Preparation method of water-quenched household garbage incineration ash and fine aggregate concrete thereof

Abstract

The application discloses a preparation method of water-quenched household garbage incineration ash and fine aggregate concrete, and belongs to the technical field of household garbage incineration ash and fine aggregate concrete. The preparation method of the water-quenched household garbage incineration ash comprises the following steps: placing molten-state household garbage incineration ash in a calcium hydroxide aqueous solution at room temperature to perform water-quenching and rapid cooling, taking out, drying, and obtaining water-quenched household garbage incineration ash; crushing the water-quenched household garbage incineration ash, screening out particles larger than 4.75 mm, and then performing grading screening to form continuous gradation to meet the sand standard of region II, so as to obtain water-quenched household garbage incineration ash precursors; and performing carbonization curing on the water-quenched household garbage incineration ash precursors in a closed environment to obtain water-quenched household garbage incineration ash, wherein the carbonization curing adopts carbon dioxide. The application improves the microstructure and potential activity of the household garbage incineration ash, so that the household garbage incineration ash can be applied to concrete as fine aggregate with stable performance.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization technology, specifically relating to a method for preparing water-quenched municipal solid waste incineration ash and its fine aggregate concrete. Background Technology

[0002] With the acceleration of urbanization, the amount of municipal solid waste generated is constantly increasing. Due to its advantages of volume reduction, harmlessness, and resource recovery, municipal solid waste incineration has become the main method of urban solid waste treatment. However, a large amount of incineration ash is generated during the waste incineration process. This ash usually contains inorganic components such as SiO2, Al2O3, and CaO, and may also contain heavy metals and soluble salts. If not handled properly, it can easily cause potential harm to the environment.

[0003] Currently, the main methods for treating municipal solid waste incineration ash include landfilling, stockpiling, and resource utilization. Among these, applying municipal solid waste incineration ash to building materials (such as as an admixture or fine aggregate in concrete) is considered a promising resource utilization approach. However, due to problems such as rough particle surfaces, loose and porous structure, high water absorption and crushing index values, and insufficient potential hydraulic activity, municipal solid waste incineration ash exhibits poor workability, decreased mechanical properties, and environmental safety hazards when used as fine aggregate in concrete, limiting its large-scale engineering application. Improving the performance of municipal solid waste incineration ash is the core key to overcoming its engineering application bottlenecks and achieving safe resource utilization.

[0004] Furthermore, given the increasing scarcity and limited mining of natural sand resources, developing artificial fine aggregates to replace natural sand has become an important development direction for the concrete industry. If municipal solid waste incineration ash can be properly treated and used as fine aggregate, it can not only realize the resource utilization of solid waste but also alleviate the shortage of natural sand resources, resulting in significant economic and environmental benefits.

[0005] Therefore, there is an urgent need to provide a treatment method that can improve the quality and potential hydraulic activity of municipal solid waste incineration ash, and further realize its application in concrete to replace natural sand, thereby achieving efficient and safe utilization of municipal solid waste incineration ash. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing water-quenched municipal solid waste incineration ash.

[0007] Another object of the present invention is to provide the use of the above-mentioned water-quenched municipal solid waste incineration ash in improving the frost resistance of concrete.

[0008] The objective of this invention is achieved through the following technical solution.

[0009] A method for preparing water-quenched municipal solid waste incineration ash, which is used to replace part of the natural sand in concrete containing natural sand, includes the following steps:

[0010] Step 1: The molten municipal solid waste incineration ash is placed in a room temperature calcium hydroxide aqueous solution for rapid water quenching, then removed and dried to obtain water-quenched municipal solid waste incineration ash. The concentration of Ca(OH)2 in the calcium hydroxide aqueous solution is 3-10 wt%.

[0011] In step 1, the ratio of calcium hydroxide aqueous solution to molten municipal solid waste incineration ash is (10~20):1 by mass.

[0012] In step 1, the water quenching time is 5~10 min.

[0013] In step 1, the method for obtaining molten municipal solid waste incineration ash includes: first holding the municipal solid waste incineration ash at 900~950℃ for 30~40min, and then holding it at 1350~1400℃ for 30~40min to obtain molten municipal solid waste incineration ash.

[0014] In the above technical solution, the particle size of the municipal solid waste incineration ash is <4.75mm. The municipal solid waste incineration ash includes CaO, SiO2, Al2O3 and Fe2O3, wherein the CaO content is 15~30wt%, the SiO2 content is 25~50wt%, the Al2O3 content is 5~15wt%, and the Fe2O3 content is 5~15wt%.

[0015] In step 1, the concentration of Ca(OH)2 in the calcium hydroxide aqueous solution is 5 wt%.

[0016] Step 2: Crush the water-quenched municipal solid waste incineration ash, screen out particles larger than 4.75mm, and then perform graded screening to form a continuous gradation that meets the Zone II sand standard, thus obtaining the water-quenched municipal solid waste incineration ash precursor.

[0017] In step 2, the particle size distribution of the water-quenched municipal solid waste incineration ash precursor is as follows: 0-25% by mass of particles with a diameter of 2.36 mm or larger, 10-50% by mass of particles with a diameter of 1.18 mm or larger, 41-70% by mass of particles with a diameter of 0.60 mm or larger, 70-92% by mass of particles with a diameter of 0.30 mm or larger, and 80-94% by mass of particles with a diameter of 0.15 mm or larger.

[0018] Step 3: The water-quenched municipal solid waste incineration ash precursor is carbonized and cured in a closed environment to obtain water-quenched municipal solid waste incineration ash. The carbonization and curing process uses carbon dioxide.

[0019] In step 3, carbonization curing is carried out in a carbonization curing chamber, where the volume fraction of carbon dioxide is 10% to 30% (preferably 20%).

[0020] In step 3, the carbonization curing temperature is 20~30℃, the relative humidity is 90~100%, and the carbonization curing time is 24~72h (preferably 48h).

[0021] In the above technical solution, the method for preparing concrete includes the following steps:

[0022] S1, mix water, cement, silica fume, natural sand, water-quenched municipal solid waste incineration ash obtained by the above preparation method, crushed stone and water-reducing agent until uniform to obtain concrete mixture. The ratio of water, cement, silica fume, natural sand, water-quenched municipal solid waste incineration ash, crushed stone and water-reducing agent by mass is (165~167):383:42:389:358:986:(3~5).

[0023] S2, the concrete mixture is poured into a test mold, covered with a film and left to stand for 24 hours, then demolded and cured to obtain concrete.

[0024] The use of water-quenched municipal solid waste incineration ash in improving the frost resistance of concrete.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. Water-quenched municipal solid waste incineration ash prepared by water quenching and carbonization curing with calcium hydroxide aqueous solution significantly reduced the crystallinity of the ash, increased the content of amorphous phases, and improved reactivity. This was achieved by introducing Ca(OH)₂ during the water quenching process, which... 2+ This invention participates in a non-equilibrium cooling reaction, forming a structure with potential hydraulic activity on the surface of water-quenched municipal solid waste incineration ash. Through carbonization curing, a dense carbonate structure is formed inside and on the surface of the ash, significantly reducing porosity and water absorption, and improving the crushing index of the water-quenched ash. The water-quenched municipal solid waste incineration ash prepared by this invention through water quenching with calcium hydroxide aqueous solution and carbonization curing has a water absorption rate reduced to 2.6% and a crushing index reduced to 18%, which is significantly better than untreated municipal solid waste incineration ash.

[0027] 2. The compressive strength and splitting tensile strength of the concrete prepared by replacing natural sand with water-quenched municipal solid waste incineration ash of the present invention are significantly improved compared with the concrete prepared by replacing natural sand with untreated municipal solid waste incineration ash, demonstrating good engineering applicability.

[0028] 3. The heavy metal leaching concentration is far below the national standard, meeting environmental safety requirements.

[0029] 4. When the water-quenched municipal solid waste incineration ash of the present invention partially replaces natural sand, the mass loss rate after 175 freeze-thaw cycles is only 0.97%, and the compressive strength after 175 freeze-thaw cycles is as high as 26.4 MPa.

[0030] In summary, this invention provides a method for preparing water-quenched municipal solid waste incineration ash, which improves the microstructure and potential activity of the ash, enabling it to be used as a stable fine aggregate in concrete. Attached Figure Description

[0031] Figure 1 SEM image of the untreated municipal solid waste incineration ash obtained in Comparative Example 1;

[0032] Figure 2 SEM image of the water-quenched municipal solid waste incineration ash obtained in Example 3;

[0033] Figure 3 SEM image of the water-quenched municipal solid waste incineration ash obtained in Example 1;

[0034] Figure 4 A confocal microscope image of the untreated municipal solid waste incineration ash obtained in Comparative Example 1;

[0035] Figure 5 This is a confocal microscope image of the water-quenched municipal solid waste incineration ash obtained in Example 1;

[0036] Figure 6 The XRD pattern of the untreated municipal solid waste incineration ash obtained in Comparative Example 1;

[0037] Figure 7 The image shows the XRD pattern of the water-quenched municipal solid waste incineration ash obtained in Example 1.

[0038] Figure 8 The image shows the concrete prepared in Example 6 after 0 freeze-thaw cycles.

[0039] Figure 9 Images of the concrete prepared in Example 6 after 100 freeze-thaw cycles;

[0040] Figure 10 The image shows the concrete prepared in Example 6 after 175 freeze-thaw cycles. Detailed Implementation

[0041] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0042] The ash from municipal solid waste incineration was taken from Jingcheng Solid Waste Disposal Co., Ltd. in Hohhot, Inner Mongolia (it is bottom ash produced at an incineration temperature of approximately 950℃). The ash comprises CaO, SiO2, Al2O3, and Fe2O3, with CaO content of 16.49 wt%, SiO2 content of 48.26 wt%, Al2O3 content of 8.89 wt%, Fe2O3 content of 4.60 wt%, and other oxides content of 21.76 wt%.

[0043] The natural sand comes from the Dahei River in Hohhot, and is naturally washed sand with a fineness modulus of 2.64, belonging to Zone II sand.

[0044] The particle size of the crushed stone is 5~20mm, and the bulk density of the crushed stone is 1310 kg / m³. 3 The apparent density is 2760 kg / m³. 3 The crushing index value is 9.9%, the moisture content is 0.3%, and the water absorption rate is 0.6%.

[0045] The cement is P·O 42.5 grade ordinary Portland cement produced by Inner Mongolia Jidong Cement Co., Ltd. The cement contains 64.00 wt% CaO, 23.44 wt% SiO2, 7.19 wt% Al2O3, 2.96 wt% Fe2O3, 1.00 wt% MnO, and 1.41 wt% other oxides.

[0046] The main component of silica fume is SiO2, of which SiO2 content is 91.92 wt%, CaO content is 0.42 wt%, Al2O3 content is 0.57 wt%, Fe2O3 content is 0.09 wt%, and other oxide content is 7.00%.

[0047] The water-reducing agent is a polycarboxylate superplasticizer with a density of 1.10 g / cm³. 3 The water reduction rate is 40%.

[0048] The temperature in the standard curing room is 18~22℃, and the relative humidity is >95%.

[0049] When conducting compressive strength tests, splitting tensile strength tests, and freeze-thaw cycle tests, three parallel specimens were made for each embodiment for the corresponding tests, and the average value of the test results was taken as the final result of that embodiment.

[0050] Example 1

[0051] A method for preparing water-quenched municipal solid waste incineration ash includes the following steps:

[0052] Step 1: The molten municipal solid waste incineration ash (at a temperature of approximately 1400℃) is placed in a calcium hydroxide aqueous solution (5wt% Ca(OH)₂ concentration) at room temperature (20-25℃) for rapid water quenching for 5 minutes. After removal, it is dried at room temperature for 24 hours, and then dried in an oven at 105℃ for 24 hours to obtain water-quenched municipal solid waste incineration ash. The ratio of calcium hydroxide aqueous solution to molten municipal solid waste incineration ash is 10:1 by mass. The method for incineration ash residue includes: screening the municipal solid waste incineration ash residue taken from Jingcheng Solid Waste Disposal Co., Ltd. in Hohhot, Inner Mongolia, to obtain municipal solid waste incineration ash residue with a particle size <4.75mm; first, holding the municipal solid waste incineration ash residue with a particle size <4.75mm at 900℃ for 30min (heating rate to 900℃ is 20℃ / min), and then holding it at 1400℃ for 30min (heating rate to 1400℃ is 5℃ / min) to completely melt the municipal solid waste incineration ash residue, thereby obtaining molten municipal solid waste incineration ash residue;

[0053] Step 2: Crush the water-quenched municipal solid waste incineration ash, screen out particles larger than 4.75mm, and then perform graded screening to form a continuous gradation that meets the Zone II sand standard, thus obtaining the water-quenched municipal solid waste incineration ash precursor. The particle size distribution of the water-quenched municipal solid waste incineration ash precursor is as follows: 21.3% by mass of particles with a diameter of 2.36mm and above, 42.1% by mass of particles with a diameter of 1.18mm and above, 52.7% by mass of particles with a diameter of 0.60mm and above, 74.9% by mass of particles with a diameter of 0.30mm and above, and 84.8% by mass of particles with a diameter of 0.15mm and above.

[0054] Step 3: The water-quenched municipal solid waste incineration ash precursor is carbonized and cured in a carbonization curing box (closed environment) with a carbon dioxide volume fraction of 20% for 48 hours to obtain water-quenched municipal solid waste incineration ash. The carbonization curing temperature is 25±5℃ and the relative humidity is 95±5%.

[0055] Example 2 (as a comparison)

[0056] A method for preparing water-quenched municipal solid waste incineration ash is basically the same as that in Example 1, except that step 3, carbonization curing, is not performed.

[0057] Example 3 (as a comparison)

[0058] A method for preparing water-quenched municipal solid waste incineration ash is basically the same as that in Example 1, except that "calcium hydroxide aqueous solution" is replaced with "water".

[0059] Example 4 (as a comparison)

[0060] A method for preparing water-quenched municipal solid waste incineration ash includes the following steps:

[0061] Step 1 is basically the same as Step 1 in Example 1, except that "calcium hydroxide aqueous solution" is replaced with "water".

[0062] Step 2: The water-quenched municipal solid waste incineration ash obtained in Step 1 of Example 4 is crushed, and particles larger than 4.75mm are screened out. Then, it is graded and screened to form a continuous gradation that meets the Zone II sand standard, thus obtaining the water-quenched municipal solid waste incineration ash precursor. The water-quenched municipal solid waste incineration ash precursor is directly used as the water-quenched municipal solid waste incineration ash (i.e., no carbonization curing was performed in Example 4). The particle size distribution of the water-quenched municipal solid waste incineration ash precursor is as follows: particles with a diameter of 2.36mm and above account for 21.3% of the mass, particles with a diameter of 1.18mm and above account for 42.1% of the mass, particles with a diameter of 0.60mm and above account for 52.7% of the mass, particles with a diameter of 0.30mm and above account for 74.9% of the mass, and particles with a diameter of 0.15mm and above account for 84.8% of the mass.

[0063] Comparative Example 1

[0064] An untreated municipal solid waste incineration ash residue is obtained by screening municipal solid waste incineration ash residue taken from Jingcheng Solid Waste Disposal Co., Ltd. in Hohhot, Inner Mongolia, to obtain municipal solid waste incineration ash residue with a particle size of <4.75mm, i.e., untreated municipal solid waste incineration ash residue.

[0065] According to the "Construction Sand" (GB / T 14684-2022), the water absorption rate and crushing index of the untreated municipal solid waste incineration ash obtained from Comparative Example 1 and the water-quenched municipal solid waste incineration ash obtained from Examples 1 to 4 were tested. The water absorption rate and crushing index values ​​were obtained, and the test results are shown in Table 1.

[0066] Table 1

[0067]

[0068] Table 1 shows that the untreated municipal solid waste incineration ash obtained in Comparative Example 1 had a water absorption rate of 10.4% and a crushing index value of 57%, exhibiting high water absorption and crushing index values. The water-quenched municipal solid waste incineration ash obtained in Example 4 (water quenching) had a water absorption rate of 7.7% and a crushing index value of 39%, indicating that water quenching can reduce both water absorption and crushing index values. The water-quenched municipal solid waste incineration ash obtained in Example 2 (calcium hydroxide aqueous solution quenching) had a water absorption rate of 6.0% and a crushing index value of 31%, indicating that the Ca in the calcium hydroxide aqueous solution... 2+The water-quenched ash reacted with SiO2 and Al2O3 in the municipal solid waste incineration ash, improving its density. Example 3 (water quenching + carbonation curing) yielded a water absorption rate of 4.3% and a crushing index of 25%. The performance of the water-quenched ash prepared in Example 3 was improved compared to Example 4, indicating that carbonation curing caused the water-quenched ash to react with CO2, forming a dense carbonate structure, thereby reducing porosity and improving performance. Example 1 yielded a water absorption rate of only 2.6% and a crushing index reduced to 18%, significantly better than Examples 2-4. This shows that water quenching with calcium hydroxide aqueous solution and carbonation curing have a synergistic effect, significantly improving the pore structure, density, and crushing resistance of the municipal solid waste incineration ash.

[0069] SEM images of the untreated municipal solid waste incineration ash obtained in Comparative Example 1 are shown below. Figure 1 As shown, the SEM image of the water-quenched municipal solid waste incineration ash obtained in Example 3 is as follows. Figure 2 As shown, the SEM image of the water-quenched municipal solid waste incineration ash obtained in Example 1 is as follows. Figure 3 As shown. By Figure 1 It can be seen that the ash from untreated municipal solid waste incineration has many pores and a relatively loose texture. Figure 2 It can be seen that, due to the violent melting reaction, most of the water-quenched municipal solid waste incineration ash prepared in Example 3 underwent crystallization and sintering, resulting in a reduction in the number of surface pores and the appearance of numerous overlapping, interwoven flakes. The surface of these flakes also had numerous small particles (unmelted material) attached to it. Figure 3 It can be seen that the surface of the water-quenched municipal solid waste incineration ash prepared in Example 1 is significantly denser, the number of pores is significantly reduced, and there are fewer small particles (small particles are unmelted and unreacted substances) attached to the surface.

[0070] Confocal microscopy image of the untreated municipal solid waste incineration ash obtained in Comparative Example 1 is shown below. Figure 4 As shown, a confocal microscope image of the water-quenched municipal solid waste incineration ash obtained in Example 1 is shown below. Figure 5 As shown. By Figure 4 and Figure 5 It can be seen that the untreated municipal solid waste incineration ash obtained in Comparative Example 1 is grayish-yellow, irregular in shape, with an uneven surface and obvious edges. The water-quenched municipal solid waste incineration ash obtained in Example 1 is relatively dense, with a smooth and flat surface, no obvious pores, and exhibits a distinct vitreous luster.

[0071] The XRD pattern of the untreated municipal solid waste incineration ash obtained in Comparative Example 1 is shown in Figure 1. Figure 6As shown, the XRD pattern of the water-quenched municipal solid waste incineration ash obtained in Example 1 is as follows. Figure 7 As shown. By Figure 6 It can be seen that the main phases in the untreated municipal solid waste incineration ash obtained in Comparative Example 1 are CaCO3, SiO2, CaSO4, and CaSiO3. The Rietveld full-spectrum refinement method was used to refine the ash. Figure 6 Quantitative phase analysis revealed that CaCO3 accounted for 26.5 wt%, SiO2 for 16.9 wt%, CaSO4 for 11.4 wt%, and CaSiO3 for 41.5 wt%. Figure 7 It can be seen that the main phases of the water-quenched municipal solid waste incineration ash obtained in Example 1 are dolomite (CaMg(CO3)2) and SiO2. The Rietveld full-spectrum refinement method was used to refine the ash. Figure 7 Quantitative phase analysis revealed that dolomite accounted for 32.03 wt% and SiO2 accounted for 67.7 wt%.

[0072] XRD peak fitting method was used to... Figure 6 and Figure 7 Perform crystallinity calculations based on Figure 6 The crystallinity of the untreated municipal solid waste incineration ash obtained in Comparative Example 1 was calculated to be 67.69%. Figure 7 The crystallinity of the water-quenched municipal solid waste incineration ash prepared in Example 1 was calculated to be 19.85%. The crystallinity of the water-quenched municipal solid waste incineration ash prepared in Example 1 was significantly lower than that of the municipal solid waste incineration ash in Comparative Example 1 (that is, the amorphous phase content of the water-quenched municipal solid waste incineration ash prepared in Example 1 was higher than that of Comparative Example 1, which improved the reactivity).

[0073] According to the "Leaching Toxicity of Solid Waste - Sulfuric Acid and Nitric Acid Method" (HJ / T 299-2007), the leaching test of toxic substances was carried out on the water-quenched municipal solid waste incineration ash obtained in Example 1, and the test results were judged with reference to the "Identification Standard for Hazardous Waste - Leaching Toxicity Identification" (GB 5085.3-2007). The test results are shown in Table 2.

[0074] Table 2

[0075]

[0076] As shown in Table 2, the leaching concentration of toxic substances in the water-quenched municipal solid waste incineration ash prepared in Example 1 is far lower than the national standard.

[0077] Examples 5-9 (Partial replacement of natural sand with municipal solid waste incineration ash, with a volume replacement rate of 50%)

[0078] A method for preparing concrete includes the following steps:

[0079] S1, water, cement, silica fume, natural sand, municipal solid waste incineration ash, crushed stone, and water-reducing agent are mixed until homogeneous to obtain a concrete mixture. The ratio of water, cement, silica fume, natural sand, municipal solid waste incineration ash, crushed stone, and water-reducing agent by mass is 167:383:42:389:358:986:3. The municipal solid waste incineration ash is one of the untreated municipal solid waste incineration ash from Comparative Example 1 and the water-quenched municipal solid waste incineration ash prepared in Examples 1-4. The mixing of water, cement, silica fume, natural sand, municipal solid waste incineration ash, crushed stone, and water-reducing agent until homogeneous specifically includes: adding cement, silica fume, municipal solid waste incineration ash, and natural sand sequentially to a mixer and mixing (dry mixing) for 30 seconds until homogeneous; adding water and water-reducing agent and mixing for 60 seconds until homogeneous (forming a slurry); adding crushed stone and mixing for 60 seconds until homogeneous to obtain the concrete mixture.

[0080] S2, the concrete mixture is poured into a test mold (the concrete mixture is poured in two batches, with the same volume for each batch; after each batch, it is vibrated on a vibrating table for 30 seconds and the surface is smoothed), covered with a film (to reduce moisture evaporation), and left to stand indoors at a temperature of 20℃±5℃ and a relative humidity of 55±5% for 24 hours. The mold is then removed, and the concrete is cured in a standard curing room for D days to obtain the final concrete. D days can be any of 7 days, 28 days, or 180 days.

[0081] Table 3

[0082]

[0083] Examples 10-14 (Complete replacement of natural sand with ash from municipal solid waste incineration)

[0084] A method for preparing concrete includes the following steps:

[0085] S1, water, cement, silica fume, municipal solid waste incineration ash, crushed stone, and water-reducing agent are mixed until homogeneous to obtain a concrete mixture. The ratio of water, cement, silica fume, municipal solid waste incineration ash, crushed stone, and water-reducing agent by mass is 165:383:42:716:986:5. The municipal solid waste incineration ash is one of the untreated municipal solid waste incineration ash from Comparative Example 1 and the water-quenched municipal solid waste incineration ash prepared in Examples 1-4. The mixing of water, cement, silica fume, municipal solid waste incineration ash, crushed stone, and water-reducing agent until homogeneous specifically includes: sequentially adding cement, silica fume, and municipal solid waste incineration ash to a mixer and mixing (dry mixing) for 30 seconds until homogeneous; adding water and water-reducing agent and mixing for 60 seconds until homogeneous (forming a slurry); adding crushed stone and mixing for 60 seconds until homogeneous to obtain the concrete mixture.

[0086] S2, the concrete mixture is poured into a test mold (the concrete mixture is poured in two batches, with the same volume for each batch; after each batch, it is vibrated on a vibrating table for 30 seconds and the surface is smoothed), covered with a film (to reduce moisture evaporation), and left to stand indoors at a temperature of 20℃±5℃ and a relative humidity of 55±5% for 24 hours. The mold is then removed, and the concrete is cured in a standard curing room for D days to obtain the final concrete. D days can be any of 7 days, 28 days, or 180 days.

[0087] Table 4

[0088]

[0089] According to the "Standard for Test Methods of Physical and Mechanical Properties of Concrete" (GB / T 50081-2019), the compressive strength and splitting tensile strength of concrete cured for D days were tested, and the test results are shown in Table 5. The concrete used is one of the concretes in Examples 5 to 14.

[0090] Table 5

[0091]

[0092] As shown in Table 5, compared with Example 5, the compressive strength and splitting tensile strength of the concrete prepared in Examples 6-9 were higher than those in Example 5. At D=7, compared with Example 5, the compressive strength of the concrete prepared in Examples 6-9 increased by 51.9%, 28.7%, 33.8%, and 20.7%, respectively. At D=28, compared with Example 5, the compressive strength of the concrete prepared in Examples 6-9 increased by 52.8%, 22.7%, 29.8%, and 14.9%, respectively. At D=180, compared with Example 5, the compressive strength of the concrete prepared in Examples 6-9 increased by 43.9%, 17.8%, 22.6%, and 15.1%, respectively. It can be seen that at each curing time, the concrete prepared in Example 6 had the highest compressive strength and splitting tensile strength.

[0093] At D=7, the compressive strength of the concrete prepared in Example 7 was 1.9 MPa higher than that in Example 9, meaning that water quenching with calcium hydroxide aqueous solution alone could only increase its compressive strength by 1.9 MPa. The compressive strength of the concrete prepared in Example 8 was 3.1 MPa higher than that in Example 9, meaning that carbonation curing alone could only increase its compressive strength by 3.1 MPa. The compressive strength of the concrete prepared in Example 6 was 7.4 MPa higher than that in Example 9. This indicates that water quenching with calcium hydroxide aqueous solution and carbonation curing can synergistically improve the compressive strength of concrete. At D=7, the splitting tensile strength of the concrete prepared in Example 7 was 0.01 MPa higher than that in Example 9; the splitting tensile strength of the concrete prepared in Example 8 was 0.09 MPa higher than that in Example 9; and the splitting tensile strength of the concrete prepared in Example 6 was 0.43 MPa higher than that in Example 9. At D=28, the splitting tensile strength of the concrete prepared in Example 6 was again the highest compared to that in Example 9. At D=180, the splitting tensile strength of the concrete prepared in Example 7 decreased by 0.24 MPa compared to Example 9; the splitting tensile strength of the concrete prepared in Example 8 decreased by 0.12 MPa compared to Example 9; and the splitting tensile strength of the concrete prepared in Example 6 increased by 0.66 MPa compared to Example 9. This indicates that water quenching with calcium hydroxide aqueous solution alone and carbonation curing alone have limited or even negative effects on improving the splitting tensile strength of concrete, while water quenching with calcium hydroxide aqueous solution and carbonation curing can synergistically improve the splitting tensile strength of concrete. Comparing Examples 11 and 14, Examples 12 and 14, and Examples 13 and 14 yields the same conclusion: water quenching with calcium hydroxide aqueous solution and carbonation curing can synergistically improve the compressive strength and splitting tensile strength of concrete.

[0094] The untreated municipal solid waste incineration ash in Comparative Example 1, due to its high water absorption, large crushing index, and numerous pores, resulted in concrete with low mechanical properties. The preparation method in Example 1, through the synergistic effect of water quenching with calcium hydroxide aqueous solution and carbonation curing, made the surface of the water-quenched municipal solid waste incineration ash denser, significantly reduced its crystallinity, and further enhanced its potential activity. Therefore, the concrete prepared from the water-quenched municipal solid waste incineration ash of Example 1 exhibited the best mechanical properties. This demonstrates that the present invention, through the synergistic modification of water quenching with calcium hydroxide aqueous solution and carbonation curing, enables the water-quenched municipal solid waste incineration ash to maintain the mechanical properties of concrete while replacing a high proportion of natural sand, thus meeting the requirements of high sand substitution engineering applications.

[0095] According to the rapid freeze-thaw method in the "Standard for Test Methods of Long-Term Performance and Durability of Concrete" (GB / T 50082-2024), freeze-thaw cycle tests were conducted on concrete cured for 28 days. The mass loss rate of the concrete under different freeze-thaw cycle numbers was tested according to the same standard. The compressive strength of the concrete under different freeze-thaw cycle numbers was tested according to the "Standard for Test Methods of Physical and Mechanical Properties of Concrete" (GB / T 50081-2019). The mass loss rate under different freeze-thaw cycle numbers is shown in Table 6, and the compressive strength under different freeze-thaw cycle numbers is shown in Table 7. The concrete used was one of the concretes prepared in Examples 5-14. Images of the concrete prepared in Example 6 after 0, 100, and 175 freeze-thaw cycles are shown in the following figures. Figures 8-10 As shown, by Figures 8-10 It can be seen that the concrete prepared in Example 6 still maintains its intact structure after 175 freeze-thaw cycles.

[0096] Table 6 (In Table 6, "—" indicates that the specimen has met the conditions for stopping the freeze-thaw cycle test, and the test was stopped early)

[0097]

[0098] Table 7 (In Table 7, "—" indicates that the specimen failed during the freeze-thaw cycle test and no longer met the integrity requirements, so its compressive strength value was not measured)

[0099]

[0100] As shown in Tables 6 and 7, in Examples 5-14, the mass loss rate of concrete gradually increased with the increase of the number of freeze-thaw cycles, while the compressive strength showed a gradual decreasing trend. Although the mass loss rate of the concrete prepared in Examples 7 and 8 was lower than that in Example 9, it was still impossible to conduct more freeze-thaw cycle tests. That is, water quenching with calcium hydroxide aqueous solution alone and carbonation curing alone did not significantly improve the mass loss rate of concrete's freeze-thaw resistance. However, the concrete prepared in Example 6 (prepared using water-quenched municipal solid waste incineration ash from Example 1) did not suffer damage after 175 freeze-thaw cycles, and its mass loss rate was always controlled at a low level, which again confirmed the synergistic effect of water quenching with calcium hydroxide aqueous solution and carbonation curing. After 75 freeze-thaw cycles, the compressive strength of the concrete prepared in Example 7 was 1.4 MPa higher than that in Example 9, meaning that water quenching with calcium hydroxide solution alone only increased its compressive strength by 1.4 MPa. The compressive strength of the concrete prepared in Example 8 was 5.1 MPa higher than that in Example 9, meaning that carbonation curing alone only increased its compressive strength by 5.1 MPa. The compressive strength of the concrete prepared in Example 6 was 12.9 MPa higher than that in Example 9, meaning that water quenching with calcium hydroxide solution and carbonation curing worked synergistically to increase the compressive strength by 12.9 MPa. After 75 freeze-thaw cycles, the compressive strength of the concrete prepared in Example 12 was 1.9 MPa higher than that in Example 14; the compressive strength of the concrete prepared in Example 13 was 2.9 MPa higher than that in Example 14; the compressive strength of the concrete prepared in Example 11 was 4.4 MPa higher than that in Example 14. When water-quenched municipal solid waste incineration ash completely replaced natural sand, the synergistic effect of water quenching with calcium hydroxide solution and carbonation curing was not significant. In summary, when water-quenched municipal solid waste incineration ash partially replaces natural sand, it significantly improves the freeze-thaw resistance of concrete. When it partially replaces natural sand, natural sand and water-quenched municipal solid waste incineration ash play the roles of "structural support" and "activity enhancement" respectively, forming a synergistic effect.

[0101] Further analysis revealed that the compressive strength of the concrete prepared in Example 6 decreased from 43.1 MPa to 26.4 MPa during 0-175 freeze-thaw cycles, exhibiting a relatively low compressive strength loss rate (approximately 38.7%). In contrast, the concrete prepared in Example 5 showed a rapid decrease in compressive strength and even failure after experiencing fewer freeze-thaw cycles. These results demonstrate that the synergistic effect of water quenching with calcium hydroxide aqueous solution and carbonation curing in this invention can significantly optimize the pore structure of municipal solid waste incineration ash, reducing its porosity and the proportion of interconnected pores, thereby effectively inhibiting the propagation of internal microcracks caused by moisture migration and freeze expansion during freeze-thaw cycles.

[0102] In summary, this invention, through the synergistic effect of water quenching and carbonization curing with calcium hydroxide aqueous solution, not only improves the aggregate quality of municipal solid waste incineration ash but also significantly enhances its engineering applicability as fine aggregate in concrete.

[0103] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing water-quenched municipal solid waste incineration ash, characterized in that, Water-quenched municipal solid waste incineration ash is used to replace part of the natural sand in concrete containing natural sand. The preparation method of water-quenched municipal solid waste incineration ash includes the following steps: Step 1: The molten municipal solid waste incineration ash is placed in a room temperature calcium hydroxide aqueous solution for rapid water quenching, then removed and dried to obtain water-quenched municipal solid waste incineration ash. The concentration of Ca(OH)2 in the calcium hydroxide aqueous solution is 3-10 wt%. Step 2: Crush the water-quenched municipal solid waste incineration ash, screen out particles larger than 4.75mm, and then perform graded screening to form a continuous gradation that meets the Zone II sand standard, thus obtaining the water-quenched municipal solid waste incineration ash precursor. Step 3: The water-quenched municipal solid waste incineration ash precursor is carbonized and cured in a closed environment to obtain water-quenched municipal solid waste incineration ash. The carbonization and curing process uses carbon dioxide.

2. The preparation method according to claim 1, characterized in that, In step 1, the water quenching time is 5~10 minutes.

3. The preparation method according to claim 1, characterized in that, In step 1, the ratio of calcium hydroxide aqueous solution to molten municipal solid waste incineration ash is (10~20):1 by mass.

4. The preparation method according to claim 1, characterized in that, In step 2, the particle size distribution of the water-quenched municipal solid waste incineration ash precursor is as follows: 0-25% by mass of particles with a diameter of 2.36 mm or larger, 10-50% by mass of particles with a diameter of 1.18 mm or larger, 41-70% by mass of particles with a diameter of 0.60 mm or larger, 70-92% by mass of particles with a diameter of 0.30 mm or larger, and 80-94% by mass of particles with a diameter of 0.15 mm or larger.

5. The preparation method according to claim 1, characterized in that, In step 3, carbonization curing is carried out in a carbonization curing chamber with a carbon dioxide volume fraction of 10% to 30%; the carbonization curing temperature is 20 to 30°C, the relative humidity is 90 to 100%, and the carbonization curing time is 24 to 72 hours.

6. The preparation method according to claim 1, characterized in that, The particle size of the ash residue from municipal solid waste incineration is <4.75mm. The ash residue from municipal solid waste incineration includes CaO, SiO2, Al2O3 and Fe2O3, of which the content of CaO is 15~30wt%, the content of SiO2 is 25~50wt%, the content of Al2O3 is 5~15wt%, and the content of Fe2O3 is 5~15wt%.

7. The preparation method according to claim 1, characterized in that, The method for preparing concrete includes the following steps: S1, water, cement, silica fume, natural sand, water-quenched municipal solid waste incineration ash obtained by the preparation method as described in claim 1, crushed stone and water-reducing agent are mixed until uniform to obtain concrete mixture. The ratio of water, cement, silica fume, natural sand, water-quenched municipal solid waste incineration ash, crushed stone and water-reducing agent by mass is (165~167):383:42:389:358:986:(3~5). S2, the concrete mixture is poured into a test mold, covered with a film and left to stand, then demolded and cured to obtain concrete.

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