Kaolin tailing-based low-carbon high-toughness cementing material and preparation method thereof

Abstract

The invention discloses a low-carbon high-toughness cementing material based on kaolin tailings and a preparation method of the low-carbon high-toughness cementing material, and the low-carbon high-toughness cementing material is prepared from the following components in parts by weight: 4.0 to 5.5 parts of Portland cement, 3.0 to 4.0 parts of kaolin tailings, 1.5 to 2.0 parts of calcium carbonate, 0.005 to 0.05 part of microfiber, 0.5 to 1 part of gypsum and 0 to 3.3 parts of fine aggregate. The preparation method comprises the following steps: carrying out light burning treatment on the kaolin tailings, and then cooling to room temperature; grinding the obtained product to form powder with the specific surface area of 400-700m < 2 > / kg; and uniformly stirring and mixing Portland cement, calcium carbonate, gypsum, fine aggregate, microfibers and the obtained powder to obtain the low-carbon high-toughness cementing material based on the kaolin tailings. The low-temperature calcined kaolin tailings are adopted to replace high-quality kaolin to serve as an aluminosilicate mineral source, and the utilization rate of tailings resources is remarkably increased.

Description

Technical Field

[0001] This invention pertains to cementitious materials and their preparation methods, specifically a low-carbon, high-toughness cementitious material based on kaolin tailings and its preparation method. Background Technology

[0002] With global population growth, the demand for cement is expected to continue to increase. However, cement materials have inherent drawbacks such as high carbon emissions and low toughness, which limit their application range and put pressure on the ecological environment.

[0003] To promote energy conservation and emission reduction, the construction industry both domestically and internationally is actively exploring alternative solutions. Currently, most commonly used mineral admixtures in cement are derived from industrial byproducts, such as fly ash and silica fume, and their content in cement generally does not exceed 30%. With industrial technological upgrades, the supply of these byproducts is expected to gradually decrease, making it difficult to meet the continued growth in infrastructure demand. Calcined clay, as a non-industrial source mineral admixture, has the advantage of abundant resources. However, high-quality clays such as kaolin have limited production and are primarily used in the ceramics industry, resulting in high costs and restricting their large-scale application in cement-based materials. Furthermore, the utilization rate of the large amount of tailings generated during clay mining is currently low. However, tailings have a similar chemical composition to clay and offer significant advantages in terms of low carbon emissions, environmental friendliness, and excellent performance: their calcination temperature and energy consumption are much lower than traditional silicate clinker, and their pozzolanic activity can effectively improve the strength and durability of cement-based materials, especially tensile strength. However, using tailings as a mineral admixture to prepare cementitious materials still presents the problem of brittleness.

[0004] Currently, cement-based composite systems with microfibers generally suffer from poor compatibility, mainly manifested in the high compressive strength of the matrix leading to excessively strong interfacial bonding and the difficulty in uniformly dispersing the fibers. Summary of the Invention

[0005] Purpose of the invention: In order to overcome the shortcomings of the existing technology, the purpose of this invention is to provide a low-carbon, high-toughness cementitious material based on kaolin tailings with high flexural strength and good tensile toughness. Another purpose of this invention is to provide a low-carbon, high-toughness cementitious material based on kaolin tailings with high tailings resource utilization rate.

[0006] Technical solution: The present invention discloses a low-carbon, high-toughness cementitious material based on kaolin tailings, which is composed of the following components in parts by weight: 4.0-5.5 parts silicate cement, 3.0-4.0 parts kaolin tailings, 1.5-2.0 parts calcium carbonate, 0.005-0.05 parts microfiber, 0.5-1 parts gypsum, and 0-3.3 parts fine aggregate.

[0007] Furthermore, the silicate cement is either P·I silicate cement or P·II silicate cement.

[0008] Furthermore, the specific surface area of ​​kaolin tailings is 300~500m². 2 / kg.

[0009] Furthermore, calcium carbonate is derived from one or more of limestone, calcite, light calcium carbonate, or nano-calcium carbonate. The specific surface area of ​​calcium carbonate is 500–900. 2 / kg.

[0010] Furthermore, the microfibers are polyvinyl alcohol fibers with a length of 8-18 mm, a diameter of 0.01-0.04 mm, a strain rate of ≥5.0%, and a tensile strength of ≥1000 MPa.

[0011] Furthermore, gypsum is derived from anhydrite or dihydrate gypsum.

[0012] Furthermore, the fine aggregate is manufactured sand, standard sand, or quartz sand with a particle size of less than 5 mm.

[0013] The preparation method of the low-carbon, high-toughness cementitious material based on kaolin tailings according to the present invention includes the following steps:

[0014] Step 1: Lightly burn the kaolin tailings and then cool them to room temperature.

[0015] Step two: Grind the material obtained in step one to form a specific surface area of ​​400~700 m². 2 / kg of powder;

[0016] Step 3: Silicate cement, calcium carbonate, gypsum, fine aggregate, microfiber and the powder obtained in step 2 are stirred and mixed evenly to obtain a low-carbon and high-toughness cementitious material based on kaolin tailings.

[0017] Furthermore, in step one, the temperature for the light calcination treatment is 500~800℃, and the time is 120~240 minutes.

[0018] Furthermore, in step three, the stirring speed is 140~285 rpm, and the time is 4~10 minutes.

[0019] Preparation principle: Calcinated and ground kaolin tailings are combined with calcium carbonate as a mineral admixture to replace cement. Different particle sizes of the mineral admixture are used to optimize the multi-component gradation with cement. Simultaneously, the gypsum content is varied to control the hydration rate and later-stage strength, inducing pozzolanic reaction to generate CASH, trisulfide-type hydrated calcium sulfoaluminate, aluminocarbonate, and other hydration products, thus strengthening the matrix. The formation of these products also enhances the interaction between fibers and cementitious materials, resulting in improved ductility and toughness on a macroscopic scale. Furthermore, the addition of calcined kaolin tailings and calcium carbonate promotes fiber dispersion, contributing to improved ductility and mechanical properties of the specimens.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0021] 1. The microfibers in the obtained low-carbon high-toughness cementitious material are uniformly dispersed, which can not only moderately reduce the strength of the matrix to alleviate the stress concentration at the interface, but also improve the uniformity of fiber dispersion by increasing the viscosity of the slurry. The resulting material has high flexural strength and good tensile toughness.

[0022] 2. The low-temperature calcination process is used to prepare calcined kaolin tailings to replace high-quality kaolin as a source of aluminosilicate minerals, which can effectively alleviate the resource pressure of kaolin and significantly improve the utilization rate of tailings resources.

[0023] 3. By incorporating a large amount of limestone powder and combining it with multi-component synergistic optimization design, the amount of silicate cement used has been significantly reduced, achieving a reduction in carbon emissions throughout the entire life cycle and improving the green performance of cementitious materials.

[0024] 4. By optimizing the particle size distribution of calcined kaolin tailings and limestone powder, the pozzolanic reaction in the system is promoted, generating hydration products, including CASH and aluminocarbonates, which are rarely seen in traditional silicate cements. This improves the toughness of the material at the matrix level. The introduction of microfibers further enhances the toughness of cement-based materials at the macro scale, significantly improving their ductility and crack resistance, and achieving synergistic optimization of the material in terms of high strength and toughness and low carbon emissions. Attached Figure Description

[0025] Figure 1 The curves of tensile stress versus tensile strain of the specimens prepared in Examples 1-7 at 28 days of age;

[0026] Figure 2 The tensile stress versus tensile strain curves of the specimens prepared in Comparative Examples 1-5 at 28 days of age;

[0027] Figure 3 The curves showing the flexural stress versus flexural displacement of the specimens prepared in Examples 1-7 at 28 days of age;

[0028] Figure 4 The curves show the flexural stress versus flexural displacement of the specimens prepared in Comparative Examples 1-5 at 28 days of age. Detailed Implementation

[0029] Unless otherwise specified, all materials and reagents used in the following embodiments are commercially available. Experimental methods not specifically described in the embodiments are generally performed under standard conditions or as recommended by the manufacturer.

[0030] Example 1

[0031] A method for preparing a low-carbon, high-toughness cementitious material based on kaolin tailings includes the following steps:

[0032] (1) Take 3.0 parts of a specific surface area of ​​300m² 2 / kg of kaolin tailings powder was placed in a muffle furnace for light calcination at a temperature of 800℃ and a time of 120 minutes.

[0033] (2) After the tailings have cooled to room temperature, they are ground to form a specific surface area of ​​500 m². 2 / kg of powder.

[0034] (3) The ground calcined tailings powder is mixed with 5.5 parts of silicate cement (P·Ⅱ) and 1.5 parts of limestone powder (800m). 2 / kg), 0.5 parts dihydrate gypsum (300m 2 The mixture consists of 3.3 parts of fine aggregate (quartz sand with a particle size of less than 5 mm) and 0.04 parts of microfiber with a tensile strength of 1600 MPa, a strain rate of 7%, a diameter of 0.039 mm, and a length of 12 mm. The mixture is then vacuum-stored at room temperature until ready for use. The microfiber is polyvinyl alcohol fiber.

[0035] (4) Add the mixture obtained in step (3) to 4.5 parts of water and 0.05 parts of polycarboxylate superplasticizer. Stir at 140 and 285 rpm for 2 minutes respectively to form a uniform slurry. Pour the prepared slurry into a specified mold and cover the surface with a film. After 1 day, demold the specimen and place it in an environment of 20±2℃ and relative humidity greater than 95% for curing. Test the tensile and flexural properties of the specimen at an age of 28 days. The tensile and flexural strengths are shown in Table 1. The tensile stress-strain curve and the curve of flexural stress versus flexural displacement are shown in Table 1. Figure 1 and Figure 3 middle.

[0036] Example 2

[0037] A method for preparing a low-carbon, high-toughness cementitious material based on kaolin tailings includes the following steps:

[0038] (1) Take 3.0 parts of a specific surface area of ​​300m² 2 / kg of kaolin tailings powder was placed in a muffle furnace for light calcination at a temperature of 800℃ and a time of 120 minutes.

[0039] (2) After the tailings have cooled to room temperature, they are ground to form a specific surface area of ​​500 m². 2 / kg of powder.

[0040] (3) The ground calcined tailings powder is mixed with 5.0 parts of silicate cement (P·Ⅱ) and 1.5 parts of limestone powder (800m).2 / kg), 0.5 parts dihydrate gypsum (300m 2 The mixture consists of 3.3 parts of fine aggregate (quartz sand with a particle size of less than 5 mm) and 0.05 parts of microfiber with a tensile strength of 1600 MPa, a strain rate of 7%, a diameter of 0.039 mm, and a length of 12 mm. The mixture is then vacuum-stored at room temperature until ready for use. The microfiber is polyvinyl alcohol fiber.

[0041] (4) Add the mixture obtained in step (3) to 3.5 parts of water and 0.05 parts of polycarboxylate superplasticizer, and stir at 140 and 285 rpm for 2 minutes respectively to form a uniform slurry.

[0042] The prepared slurry was poured into a specified mold and then covered with a film. One day later, the specimens were demolded and cured at 20±2℃ and a relative humidity greater than 95%. The tensile and flexural properties of the specimens were tested after 28 days. The tensile and flexural strengths are shown in Table 1. The tensile stress-strain curves and the flexural stress-flexural displacement curves are shown in Table 1. Figure 1 and Figure 3 middle.

[0043] Example 3

[0044] A method for preparing a low-carbon, high-toughness cementitious material based on kaolin tailings includes the following steps:

[0045] (1) Take 3.0 parts of a specific surface area of ​​300m² 2 / kg of kaolin tailings powder was placed in a muffle furnace for light calcination at a temperature of 800℃ and a time of 120 minutes.

[0046] (2) After the tailings have cooled to room temperature, they are ground to form a specific surface area of ​​500 m². 2 / kg of powder.

[0047] (3) The ground calcined tailings powder is mixed with 5.0 parts of silicate cement (P·Ⅱ) and 1.5 parts of limestone powder (800m). 2 / kg), 0.5 parts dihydrate gypsum (300m 2 The mixture consists of 3.3 parts of fine aggregate (standard sand with a particle size of less than 5 mm) and 0.04 parts of microfiber with a tensile strength of 1600 MPa, a strain rate of 7%, a diameter of 0.039 mm, and a length of 12 mm. The mixture is then vacuum-stored at room temperature until ready for use. The microfiber is polyvinyl alcohol fiber.

[0048] (4) Add the mixture obtained in step (3) to 4.5 parts of water, add 0.05 parts of polycarboxylate superplasticizer, and stir at 140 and 285 rpm for 2 minutes respectively to form a uniform slurry.

[0049] The prepared slurry was poured into a specified mold and then covered with a film. One day later, the specimens were demolded and cured at 20±2℃ and a relative humidity greater than 95%. The tensile and flexural properties of the specimens were tested after 28 days. The tensile and flexural strengths are shown in Table 1. The tensile stress-strain curves and the flexural stress-flexural displacement curves are shown in Table 1. Figure 1 and Figure 3 middle.

[0050] Example 4

[0051] A method for preparing a low-carbon, high-toughness cementitious material based on kaolin tailings includes the following steps:

[0052] (1) Take 3.0 parts of a specific surface area of ​​300m² 2 / kg of kaolin tailings powder was placed in a muffle furnace for light calcination at a temperature of 800℃ and a time of 120 minutes.

[0053] (2) After the tailings have cooled to room temperature, they are ground to form a specific surface area of ​​500 m². 2 / kg of powder.

[0054] (3) The ground calcined tailings powder is mixed with 5.0 parts of silicate cement (P·Ⅱ) and 1.5 parts of limestone powder (800m). 2 / kg), 0.5 parts dihydrate gypsum (300m 2 The mixture consists of 3.3 parts of fine aggregate (standard sand with a particle size of less than 5 mm) and 0.05 parts of microfiber with a tensile strength of 1600 MPa, a strain rate of 7%, a diameter of 0.039 mm, and a length of 12 mm. The mixture is then vacuum-stored at room temperature until ready for use. The microfiber is polyvinyl alcohol fiber.

[0055] (4) Add the mixture obtained in step (3) to 3.5 parts of water and 0.05 parts of polycarboxylate superplasticizer, and stir at 140 and 285 rpm for 2 minutes respectively to form a uniform slurry.

[0056] The prepared slurry was poured into a specified mold and then covered with a film. One day later, the specimens were demolded and cured at 20±2℃ and a relative humidity greater than 95%. The tensile and flexural properties of the specimens were tested after 28 days. The tensile and flexural strengths are shown in Table 1. The tensile stress-strain curves and the flexural stress-flexural displacement curves are shown in Table 1. Figure 1 and Figure 3 middle.

[0057] Example 5

[0058] A method for preparing a low-carbon, high-toughness cementitious material based on kaolin tailings includes the following steps:

[0059] (1) Take 3.0 parts of a specific surface area of ​​300m² 2 / kg of kaolin tailings powder was placed in a muffle furnace for light calcination at a temperature of 800℃ and a time of 120 minutes.

[0060] (2) After the tailings have cooled to room temperature, they are ground to form a specific surface area of ​​500 m². 2 / kg of powder.

[0061] (3) The ground calcined tailings powder is mixed with 5.0 parts of silicate cement (P·Ⅱ) and 1.5 parts of limestone powder (800m). 2 / kg), 0.5 parts dihydrate gypsum (300m 2 The mixture is prepared by mixing 0.03 parts of microfibers with a tensile strength of 1600 MPa, a strain rate of 7%, a diameter of 0.039 mm, and a length of 12 mm with a per kg weight of polyvinyl alcohol (VAE) and then storing it under vacuum at room temperature until ready for use.

[0062] (4) Add the mixture obtained in step (3) to 4.5 parts of water and 0.05 parts of polycarboxylate superplasticizer, and stir at 140 and 285 rpm for 2 minutes respectively to form a uniform slurry.

[0063] The prepared slurry was poured into a specified mold and then covered with a film. One day later, the specimens were demolded and cured at 20±2℃ and a relative humidity greater than 95%. The tensile and flexural properties of the specimens were tested after 28 days. The tensile and flexural strengths are shown in Table 1. The tensile stress-strain curves and the flexural stress-flexural displacement curves are shown in Table 1. Figure 1 and Figure 3 middle.

[0064] Example 6

[0065] A method for preparing a low-carbon, high-toughness cementitious material based on kaolin tailings includes the following steps:

[0066] (1) Take 3.0 parts of a specific surface area of ​​300m² 2 / kg of kaolin tailings powder was placed in a muffle furnace for light calcination at a temperature of 800℃ and a time of 120 minutes.

[0067] (2) After the tailings have cooled to room temperature, they are ground to form a specific surface area of ​​500 m². 2 / kg of powder.

[0068] (3) The ground calcined tailings powder is mixed with 5.0 parts of silicate cement (P·Ⅱ) and 1.5 parts of limestone powder (800m). 2 / kg), 0.5 parts dihydrate gypsum (300m2 0.04 parts of microfibers with a tensile strength of 1600 MPa, a strain rate of 7%, a diameter of 0.039 mm, and a length of 12 mm were mixed evenly to form a mixture and then stored under vacuum at room temperature for later use. The microfibers were polyvinyl alcohol fibers.

[0069] (4) Add the mixture obtained in step (3) to 3.5 parts of water and 0.05 parts of polycarboxylate superplasticizer, and stir at 140 and 285 rpm for 2 minutes respectively to form a uniform slurry.

[0070] The prepared slurry was poured into a specified mold and then covered with a film. One day later, the specimens were demolded and cured at 20±2℃ and a relative humidity greater than 95%. The tensile and flexural properties of the specimens were tested after 28 days. The tensile and flexural strengths are shown in Table 1. The tensile stress-strain curves and the flexural stress-flexural displacement curves are shown in Table 1. Figure 1 and Figure 3 middle.

[0071] Example 7

[0072] A method for preparing a low-carbon, high-toughness cementitious material based on kaolin tailings includes the following steps:

[0073] (1) Take 3.0 parts of a specific surface area of ​​300m² 2 / kg of kaolin tailings powder was placed in a muffle furnace for light calcination at a temperature of 600℃ and a time of 240 minutes.

[0074] (2) After the tailings have cooled to room temperature, they are ground to form a specific surface area of ​​500 m². 2 / kg of powder.

[0075] (3) The ground calcined tailings powder is mixed with 5.0 parts of silicate cement (P·Ⅱ) and 1.5 parts of limestone powder (800m). 2 / kg), 0.5 parts dihydrate gypsum (300m 2 0.005 parts of microfibers with a tensile strength of 1600 MPa, a strain rate of 7%, a diameter of 0.039 mm, and a length of 12 mm were mixed evenly to form a mixture and then stored under vacuum at room temperature for later use. The microfibers were polyvinyl alcohol fibers.

[0076] (4) Add the mixture obtained in step (3) to 4.5 parts of water and 0.05 parts of polycarboxylate superplasticizer, and stir at 140 and 285 rpm for 2 minutes respectively to form a uniform slurry.

[0077] The prepared slurry was poured into a specified mold and then covered with a film. One day later, the specimens were demolded and cured at 20±2℃ and a relative humidity greater than 95%. The tensile and flexural properties of the specimens were tested after 28 days. The tensile and flexural strengths are shown in Table 1. The tensile stress-strain curves and the flexural stress-flexural displacement curves are shown in Table 1. Figure 1 and Figure 3 middle.

[0078] Example 8

[0079] A method for preparing a low-carbon, high-toughness cementitious material based on kaolin tailings includes the following steps:

[0080] (1) Take 4.0 parts of a specific surface area of ​​400m² 2 / kg of kaolin tailings powder was placed in a muffle furnace for light calcination treatment at a temperature of 500℃ and a time of 200 minutes.

[0081] (2) After the tailings have cooled to room temperature, they are ground to form a specific surface area of ​​400 m². 2 / kg of powder.

[0082] (3) The ground calcined tailings powder is mixed with 4.0 parts of silicate cement (P·I) and 2.0 parts of calcite powder (800m). 2 / kg), 0.5~1 part anhydrite (300m 2 The mixture consists of 1.0 part fine aggregate (manufactured sand with a particle size less than 5 mm) and 0.01 part microfibers with a tensile strength of 1600 MPa, a strain rate of 7%, a diameter of 0.039 mm, and a length of 8 mm. The mixture is then vacuum-stored at room temperature until ready for use. The microfibers are polyvinyl alcohol fibers.

[0083] (4) Add the mixture obtained in step (3) to 4.0 parts of water and 0.05 parts of polycarboxylate superplasticizer, and stir at 140 and 285 rpm for 5 minutes respectively to form a uniform slurry.

[0084] The prepared slurry was poured into a specified mold and then covered with a film. One day later, the specimens were demolded and cured at 20±2℃ and a relative humidity greater than 95%. The tensile and flexural properties of the specimens were tested after 28 days. The tensile and flexural strengths are shown in Table 1. The tensile stress-strain curves and the flexural stress-flexural displacement curves are shown in Table 1. Figure 1 and Figure 3 middle.

[0085] Example 9

[0086] A method for preparing a low-carbon, high-toughness cementitious material based on kaolin tailings includes the following steps:

[0087] (1) Take 3.5 portions with a specific surface area of ​​500m² 2 / kg of kaolin tailings powder was placed in a muffle furnace for light calcination at a temperature of 700℃ and a time of 150 minutes.

[0088] (2) After the tailings have cooled to room temperature, they are ground to form a specific surface area of ​​700 m². 2 / kg of powder.

[0089] (3) The ground calcined tailings powder is mixed with 4.5 parts of silicate cement (P·I) and 1.8 parts of light calcium carbonate powder (800m). 2 / kg), 0.8 parts anhydrite (300m) 2 The mixture consists of 2 parts of fine aggregate (manufactured sand with a particle size of less than 5 mm) and 0.03 parts of microfiber with a tensile strength of 1600 MPa, a strain rate of 7%, a diameter of 0.039 mm, and a length of 18 mm. The mixture is then vacuum-stored at room temperature until ready for use. The microfiber is polyvinyl alcohol fiber.

[0090] (4) Add the mixture obtained in step (3) to 4.0 parts of water and 0.05 parts of polycarboxylate superplasticizer, and stir at 140 and 285 rpm for 4 minutes respectively to form a uniform slurry.

[0091] The prepared slurry was poured into a specified mold and then covered with a film. One day later, the specimens were demolded and cured at 20±2℃ and a relative humidity greater than 95%. The tensile and flexural properties of the specimens were tested after 28 days. The tensile and flexural strengths are shown in Table 1. The tensile stress-strain curves and the flexural stress-flexural displacement curves are shown in Table 1. Figure 1 and Figure 3 middle.

[0092] Comparative Example 1

[0093] A method for preparing a cementitious material includes the following steps:

[0094] (1) Take 3.0 parts of a specific surface area of ​​300m² 2 / kg of kaolin tailings powder was placed in a muffle furnace for light calcination at a temperature of 800℃ and a time of 120 minutes.

[0095] (2) After the tailings have cooled to room temperature, they are ground to form a specific surface area of ​​500 m². 2 / kg of powder.

[0096] (3) The ground calcined tailings powder is mixed with 5.0 parts of silicate cement (P·Ⅱ) and 1.5 parts of limestone powder (800m). 2 / kg), 0.5 parts dihydrate gypsum (300m 2After mixing 3.3 parts of fine aggregate (quartz sand) with 3.3 parts of fine aggregate ( / kg) to form a mixture, the mixture is placed in a vacuum storage environment at room temperature for later use.

[0097] (4) Add the mixture described in step (3) to 4.5 parts of water and 0.05 parts of polycarboxylate superplasticizer, and stir at 140 and 285 rpm for 2 minutes respectively to form a uniform slurry.

[0098] The prepared slurry was poured into a specified mold and then covered with a film. One day later, the specimens were demolded and cured at 20±2℃ and a relative humidity greater than 95%. The tensile and flexural properties of the specimens were tested after 28 days. The tensile and flexural strengths are shown in Table 1. The tensile stress-strain curves and the flexural stress-flexural displacement curves are shown in Table 1. Figure 2 and Figure 4 middle.

[0099] Comparative Example 2

[0100] A method for preparing a cementitious material includes the following steps:

[0101] (1) Take 3.0 parts of a specific surface area of ​​300m² 2 / kg of kaolin tailings powder was placed in a muffle furnace for light calcination at a temperature of 800℃ and a time of 120 minutes.

[0102] (2) After the tailings have cooled to room temperature, they are ground to form a specific surface area of ​​500 m². 2 / kg of powder.

[0103] (3) The ground calcined tailings powder is mixed with 5.0 parts of silicate cement (P·Ⅱ) and 1.5 parts of limestone powder (800m). 2 / kg), 0.5 parts dihydrate gypsum (300m 2 After mixing the mixture thoroughly to form a homogeneous mixture, store it under vacuum at room temperature until ready for use.

[0104] (4) Add the mixture described in step (3) to 4.5 parts of water and 0.05 parts of polycarboxylate superplasticizer, and stir at 140 and 285 rpm for 2 minutes respectively to form a uniform slurry.

[0105] The prepared slurry was poured into a specified mold and then covered with a film. One day later, the specimens were demolded and cured at 20±2℃ and a relative humidity greater than 95%. The tensile and flexural properties of the specimens were tested after 28 days. The tensile and flexural strengths are shown in Table 1. The tensile stress-strain curves and the flexural stress-flexural displacement curves are shown in Table 1. Figure 2 and Figure 4 middle.

[0106] Comparative Example 3

[0107] A method for preparing a cementitious material includes the following steps: adding 10.0 parts of silicate cement (P·II) and 3.3 parts of fine aggregate (quartz sand) to 4.5 parts of water, adding 0.05 parts of polycarboxylate superplasticizer, and stirring at speeds of 140 and 285 rpm for 2 minutes respectively to form a uniform slurry.

[0108] The prepared slurry was poured into a specified mold and then covered with a film. One day later, the specimens were demolded and cured at 20±2℃ and a relative humidity greater than 95%. The tensile and flexural properties of the specimens were tested after 28 days. The tensile and flexural strengths are shown in Table 1. The tensile stress-strain curves and the flexural stress-flexural displacement curves are shown in Table 1. Figure 1 and Figure 2 middle.

[0109] Comparative Example 4

[0110] A method for preparing a cementitious material includes the following steps: adding 10.0 parts of silicate cement (P·Ⅱ) to 4.5 parts of water, adding 0.05 parts of polycarboxylate superplasticizer, and stirring at speeds of 140 and 285 rpm for 4 minutes respectively to form a uniform slurry.

[0111] The prepared slurry was poured into a specified mold and then covered with a film. One day later, the specimens were demolded and cured at 20±2℃ and a relative humidity greater than 95%. The tensile and flexural properties of the specimens were tested after 28 days. The tensile and flexural strengths are shown in Table 1. The tensile stress-strain curves and the flexural stress-flexural displacement curves are shown in Table 1. Figure 2 and Figure 4 middle.

[0112] Comparative Example 5

[0113] A method for preparing a cementitious material includes the following steps: 10.0 parts of silicate cement (P·II), 3.3 parts of fine aggregate (quartz sand), and 0.004 parts of microfibers with a tensile strength of 1600 MPa and a strain rate of 7% are mixed evenly and then added to 4.5 parts of water. 0.05 parts of polycarboxylate superplasticizer are added, and the mixture is stirred at 140 rpm and 285 rpm for 4 minutes each to form a uniform slurry.

[0114] The prepared slurry was poured into a specified mold and then covered with a film. One day later, the specimens were demolded and cured at 20±2℃ and a relative humidity greater than 95%. The tensile and flexural properties of the specimens were tested after 28 days. The tensile and flexural strengths are shown in Table 1. The tensile stress-strain curves and the flexural stress-flexural displacement curves are shown in Table 1. Figure 2 and Figure 4 middle.

[0115] *There is no national standard for tensile strength testing. The tensile strength was obtained by strain control method, with the strain applied at a rate of 0.5% / min. The flexural strength was tested at three points, with the specimen size meeting GB / T 17671-2021, and the flexural displacement loading rate being 0.2 mm / min.

[0116] In addition, the microfibers in the above embodiments can also be derived from organic fibers, meeting the following requirements: length 8~18mm, diameter 0.01~0.04mm, strain rate greater than or equal to 5.0%, and tensile strength greater than 1000MPa. The flexural strength and tensile strength of the low-carbon, high-toughness cementitious material based on kaolin tailings prepared according to the above conditions are similar to those in Examples 1-7, and it can also exhibit extremely high tensile and flexural strength. The silicate cement can also be P·I type conforming to GB175-2023 General-Purpose Silicate Cement.

[0117] As shown in Table 1, the cementitious material prepared by this invention exhibits superior tensile and flexural strength compared to silicate-based cementitious materials. A comparison of the mechanical strength of Examples 1-7 and Comparative Examples 1-5 shows that the tensile strength of the high-toughness, low-carbon cementitious material based on kaolin tailings is increased by approximately 1 MPa, and the flexural strength can be increased by up to 3 MPa. Figure 1 , Figure 2 The figures show the tensile stress versus tensile strain curves of the specimens prepared in Examples 1-7 and Comparative Examples 1-5 at 28 days of age. Figure 3 , Figure 4 The figures show the flexural stress versus flexural displacement curves of the specimens prepared in Examples 1-7 and Comparative Examples 1-5 at 28 days of age, respectively. Figures 1-4 It can be seen that the cementitious material prepared based on the present invention exhibits superior tensile properties and strain-hardening ability compared to the control example. The optimal embodiment is Example 7.

[0118] Table 1. Tensile and flexural strengths of the products obtained in Examples 1-9 and Comparative Examples 1-5 at 28 days of age.

[0119]

[0120] Existing research indicates that during the production stage of building materials, the carbon emissions of ordinary silicate cement and clinker are 735 and 850 kgCO2 / t, respectively. The carbon emissions of gypsum (anhydrous gypsum and dihydrate gypsum), stone powder, and calcination tailings are 33, 2.19, and 127 kgCO2 / t, respectively. Examples 1-7, compared to Control Examples 3-5, show a reduction in carbon emissions of 342.5 kgCO2 / t, representing a relative reduction of 42.4%.

Claims

1. A low-carbon, high-toughness cementitious material based on kaolin tailings, characterized in that: It is composed of the following components in parts by weight: 4.0-5.5 parts silicate cement, 3.0-4.0 parts kaolin tailings, 1.5-2.0 parts calcium carbonate, 0.005-0.05 parts microfiber, 0.5-1 parts gypsum, and 0-3.3 parts fine aggregate.

2. The low-carbon, high-toughness cementitious material based on kaolin tailings according to claim 1, characterized in that: The silicate cement is either P·I silicate cement or P·II silicate cement.

3. The low-carbon, high-toughness cementitious material based on kaolin tailings according to claim 1, characterized in that: The specific surface area of ​​the kaolin tailings is 300~500m². 2 / kg.

4. The low-carbon, high-toughness cementitious material based on kaolin tailings according to claim 1, characterized in that: The calcium carbonate is derived from one or more of limestone, calcite, light calcium carbonate, or nano-calcium carbonate.

5. The low-carbon, high-toughness cementitious material based on kaolin tailings according to claim 1, characterized in that: The microfibers are polyvinyl alcohol fibers with a length of 8-18 mm, a diameter of 0.01-0.04 mm, a strain rate of ≥5.0%, and a tensile strength of ≥1000 MPa.

6. The low-carbon, high-toughness cementitious material based on kaolin tailings according to claim 1, characterized in that: The gypsum is derived from anhydrite or dihydrate gypsum.

7. The low-carbon, high-toughness cementitious material based on kaolin tailings according to claim 1, characterized in that: The fine aggregate is manufactured sand, standard sand, or quartz sand with a particle size of less than 5 mm.

8. A method for preparing a low-carbon, high-toughness cementitious material based on kaolin tailings according to any one of claims 1 to 7, characterized in that, Includes the following steps: Step 1: Lightly burn the kaolin tailings and then cool them to room temperature. Step two: Grind the material obtained in step one to form a specific surface area of ​​400~700 m². 2 / kg of powder; Step 3: Silicate cement, calcium carbonate, gypsum, fine aggregate, microfiber and the powder obtained in step 2 are stirred and mixed evenly to obtain a low-carbon and high-toughness cementitious material based on kaolin tailings.

9. The method for preparing low-carbon, high-toughness cementitious material based on kaolin tailings according to claim 8, characterized in that: In step one, the temperature for the light calcination treatment is 500~800℃, and the time is 120~240 minutes.

10. The method for preparing low-carbon, high-toughness cementitious material based on kaolin tailings according to claim 8, characterized in that: In step three, the stirring speed is 140~285 rpm and the time is 4~10 minutes.

Images