A fiber-containing early-strength ductile cementitious material and a method for preparing the same

Abstract

The present application belongs to the technical field of road engineering materials, and relates to an early-strength tough cementitious material containing fibers and a preparation method thereof. The early-strength tough cementitious material contains rock powder, blast furnace slag, fibers and an alkaline activator, the mass ratio of the rock powder and the blast furnace slag is (5-7):(3-5), the mass of the fibers is less than 2% of the sum of the masses of the rock powder and the blast furnace slag, and the mass of the alkaline activator is 5%-10% of the sum of the masses of the rock powder and the blast furnace slag. The present application provides an early-strength tough cementitious material. The material uses rock powder, blast furnace slag powder, fibers and an alkaline activator in a specific proportion as raw materials, fully utilizes solid waste materials, and plays a synergistic effect among the solid waste materials, so that the cementitious material with excellent working performance and high strength is prepared by a simple method and at a low cost.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of road engineering materials, and relates to a fiber-containing early-strength toughness cementitious material and a preparation method thereof, in particular to an early-strength toughness cementitious material using waste granite and dolomite and a preparation method thereof. BACKGROUND

[0002] Under the background of accelerating urbanization, road construction and maintenance are crucial for the sustainable development of cities. Traditional road base materials usually use cement, lime and natural aggregate resources such as stone, sand and gravel, but this approach has some environmental and sustainability problems, including resource depletion, energy consumption, land destruction, air and water pollution, etc. Especially, the production of raw materials such as cement and lime is accompanied by a large amount of carbon dioxide emissions and high energy consumption, which is not conducive to environmental protection and energy saving. By alkali activation, solid waste-based geopolymer cementitious materials not only have mechanical properties comparable to or even better than ordinary Portland cement, but also have a more environmentally friendly production process, and are considered as a very promising alternative to Portland cement.

[0003] In industrial production and urban life, a large amount of waste will pollute the environment. A large amount of granite and dolomite waste will be generated during the processing and mining of granite and dolomite. These wastes are generally treated by piling up or landfilling, and some are mixed with household garbage or directly discharged into rivers, which will cause serious harm to land and water sources, and even threaten human health if the powder is inhaled. In addition, in the process of blast furnace ironmaking, gangue in ore, ash in fuel and non-volatile components in solvent (usually limestone) will form blast furnace slag. As an industrial by-product, slag is usually piled up in the open air for many years, not only occupying a large amount of land, but also causing serious pollution to the atmosphere, soil and groundwater system due to dust and heavy metal ions leaching with rainwater. Therefore, how to realize large-scale recycling of these industrial solid wastes, reduce environmental hazards and improve social and economic benefits has always been the focus of attention for solid waste treatment departments. If the above waste can be used in the preparation of cementitious materials, not only the use of cement and lime in cementitious materials can be reduced, but also the utilization rate of waste can be improved, which has high research value. However, alkali-activated slag cementitious materials have a serious shrinkage problem, and the shrinkage of alkali-activated slag cementitious materials is much larger than that of ordinary Portland cement. Due to shrinkage, alkali-activated cementitious materials are more prone to cracking, which has a serious negative impact on their durability. In addition, alkali-activated slag cementitious materials have a very fast setting speed, and traditional retarders suitable for cement have little effect, and there are also problems of carbonation, brittleness, alkali-aggregate reaction, etc., which also limit the application of alkali-activated slag.

[0004] The patent with publication number CN116332540A provides a green and environmentally friendly alkali-activated cementitious material and a preparation method thereof. The patent mixes waste granite stone powder, blast furnace slag, metakaolin, and municipal solid waste incineration bottom ash according to a certain ratio, fully ball-mills to obtain admixture, and then mixes the admixture with an alkali activator to prepare a cementitious material. Through the above-mentioned manner, the invention can improve the utilization rate of solid waste materials while utilizing the synergistic effect between the solid waste materials, improve the performance of the cementitious material, and relieve the expansion and deformation of municipal solid waste incineration bottom ash, forming a cementitious material with good workability and high mechanical properties. However, the method requires a high water demand due to the addition of metakaolin, and the process is complicated and the technology is complex. Moreover, metakaolin needs to be treated by high-temperature calcination of kaolin, which will bring a large amount of energy consumption and increase the processing cost. In addition, it cannot alleviate the shrinkage and cracking problems of alkali-activated slag. SUMMARY

[0005] In view of the deficiencies of the prior art, the present invention aims to provide a fiber-containing early-strength tough cementitious material and a preparation method thereof. By reasonably mixing rock powder, blast furnace slag powder, and fiber, the invention fully utilizes solid waste materials to achieve synergistic effect, thereby improving the performance of the cementitious material, alleviating the shrinkage and cracking of alkali-activated slag, and other problems such as rapid setting, and preparing a cementitious material with good workability and high strength.

[0006] According to a first aspect of the present invention, a fiber-containing early-strength tough cementitious material is provided, containing rock powder, blast furnace slag, fiber, and alkali activator. The mass ratio of the rock powder and blast furnace slag is (5-7):(3-5), the mass of the fiber is less than 2% of the sum of the mass of the rock powder and blast furnace slag, and the mass of the alkali activator is 5%-10% of the sum of the mass of the rock powder and blast furnace slag.

[0007] Preferably, the rock powder is at least one of granite stone powder and dolomite stone powder.

[0008] Preferably, the mass ratio of the granite stone powder and dolomite stone powder is (2-5):(1-5).

[0009] Preferably, the granite stone powder is waste granite stone powder, and the dolomite stone powder is waste dolomite stone powder.

[0010] Preferably, the fiber is a polymer fiber.

[0011] Preferably, the polymer fiber is a polypropylene fiber.

[0012] Preferably, the alkali activator is one or both of sodium hydroxide and water glass.

[0013] According to another aspect of the present application, there is provided a method for preparing any of the early-strength and toughness fiber-containing cementitious materials, comprising the following steps:

[0014] (1) mixing rock powder, blast furnace slag and fiber, and then ball-milling to obtain a mixture; the mass ratio of the rock powder to the blast furnace slag is (5-7):(3-5), and the mass of the fiber is less than 2% of the total mass of the rock powder and the blast furnace slag;

[0015] (2) adding an alkaline activator to the mixture obtained in step (1), wherein the mass of the alkaline activator is 5%-10% of the total mass of the rock powder and the blast furnace slag, and then uniformly mixing to obtain the early-strength and toughness fiber-containing cementitious material.

[0016] Preferably, the rock powder is at least one of granite rock powder and dolomite rock powder.

[0017] Preferably, the mass ratio of the granite rock powder to the dolomite rock powder is (2-5):(1-5).

[0018] Preferably, the fiber is a polymer fiber.

[0019] Preferably, the polymer fiber is a polypropylene fiber.

[0020] Preferably, the specific surface area of the mixture is greater than 600 m 2 / kg.

[0021] Overall, compared with the prior art, the above technical solutions conceived by the present application mainly have the following technical advantages:

[0022] (1) The present application provides an early-strength and toughness cementitious material. The material uses rock powder, blast furnace slag powder, fiber and alkaline activator in a specific proportion as raw materials, fully utilizes solid waste materials, and plays a synergistic effect among the solid waste materials, so as to prepare a cementitious material with excellent workability and high strength by a simple method and at a low cost, thereby bringing significant economic and environmental benefits. The early-strength and toughness cementitious material has a 1-day compressive strength of more than 10 MPa and a 7-day compressive strength of more than 30 MPa; and has good toughness, with a 28-day flexural strength of 9 MPa.

[0023] (2) The present application does not need to add metakaolin, thereby eliminating the energy consumption generated by calcining kaolin to obtain metakaolin, and also reducing the water demand in the preparation process of the cementitious material (the material properties of metakaolin itself determine that it has a particularly high demand for water, which easily leads to the formation of a cementitious material with excessively high porosity in the preparation process).

[0024] (3) The application can improve the utilization rate of solid waste materials, utilize the synergistic effect between the solid waste materials, improve the performance of cementitious materials, alleviate the dry shrinkage and cracking problem of alkali-activated slag, reduce the water consumption, realize the setting retarding of alkali-activated slag, and form cementitious materials with good working performance and high mechanical properties.

[0025] (4) Preferably, by controlling the amount of each raw material within a reasonable range, the synergistic effect between the raw materials can be effectively utilized, the waste granite stone powder and the waste dolomite stone powder can be mixed in a large amount, the waste granite stone powder, the waste dolomite stone powder and the fiber can be used to improve the activation effect of the blast furnace slag, alleviate the dry shrinkage and cracking problem of alkali-activated slag, reduce the water consumption, realize the setting retarding of alkali-activated slag, and thus obtain green and environment-friendly early-strength and toughness alkali-activated cementitious materials with good working performance and high mechanical properties.

[0026] (5) Preferably, by skillfully designing the proportion of the waste granite stone powder, the waste dolomite stone powder, the blast furnace slag powder, the fiber and the alkali activator, the application not only greatly improves the application amount of the waste granite stone powder and the waste dolomite stone powder which are usually difficult to effectively utilize, but also significantly improves the performance of the blast furnace slag-based alkali-activated material by means of the pore filling effect of the waste stone powder. This not only reduces the setting rate of the blast furnace slag-based cementitious material, improves the working performance and the mechanical properties, but also helps to reduce the amount of alkali activator. At the same time, the hydrophobicity of the waste granite stone powder and the waste dolomite stone powder can reduce the water demand of the cementitious material, thereby reducing the production cost. In addition, the increase of the calcium oxide content in the alkali-activated material can rapidly generate C-S-H gel through the alkali activator in an alkaline environment, thereby improving the compressive strength; the calcium element in the waste dolomite stone powder can rapidly generate early strength with the slag in an alkaline environment; at the same time, the addition of the waste granite stone powder, the waste dolomite stone powder and the fiber can also effectively slow down the dry shrinkage deformation of the blast furnace slag powder in an alkaline environment, providing a more simple and efficient method for the comprehensive application of the blast furnace slag powder, the waste granite stone powder and the waste dolomite stone powder. The addition of the fiber makes the alkali-activated cementitious material have good anti-fracture performance, the fracture toughness is maintained at a high level, the 28-day flexural strength can reach about 9MPa, and the shrinkage value of the cementitious material can be reduced by about 20%~40%, which has a significant inhibitory effect on shrinkage and cracking.

[0027] (6) Preferably, the early-strength and toughness gelatinous material provided by using waste granite and dolomite releases silicon and aluminum elements under the action of a corresponding alkaline activator to generate hydrated silica and zeolite-like products, thereby achieving high strength. Therefore, the gelatinous material can meet the required mechanical properties without adding cement, lime and other raw materials, and compared with the traditional preparation method, the carbon dioxide emission and energy consumption are greatly reduced. In addition, the present application uses a large amount of industrial solid waste materials such as waste granite stone powder, waste dolomite stone powder and blast furnace slag powder, avoids resource waste and solves the environmental pollution problem of solid waste. The raw material acquisition cost is low, the preparation process is simple, and the actual production and application requirements can be met. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 Comparison of the dry shrinkage performance of the gelatinous materials prepared for Example 1 and Comparative Example 3. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0030] The early-strength and toughness gelatinous material provided by the present application contains rock powder, blast furnace slag, fiber and alkaline activator, the mass fraction ratio of the rock powder and blast furnace slag is (5-7):(3-5), the mass of the fiber is less than 2% of the sum of the mass of the rock powder and blast furnace slag, and the mass of the alkaline activator is 5%-10% of the sum of the mass of the rock powder and blast furnace slag.

[0031] In some embodiments, the rock powder is at least one of granite stone powder and dolomite stone powder.

[0032] In some embodiments, the mass fraction ratio of the granite stone powder and dolomite stone powder is (2-5):(1-5).

[0033] In some embodiments, the granite stone powder is waste granite stone powder, and the dolomite stone powder is waste dolomite stone powder.

[0034] Preferably, the waste granite stone powder contains the following components in terms of mass fraction:

[0035] Na2O 2%~6%, MgO 0.4%~1.2%, Al2O3 10%~20%, SiO2 60%~75%, Fe2O3 1.2%~2.0%, K2O 4%~5%.

[0036] Preferably, the waste dolomite rock powder contains the following components by mass fraction:

[0037] MgO 25%~40%, Al2O3 0.1%~0.5%, SiO2 12%~24%, CaO 35%~55%, Fe2O3 0.1%~0.4%.

[0038] Preferably, the blast furnace slag contains the following components by mass fraction:

[0039] Na2O 0.1%~0.5%, MgO 5%~10%, Al2O3 10%~20%, SiO2 20%~40%, SO3 1.5%~3%, CaO 30%~50%, K2O 0.2%~0.6%, Fe2O3 0.2%~0.6%, TiO2 0.6%~1.2%, MnO 0.2~0.5%.

[0040] Preferably, the alkaline activator is one of sodium hydroxide and water glass, or a composite of both.

[0041] In some embodiments, the application further provides a preparation method of the early-strength and high-toughness cementitious material described above, comprising the following steps:

[0042] (1) mixing the rock powder (preferably granite rock powder and dolomite rock powder), blast furnace slag and fiber according to a predetermined ratio, and then fully ball milling to obtain a mixture;

[0043] (2) mixing the mixture and the alkaline activator according to a predetermined ratio to obtain a cementitious material.

[0044] In step S1, the specific surface area of the mixture obtained after fully ball milling is greater than 600 m 2 / kg.

[0045] After mixing the cementitious material obtained in step S2 with water and natural curing, the 1d compressive strength is 10~18MPa, the 3d compressive strength is 20~30MPa, the 7d compressive strength is 28~45MPa, the 28d compressive strength is 35~55MPa, the 1d flexural strength is 1.5~4MPa, the 3d flexural strength is 2.2~6MPa, the 7d flexural strength is 3.4~7MPa, and the 28d flexural strength is 4.6~8.8MPa.

[0046] The water-cement ratio of water to the cementitious material is 1:2.

[0047] The early-strength and toughness cementing material and the preparation method thereof provided by the present application are described below in combination with specific examples and comparative examples.

[0048] Example 1

[0049] The early-strength and toughness cementing material provided by the present application comprises the following components in terms of mass fraction:

[0050] The mass ratio of the waste granite stone powder, the waste dolomite stone powder and the blast furnace slag is 3:2:5;

[0051] The fiber is 2% of the total mass of the waste granite stone powder, the waste dolomite stone powder and the blast furnace slag;

[0052] The alkaline activator is 10% of the total mass of the waste granite stone powder, the waste dolomite stone powder and the blast furnace slag;

[0053] The alkaline activator sodium hydroxide is 2% of the total mass of the waste granite stone powder, the waste dolomite stone powder and the blast furnace slag;

[0054] In the present example, the chemical composition of the waste granite stone powder is as follows:

[0055] Na2O 3.09%, MgO 0.91%, Al2O3 13.41%, SiO2 73.60%, Fe2O3 1.94%, K2O 4.53%.

[0056] The chemical composition of the waste dolomite stone powder is as follows:

[0057] MgO 34.34%, Al2O3 0.13%, SiO2 19.38%, CaO 45.99%, Fe2O3 0.12%.

[0058] The chemical composition of the blast furnace slag is as follows:

[0059] Na2O 0.41%, MgO 9.79%, Al2O3 15.34%, SiO2 32.40%, SO3 2.83%, CaO 37.10%, K2O 0.34%, Fe2O3 0.29%, TiO2 0.97%, MnO 0.34%.

[0060] The present example also provides a preparation method of the above early-strength and toughness cementing material using waste granite and dolomite, which specifically comprises the following steps:

[0061] S1, the waste granite stone powder, the waste dolomite stone powder, the blast furnace slag powder and the fiber are mixed according to the above-mentioned ratio, and then ball-milled in a ball mill for a certain time, so that the specific surface area of the admixture obtained after sufficient ball-milling is greater than 600 m2 / kg;

[0062] S2, the admixture is mixed with the alkaline activator solution (water glass and sodium hydroxide) according to the above ratio to obtain a cementing material.

[0063] Examples 2-5 and Comparative Examples 1-5

[0064] Examples 2-5 and Comparative Examples 1-5 each provide a cementing material using waste granite and dolomite, and differ from Example 1 in that the composition of the cementing material is changed. The preparation method is consistent with that of Example 1, and is not repeated here. The corresponding raw material compositions of the examples and comparative examples are shown in Table 1.

[0065] Table 1 Weight fractions of each raw material in the cementing materials provided by Examples 2-5 and Comparative Examples 1-5

[0066]

[0067] The working performance and mechanical properties of the cementing materials prepared by Examples 2-5 and Comparative Examples 1-5 were tested. In the mechanical property test, cementing material neat paste was used, water was added according to a water-cement ratio of 1:2, and natural curing was performed for 1d, 3d, 7d, and 28d. The results are shown in Table 2.

[0068] Table 2 Properties of the cementing materials prepared by Examples 2-5 and Comparative Examples 1-5

[0069]

[0070] As shown in the table above, the working performance (setting time, stability, standard consistency water consumption, and fluidity) of Examples 1-5 all meet the specifications. Examples 1, 2, 3, and 4 have a 7-day compressive strength of 40 MPa, reaching over 75% of the working strength, exhibiting early strength characteristics, and can be used as repair materials. Example 5 has a slightly lower compressive strength than Examples 1-4, but still meets the strength requirements of practical engineering projects, and can be used for auxiliary facilities with slightly lower strength requirements, such as sidewalk paving stones. In this case, the material cost is also reduced due to the lower slag content. Examples 1, 2, and 3 have a 28-day flexural strength of over 6.0 MPa, exhibiting high fracture toughness. While the flexural strength of Examples 4 and 5 is lower than that of Examples 1, 2, and 3, it still reaches over 4 MPa. Furthermore, compared to the examples, the comparative examples have relatively poor mechanical properties. In Comparative Example 1, no alkaline activator was used, making it difficult to create the required alkaline environment and effectively activate the activity of the raw materials, resulting in a low strength of the cementitious material. In Comparative Example 2, no waste granite powder, waste dolomite powder, or fiber was added, leading to excessively fast setting time and a significant decrease in flexural strength. At this point, the system only contained slag, resulting in low utilization of waste stone powder and poor environmental benefits. However, its compressive strength could still reach over 50 MPa. In Comparative Example 3, no fiber was added, leading to a decrease in the flexural strength of the cementitious material, but its compressive strength could reach over 40 MPa. At this point, the utilization rate of waste stone powder in the system was relatively high, showing some environmental benefits compared to Comparative Example 2. In Comparative Example 4, only water glass was used as the alkaline activator, and in Comparative Example 5, only sodium hydroxide was used as the alkaline activator. Compared with a mixed alkaline activator (water glass and sodium hydroxide solution), the strength of the cementitious material was significantly reduced.

[0071] The shrinkage test results of Example 1 and Comparative Example 3 are as follows: Figure 1 As shown, by Figure 1 It can be seen that the shrinkage value of Example 1 at different ages is less than that of Comparative Example 3. This indicates that the addition of fibers can reduce the shrinkage value of cementitious materials by about 20% to 40%, and has a significant inhibitory effect on shrinkage cracking.

[0072] This invention effectively utilizes the synergistic effect between raw materials by controlling the dosage of each raw material within a reasonable range. While incorporating a large amount of waste granite powder and waste dolomite powder, it also utilizes the waste granite powder, waste dolomite powder, and fiber to synergistically improve the activation effect of blast furnace slag, alleviate the drying shrinkage and cracking problem of alkali-activated slag, reduce water consumption, and achieve slow setting of alkali-activated slag. This results in a green and environmentally friendly early-strength and tough alkali-activated cementitious material with good workability and high mechanical properties.

[0073] In summary, the application can improve the utilization rate of solid waste materials, utilize the synergies between the solid waste materials, improve the performance of cementitious materials, alleviate the dry shrinkage and cracking problem of alkali-activated slag, reduce the water consumption, realize the slow setting of alkali-activated slag, and form cementitious materials with good working performance and high mechanical performance.

[0074] Those skilled in the art can understand that the above description is only the preferred embodiment of the present application, and is not used to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A fibre-containing early-strength, ductile cementitious material, characterised in that, The rock powder, blast furnace slag, fiber and alkaline activator are contained, the mass ratio of the rock powder and blast furnace slag is 6:4, the mass of the fiber is less than 2% of the sum of the mass of the rock powder and blast furnace slag, and the mass of the alkaline activator is 5%-10% of the sum of the mass of the rock powder and blast furnace slag. The rock powder is granite rock powder and dolomite rock powder, and the mass ratio of the granite rock powder and dolomite rock powder is 5:

1. The alkaline activator is sodium hydroxide and water glass.

2. The early-strength, ductile, fiber-containing cementitious material of claim 1, wherein, The granite rock powder is waste granite rock powder, and the dolomite rock powder is waste dolomite rock powder.

3. The fiber-containing early-strength, ductile cementitious material of claim 1, wherein, The fiber is a polymer fiber.

4. The early-strength, ductile, fiber-containing cementitious material of claim 3, wherein, The polymer fiber is a polypropylene fiber.

5. A process for the production of a fibre-containing early-strength ductile cementitious material according to any one of claims 1 to 4, characterised in that, The method comprises the following steps: (1) mixing the rock powder, blast furnace slag and fiber, and then fully ball milling to obtain a mixture, wherein the mass ratio of the rock powder and blast furnace slag is 6:4, and the mass of the fiber is less than 2% of the sum of the mass of the rock powder and blast furnace slag; The rock powder is granite rock powder and dolomite rock powder, and the mass ratio of the granite rock powder and dolomite rock powder is 5:

1. (2) adding an alkaline activator to the mixture obtained in step (1), wherein the mass of the alkaline activator is 5%-10% of the sum of the mass of the rock powder and blast furnace slag, and fully mixing to obtain the early-strength and toughness cementitious material containing the fiber.

6. The method of producing a fiber-containing early-strength ductile cementitious material according to claim 5, characterized by, The specific surface area of the blend is greater than 600 m 2 / kg.

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