Solid waste-based low-carbon cement and preparation method thereof

Abstract

The invention belongs to the technical field of low-carbon cement, and particularly relates to solid-waste-based low-carbon cement and a preparation method thereof. The solid waste-based low-carbon cement provided by the invention comprises the following components in parts by weight: 50-60 parts of slag; 15 to 20 parts of fly ash; 10-15 parts of carbide slag; 8-12 parts of limestone; 5-10 parts of steel slag; 8-10 parts of a functional compound; 4-6 parts of a composite alkali activator; according to the present invention, the solid waste slag, the fly ash and the carbide slag are adopted as the main components so as to achieve the reutilization of the solid waste, and the functional compound is added to modify the low-carbon cement so as to improve the anti-cracking performance and the self-repairing performance of the low-carbon cement, and the low-carbon cement provided by the invention has characteristics of high compressive strength, high breaking strength, low shrinkage rate, high anti-cracking performance, and wide application prospect. And the cement also has certain self-repairing performance, and can meet the market demand of functional low-carbon cement.

Description

Technical Field

[0001] This invention belongs to the field of low-carbon cement technology, specifically relating to a solid waste-based low-carbon cement and its preparation method. Background Technology

[0002] Cement, as an important basic building material, has advantages such as convenient raw material availability, low price, and high construction flexibility. Its annual consumption is enormous, resulting in significant carbon emissions and a serious impact on global climate change. To reduce carbon emissions from the cement industry, low-carbon cement has become a new direction for green research and development. Low-carbon cement is a cement system that significantly reduces carbon dioxide emissions during production and use by optimizing raw materials, processes, or mineral composition. Meanwhile, solid wastes such as slag, fly ash, and red mud are generated in huge quantities annually, originating from a wide range of industries including energy, metallurgy, mining, chemicals, and construction. These large amounts of solid waste not only occupy land resources but also cause serious environmental pollution, making the recycling and reuse of solid waste resources urgent. Currently, many studies have successfully applied solid waste to low-carbon cement, simultaneously achieving the utilization of solid waste resources and the development of a low-carbon, green cement industry.

[0003] Chinese patent application CN202311096659.7 discloses a red mud-based low-carbon composite cement and its preparation method. The raw materials for the red mud-based low-carbon composite cement include a cementitious component, an activator component, and an admixture component. The cementitious component includes red mud, auxiliary cementitious materials, and gypsum-based solid waste. The activator component includes an alkali activator, and the admixture component includes a retarder and an interface reinforcing agent. Its preparation method is simple, requiring neither red mud dealkalization nor high-temperature calcination, truly achieving low-carbon, low-energy-consumption, and low-cost green and environmentally friendly cement preparation. The resulting low-carbon composite cement has compressive strength comparable to or even higher than that of 425 or 525 cement. (Application CN20251041) Chinese patent application 2040.5 discloses a method for preparing low-carbon cement based on construction waste. The method involves first preparing a slurry from the construction waste, then adding an activator, hydrothermal additive powder, and water to the slurry. A deep hydrothermal reaction is then carried out in a high-pressure autoclave under high temperature and pressure to obtain a low-carbon cement precursor. This precursor is then calcined to obtain clinker, which is finally mixed with mineral admixtures and ground into a fine powder to obtain the low-carbon cement. The resulting low-carbon cement exhibits high compressive and flexural strength, with a strength grade of 32.5. While these patents utilize solid waste to prepare low-carbon cement with good compressive strength, the resulting low-carbon cement only meets basic construction needs and is not suitable for construction fields requiring functional applications. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a solid waste-based low-carbon cement and its preparation method. The low-carbon cement provided by this invention uses solid waste slag, fly ash, and carbide slag as its main components, realizing the reuse of solid waste. At the same time, functional composites are added to modify the low-carbon cement, improving its crack resistance and self-healing properties. The low-carbon cement provided by this invention has high compressive strength and flexural strength, low shrinkage rate, and high crack resistance, as well as certain self-healing properties, which can meet the market demand for functional low-carbon cement.

[0005] The technical solution adopted by the present invention to achieve the above objectives is as follows: A solid waste-based low-carbon cement comprises the following components by weight: 50-60 parts slag; 15-20 parts fly ash; 10-15 parts calcium carbide slag; 8-12 parts limestone; 5-10 parts steel slag; 8-10 parts functional composite material; and 4-6 parts composite alkali activator.

[0006] Furthermore, the composite alkali activator is composed of sodium hydroxide and sodium silicate.

[0007] Furthermore, the mass ratio of sodium hydroxide to sodium silicate is 1:0.8-1.

[0008] Furthermore, the preparation method of the functional complex is as follows: S1. Immerse polypropylene fibers in xylene, stir evenly, add modifier and benzoyl peroxide, and continue stirring and reacting at 100-110℃ for 3-4 hours to obtain functionalized polypropylene fibers. S2. Immerse the functionalized polypropylene fiber in ethanol, stir until homogeneous, add hydroxyapatite, sonicate, and continue stirring at 50-60℃ for 4-5 hours to obtain the functionalized composite.

[0009] Further, in step S1, the mass ratio of polypropylene fiber, modifier, and benzoyl peroxide is 1:0.3-0.4:0.01-0.02.

[0010] Furthermore, the modifier in step S1 is composed of 4-vinylbenzoic acid and methyl allyl disulfide.

[0011] Furthermore, the mass ratio of 4-vinylbenzoic acid to methyl allyl disulfide is 1:0.8-1.

[0012] Furthermore, the mass ratio of the functionalized polypropylene fiber to hydroxyapatite in step S2 is 1:0.8-1.

[0013] Furthermore, the ultrasonic power in step S2 is 400-500W, and the ultrasonic time is 0.5-1h.

[0014] The present invention also provides a method for preparing solid waste-based low-carbon cement, comprising the following steps: mixing industrial solid waste, fly ash, limestone, functional composite material and composite alkali activator evenly according to the mass ratio to obtain solid waste-based low-carbon cement.

[0015] The solid waste-based low-carbon cement provided by this invention, with a water-binder ratio of 0.5, can be applied to the construction and road construction fields after being mixed evenly with water.

[0016] The present invention has the following beneficial effects: 1. In this invention, under the action of benzoyl peroxide catalyst, 4-vinylbenzoic acid (carboxylic acid group) and methyl allyl disulfide (disulfide bond) are grafted onto polypropylene fibers through a chemical reaction to obtain functionalized polypropylene fibers. The modified functionalized polypropylene fibers are easier to disperse in cement. In this invention, the functionalized polypropylene fibers are further reacted with hydroxyapatite. Through the coordination of the carboxylic acid groups grafted on the functionalized polypropylene fibers with the calcium ions rich on the surface of hydroxyapatite, a stable calcium-carboxylic acid complex is formed, thereby firmly binding the functionalized polypropylene fibers and hydroxyapatite together to obtain a functionalized composite.

[0017] 2. The polypropylene fiber molecules in the functionalized composite of this invention can form a network structure support system through three-dimensional random distribution in the cement components, effectively inhibiting the generation of microcracks. The hydroxyapatite grafted onto the polypropylene fiber molecules can promote more complete hydration reaction, reduce the generation of micropores, and also fill micropores and cracks. The strong bond between hydroxyapatite and polypropylene fiber molecules helps to improve the strength of the network structure, enhance the compactness of the low-carbon cement structure, and improve the mechanical properties of low-carbon cement. In particular, the polypropylene fiber molecules and hydroxyapatite can synergistically enhance each other, significantly improving the crack resistance of low-carbon cement. In addition, the disulfide bonds grafted onto the polypropylene fiber molecules can endow low-carbon cement with a certain self-healing property through dynamic exchange reaction, enabling the self-healing function of fine cracks.

[0018] 3. The low-carbon cement provided by this invention uses solid waste slag, fly ash, and carbide slag as the main components, realizing the reuse of solid waste. At the same time, functional composites are added to modify the low-carbon cement, improving its crack resistance and self-healing properties. The low-carbon cement provided by this invention has high compressive strength and flexural strength, low shrinkage rate and high crack resistance, and also has a certain degree of self-healing properties, which can meet the market demand for functional low-carbon cement. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] In this invention, the particle size of low-carbon cement slag, fly ash, carbide slag, limestone, and steel slag is controlled within the range of 8-10 μm. Specifically, the slag contains no less than 40 wt% CaO, the fly ash contains no less than 65 wt% total SiO2 and Al2O3, the carbide slag contains no less than 60 wt% CaO, and the steel slag contains no less than 50 wt% CaO. The limestone has CAS number 1317-65-3; sodium hydroxide has CAS number 1310-73-2; and sodium silicate has CAS number 1344-0. 9-8; Hydroxyapatite CAS No. 1306-06-5 (particle size within 100nm); Polypropylene fiber diameter 10-20μm, length 3-5mm; Benzoyl peroxide CAS No. 94-36-0; 4-Vinylbenzoic acid CAS No. 1075-49-6; Methyl allyl disulfide CAS No. 2179-58-0; Xylene CAS No. 1330-20-7; Ethanol CAS No. 64-17-5; All chemical reagents are commercially available.

[0021] Example 1 A solid waste-based low-carbon cement comprises the following components by weight: 60 parts slag; 20 parts fly ash; 15 parts calcium carbide slag; 10 parts limestone; 10 parts steel slag; 10 parts functional composite material; and 6 parts composite alkali activator; wherein the composite alkali activator is composed of sodium hydroxide and sodium silicate in a mass ratio of 1:1.

[0022] The preparation method of the functional complex is as follows: S1. Polypropylene fibers are immersed in xylene and stirred evenly. Modifier and benzoyl peroxide are added, and the reaction is continued at 110°C for 3 hours. After the reaction is completed, the mixture is cooled, filtered, and the product is washed and dried to obtain functionalized polypropylene fibers. The mass ratio of polypropylene fibers, modifier, and benzoyl peroxide is 1:0.4:0.02. The modifier is composed of 4-vinylbenzoic acid and methyl allyl disulfide in a mass ratio of 1:1. S2. The functionalized polypropylene fiber was immersed in ethanol and stirred evenly. Hydroxyapatite was added, and after ultrasonic treatment, the mixture was stirred and reacted at 60°C for 4 hours. After the reaction was completed, the mixture was cooled, filtered, and the product was washed and dried to obtain the functionalized composite. The mass ratio of functionalized polypropylene fiber to hydroxyapatite was 1:1. The ultrasonic power was 500W and the ultrasonic time was 0.5h.

[0023] A method for preparing solid waste-based low-carbon cement includes the following steps: mixing industrial solid waste, fly ash, limestone, functional composite material, and composite alkali activator evenly according to the mass ratio to obtain solid waste-based low-carbon cement.

[0024] Example 2 A solid waste-based low-carbon cement comprises the following components by weight: 50 parts slag; 15 parts fly ash; 10 parts calcium carbide slag; 12 parts limestone; 7 parts steel slag; 8 parts functional composite material; and 4 parts composite alkali activator; wherein the composite alkali activator is composed of sodium hydroxide and sodium silicate in a mass ratio of 1:0.8.

[0025] The preparation method of the functional complex is as follows: S1. Polypropylene fibers are immersed in xylene and stirred evenly. Modifier and benzoyl peroxide are added, and the reaction is continued at 100°C for 4 hours. After the reaction is completed, the mixture is cooled, filtered, and the product is washed and dried to obtain functionalized polypropylene fibers. The mass ratio of polypropylene fibers, modifier, and benzoyl peroxide is 1:0.3:0.01. The modifier is composed of 4-vinylbenzoic acid and methyl allyl disulfide in a mass ratio of 1:0.8. S2. The functionalized polypropylene fiber was immersed in ethanol and stirred evenly. Hydroxyapatite was added, and after ultrasonic treatment, the mixture was stirred and reacted at 50°C for 4.5 hours. After the reaction was completed, the mixture was cooled, filtered, and the product was washed and dried to obtain the functionalized composite. The mass ratio of functionalized polypropylene fiber to hydroxyapatite was 1:0.8. The ultrasonic power was 400W and the ultrasonic time was 0.8 hours.

[0026] A method for preparing solid waste-based low-carbon cement includes the following steps: mixing industrial solid waste, fly ash, limestone, functional composite material, and composite alkali activator evenly according to the mass ratio to obtain solid waste-based low-carbon cement.

[0027] Example 3 A solid waste-based low-carbon cement comprises the following components by weight: 55 parts slag; 16 parts fly ash; 13 parts calcium carbide slag; 8 parts limestone; 5 parts steel slag; 9 parts functional composite material; and 5 parts composite alkali activator; wherein the composite alkali activator is composed of sodium hydroxide and sodium silicate in a mass ratio of 1:0.9.

[0028] The preparation method of the functional complex is as follows: S1. Polypropylene fibers are immersed in xylene and stirred evenly. Modifier and benzoyl peroxide are added, and the reaction is continued at 105℃ for 3.5 hours. After the reaction is completed, the mixture is cooled, filtered, and the product is washed and dried to obtain functionalized polypropylene fibers. The mass ratio of polypropylene fibers, modifier, and benzoyl peroxide is 1:0.35:0.015. The modifier is composed of 4-vinylbenzoic acid and methyl allyl disulfide in a mass ratio of 1:0.9. S2. The functionalized polypropylene fiber was immersed in ethanol and stirred evenly. Hydroxyapatite was added, and after ultrasonic treatment, the mixture was stirred and reacted at 55°C for 5 hours. After the reaction was completed, the mixture was cooled, filtered, and the product was washed and dried to obtain the functionalized composite. The mass ratio of functionalized polypropylene fiber to hydroxyapatite was 1:0.9. The ultrasonic power was 450W and the ultrasonic time was 1 hour.

[0029] A method for preparing solid waste-based low-carbon cement includes the following steps: mixing industrial solid waste, fly ash, limestone, functional composite material, and composite alkali activator evenly according to the mass ratio to obtain solid waste-based low-carbon cement.

[0030] Example 4 A solid waste-based low-carbon cement comprises the following components by weight: 52 parts slag; 18 parts fly ash; 12 parts calcium carbide slag; 9 parts limestone; 6 parts steel slag; 9 parts functional composite material; and 6 parts composite alkali activator; wherein the composite alkali activator is composed of sodium hydroxide and sodium silicate in a mass ratio of 1:1.

[0031] The preparation method of the functional complex is as follows: S1. Polypropylene fibers are immersed in xylene and stirred evenly. Modifier and benzoyl peroxide are added, and the reaction is continued at 100℃ for 3.5 hours. After the reaction is completed, the mixture is cooled, filtered, and the product is washed and dried to obtain functionalized polypropylene fibers. The mass ratio of polypropylene fibers, modifier, and benzoyl peroxide is 1:0.35:0.02. The modifier is composed of 4-vinylbenzoic acid and methyl allyl disulfide in a mass ratio of 1:0.9. S2. The functionalized polypropylene fiber was immersed in ethanol and stirred evenly. Hydroxyapatite was added, and after ultrasonic treatment, the mixture was stirred and reacted at 60°C for 5 hours. After the reaction was completed, the mixture was cooled, filtered, and the product was washed and dried to obtain the functionalized composite. The mass ratio of functionalized polypropylene fiber to hydroxyapatite was 1:0.8. The ultrasonic power was 480W and the ultrasonic time was 0.6 hours.

[0032] A method for preparing solid waste-based low-carbon cement includes the following steps: mixing industrial solid waste, fly ash, limestone, functional composite material, and composite alkali activator evenly according to the mass ratio to obtain solid waste-based low-carbon cement.

[0033] Comparative Example 1 Compared with Example 1, the composition of the solid waste-based low-carbon cement in this comparative example is different, with the addition of functionalized polypropylene fibers.

[0034] A solid waste-based low-carbon cement comprises the following components by weight: 60 parts slag; 20 parts fly ash; 15 parts calcium carbide slag; 10 parts limestone; 10 parts steel slag; 10 parts functionalized polypropylene fiber; and 6 parts composite alkali activator, wherein the composite alkali activator is composed of sodium hydroxide and sodium silicate in a mass ratio of 1:1.

[0035] The preparation method of functionalized polypropylene fiber is the same as step S1 in Example 1.

[0036] The preparation method of a solid waste-based low-carbon cement is the same as in Example 1.

[0037] Comparative Example 2 Compared with Example 1, the composition of the solid waste-based low-carbon cement in this comparative example is different, with the addition of polypropylene fibers.

[0038] A solid waste-based low-carbon cement comprises the following components by weight: 60 parts slag; 20 parts fly ash; 15 parts calcium carbide slag; 10 parts limestone; 10 parts steel slag; 10 parts polypropylene fiber; and 6 parts composite alkali activator, wherein the composite alkali activator is composed of sodium hydroxide and sodium silicate in a mass ratio of 1:1.

[0039] The preparation method of a solid waste-based low-carbon cement is the same as in Example 1.

[0040] Comparative Example 3 The composition of the solid waste-based low-carbon cement in this comparative example is different from that in Example 1.

[0041] A solid waste-based low-carbon cement comprises the following components by weight: 60 parts slag; 20 parts fly ash; 15 parts calcium carbide slag; 10 parts limestone; 10 parts steel slag; and 6 parts composite alkali activator, wherein the composite alkali activator is composed of sodium hydroxide and sodium silicate in a mass ratio of 1:1.

[0042] A method for preparing solid waste-based low-carbon cement includes the following steps: mixing industrial solid waste, fly ash, limestone, and composite alkali activator evenly according to the mass ratio to obtain solid waste-based low-carbon cement.

[0043] Test case Solid waste-based low-carbon cement from Examples 1 to 4 and Comparative Examples 1 to 3 were prepared into standard test blocks. After standard curing for 28 days, the compressive strength and flexural strength of the test blocks were tested according to GB / T 17671-1999 standard. The shrinkage rate was tested using the corrugated pipe method according to ASTM C1698 standard, and the appearance of the test blocks was observed for obvious cracks. The cured test blocks were broken and then spliced ​​back together. After standard curing for 28 days, the flexural strength of the self-healing test blocks was tested. The results are shown in Table 1.

[0044] Table 1 Test Results As shown in Table 1, the solid waste-based low-carbon cements of Examples 1 to 4 of the present invention have high compressive strength and flexural strength, low shrinkage rate and high crack resistance, and also have certain self-healing properties. They can self-heal after being broken (the test blocks of Comparative Example 2 and Comparative Example 3 did not self-heal after being broken).

[0045] Compared with Comparative Examples 1 to 3, Embodiment 1 of the present invention adds a functionalized composite to the solid waste-based low-carbon cement component. The polypropylene fiber molecules in the functionalized composite can form a network structure support system through three-dimensional random distribution within the cement component, effectively inhibiting the generation of microcracks. The hydroxyapatite grafted onto the polypropylene fiber molecules can promote more complete hydration reactions, reduce the generation of micropores, and also fill micropores and cracks. The strong bond between hydroxyapatite and polypropylene fiber molecules helps improve the strength of the network structure, enhances the density of the low-carbon cement structure, and improves the mechanical properties of the low-carbon cement. In particular, the polypropylene fiber molecules and hydroxyapatite can synergistically enhance each other, significantly improving the crack resistance of the low-carbon cement. Furthermore, the disulfide bonds grafted onto the polypropylene fiber molecules can, through dynamic exchange reactions, endow the low-carbon cement with certain self-healing properties, enabling the self-healing function of fine cracks.

[0046] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus; although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A solid waste-based low-carbon cement, characterized in that, The composition includes the following components by weight: 50-60 parts slag; 15-20 parts fly ash; 10-15 parts calcium carbide slag; 8-12 parts limestone; 5-10 parts steel slag; 8-10 parts functional composite; and 4-6 parts composite alkali activator. The preparation method of the functional composite is as follows: S1. Immerse polypropylene fibers in xylene, stir evenly, add modifier and benzoyl peroxide, and continue stirring and reacting at 100-110℃ for 3-4 hours to obtain functionalized polypropylene fibers. S2. Immerse the functionalized polypropylene fiber in ethanol, stir until homogeneous, add hydroxyapatite, sonicate, and continue stirring at 50-60℃ for 4-5 hours to obtain the functionalized composite.

2. The solid waste-based low-carbon cement according to claim 1, characterized in that, In step S1, the mass ratio of polypropylene fiber, modifier, and benzoyl peroxide is 1:0.3-0.4:0.01-0.

02.

3. The solid waste-based low-carbon cement according to claim 1, characterized in that, The modifier in step S1 consists of 4-vinylbenzoic acid and methyl allyl disulfide.

4. The solid waste-based low-carbon cement according to claim 3, characterized in that, The mass ratio of 4-vinylbenzoic acid to methyl allyl disulfide is 1:0.8-1.

5. The solid waste-based low-carbon cement according to claim 1, characterized in that, The mass ratio of functionalized polypropylene fiber to hydroxyapatite in step S2 is 1:0.8-1.

6. The solid waste-based low-carbon cement according to claim 1, characterized in that, The ultrasonic power in step S2 is 400-500W, and the ultrasonic time is 0.5-1h.

7. The solid waste-based low-carbon cement according to claim 1, characterized in that, The composite alkaline activator is composed of sodium hydroxide and sodium silicate.

8. The solid waste-based low-carbon cement according to claim 7, characterized in that, The mass ratio of sodium hydroxide to sodium silicate is 1:0.8-1.

9. A method for preparing solid waste-based low-carbon cement as described in any one of claims 1-8, characterized in that, The process includes the following steps: mixing industrial solid waste, fly ash, limestone, functional composite material, and composite alkali activator evenly according to the mass ratio to obtain solid waste-based low-carbon cement.

Images