Environment-friendly high-strength ceramsite and preparation method thereof

Abstract

The invention relates to the technical field of waste utilization, in particular to environment-friendly high-strength ceramsite and a preparation method thereof. The raw materials comprise copper tailings, fly ash, bentonite and calcium fluoride. The preparation method comprises the following steps: mixing the raw materials to prepare a ceramsite blank, sintering the ceramsite blank in a high-temperature furnace according to a set heating curve, and naturally cooling after sintering to obtain the high-strength ceramsite. According to the ceramsite, industrial solid wastes such as copper tailings are used as main raw materials, and components such as silicon dioxide and aluminum oxide contained in the industrial solid wastes are melted and recombined at high temperature to form a compact structure, so that the mechanical property is improved. The product is green, environment-friendly, high in strength and suitable for concrete aggregate, and resource utilization of tailings is achieved.

Description

Technical Field

[0001] This invention relates to the field of waste utilization technology, specifically to environmentally friendly high-strength ceramsite and its preparation method. Background Technology

[0004] Firing ceramsite can be used as a resource-efficient, harmless, and volume-reducing method to utilize copper tailings and fly ash. Some processes use copper tailings as the main raw material, adding clay, binders, and other auxiliary materials, and then prepare ceramsite through processes such as batching, mixing, granulation, and sintering, which consumes a large amount of arable land clay. Summary of the Invention

[0005] The purpose of this invention is to provide environmentally friendly high-strength ceramsite and its preparation method to solve the problems of environmental pollution and consumption of arable land clay during processing mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: environmentally friendly high-strength ceramsite, comprising the following raw materials in parts by weight:

[0007] Copper tailings: 50.53 parts to 155.56 parts;

[0008] Fly ash: 0 parts to 101.05 parts;

[0009] Bentonite: 0 parts to 47.06 parts;

[0010] Calcium fluoride: 0 parts to 18.82 parts.

[0011] Preferably, the copper tailings contain 40%-50% silica, 10%-20% calcium oxide, 8%-15% aluminum oxide, and 5%-10% iron oxide, with the remainder being impurities; the fly ash contains 40%-60% silica, 25%-40% aluminum oxide, with the remainder being impurities.

[0012] A method for preparing environmentally friendly high-strength ceramsite, the method being used to prepare the aforementioned environmentally friendly high-strength ceramsite, the specific steps of the preparation method are as follows:

[0013] S1: Preparation of high-strength ceramsite green body: Dry copper tailings, fly ash, bentonite and calcium fluoride; Weigh the dried copper tailings, fly ash, bentonite and calcium fluoride according to the mass ratio described in claim 1, and mix the raw materials using a ball mill;

[0014] Use a vibrating screen to continuously vibrate and sieve for more than 10 minutes to sieve out the powder. Use the sieved powder to make a green body. Dry the green body to obtain a high-strength ceramsite green body.

[0015] S2: Preparation of high-strength ceramsite green body by sintering: The high-strength ceramsite green body is placed in the furnace chamber of a muffle furnace and a heating curve is set for sintering. The heating rate is 5℃ / min-20℃ / min, and the specific heating rate can be selected as 5℃ / min, 8℃ / min, 10℃ / min, 12℃ / min, 15℃ / min, 18℃ / min, or 20℃ / min. After the temperature reaches 300℃-450℃, it is maintained for 5min-20min; the temperature can be selected as 300℃, 320℃, 350℃, 380℃, 400℃, 420℃, or 450℃. The holding time can be selected as 5 min, 10 min, 15 min, 18 min or 20 min; then continue to heat up to the set maximum sintering temperature of 900℃-1300℃, and then hold for 3 min to 15 min, and then cool down naturally to obtain high-strength ceramsite; the maximum sintering temperature can be selected as 900℃, 950℃, 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, 1250℃ or 1300℃, and the latest temperature holding time can be selected as 3 min, 5 min, 8 min, 10 min, 12 min or 15 min.

[0016] Preferably, the minimum sintering temperature in S2 is 1100℃-1250℃, and the sintering time is 3 minutes.

[0017] Preferably, the drying temperature in S1 is 100℃-120℃, the ball mill speed is 200r / min-400r / min, and the drying temperature can be selected as 100℃, 110℃ or 120℃.

[0018] Preferably, the aperture in S1 is 100-200 mesh, and the aperture can be selected as 100 mesh, 120 mesh, 150 mesh, 180 mesh or 200 mesh.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] First, copper tailings, fly ash, and bentonite are low in cost and readily available, which can reduce the raw material cost of high-strength ceramsite and reduce the environmental pollution caused by copper tailings and fly ash.

[0021] Secondly, the development cycle of high-strength ceramsite produced by sintering is shorter than that of non-fired ceramsite.

[0022] Third, this high-strength ceramsite has a dense internal structure and high strength. This invention is scientifically and rationally designed, using copper tailings, fly ash, and bentonite as the main raw materials. Under high-temperature conditions, components such as silica and alumina in the raw materials melt and recombine, generating high-strength mullite and corundum phases. These crystalline phases fill the ceramsite structure, making it denser, thus endowing the ceramsite with high-strength properties, making it suitable for use as concrete aggregate.

[0023] Fourth, this high-strength ceramsite has a water absorption rate of approximately 0.5%. It uses copper tailings and fly ash as the main raw materials, with calcium fluoride as an additive to lower the melting point. Furthermore, the material achieves surface vitrification in its molten state, enhancing its strength and significantly reducing water absorption, without affecting the water-cement ratio of the concrete.

[0024] Fifth, existing processes use copper tailings as the main raw material, adding clay, binders, and other auxiliary materials to prepare ceramsite through processes such as batching, mixing, granulation, and sintering, which consumes a large amount of arable land clay. This invention mixes copper tailings with fly ash, improving resource utilization, reducing pollutant emissions, and finding the optimal ratio to prepare high-strength ceramsite with superior performance.

[0025] Sixth, this invention employs a segmented sintering process in the sintering of expanded clay aggregates. Before formal firing, a preheating stage is set up to fully preheat the expanded clay aggregates. This preheating process allows the expanded clay aggregates to gradually increase in temperature, effectively avoiding cracking caused by sudden temperature rises. Simultaneously, sufficient preheating promotes the early release of volatile components and moisture in the raw materials, reducing the amount of gas generated and the degree of expansion during the firing stage, thereby increasing the density of the expanded clay aggregates and enhancing their final strength. Attached Figure Description

[0026] Figure 1 The graph shows the changes in the size of the ceramsite after sintering the 10 different ingredients in Table 3 at different high temperatures.

[0027] Figure 2 The XRD composition analysis diagram of the high-strength ceramsite in Table 7 is shown below;

[0028] Figure 3 This is a bar chart showing the compressive strength of the 10 ingredients in Table 3 after being subjected to different sintering parameters;

[0029] Figure 4 The diagram shows the water absorption rate and apparent density of the 10 ingredients in Table 3 after 1 hour of sintering parameter (6);

[0030] Figure 5 The compressive strength diagram of the 10 ingredients in Table 3 after the application of sintering parameter (6);

[0031] Figure 6 The graph shows the test results of the compressive strength of the expanded clay aggregate at different maximum sintering temperatures for the new ingredients;

[0032] Figure 7 XRD patterns of high-strength ceramsite with new ingredients at different maximum sintering temperatures;

[0033] Figure 8 These are microscopic images of the interior of high-strength ceramsite in Example 61 at a depth of 10 micrometers.

[0034] Figure 9Microscopic images of the interior of high-strength ceramic particles in Example 61 at a 500-nanometer scale;

[0035] Figure 10 These are microscopic images of the interior of high-strength ceramsite in Example 62 at a depth of 10 micrometers.

[0036] Figure 11 These are microscopic images of the interior of high-strength ceramic particles at a 500-nanometer scale, as shown in Example 62.

[0037] Figure 12 These are microscopic images of the interior of high-strength ceramsite in Example 63 at a depth of 10 micrometers.

[0038] Figure 13 The images show the microscopic internal structure of high-strength ceramic particles in Example 63 at a 500-nanometer scale.

[0039] Figure 14 These are microscopic images of the interior of high-strength ceramsite in Example 64 at a depth of 10 micrometers.

[0040] Figure 15 These are microscopic images of the interior of high-strength ceramic particles at a 500-nanometer scale, as shown in Example 64. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0042] The preparation method of environmentally friendly high-strength ceramsite includes the following steps:

[0043] S1: Preparation of high-strength ceramsite green body: Dry copper tailings, fly ash, bentonite, and calcium fluoride at a drying temperature of 105℃; weigh the dried copper tailings, fly ash, bentonite, and calcium fluoride according to the following mass ratio, and mix the raw materials using a ball mill; use a planetary ball mill, and when the ball mill is working, the ball mill speed is 400 r / min, and the mixing in the ball mill continues for more than 20 minutes; then use a vibrating screen to continuously vibrate and sieve for more than 10 minutes to sieve out the powder, use the sieved powder to make green body, and dry the green body to obtain the high-strength ceramsite green body, wherein the diameter of the vibrating screen is 30cm and the aperture is 100 mesh.

[0044] The quality ratio of raw materials is as follows:

[0045] Copper tailings: 50.53 parts to 155.56 parts;

[0046] Fly ash: 0 parts to 101.05 parts;

[0047] Bentonite: 0 parts to 47.06 parts;

[0048] Calcium fluoride: 0 parts to 18.82 parts.

[0049] The copper tailings contain 47.26% silica, 17.50% calcium oxide, 10.63% aluminum oxide, and 8.60% iron oxide, with the remainder being impurities; the fly ash contains 51% silica, 35.31% aluminum oxide, with the remainder being impurities.

[0050] S2: Preparation of high-strength ceramsite green body by sintering: The high-strength ceramsite green body is placed in the furnace chamber of a muffle furnace and a heating curve is set for sintering. The heating rate is 15℃ / min. After the temperature reaches 350℃, it is maintained for 15min. Then the temperature is continued to rise to the set maximum sintering temperature of 900℃-1300℃, and then maintained for 3min to 15min. After that, it is naturally cooled to obtain high-strength ceramsite.

[0051] The above-mentioned copper tailings, fly ash, and bentonite were used to conduct experiments with the addition of calcium fluoride. The sintering parameters of the specific experimental samples are shown in Tables 1-2 below, and the composition ratios and results are shown in Tables 3-8 below. Tables 3-8 show the same composition but different sintering curves.

[0052] Table 9 shows the apparent density, compressive strength, and water absorption of the optimized new batch (set as copper tailings, fly ash, and bentonite in a mass ratio of 52:104:4) under different sintering parameters.

[0053] Table 1 Sintering parameters

[0054]

[0055]

[0056] Table 2 Optimized sintering parameters

[0057]

[0058] Table 3 shows the proportions of copper tailings, fly ash, bentonite, and calcium fluoride as follows, with a maximum sintering temperature of 900℃ and a maximum temperature duration of 6 minutes.

[0059]

[0060]

[0061] Table 4 shows the proportions of copper tailings, fly ash, bentonite, and calcium fluoride as follows, with a maximum sintering temperature of 1100℃ and a maximum temperature duration of 9 min.

[0062]

[0063] Table 5 shows the proportions of copper tailings, fly ash, bentonite, and calcium fluoride as follows, with a maximum sintering temperature of 1200℃ and a maximum temperature duration of 3 min.

[0064]

[0065]

[0066] Table 6 shows the proportions of copper tailings, fly ash, bentonite, and calcium fluoride as follows, with a maximum sintering temperature of 1000℃ and a maximum temperature duration of 15 min.

[0067]

[0068] Table 7 shows the following mass ratios of copper tailings, fly ash, bentonite, and calcium fluoride, with a maximum sintering temperature of 1150℃ and a maximum temperature duration of 3 minutes.

[0069]

[0070] Table 8 shows the following mass ratios of copper tailings, fly ash, bentonite, and calcium fluoride, with a maximum sintering temperature of 900℃ and a maximum temperature duration of 12 min.

[0071]

[0072]

[0073] Table 9 shows the apparent density, compressive strength, and water absorption of the optimized new ingredients under different sintering parameters.

[0074]

[0075] Before sintering, the diameter of the ceramsite is 10mm. Figure 1 The changes in the morphology and size of the expanded clay aggregate after calcination at different high temperatures are shown. The sintering parameters of the expanded clay aggregate correspond to those in Table 1, and are labeled 1-10. The component ratios correspond to those in Tables 3-8. Tables 3-8 show the same ingredients but different sintering curves. Figure 1It was observed that the ceramsite exhibited significant melting at maximum temperatures of 1200℃ and 1300℃. At these temperatures, most of the ceramsite appeared as flat, sheet-like particles, losing their compressive strength. Therefore, the ceramsite group with sintering parameter 3 was not discussed or tested. However, at 1300℃, the second group of ceramsite did not melt and underwent significant expansion, with researchers observing numerous small pores on the surface. At lower maximum temperatures, the ceramsite's reaction was insufficient, resulting in no significant strength difference. Therefore, the experimental groups for ceramsite with sintering parameters 8 and 10 were cancelled. Furthermore, observation of the ceramsite under each sintering parameter revealed that the duration of the maximum sintering temperature had little impact on whether the ceramsite ultimately reacted and melted. Therefore, for sintering parameter 6, the peak temperature was adjusted to 1150℃, the holding time was set to 3 minutes, and the experimental group for ceramsite with sintering parameter 9 was cancelled.

[0076] Figure 2 To correspond with the XRD patterns of the high-strength ceramsite in Table 7, the main constituent phases of this type of ceramsite sample are quartz (SiO2), feldspar (mainly calcium feldspar (CaAl2Si2O8) and sodium feldspar (NaSi3AlO8)), and mullite (Al6Si2O8). 13 The peak strength analysis of the ceramsite in Example 41 shows that its peak strength is relatively weak, and its high bentonite content leads to significant expansion during sintering, resulting in low compressive strength. In the images corresponding to ceramsites in Examples 43, 45, 48, 49, and 50, the peak strength of various feldspars is observed to be high, while the quartz peak is relatively weak, indicating that quartz may have been converted into feldspar during the reaction, thus reducing the sample strength. Simultaneously, these groups show higher fluorite powder content and lower fly ash content compared to other groups, indicating a negative impact on compressive strength. In Examples 42, 44, and 47, as the relative fly ash content increases, the feldspar and quartz peaks gradually weaken, while the corresponding compressive strength increases. This suggests that it may have been converted into mullite, which can support strength. Weak peaks corresponding to pyroxene were observed in all these samples, and they appeared more frequently in the groups with lower compressive strength. This may be due to incomplete conversion of feldspar and quartz during the reaction. In summary, the compressive strength of ceramsite is basically consistent with its XRD analysis.

[0077] Figure 4 To correspond with the 1-hour water absorption rate and apparent density of high-strength ceramsite in Table 7, the results show that the higher the density, the lower the water absorption rate. Ceramsite samples 42, 44, and 47 exhibited higher strength, and their higher density compared to other ceramsite samples is clearly observed in the figure. Conversely, the corresponding moisture content was the opposite; the high-strength ceramsite absorbed almost no water. In general, the density of the ceramsite group with higher compressive strength can be controlled within the range of 1.90-2.00 × 10⁻⁶. 3 kg / m3 Furthermore, the higher the density of the expanded clay aggregate, the lower its water absorption rate, which should be controlled within 0.5-0.6%. Ceramic aggregate No. 2 has the highest compressive strength, with a density of 1.98 × 10⁻⁶. 3 kg / m 3 The water absorption rate is 0.51%.

[0078] Figure 5 The compressive strength of the high-strength ceramsite corresponds to that in Table 7. The compressive strength of the ceramsite in Example 42 is significantly higher than the other groups, followed by Examples 44 and 47. In these groups, the proportions of bentonite and calcium fluoride are relatively small, while the ratio of copper tailings to fly ash reaches 1:1 or even 1:2. The compressive strength of Example 41 is far lower than the other groups, even though the ceramsite sample in this group did not contain fly ash and had a relatively high proportion of bentonite and calcium fluoride. This indicates that adding fly ash significantly improves the compressive strength of ceramsite, while the addition of bentonite and calcium fluoride does not significantly improve the compressive strength and may even cause a decrease in strength.

[0079] Figure 7 Corresponding to the XRD patterns of the high-strength ceramsite in Table 9, it can be observed that at similar sintering temperatures, the crystal phase composition of the ceramsite did not change, but it underwent a relatively significant transformation. After optimization, the main mineral composition of the ceramsite remains quartz (SiO2), feldspar, and mullite (Al6Si2O3). 13 ) and pyroxene.

[0080] As can be seen from the peak intensity of Example 61, at lower temperatures, quartz exhibits higher peak intensity, while feldspar and mullite show relatively lower peak intensities. This indicates that at lower temperatures, the constituent phases do not undergo significant reactions, resulting in lower strength. With increasing temperature, the spectra of Examples 62, 63, and 64 show that the peak intensities of feldspar and mullite gradually increase, exhibiting the opposite trend to quartz, suggesting a possible phase transformation in quartz. At this point, the content of feldspar and mullite gradually increases. Mullite significantly contributes to improving the structural strength of the ceramsite, resulting in a more pronounced strength increase compared to Example 61. However, as the temperature continues to rise, the spectra of Examples 63 and 64 show that the peak intensities of feldspar and mullite do not continue to increase. This is due to the pyrolysis of orthoclase and the partial transformation of mullite into feldspar, leading to a decrease in the strength of the ceramsite samples.

[0081] Although the main components of the ceramsite groups are the same, their microstructure changes significantly with temperature. Microscopic images of the ceramsite groups in Example 61 at 10 micrometers and 500 nanometers are shown below. Figure 8 , Figure 9As shown, its overall structure is a dispersed granular structure, with varying density and irregularity. Further magnification of its microstructure reveals an extremely uneven surface and noticeable gaps between surfaces. This indicates that the ceramsite has not yet reacted at this temperature. Therefore, the ceramsite samples in this group exhibit low compressive strength.

[0082] The microscopic images of the ceramsite in Examples 62, 63, and 64 at 10 micrometers and 500 nanometers are analyzed as follows: Figure 10 , Figure 11 , Figure 12 , Figure 13 , Figure 14 , Figure 15 It can be concluded that as the temperature rises, a reaction begins to occur inside the ceramsite, transforming the irregular granular structure into a dense structure with some small pores. This denser structure significantly improves the compressive strength of the ceramsite. In comparison, Figure 10 , Figure 11 Its surface has a more uniform distribution of fine pores, resulting in more uniform strength and a more significant improvement. And for... Figure 12 , Figure 13 Generally speaking, as the temperature continues to rise, the overall dense matrix does not change significantly, but the porosity between the matrix begins to change. Its distribution becomes noticeably uneven, and larger pores begin to appear, resulting in uneven pore size. Although magnified microstructures show that the matrix is ​​smoother at higher temperatures, this does not significantly improve strength. Instead, the uneven change in porosity causes a decrease in the strength of the ceramsite at higher temperatures.

[0083] This invention utilizes the relationship between the dosage of four raw materials (including copper tailings, fly ash, bentonite, and calcium fluoride) and compressive strength, employing stepwise regression technology to fit and optimize the batching. This method successfully optimized the experimental mix proportions, achieving the expected results. This invention provides a method for developing high-strength aggregates using copper tailings, fly ash, bentonite, and calcium fluoride, promoting the utilization of solid waste and reducing the mining of natural stone. Based on the results of compressive strength testing, XRD analysis, and microstructure examination, the following conclusions are drawn:

[0084] (1) When the mass ratio of copper tailings, fly ash and bentonite is 50.53:101.05:8.42, the sintering temperature is 1150℃, the sintering time is 3min, and the heating rate is 15℃ / min, ceramsite with an average compressive strength of 50.40MPa and whose main components are SiO2, sodium feldspar, calcium feldspar and mullite can be obtained.

[0085] (2) The composition of the ceramsite was optimized. Without adding calcium fluoride, the average compressive strength of the ceramsite was further enhanced to 57.13 MPa when the mass ratio of copper tailings, fly ash and bentonite was 52:104:4, the sintering temperature was 1150℃, the sintering time was 3 min and the heating rate was 15℃ / min.

[0086] (3) The optimal sintering temperature is 1150℃. After holding for 3 minutes, the water absorption rate of the resulting ceramsite is 0.497%, and the internal structure is relatively dense, so it can be used as concrete aggregate.

[0087] (4) XRD and SEM analyses of the ceramsite revealed that its main components are quartz, various feldspars, mullite, and a small amount of corundum. The enhanced strength is primarily due to the dense matrix, small pores, and relatively uniform distribution. Mullite and corundum can significantly improve the compressive strength of the ceramsite, but their content decreases at excessively low or high temperatures, leading to reduced strength. Therefore, preparation at a suitable temperature is necessary.

[0088] High-strength expanded clay aggregate is not only a sustainable alternative but also a means of reducing environmental pollution. Its development also underscores the prospects for eco-friendly building materials and promotes environmentally responsible research and development practices.

[0089] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or basic characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of the invention is defined by the appended claims rather than the foregoing description. Therefore, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

[0090] 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 alterations 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. Environmentally friendly high-strength ceramsite, characterized in that, The raw materials include the following parts by weight: Copper tailings: 50.53 parts to 155.56 parts; Fly ash: 0 parts to 101.05 parts; Bentonite: 0 parts to 47.06 parts; Calcium fluoride: 0 parts to 18.82 parts.

2. The environmentally friendly high-strength ceramsite according to claim 1, characterized in that: The copper tailings contain 40%-50% silica, 10%-20% calcium oxide, 8%-15% aluminum oxide, and 5%-10% iron oxide, with the remainder being impurities. The fly ash contains 40%-60% silica and 25%-40% alumina, with the remainder being impurities.

3. A method for preparing environmentally friendly high-strength ceramsite, characterized in that: This preparation method is used to prepare the environmentally friendly high-strength ceramsite as described in claim 1 or 2. The specific steps of this preparation method are as follows: S1: Preparation of high-strength ceramsite green body: Dry copper tailings, fly ash, bentonite and calcium fluoride; Weigh the dried copper tailings, fly ash, bentonite and calcium fluoride according to the mass ratio described in claim 1, and mix the raw materials using a ball mill; Use a vibrating screen to continuously vibrate and sieve for more than 10 minutes to sieve out the powder. Use the sieved powder to make a green body. Dry the green body to obtain a high-strength ceramsite green body. S2: Preparation of high-strength ceramsite green body by sintering: The high-strength ceramsite green body is placed in the furnace chamber of a muffle furnace and a heating curve is set for sintering. The heating rate is 5℃ / min-20℃ / min. After the temperature reaches 300℃-450℃, it is maintained for 5min-20min. Then the temperature is continued to rise to the set maximum sintering temperature of 900℃-1300℃, and then maintained for 3min-15min. After that, it is naturally cooled to obtain high-strength ceramsite.

4. The method for preparing environmentally friendly high-strength ceramsite according to claim 3, characterized in that: The minimum sintering temperature in S2 is 1100℃-1250℃, and the sintering time is 3 minutes.

5. The method for preparing environmentally friendly high-strength ceramsite according to claim 3, characterized in that: The drying temperature in S1 is 100℃-120℃, and the ball mill speed is 200r / min-400r / min.

6. The method for preparing environmentally friendly high-strength ceramsite according to claim 3, characterized in that: The aperture of S1 is 100-200 mesh.

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