parts by weight:

[0011] Silicate cement clinker: 18-24 parts;

[0012] Widely distributed ultrafine mineral powder: 75-80 parts;

[0013] Plaster: 1-1.5 parts;

[0014] The wide-distribution ultrafine mineral powder accounts for ≥75% of the mass of high-strength solid waste-based cement without alkali activator;

[0015] The characteristic particle size value De of the wide-distribution ultrafine mineral powder is less than 7.5 μm, and the uniformity coefficient n is less than 0.9;

[0016] The specific surface area of ​​the wide-distribution ultrafine mineral powder is ≥700m². 2 / kg, 3d activity index ≥87%, 28d activity index ≥120%;

[0017] The wide-distribution ultrafine mineral powder contains 14-16% active Al2O3; preferably, the main chemical components of the wide-distribution ultrafine mineral powder include: 30-35% SiO2, 14-16% Al2O3, 38-40% CaO and 7-10% MgO.

[0018] The preparation method of the wide-distribution ultrafine mineral powder is as follows: the slag is first ground by a vertical mill, and then ground by a ball mill, and prepared according to conventional methods to obtain wide-distribution ultrafine mineral powder that meets the above-mentioned index requirements; the particle size distribution of the wide-distribution ultrafine mineral powder is tested by a laser particle size analyzer to ensure that the particle size distribution of the mineral powder meets the requirements.

[0019] The silicate cement clinker is ordinary silicate cement clinker with a 28-day mortar compressive strength ≥ 55 MPa; the alkali content (Na2O + 0.658 K2O) in the silicate cement clinker is ≤ 0.6%.

[0020] The gypsum is industrial gypsum or phosphogypsum.

[0021] The present invention provides a method for preparing high-strength solid waste-based cement without alkali activator, specifically as follows:

[0022] The silicate cement clinker and gypsum are ground and mixed together according to the formula to obtain silicate cement clinker powder; then it is mixed with wide-distribution ultrafine mineral powder under air pressure.

[0023] The grinding mentioned above refers to grinding to a specific surface area ≥ 350 kg / m². 3 ;

[0024] Since both silicate cement clinker powder and wide-distribution ultrafine mineral powder raw materials are ultrafine powders, they are prone to agglomeration. Therefore, the mixing method is to use air-pressurized mixing with a pressure of 3-5 MPa and a mixing time of more than 1 hour to ensure that there is no obvious particle agglomeration in the high-strength solid waste-based cement without alkali activator after mixing.

[0025] The present invention provides a high-strength solid waste-based cement without alkali activator, with a consistency ≤30%, initial setting time 200-230 min, final setting time 270-290 min; 3-day flexural strength ≥4.2 MPa, 3-day compressive strength ≥21 MPa, 28-day flexural strength ≥9 MPa, 28-day compressive strength ≥55 MPa, and cement mortar fluidity 200-210 mm.

[0026] In the preparation method provided by this invention, the functions of each raw material are as follows:

[0027] Silicate cement clinker: Silicate cement clinker has high strength and fast reaction speed, providing the necessary alkaline environment for the hydration of mineral powder, promoting the dissolution of the glassy body of mineral powder and the hydration reaction, while providing early strength for high-volume low-carbon slag cement.

[0028] Wide-distribution ultrafine mineral powder: The wide-particle-size ultrafine mineral powder selected in this invention is prepared through a graded grinding process. It features high specific surface area, continuous and wide particle size distribution, characteristic particle size value De < 7.5 μm, and uniformity coefficient n < 0.9, effectively achieving the densest packing of powder particles. Cement strength and powder particle packing density are correlated. If the powder particles can reach maximum density packing before the hydration reaction, the hydration products can fill the voids and generate a denser structure, thereby improving the strength, density, and durability of cement mortar. After water is mixed with cement, it can be divided into filler water, interlayer water, and reaction water. Filler water is needed to fill the voids between powder particles, while interlayer water is used to wet and coat the particles and form a water film. Therefore, the less filler water used, the more water available for hydration reaction and forming a lubricating water film, resulting in a decrease in the water requirement for cement standard consistency and higher early strength. The ultrafine mineral powder has a high overall specific surface area, and the presence of a certain proportion of ultrafine powder can effectively achieve the functions of filling and reaction nuclei. This invention performs quantitative analysis of the particle size distribution curve, using the minimum chi-square algorithm in Python to accurately fit and calculate the particle size distribution curve of the mineral powder. The wide-particle-size ultrafine mineral powder used in this invention has a characteristic particle size value De < 7.5 μm and a uniformity coefficient < 0.9, which can achieve a good powder compaction effect, which is beneficial to reducing the filling water in the system and increasing the proportion of interlayer water. Therefore, the prepared alkali-free activator high-strength solid waste-based cement has a standard consistency water requirement of less than 30%, high strength, and good fluidity. In addition, the active alumina content in the chemical composition of the wide-particle-size ultrafine mineral powder is 14-16%, ensuring that the high-volume low-carbon slag cement has good hydration activity and can generate sufficient hydration products.

[0029] Gypsum: In cement with high admixture levels of solid waste, gypsum mainly functions to regulate setting time and provide SO4 required for the hydration reaction of slag. 2- C3A in cement and slowly dissolved active alumina in mineral powder can react with SO4 under alkaline conditions. 2-The reaction produces ettringite and related products, thereby enabling cement to set and providing early strength. However, excessive gypsum addition can lead to abnormal cement setting time, failing to meet construction requirements. Therefore, an appropriate amount of gypsum can promote the 3-day strength increase of cement with high solid waste content.

[0030] Compared with existing technologies, this invention mainly achieves its goal by precisely designing and optimizing the particle characteristics and packing effect of mineral powder, and selecting a reasonable dosage range for industrial gypsum. Without using chemical alkali activators, it ensures that all cement properties meet the requirements of 52.5 grade ordinary Portland cement, effectively reducing the production process difficulty, cost, and quality fluctuations of solid waste-based cement, and improving the product's scalability and applicability. This invention uses a staged grinding method of vertical mill followed by ball milling to obtain a wide-distribution ultrafine mineral powder. Compared with using an air classification system to prepare ultrafine powder, this method offers higher production efficiency and a simpler and easier-to-implement preparation process. The alkali-free activator-based high-strength solid waste-based cement prepared by this invention has a mineral powder content exceeding 75%, which can fully utilize bulk industrial solid waste such as mineral powder, reducing energy consumption and carbon emissions during cement production, and exhibiting low-carbon, energy-saving, and environmentally friendly characteristics. The alkali-free activator-based high-strength solid waste-based cement prepared by this invention meets the requirements of ordinary Portland cement in terms of setting time and other properties, has good workability, and meets the strength requirements of 52.5 grade general-purpose Portland cement. Attached Figure Description

[0031] Figure 1 The cumulative particle size distribution curve of the wide-distribution ultrafine mineral powder obtained by dry laser particle size analyzer;

[0032] Figure 2 The frequency distribution curve of the wide-distribution ultrafine mineral powder obtained by dry laser particle size analyzer is shown. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0035] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0036] This invention provides a high-strength solid waste-based cement without alkali activator, comprising the following raw materials in parts by weight:

[0037] Silicate cement clinker: 18-24 parts;

[0038] Widely distributed ultrafine mineral powder: 75-80 parts;

[0039] Plaster: 1-1.5 parts;

[0040] The wide-distribution ultrafine mineral powder accounts for ≥75% of the mass of high-strength solid waste-based cement without alkali activator;

[0041] The characteristic particle size value De of the wide-distribution ultrafine mineral powder is less than 7.5 μm, and the uniformity coefficient n is less than 0.9;

[0042] The specific surface area of ​​the wide-distribution ultrafine mineral powder is ≥700m². 2 / kg, 3d activity index ≥87%, 28d activity index ≥120%;

[0043] The wide-distribution ultrafine mineral powder used in this invention is based on the Rosin-Rammler-Bennet (RRB) model. An optimization function is constructed using the minimum chi-square method, and an iterative calculation method is employed to give the parameters in the fitted curve: the characteristic particle size (De) and the uniformity coefficient (n). The characteristic particle size (De) and the uniformity coefficient (n) are introduced as technical indicators of the wide-distribution ultrafine mineral powder, including the following:

[0044] 1) The particle size distribution of the mineral powder was tested using a laser particle size analyzer to obtain the cumulative particle size distribution curve of the ultrafine mineral powder.

[0045] 2) Based on the RRB model prototype: R = 100 × exp[-(D / De)] n In Python, the minimum chi-square method is used to construct an optimization function for the particle size distribution curve of ultrafine mineral powder. The minimum chi-square value of the fitting function is found through iterative calculations using the minimum algorithm, yielding the parameter values ​​of the fitting function. Here, n is the uniformity coefficient, which characterizes the breadth of the particle size distribution; a larger n value indicates a more uniform and narrower particle size distribution. De is the characteristic particle size, used to describe the fineness of the particles. This invention requires that the De value of the wide-distribution ultrafine mineral powder be less than 7.5 μm and the n value be less than 0.9.

[0046] 3) To ensure the accuracy of the fit, the correlation coefficient algorithm in Python was used to calculate the measured values ​​and the fitted function of the mineral powder particle size distribution curve, ensuring that the correlation coefficient R between the fitted model value and the measured value was consistent each time. 2 Greater than 0.99.

[0047] The preparation method of the wide-distribution ultrafine mineral powder is as follows: the slag is first ground by a vertical mill, and then ground by a ball mill to obtain the wide-distribution ultrafine mineral powder; the particle size distribution of the wide-distribution ultrafine mineral powder is tested by a laser particle size analyzer to ensure that the particle size distribution of the mineral powder meets the requirements.

[0048] The wide-distribution ultrafine mineral powder is prepared by grinding granulated blast furnace slag. This wide-distribution ultrafine mineral powder is obtained directly through graded grinding without air separation, retaining the wide particle distribution characteristics. The material particle size distribution frequency and cumulative distribution curve characteristics are as follows: Figure 1 As shown. The characteristic particle size and uniformity coefficient of the wide-distribution ultrafine mineral powder must meet the following requirements: De value less than 7.5 μm, n value less than 0.9.

[0049] The specific implementation method is as follows:

[0050] Example 1

[0051] A high-strength solid waste-based cement without alkali activator comprises the following raw materials in parts by weight:

[0052] Silicate cement clinker: 22.5 parts; 28-day mortar compressive strength: 57 MPa; alkali content (Na2O + 0.658 K2O) in silicate cement clinker: 0.5%.

[0053] Widely distributed ultrafine mineral powder: 76 parts, characteristic particle size De value is 6.31 μm, uniformity coefficient n value is 0.78; the specific surface area of ​​the widely distributed ultrafine mineral powder is 780 m². 2 / kg, with an active Al2O3 content of 15.27%, a 3-day activity index of 90%, and a 28-day activity index of 124%;

[0054] Gypsum: 1.5 parts, the gypsum is industrial gypsum.

[0055] The above-mentioned method for preparing high-strength solid waste-based cement without alkali activator is as follows: silicate cement clinker and gypsum are mixed according to the specified ratio and then ground together until the specific surface area is 370 kg / m². 3 The silicate cement clinker powder was obtained. Widely distributed ultrafine mineral powder and silicate cement clinker powder were weighed according to the formula, and the raw materials were mixed using an aerated pressurized mixing method, with the mixing pressure controlled at 3-5 MPa. After mixing for 2 hours, high-strength solid waste-based cement without alkali activator was obtained.

[0056] Comparative Example 1

[0057] A type of cement, identical to Example 1 in all other conditions except for the adjustment of the industrial gypsum content, comprises the following raw material components in parts by weight:

[0058] Silicate cement clinker: 24 parts; 28-day mortar compressive strength: 57 MPa; alkali content (Na2O + 0.658 K2O) in silicate cement clinker: 0.5%.

[0059] Widely distributed ultrafine mineral powder: 76 parts, characteristic particle size De value is 6.31 μm, uniformity coefficient n value is 0.78; the specific surface area of ​​the widely distributed ultrafine mineral powder is 780 m². 2 / kg, with an active Al2O3 content of 15.27%, a 3-day activity index of 90%, and a 28-day activity index of 124%;

[0060] Gypsum: 0 parts.

[0061] Comparative Example 2

[0062] A type of cement, identical to Example 1 in all other conditions except for the adjustment of the industrial gypsum content, comprises the following raw material components in parts by weight:

[0063] Silicate cement clinker: 21 parts; 28-day mortar compressive strength: 57 MPa; alkali content (Na2O + 0.658 K2O) in silicate cement clinker: 0.5%.

[0064] Widely distributed ultrafine mineral powder: 76 parts, characteristic particle size De value is 6.31 μm, uniformity coefficient n value is 0.78; the specific surface area of ​​the widely distributed ultrafine mineral powder is 780 m². 2 / kg, with an active Al2O3 content of 15.27%, a 3-day activity index of 90%, and a 28-day activity index of 124%;

[0065] Plaster: 3 parts The gypsum is industrial gypsum.

[0066] Example 2

[0067] A high-strength solid waste-based cement without alkali activator comprises the following raw materials in parts by weight:

[0068] Silicate cement clinker: 19.5 parts, 28-day mortar compressive strength 58 MPa; alkali content (Na2O + 0.658K2O) in silicate cement clinker is 0.48%.

[0069] Widely distributed ultrafine mineral powder: 79 parts, characteristic particle size De value is 6.72 μm, uniformity coefficient n value is 0.79; the specific surface area of ​​the widely distributed ultrafine mineral powder is 795 m². 2 / kg, with an active Al2O3 content of 15.35%, a 3-day activity index of 92%, and a 28-day activity index of 125%;

[0070] Gypsum: 1.5 parts, the gypsum is industrial gypsum.

[0071] The above-mentioned method for preparing high-strength solid waste-based cement without alkali activator is as follows: Silicate cement clinker and gypsum are ground and mixed according to the formula, and the mixture is ground until the specific surface area is 380 kg / m². 3 The silicate cement clinker powder is obtained; then it is mixed with wide-distribution ultrafine mineral powder under air pressure of 3-5 MPa for 2 hours.

[0072] Example 3

[0073] A high-strength solid waste-based cement without alkali activator comprises the following raw materials in parts by weight:

[0074] Silicate cement clinker: 19 parts, 28-day mortar compressive strength 58 MPa; alkali content (Na2O + 0.658K2O) in silicate cement clinker is 0.48%.

[0075] Widely distributed ultrafine mineral powder: 80 parts, characteristic particle size De value is 6.72 μm, uniformity coefficient n value is 0.79; the specific surface area of ​​the widely distributed ultrafine mineral powder is 795 m². 2 / kg, with an active Al2O3 content of 15.35%, a 3-day activity index of 92%, and a 28-day activity index of 125%;

[0076] Gypsum: 1.0 part, the gypsum is industrial gypsum.

[0077] The above-mentioned method for preparing high-strength solid waste-based cement without alkali activator is as follows: Silicate cement clinker and gypsum are ground and mixed according to the formula, and the mixture is ground until the specific surface area is 380 kg / m². 3 The silicate cement clinker powder is obtained; then it is mixed with wide-distribution ultrafine mineral powder under air pressure of 3-5 MPa for 2 hours.

[0078] Comparative Example 3

[0079] A cement, with all other conditions identical to Example 2 except for the alteration of the silicate cement clinker and the amount of broadly distributed ultrafine mineral powder, comprises the following raw material components in parts by weight:

[0080] Silicate cement clinker: 28.5 parts The 28-day compressive strength of the mortar is 58 MPa; the alkali content (Na2O + 0.658 K2O) in the silicate cement clinker is 0.48%.

[0081] Widely distributed ultrafine mineral powder: 70 parts The characteristic particle size De value is 6.72 μm, and the uniformity coefficient n value is 0.79; the specific surface area of ​​the wide-distribution ultrafine mineral powder is 795 m². 2 / kg, with an active Al2O3 content of 15.35%, a 3-day activity index of 92%, and a 28-day activity index of 125%;

[0082] Gypsum: 1.5 parts, the gypsum is industrial gypsum.

[0083] Comparative Example 4

[0084] A cement, with all other conditions identical to Example 2 except for the alteration of the silicate cement clinker and the amount of wide-particle-size ultrafine mineral powder, comprises the following raw material components in parts by weight:

[0085] Silicate cement clinker: 13.5 parts The 28-day compressive strength of the mortar is 58 MPa; the alkali content (Na2O + 0.658 K2O) in the silicate cement clinker is 0.48%.

[0086] Widely distributed ultrafine mineral powder: 85 parts The characteristic particle size De is 6.72 μm, and the uniformity coefficient n is 0.79; the specific surface area of ​​the wide-distribution ultrafine mineral powder is 795 m². 2 / kg, with an active Al2O3 content of 15.35%, a 3-day activity index of 92%, and a 28-day activity index of 125%;

[0087] Gypsum: 1.5 parts, the gypsum is industrial gypsum.

[0088] Comparative Example 5 (Narrowly Distributed Mineral Powder)

[0089] A type of cement, with all other conditions identical to Example 2 except for the type of mineral powder, was selected, using narrow-distribution ultrafine mineral powder with similar specific surface area but different characteristic particle size and uniformity coefficient, comprising the following raw material components in parts by weight:

[0090] Silicate cement clinker: 19.5 parts, 28-day mortar compressive strength 58 MPa; alkali content (Na2O + 0.658K2O) in silicate cement clinker is 0.48%.

[0091] Ordinary ultrafine mineral powder: 79 parts The characteristic particle size De is 10.61 μm, and the uniformity coefficient n is 1.17. The specific surface area of ​​the wide-distribution ultrafine mineral powder is 785 m². 2 / kg, with an active Al2O3 content of 15.37%, a 3-day activity index of 91%, and a 28-day activity index of 125%;

[0092] Gypsum: 1.5 parts, the gypsum is industrial gypsum.

[0093] Comparative Example 6 (Narrowly Distributed Mineral Powder)

[0094] A type of cement, with all other conditions identical to Example 2 except for the type of mineral powder, was selected, using narrow-distribution ultrafine mineral powder with similar specific surface area but different characteristic particle size and uniformity coefficient, comprising the following raw material components in parts by weight:

[0095] Silicate cement clinker: 19.5 parts, 28-day mortar compressive strength 58 MPa; alkali content (Na2O + 0.658K2O) in silicate cement clinker is 0.48%.

[0096] Ordinary ultrafine mineral powder: 79 parts The characteristic particle size De is 10.52 μm, and the uniformity coefficient n is 1.14. The specific surface area of ​​the wide-distribution ultrafine mineral powder is 790 m². 2 / kg, with an active Al2O3 content of 15.33%, a 3-day activity index of 90%, and a 28-day activity index of 124%;

[0097] Gypsum: 1.5 parts, the gypsum is industrial gypsum.

[0098] Comparative Example 7 (S95 mineral powder, with low active Al content)

[0099] A cement, with all other conditions identical to Example 2, except for the type of mineral powder, was made using commercially available S95 mineral powder. Specific surface area is 420m² 2 / kg, with an activated alumina content of 13.5%, a characteristic particle size De of 16.02μm, and uniformity. The sex coefficient n is 1.03. The raw material components include the following parts by weight:

[0100] Silicate cement clinker: 19.5 parts, 28-day mortar compressive strength 58 MPa; alkali content (Na2O + 0.658K2O) in silicate cement clinker is 0.48%.

[0101] S95 mineral powder: 79 copies,

[0102] Gypsum: 1.5 parts. The gypsum is industrial gypsum.

[0103] Comparative Example 8

[0104] A cement comprising the following raw materials in parts by weight, wherein all other conditions are the same as in Example 2, except that silicate cement clinker of different strengths is used:

[0105] Silicate cement clinker: 19.5 parts 28-day mortar compressive strength: 47 MPa; The alkali content (Na2O + 0.658K2O) in silicate cement clinker is 0.51%.

[0106] Widely distributed ultrafine mineral powder: 79 parts, characteristic particle size De value is 6.72 μm, uniformity coefficient n value is 0.79; the specific surface area of ​​the widely distributed ultrafine mineral powder is 795 m². 2 / kg, 3d activity index 92%, 28d activity index 125%;

[0107] Gypsum: 1.5 parts, the gypsum is industrial gypsum.

[0108] The performance of the cements in each embodiment and comparative example was tested, and the test reference specifications are shown below. Table 1 shows the relevant performance parameters of the cements in the embodiments and comparative examples of this invention.

[0109] The compressive strength of the mortar should be referenced to GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)";

[0110] Cement consistency and setting time should refer to GB / T1346-2011 "Standard Consistency Water Requirement, Setting Time and Soundness Test Methods for Cement";

[0111] The fluidity of cement mortar should be determined according to GB / T2419-2005 "Method for Determination of Flowability of Cement Mortar".

[0112] Table 1 Performance parameters of slag cement in the examples and comparative examples (kg / m³) 3 )

[0113]

[0114]

[0115] As can be seen from the results of Example 1 and Comparative Examples 1 and 2 in the table, the setting time of the alkali-free activator high-strength solid waste-based cement in this invention meets the requirements of initial setting time ≥ 45 min and final setting time ≤ 390 min for silicate cement; the flexural and compressive strength at 3d and 28d are significantly higher than those of Comparative Examples 1 and 2.

[0116] Comparison of the results of Example 2 and Comparative Examples 3 and 4 shows that the alkali-free activator-based high-strength solid waste cement of the present invention can still achieve a 28-day compressive strength of ≥55MPa when the mineral powder content is 75%-80%; however, when the mineral powder content exceeds 80%, the 28-day compressive strength of the cement begins to decrease significantly, and the setting time exceeds 400min.

[0117] Compared with the comparative example, the product of the present invention has good fluidity, and the flowability of cement mortar meets 200±20mm.

[0118] Comparing Example 2 with Comparative Examples 5 and 6, it can be seen that when using narrowly distributed ultrafine mineral powder with a particle size De > 7.5 μm and a uniformity coefficient n > 0.9, the standard consistency of cement is too high, the water demand increases significantly, the fluidity of cement paste decreases significantly, and the 3d strength is low.

[0119] A comparison of Example 2 and Comparative Example 7 shows that when using commercially available S95 mineral powder, the slag cement setting time exceeds 390 minutes due to the low specific surface area and activity index of the mineral powder, and the 3-day compressive strength is only 11.6 MPa.

[0120] As can be seen from the test results of Example 2 and Comparative Example 8, when the strength of silicate cement clinker is low, the final setting time of cement is 470 min, the 3-day compressive strength is 12.3 MPa, and the 28-day compressive strength is 41.5 MPa, which are significantly lower than the product prepared in this invention.

[0121] The alkali-activated high-strength solid waste-based cement provided by this invention has a mineral powder content exceeding 75%, and its setting time and cement mortar fluidity meet the requirements of ordinary Portland cement; its standard consistency is below 30.0%; its 3-day compressive strength is higher than 21 MPa and its 28-day compressive strength is higher than 55 MPa, meeting the strength requirements of general-purpose Portland cement with a strength grade of 52.5. Compared to ordinary solid waste-based cement, the alkali-free activator-based high-strength solid waste-based cement prepared by this invention does not contain chemical alkali activators, has a high mineral powder content, good workability, and exhibits high flexural and compressive strength at both 3-day and 28-day, demonstrating good mechanical properties. The alkali-free activator-based high-strength solid waste-based cement proposed in this invention has significant value for the resource utilization of solid waste and low-carbon environmental protection.

[0122] The data underlined above do not meet the requirements of this invention.

[0123] The above description of the embodiments is intended to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A high-strength solid waste-based cement without alkali activator, characterized in that, The alkali-free activator-based high-strength solid waste cement is composed of the following raw materials in parts by weight: Silicate cement clinker: 18-24 parts; Widely distributed ultrafine mineral powder: 75-80 parts; Plaster: 1-1.5 parts; The characteristic particle size De value of the wide-distribution ultrafine mineral powder is less than 7.5 μm, and the uniformity coefficient n value is less than 0.9; The specific surface area of ​​the wide-distribution ultrafine mineral powder is ≥700m². 2 / kg, 3d activity index ≥87%, 28d activity index ≥120%; The alkali-free activator-based high-strength solid waste cement has a consistency ≤30%, an initial setting time of 200-230 min, a final setting time of 270-290 min, a 3-day flexural strength ≥4.2 MPa, a 3-day compressive strength ≥21 MPa, a 28-day flexural strength ≥9 MPa, a 28-day compressive strength ≥55 MPa, and a cement mortar fluidity of 200-210 mm.

2. The alkali-free activator-based high-strength solid waste cement according to claim 1, characterized in that, The wide-distribution ultrafine mineral powder contains 14–16% Al2O3.

3. The alkali-free activator-based high-strength solid waste cement according to claim 1, characterized in that, The 28-day compressive strength of the silicate cement clinker is ≥55MPa; the alkali content (Na2O+0.658K2O) in the silicate cement clinker is ≤0.6%.

4. The alkali-free activator-based high-strength solid waste cement according to claim 1, characterized in that, The gypsum mentioned is industrial gypsum.

5. A method for preparing alkali-free activator-based high-strength solid waste cement according to any one of claims 1-4, characterized in that, The preparation method is as follows: silicate cement clinker and gypsum are ground and mixed together according to the formula to obtain silicate cement clinker powder; then it is mixed with wide-distribution ultrafine mineral powder under air pressure.

6. The preparation method according to claim 5, characterized in that, The grinding mentioned above refers to grinding to a specific surface area ≥ 350 kg / m². 3 .

7. The preparation method according to claim 5 or 6, characterized in that, The inflation and pressurization mixing process involves a pressure of 3-5 MPa and a mixing time of more than 1 hour.

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