A low-carbon, environmentally friendly, high-strength, fast-setting domestic waste incineration slag foam concrete and its preparation method

Abstract

The present invention discloses a low-carbon, environmentally friendly, high-strength, fast-setting domestic waste incineration slag foam concrete and a preparation method thereof. The main components of the foam concrete are cement, domestic waste incineration slag, a foaming liquid, waste diatomaceous earth, sodium hydroxide, sodium sulfate, and water. The domestic waste incineration slag and waste diatomaceous earth used in the present invention both have a certain volcanic ash activity and have the potential to be stimulated by strong alkali dissolution. The present invention uses waste diatomaceous earth as a silicon source and pre-treats the waste diatomaceous earth with a sodium hydroxide solution to convert it into a sodium silicate solution. The pre-treated diatomaceous earth solution is then used to stimulate the domestic waste incineration slag. In a strong alkaline environment, the calcium ions dissolved in the domestic waste incineration slag can directly react with the silicate ions dissolved in the pre-treated diatomaceous earth to form calcium silicate gel, which greatly shortens the setting time, increases the density of the foam concrete, ensures the strength of the foam concrete, and has the advantages of low carbon, environmental protection, and good economic benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of building material production, and in particular to a low-carbon, environmentally friendly, high-strength, fast-setting domestic waste incineration slag foam concrete and a preparation method thereof. Background Art

[0002] The current methods for treating domestic waste primarily include landfilling, composting, and incineration. Incineration offers the highest waste treatment efficiency, with a volume reduction capacity exceeding 90%. This effectively alleviates the problem of landfill waste encroachment, disinfects domestic waste through high-temperature incineration, and recovers heat for use in thermal power generation. Statistics show that slag generated during the incineration of domestic waste accounts for approximately 80% of the total combustion residue. Currently, landfilling is the primary method for treating domestic waste incineration slag. Therefore, there is an urgent need to develop more environmentally friendly, efficient, and economical domestic waste incineration slag recovery and treatment technologies.

[0003] Traditional foamed concrete typically consists of a cement paste and macropores. It is a lightweight cementitious material produced by generating bubbles or foam through a suitable foaming method and retaining them intact within the cement paste. This material is lightweight, soundproof, fire-resistant, and heat-insulating. Its high strength-to-weight ratio effectively reduces the weight of buildings while also lowering production and labor costs during manufacturing and transportation. Traditional foamed concrete uses cement as a binder. Cement production consumes significant resources, generates large amounts of dust, emits large amounts of carbon dioxide, and even produces harmful gases such as carbon monoxide and sulfur dioxide, placing significant pressure on the environment. Therefore, some studies have considered replacing cement with solid waste materials in the production of foamed concrete, hoping to achieve better environmental benefits. However, limited research has been conducted on the use of high-content municipal solid waste incineration slag in foamed concrete, and key technologies for using high-content municipal solid waste incineration slag in foamed concrete have yet to be developed. Furthermore, conventional foamed concrete still has lower strength and longer setting time than ordinary concrete. These factors restrict its widespread promotion and application. Furthermore, the low reactivity of municipal solid waste incineration slag, when used to replace large amounts of cement, will inevitably further reduce the strength of foamed concrete, and will also affect properties such as setting time and shrinkage. Therefore, a method for producing foamed concrete with a high content of municipal solid waste incineration slag is needed, which can produce foamed concrete with a short setting time and high strength. Summary of the Invention

[0004] In response to the shortcomings and deficiencies of existing technologies, the primary objective of the present invention is to develop a foamed concrete made from municipal solid waste incineration slag. This foamed concrete addresses the issues of low strength, long setting time, and high cement consumption associated with existing foamed concrete. This foamed concrete boasts high strength, a short setting time, and a high content of municipal solid waste incineration slag, making it a high-strength, fast-setting, and environmentally friendly foamed concrete construction material.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned high-strength and fast-setting domestic waste incineration slag foam concrete.

[0006] The foamed concrete is composed of the following materials in parts by mass:

[0007] Ordinary Portland cement 105~230

[0008] Domestic waste incineration slag 250~400

[0009] Foaming liquid 15~25

[0010] Waste diatomaceous earth 60~100

[0011] Sodium hydroxide 60~100

[0012] Sodium sulfate 12~20

[0013] Water 100~200

[0014] The cement is PO 42.5 type ordinary Portland cement.

[0015] The municipal solid waste incineration slag is a powdery particle obtained by screening out the unburned waste from the bottom ash of the slag, drying it at 100°C for 24 hours, and finally ball milling it. The particle size is above 200 mesh and the density is 2000~2300kg / m 3 The main chemical components are CaO, SiO2, and Al2O3 (the total content of the three is ≥75wt%), among which the CaO content is 40wt%~75wt%, and the Al2O3 content is 3wt%~10wt%.

[0016] The foaming liquid is prepared by diluting a composite protein foaming agent or an animal protein foaming agent by 30 times, and the foam prepared thereby needs to meet the following requirements: water secretion volume ≤ 15 ml in 1 hour, and sedimentation distance ≤ 5 mm in 1 hour.

[0017] The waste diatomaceous earth has a mesh size range of 200-400 mesh, an amorphous SiO2 content of ≥70wt%, an organic matter content of ≤11wt%, a heavy metal content of <0.005wt%, and a moisture content of 10wt%-30wt%.

[0018] The sodium hydroxide is anhydrous sodium hydroxide with a purity of ≥99%.

[0019] The sodium sulfate is anhydrous sodium sulfate with a purity of ≥99%.

[0020] The water usage requirements described above comply with the requirements of the "Standard for Water Use in Concrete" (JGJ63-2006).

[0021] The preparation process of the foamed concrete comprises the following steps:

[0022] (1) Remove the unburned garbage from the slag bottom ash, dry it at 100 °C for 24 h, and then ball mill it for 10 min. Sieve out the slag with mesh size of 200 or above for use;

[0023] (2) Measure each component material according to the above mass ratio;

[0024] (3) adding weighed solid sodium hydroxide to water and stirring thoroughly with a glass rod to completely dissolve the solid sodium hydroxide in water, adding the discarded diatomaceous earth to the sodium hydroxide solution after the sodium hydroxide solution is cooled, and stirring with a magnetic stirrer for 2 hours, and letting it stand for half an hour until the pretreated diatomaceous earth solution is ready for use;

[0025] (4) Add cement and domestic waste incineration slag into a mixing pot in proportion and stir for 1.5 minutes;

[0026] (5) The pretreated diatomaceous earth solution and sodium sulfate were mixed evenly in proportion and then put into a stirring pot, and stirred together with cement and domestic waste incineration slag for 2 minutes to prepare a slurry;

[0027] (6) Prepare foaming solution: Mix the foaming agent and water in a mass ratio of 1:30 and use a foaming machine to make foam;

[0028] (7) Add the foam to the slurry and stir slowly for 3 minutes until the foam is evenly dispersed in the slurry to obtain a foamed concrete slurry;

[0029] (8) The freshly mixed foamed slurry is injection molded, demolded after 1 day, and placed in a standard curing room for curing to a specified age to obtain a finished product of domestic waste incineration slag foam concrete.

[0030] The foamed concrete product has a dry bulk density of 500-800 kg / m3 measured at 28 days. 3 The 28d cubic compressive strength of the prepared test block is 2.5MPa~5MPa, and the setting time is 150~250 minutes.

[0031] The mechanism of the present invention is: pre-treating OH in diatomite solution - Ions can break the Si-O bonds, Ca-O bonds and Al-O bonds on the surface of slag bottom ash particles, increasing the [SiO4] 4- , Ca 2+and [AlO4] 4- content, providing more raw materials for the subsequent hydration reaction; on the other hand, pre-treating SiO4 in the diatomite solution 2- Ions can directly react with Ca in the slurry 2 + 、Al 3+ Combined to produce hydrated calcium silicate aluminate gel. The added sodium sulfate reacts with Ca(OH)2 in a highly alkaline environment to form secondary gypsum (CaSO4). The secondary gypsum reacts with C3A in the slurry to form ettringite, which further accelerates the hydration rate. In the early stage of hydration, ettringite serves as the skeleton, and the hydrated calcium silicate aluminate gel fills in between, which improves the density of the slurry ( Figure 1 ); At the same time, ettringite and hydrated calcium aluminosilicate gel provide early strength for the paste, and the paste can form a good support before the bubbles merge and break, resulting in a better pore structure of the foamed concrete ( Figure 2 ), a large number of small pores are evenly distributed in the slurry, and the pore shape is close to circular, which reduces the concentrated stress generated by the pores when subjected to force or deformation, so the specimen exhibits higher mechanical properties.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] (1) The present invention is a foamed concrete based on municipal solid waste incineration slag, which replaces a large amount of cement. Cement production is recognized as the link with the highest carbon emissions in the construction industry. Therefore, adding municipal solid waste incineration slag to foamed concrete instead of cement can not only unleash the resource potential of municipal solid waste incineration slag, but also further reduce the amount of cement used. This can achieve resource utilization of municipal solid waste incineration slag and reduce the land occupation caused by municipal solid waste incineration slag landfill.

[0034] (2) The present invention uses treated municipal solid waste incineration slag as raw material. The foamed concrete produced has a short setting time, high strength, and high utilization rate of municipal solid waste incineration slag. The prepared alkali-activated foamed concrete meets the requirements of the national standard "JGT266-2011 Foamed Concrete" and has superior performance compared to traditional cement foamed concrete.

[0035] (3) The present invention uses waste diatomaceous earth as a silicon source. Waste diatomaceous earth refers to the waste material discharged after being used as a filter aid in the food, chemical and other industries for a period of time. At present, waste diatomaceous earth is often disposed of by landfill, which on the one hand easily causes land pollution, and on the other hand also occupies a large amount of land resources. The present invention pre-treats the waste diatomaceous earth with sodium hydroxide, converting the waste diatomaceous earth into an activator, making it "waste but not discarded" and a beneficial way of low-carbon economic recycling.

[0036] (4) The preparation process of the present invention is simple, does not require large-scale equipment, and has the characteristics of low cost, small amount of cement used, short setting time, and high strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The scanning electron microscope test results of Example 1, Example 2, Example 3 and Control Example 1, Control Example 2, Control Example 3 are compared.

[0038] Figure 2 The backscattered scanning electron microscopy test results of Example 1, Example 2, Example 3 are compared with those of Control Example 1, Control Example 2 and Control Example 3. Specific embodiments

[0039] A high-strength, fast-setting, lightweight foamed concrete prepared from municipal solid waste incineration slag, wherein the main components are cement, municipal solid waste incineration slag, foaming liquid, waste diatomaceous earth, water glass, sodium sulfate, and water. The mass ratio of the components in the foamed concrete is:

[0040] Ordinary Portland cement 105~230

[0041] Domestic waste incineration slag 250~400

[0042] Foaming liquid 15~25

[0043] Waste diatomaceous earth 60~100

[0044] Sodium hydroxide 60~100

[0045] Sodium sulfate 12~20

[0046] Water 100~200.

[0047] The preparation process of the foamed concrete comprises the following steps:

[0048] (1) Remove the unburned garbage from the slag bottom ash, dry it at 100 °C for 24 h, and then ball mill it for 10 min to select the slag with the required particle size (above 200 mesh) for use;

[0049] (2) Measure each component material according to the above mass ratio;

[0050] (3) adding weighed solid sodium hydroxide to water and stirring thoroughly with a glass rod to completely dissolve the solid sodium hydroxide in water, adding the discarded diatomaceous earth to the sodium hydroxide solution after the sodium hydroxide solution is cooled, and stirring with a magnetic stirrer for 2 hours, and letting it stand for half an hour until the pretreated diatomaceous earth solution is ready for use;

[0051] (4) Add cement and domestic waste incineration slag into a mixing pot in proportion and stir for 1.5 minutes;

[0052] (5) The pretreated diatomaceous earth solution and sodium sulfate were mixed evenly in proportion and then put into a stirring pot, and stirred together with cement and domestic waste incineration slag for 2 minutes to prepare a slurry;

[0053] (6) Prepare foaming solution: Mix the foaming agent and water in a mass ratio of 1:30 and use a foaming machine to make foam;

[0054] (7) Add the foam to the slurry and stir slowly for 3 minutes until the foam is evenly dispersed in the slurry to obtain a foamed concrete slurry;

[0055] (8) The freshly mixed foamed slurry is injection molded, demolded after 1 day, and placed in a standard curing room for curing to a specified age to obtain a finished product of domestic waste incineration slag foam concrete.

[0056] Example 1:

[0057] A domestic waste incineration slag foam concrete (measured by mass) is prepared by taking the following raw materials: 170 parts of PO 42.5 type ordinary Portland cement, 260 parts of domestic waste incineration slag, 60 parts of waste diatomaceous earth, 100 parts of sodium hydroxide, 15 parts of sodium sulfate, 22 parts of foaming liquid, and 137 parts of water. The domestic waste incineration slag used in this embodiment is obtained by screening out unburned garbage from the slag bottom ash, drying at 100°C for 24 hours, and ball milling for 10 minutes; the obtained slag has a moisture content of 32.1wt%, and the average particle size of the slag after ball milling is 25.86μm; the main chemical components are SiO2 (21.68wt%), CaO (51.21wt%), Al2O3 (5.76wt%), and Fe2O3 (6.29wt%); the slag density is 2385 kg / m 3 The SiO2 content of the waste diatomite used was 94.07wt%, the average particle size was 32.26 μm, and the density was 2060kg / m 3 , specific surface area 488.1m 2 / kg. Finally, concrete was prepared according to the preparation method. The performance test results are shown in Table 1.

[0058] Example 2:

[0059] A domestic waste incineration slag foam concrete (measured by mass) is prepared by taking the following raw materials: 150 parts of PO 42.5 type ordinary Portland cement, 280 parts of domestic waste incineration slag, 60 parts of waste diatomaceous earth, 100 parts of sodium hydroxide, 15 parts of sodium sulfate, 22 parts of foaming liquid, and 137 parts of water. The domestic waste incineration slag used in this embodiment is obtained by screening out unburned garbage from the slag bottom ash, drying at 100°C for 24 hours, and ball milling for 10 minutes; the obtained slag has a moisture content of 32.1wt%, and the average particle size of the slag after ball milling is 25.86μm; the main chemical components are SiO2 (21.68wt%), CaO (51.21wt%), Al2O3 (5.76wt%), and Fe2O3 (6.29wt%); the slag density is 2385 kg / m 3 The SiO2 content of the waste diatomite used was 94.07wt%, the average particle size was 32.26 μm, and the density was 2060kg / m 3 , specific surface area 488.1m 2 / kg. Finally, concrete was prepared according to the preparation method. The performance test results are shown in Table 1.

[0060] Example 3:

[0061] A domestic waste incineration slag foam concrete (measured by mass) is prepared by taking the following raw materials: 150 parts of PO 42.5 type ordinary Portland cement, 280 parts of domestic waste incineration slag, 60 parts of waste diatomaceous earth, 100 parts of sodium hydroxide, 15 parts of sodium sulfate, 22 parts of foaming liquid, and 137 parts of water. The domestic waste incineration slag used in this embodiment is obtained by screening out unburned garbage from the slag bottom ash, drying at 100°C for 24 hours, and ball milling for 20 minutes; the obtained slag has a moisture content of 32.1wt%, and the average particle size of the slag after ball milling is 15.67μm; the main chemical components are SiO2 (21.68wt%), CaO (51.21wt%), Al2O3 (5.76wt%), and Fe2O3 (6.29wt%); the slag density is 2385 kg / m 3 The SiO2 content of the waste diatomite used was 94.07wt%, the average particle size was 32.26 μm, and the density was 2060kg / m 3 , specific surface area 488.1m 2 / kg. Finally, concrete was prepared according to the preparation method. The performance test results are shown in Table 1.

[0062] Comparative Example 1 (waste diatomaceous earth is not mixed with sodium hydroxide solution for pretreatment):

[0063] A domestic waste incineration slag foam concrete is prepared using the following raw materials (by weight): 170 parts PO 42.5 type ordinary Portland cement, 260 parts domestic waste incineration slag, 60 parts untreated waste diatomaceous earth, 100 parts sodium hydroxide, 15 parts sodium sulfate, 22 parts foaming liquid, and 137 parts water. The domestic waste incineration slag used in this comparative example was obtained by screening out unburned waste from the slag bottom ash, drying at 100°C for 24 hours, and ball milling for 10 minutes. The resulting slag had a moisture content of 32.1 wt%, and an average particle size of 25.86 μm after ball milling. The main chemical components were SiO2 (21.68 wt%), CaO (51.21 wt%), Al2O3 (5.76 wt%), and Fe2O3 (6.29 wt%). The slag density was 2385 kg / m 3 The waste diatomite used was dried at 100°C to constant weight, with a SiO2 content of 94.07wt%, an average particle size of 32.26 μm, and a density of 2060 kg / m 3 , specific surface area 488.1m 2 / kg. Finally, concrete was made by the following steps: (1) Measure each component material according to the above mass ratio; (2) Put cement, municipal solid waste incineration slag, and untreated waste diatomaceous earth into a mixing pot in proportion and stir for 1.5 minutes; then mix water, sodium hydroxide, and sodium sulfate in proportion and put them into a mixing pot, and stir them together with cement and municipal solid waste incineration slag for 2 minutes to obtain a pure slurry; (3) Prepare the foaming liquid: Mix the foaming agent and water in a mass ratio of 1:30 and use a foaming machine to obtain foam; (4) Add the foam to the pure slurry and stir slowly for 3 minutes until the foam is evenly dispersed in the slurry to obtain a foamed concrete slurry; (5) Injection mold the obtained freshly mixed foamed slurry, remove the mold after 1 day, and place it in a standard curing room for curing to the specified age to obtain a finished product of municipal solid waste incineration slag foam concrete. The performance test results are shown in Table 1.

[0064] Comparative Example 2 (without diatomaceous earth):

[0065] A domestic waste incineration slag foam concrete is prepared using the following raw materials (by weight): 170 parts PO 42.5 type ordinary Portland cement, 260 parts domestic waste incineration slag, 100 parts sodium hydroxide, 15 parts sodium sulfate, 22 parts foaming liquid, and 137 parts water. The domestic waste incineration slag used in this comparative example was obtained by screening out unburned waste from the slag bottom ash, drying at 100°C for 24 hours, and ball milling for 10 minutes. The resulting slag had a moisture content of 32.1 wt%, and an average particle size of 25.86 μm after ball milling. The main chemical components were SiO2 (21.68 wt%), CaO (51.21 wt%), Al2O3 (5.76 wt%), and Fe2O3 (6.29 wt%). The slag density was 2385 kg / m 3Finally, concrete was prepared by the preparation method. The performance test results are shown in Table 1.

[0066] Comparative Example 3 (domestic waste incineration slag without ball milling):

[0067] A domestic waste incineration slag foam concrete is prepared using the following raw materials (by weight): 170 parts PO 42.5 type ordinary Portland cement, 260 parts domestic waste incineration slag, 60 parts waste diatomaceous earth, 100 parts sodium hydroxide, 15 parts sodium sulfate, 22 parts foaming liquid, and 137 parts water. The domestic waste incineration slag used in this comparative example was obtained by screening out unburned waste from the slag bottom ash and then further screening out slag with a mesh size of approximately 50. The resulting slag had a moisture content of 32.1 wt% and an average particle size of 70.2 μm. The main chemical components were SiO2 (21.68 wt%), CaO (51.21 wt%), Al2O3 (5.76 wt%), and Fe2O3 (6.29 wt%). The slag density was 2385 kg / m 3 The SiO2 content of the waste diatomite used was 94.07wt%, the average particle size was 32.26 μm, and the density was 2060kg / m 3 , specific surface area 488.1m 2 / kg. Finally, concrete was prepared according to the preparation method. The performance test results are shown in Table 1.

[0068] Table 1 Performance test results of domestic waste incineration slag foam concrete

[0069]

[0070] As shown in Table 1, the compressive and flexural strengths of the Example 28 days were significantly improved compared to the Control Example. Furthermore, the setting time of the mortar obtained in the Example was significantly shortened compared to the Control Example, demonstrating that the combined addition of municipal solid waste incineration slag and waste diatomaceous earth significantly shortens the setting time, significantly outperforming the addition of municipal solid waste incineration slag alone. In particular, from Control Example 1 and Example 1, it can be seen that the use of pretreated waste diatomaceous earth significantly improves the mechanical properties and setting time of foamed concrete, indicating that pretreatment of diatomaceous earth with sodium hydroxide solution can enhance its activity. Compared to Example 2, Example 3 exhibits a longer ball milling time (i.e., a smaller slag particle size). This significantly improves the compressive and flexural strengths of Example 3, and also achieves a more pronounced shortening of the setting time. Combining the results of Example 1 and Control Example 3 reveals that the mesh size of municipal solid waste incineration slag is a key parameter influencing compressive strength, flexural strength, and setting time.

[0071] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A low-carbon, environmentally friendly, high-strength, fast-setting domestic waste incineration slag foam concrete, characterized in that: Its main components are cement, domestic waste incineration slag, foaming liquid, waste diatomaceous earth, sodium hydroxide, sodium sulfate, and water. The mass ratio of each component in foam concrete is: Ordinary Portland cement 105~230 Domestic waste incineration slag 250~400 Foaming liquid 15~25 Waste diatomaceous earth 60~100 Sodium hydroxide 60~100 Sodium sulfate 12~20 Water 100~200 The municipal solid waste incineration slag is obtained by sieving the bottom ash of the slag to remove the unburned waste, drying it at 100°C for 24 hours, and finally ball milling it into powder particles with a particle size of more than 200 mesh. The main chemical components of the slag are CaO, SiO2, and Al2O3, and the total content of the three is ≥75wt%; The waste diatomite has a mesh size range of 200-400 mesh, an amorphous SiO2 content of ≥70wt%, an organic matter content of ≤11wt%, a heavy metal content of <0.005wt%, and a moisture content of 10wt%-30wt%; The method for preparing the domestic waste incineration slag foam concrete comprises the following steps: (1) Measure each component material according to the above mass ratio; (2) Add the weighed solid sodium hydroxide to water and stir thoroughly to dissolve the solid sodium hydroxide completely in water. After the sodium hydroxide solution cools down, add the waste diatomaceous earth to the sodium hydroxide solution and stir it with a magnetic stirrer for 2 hours. After standing for half an hour, the pretreated diatomaceous earth solution is ready for use. (3) Add cement and domestic waste incineration slag into the mixing pot and stir for 1.5 minutes; (4) The pretreated diatomaceous earth solution and sodium sulfate were mixed evenly and then put into a stirring pot, and stirred together with cement and domestic waste incineration slag for 2 minutes to obtain a slurry; (5) Prepare foaming liquid: mix the foaming agent and water in a mass ratio of 1:30 and make foam through a foaming machine; (6) Add the foam to the slurry and stir slowly for 3 minutes until the foam is evenly dispersed in the slurry to obtain foamed concrete slurry; (7) The newly mixed foamed slurry is injection molded, and the mold is removed after 1 day. The slurry is placed in a standard curing room and cured to a specified age to obtain a finished product of domestic waste incineration slag foam concrete.

2. The domestic waste incineration slag foam concrete according to claim 1, characterized in that: The cement is P.O42.5 type ordinary Portland cement.

3. The domestic waste incineration slag foam concrete according to claim 1, characterized in that: The foaming liquid is prepared by diluting a composite protein foaming agent or an animal protein foaming agent by 30 times, and the foam prepared thereby needs to meet the following requirements: water secretion volume ≤ 15 ml in 1 hour, and sedimentation distance ≤ 5 mm in 1 hour.

4. The domestic waste incineration slag foam concrete according to claim 1, characterized in that: The sodium hydroxide is anhydrous sodium hydroxide with a purity of ≥99%.

5. The domestic waste incineration slag foam concrete according to claim 1, characterized in that: The sodium sulfate is anhydrous sodium sulfate with a purity of ≥99%.

6. The domestic waste incineration slag foam concrete according to claim 1, characterized in that: The water usage requirements described above comply with the requirements of the "Standard for Water Use in Concrete" (JGJ63-2006).

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