Method for using solidified mineralized garbage fines to make roadbed filling materials

Abstract

The invention discloses a method for solidifying mineralized garbage fines for making roadbed filling materials, which comprises the following steps: weighing 60-70 parts of mineralized garbage fines, 4-8 parts of slaked lime, 5-14 parts of cement, 2-5 parts of stabilizers, and 2-5 parts of modifiers, mixing and stirring evenly, and then adding 18-25 parts of water and stirring evenly to obtain roadbed filling materials. The method uses slaked lime to degrade organic components in mineralized garbage to ensure long-term performance, and accelerates cement hydration with stabilizers and modifiers to fill soil voids, solidifies mineralized garbage fines by stabilizing, reinforcing, and enhancing synergistic effects, significantly improves the mechanical performance index of roadbed filling material soil, and achieves the stability of heavy metals; and it uses mineralized garbage fines as roadbed filling materials, realizes landfill burden reduction and reduces pollution to surrounding soil and groundwater, achieves heavy metal stability, reduces material costs and transportation costs for adjacent road engineering construction, and can provide reference for resource utilization of soil with high organic matter content and heavy metal pollution.

Description

Technical Field

[0001] The invention belongs to the technical field of resource utilization of urban solid waste and the field of road engineering construction, and specifically relates to a method for preparing roadbed filling material by solidifying mineralized garbage fine materials. Background Art

[0002] Landfill has gradually become one of the main ways to deal with domestic waste in my country's cities. However, with the advancement of urbanization, informal domestic waste landfills originally located in the suburbs have occupied a large amount of land, and urban sanitary landfills have also reached the end of their service life and are seriously insufficient in storage capacity. In view of the problems of insufficient storage capacity and long-term land occupation in domestic waste landfills, excavation and separation of waste landfills are effective ways to reduce the pollution source load of landfills and utilize landfill waste as a resource. This can not only avoid pollution of the surrounding ecological environment, but also realize the redevelopment of land.

[0003] After screening, the landfill can obtain mineralized garbage fines, inorganic aggregates, lightweight materials and other components. The stock of mineralized garbage fines accounts for more than 60%, which directly affects the feasibility of landfill mining and the degree of reduction and resource utilization. In the existing technology, the following treatment methods are generally adopted for mineralized garbage fines: 1) The mineralized garbage fines are crushed and screened, and then compounded with clay mineral additives, construction waste, etc. in a certain proportion, and finally aged, dried, sintered and other processes to make hollow bricks, insulation bricks, hollow bricks and other products; 2) The pH and heavy metal content of mineralized garbage fines and clean soil are tested, and then the mineralized garbage fines are compounded with clean soil and the pH value, organic matter, hydrolyzable nitrogen, available phosphorus and quick-acting potassium are adjusted through the "soil testing and formula fertilization technology" to obtain planting soil, so as to realize the in-situ treatment of landfills and the resource utilization of mineralized garbage fines; 3) The mineralized garbage fines are mixed with bentonite in a disc granulator, and by adding atomized water and Atomized polyvinyl alcohol glue is made into a biofiller product with uniform particle size, high mechanical strength and good water resistance; 4) Microplastics in mineralized garbage fines are removed by fine screening, and the mixed stones and glass are crushed by grinding, and finally EM composite biological bacteria are added to obtain organic fertilizer, i.e. soil conditioner; 5) In view of the fact that the plastic on the screen is moist and difficult to be air-sorted, a system and method for the coordinated treatment of mineralized garbage fines and plastics in a cement kiln is provided, the collection efficiency of plastics is improved by throwing, and the heat released by the combustion of plastics is used as a heat source for thermal desorption of mineralized garbage fines; 6) Using the combustible material on the screen as the heat source, the mineralized garbage fines, crushed plastics and auxiliary materials are mixed into balls, and then dried, sintered and cooled to prepare expanded clay. However, the mineralized waste fines in the prior art are generally sandy soil, and heavy metals are concentrated in fine particles with a particle size of less than 2 mm, which is not conducive to resource utilization or has high processing costs; and the prior art mostly uses the mineralized waste fines directly or mixes them with other soils before use, without considering whether the heavy metals in the mineralized waste fines are stable in the long term. Summary of the invention

[0004] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, the main purpose of the present invention is to provide a method for solidifying mineralized garbage fines for making roadbed filling materials.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A method for solidifying mineralized garbage fines for making roadbed filling materials comprises the following steps:

[0007] 1) The method of obtaining mineralized waste fines is to mine, screen and landfill landfills that have reached a stable state for more than 10 years;

[0008] 2) Add slaked lime to the mineralized garbage fine material and simmer for 24 hours, then add the evenly mixed cement and stabilizer and stir evenly, finally add the modifier and water and stir evenly to obtain the roadbed filling material.

[0009] Preferably, the particle size of the mineralized waste fine material is less than / equal to 5 mm, and the organic matter content in the mineralized waste fine material is lower than 15%, further 14.7%, and the pH value is 7.1-7.8.

[0010] Preferably, the roadbed filling material comprises the following components in parts by weight: 60-70 parts of mineralized garbage fines, 4-8 parts of slaked lime, 5-14 parts of cement, 2-5 parts of stabilizer, 2-5 parts of modifier, and 18-25 parts of water.

[0011] In some specific embodiments, the roadbed filling material includes the following components in parts by weight: 60 parts of mineralized garbage fines, 8 parts of slaked lime, 5 parts of cement, 2 parts of stabilizer, 5 parts of modifier, and 18 parts of water.

[0012] In some specific embodiments, the roadbed filling material includes the following components in parts by weight: 65 parts of mineralized garbage fines, 6 parts of slaked lime, 10 parts of cement, 3 parts of stabilizer, 3 parts of modifier, and 22 parts of water.

[0013] In some specific embodiments, the roadbed filling material includes the following components in parts by weight: 70 parts of mineralized garbage fines, 4 parts of slaked lime, 14 parts of cement, 5 parts of stabilizer, 2 parts of modifier, and 25 parts of water.

[0014] Preferably, the cement is selected from at least one of composite silicate cement and ordinary silicate cement; further, the composite silicate cement is one of composite silicate cements with a strength grade of 32.5 or 42.5.

[0015] Preferably, the stabilizer is heat-modified attapulgite, and the heat-modified attapulgite is prepared by the following method: maintaining attapulgite with a mesh size of 400-600 mesh at a temperature of 500-600° C. for 2-4 hours, and then cooling to obtain the heat-modified attapulgite.

[0016] Preferably, the heavy metals in the mineralized waste fines include at least one of Hg, Sn, Be, V, Cr, Mn, Cu, Zn, As, Se, Cd, Sb, Ba and Pb.

[0017] Preferably, the dry density of the roadbed filling material is 1.55 g / cm 3 ~1.62g / cm 3 The unconfined compressive strength is 2.53-2.85Mpa, the cohesion is 7.82-8.28kpa, the internal friction angle is 14.32-15.64°, the bearing ratio is 75-82, and the compaction degree is greater than 94%.

[0018] Compared with the prior art, the present invention has at least the following advantages:

[0019] 1) The method for using solidified mineralized garbage fines to make roadbed filling materials provided by the present invention is the first to propose the use of mineralized garbage fines as roadbed filling materials; the method uses cement, slaked lime and stabilizer to synergistically solidify the mineralized garbage fines as roadbed filling materials, and the hydration products generated by cement hydration can enhance the strength of the soil of the mineralized garbage fines and can also bury some heavy metal pollutants; the addition of slaked lime can, on the one hand, create an alkaline environment to accelerate the degradation of organic matter and prevent it from affecting the long-term performance of the soil, and on the other hand, can synergize with cement to solidify the mineralized garbage fines, thereby improving the roadbed filling materials. Improve soil strength; stabilizer plays a "reinforcement" role in the soil, stabilizing heavy metals through adsorption, exchange and other means, so that heavy metals in mineralized garbage fines are almost not leached during use, and can also accelerate the cement hydration rate, further enhancing the strength of the soil; the addition of modifier is beneficial to improving the adhesion between soil particles, and can also construct an organic-inorganic interpenetrating network skeleton with the hydration products of cement, stabilizer and other substances, further improving the strength of roadbed filling materials, ensuring water stability, and reducing the leaching of harmful substances to make it meet environmental protection standards. The roadbed filling material prepared by the present application, through the coordinated cooperation of various raw materials, makes the maximum dry density, unconfined compressive strength, compaction degree, bearing ratio, cohesion, and internal friction angle of the roadbed filling material obtained by the application method significantly improved, meeting the requirements of the "Highway Roadbed Design Code" (JTG D30-2015); at the same time, the metal leaching amount of the roadbed filling material is low, and during the use of the roadbed filling material, due to the increase in pH, the embedding of heavy metals by cement hydration, and the organic-inorganic interpenetrating network skeleton, the leaching stability of heavy metals during use is effectively improved, and the heavy metal leaching amount can be kept low or no leaching for a long time, which meets the "Hazardous Waste Identification Standard-Leaching Toxicity Identification", "Groundwater Quality Standard" Class III standard limit, "Comprehensive Pollution Emission Standard" Class I pollutant maximum allowable emission concentration limit, "Surface Water Environmental Quality Standard" Class III limit requirements.

[0020] 2) The waste components in the mineralized waste fines are complex and can easily lead to discrete test results. The use of 5mm geosieve to process the mineralized waste fines can ensure the regularity of the test results on the one hand, and on the other hand, remove components such as plastics to improve the bonding between soil particles and increase soil strength.

[0021] 3) According to the application method provided by the present invention, the mineralized waste fines can be processed and reused without being compounded with other soils, thereby achieving 100% recycling of the mineralized waste fines. DETAILED DESCRIPTION

[0022] The present invention is further described in detail with reference to the following examples. The following examples are merely illustrative and not restrictive, and the protection scope of the present invention cannot be limited thereto.

[0023] When a certain amount, concentration or other value or parameter is expressed in the form of a range, a preferred range, or a preferred upper and lower numerical limit, it should be understood that it is equivalent to specifically revealing any range by combining any pair of upper range limits or preferred numerical values ​​with any lower range limit or preferred numerical value, regardless of whether the range is specifically disclosed. Unless otherwise indicated, the numerical range values ​​listed herein include the endpoints of the range, and all integers and fractions within the range.

[0024] Unless otherwise indicated, all percentages, parts, ratios, etc. herein are by weight.

[0025] The materials, methods, and examples herein are illustrative and are not to be construed as limiting unless specifically stated.

[0026] The test indexes and methods of the mineralized garbage fines used in the following examples are shown in Table 1:

[0027] Table 1 Test indicators and methods

[0028]

[0029]

[0030] 1) Determination of organic matter content and pH value

[0031] The organic matter content of the mineralized garbage fine material in the present application was measured by the loss on ignition method to be 14.7%, which did not meet the requirements of the "Greening Planting Soil" (20% to 80%), and was lower than the requirements of the "Organic Substrate for Greening" (≥25%). The pH of the mineralized garbage fine material was measured by the "Highway Geotechnical Test Regulations" acid-base test (water-soil ratio of 1:5) to be 7.51, which is weakly alkaline.

[0032] 2) Heavy metal content detection

[0033] The present application uses microwave digestion / atomic fluorescence spectrometry (HJ 702-2014) to determine the content of mercury in solid waste, and inductively coupled plasma mass spectrometry (HJ 766-2015) to determine the content of beryllium, vanadium, cadmium, chromium, manganese, nickel, copper, zinc, arsenic, selenium, antimony, barium and lead in the determination of metal elements in solid waste. The results are shown in Table 2:

[0034] Table 2. Results of the full amount of heavy metals detected in mineralized waste fines (mg kg -1 )

[0035]

[0036] Note: (VI) is Cr in the specification 6+ limit.

[0037] 3) Detection of metal leaching amount

[0038] The present application uses microwave digestion / atomic fluorescence spectrometry (HJ 702-2014) to determine the content of mercury in solid waste, and inductively coupled plasma mass spectrometry (HJ 766-2015) to determine the content of beryllium, vanadium, cadmium, chromium, manganese, nickel, copper, zinc, arsenic, selenium, antimony, barium and lead in the determination of metal elements in solid waste. The results are shown in Table 3:

[0039] Table 3 Leaching test results of heavy metals in mineralized garbage fines (mg·L -1 )

[0040]

[0041] Note: (VI) is Cr in the specification 6+ limit.

[0042] The stabilizer in the following embodiments is heat-modified attapulgite, which is prepared by the following method: maintaining attapulgite with a mesh size of 400-600 mesh at a temperature of 500-600° C. for 2-4 hours, and then cooling to obtain the heat-modified attapulgite.

[0043] In the following embodiments, the particle size of the mineralized waste fine material is less than / equal to 5 mm, the mineralized waste fine material is the mineralized waste fine material sieved by a 5 mm geosieve, and the organic matter content in the mineralized waste fine material is less than 15%, specifically 14.7%, and the pH value is 7.1-7.8.

[0044] Example 1

[0045] The method for preparing roadbed filling material by using solidified mineralized garbage fine material provided by the present invention comprises the following steps:

[0046] 1) The method of obtaining mineralized waste fines is to mine, screen and landfill landfills that have reached a stable state for more than 10 years;

[0047] 2) Add 8 parts by weight of slaked lime to the mineralized garbage fine material and simmer for 24 hours, then add the uniformly mixed cement and stabilizer and stir evenly, finally add the modifier and water and stir evenly to obtain the roadbed filling material.

[0048] 3) 5 parts by weight of composite silicate cement (42.5) and 2 parts by weight of stabilizer are mixed evenly, added into 60 parts by weight of mineralized garbage fine material and stirred evenly, and then 5 parts of modifier and 18 parts by weight of water are added and stirred evenly to obtain roadbed filling material.

[0049] Example 2

[0050] The method for preparing roadbed filling material by using solidified mineralized garbage fine material provided by the present invention comprises the following steps:

[0051] 1) The method of obtaining mineralized waste fines is to mine, screen and landfill landfills that have reached a stable state for more than 10 years;

[0052] 2) Add 6 parts by weight of slaked lime to the mineralized garbage fines and keep them for 24 hours, then add the mixed cement and stabilizer and stir them evenly, and finally add the modifier and water and stir them evenly to obtain the roadbed filling material;

[0053] 3) 10 parts by weight of composite silicate cement (42.5) and 3 parts by weight of stabilizer are mixed evenly, added into 65 parts by weight of mineralized garbage fine material and stirred evenly, and then 3 parts of modifier and 22 parts by weight of water are added and stirred evenly to obtain a roadbed filling material.

[0054] Example 3

[0055] The method for preparing roadbed filling material by using solidified mineralized garbage fine material provided by the present invention comprises the following steps:

[0056] 1) The method of obtaining mineralized waste fines is to mine, screen and landfill landfills that have reached a stable state for more than 10 years;

[0057] 2) Add 4 parts by weight of slaked lime to the mineralized garbage fines and keep them for 24 hours, then add the mixed cement and stabilizer and stir them evenly, and finally add the modifier and water and stir them evenly to obtain the roadbed filling material;

[0058] 3) 14 parts by weight of composite silicate cement (42.5) and 5 parts by weight of stabilizer are mixed evenly, added into 70 parts by weight of mineralized garbage fine material and stirred evenly, and then 2 parts of modifier and 25 parts by weight of water are added and stirred evenly to obtain a roadbed filling material.

[0059] Comparative Example 1:

[0060] The solidified mineralized garbage fine material provided in this comparative example 1 is used for the method of making roadbed filling material, and its components and proportions are basically the same as those in Example 2, except that the particle size of the mineralized garbage fine material is less than / equal to 30 mm; its application method is the same as that in Example 2.

[0061] Comparative Example 2

[0062] The method for using the solidified mineralized garbage fine material provided in this comparative example 2 to prepare roadbed filling material does not contain any stabilizer, and the remaining components and proportions are basically the same as those in Example 2; its application method is the same as that in Example 2.

[0063] Performance Testing:

[0064] 1. Indoor mechanical properties test:

[0065] In the present application, the roadbed filling materials prepared in Examples 1-3 and Comparative Example 1 were subjected to compaction tests, unconfined compressive strength tests, bearing ratio (CBR) tests, and triaxial compression tests according to the "Highway Geotechnical Test Code" (JTG 3430-2020) to obtain the maximum dry density, unconfined compressive strength, compaction degree, bearing ratio, total cohesion, total internal friction angle and other indicators to evaluate their mechanical properties. The results are shown in Table 4, specifically:

[0066] Table 4: Performance indicators of roadbed filling materials of Examples 1-3 and Comparative Example 1

[0067]

[0068]

[0069] As can be seen from Table 4, the roadbed filling material in Comparative Example 1 is inferior to those in the embodiment in all indicators because the mineralized garbage fines screened under the 30 mm geosieve have a large content of plastic components and the soil is loose and easy to collapse after compaction; while the unconfined compressive strength, compaction degree, bearing ratio, total cohesion and total internal friction angle of the roadbed filling material prepared by the application method provided in the present application are significantly improved, meeting the requirements of the "Highway Roadbed Design Code" (JTG D30-2015); pitting is observed on the cross section of the test piece after compaction, which is the result of the compaction of components such as stones mixed in the mineralized garbage fines to form a mechanical skeleton.

[0070] 2. Detection of metal leaching

[0071] The present application tests the metal leaching amount of the roadbed filling materials prepared in Examples 1-3 and Comparative Example 2, and adopts microwave digestion / atomic fluorescence spectrometry (HJ 702-2014) to determine the content of mercury in solid waste, and inductively coupled plasma mass spectrometry (HJ 766-2015) to determine the content of beryllium, vanadium, cadmium, chromium, manganese, nickel, copper, zinc, arsenic, selenium, antimony, barium and lead in solid waste. The test results are shown in Table 5:

[0072] Table 5: Performance indicators of roadbed filling materials of Examples 1-3 and Comparative Example 2 (mg·L -1 )

[0073]

[0074] Note: (VI) is Cr in the specification 6+ limit.

[0075] As can be seen from Table 5, the method for using solidified mineralized garbage fines provided in the present application to prepare roadbed filling materials has low metal leaching amount in the roadbed filling materials prepared by this method, and during use, due to the increase in pH, the embedding of heavy metals by cement hydration, and the stabilization of heavy metals by stabilizers, the heavy metals can be stabilized for a long time and will not be leached during use, thereby avoiding pollution to the surrounding soil or environment.

[0076] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A method for solidifying mineralized garbage fines for making roadbed filling materials, characterized in that: The steps include: 1) The method of obtaining mineralized waste fines is to mine, screen and landfill landfills that have reached a stable state for more than 10 years; 2) Add slaked lime to the mineralized garbage fines for 24 hours, then add the mixed cement and stabilizer and stir evenly, finally add the modifier and water and stir evenly to obtain the roadbed filling material; The roadbed filling material has the following components in parts by weight: 60-70 parts of mineralized garbage fines, 4-8 parts of slaked lime, 5-14 parts of cement, 2-5 parts of stabilizer, 2-5 parts of modifier, and 18-25 parts of water; The stabilizer is heat-modified attapulgite, which is prepared by the following method: maintaining attapulgite with a mesh size of 400-600 meshes at a temperature of 500-600° C. for 2-4 hours, and then cooling to obtain the heat-modified attapulgite.

2. The method for preparing roadbed filling material using solidified mineralized garbage fines according to claim 1, characterized in that: The particle size of the mineralized garbage fine material is less than / equal to 5 mm, the organic matter content of the mineralized garbage fine material is 14.7%, and the pH value is 7.1-7.

8.

3. The method for preparing roadbed filling material using solidified mineralized garbage fines according to claim 1, characterized in that: The roadbed filling material includes the following components by weight: 60 parts of mineralized garbage fines, 8 parts of slaked lime, 5 parts of cement, 2 parts of stabilizer, 5 parts of modifier, and 18 parts of water.

4. The method for preparing roadbed filling material using solidified mineralized garbage fines according to claim 1, characterized in that: The roadbed filling material includes the following components by weight: 65 parts of mineralized garbage fines, 6 parts of slaked lime, 10 parts of cement, 3 parts of stabilizer, 3 parts of modifier, and 22 parts of water.

5. The method for preparing roadbed filling material using solidified mineralized garbage fines according to claim 1, characterized in that: The roadbed filling material includes the following components by weight: 70 parts of mineralized garbage fines, 4 parts of slaked lime, 14 parts of cement, 5 parts of stabilizer, 2 parts of modifier, and 25 parts of water.

6. The method for preparing roadbed filling material using solidified mineralized garbage fines according to claim 1, characterized in that: The cement is selected from at least one of composite silicate cement and ordinary silicate cement.

7. The method for preparing roadbed filling material by using solidified mineralized garbage fines according to claim 6, characterized in that: The heavy metals in the mineralized waste fines include at least one of Hg, Sn, Be, V, Cr, Mn, Cu, Zn, As, Se, Cd, Sb, Ba and Pb.

8. The method for preparing roadbed filling material by using solidified mineralized garbage fines according to claim 1, characterized in that: The dry density of the roadbed filling material is 1.55 g / cm 3 ~1.62g / cm 3 The unconfined compressive strength is 2.53-2.85Mpa, the cohesion is 7.82-8.28kpa, the internal friction angle is 14.32-15.64°, the bearing ratio is 75-82%, and the compaction degree is greater than 96%.

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