Negative carbon cementing material based on multi-solid-waste synergy and preparation method of negative carbon cementing material

Abstract

The invention belongs to the technical field of building materials, and particularly relates to a negative carbon cementing material based on multi-solid-waste synergy and a preparation method thereof.The negative carbon cementing material is prepared from, by mass, 30-50% of ardealite, 10-20% of rice hull ash, 10-25% of steel slag micro powder, 3-8% of reed fiber, 10-18% of salt lake brine and 5-10% of red mud; a material system which is composed of six specific components including ardealite, rice hull ash, steel slag micro powder, reed fibers, salt lake brine and red mud and achieves high performance and negative carbon benefits through the synergistic effect is called as a six-element system, through the synergistic effect, large-scale consumption of the solid waste utilization rate is achieved, meanwhile, the material has excellent mechanical performance and good durability, and the service life of the material is prolonged. And carbon loading is realized in the whole life cycle.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically referring to a negative carbon cementitious material based on the synergistic effect of multiple solid wastes and its preparation method. Background Technology

[0002] Traditional cement-based materials are one of the world's major sources of carbon emissions, accounting for 8-10% of global carbon emissions, which seriously restricts the carbon neutrality process in the construction sector. At the same time, the steel, phosphate chemical, alumina and agricultural sectors produce huge quantities of solid waste such as phosphogypsum, steel slag, red mud and rice husk ash every year, with phosphogypsum alone exceeding 80 million tons per year.

[0003] Currently, the comprehensive utilization rate of phosphogypsum in my country is only 40%, and the utilization rate of steel slag is about 30%. The long-term storage of large amounts of solid waste not only occupies valuable land resources, but also poses serious environmental risks. For example, the leaching of radioactive elements and soluble phosphorus in phosphogypsum will pollute the soil and groundwater.

[0004] Gypsum-based building materials have attracted attention due to their lightweight, fire-resistant, and environmentally friendly properties. Existing technologies include research on modifying gypsum using single or a few types of solid waste, but these generally suffer from inherent defects such as low strength (typically <20MPa), poor toughness, and poor water resistance, and cannot simultaneously achieve optimal mechanical properties, functionality, and economy. Furthermore, the synergistic utilization of multiple solid wastes faces technical bottlenecks such as large fluctuations in composition, poor compatibility, and unstable performance.

[0005] Furthermore, existing technologies related to prefabricated building components based on solid waste only protect specific component structures and do not address the negative carbon properties of the materials themselves or their general application in various building components. How to achieve large-scale, high-value resource utilization of bulk solid waste, while simultaneously developing cementitious materials with high performance, high durability, and significant negative carbon benefits, is a pressing global challenge that needs to be addressed. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a carbon-negative cementitious material based on the synergistic effect of multiple solid wastes and its preparation method. The material system, composed of six specific components—phosphogypsum, rice husk ash, steel slag powder, reed fiber, salt lake brine, and red mud—achieves high performance and carbon-negative benefits through synergistic effects and is referred to as the "six-element system." Through synergistic effects, it enables large-scale utilization and disposal of solid waste, while possessing excellent mechanical properties, good durability, and carbon-negative effects throughout its entire life cycle.

[0007] To achieve the above functions, the technical solution adopted by the present invention is as follows: a negative carbon cementitious material based on the synergy of multiple solid wastes, comprising the following raw materials by mass percentage: 30-50% phosphogypsum, 10-20% rice husk ash, 10-25% steel slag powder, 3-8% reed fiber, 10-18% salt lake brine, and 5-10% red mud.

[0008] Preferably, the rice husk ash is a highly active rice husk ash with an amorphous SiO2 content of ≥85% and a specific surface area of ​​≥15000m² / kg.

[0009] Preferably, the steel slag powder is stabilized steel slag powder that has undergone carbonization and solidification treatment, wherein the f-CaO content is ≤1.5% and the specific surface area is ≥400m² / kg.

[0010] Preferably, the reed fiber has a length of 5-15 mm, an aspect ratio of ≥50, a tensile strength of ≥150 MPa, and the reed fiber has not been treated with alkaline brine from the salt lake.

[0011] Preferably, the concentration of Mg²⁺ ions in the salt lake brine is 40-80 g / L, and the concentration of Li⁺ ions is 2-5 g / L, and it can be used directly without pretreatment.

[0012] A method for preparing a negative carbon cementitious material based on the synergistic effect of multiple solid wastes includes the following steps: (1) Prepare phosphogypsum, rice husk ash, steel slag powder, reed fiber, salt lake brine and red mud according to the required proportions and quality. (2) Put phosphogypsum, rice husk ash, steel slag powder and red mud into a mixer for the first stage of dry mixing, and mix for 3-5 minutes until uniform. (3) Add salt lake brine to the dry mixture from step (2) and perform a second wet mixing for 2-4 minutes; (4) Add reed fiber to the slurry in step (3) and carry out third-level fiber dispersion and mixing for 1-2 minutes to obtain the negative carbon cementitious material.

[0013] Preferably, the phosphogypsum in step (1) is a purified low-radioactivity phosphogypsum with an internal radiation index ≤0.3.

[0014] Preferably, the preparation method of the negative carbon cementitious material further includes a curing step: curing at a temperature of 50-80℃ and a relative humidity of ≥90% for 6-24 hours to enhance the carbonization reaction and negative carbon performance.

[0015] Preferably, the negative carbon cementitious material can be used to prepare any one of building panels, blocks, precast beams, precast columns or pipe components.

[0016] Compared with the prior art, the present invention achieves the following beneficial effects by adopting the above solution: The "six-element system," achieved through the synergistic effect of six components, has achieved breakthroughs in three dimensions: performance, environment, and economy. Phosphogypsum provides calcium and early strength, rice husk ash provides active silicon and later strength, steel slag and red mud provide alkalinity and micro-aggregate effect, reed fiber toughens and resists cracking, and Li⁺ and Mg²⁺ ions in the salt lake brine promote coagulation and mineralization, significantly improving compressive strength. The "six-element system" itself sequesters CO2 and replaces cement on a large scale, achieving significant negative carbon benefits. Compared with traditional cement, carbon emissions have turned from positive to negative, and carbon emissions have been greatly reduced. The raw materials are solid waste, with extremely low cost, large-scale solid waste disposal, safety and environmental protection. It can be produced using existing building material production lines without special equipment, enabling large-scale mass production. Attached Figure Description

[0017] Figure 1 This is a schematic diagram comparing the carbon emissions of Embodiment 1 of the present invention with those of ordinary cement; Figure 2 This is a comparison chart of the compressive strength development curves of Example 1 of the present invention and ordinary cement. Detailed Implementation

[0018] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] This invention discloses a negative carbon cementitious material based on the synergistic effect of multiple solid wastes, comprising the following raw materials by mass percentage: 30-50% phosphogypsum, 10-20% rice husk ash, 10-25% steel slag powder, 3-8% reed fiber, 10-18% salt lake brine, and 5-10% red mud; the rice husk ash is amorphous SiO2 content ≥85% and specific surface area ≥15000m² / kg with high activity; the steel slag powder is stabilized steel slag powder that has undergone carbonization and solidification treatment, wherein the f-CaO content is ≤1.5% and the specific surface area is ≥400m² / kg; the reed fiber has a length of 5-15mm, an aspect ratio ≥50, and a tensile strength ≥150MPa, and the reed fiber has not undergone alkali treatment with salt lake brine; the Mg²⁺ ion concentration in the salt lake brine is 40-80g / L and the Li⁺ ion concentration is 2-5g / L, and it can be used directly without pretreatment.

[0020] A method for preparing a negative carbon cementitious material based on the synergistic effect of multiple solid wastes includes the following steps: (1) Prepare phosphogypsum, rice husk ash, steel slag powder, reed fiber, salt lake brine and red mud according to the required proportions and quality. (2) Put phosphogypsum, rice husk ash, steel slag powder and red mud into a mixer for the first stage of dry mixing, and mix for 3-5 minutes until uniform. (3) Add salt lake brine to the dry mixture from step (2) and perform a second wet mixing for 2-4 minutes; (4) Add reed fiber to the slurry in step (3) and carry out third-level fiber dispersion and mixing for 1-2 minutes to obtain the negative carbon cementitious material. Example 1:

[0021] Raw materials consisting of 42% phosphogypsum, 15% rice husk ash, 18% steel slag powder, 6% reed fiber, 15% salt lake brine, and 6% red mud were selected and dry-mixed for 4 minutes, wet-mixed for 3 minutes, and fiber dispersion-mixed for 1.5 minutes.

[0022] Performance test results: 28-day compressive strength: 85 MPa; Initial setting time: 9 min; Internal radiation index: IRa = 0.12; Carbon sequestration: -108 kg CO2eq / t; Thermal conductivity: 0.32 W / (m·K); Fire resistance rating: Class A; Shrinkage rate: 0.04%; Water absorption rate: 6.5%. Example 2:

[0023] Raw materials consisting of 30% phosphogypsum, 20% rice husk ash, 25% steel slag powder, 3% reed fiber, 12% salt lake brine, and 10% red mud were selected and dry-mixed for 4 minutes, wet-mixed for 3 minutes, and fiber-dispersed for 1.5 minutes.

[0024] Performance test results: 28-day compressive strength: 58 MPa; Initial setting time: 11 min; Carbon sequestration: -75 kg CO2eq / t; The other performance test results are consistent with those of Example 1. Example 3:

[0025] Raw materials consisting of 50% phosphogypsum, 10% rice husk ash, 10% steel slag powder, 8% reed fiber, 12% salt lake brine, and 10% red mud were selected and dry-mixed for 4 minutes, wet-mixed for 3 minutes, and fiber-dispersed for 1.5 minutes.

[0026] Performance test results: 28-day compressive strength: 62 MPa; Initial setting time: 8 min; Carbon sequestration: -82 kg CO2eq / t; The other performance test results are consistent with those of Example 1. Example 4:

[0027] Raw materials consisting of 45% phosphogypsum, 18% rice husk ash, 15% steel slag powder, 5% reed fiber, 12% salt lake brine, and 5% red mud were selected and dry-mixed for 4 minutes, wet-mixed for 3 minutes, and fiber-dispersed and mixed for 1.5 minutes.

[0028] Performance test results: 28-day compressive strength: 92 MPa; 180-day compressive strength: 105 MPa; Initial setting time: 8 min; Carbon sequestration: -115 kg CO2eq / t; Strength loss rate after 50 wet-dry cycles: <5%; The other performance test results are consistent with those of Example 1. Example 5:

[0029] Raw materials consisting of 42% phosphogypsum, 15% rice husk ash, 18% steel slag powder, 6% reed fiber, 15% salt lake brine, and 6% red mud were selected and dry-mixed for 4 minutes, wet-mixed for 3 minutes, and fiber dispersion-mixed for 1.5 minutes.

[0030] Detailed LCA analysis (lifecycle assessment from raw material acquisition to product delivery): Carbon emissions from raw material transportation: 50 kg CO2eq / t; Carbon emissions during production: 20 kg CO2eq / t; Carbon sequestration contribution: -178 kg CO2eq / t; Net carbon emissions: -108 kg CO2eq / t. Example 6:

[0031] Raw materials consisting of 42% phosphogypsum, 15% rice husk ash, 18% steel slag powder, 6% reed fiber, 15% salt lake brine, and 6% red mud were selected and dry-mixed for 4 minutes, wet-mixed for 3 minutes, and fiber dispersion-mixed for 1.5 minutes.

[0032] Durability test results: Freeze-thaw resistance: After 100 freeze-thaw cycles, the strength loss rate is <8%; Resistance to sulfate attack: After immersion in 5% Na2SO4 solution for 180 days, the strength loss rate is <10%; Carbonization depth: After carbonization for 28 days at 20℃ and 70%RH, the carbonization depth is <3mm.

[0033] A 200mm thick wall panel was prepared using the material from Example 1. Test results: Sound insulation: 45dB; Thermal resistance: 0.35 m²·K / W; Hanging force: ≥800N.

[0034] Pipe components were prepared using the material from Example 1, and the test results were as follows: Internal pressure strength: ≥1.6MPa; Corrosion resistance: After immersion in an acidic solution with pH=4 for 30 days, the mass loss is <0.5%.

[0035] Comparative Example 1 Test blocks were prepared using ordinary silicate cement.

[0036] Performance test results: 28-day compressive strength: 45 MPa; LCA calculated carbon emissions: +850 kg CO2 equivalent / ton of material.

[0037] Comparative Example 2 The red mud component is missing; otherwise, it is the same as in Example 1.

[0038] Performance test results: 28-day compressive strength: 62 MPa; Internal radiation index: IRa = 0.35; The radioactive adsorption capacity decreased significantly.

[0039] Comparative Example 3 Since salt lake brine was unavailable, water was used as a substitute; otherwise, the process was the same as in Example 1.

[0040] Performance test results: The initial setting time was extended to 25 minutes, and the early strength development was slow.

[0041] Microstructure analysis: SEM observation showed that the "six-element system" of this invention forms a dense network structure. The reaction between phosphogypsum and rice husk ash generates a large amount of CSH gel. The reed fiber is tightly bound to the matrix, and calcium carbonate mineral deposits are visible on the surface. Energy dispersive spectroscopy analysis confirmed that the red mud has a significant adsorption and fixation effect on Ra²⁺, B³⁺ and other substances in the brine.

[0042] The present invention and its embodiments have been described above. This description is not restrictive, and the embodiments shown are only one of the embodiments of the present invention, and are not actually limited thereto. In short, if those skilled in the art are inspired by this description and design similar embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A negative carbon cementitious material based on multi-solid waste synergy, characterized in that, The raw materials include the following by weight percentage: 30-50% phosphogypsum, 10-20% rice husk ash, 10-25% steel slag powder, 3-8% reed fiber, 10-18% salt lake brine, and 5-10% red mud.

2. The negative carbon cementitious material based on multi-solid waste synergy according to claim 1, characterized in that, The rice husk ash is a highly active rice husk ash with an amorphous SiO2 content of ≥85% and a specific surface area of ​​≥15000m² / kg.

3. The negative carbon cementitious material based on multi-solid waste synergy according to claim 1, characterized in that, The steel slag powder is stabilized steel slag powder that has undergone carbonization and solidification treatment, wherein the f-CaO content is ≤1.5% and the specific surface area is ≥400m² / kg.

4. The negative carbon cementitious material based on multi-solid waste synergy according to claim 1, characterized in that, The reed fiber has a length of 5-15mm, an aspect ratio of ≥50, a tensile strength of ≥150MPa, and has not been treated with alkaline salt lake brine.

5. The negative carbon cementitious material based on multi-solid waste synergy according to claim 1, characterized in that, The concentration of Mg²⁺ ions in the salt lake brine is 40-80 g / L, and the concentration of Li⁺ ions is 2-5 g / L.

6. The method for preparing negative carbon cementitious materials based on multi-solid waste synergy according to claims 1-5, characterized in that, Includes the following steps: (1) Prepare phosphogypsum, rice husk ash, steel slag powder, reed fiber, salt lake brine and red mud according to the required proportions and quality. (2) Put phosphogypsum, rice husk ash, steel slag powder and red mud into a mixer for the first stage of dry mixing, and mix for 3-5 minutes until uniform. (3) Add salt lake brine to the dry mixture from step (2) and perform a second wet mixing for 2-4 minutes; (4) Add reed fiber to the slurry in step (3) and carry out third-level fiber dispersion and mixing for 1-2 minutes to obtain the negative carbon cementitious material.

7. The method for preparing negative carbon cementitious material based on multi-solid waste synergy according to claim 6, characterized in that, The phosphogypsum in step (1) is a purified low-radioactivity phosphogypsum with an internal radiation index ≤0.

3.

8. The method for preparing negative carbon cementitious material based on multi-solid waste synergy according to claim 6, characterized in that, The preparation method of the negative carbon cementitious material also includes a curing step: curing for 6-24 hours at a temperature of 50-80℃ and a relative humidity of ≥90%.

9. The negative carbon cementitious material based on multi-solid waste synergy according to claims 1-5 can be used to prepare any one of building panels, blocks, precast beams, precast columns or pipe components.

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