A solid waste-based low-carbon cement and a preparation method thereof

Abstract

The application belongs to the technical field of low-carbon cement, and particularly relates to a solid waste-based low-carbon cement and a preparation method thereof. The solid waste-based low-carbon cement provided by the application comprises the following components in parts by weight: 50-60 parts of slag; 15-20 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; and 4-6 parts of a composite alkali activator. The solid waste-based low-carbon cement realizes the reuse of solid waste by taking solid waste slag, fly ash and carbide slag as main components, and the low-carbon cement is modified by adding the functional compound, so that the crack resistance and self-repairing performance of the low-carbon cement are improved. The low-carbon cement provided by the application has high compressive strength and flexural strength, low shrinkage and high crack resistance, and also has certain self-repairing performance, and can meet the market demand for functional low-carbon cement.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of low-carbon cement, and particularly relates to a solid waste-based low-carbon cement and a preparation method thereof. BACKGROUND

[0002] Cement, as an important basic building material, has the advantages of convenient raw material acquisition, low price, high construction flexibility, etc. Its annual usage is huge, and the carbon emissions generated are also huge, which has a serious impact on global climate change. In order to reduce the carbon emissions generated by the cement industry, low-carbon cement has become a new green research and development direction. Low-carbon cement is a cement system that significantly reduces carbon dioxide emissions in the production and use process by optimizing raw materials, processes or mineral composition. At the same time, the annual production of solid waste such as slag, fly ash, red mud, etc. is huge, and its sources are widespread, including energy, metallurgy, mining, chemical industry, construction and many other industries. A large amount of solid waste not only occupies land resources, but also seriously pollutes the environment. The recycling of solid waste resources is also imminent. At present, many studies have successfully applied solid waste to low-carbon cement, and at the same time realized the utilization of solid waste resources and the development of low-carbon green cement industry.

[0003] A patent application with the application number CN202311096659.7 discloses a red mud-based low-carbon composite cement and a preparation method thereof. The raw materials of the red mud-based low-carbon composite cement include cementitious components, activator components and admixtures components. The cementitious components include red mud, auxiliary cementitious materials and gypsum-based solid waste. The activator components include alkali activators. The admixtures components include retarders and interfacial enhancers. The preparation method is simple, does not need to remove alkali from the red mud, and does not need high-temperature calcination. It truly realizes the green and environmentally friendly preparation of low-carbon, low-energy and low-cost cement. The prepared low-carbon composite cement has a compressive strength comparable to or even higher than that of 425 cement or 525 cement. A patent application with the application number CN202510412040.5 discloses a method for preparing low-carbon cement based on construction waste. The construction waste is first made into a construction waste slurry. An activator, a hydrothermal auxiliary powder and water are added to the slurry. A high-pressure autoclave is used to perform deep hydrothermal reaction under high temperature and high pressure conditions to obtain a low-carbon cement precursor. The precursor is calcined to obtain clinker. Finally, the clinker is uniformly mixed with mineral admixtures and ground into a fine powder to obtain low-carbon cement. The prepared low-carbon cement has high later compressive strength and flexural strength, and its strength grade is 32.5. Although the above-mentioned patents can use solid waste to prepare low-carbon cement with good compressive strength, the prepared low-carbon cement can only meet the basic building requirements and is not suitable for functional building fields. SUMMARY

[0004] The low-carbon cement provided by the present application has high compressive strength and bending strength, low shrinkage rate and high crack resistance, and also has certain self-repairing performance, and can meet the market demand for functional low-carbon cement.

[0005] The technical scheme adopted by the present application to achieve the above-mentioned purpose is as follows:

[0006] A kind of solid waste-based low-carbon cement, including the following weight parts components: slag 50-60 parts;Fly ash 15-20 parts;Gypsum 8-12 parts;Steel slag 5-10 parts;Functional compound 8-10 parts;Composite alkali activator 4-6 parts.

[0007] Further, the composite alkali activator is composed of sodium hydroxide and sodium silicate.

[0008] Further, the mass ratio of sodium hydroxide and sodium silicate is 1:0.8-1.

[0009] Further, the preparation method of the functional compound is as follows:

[0010] S1, polypropylene fibers are immersed in dimethylbenzene, stirred uniformly, a modifier and benzoyl peroxide are added, and stirring is continued at a temperature of 100-110 DEG C for 3-4 h to obtain functionalized polypropylene fibers.

[0011] S2, the functionalized polypropylene fibers are immersed in ethanol, stirred uniformly, hydroxyapatite is added, and after ultrasonic treatment, stirring is continued at a temperature of 50-60 DEG C for 4-5 h to obtain a functional compound.

[0012] Further, the mass ratio of polypropylene fibers, modifier and benzoyl peroxide in step S1 is 1:0.3-0.4:0.01-0.02.

[0013] Further, the modifier in step S1 is composed of 4-vinylbenzoic acid and methyl allyl disulfide.

[0014] Further, the mass ratio of 4-vinylbenzoic acid and methyl allyl disulfide is 1:0.8-1.

[0015] Further, the mass ratio of functionalized polypropylene fibers and hydroxyapatite in step S2 is 1:0.8-1.

[0016] Further, the ultrasonic power in step S2 is 400-500 W, and the ultrasonic time is 0.5-1 h.

[0017] The application further provides a preparation method of the solid waste-based low-carbon cement.

[0018] The solid waste-based low-carbon cement provided by the application can be applied to the fields of building and road after being mixed with water at a water-binder ratio of 0.5.

[0019] The application has the following beneficial effects:

[0020] 1. The functionalized polypropylene fiber is obtained by grafting 4-vinylbenzoic acid (carboxyl group) and methyl allyl disulfide (disulfide bond) onto the polypropylene fiber through chemical reaction under the action of the catalyst benzoyl peroxide, and the modified functionalized polypropylene fiber is easier to disperse in cement.

[0021] 2. The polypropylene fiber molecules in the functionalized compound can be distributed in the cement component in a three-dimensional random manner to form a reticular structure support system, effectively inhibiting the generation of microcracks, and the hydroxyapatite grafted on the polypropylene fiber molecules can promote the more complete hydration reaction, reduce the generation of micropores, and also play a role in filling micropores and cracks.

[0022] 3. The low-carbon cement provided by the application uses solid waste slag, fly ash and calcium carbide slag as main components, realizes the reuse of solid waste, and adds the functional compound to modify the low-carbon cement, thereby improving the crack resistance and self-repairing performance of the low-carbon cement. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0024] In the present application, the particle sizes of the slag, fly ash, carbide slag, limestone and steel slag are controlled in the range of 8-10 μm, wherein CaO in the slag is not less than 40 wt%, the total amount of SiO2 and Al2O3 in the fly ash is not less than 65 wt%, CaO in the carbide slag is not less than 60 wt%, and CaO in the steel slag is not less than 50 wt%; the limestone has CAS number 1317-65-3; the sodium hydroxide has CAS number 1310-73-2; the sodium silicate has CAS number 1344-09-8; the hydroxyapatite has CAS number 1306-06-5 (particle size within 100 nm); the polypropylene fiber has a diameter of 10-20 μm and a length of 3-5 mm; the benzoyl peroxide has CAS number 94-36-0; the 4-vinylbenzoic acid has CAS number 1075-49-6; the methyl allyl disulfide has CAS number 2179-58-0; the dimethylbenzene has CAS number 1330-20-7; the ethanol has CAS number 64-17-5; and all the chemical reagents are commercially available.

[0025] Embodiment one

[0026] A solid waste-based low-carbon cement, comprising the following components in parts by weight: 60 parts of slag; 20 parts of fly ash; 15 parts of carbide slag; 10 parts of limestone; 10 parts of steel slag; 10 parts of functional composite; and 6 parts of composite alkali activator; wherein the composite alkali activator is composed of sodium hydroxide and sodium silicate in a mass ratio of 1:1.

[0027] The preparation method of the functional composite is as follows:

[0028] S1, polypropylene fibers are immersed in dimethylbenzene, stirred uniformly, a modifier and benzoyl peroxide are added, and stirring is continued at a temperature of 110°C for 3h of reaction; after the reaction is completed, cooling, filtering, and washing and drying of the product are performed to obtain functionalized polypropylene fibers; wherein the mass ratio of the polypropylene fibers, the modifier and the 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.

[0029] S2, the functional polypropylene fiber is immersed into ethanol, stirred uniformly, hydroxyapatite is added, after ultrasonic treatment, at the temperature of 60 DEG C, the stirring reaction is continuously carried out for 4h, after the reaction is completed, cooling, filtration, the product is washed, dried to obtain the functional compound;The mass ratio of functional polypropylene fiber and hydroxyapatite is 1:1;The ultrasonic power is 500W, and the ultrasonic time is 0.5h.

[0030] A preparation method of a solid waste-based low-carbon cement, comprising the following steps: mixing industrial solid waste, fly ash, limestone, functional compound and composite alkali activator uniformly according to mass fraction, to obtain the solid waste-based low-carbon cement.

[0031] Example two

[0032] A solid waste-based low-carbon cement, comprising the following components by weight: 50 parts of slag, 15 parts of fly ash, 10 parts of calcium carbide slag, 12 parts of limestone, 7 parts of steel slag, 8 parts of functional compound and 4 parts of composite alkali activator;The composite alkali activator is composed of sodium hydroxide and sodium silicate with a mass ratio of 1:0.8.

[0033] The preparation method of the functional compound is as follows:

[0034] S1, the polypropylene fiber is immersed into dimethylbenzene, stirred uniformly, modifier and benzoyl peroxide are added, at the temperature of 100 DEG C, the stirring reaction is continuously carried out for 4h, after the reaction is completed, cooling, filtration, the product is washed, dried to obtain the functional polypropylene fiber;The mass ratio of polypropylene fiber, modifier and benzoyl peroxide is 1:0.3:0.01;The modifier is composed of 4-vinylbenzoic acid and methyl allyl disulfide with a mass ratio of 1:0.8;

[0035] S2, the functional polypropylene fiber is immersed into ethanol, stirred uniformly, hydroxyapatite is added, after ultrasonic treatment, at the temperature of 50 DEG C, the stirring reaction is continuously carried out for 4.5h, after the reaction is completed, cooling, filtration, the product is washed, dried to obtain the functional compound;The mass ratio of functional polypropylene fiber and hydroxyapatite is 1:0.8;The ultrasonic power is 400W, and the ultrasonic time is 0.8h.

[0036] A preparation method of a solid waste-based low-carbon cement, comprising the following steps: mixing industrial solid waste, fly ash, limestone, functional compound and composite alkali activator uniformly according to mass fraction, to obtain the solid waste-based low-carbon cement.

[0037] Example three

[0038] A solid waste-based low-carbon cement, comprising the following components by weight: 55 parts of slag; 16 parts of fly ash; 13 parts of carbide slag; 8 parts of limestone; 5 parts of steel slag; 9 parts of functional composite; 5 parts of composite alkali activator; wherein the composite alkali activator is composed of sodium hydroxide and sodium silicate in a mass ratio of 1:0.9.

[0039] The preparation method of the functional composite is as follows:

[0040] S1, polypropylene fibers are immersed in dimethylbenzene, stirred uniformly, a modifier and benzoyl peroxide are added, and stirring is continued at a temperature of 105 DEG C for 3.5 h, after the reaction is completed, cooling, filtering, and the product is washed and dried to obtain functionalized polypropylene fibers; wherein 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;

[0041] S2, the functionalized polypropylene fibers are immersed in ethanol, stirred uniformly, hydroxyapatite is added, and ultrasonic treatment is carried out, and stirring is continued at a temperature of 55 DEG C for 5 h, after the reaction is completed, cooling, filtering, and the product is washed and dried to obtain a functional composite; wherein the mass ratio of functionalized polypropylene fibers and hydroxyapatite is 1:0.9; the ultrasonic power is 450 W, and the ultrasonic time is 1 h.

[0042] A preparation method of a solid waste-based low-carbon cement, comprising the following steps: mixing industrial solid waste, fly ash, limestone, functional composite and composite alkali activator uniformly according to the mass ratio to obtain a solid waste-based low-carbon cement.

[0043] Example four

[0044] A solid waste-based low-carbon cement, comprising the following components by weight: 52 parts of slag; 18 parts of fly ash; 12 parts of carbide slag; 9 parts of limestone; 6 parts of steel slag; 9 parts of functional composite; 6 parts of composite alkali activator; wherein the composite alkali activator is composed of sodium hydroxide and sodium silicate in a mass ratio of 1:1.

[0045] The preparation method of the functional composite is as follows:

[0046] S1, polypropylene fibers are immersed in dimethylbenzene, stirred uniformly, a modifier and benzoyl peroxide are added, and stirring is continued at a temperature of 105 DEG C for 3.5 h, after the reaction is completed, cooling, filtering, and the product is washed and dried to obtain functionalized polypropylene fibers; wherein 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;

[0047] S2, the functional polypropylene fiber is immersed into ethanol, stirred uniformly, hydroxyapatite is added, after ultrasonic treatment, at a temperature of 60℃, the stirring reaction is continued for 5h, after the reaction is completed, cooling, filtration, the product is washed, dried to obtain the functional composite; wherein the mass ratio of the functional polypropylene fiber and the hydroxyapatite is 1:0.8; the ultrasonic power is 480W, and the ultrasonic time is 0.6h.

[0048] A preparation method of a solid waste-based low-carbon cement, comprising the following steps: uniformly mixing industrial solid waste, fly ash, limestone, functional composite and composite alkali activator according to mass fraction, to obtain the solid waste-based low-carbon cement.

[0049] Comparative example one

[0050] Compared with example one, the components of the solid waste-based low-carbon cement are different, and the functional polypropylene fiber is added.

[0051] A solid waste-based low-carbon cement, comprising the following components by weight: 60 parts of slag; 20 parts of fly ash; 15 parts of carbide slag; 10 parts of limestone; 10 parts of steel slag; 10 parts of polypropylene fiber; and 6 parts of composite alkali activator; wherein the composite alkali activator is composed of sodium hydroxide and sodium silicate with a mass ratio of 1:1.

[0052] The preparation method of the functional polypropylene fiber is the same as step S1 in example one.

[0053] A preparation method of a solid waste-based low-carbon cement is the same as example one.

[0054] Comparative example two

[0055] Compared with example one, the components of the solid waste-based low-carbon cement are different, and the polypropylene fiber is added.

[0056] A solid waste-based low-carbon cement, comprising the following components by weight: 60 parts of slag; 20 parts of fly ash; 15 parts of carbide slag; 10 parts of limestone; 10 parts of steel slag; 10 parts of polypropylene fiber; and 6 parts of composite alkali activator; wherein the composite alkali activator is composed of sodium hydroxide and sodium silicate with a mass ratio of 1:1.

[0057] A preparation method of a solid waste-based low-carbon cement is the same as example one.

[0058] Comparative example three

[0059] Compared with example one, the components of the solid waste-based low-carbon cement are different.

[0060] A solid waste-based low-carbon cement, comprising the following components in parts by weight: 60 parts of slag; 20 parts of fly ash; 15 parts of carbide slag; 10 parts of limestone; 10 parts of steel slag; 6 parts of composite alkali activator; wherein the composite alkali activator is composed of sodium hydroxide and sodium silicate in a mass ratio of 1:1.

[0061] A preparation method of a solid waste-based low-carbon cement, comprising the following steps: uniformly mixing industrial solid waste, fly ash, limestone and composite alkali activator according to the mass ratio to obtain the solid waste-based low-carbon cement.

[0062] Test example

[0063] The solid waste-based low-carbon cement of examples one to four and comparative examples one to three is made into standard test blocks, and the standard curing is carried out for 28 days; the compressive strength and the flexural strength of the test blocks are tested according to the standard GB / T 17671-1999; the shrinkage is tested according to the standard ASTM C1698 by using the bellows method to test the autogenous shrinkage value, and the appearance of the test blocks is observed to see whether there is obvious crack; the cured test blocks are broken and then spliced, and the standard curing is carried out for 28 days to test the flexural strength of the test blocks after self-repairing, and the results are shown in Table 1.

[0064] Table 1 test results

[0065]

[0066] It can be known from the results in Table 1 that the solid waste-based low-carbon cement of examples one to four has high compressive strength and flexural strength, low shrinkage and high crack resistance, and also has certain self-repairing performance, and can be self-repaired after being broken (the test blocks of comparative examples two and three are not self-repaired after being broken).

[0067] It can be known from the comparison between example one and comparative examples one to three that the functional compound is added in the component of the solid waste-based low-carbon cement of example one, the polypropylene fiber molecules in the functional compound can be distributed in the cement component in a three-dimensional random manner to form a network structure support system, effectively inhibiting the generation of microcracks, the hydroxyapatite grafted on the polypropylene fiber molecules can promote the more sufficient hydration reaction and reduce the generation of micropores, and also can play the role of filling micropores and cracks, the combination between the hydroxyapatite and the polypropylene fiber molecules is firm, which helps to improve the strength of the network structure and enhance the compactness of the low-carbon cement structure, improve the mechanical properties of the low-carbon cement, and especially the polypropylene fiber molecules and the hydroxyapatite can synergistically enhance the crack resistance of the low-carbon cement; in addition, the disulfide bond grafted on the polypropylene fiber molecules can impart certain self-repairing performance to the low-carbon cement through dynamic exchange reaction, and can realize the self-repairing function of fine cracks.

[0068] It is to be understood that, in this text, such as the term "comprise", "comprising" or any other variant thereof is intended to cover the non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus; although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements, and changes can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A solid waste based low-carbon cement, characterized by, The method comprises the following components by weight: slag 50-60 parts; fly ash 15-20 parts; carbide slag 10-15 parts; limestone 8-12 parts; steel slag 5-10 parts; functional composite 8-10 parts; composite alkali activator 4-6 parts; the preparation method of the functional composite is: S1, polypropylene fibers are immersed in xylene, stirred uniformly, a modifier and benzoyl peroxide are added, and stirring is continued at a temperature of 100-110 DEG C for 3-4 h to obtain functionalized polypropylene fibers; S2, the functionalized polypropylene fibers are immersed in ethanol, stirred uniformly, hydroxyapatite is added, and ultrasonic treatment is performed, and stirring is continued at a temperature of 50-60 DEG C for 4-5 h to obtain a functional composite; The modifier in step S1 is composed of 4-vinylbenzoic acid and methyl allyl disulfide; the mass ratio of the 4-vinylbenzoic acid and methyl allyl disulfide is 1:0.8-1.

2. The solid waste based low-carbon cement as claimed in claim 1, wherein, The mass ratio of the polypropylene fibers, the modifier, and the benzoyl peroxide in step S1 is 1:0.3-0.4:0.01-0.

02.

3. The solid waste based low-carbon cement as claimed in claim 1, wherein, The mass ratio of the functionalized polypropylene fibers and the hydroxyapatite in step S2 is 1:0.8-1.

4. The solid waste based low-carbon cement as claimed in claim 1, wherein, The ultrasonic power in step S2 is 400-500 W, and the ultrasonic time is 0.5-1 h.

5. The solid waste based low-carbon cement as claimed in claim 1, wherein, The composite alkali activator is composed of sodium hydroxide and sodium silicate.

6. The solid waste based low-carbon cement as claimed in claim 5, wherein, The mass ratio of the sodium hydroxide and the sodium silicate is 1:0.8-1.

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