A multi-source full-solid waste geopolymer based on oyster shell powder and a preparation method thereof

Abstract

The present application belongs to the technical field of baking-free bricks, and particularly relates to a multi-source full-solid waste geopolymer baking-free brick based on oyster shell powder and a preparation method thereof, which is prepared from the following raw materials in terms of mass fraction: 0.1-0.25 parts of oyster shell powder, 0.1-0.60 parts of fly ash, 0.25-1.0 parts of slag, 0.8-2.0 parts of waste ceramic particles, 1-2.9 parts of recycled concrete aggregate, and 0.33-1.23 parts of alkali activator. The multi-source full-solid waste geopolymer baking-free brick of the present application successfully resolves the contradiction between the low fluidity caused by high calcium and the high strength requirement by increasing the proportion of high-quality fly ash and matching with slag under the premise of controlling the dosage of oyster shell powder.

Description

Technical Field

[0001] This invention belongs to the field of non-fired brick technology, specifically relating to a non-fired brick based on oyster shell powder and its preparation method. Background Technology

[0002] Existing research indicates that oyster shell powder can be used in asphalt. Using oyster shell powder as a filler in asphalt and asphalt mixtures, specifically replacing ordinary mineral powder as a filler in asphalt mastic, produces oyster shell powder asphalt mastic with better high-temperature stability, water stability, and temperature sensitivity compared to ordinary mineral powder asphalt mastic. Furthermore, using oyster shell powder to replace dolomite as a filler in asphalt mixtures results in asphalt mixtures with greater resistance to rutting and water damage. Studies have also investigated the use of seafood shell powder (clam shells, oyster shells, scallop shells) to prepare asphalt mastic. Oyster shell powder, replacing mineral powder, improves the low-temperature crack resistance of asphalt mixtures. However, research on the application of oyster shells in geopolymers is relatively limited.

[0003] In the field of non-fired brick technology, the preparation of non-fired bricks using alkali-activated materials has been widely used in the construction industry, such as CN119285288A and CN116553864A. However, the CaO content of oyster shells can reach more than 95%. Their high calcium content, when combined with the high alkalinity of the alkali activator, will cause the slurry to react rapidly and reduce its fluidity, thus failing to meet the requirements of the pressing and molding process of non-fired bricks. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a multi-source, all-solid-waste geopolymer non-fired brick based on oyster shell powder and its preparation method.

[0005] A multi-source, all-solid-waste geopolymer non-fired brick based on oyster shell powder is made from the following raw materials by mass fraction: Oyster shell powder 0.1 to 0.25 parts, fly ash 0.1 to 0.60 parts, slag 0.25 to 1.0 parts, waste ceramic particles 0.8 to 2.0 parts, recycled concrete aggregate 1 to 2.9 parts, alkali activator 0.33 to 1.23 parts.

[0006] The multi-source solid waste geopolymer non-fired brick of the present invention, under the premise of setting the amount of oyster shell powder, increases the proportion of fly ash and combines it with slag, successfully reconciling the contradiction between low fluidity caused by high calcium and high strength requirements, and obtaining high fluidity and high strength at the same time.

[0007] Preferably, the surface area of ​​the oyster shell powder is 500m². 2 / kg~700m 2 / kg.

[0008] Preferably, the particle size of the waste ceramic particles is <4.75mm.

[0009] Preferably, the particle size of the recycled concrete aggregate is 5mm to 31.5mm.

[0010] Preferably, the alkaline activator is prepared from 0.03 to 0.18 parts of sodium hydroxide, 0.15 to 0.55 parts of sodium silicate water glass, and 0.15 to 0.50 parts of water.

[0011] A method for preparing the aforementioned multi-source solid waste geopolymer non-fired brick includes the following steps: Active oyster shell powder is obtained by calcining oyster shells at 800℃~1000℃ for 2~4 hours and then grinding them. Fly ash, slag and active oyster shell powder are mixed evenly, then waste ceramic particles and recycled concrete aggregate are added and mixed evenly; then alkali activator is added and mixed evenly to obtain geopolymer. The geopolymer is pressed and cured to obtain the multi-source solid waste geopolymer non-fired brick.

[0012] Preferably, the Na2O content in the alkali activator is 6%~10%.

[0013] Preferably, the pressing is performed by applying pressure at 15MPa to 25MPa and holding the pressure for 10 to 30 seconds.

[0014] Preferably, the curing conditions are steam curing at 40℃~60℃ for 12h~24h.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention aims to produce a multi-source, all-solid-waste geopolymer non-fired brick by utilizing oyster shell powder, fly ash, and slag as cementing materials, waste ceramic particles as fine aggregate, and recycled concrete aggregate as coarse aggregate. This invention transforms various solid wastes into geopolymer non-fired bricks, forming a good model for resource recycling, alleviating resource pressure, and promoting the green and environmentally friendly development of the construction industry. Furthermore, this geopolymer non-fired brick has good mechanical properties, high compressive strength, and can provide reliable support for building structures. Detailed Implementation

[0016] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods.

[0017] The main technical problem solved by this invention is how to efficiently utilize industrial waste (oyster shell powder, fly ash, and slag) as a cementing material, and use waste ceramic particles as fine aggregate and recycled concrete aggregate as coarse aggregate to prepare a multi-source solid waste geopolymer non-fired brick based on oyster shell powder. Specific technical problems include: (1) Utilizing the rich CaO content: Oyster shell powder contains a large amount of CaO, which can be used to adjust the CaO content in the precursor material, not only reducing the dependence on traditional calcium sources, but also improving the density and strength of the geopolymer by appropriately increasing the CaO content. (2) Activation of oyster shell powder, fly ash, and slag: These materials have low activity, which can be improved by alkali activation technology, and the activity of oyster shell powder can also be improved by combustion and grinding, so that they can fully participate in the reaction in the geopolymer. (3) Influence of aggregates: Waste ceramic particles and recycled concrete aggregates have irregular shapes and rough surfaces, which affect the working performance of geopolymers. Furthermore, their strength and porosity also affect the mechanical properties and durability of geopolymers. It is necessary to study the optimal mix proportion to ensure the excellent overall performance of geopolymers.

[0018] Multi-source solid waste geopolymer non-fired bricks are mainly composed of the following components mixed in a specific ratio: oyster shell powder (surface area 500-700 m²). 2 The composition includes: ( / kg) fly ash (grades I and II), slag (grades S95 and S105), waste ceramic particles (particle size <4.75mm), recycled concrete aggregate (particle size between 5mm and 31.5mm), sodium silicate water glass, sodium hydroxide, and water. The water-cement ratio of the geopolymer is 0.30-0.45, which is the ratio of water to the total mass of oyster shell powder, fly ash, and slag. The water glass modulus is 1.0-1.6. Sodium silicate water glass and sodium hydroxide are used as alkali activators, with a Na2O content of 6%-10% in the alkali activators.

[0019] A method for preparing a multi-source solid waste geopolymer non-fired brick based on oyster shell powder is as follows: (1) Place the washed and dried oyster shells in a muffle furnace and calcine them at 800℃-1000℃ for 2-4 hours to convert them into an active calcium source mainly composed of calcium oxide. Then, grind the calcined oyster shells in a ball mill until the specific surface area is 500-700m² / kg and pass them through a 200-mesh sieve to obtain active oyster shell powder; (2) Mix sodium hydroxide and water evenly, then mix and stir with sodium silicate water glass evenly and cool to room temperature to obtain an alkali activator; (3) Add fly ash, slag and active oyster shell powder to a mixer and stir evenly; then add waste ceramic particles and recycled concrete aggregate and continue stirring. Stir; then add the alkali activator cooled to room temperature, continue stirring to obtain the geopolymer; (4) immediately pour the well-stirred geopolymer into a 240mm×115mm×53mm mold, place it on a vibrating table and vibrate for 20 seconds; then move the mold to a hydraulic brick making machine, press it at a rate of 2-5kN / s to 15-25MPa, and hold the pressure for 10-30 seconds to demold and obtain the brick blank; place the brick blank on a flat pallet, and let it stand for 2-4 hours in an environment with room temperature (20±5℃) and relative humidity not less than 50%, and after the surface has initially hardened, place it in a steam curing environment at 40-60℃ for 12-24h, and then seal it at room temperature for 7-28d.

[0020] A multi-source solid waste geopolymer non-fired brick based on oyster shell powder is prepared by mixing oyster shell powder, fly ash, slag, waste ceramic particles, recycled concrete aggregate, sodium hydroxide, sodium silicate water glass, and water. The raw material ratio is (0.1~0.25):(0.1~0.60):(0.25~1.0):(0.8~2.0):(1~2.9):(0.03~0.18):(0.15~0.55):(0.15~0.50).

[0021] The main component of oyster shell waste is CaO. After processing through grinding and combustion, it can be used as a cementing material. Using it to prepare geopolymer non-fired bricks can realize the resource utilization of waste. Oyster shells can have a CaO content of over 95%. Adding ground oyster shells to geopolymers can improve cementing properties, promote the crystallization and precipitation of hydration products of other cementing materials (such as fly ash and slag), and facilitate the formation of a denser structure. Furthermore, CaO... 2+ It can promote the dissolution of aluminosilicates, shorten the gel formation time, and improve early strength. Oyster shells, through calcium source activation and bio-structure empowerment, break through the strength and durability bottlenecks of traditional non-fired bricks.

[0022] Example 1 A multi-source solid waste geopolymer non-fired brick based on oyster shell powder is made from oyster shell powder, fly ash, slag, waste ceramic particles, recycled concrete aggregate, sodium hydroxide, sodium silicate water glass and water; The masses of oyster shell powder, fly ash, slag, waste ceramic particles, recycled concrete aggregate, sodium hydroxide, sodium silicate, water glass, and water are 100g, 300g, 600g, 1900g, 2900g, 30g, 150g, and 390g, respectively.

[0023] The preparation method of the non-fired bricks is as follows: (1) Place the washed and dried oyster shells in a muffle furnace and calcine them at 900°C for 3 hours to convert them into active calcium sources mainly composed of calcium oxide. Then, put the calcined oyster shells into a ball mill and grind them until the specific surface area is 600 m² / kg. Pass them through a 200-mesh sieve to obtain active oyster shell powder. (2) Mix sodium hydroxide and water evenly, then mix with sodium silicate water glass evenly and let cool to room temperature to obtain an alkaline activator; (3) Add fly ash, slag and active oyster shell powder to a mixer and mix evenly; then add waste ceramic particles and recycled concrete aggregate and continue mixing; then add alkali activator that has been cooled to room temperature and continue mixing to obtain geopolymer; (4) Immediately pour the well-stirred geopolymer into a 240mm×115mm×53mm mold and place it on a vibrating table to vibrate for 20 seconds; then move the mold to a hydraulic brick making machine, press it at a rate of 3kN / s to 20MPa, and hold the pressure for 20 seconds to form and demold to obtain a brick blank; place the brick blank on a flat pallet and let it stand for 3 hours in an environment with room temperature (20±5℃) and relative humidity not less than 50% until its surface is initially hardened, then place it under steam curing at 50℃ for 16 hours, and then seal it at room temperature for 15 days.

[0024] Example 2 The only difference between Example 2 and Example 1 is the ratio of raw materials, which is as follows: The masses of oyster shell powder, fly ash, slag, waste ceramic particles, recycled concrete aggregate, sodium hydroxide, sodium silicate water glass, and water are 150g, 500g, 350g, 1500g, 2500g, 50g, 300g, and 450g, respectively.

[0025] Example 3 The only difference between Example 3 and Example 1 is the ratio of raw materials, which is as follows: The masses of oyster shell powder, fly ash, slag, waste ceramic particles, recycled concrete aggregate, sodium hydroxide, sodium silicate water glass, and water are 200g, 300g, 500g, 1900g, 2800g, 40g, 250g, and 500g, respectively.

[0026] Example 4 The only difference between Example 4 and Example 1 is the ratio of raw materials, which is as follows: The masses of oyster shell powder, fly ash, slag, waste ceramic particles, recycled concrete aggregate, sodium hydroxide, sodium silicate water glass, and water are 100g, 600g, 300g, 1800g, 2700g, 30g, 400g, and 500g, respectively.

[0027] Example 5 The only difference between Example 5 and Example 1 is the ratio of raw materials, which is as follows: The masses of oyster shell powder, fly ash, slag, waste ceramic particles, recycled concrete aggregate, sodium hydroxide, sodium silicate water glass, and water are 250g, 250g, 500g, 2000g, 2900g, 30g, 550g, and 350g, respectively.

[0028] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is the ratio of raw materials, which is as follows: The masses of limestone powder, fly ash, slag, waste ceramic particles, recycled concrete aggregate, sodium hydroxide, sodium silicate water glass, and water are 100g, 300g, 600g, 1900g, 2900g, 30g, 150g, and 390g, respectively.

[0029] Mechanical properties tests were conducted on the unfired bricks of the examples and comparative examples, including slump test, 7-day compressive strength test and 28-day compressive strength test. The test results are shown in Table 1.

[0030] 1. The slump test procedure is as follows: (1) The well-mixed geopolymer slurry is loaded into the slump cone in three layers, and each layer is tamped 25 times. (2) Scrape the top of the cylinder and lift the slump cylinder vertically; (3) The height difference between the height of the measuring cylinder and the highest point of the specimen after collapse is the slump value (unit: mm).

[0031] 2. The test procedures for compressive strength at 7 days and 28 days are as follows: (1) Place the unfired brick specimen (240mm×115mm×53mm) cured to the specified age (7d or 28d) in the center of the lower pressure plate of the pressure testing machine; (2) Apply a uniform load at a rate of 0.5-1.0 kN / s until the specimen fails; (3) Record the maximum failure load and calculate the compressive strength according to the formula: Table 1: Comparison of mechanical property test results between the examples and comparative examples As shown in Table 1, oyster shell powder, as an active calcium source, can effectively promote the reaction and contribute good early strength (31.2 MPa at 7 days) when added in appropriate amounts (such as 0.10 parts in Example 1). However, when its dosage is increased to near the upper limit (0.25 parts in Example 5), the slump of the slurry drops sharply to 46 mm, and the 28-day compressive strength is only 25.9 MPa, the lowest among all examples. This proves that excessive oyster shell powder will seriously impair workability and may interfere with the formation of long-term gel structure. Therefore, its dosage must be strictly limited to a reasonable range (0.10-0.20 parts is preferred).

[0032] The spherical particles of fly ash significantly improved the fluidity of the slurry; in Examples 2-4, where fly ash was used in higher amounts, the slump was greater than 60 mm. More importantly, the later pozzolanic reaction of fly ash significantly contributed to the strength; for example, in Example 4 (0.60 parts), with the highest fly ash content, the 28-day compressive strength reached the optimal 38.8 MPa. Slag, on the other hand, mainly ensured early strength development. Example 2 (0.50 parts fly ash, 0.35 parts slag) achieved good fluidity (62 mm) while also reaching a later strength of 35.2 MPa, demonstrating a good synergistic effect between the two.

[0033] The total amount of aggregate (waste ceramics and recycled concrete) directly affects the abundance of the paste. Example 5 has the highest total aggregate amount (4.9 parts) but the lowest slump (46 mm), indicating that the cementitious paste is insufficient to fully coat and lubricate the aggregate, resulting in poor workability and weak interfaces, and consequently, the lowest strength. Fine aggregate (waste ceramic particles <4.75 mm) and coarse aggregate (recycled concrete aggregate 5-31.5 mm) need to form a good gradation to construct a dense skeleton. Among the examples, Example 4 (1.8 parts waste ceramic particles and 2.7 parts recycled concrete aggregate) achieved both the highest fluidity and the highest strength, indicating that its aggregate gradation and cementitious paste content were most well matched, forming the densest microstructure.

[0034] Furthermore, the slump of Comparative Example 1 was comparable to that of Example 1, indicating a similar physical filling effect of limestone powder. However, its 7-day and 28-day compressive strengths were significantly lower than those of Example 1. This demonstrates that not all calcareous fillers can achieve the same effect. The oyster shell powder used in this invention, due to its special active CaO component and microstructure, can actively participate in the geological polymerization reaction in an alkaline-activated environment, generating more cementitious products, thereby significantly improving the core mechanical properties of the brick. Limestone powder (mainly composed of CaCO3) has very low activity and mainly exists in the form of an inert filler, thus its reinforcing effect is limited.

[0035] In summary, the formulation of Example 4 achieved the optimal balance between slump and strength at various ages. This result verifies the core formulation strategy of this invention: by controlling the amount of oyster shell powder, increasing the proportion of high-quality fly ash and adding an appropriate amount of slag, the contradiction between "low fluidity caused by high calcium" and "high strength requirements" can be successfully reconciled. All data from the examples fall within the scope of the claims, and the performance meets the standards, fully demonstrating the rationality and necessity of the claimed protection range.

[0036] It should be noted that when numerical ranges are mentioned in the claims of this invention, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. To avoid redundancy, the present invention describes preferred embodiments.

[0037] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0038] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A non-fired brick based on oyster shell powder and multi-source solid waste geopolymer, characterized in that, Made from the following raw materials by weight: Oyster shell powder 0.1 to 0.25 parts, fly ash 0.1 to 0.60 parts, slag 0.25 to 1.0 parts, waste ceramic particles 0.8 to 2.0 parts, recycled concrete aggregate 1 to 2.9 parts, alkali activator 0.33 to 1.23 parts.

2. The multi-source solid waste geopolymer non-fired brick according to claim 1, characterized in that, The surface area of ​​the oyster shell powder is 500m². 2 / kg~700m 2 / kg.

3. The multi-source solid waste geopolymer non-fired brick according to claim 1, characterized in that, The particle size of the waste ceramic particles is <4.75mm.

4. The multi-source solid waste geopolymer non-fired brick according to claim 1, characterized in that, The particle size of the recycled concrete aggregate is 5mm to 31.5mm.

5. The multi-source solid waste geopolymer non-fired brick according to claim 1, characterized in that, The alkaline activator is prepared from 0.03 to 0.18 parts of sodium hydroxide, 0.15 to 0.55 parts of sodium silicate water glass, and 0.15 to 0.50 parts of water.

6. A method for preparing multi-source solid waste geopolymer non-fired bricks according to any one of claims 1 to 5, characterized in that, Includes the following steps: Active oyster shell powder is obtained by calcining oyster shells at 800℃~1000℃ for 2~4 hours and then grinding them. Fly ash, slag and active oyster shell powder are mixed evenly, then waste ceramic particles and recycled concrete aggregate are added and mixed evenly; then alkali activator is added and mixed evenly to obtain geopolymer. The geopolymer is pressed and cured to obtain the multi-source solid waste geopolymer non-fired brick.

7. The preparation method according to claim 6, characterized in that, The Na2O content in the alkaline activator is 6%~10%.

8. The preparation method according to claim 6, characterized in that, The compression is achieved by applying pressure at 15MPa to 25MPa and holding the pressure for 10 to 30 seconds.

9. The preparation method according to claim 6, characterized in that, The curing conditions are steam curing at 40℃~60℃ for 12h~24h.

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