Roadbed stabilizing material using inorganic solid waste as raw material and preparation method thereof

Abstract

The application belongs to the technical field of road engineering materials, and particularly relates to a subgrade stabilizing material taking inorganic solid waste as raw material and a preparation method thereof, which comprises the following steps: preparing a composite drying agent: acrylic cross-linking is used to obtain gel blocks, which are stirred and broken together with heavy metal tailing powder, and after drying, the gel blocks are crushed to obtain the composite drying agent; preparing A material: after the flotation metal tailing is thickened, the pH is adjusted, PAM is added, and the composite drying agent is stirred and uniformly dehydrated to obtain the A material; preparing B material: the B material is prepared by using steel slag powder, diammonium hydrogen phosphate and slag powder curing agent; and preparing a finished product: the A material and the B material are mixed, and water is added to prepare the subgrade stabilizing material taking inorganic solid waste as raw material. Based on the characteristics of the metal tailings prepared by different processes and in combination with the process, good dispersion of the polyacrylic superabsorbent resin is realized, and the subgrade stabilizing material with low energy consumption and high stability is obtained.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of road engineering materials, and in particular relates to a subgrade stabilizing material using inorganic solid waste as raw material and a preparation method thereof. BACKGROUND

[0002] Using solid waste materials and inorganic cementing materials to replace clay as subgrade materials is a method of realizing resource recycling and reducing costs, but common solid waste materials such as metal tailings, especially flotation metal tailings, have fine particle sizes and need to consume a large amount of energy for drying. In addition, the composition of the solid waste materials is complex, and the residual sulfur and chlorine elements will slowly affect the overall performance through corrosion and other effects, and the dispersibility between the solid waste materials and the inorganic cementing materials will cause serious cracking of the subgrade, so there are still certain difficulties in the actual low-cost application.

[0003] CN108083667B discloses a subgrade filler, which provides a subgrade filler using alkali residue and lignosulfonate as main components. The lignosulfonate is used as a dispersant to improve the mixing uniformity of the alkali residue and reduce the water content, thereby improving the construction efficiency and compaction effect. However, the alkali residue composition used in this technical solution is single, and the compatibility and synergistic effect between different types of solid waste materials are not fully considered, which may lead to insufficient durability and crack resistance of the subgrade filler in complex environments.

[0004] CN107056157B discloses a subgrade filling material, which proposes a subgrade filling material using Xigeda soil and vanadium-titanium tailings as main components. The combination of the two improves the strength and bearing capacity of the filler, and realizes effective utilization of waste resources. However, the particle size, pH value and harmful element content of the vanadium-titanium tailings are not explicitly defined in this technical solution, which may lead to inconsistent performance of the subgrade due to large differences in raw materials in actual application. In addition, although the problem of Xigeda soil disintegration when exposed to water is alleviated to some extent by adding vanadium-titanium tailings, the risk of cracking caused by water retention is not fundamentally solved, and the optimization design of the microporous structure is not involved, which makes it difficult to meet the high requirements for subgrade stability under complex working conditions.

[0005] As can be seen from the above, there are also few solutions to the problem of large energy consumption for drying solid waste materials in the prior art. The use of wet solid waste materials in the background of the prior art will lead to inaccurate batching, unstable performance, and cracking problems. SUMMARY

[0006] Therefore, the present application provides a subgrade stabilizing material using inorganic solid waste as raw material and a preparation method thereof. Based on the characteristics of metal tailings prepared by different processes and combined with the process, good dispersion of polyacrylic acid superabsorbent resin is achieved, and a subgrade stabilizing material with low energy consumption and high stability is obtained.

[0007] To solve the above problems, the present application mainly provides the following technical solutions:

[0008] In one aspect, the present application provides a preparation method of subgrade stabilizer using inorganic solid waste as raw material, including the following steps:

[0009] including the following steps:

[0010] (1) Preparation of gel block: 100 parts of acrylic acid are added to 80-100 parts of water, stirred uniformly, and then 0.5-0.8 parts of initiator is added, and reacted at 60-65℃ for 1.5-2.5h, 1-3 parts of crosslinking agent is added, and the reaction is continued at 60-65℃ for 1.5-2.5h, to obtain a gel block of polyacrylic acid superabsorbent resin;

[0011] (2) Preparation of composite desiccant: 50-150 mesh heavy metal tailings powder is added to the gel block and stirred, crushed, dried, and further crushed to obtain a composite desiccant; wherein the mass ratio of the gel block to the heavy metal tailings powder is 1:30-40, and the composite desiccant has a water content of less than 0.5% and an average particle size of 10-20μm;

[0012] (3) Preparation of slurry: the flotation metal tailings are treated by slurry, to obtain a slurry; the solid mass fraction in the slurry is 10-15%, and the pH value is 8-10;

[0013] (4) Preparation of filter cake: 0.1-0.3ppm PAM is added to the slurry for dewatering treatment, to obtain a filter cake with a water content of 12-18%;

[0014] (5) Preparation of A material: under stirring conditions, the filter cake and the composite desiccant are mixed in a mass ratio of 1:1-1.2, and then densified, placed, and dispersed to obtain A material;

[0015] (6) Preparation of B material: 10-20 parts of steel slag powder, 0.3-1 parts of diammonium hydrogen phosphate, and 5-10 parts of slag powder curing agent are dry ball milled and densified to obtain B material;

[0016] (7) Preparation of subgrade stabilizer: 30-50 parts of A material and 30-50 parts of B material are mixed, 8-15 parts of water is added, and stirred uniformly to obtain a subgrade stabilizer.

[0017] The radical polymerization and cross-linking reaction of the acrylic monomer in step (1) generates a three-dimensional network polyacrylic acid superabsorbent resin gel, which realizes efficient water absorption through ionization of the carboxyl groups on the molecular chain and ion osmotic pressure effect; subsequently in step (2), the introduction of the heavy metal tailings powder not only solves the engineering problem of difficult drying and crushing of the gel, but also inhibits the excessive swelling of the gel after water absorption through the supporting effect of the rigid inorganic particles of the heavy metal tailings powder, thereby enhancing the dimensional stability of the gel in the subsequent solidified body, and also enables the polyacrylic acid superabsorbent resin gel block to be uniformly dispersed in the roadbed material.

[0018] In step (3), the flotation metal tailings are treated with slurry and the pH is adjusted, aiming to create an alkaline precipitation environment for the metal ions on the surface of the tailings; in step (4), anionic PAM is added to capture fine particles and free ions through bridging flocculation, forming a pretreated filter cake; in step (5), the mixing and densification with the composite desiccant is a key interface engineering process, which enables the composite desiccant particles to be uniformly embedded in the microstructure of the tailings filter cake, and initially forms a prefabricated composite with the tailings as the skeleton and the reversible water absorption unit contained therein, i.e. A material.

[0019] In step (6), the steel slag powder and the slag powder have increased particle surface energy and increased lattice defects under the mechanical force activation of ball milling, and together with the phosphate ions provided by the diammonium hydrogen phosphate, they form a potential alkaline activation and solidification system (B material).

[0020] Finally, in step (7), A material and B material are mixed, and during the stirring process, the hydration activity of the B material steel slag powder reacts with the free calcium oxide in the steel slag powder to promote the formation of hydrated gel products of the steel slag powder, and the specific reaction is:

[0021] PO4 3- + CaO → CaHPO4

[0022] SiO2 + Ca(OH)2 → CaSiO3

[0023] The composite desiccant dispersed in the A material beforehand absorbs excess mixing water to reduce bleeding and promote hydration, and in the later environment, it adjusts the humidity inside the roadbed by absorbing and releasing water, thereby inhibiting the generation of dry shrinkage cracks. Finally, the polyacrylic acid superabsorbent resin is uniformly dispersed in the roadbed material to form a stable composite whole, thereby meeting the comprehensive requirements of roadbed materials for strength, durability and environmental adaptability.

[0024] As a preferred, in the step (1), the initiator is ammonium persulfate, and the cross-linking agent is dicumyl peroxide.

[0025] As preferred, in the step (2), the heavy metal tailings powder is one or more of iron tailings, molybdenum tailings, tungsten tailings.

[0026] As preferred, the heavy metal tailings powder has a chloride ion content ≤0.3%, and a sulfide content ≤0.5%.

[0027] The iron, molybdenum, tungsten tailings are derived from the gravity separation process, and their common characteristics are that the mineral composition is relatively simple, and is mainly composed of stable silicate or oxide minerals such as quartz, feldspar, garnet, molybdenite, scheelite / black tungsten ore, etc., and the crystal structure is stable and the surface chemical inertness is strong. This chemical inertness is crucial, as it ensures that the surface of the tailings particles does not release a large amount of soluble ions. The strict limitation of the content of harmful impurities is a forward-looking design for the long-term durability and environmental compatibility of the entire material system. The chloride ion content is controlled to fundamentally eliminate the risk of inducing electrochemical corrosion of surrounding metal components in the humid environment of the roadbed in the future. The limitation of the sulfide (calculated as S ion) content to ≤0.5% is to prevent the gradual oxidation of sulfide to generate sulfuric acid under the action of water and oxygen in the later stage, thereby causing acid hydrolysis damage to the molecular chain of the superabsorbent polymer and causing sulfate erosion to the gelling component in the system, leading to material strength degradation and swelling cracking, ensuring the volume stability and performance durability of the roadbed stabilizer during the service life. The heavy metal tailings powder particles are relatively coarse, and the water content can be easily controlled at a low level of less than 2%. In the present application, step (2) requires hot air drying to obtain dehydrated superabsorbent polymer, and the heavy metal tailings powder provides a good dispersion skeleton for the superabsorbent polymer during this process, which is beneficial to efficient dehydration.

[0028] As preferred, in the step (2), the further crushing process is: the dried material is crushed to an average particle size of 10-20 μm by air flow crushing, and a nitrogen protective atmosphere is maintained during the crushing process.

[0029] The jet milling utilizes high-speed airflow to give particles extremely high kinetic energy, and realizes high-efficiency crushing through the violent collision and friction between particles, and has high energy utilization rate and no pollution of grinding medium, and is especially suitable for efficiently preparing the polyacrylic superabsorbent resin / tailings composite into a powder with concentrated particle size distribution, and this specific particle size range ensures that the composite desiccant particles can be uniformly dispersed in the roadbed matrix during subsequent use, a large number of uniformly distributed micro-nano water storage units are formed, and the water absorption and water release behavior and stress distribution are optimized. Nitrogen is used as the milling medium and a protective atmosphere is maintained, on the one hand, the explosive environment that may be formed due to the mixing of high-concentration organic dust and air during milling and conveying is completely eliminated, the oxygen concentration is continuously controlled below the limit oxygen concentration through inertization treatment, and the risk of dust explosion is completely eliminated from the source; on the other hand, the nitrogen atmosphere effectively isolates oxygen and prevents the oxidative degradation of the polyacrylic superabsorbent resin molecular chain under the conditions of a new surface and high mechanical energy input, avoids the inactivation of active functional groups such as carboxyl groups, and thereby maximizes the functional integrity and long-term chemical stability of the composite desiccant.

[0030] As preferred, in the step (3), the floated metal tailings are one or more of 180-220 mesh copper tailings, lead-zinc tailings, or fluorite tailings.

[0031] As preferred, the floated metal tailings have a chloride content of ≤0.5%, a sulfide content of ≤1.0%, and a free calcium oxide content of ≤4.0%.

[0032] The flotation process is generally controlled at about 200 mesh, and too fine will cause mudification and affect the flotation yield, and too coarse will cause poor capture of target minerals and also affect the efficiency. However, there is an inevitable mudification part in the process of refining to 200 mesh, the average particle size of the flotation metal tailings is fine, drying is difficult, and at the same time, since the flotation agent needs to be combined to regulate the pH to achieve flotation optimization, therefore the pH of the flotation metal tailings is not stable. The present application fully considers this problem, after the flotation metal tailings are prepared by pressure filtration and the like, the water content is between 10-20%, the present application does not need to control the water content of the flotation metal tailings, and the slurry treatment of the flotation metal tailings is to stabilize the unstable pH to a controllable range, and most of the chlorides are water-soluble substances, which can be removed through the slurry and dehydration processes. The particle size range ensures that the particles of the flotation metal tailings have a large enough specific surface, can form a good particle accumulation with the steel slag and slag powder in the B material, reduce the void ratio, and provide a physical skeleton for the final formation of a dense roadbed structure. The energy consumption of the pressure filtration process is low, the filter cake after pressure filtration is mixed with the composite drying agent, and the residual water in the filter cake is mainly absorbed by the polyacrylic acid superabsorbent resin in the composite drying agent. The free calcium oxide (f-CaO) is limited to ≤4.0%, which is to solve the problem of delayed volume expansion caused by hydration in the later stage. The reaction generates calcium hydroxide with volume doubling, which will produce a huge expansion stress in the material, causing cracking and structure fluffiness. Strictly controlling the content is one of the keys to ensure the volume stability of the roadbed.

[0033] Preferably, in the step (5), the stirring condition is 500-800 rpm; the densification process is extrusion or rolling; and the standing time is 30-60 min.

[0034] The material is densified by extrusion or rolling, which can allow the composite drying agent to fully contact the pretreated metal tailings powder particles; and the temperature during the standing and aging is 40-50℃, which is mainly to allow the composite drying agent to adsorb the water on the surface of the metal tailings powder particles.

[0035] Preferably, in the step (6), the steel slag powder is subjected to magnetic separation treatment, and the specific surface area is ≥400 m 2 / kg, and the free calcium oxide content of the steel slag powder is ≤3.0%.

[0036] The B material of the present scheme uses industrial steel slag powder as the main material, and the steel slag powder in the field refers to the slag after blast furnace steelmaking, not the crushed material of steel or its products, which is sieved after grinding to obtain a specific surface area of 350-400 m 2 / kg, the process mainly improves the specific surface area, which is equivalent to the activation function, and the active activator is added to the steel slag powder and stirred uniformly for use. The purpose of magnetic separation treatment is to remove the magnetic substances such as elemental iron or ferrous oxide remaining in the smelting process; these impurities will cause slow electrochemical corrosion in a humid environment, produce iron rust with volume expansion, and thus form stress concentration points in the material, destroying the integrity of the hydration product. The subsequently added slag powder curing agent, also a solid waste in the steel smelting industry, has a specific surface area greater than 400m 2 / kg, mainly in the form of glass body, has no independent water hardness itself, but contains a large number of potential active sites. Under the excitation conditions of the excitation agent in the scheme, the calcium-silicon ions in the glass body can dissociate and react with water to generate cementitious substances.

[0037] In summary, on the basis of raw material optimization, the heavy metal tailings powder is mixed into the gel block of the polyacrylic superabsorbent resin and dispersed together, the heavy metal tailings powder has the characteristics of coarse particle size and easy drying, which is used as the skeleton supporting the gel block of the polyacrylic superabsorbent resin during the drying process, and acts as an abrasive during the crushing process, improving the dispersibility of the polyacrylic superabsorbent resin after being made into powder, and then a composite desiccant is prepared, avoiding the high-energy consumption drying link; after the pH of the flotation metal tailings is adjusted by slurry, although the specific components still have differences between different minerals, the pH is adjusted to be beneficial to the water absorption range of the composite desiccant, and the content of soluble harmful elements is also controlled, which is mixed into the treated flotation metal tailings, controlling the moisture content and optimizing the particle dispersibility; the B material is densified by dry ball milling to realize mechanical force activation of the steel slag and the slag, and the diammonium hydrogen phosphate is matched to construct a high-activity curing system. Finally, after 30-50 parts of A material and 30-50 parts of B material are mixed with water, the B material rapidly hydrates into a gel to form a complex crosslinked network, and the composite desiccant on the surface of the A material can provide hydration conditions for the B material, and more importantly, can form coordination with the active sites on the surface of the B material, especially the metal ion exposed sites, through electrostatic interaction, to form a strengthening effect.

[0038] On the other hand, the application also provides a roadbed stabilizing material using inorganic solid waste as raw material, which is prepared by the above-mentioned preparation method of the roadbed stabilizing material using inorganic solid waste as raw material.

[0039] Compared with the prior art, the present application has the following advantages:

[0040] 1.The present application avoids the high energy consumption drying link in the process of utilizing metal tailings, and the metal tailings obtained by different processes are integrated into different stages of the preparation process of composite drying agent: the heavy metal tailings powder particles are coarse and easy to dry, which are dispersed, dried and crushed together with the superabsorbent polymer, which is beneficial to improve the dispersion effect and drying efficiency; the flotation metal tailings fluctuate greatly, the pH is adjusted, and a low-cost dewatering process is selected to adapt the composite drying agent, which can further control the moisture, eliminate the drying process of the flotation metal tailings, and achieve the goal of low energy consumption.

[0041] 2.The present application also controls the harmful elements to a low level by limiting the technical indicators of metal tailings, steel slag powder and other materials obtained by different processes, prevents the harmful elements from damaging the strength of the matrix and affecting the water absorption effect of the superabsorbent polymer; the mechanical force activation and magnetic purification of the steel slag and slag powder significantly improve the reactivity and exclude unstable factors, and build a high-activity alkaline activation and curing system, and the control of the present application ensures the stability of the roadbed material performance. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 The preparation flow chart of the roadbed stabilizing material in the embodiment of the present application is shown in the figure.

[0043] Figure 2 A material prepared in Example 1 of the present application is shown in the figure.

[0044] Figure 3 B material prepared in Example 1 of the present application is shown in the figure.

[0045] Figure 4 The morphology of the roadbed stabilizing material prepared in Example 1 of the present application after maintenance is shown in the figure.

[0046] Figure 5 The morphology of the roadbed stabilizing material prepared in Comparative Example 1 after maintenance is shown in the figure. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments of the present application will be described in detail below, obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0048] The specific scheme of the present application is as follows:

[0049] The embodiment of the present application provides a preparation method of roadbed stabilizing material using inorganic solid waste as raw material, according to mass fraction, combining Figure 1 as shown in the figure, including the following steps:

[0050] (1) Preparation of gel block: 100 parts of acrylic acid is added to 80-100 parts of water and stirred uniformly, then 0.5-0.8 parts of ammonium persulfate is added, and reacted at 60-65℃ for 1.5-2.5h, 1-3 parts of dicumyl peroxide is added to the solution after reaction, and continue to react at 60-65℃ for 1.5-2.5h to obtain a gel block of polyacrylic acid superabsorbent resin.

[0051] (2) Preparation of composite desiccant: 50-150 mesh heavy metal tailings powder is added to the gel block for stirring, crushing, drying, and further crushing to obtain a composite desiccant.

[0052] In this step, the mass ratio of gel block to heavy metal tailings powder is 1:30-40; hot air drying is carried out at 60℃ and 3L / min nitrogen gas flow until the moisture content of the composite desiccant is less than 0.5%, then the dried material is crushed by air flow crushing method to an average particle size of 10-20μm, and nitrogen protective atmosphere is maintained during the crushing process, the air flow rate is 340m / s, to obtain a composite desiccant;

[0053] Preferably, the heavy metal tailings powder is one or more of iron tailings, molybdenum tailings, and tungsten tailings; the chloride ion content in the heavy metal tailings powder is ≤0.3%, and the sulfide content is ≤0.5%.

[0054] (3) Preparation of slurry: the flotation metal tailings are treated by slurry preparation to form a slurry with a solid mass fraction of 10-15%, and the pH is adjusted to 8-10.

[0055] In this step, the flotation metal tailings are one or more of 180-220 mesh copper tailings, lead-zinc tailings, or fluorite tailings; the chloride ion content of the flotation metal tailings is ≤0.5%, the sulfide content is ≤1.0%, and the free calcium oxide content is ≤4.0%.

[0056] (4) Preparation of filter cake: 0.1-0.3ppm PAM is added to the slurry, and the slurry is dewatered to a filter cake with a moisture content of 12-18%.

[0057] (5) Preparation of A material: under the condition of 500-800rpm stirring, the composite desiccant is added to the filter cake, wherein the mass ratio of filter cake to composite desiccant is 1:1-1.2, and after uniform stirring, the material is extruded or rolled to be dense, and then placed for 30-60min, dispersed, to obtain A material.

[0058] (6) Preparation of B material: 10-20 parts of steel slag powder, 0.3-1 parts of diammonium hydrogen phosphate, and 5-10 parts of slag powder solidification agent are dry ball milled for 30min to obtain B material.

[0059] In this step, the steel slag powder is treated by magnetic separation, and the specific surface area is ≥400m 2 / kg, the free calcium oxide content of the steel slag powder is less than or equal to 3.0%; the bulk density of the B material is 2.0-2.5 g / cm 3 .

[0060] (4) Preparing the roadbed stabilizing material: 30-50 parts of the A material is mixed with 30-50 parts of the B material, 8-15 parts of water is added and stirred uniformly to obtain the roadbed stabilizing material.

[0061] The application is further described below through specific examples:

[0062] In the examples and comparative examples:

[0063] The slag powder solidifying agent used satisfies the limitation of GB / T18046-2017 “Granulated Blast Furnace Slag Powder for Use in Cement, Mortar and Concrete”;

[0064] The heavy metal tailing powder, the flotation metal tailing and the steel slag powder used satisfy GB5085.3-2007 “Hazardous Waste Identification Standard Leaching Toxicity Identification” in terms of heavy metals;

[0065] The PAM is an anionic polyacrylamide (PAM).

[0066] Example 1

[0067] The embodiment provides a preparation method of a roadbed stabilizing material taking inorganic solid waste as raw material, which comprises the following steps according to mass parts:

[0068] (1) 100 parts of acrylic acid are added into 90 parts of water and stirred uniformly, then 0.6 parts of ammonium persulfate is added, and the reaction is carried out at 63℃ for 2h; 2 parts of dicumyl peroxide is added into the solution after the reaction, and the reaction is continued at 63℃ for 2h to obtain a gel block of polyacrylic acid superabsorbent resin.

[0069] (2) 100-mesh heavy metal tailing powder is added into the gel block, the mass ratio of the gel block to the heavy metal tailing powder is 1:35, and the gel block is stirred and crushed; the gel block is dried by hot air at 60℃ and under the condition of 3L / min nitrogen gas flow until the water content is 0.35%, then the dried material is crushed by airflow crushing to an average particle size of 15μm, and a nitrogen protective atmosphere is maintained during the crushing process, and the airflow rate is 340m / s to obtain a composite drying agent.

[0070] The heavy metal tailing powder is iron tailing; the chloride ion content in the heavy metal tailing powder is 0.25%, and the sulfide content is 0.4%.

[0071] (3) The flotation metal tailing slurry is prepared into a slurry with a solid mass ratio of 13% (pH is 4.8), and the pH is adjusted to 9.

[0072] The flotation metal tailings are copper tailings with a particle size of 200 mesh; the content of chloride ions in the flotation metal tailings is 0.4%, the content of sulfides is 0.8%, and the content of free calcium oxide is 3.0%.

[0073] (4) 0.2 ppm of PAM is added to the slurry, and dehydration is performed to obtain a filter cake with a moisture content of 15%.

[0074] (5) The filter cake is mixed with the composite drying agent at a mass ratio of 1:1.1 under stirring at 650 rpm, and then uniformly stirred and extruded to be compact, and then left to stand for 45 min, and then dispersed to obtain A material, as shown in Figure 2 .

[0075] (6) 15 parts of steel slag powder, 0.6 parts of diammonium hydrogen phosphate and 7 parts of slag powder curing agent are dry ball-milled to be compact for 30 min to obtain B material.

[0076] The steel slag powder is subjected to magnetic separation treatment, and has a specific surface area of 450 m 2 / kg; the content of free calcium oxide in the steel slag powder is 2.0%; the bulk density of the B material is 2.3 g / cm 3 , as shown in Figure 3 .

[0077] (7) 40 parts of A material and 40 parts of B material are mixed, 12 parts of water is added and stirred to be uniform, and then a roadbed stabilizing material is obtained.

[0078] The structure of the roadbed stabilizing material prepared in the embodiment is tested, and the morphology of the surface with a magnification of 100 times after curing for 7 days is shown in Figure 4 . As can be seen from Figure 4 , under a 100 times stereomicroscope, the surface is compact, and there are few microcracks.

[0079] The roadbed stabilizing material prepared in the embodiment is tested, and the test results are shown in Table 1.

[0080] Example 2

[0081] The difference between the embodiment and Example 1 is only that:

[0082] (1) 100 parts of acrylic acid are added to 80 parts of water and stirred to be uniform, then 0.5 parts of ammonium persulfate is added, and the reaction is carried out at 60°C for 2.5 h; then 1 part of dicumyl peroxide is added to the solution after the reaction, and the reaction is continued at 60°C for 2.5 h to obtain a gel block of polyacrylic acid superabsorbent resin.

[0083] (2) Add 50-mesh re-election metal tailings powder into the gel block, the mass ratio of the gel block and the re-election metal tailings powder is 1:30, carry out stirring and crushing, hot air dry at 60℃ and under the condition of 3L / min nitrogen gas flow until the water content is 0.37%, then crush the dry material to an average particle size of 10μm by air flow crushing, keep nitrogen protective atmosphere during the crushing process, the air flow rate is 340m / s, and obtain a composite drying agent.

[0084] The re-election metal tailings powder is molybdenum tailings; the chloride ion content in the re-election metal tailings powder is 0.3%, and the sulfide content is 0.3%.

[0085] (3) Prepare the flotation metal tailings slurry into a slurry with a solid mass ratio of 10% (pH is 6.8), and adjust the pH to 8.

[0086] The flotation metal tailings are 180-mesh lead-zinc tailings; the chloride ion content of the flotation metal tailings is 0.5%, the sulfide content is 0.6%, and the free calcium oxide content is 2.5%.

[0087] (4) Add 0.1ppm of PAM in terms of slurry mass, and dewater to a filter cake with a water content of 12%.

[0088] (5) Mix and stir evenly under the condition of 500rpm stirring according to the mass ratio of the filter cake:composite drying agent is 1:1, then extrude and densify, stand for 30min, and disperse to obtain A material.

[0089] (6) Dry ball mill 10 parts of steel slag powder, 0.3 parts of diammonium hydrogen phosphate and 5 parts of slag powder solidifying agent for 30min to obtain B material.

[0090] The steel slag powder is treated by magnetic separation, and the specific surface area is 400m 2 / kg; the free calcium oxide content of the steel slag powder is 1.5%; and the bulk density of the B material is 2.15g / cm 3 .

[0091] (7) Mix 30 parts of A material with 30 parts of B material, add 8 parts of water and stir evenly to obtain roadbed stabilizing material.

[0092] Test the roadbed stabilizing material prepared in this embodiment, and the test results are shown in Table 1.

[0093] Example 3

[0094] The difference between this embodiment and Example 1 is only that: (1) add 100 parts of acrylic acid into 100 parts of water and stir evenly, then add 0.8 parts of ammonium persulfate, react at 65℃ for 1.5h, add 3 parts of dicumyl peroxide into the solution after reaction, and continue to react at 65℃ for 1.5h to obtain a gel block of polyacrylic acid superabsorbent resin.

[0095] (2) Add 150-mesh re-election metal tailings powder into the gel block, the mass ratio of the gel block and the re-election metal tailings powder is 1:40, and the gel block and the re-election metal tailings powder are stirred and crushed, and then hot air drying is performed at 60°C and under the condition of 3L / min nitrogen gas flow until the water content is 0.42%, and then the dried material is crushed to an average particle size of 20μm by air flow crushing, and a nitrogen protective atmosphere is maintained during the crushing process, and the air flow rate is 340m / s, to obtain a composite drying agent.

[0096] In the re-election metal tailings powder, the chloride ion content is 0.1%, and the sulfide content is 0.5%.

[0097] (3) The flotation metal tailings slurry is prepared into a slurry with a solid mass ratio of 15% (pH is 8.2), and the pH is adjusted to 10.

[0098] In the flotation metal tailings, the chloride ion content is 0.2%, the sulfide content is 1.0%, and the free calcium oxide content is 4.0%.

[0099] (4) 0.3ppm of PAM is added to the slurry, and the filter cake with a water content of 18% is obtained by dewatering.

[0100] (5) The filter cake and the composite drying agent are mixed and stirred uniformly under the condition of 800rpm stirring, and then extruded and densified, and then placed for 60min, and then dispersed, to obtain A material.

[0101] (6) 20 parts of steel slag powder, 1 part of diammonium hydrogen phosphate, and 10 parts of slag powder curing agent are dry ball milled and densified for 30min to obtain B material.

[0102] In the steel slag powder, the specific surface area is 500m 2 / kg, and the free calcium oxide content of the steel slag powder is 3.0%; the bulk density of the B material is 2.38g / cm 3 .

[0103] (7) 50 parts of A material and 50 parts of B material are mixed, 15 parts of water is added and stirred uniformly, to obtain roadbed stabilizing material.

[0104] The roadbed stabilizing material prepared in the embodiment is tested, and the test results are shown in Table 1.

[0105] Example 4

[0106] The difference between the embodiment and Example 1 is only that:

[0107] (1) 100 parts of acrylic acid was added into 85 parts of water and stirred uniformly, then 0.55 parts of ammonium persulfate was added, and reacted at 61℃ for 2.2 hours, 1.5 parts of dicumyl peroxide was added into the solution after reaction, and continued to react at 61℃ for 2.2 hours, to obtain a gel block of polyacrylic acid superabsorbent resin.

[0108] (2) 80 mesh heavy metal tailings powder was added into the gel block, the mass ratio of the gel block and the heavy metal tailings powder was 1:32, and hot air drying was carried out at 60℃ and 3L / min nitrogen gas flow until the water content was 0.31%, then the dried material was crushed by air flow crushing method to an average particle size of 12μm, and a nitrogen protective atmosphere was maintained during the crushing process, and the air flow rate was 340m / s, to obtain a composite drying agent.

[0109] The heavy metal tailings powder is a mixture of iron tailings and molybdenum tailings; the chloride ion content in the heavy metal tailings powder is 0.2%, and the sulfide content is 0.35%;

[0110] (3) The flotation metal tailings slurry was prepared into a slurry with a solid mass ratio of 11% (pH 6.5), and the pH was adjusted to 8.5.

[0111] The flotation metal tailings are a mixture of 190 mesh copper tailings and lead-zinc tailings; the chloride ion content of the flotation metal tailings is 0.3%, the sulfide content is 0.7%, and the free calcium oxide content is 2.0%.

[0112] (4) 0.15ppm of PAM was added to the slurry, and the filter cake was dewatered to a water content of 14%.

[0113] (5) The filter cake and the composite drying agent were mixed and stirred uniformly at a mass ratio of 1:1.05 under the condition of 600rpm stirring, then extruded and densified, and placed for 35min, and dispersed, to obtain A material.

[0114] (6) 12 parts of steel slag powder, 0.4 parts of diammonium hydrogen phosphate and 6 parts of slag powder curing agent were dry ball milled for 30min to obtain B material.

[0115] The steel slag powder was treated by magnetic separation, and the specific surface area was 420m 2 / kg, and the free calcium oxide content of the steel slag powder was 1.0%; the bulk density of the B material was 2.18g / cm 3 .

[0116] (7) 35 parts of A material and 35 parts of B material were mixed, 9 parts of water was added and stirred uniformly, to obtain a roadbed stabilizing material.

[0117] The roadbed stabilizing material prepared in this embodiment was tested, and the test results are shown in Table 1.

[0118] Example 5

[0119] The difference between this example and Example 1 is only:

[0120] (1) 100 parts of acrylic acid were added to 95 parts of water and stirred uniformly, then 0.75 parts of ammonium persulfate was added, and reacted at 64°C for 1.8h, 2.5 parts of dicumyl peroxide was added to the solution after reaction, and continued to react at 64°C for 1.8h, to obtain a gel block of polyacrylic acid superabsorbent resin.

[0121] (2) 120 mesh heavy metal tailings powder was added to the gel block, the mass ratio of gel block to heavy metal tailings powder was 1:38, and the gel block and heavy metal tailings powder were stirred and crushed, and then hot air dried at 60°C and 3L / min nitrogen gas flow to a water content of 0.3%, then the dried material was crushed by air flow crushing to an average particle size of 18μm, and a nitrogen protective atmosphere was maintained during the crushing process, and the air flow rate was 340m / s, to obtain a composite drying agent.

[0122] Among them, the heavy metal tailings powder is a mixture of molybdenum tailings and tungsten tailings; the chloride ion content in the heavy metal tailings powder is 0.15%, and the sulfide content is 0.45%.

[0123] (3) The flotation metal tailings were made into a slurry with a solid mass ratio of 14% (pH 7.3), and the pH was adjusted to 9.5.

[0124] Among them, the flotation metal tailings are a mixture of 210 mesh lead-zinc tailings and fluorite tailings; the chloride ion content of the flotation metal tailings is 0.45%, the sulfide content is 0.9%, and the free calcium oxide content is 3.5%.

[0125] (4) 0.25ppm of PAM was added to the slurry, and the filter cake was dewatered to a water content of 16%.

[0126] (5) The filter cake and the composite drying agent were mixed and stirred uniformly at a mass ratio of 1:1.15 under the condition of 700rpm stirring, then extruded and densified, and then placed for 55min, and then dispersed, to obtain A material.

[0127] (6) 18 parts of steel slag powder, 0.8 parts of diammonium hydrogen phosphate and 9 parts of slag powder solidifying agent were dry ball milled for 30min to obtain B material.

[0128] Among them, the steel slag powder is treated by magnetic separation, and the specific surface area is 480m 2 / kg, and the free calcium oxide content of the steel slag powder is 2.5%; the bulk density of B material is 2.34g / cm 3 .

[0129] (7) 45 parts of A material and 45 parts of B material were mixed, 14 parts of water was added and stirred uniformly, to obtain a roadbed stabilizing material.

[0130] The roadbed stabilizing material prepared in this example was tested, and the test results are shown in Table 1.

[0131] Comparative Example 1

[0132] The only difference between this comparative example and Example 1 is that:

[0133] The roadbed stabilizing material was prepared by directly mixing and stirring the same proportions of the heavy metal tailings powder, the floating metal tailings, the steel slag powder, the slag powder stabilizer, the diammonium hydrogen phosphate and water as in Example 1.

[0134] The structure of the roadbed stabilizing material prepared in this example was tested, and the surface morphology at 100 times magnification after 7 days of curing is shown in Figure 5 From Figure 5 it can be seen that there are more cracks on the surface under the 100 times visual microscope.

[0135] The roadbed stabilizing material prepared in this comparative example was tested, and the test results are shown in Table 1.

[0136] Comparative Example 2

[0137] The only difference between this comparative example and Example 1 is that:

[0138] In step (2), the heavy metal tailings powder was replaced by the floating metal tailings, and the time required for hot air drying at 60°C and a nitrogen gas flow of 3L / min to a water content of 0.35% was about twice that of Example 1.

[0139] The roadbed stabilizing material prepared in this comparative example was tested, and the test results are shown in Table 1.

[0140] Comparative Example 3

[0141] The only difference between this comparative example and Example 1 is that:

[0142] In step (2), the mass ratio of the gel block to the heavy metal tailings powder was 1:45.

[0143] The roadbed stabilizing material prepared in this comparative example was tested, and the test results are shown in Table 1.

[0144] Comparative Example 4

[0145] The only difference between this comparative example and Example 1 is that:

[0146] In step (2), the mass ratio of the gel block to the heavy metal tailings powder was 1:25.

[0147] The roadbed stabilizing material prepared in this comparative example was tested, and the test results are shown in Table 1.

[0148] Comparative Example 5

[0149] The difference between the present comparative example and Example 1 is only that:

[0150] In step (2), the stirring and crushing are not followed by drying treatment, and the moisture content is 1.3%.

[0151] The roadbed stabilizing material prepared in the present comparative example is tested, and the test results are shown in Table 1.

[0152] Comparative Example 6

[0153] The difference between the present comparative example and Example 1 is only that:

[0154] In step (3), the pH of the slurry is 4.8, and the pH is not adjusted.

[0155] The roadbed stabilizing material prepared in the present comparative example is tested, and the test results are shown in Table 1.

[0156] Comparative Example 7

[0157] The difference between the present comparative example and Example 1 is only that:

[0158] In step (4), PAM is not added.

[0159] The roadbed stabilizing material prepared in the present comparative example is tested, and the test results are shown in Table 1.

[0160] Comparative Example 8

[0161] The difference between the present comparative example and Example 1 is only that:

[0162] In step (4), the moisture content of the filter cake is 20%.

[0163] The roadbed stabilizing material prepared in the present comparative example is tested, and the test results are shown in Table 1.

[0164] Comparative Example 9

[0165] The difference between the present comparative example and Example 1 is only that:

[0166] In step (6), the dry ball milling is not performed, and the bulk density of the B material is 1.54 g / cm 3 .

[0167] The roadbed stabilizing material prepared in the present comparative example is tested, and the test results are shown in Table 1.

[0168] Comparative Example 10

[0169] The difference between the present comparative example and Example 1 is only that:

[0170] In step (2), the content of chloride ion in the heavy metal tailing powder is 0.32%, and the content of sulfide is 0.54%.

[0171] The roadbed stabilizer prepared in the present comparative example was tested, and the test results are shown in Table 1.

[0172] Comparative Example 11

[0173] The present comparative example differs from Example 1 only in that:

[0174] The chloride ion content of the floated metal tailings in Step (3) was 0.53%, the sulfide content was 1.17%, and the free calcium oxide content was 4.3%.

[0175] The roadbed stabilizer prepared in the present comparative example was tested, and the test results are shown in Table 1.

[0176] Comparative Example 12

[0177] The present comparative example differs from Example 1 only in that:

[0178] The free calcium oxide content of the steel slag powder in Step (6) was 3.3%.

[0179] The roadbed stabilizer prepared in the present comparative example was tested, and the test results are shown in Table 1.

[0180] Comparative Example 13

[0181] The present comparative example differs from Example 1 only in that:

[0182] Step (1) was cancelled, and the commercial polyacrylic acid superabsorbent resin (SDK, Qingdao Shouke New Materials) was mixed with the gravity metal tailings powder in Step (2).

[0183] The roadbed stabilizer prepared in the present comparative example was tested, and the test results are shown in Table 1.

[0184] Comparative Example 14

[0185] The present comparative example differs from Example 1 only in that:

[0186] After the 100-mesh gravity metal tailings powder was added to the gel block in Step (2), the mass ratio of the gel block to the gravity metal tailings powder was 1:35, and the gel block and the gravity metal tailings powder were stirred and crushed, and then hot air dried at 60°C and under a nitrogen gas flow of 3L / min until the water content was 0.35%, to obtain the composite drying agent.

[0187] The step was not performed by the air flow crushing method.

[0188] The roadbed stabilizer prepared in the present comparative example was tested, and the test results are shown in Table 1.

[0189] The detection methods of the examples and comparative examples of the present application are as follows:

[0190] 1. Water absorption rate detection of composite desiccant: 5 groups of 1 g of composite desiccant were weighed and put into water, respectively, and after standing for 60 min at 25°C, they were filtered out, drained until no water dripped, and then weighed to increase the weight. The water absorption specific gravity = (weight after water absorption - 1 g) x 100%;

[0191] 2. Detection of unconfined compressive strength: The tailings-steel slag synergistic solidified road subgrade stabilizer prepared from all examples and comparative examples was sampled and cured for 7 days according to the standard in the Ministry of Communications "Highway Geotechnical Test Procedures" (JTG-E40), and the test sample was obtained, and the unconfined compressive strength (MPa) was detected;

[0192] 3. Heavy metal ion leaching concentration detection: After the unconfined compressive strength detection was completed, the same shape and weight of the sample block was soaked in water for 7 days, and whether the dissolved heavy metal met the requirements was tested according to "Groundwater Quality Standard" (GB / T14848-9);

[0193] 4. Sulfur and chlorine leaching concentration detection: Reference is made to "HJ557-2010 Solid Waste Leaching Toxicity Leaching Method Horizontal Oscillation Method";

[0194] 5. Water stability detection: Reference is made to "Inorganic Binder Stabilized Material Immersion Test" in "JTGE40-2007 Highway Geotechnical Test Procedures", and after immersion for 7 days, the compressive strength loss rate (≤15% is excellent) is measured;

[0195] 6. Consistency test: The standard cone with a mass of 300 g and a cone bottom diameter of 40 mm is used to test the depth of immersion in the finished product prepared from the examples and comparative examples, and the depth of immersion is read as the consistency value.

[0196] The detection results are shown in Table 1.

[0197] Table 1 Performance detection results of examples and comparative examples

[0198]

[0199] In the examples and comparative examples, the tailings components of the same variety are all from the same source, the component difference is not large, and the heavy metal dissolution meets the requirements of GB5085.3 for heavy metals.

[0200] Examples 1 to 5 are based on raw material control, combined with the different treatment of different process metal tailings in the preparation process, to realize efficient water absorption and uniform dispersion of the composite desiccant, reduce the uncertain influence of the flotation metal tailings, and finally realize the preparation of high-performance subgrade stabilizer combined with the B material solidification system. The consistency of examples 1 to 5 is concentrated in 118-132 mm, with narrow fluctuation, meeting the construction and performance requirements of wet solid waste subgrade stabilizer, indicating good batching stability and suitability for quality control in the construction process.

[0201] Compared with Example 1, the untreated A material and B material of Comparative Example 1 were directly mixed, resulting in uneven dispersion of solid waste particles, many internal voids, and acidic floating metal tailings, which led to a sharp decrease in strength and water stability. Figure 5 and Figure 4 (Example 1 surface) can be seen, Figure 5More obvious microcracks; Comparative Example 2 uses flotation metal tailings to replace gravity metal tailings powder to prepare composite drying agent, because the flotation metal tailings have fine particle size, large specific surface area and easy agglomeration, the prepared roadbed stabilizer has low consistency, which not only hinders the water absorption channel of the superabsorbent polymer, but also destroys the water absorption effect due to its acidic characteristics. In addition, the time required for hot air drying to 0.35% moisture content under the condition of 60℃ and 3L / min nitrogen gas flow is about twice that of Example 1, the advantage of reducing energy consumption is lost; Comparative Example 3 because the gravity metal tailings powder is excessive, it dilutes the relative content of the superabsorbent polymer, which weakens the humidity adjusting ability of the composite drying agent, and the prepared roadbed stabilizer has low consistency, which cannot effectively alleviate the roadbed dry shrinkage; Comparative Example 4 because the gravity metal tailings powder is insufficient, the superabsorbent polymer lacks enough rigid particle support and swells excessively, occupying the internal pore of the roadbed, the prepared roadbed stabilizer has high consistency, which affects the structure density; Comparative Example 5 because the composite drying agent is not dried, the residual moisture occupies the water absorption sites of the superabsorbent polymer and the tailings capillary pores in advance, resulting in the failure of the composite drying agent, and interfering with the hydration reaction of B material; Comparative Example 6 because the pH of the flotation metal tailings is not adjusted, the metal ions on the surface of the tailings cannot be precipitated in the acidic environment, which not only leads to the easy leaching of sulfur and chlorine elements, but also weakens the interfacial bonding strength between the flotation metal tailings and the composite drying agent; Comparative Example 7 because PAM is not added, the fine particles of the flotation metal tailings cannot form flocculation, which has poor dispersibility and is difficult to wrap free harmful ions, affecting the overall stability of the roadbed; Comparative Example 8 because the moisture content of the flotation metal tailings filter cake is too high, the composite drying agent still makes A material in a wet state after absorbing excess water, which hinders the uniform hydration of B material and the compaction of the roadbed, resulting in low consistency; Comparative Example 9 because B material is not dry ball milled, the surface energy of steel slag and slag particles is low, and the lattice defects are few, so the activity cannot be effectively excited, the strength of the solidified system is insufficient and the water stability is poor, and the loose bulk density is low, indicating that the particles are not in full contact; Comparative Example 10 because the sulfur and chlorine content of the gravity metal tailings powder exceeds the standard, harmful ions will slowly corrode the molecular chain of the superabsorbent polymer and block the matrix pores, reducing the water absorption efficiency of the composite drying agent and the impermeability of the roadbed; Comparative Example 11 because the sulfur and chlorine content and the free calcium oxide content of the flotation metal tailings exceed the standard, not only intensifies the risk of harmful ion leaching, but also causes volume expansion due to the hydration of free calcium oxide in the later stage, resulting in microcracks in the roadbed; Comparative Example 12 because the free calcium oxide content of the steel slag exceeds the standard, the volume increases when calcium hydroxide is generated by hydration in the later stage, which destroys the overall structure of the solidified body and leads to a decrease in strength and water stability; Comparative Example 13 because the commercial superabsorbent polymer and the gravity metal tailings powder are physically mixed without forming in-situ polymerization synergy, the resin is easy to agglomerate and cannot achieve uniform dispersion and efficient water absorption and release; Comparative Example 14 because the composite drying agent is not treated by airflow crushing, the uneven particle size leads to unbalanced dispersion of the composite drying agent in the roadbed, inconsistent water absorption and release behavior, and local dry shrinkage or bleeding, affecting the performance stability of the roadbed.

Claims

1. A method for producing a roadbed stabilizer using inorganic solid waste as a raw material, characterized by comprising the steps of: According to mass parts, comprising the following steps: ​ (1) Preparation of gel block: 100 parts of acrylic acid is added to 80-100 parts of water, after stirring evenly, 0.5-0.8 parts of initiator is added, and the reaction is carried out at 60-65℃ for 1.5-2.5h, 1-3 parts of crosslinking agent is added, and the reaction is continued at 60-65℃ for 1.5-2.5h, to obtain a gel block of polyacrylic acid superabsorbent resin; (2) Preparation of composite desiccant: the gel block is added with 50-150 mesh heavy selected metal tailings powder for stirring, crushing, drying and further crushing treatment to obtain a composite desiccant; wherein the mass ratio of the gel block to the heavy selected metal tailings powder is 1:30-40, and the composite desiccant has a water content of less than 0.5% and an average particle size of 10-20μm; (3) Preparation of slurry: the flotation metal tailings are treated by slurry preparation to obtain a slurry; the solid mass content of the slurry is 10-15%, and the pH value is 8-10; (4) Preparation of filter cake: the slurry is added with PAM at a content of 0.1-0.3ppm of the slurry mass for dewatering treatment to obtain a filter cake with a water content of 12-18%; (5) Preparation of A material: the filter cake and the composite desiccant are mixed under stirring at a mass ratio of 1:1-1.2, followed by densification, standing and dispersion treatment to obtain A material; (6) Preparation of B material: 10-20 parts of steel slag powder, 0.3-1 part of diammonium hydrogen phosphate and 5-10 parts of slag powder solidifying agent are dry ball milled and densified to obtain B material; (7) Preparation of roadbed stabilizing material: 30-50 parts of A material and 30-50 parts of B material are mixed, and 8-15 parts of water is added and stirred uniformly to obtain a roadbed stabilizing material.

2. The method for producing a roadbed stabilizer using inorganic solid waste according to Claim 1, wherein In the step (1), the initiator is ammonium persulfate, and the crosslinking agent is dicumyl peroxide.

3. The method for producing a roadbed stabilizer using inorganic solid waste according to Claim 1, wherein In the step (2), the heavy selected metal tailings powder is one or more of iron tailings, molybdenum tailings and tungsten tailings.

4. The method for producing a roadbed stabilizer using inorganic solid waste according to Claim 3, wherein The heavy selected metal tailings powder has a chloride content of ≤0.3% and a sulfide content of ≤0.5%.

5. The method for producing a roadbed stabilizer using inorganic solid waste according to Claim 1, wherein In the step (2), the further crushing process is that the dried material is crushed to an average particle size of 10-20μm by air flow crushing, and a nitrogen protective atmosphere is maintained during the crushing process.

6. The method for producing a roadbed stabilizer using inorganic solid waste according to Claim 1, wherein In the step (3), the flotation metal tailings are one or more of 180-220 mesh copper tailings, lead-zinc tailings or fluorite tailings.

7. The method for producing a roadbed stabilizer using inorganic solid waste according to Claim 6, wherein The flotation metal tailings have a chloride content of ≤0.5%, a sulfide content of ≤1.0% and a free calcium oxide content of ≤4.0%.

8. The method for producing a roadbed stabilizer using inorganic solid waste according to Claim 1, wherein In the step (5), the stirring condition is 500-800rpm; the densification process is extrusion or rolling; and the standing time is 30-60min.

9. The method for producing a roadbed stabilizer using inorganic solid waste according to Claim 1, wherein In the step (6), the steel slag powder is treated by magnetic separation, and the specific surface area is ≥400 m 2 / kg, and the free calcium oxide content of the steel slag powder is ≤3.0%.

10. A roadbed stabilizing material using inorganic solid waste as raw material, characterized in that, The roadbed stabilizing material is prepared by the method of any one of claims 1-9.

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