Solid-waste-based lightweight fine-grained ceramsite as well as preparation method and application thereof

Abstract

The invention is applicable to the technical field of solid waste resource utilization and novel building material preparation, and provides solid waste based lightweight fine-grained ceramsite as well as a preparation method and application thereof, and the ceramsite is prepared from titanium gypsum, iron tailing powder, a solid waste based cementing material, a chelating agent, a nanocrystalline nucleus early strength agent and mixing water according to a specific proportion. The preparation method comprises the following steps: dry mixing of raw materials, preparation of an additive solution, wet mixing, rolling granulation, normal-temperature curing, 60-95 DEG C low-temperature steam curing and drying. According to the invention, the titanium gypsum, the iron tailing powder and other low-value solid wastes are used as main raw materials, and the lightweight fine-grained ceramsite with small particle size, stable structure, low water absorption and low dry density is successfully prepared through an optimized ratio and a unique low-temperature steam curing process. The product can be used as a fine aggregate to be applied to plastering mortar, completely or partially replaces natural gravel, and the mechanical property and construction stability of the mortar are improved while the mortar capacity is reduced.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization and new building material preparation technology, and more specifically, it relates to a solid waste-based lightweight fine-grained ceramsite, its preparation method and application. Background Technology

[0002] As the construction industry moves towards green and low-carbon development, the resource utilization of solid waste has become an important research topic in the field of building materials. Currently, bulk solid wastes such as slag and fly ash have been used on a large scale as cement admixtures, while industrial solid wastes such as titanium gypsum and iron tailings powder, which have large outputs but low utilization rates, still face significant challenges in resource utilization.

[0003] Specifically, titanium gypsum has a high water content, many impurities, and high viscosity; iron tailings powder has a large specific surface area and strong surface adsorption. If both are used directly as concrete admixtures, they will rapidly absorb mixing water, leading to a sharp decrease in fluidity and deterioration in workability. Furthermore, due to the large fluctuations in their composition and activity, the stability of the material's properties will be further affected.

[0004] Preparing ceramsite from solid waste through high-temperature sintering is another resource utilization pathway. However, traditional ceramsite production processes are energy-intensive, generate large carbon emissions, and are prone to producing polluting gases. The resulting products are mostly medium to coarse-sized particles with open pore structures and rapid water absorption, making them suitable for structural load-bearing or lightweight concrete, but difficult to meet the stringent requirements of aggregate fineness, uniformity, and low water absorption for thin-layer construction materials such as plastering mortar.

[0005] At the same time, the fine aggregates currently widely used in plastering mortar—natural sand and stone powder—consume natural resources and damage the environment during extraction. Moreover, the materials have limited functionality and cannot provide added value in terms of lightweighting, volume stability, and construction performance control.

[0006] Therefore, a lightweight fine-grained ceramsite based on solid waste, its preparation method, and its application are proposed to improve the existing problems. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a lightweight fine-grained ceramsite based on solid waste, its preparation method, and its application. This invention can achieve efficient disposal of low-value solid wastes such as titanium gypsum and iron tailings powder, and can also produce lightweight aggregates with small particle size, stable structure, and controllable water absorption through energy-saving processes. These aggregates can replace natural sand and gravel in plastering mortar, thereby improving the overall performance of materials and promoting the green and low-carbon transformation of the building materials industry.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a solid waste-based lightweight fine-grained ceramsite, comprising the following components by mass percentage: 10%–60% titanium gypsum; 10%–50% iron tailings powder; 5%–20% solid waste-based cementitious material; 0.02%–0.1% chelating agent; 0.1%–1.0% nanocrystalline nucleation early strength agent; and 15%–30% mixing water; wherein the titanium gypsum has a particle size of less than 2.36 mm and a moisture content of no more than 30%.

[0009] The present invention is further configured such that: the titanium gypsum is an industrial gypsum produced by neutralizing a large amount of acidic wastewater during the production of titanium dioxide using the sulfuric acid process, and its main chemical component is calcium sulfate dihydrate.

[0010] The present invention is further configured such that: the solid waste-based cementitious material is a ternary solid waste system obtained by mechanochemical and lattice activation treatment, and the ternary solid waste system is composed of the following raw materials by mass percentage: 40% steel slag powder; 45% slag powder; and 15% desulfurized gypsum powder.

[0011] The present invention is further configured such that the chelating agent is selected from one or more of disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, tetrasodium glutamate diacetate, or sodium gluconate.

[0012] The present invention is further configured such that the nanocrystalline nucleus early strength agent serves as a nucleation center for the hydration reaction, thereby promoting the early nucleation and growth of hydration products.

[0013] The above-mentioned method for preparing ceramsite includes the following steps:

[0014] (1) Dry mixing: Titanium gypsum, iron tailings powder and solid waste-based cementitious materials are mixed thoroughly in proportion to obtain a uniform dry mixture;

[0015] (2) Solution preparation: Dissolve the chelating agent and the nanocrystal nucleus early strength agent in the mixing water after deducting the water content of the raw materials to form a uniform additive solution;

[0016] (3) Wet mixing: Mix the dry mixture obtained in step (1) with the additive solution obtained in step (2) and stir evenly to obtain a wet material with good plasticity;

[0017] (4) Granulation: The wetted material obtained in step (3) is fed into an inclined granulation device for rolling granulation to obtain a wet spherical green body;

[0018] (5) Curing at room temperature: The wet spherical blank is cured at room temperature to obtain initial strength;

[0019] (6) Steam curing: The green body treated in step (5) is steam cured at 60-95℃ for 3-12 hours;

[0020] (7) Drying: The green body after step (6) is dried to remove residual moisture and obtain solid waste-based lightweight fine ceramsite finished product.

[0021] The above-mentioned expanded clay aggregates can be used to prepare plastering mortar as a functional fine aggregate, which can completely or partially replace the natural sand or stone powder in it.

[0022] In summary, this application includes at least one of the following beneficial technical effects:

[0023] (1) By co-utilizing titanium gypsum and iron tailings powder, the resource transformation of the two types of low-value-added solid wastes can be realized, effectively improving their comprehensive utilization level and reducing the pressure on the environment caused by solid waste stockpiling.

[0024] (2) By synergistically controlling the raw material composition and granulation process, the resulting ceramsite has a relatively concentrated particle size distribution, and the proportion of fine particles is significantly increased, with ceramsite smaller than 2.36mm accounting for more than 80%. It is suitable for applications such as plastering mortar that have high requirements for fine aggregates, and overcomes the problems of traditional ceramsite having large particle size and unreasonable gradation.

[0025] (3) By regulating the raw material system and pore structure, the pore distribution inside the ceramsite is made more uniform and the proportion of interconnected pores is effectively controlled, thereby reducing the water absorption rate and slowing down the water adsorption process, which is conducive to improving the construction stability and usage consistency of the mixture.

[0026] (4) The prepared ceramsite meets the requirements for lightweighting, with a dry density of less than 800 kg / m³. 3 It has lower density than inert fillers such as natural sand and stone powder, and has better structural stability and applicability. It can meet the requirements of plastering mortar and other materials for fine aggregates, and is suitable for large-scale preparation and engineering applications. Detailed Implementation

[0027] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0028] This invention provides the following technical solutions:

[0029] Example 1:

[0030] Mix 30% titanium gypsum, 50% iron tailings powder, and 20% solid waste-based cementitious material evenly according to weight percentage to prepare a mixed dry material. Dissolve 0.02% disodium ethylenediaminetetraacetate and 0.2% nanocrystalline nucleation early strength agent in 25% water to prepare a solution. Mix the mixture with the solution and stir for 5 minutes to form a uniformly wetted powder. Then pour it into an inclined granulator and granulate for 10 minutes to obtain solid waste-based lightweight fine ceramsite green bodies. After the green bodies are left to stand at room temperature for 12 hours, they are transferred to a high-temperature steam curing environment at 80℃ for 8 hours, and then dried to constant weight to obtain solid waste-based lightweight ceramsite.

[0031] Example 2:

[0032] Mix 50% titanium gypsum, 30% iron tailings powder, and 20% solid waste-based cementitious material evenly according to weight percentage to prepare a mixed dry material. Dissolve 0.05% disodium ethylenediaminetetraacetate and 0.5% nanocrystalline nucleation early strength agent in 20% water to prepare a solution. Mix the mixture with the solution and stir for 5 minutes to form a uniformly wetted powder. Then pour it into an inclined granulator and granulate for 10 minutes to obtain solid waste-based lightweight fine ceramsite green bodies. After the green bodies are left to stand at room temperature for 12 hours, they are transferred to a high-temperature steam curing environment at 80℃ for 8 hours, and then dried to constant weight to obtain solid waste-based lightweight ceramsite.

[0033] Example 3:

[0034] Mix 50% titanium gypsum, 30% iron tailings powder, and 20% solid waste-based cementitious material evenly according to weight percentage to prepare a mixed dry material. Dissolve 0.05% disodium ethylenediaminetetraacetate and 0.5% nanocrystalline nucleation early strength agent in 20% water to prepare a solution. Mix the mixture with the solution and stir for 5 minutes to form a uniformly wetted powder. Then pour it into an inclined granulator and granulate for 10 minutes to obtain solid waste-based lightweight fine ceramsite green bodies. After the green bodies are left to stand at room temperature for 12 hours, they are transferred to a high-temperature steam curing environment at 80℃ for 12 hours, and then dried to constant weight to obtain solid waste-based lightweight ceramsite.

[0035] Comparative Example 1:

[0036] The difference from Example 1 is that the obtained ceramsite green body is transferred to a high temperature steam curing environment of 150°C for 8 hours, and then dried to constant weight to obtain solid waste-based lightweight ceramsite.

[0037] Comparative Example 2:

[0038] The difference from Example 1 is that: the dry mixture consists of 80% iron tailings powder and 20% solid waste-based cementitious material mixed evenly by weight percentage. A solution is prepared by dissolving 0.02% disodium ethylenediaminetetraacetate and 0.2% nanocrystalline nucleation early strength agent in 35% water.

[0039] Comparative Example 3:

[0040] The difference from Example 1 is that no chelating agent or nanocrystal nucleus early strength agent is added.

[0041] Therefore, the compressive strength, bulk density, and sieve analysis of the ceramsite in the above embodiments and comparative examples were conducted, and the results are shown in the table below:

[0042] project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Cylinder compressive strength MPa 5.1 5.7 6.5 3.2 5.5 4.1 <![CDATA[Bulk density kg / m 3 > 780 790 785 786 813 809 Water absorption rate / % 15.1 14.7 13.9 23 20 17 Percentage of particles smaller than 4.75mm 93% 95% 94% 91% 56% 85% Percentage of particles smaller than 2.36mm 85% 87% 88% 84% 42% 75% Percentage of particles smaller than 1.18mm 72% 74% 73% 69% 25% 57% Percentage of particles smaller than 0.6mm 57% 63% 61% 55% 10% 43%

[0043] As can be seen from the table above, the ceramsite prepared in Examples 1-3 is lightweight, has low water absorption, high strength, and more than 80% of the ceramsite is fine ceramsite smaller than 2.36 mm.

[0044] Comparative Example 1 shows that excessively high temperature curing is actually detrimental to the strength development of ceramsite, mainly because hydrated products such as ettringite are easily decomposed at high temperatures.

[0045] Comparative Example 2 shows that excessive iron tailings powder content will lead to a decrease in the fine particle output during the granulation process, because excessive iron tailings have a high water absorption rate and are prone to sticking to the wall during the granulation process.

[0046] Comparative Example 3 shows that chelating agents and nanocrystal nuclei early strength agents help optimize the granulation process and enhance the strength of ceramic particles.

[0047] Prepare a gypsum plastering mortar base group according to the mass ratio in the table below, and use the expanded clay aggregate prepared in Example 2, preferably with particles smaller than 0.6 mm, to completely replace the inert filler stone powder in the traditional plastering gypsum mortar according to the bulk density, while reducing the water consumption by 10%, to prepare the expanded clay aggregate gypsum plastering mortar.

[0048] plaster stone powder perlite Cellulose ethers Retarder Entraining agent water 900 400 80 3 1.0 1.8 660

[0049] The test-prepared gypsum plaster mortar reference group had an initial setting time of 70 minutes, a final setting time of 90 minutes, and a dry density of 890 kg / m³. 3 The flexural strength is 2.6 MPa, the compressive strength is 6.8 MPa, and the tensile bond strength is 0.51 MPa. When the expanded clay aggregate prepared in this invention partially replaces the stone powder, the initial setting time of the resulting plastering mortar is 75 min, the final setting time is 95 min, and the dry density decreases to 860 kg / m³. 3 The flexural strength is increased to 3.4 MPa, the compressive strength is increased to 7.9 MPa, and the tensile bond strength is increased to 0.55 MPa.

[0050] The results show that using the expanded clay aggregate of this invention as a fine aggregate can significantly reduce the overall density of the mortar system and effectively improve its mechanical properties while maintaining good workability. This effect is mainly attributed to the relatively regular spherical morphology of the expanded clay aggregate surface and the ball-bearing lubrication effect generated during mixing, which makes the slurry distribution more uniform and is conducive to structural densification and improved interfacial bonding performance. Compared with traditional stone powder, the expanded clay aggregate prepared by this invention can meet the performance requirements of plastering mortar while taking into account both lightweight and optimized mechanical properties. In addition, the expanded clay aggregate uses industrial solid waste as the main raw material, which has the advantages of wide availability and low cost, helping to reduce the overall material cost and improve the level of comprehensive resource utilization.

[0051] Obviously, the embodiments described above are merely some, not all, embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

Claims

1. A type of lightweight fine-grained ceramsite based on solid waste, characterized in that: Includes the following components by mass percentage: Titanium gypsum 10%–60%; iron tailings powder 10%–50%; solid waste-based cementitious material 5%–20%; chelating agent 0.02%–0.1%; nanocrystalline nucleation early strength agent 0.1%–1.0%; mixing water 15%–30%; The titanium gypsum has a particle size of less than 2.36 mm and a moisture content of no more than 30%.

2. The solid waste-based lightweight fine-grained ceramsite according to claim 1, characterized in that: The titanium gypsum mentioned is an industrial gypsum produced as a byproduct of titanium dioxide production via the sulfuric acid process, and its main chemical component is calcium sulfate dihydrate.

3. The solid waste-based lightweight fine-grained ceramsite according to claim 1, characterized in that: The solid waste-based cementitious material is a ternary solid waste system obtained through mechanochemical and lattice activation treatment. The ternary solid waste system is composed of the following raw materials by mass percentage: 40% steel slag powder; 45% slag powder; and 15% desulfurized gypsum powder.

4. The solid waste-based lightweight fine-grained ceramsite according to claim 1, characterized in that: The chelating agent is selected from one or more of disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, tetrasodium glutamate diacetate, or sodium gluconate.

5. The solid waste-based lightweight fine-grained ceramsite according to claim 1, characterized in that: The nanocrystalline nucleus early strength agent serves as a nucleation center for the hydration reaction, promoting the early nucleation and growth of hydration products.

6. The method for preparing solid waste-based lightweight fine-grained ceramsite according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Dry mixing: Titanium gypsum, iron tailings powder and solid waste-based cementitious materials are mixed thoroughly in proportion to obtain a uniform dry mixture; (2) Solution preparation: Dissolve the chelating agent and the nanocrystal nucleus early strength agent in the mixing water after deducting the water content of the raw materials to form a uniform additive solution; (3) Wet mixing: Mix the dry mixture obtained in step (1) with the additive solution obtained in step (2) and stir evenly to obtain a wet material with good plasticity; (4) Granulation: The wetted material obtained in step (3) is fed into an inclined granulation device for rolling granulation to obtain a wet spherical green body; (5) Curing at room temperature: The wet spherical blank is cured at room temperature to obtain initial strength; (6) Steam curing: The green body treated in step (5) is steam cured at 60-95℃ for 3-12 hours; (7) Drying: The green body after step (6) is dried to remove residual moisture and obtain solid waste-based lightweight fine ceramsite finished product.

7. The application of solid waste-based lightweight fine-grained ceramsite as a fine aggregate in plastering mortar according to any one of claims 1-5.