Self-adapting heavy metal solidification and blocking micro-particle and preparation of high volume steel slag micro-powder cement concrete by using the same

Abstract

The application discloses a self-adaptive heavy metal solidification and blocking micro-particle, which comprises, from inside to outside, a heavy metal dissolution blocking agent inner core, a triggerable capsule wall and a heavy metal solidification agent shell layer arranged in sequence; wherein the heavy metal dissolution blocking agent inner core material is mainly obtained by compounding silicate and nano-scale active silicon dioxide, the triggerable capsule wall material comprises a pH trigger material and a heat-curing resin; and the heavy metal solidification agent shell layer material is mainly obtained by compounding and intercalating modified kaolin, a calcium-silicon ratio regulator and a sulfate. The application mainly reduces heavy metal dissolution of large-dosage steel slag micro-powder concrete in a service process from two aspects of early solidification and later prevention, and reduces the cracking risk of the large-dosage steel slag micro-powder concrete in a preventive and later compensatory mode; the application can meet the requirements of multiple scene services, and even when the concrete has slight cracks, the application will not increase the risk of heavy metal dissolution, and is suitable for popularization and application.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to an adaptive heavy metal solidification-blocking microparticle and high-volume steel slag micropowder cement concrete prepared using it. Background Technology

[0002] Steel slag is a byproduct of steelmaking, accounting for approximately 15-20% of total steel production. The annual discharge of steel slag is enormous, but its utilization rate is very low, resulting in it being largely left as waste and stockpiled. It is one of the major bulk solid wastes. Steel slag has a complex composition, containing impurities such as phosphides, active metal oxides, and heavy metals. On-site dumping not only occupies large amounts of land, but the trace elements and alkaline substances within the slag can also seep into the surrounding soil and water through rainwater runoff, causing harm to the environment. To improve the utilization rate of steel slag and reduce its environmental harm, the resource utilization of steel slag solid waste has become a research hotspot.

[0003] Currently, there are some reports on using steel slag powder as one of the raw materials for heavy metal solidification agents, which can achieve good application results under stable pH conditions in the environment. However, studies have found that at low pH values, the leaching of heavy metal elements such as Cu, Mn, Zn, and Cr from steel slag increases significantly, exceeding the limits specified for Class III surface water in the "Surface Water Environmental Quality Standard". Therefore, when steel slag is directly piled up without treatment or used as a raw material for concrete, especially when it is soaked in acid rain for a long time, it is necessary to curb the pollution of surrounding water resources by the soaking liquid of steel slag powder concrete. CN 115353303 A discloses an industrial solid waste cement for heavy metal pollution control, including blast furnace water quenching slag, steel slag, desulfurization gypsum, cement clinker, etc., using the main components of traditional cement as auxiliary materials for this type of solid waste cement. CN 108863267 A discloses a method for preparing heavy metal solidification agents using polycrystalline silicon waste, which involves mixing active additives with materials such as steel slag, slag, zeolite, clinker, and modified gypsum and then grinding them. While the heavy metal curing agents described above possess a certain capacity for heavy metal curing, they often pose a risk of heavy metal re-leaching under acidic conditions due to their high solid waste content. Furthermore, steel slag has relatively low activity; when applied to concrete, it forms a large amount of calcium hydroxide during hydration, posing a risk of later cracking and further leaching of internal heavy metal ions. Further exploration of adaptive heavy metal curing-blocking materials suitable for various environments is of significant research and application value. Summary of the Invention

[0004] The main objective of this invention is to address the problems and shortcomings in the existing steel slag resource utilization process by providing an adaptive heavy metal solidification-blocking microparticle suitable for high-volume steel slag micro-powder cement concrete. This microparticle can meet the requirements of multiple service scenarios and will not increase the risk of heavy metal leaching even when the concrete has minor cracks.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] An adaptive heavy metal curing-blocking microparticle comprises, from the inside out, a heavy metal leaching blocker core, a triggering capsule wall, and a heavy metal curing agent shell layer arranged sequentially. The heavy metal leaching blocker core material is mainly composed of silicate and nano-sized active silica composite; the triggering capsule wall material includes a pH triggering material and a thermosetting resin; and the heavy metal curing agent shell layer material is mainly composed of a modified kaolin-based composite intercalating material, a calcium-silicon ratio regulator, and a sulfate composite.

[0007] In the above scheme, the adaptability of the heavy metal solidification-blocking microparticles is reflected in the fact that when concrete cracks or the alkaline environment of the system changes, causing the pH value of the pore solution to decrease, it will affect the stability of the triggering capsule wall material, causing it to gradually dissolve and release the core blocking agent material. The internal core material will be exposed to the alkaline environment and quickly hydrate to generate gel and other products to repair the concrete cracks and further block the leaching of heavy metals in steel slag.

[0008] In the above scheme, the diameter of the core of the heavy metal leaching inhibitor is 60-80 μm, the wall thickness of the trigger capsule is 3-10 μm, and the thickness of the heavy metal curing agent shell is 20-40 μm.

[0009] In the above scheme, the components and their mass percentages in the core material of the heavy metal leaching inhibitor include: 65-75% nano-sized active silica and 25-35% silicate.

[0010] In the above scheme, the silicate is solid sodium silicate or potassium silicate powder with an average particle size of 5-30 μm, is easily soluble, and has a modulus of 0.5-3.0.

[0011] In the above scheme, the nanoscale active silica is mainly one of silica ash and pure silica seed crystals or a mixture of the two, with a particle size of 50-300nm.

[0012] In the above scheme, the pH triggering material and the thermosetting resin are sequentially disposed on the inner surface of the heavy metal leaching blocker core.

[0013] In the above scheme, the pH triggering material can be one or more of ethyl cellulose EC, polyvinylpyrrolidone PVP, etc.

[0014] In the above scheme, the pH triggering material is first placed on the surface of the heavy metal leaching blocker core to form microcapsules, and then a thermosetting resin is placed on the surface of the microcapsules.

[0015] In the above scheme, the mass ratio of the pH triggering material to the heavy metal leaching inhibitor core is 1:2.6-3.2; the mass ratio of the thermosetting resin to the total mass (mass of microcapsules) of the pH triggering material and the heavy metal leaching inhibitor core is 1:2-3.

[0016] In the above scheme, the thermosetting resin can be selected from one of phenolic resin, urea-formaldehyde resin, melamine-formaldehyde resin, epoxy resin, unsaturated resin, polyurethane, polyimide, etc., with a resin viscosity of 10-500 mPa·s, a thermosetting temperature of 80-200℃, and a curing time of 15-30 min.

[0017] In the above scheme, the molecular weight of the ethyl cellulose is 50,000-100,000 and the molecular weight of the polyvinylpyrrolidone is 10,000-80,000.

[0018] In the above scheme, the components and their mass percentages in the heavy metal curing agent shell material include: 47-75% modified kaolin composite intercalating material, 22-50% calcium-silicon ratio regulator, and 3-5% sulfate.

[0019] In the above scheme, the modified kaolin composite intercalation material is prepared from kaolin materials and intercalation materials, and its particle size is 1-10μm. Among them, the kaolin materials can be one or more of the following: kaolinite (soil), coal-associated kaolinite (soil), coal gangue, dickite, perlite, halloysite, and layered carbonates with a 1:1 main type. The intercalation molecules can be one of the conventional kaolin intercalation materials such as alkali metal (alkoxide) salts, small organic molecules, polymer macromolecules, or polymer monomers.

[0020] In the above scheme, the modified kaolin composite intercalation material is mainly obtained by intercalating kaolin materials and intercalation materials through liquid phase intercalation, evaporative solvent intercalation, mechanochemical intercalation, microwave radiation, or ultrasonic treatment. The specific intercalation method is selected according to the properties of the intercalation molecules.

[0021] In the above scheme, the modified kaolin composite intercalation materials are classified into stable kaolin composite intercalation materials and unstable kaolin composite intercalation materials according to the type of kaolin. The distinction is as follows: if the intercalating molecules used in the preparation process of the intercalation material are alkali metal salt ions, the composite intercalation material is considered to be an unstable kaolin composite intercalation material; if the intercalating molecules are small organic molecules, polymer macromolecules, or polymer monomers, then it is a stable kaolin composite intercalation material.

[0022] In the above scheme, the particle size of the calcium-silicon ratio regulator is 5-15 μm; according to the type of modified kaolin composite intercalation material, it is divided into activating type and stabilizing type calcium-silicon ratio regulator: the activating type calcium-silicon ratio regulator is suitable for stable kaolin composite intercalation materials, and selects one or more of metakaolin, calcined coal gangue, low-calcium fly ash, etc., with the overall Al / Si maintained between 0.3-0.5; the stabilizing type calcium-silicon ratio regulator is suitable for unstable kaolin composite intercalation materials, and uses one or more of mineral powder, high-calcium fly ash, carbide slag, phosphorus slag, manganese slag, etc., with the overall Al / Si maintained below 0.2.

[0023] In the above scheme, the sulfate can be one or more of natural gypsum, desulfurized gypsum, phosphogypsum, fluorogypsum, etc.; the particle size of the sulfate regulator is 15-30μm.

[0024] In the above scheme, the heavy metal curing agent shell material is obtained by ball milling a mixture of modified kaolin-based composite intercalating material, calcium-silicon ratio regulator, and sulfate in a certain proportion. The ball milling speed is set to 100-500 rpm, and the milling time is 10-30 min. The particle size of the resulting heavy metal curing agent shell material is 1-5 μm.

[0025] In the above scheme, the average particle size of the heavy metal leaching inhibitor material is 4-100 μm.

[0026] The above-mentioned method for preparing adaptive heavy metal solidification-blocking microparticles includes the following steps:

[0027] 1) Dissolve gelatin and emulsifier in water to form an emulsifier solution, which serves as the aqueous phase;

[0028] 2) Dissolve the pH triggering material and the core material of the heavy metal leaching inhibitor in an organic solvent in a certain proportion to form a homogeneous mixed solution, which serves as the oil phase;

[0029] 3) Under stirring conditions (600-1000 rpm), the oil phase is added dropwise to the aqueous phase to form an O / W type emulsion; the mixture is stirred until the surface of the microcapsules solidifies. Then the stirring speed and temperature are adjusted to allow the solvent to evaporate fully; the surface suspended matter of the resulting reaction product is removed and the mixture is allowed to stand. At this point, the formed microcapsules precipitate at the bottom of the reaction vessel. The microcapsules are washed and dried at room temperature to obtain the microcapsules.

[0030] 4) Place the obtained microcapsules in a sugar coating machine, spray a quantitative amount of thermosetting resin to wet the surface of the microcapsules, and then add heavy metal curing agent shell material to evenly cover the surface of the microcapsules to form core-shell particles.

[0031] 5) The obtained core-shell particles are heated and cured (100-200℃, the resin molecules will cross-link with each other and combine with the pH trigger material capsule wall to form a strong solid structure; in addition, the expansion of concrete cracks destroys the capsule wall and the acidification of the external environment can jointly trigger the capsule wall to release the internal blocking agent), and finally the desired heavy metal curing-blocking agent microparticles are obtained.

[0032] In the above scheme, the emulsifier can be one or more of the following: sodium dodecyl sulfate, Tween, octylphenol polyoxyethylene ether, etc.

[0033] In the above scheme, the mass ratio of gelatin to water in step 1) is 5-10:90-95; the emulsifier accounts for 1-3% of the mass of the aqueous phase.

[0034] In the above scheme, the stirring process in step 3) uses a temperature of 25-35℃ and a time of 2-3h; after adjusting the speed and temperature, the speed is 500-700r / min, the temperature is 40-45℃, and the time is 2-3h.

[0035] The present invention also provides a high-volume steel slag micro-powder cement concrete based on the above-mentioned heavy metal solidification-blocking microparticles, wherein the amount of heavy metal solidification-blocking microparticles is 3-6% of the mass of cementitious materials.

[0036] Furthermore, in the high-volume steel slag micro-powder cement concrete, the components and their respective weight percentages include: 340-370 parts of cementitious material, 980-1100 parts of coarse aggregate, 870-900 parts of fine aggregate, and 10-20 parts of heavy metal curing and reinforcing agent, wherein the content of steel slag micro-powder in the cementitious material is 9-20 wt%.

[0037] In the above scheme, the cementing material also includes one or more of cement, mineral powder, etc.

[0038] The principle of this invention is as follows:

[0039] The microparticles of this invention consist of three parts: a heavy metal curing agent shell, a triggering capsule wall, and a heavy metal leaching inhibitor core. In the early hydration stage, the surface curing agent shell rapidly binds to heavy metal ions released from steel slag dissolution through physical adsorption methods such as charge attraction, ion or ion cluster substitution, and steric hindrance. In a highly alkaline environment, it further undergoes a dissolution reaction to generate CSH gels with a low calcium-to-silicon ratio, ettringite-like solid solutions, etc., achieving chemical curing of the heavy metals. In the later hardening stage, the inhibitor core remains stably present within the microparticles. When changes in the external environment or the formation of cracks cause changes in the pH of the pore solution, it stimulates the release and dissolution hydration of the inhibitor core material, simultaneously blocking the leaching of heavy metals from the internal pore solution and repairing cracks. This invention primarily reduces heavy metal leaching in high-volume steel slag micropowder concrete during service from two aspects: early curing and late-stage prevention. It also reduces the cracking risk of high-volume steel slag micropowder concrete through prevention and late-stage compensation.

[0040] On the one hand, in the early stage of hydration, the heavy metal curing agent on the surface of the microparticles first undergoes a dissolution-reaction, which takes place through physical adsorption-chemical curing: the modified amorphous kaolin-like intercalating material in the curing agent has a high specific surface area and can effectively adsorb heavy metal ions in the pore solution; and both it and the calcium-silicon ratio regulator have certain pozzolanic activity. In an alkaline environment, it will further combine with calcium ions in the pore solution to form a low-calcium-silicon ratio CSH gel; the ratio of silicate ions to calcium ions in the low-calcium-silicon ratio CSH gel is lower, its structure is more stable, its micromechanical properties are better, and it will affect the chemical form of heavy metals in it; heavy metals in the low-calcium-silicon ratio CSH gel tend to undergo hydration reactions to form relatively stable compounds, thereby reducing their activity and toxicity. These ion substitutions mainly include heavy metal ions being able to replace calcium and silicon in CSH (e.g., Pb). 2+ Cu 2+ and Zn 2+ It can replace Ca in CSH 2+ Cr 3+ Can replace Si in CSH 4+ (and compensate for potential equilibrium with other ions); in addition, under sulfate and high Al / Si conditions, aluminosilicates will also combine with heavy metal ions to form ettringite-like solid solutions (such as Cd). 2+ Co 2+ Ni 2+ Zn 2+ Can replace Ca in ettringite 2+ , while Cr 3+ Can replace Al in ettringite 3+ CrO4 2- Can replace SO4 2-The material further solidifies heavy metal ions through the "binding" of hydration products and encapsulates unhydrated steel slag, limiting its dissolution and the release of internal heavy metals. This not only effectively improves the solidification efficiency of heavy metals but also reduces the impact of calcium hydroxide generated by steel slag hydration in the later stages of hardening on the volume stability of the concrete matrix, thus reducing the risk of cracking caused by expansive crystals to a certain extent. Based on this physical adsorption-chemical solidification approach, this two-phase material can effectively solidify heavy metal ions released by early steel slag hydration, significantly improving the early heavy metal solidification capacity of concrete. That is, even when the strength of steel slag concrete is low, there will be no large amount of heavy metal leaching.

[0041] On the other hand, in the later stage of hydration, the shell of the microparticles reacts completely, and the internal blocking agent core material is exposed. In a normal environment, the core material exists stably and does not have a significant impact on the macroscopic properties of concrete. When the concrete is affected by external media erosion, internal product generation, and internal and external cracks, causing changes in the internal alkaline environment, the shell of the blocking agent core material (i.e., the triggering capsule material), which is more sensitive to pH value, will be affected first and begin to dissolve and release the internal nanoscale active silica. Due to its high specific surface area and extremely fine particle size, nano-sized silica can fill the tiny voids inside concrete and react rapidly with the hydration products of cement and steel slag to form a gel. This not only significantly improves the compressive, tensile, and flexural mechanical properties of concrete, but also enhances its density and durability. When excess f-CaO in steel slag hydrates in the cement-based hardened body to form calcium hydroxide, the increased alkalinity and crystallization pressure lead to the formation of microcracks. This promotes the release and dissolution hydration of active silica (promoting the destruction and dissolution hydration of the glass structure of nano-silica), consumes calcium hydroxide to reduce internal crystallization pressure, and generates a gel to repair cracks, delaying further intrusion of external ions and further expansion of cracks. In addition, the generated gel will further cement heavy metal ions in the pore solution, delaying their dissolution.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] 1) The heavy metal solidification-blocking microparticles adopt a combination of physical adsorption and chemical solidification, which significantly improves the solidification efficiency of heavy metals; and they have high hydration activity. They can also regulate the phase composition and structure of hydration products in steel slag concrete through self-hydration and synergistic reaction with unhydrated particles (such as mineral powder and fly ash) and hydration products (such as calcium hydroxide) in the concrete itself, so as to optimize the compactness, mechanical properties and durability of the concrete matrix.

[0044] 2) The effective period of the heavy metal solidification-blocking microparticles covers the entire service life of the concrete. It will start to work from the early stage and will block and repair the possible losses and heavy metal leaching of the concrete matrix in the later stage. It can also inhibit the leaching of heavy metals in concrete under various environmental influences (acid rain erosion, dynamic water erosion, etc.).

[0045] 3) The heavy metal curing-blocking microparticles described in this invention have small particle size, which will not affect the particle stacking structure of concrete, and the surface curing agent has a fast dissolution-hydration rate and efficient curing reaction; the overall composition is stable and has good storage properties; it is suitable for widespread application. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the structure of the adaptive heavy metal solidification-blocking microparticles according to an embodiment of the present invention;

[0047] Figure 2 This is a schematic diagram of the preparation process of adaptive heavy metal solidification-blocking microparticles according to an embodiment of the present invention. Detailed Implementation

[0048] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. These descriptions are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention.

[0049] Example 1

[0050] An adaptive heavy metal curing-blocking microparticle (heavy metal curing enhancer) suitable for acid rain erosion, its composition and preparation steps are as follows:

[0051] 1) Heavy metal curing agent shell material

[0052] A calcium-silicon ratio regulator, a stabilized kaolin-based composite intercalation material, and phosphogypsum were mixed at a mass ratio of 42:54:4 and ball-milled at 350 rpm for 30 min using a planetary ball mill to obtain a heavy metal curing agent shell material with an average particle size of 3.7 μm.

[0053] The calcium-silicon ratio regulator used was obtained by ball milling a mixture of 40 wt% metakaolin, 40 wt% calcined coal gangue, and 20 wt% low-calcium fly ash. The average particle size of the metakaolin was 4.5 μm; the average particle size of the calcined coal gangue was 7.9 μm; the average particle size of the low-calcium fly ash was 12.8 μm with a calcium oxide content of 7% and a calcination vector of 5%. The Al / Si ratio of the calcium-silicon ratio regulator was 0.34, and the Ca / (Si+Al) ratio was <0.5.

[0054] The modified kaolin composite intercalation material was prepared by ultrasonic oscillation of kaolin and dimethyl sulfoxide (DMSO). The specific steps included: preparing a DMSO solution (the volume ratio of DMSO to water was 10:1), selecting kaolin with an average particle size of 6.9 μm, adjusting the mass ratio of kaolin to DMSO solution to 0.15:1, mixing and placing it in an ultrasonic cleaner, ultrasonically oscillating at 80℃ for 2 hours, removing it and filtering it three times with anhydrous ethanol, and finally placing it in a forced-air drying oven at 50℃ to dry, thereby obtaining a stable kaolin composite intercalation material.

[0055] The sulfate used was phosphogypsum, with an average particle size of 23.6 μm;

[0056] 2) Core material of heavy metal blocking agent

[0057] Silicate and nano-sized active silica were mixed evenly at a mass ratio of 32:68 to obtain the core material of the heavy metal blocking agent. The nano-sized active silica used was obtained by mixing silica fume SF96 and pure silica seed crystals at a mass ratio of 8:2, with an average particle size of 154 nm. The silicate was solid sodium silicate with a modulus of 2.0. 3) Preparation of heavy metal solidification-blocking microparticles.

[0058] Gelatin was dissolved in deionized water at a mass ratio of 6:92, and sodium dodecyl sulfate (2% by mass of the aqueous phase) was added to form a homogeneous gelatin solution as the aqueous phase. Ethyl cellulose (6% by mass of the oil phase) and the heavy metal blocking core material were dissolved in dichloromethane at a mass ratio of 1:2 to form a homogeneous mixed solution as the oil phase. The oil phase was slowly added dropwise to the aqueous phase at a mass ratio of 1:1 using a dropper, and stirred at 700 rpm for 30 min to form an O / W emulsion. After the oil phase was completely added, stirring was continued at 40°C for 3 h, at which point the microcapsule surface solidified. The stirring speed (600 rpm) and temperature (42°C) were adjusted to allow for complete solvent evaporation, with an evaporation time of 2 h. The resulting solution was then used to fill the microcapsule container. The suspended matter on the surface of the microcapsule solution in the beaker is removed, and the mixture is allowed to stand for 20 minutes. At this time, the formed microcapsules settle at the bottom of the beaker. The microcapsules at the bottom of the beaker are washed three more times and then dried at room temperature to obtain microcapsules. 300 parts of the obtained microcapsules are placed in a sugar coating machine. The machine is operated at an inclination angle of 45° and a speed of 50 rpm. 120 parts of phenolic resin are sprayed to wet the surface of the microcapsules. Then, heavy metal curing agent shell material is added to evenly cover the surface of the capsules to form a shell. Finally, the obtained "core-shell" particles are heated and cured at 150°C (the resin molecules will cross-link with each other and combine with the ethyl cellulose capsule wall to form a strong solid structure), thus obtaining the heavy metal curing-blocking agent microparticles (denoted as microparticle A).

[0059] Example 2

[0060] A heavy metal curing and reinforcing agent (denoted as microparticle B) is prepared in a manner largely the same as in Example 1, except for its chemical composition, which is detailed below:

[0061] 1) Heavy metal curing agent shell material

[0062] The calcium-silicon ratio regulator, the unstable kaolin composite intercalation material, and the desulfurized gypsum were mixed in a mass ratio of 50:47:3 and then ball-milled at 450 rpm for 40 min using a planetary ball mill to obtain a heavy metal curing agent shell material with an average particle size of 3.2 μm.

[0063] The calcium-silicon ratio regulator used was obtained by mixing and ball milling 40 wt% mineral powder, 20 wt% carbide slag, and 40% high-calcium fly ash. The average particle size of the mineral powder was 10.1 μm; the average particle size of the carbide slag was 12.2 μm; the average particle size of the high-calcium fly ash was 11.9 μm; and the Al / Si ratio of the calcium-silicon ratio regulator was 0.18.

[0064] The modified kaolin composite intercalation material was prepared by liquid-phase intercalation of kaolin and sodium methoxide. The specific steps included: mixing sodium methoxide and methanol at a mass ratio of 1:4 to obtain an intercalation solution; selecting kaolin with an average particle size of 7.4 μm; adjusting the mass ratio of kaolin to the intercalation solution to 0.1:1; heating to 60°C and stirring; refluxing and maintaining the temperature for 10 h; removing the reactants and centrifuging; and drying the obtained solid at 80°C to obtain the unstable kaolin composite intercalation material.

[0065] The sulfate used was desulfurized gypsum with an average particle size of 19.6 μm.

[0066] 2) Heavy metal blocking agent core

[0067] Silicate and nano-sized active silica were mixed evenly at a mass ratio of 25:75 to obtain the core material of the heavy metal blocking agent. The nano-sized active silica used was obtained by mixing silica ash SF96 and pure silica seed crystals at a mass ratio of 8:2, with an average particle size of 154nm. The silicate was sodium silicate with a modulus of 2.0.

[0068] Comparative Example 1

[0069] The heavy metal curing agent shell component (without blocking agent and capsule wall material) in Example 1 was used as Comparative Example 1 and labeled as curing agent C.

[0070] Comparative Example 2

[0071] The heavy metal curing agent shell component (without blocking agent and capsule wall material) in Example 2 was used as Comparative Example 2 and labeled as curing agent D.

[0072] Comparative Example 3

[0073] The heavy metal capsule wall-blocking agent component (shellless material) in Example 1 was used as Comparative Example 3 and labeled as curing agent E.

[0074] Comparative Example 4

[0075] The heavy metal capsule wall-blocking agent component (shellless material) in Example 2 was used as Comparative Example 4 and labeled as curing agent F.

[0076] Comparative Example 5

[0077] The heavy metal blocking agent component (without shell material and capsule wall material) in Example 1 was used as Comparative Example 5 and labeled as curing agent G.

[0078] Comparative Example 6

[0079] The heavy metal blocking agent component (without shell material and capsule wall material) in Example 2 was used as Comparative Example 6 and labeled as curing agent H.

[0080] Comparative Example 7

[0081] A heavy metal curing enhancer (denoted as curing agent I) with the same structure as in Example 1 is prepared by a method largely the same as in Example 1, but differs in its chemical composition, as detailed below:

[0082] 1) Heavy metal curing agent shell material

[0083] Unstable kaolin composite intercalation materials were ball-milled at 350 rpm for 30 min using a planetary ball mill to obtain a heavy metal curing agent shell material with an average particle size of 3.7 μm.

[0084] The modified kaolin composite intercalation material used was prepared by ultrasonic oscillation of kaolin and dimethyl sulfoxide (DMSO). The specific steps included: preparing a DMSO solution (the volume ratio of DMSO to water was 10:1), selecting kaolin with an average particle size of 6.4 μm, adjusting the mass ratio of kaolin to DMSO solution to 0.15:1, mixing and placing it in an ultrasonic cleaner, ultrasonically oscillating at 80℃ for 2 hours, removing it and filtering it three times with anhydrous ethanol, and finally placing it in a forced-air drying oven at 50℃ to dry, thereby obtaining a stable kaolin composite intercalation material.

[0085] 2) Core material of heavy metal blocking agent

[0086] The nano-sized active silica described in Example 1 is used as the core material of the heavy metal blocking agent. The nano-sized active silica is obtained by mixing silica ash SF96 and pure silica seeds at a mass ratio of 8:2, with an average particle size of 154 nm.

[0087] The heavy metal curing-blocking agent microparticles (denoted as curing agent I) are described.

[0088] Application Example 1

[0089] The heavy metal solidification-blocking microparticles obtained in this invention are applied to the preparation of steel slag micropowder concrete. The concrete is composed of the following materials: cementitious materials: steel slag micropowder, cement, and mineral powder, in weight percentages of 2%, 9.3%, and 5.1%, respectively; aggregates: fine aggregate and coarse aggregate, in weight percentages of 36.7% and 42.6%, respectively; water and water-reducing agent, in weight percentages of 3.9% and 0.4%, respectively; the steel slag micropowder is finely ground converter steel slag powder with a specific surface area of ​​498 m². 2 / kg, CaO content is 47.2%, alkalinity is 2.9; the cement is P·O 42.5; the fine aggregate is natural river sand, which is zone 2 medium sand with a fineness modulus of 2.8; the coarse aggregate is 5-31.5mm continuously graded limestone crushed stone; the water-reducing agent is polycarboxylate water-reducing agent with a water reduction rate of 15%;

[0090] The specific preparation steps include: weighing the raw materials according to the formula ratio, adding the water-reducing agent and curing and strengthening agent to water and stirring evenly for later use; pouring the weighed aggregate into a concrete mixer and mixing for 1-3 minutes to mix evenly; then, pouring the cementitious materials (steel slag powder, cement, and mineral powder) into the concrete mixer and mixing for 1-3 minutes to ensure that all components are evenly mixed with the aggregate; pouring the water mixed with the water-reducing agent and heavy metal curing-blocking microparticles into the concrete mixer, mixing for 1-2 minutes, and then discharging to obtain the steel slag powder concrete; the material selection requirements for each application example are as follows (see Table 1 for details):

[0091] Application Example 1-1: Blank control, without adding the heavy metal curing-blocking microparticles described in the examples and comparative example AI, directly using concrete composed of the above materials.

[0092] Application Examples 1-2: The curing enhancer used is the heavy metal curing-blocking microparticle A obtained in Example 1, with an admixture amount of 6% (by weight) of the cementitious material.

[0093] Application Examples 1-3: The curing enhancer used is the heavy metal curing-blocking microparticle B obtained in Example 2, with a dosage of 6% of the cementitious material.

[0094] Application Examples 1-4: The curing reinforcing agent used is the heavy metal curing-blocking microparticle C obtained in Comparative Example 1, with a dosage of 6% of the cementitious material.

[0095] Application Examples 1-5: The curing reinforcing agent used is the heavy metal curing-blocking microparticle D obtained in Comparative Example 2, with a dosage of 6% of the cementitious material.

[0096] Application Examples 1-6: The curing reinforcing agent used is the heavy metal curing-blocking microparticle E obtained in Comparative Example 3, with a dosage of 6% of the cementitious material.

[0097] Application Examples 1-7: The curing reinforcing agent used is the heavy metal curing-blocking microparticle F obtained in Comparative Example 4, with a dosage of 6% of the cementitious material.

[0098] Application Examples 1-8: The curing reinforcing agent used is the heavy metal curing-blocking microparticle G obtained in Comparative Example 5, with a dosage of 6% of the cementitious material.

[0099] Application Examples 1-9: The curing reinforcing agent used is the heavy metal curing-blocking microparticle H obtained in Comparative Example 6, with a dosage of 6% of the cementitious material.

[0100] Application Examples 1-10: The curing reinforcing agent used was the heavy metal curing-blocking microparticle I obtained in Comparative Example 7, with a dosage of 6% of the cementitious material.

[0101] After mixing the above components evenly, the concrete setting time and concrete block strength were measured according to the standards GB / T50080-2002 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures" and GB / T 50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete". The test samples were prepared according to the standard HJ / T 300-2007 "Leaching Toxicity of Solid Waste - Acetic Acid Buffer Solution Method".

[0102] Table 1. C40 Concrete Mix Proportion

[0103]

[0104]

[0105] The mechanical properties of the steel slag micropowder concrete obtained in each application example, the heavy metal leaching performance at 7 days and 28 days of curing, and the heavy metal leaching performance of the matrix after artificially applying a pressure of 20 MPa to introduce microcracks are shown in Table 2. The results indicate that the introduction of the heavy metal solidification-blocking microparticles described in this invention promotes the strength development of concrete at all ages, and significantly reduces the heavy metal leaching of steel slag concrete in both the early and late stages of hydration, demonstrating strong solidification ability. However, adding only the blocking agent (i.e., the core material) does not significantly improve the heavy metal solidification ability at 7 days of hydration. Conversely, the heavy metal solidification ability of the sample with only the heavy metal solidifying agent (i.e., the shell material) is not significantly different from that of the sample with the heavy metal solidification-blocking microparticles, indicating that the shell material of the heavy metal solidification-blocking microparticles can effectively adsorb the early hydration of steel slag. The leaching of heavy metals; in addition, comparing concrete samples with and without encapsulated wall materials, the encapsulated wall material, due to its ability to encapsulate the internal active silica under high pH conditions, limited its leaching. Therefore, the encapsulated wall material did not significantly improve the early-stage heavy metal curing ability of the blocker. On the other hand, the introduction of the blocker without encapsulated wall material was equivalent to the direct introduction of active silica material, which promoted early strength and caused it to hydrate rapidly, but did not significantly improve later-stage strength. This indicates that the role of the encapsulated wall is mainly to ensure the "adaptability" and "self-regulation" of the concrete. After artificially applying a pressure of 20 MPa, cracks appeared inside the steel slag concrete, and the leaching of heavy metals increased in all groups. Compared to the control group, the increase in heavy metal leaching was significantly reduced after adding heavy metal solidification-blocking microparticles. Furthermore, compared to samples containing blocking agents, samples without blocking agents showed greater heavy metal leaching, indicating that the blocking agents effectively repaired the cracks and inhibited heavy metal leaching. In contrast, samples containing only blocking agents without a shell material had their effective components involved in hydration in the early stages, thus lacking repair function. The steel slag microparticle concrete obtained by this invention can balance good compressive strength and heavy metal leaching inhibition performance, and also has adaptive control performance. Moreover, when using a single-component shell and core coating mechanism, although the obtained heavy metal solidification-blocking microparticles have a certain solidification effect on heavy metals, the effect is far lower than that of the multi-component coupled solidification microparticles described in this invention.

[0106] Table 2. Compressive strength and heavy metal leaching test results of C40 concrete

[0107]

[0108] Application Example 2

[0109] A steel slag micro-powder concrete is prepared in a manner largely similar to that in application example 1, except that:

[0110] The cementitious material comprises steel slag powder, cement, and mineral powder in the following weight percentages: 1.5%, 9.4%, and 5.5%, respectively; aggregates: fine aggregate and coarse aggregate, in the following weight percentages: 34.8% and 44.5%, respectively; water and water-reducing agent in the following weight percentages: 4.2% and 0.3%, respectively; the steel slag powder is finely ground converter steel slag powder with a specific surface area of ​​455 m². 2 / kg, CaO content is 47.8%, alkalinity is 3.0; the cement is P·O 42.5; the fine aggregate is manufactured sand; the coarse aggregate is limestone crushed stone; the water-reducing agent is polycarboxylate water-reducing agent.

[0111] Application Example 2-1: Blank control, without adding the early strength agent described in the examples, directly using concrete composed of the above materials.

[0112] Application Example 2-2: Add the heavy metal solidification-blocking microparticles A described in Example 1 to concrete composed of the above materials, at a dosage of 3% (by weight) of the cementitious material.

[0113] Application Examples 2-3: Add the heavy metal solidification-blocking microparticles B described in Example 2 to concrete composed of the above materials, at a dosage of 3% (by weight) of the cementitious material.

[0114] Application Examples 2-4: The heavy metal curing agent C described in Comparative Example 1 was added to concrete composed of the above materials at a dosage of 3% (by weight) of the cementitious material.

[0115] Application Example 2-5: Add the heavy metal curing agent D described in Comparative Example 2 to concrete composed of the above materials, at a dosage of 3% (by weight) of the cementitious material.

[0116] Table 3. Mix Proportions for C40 Concrete

[0117]

[0118] Table 4. Compressive strength and heavy metal leaching test results of C40 concrete

[0119]

[0120]

[0121] The mechanical properties of the steel slag micropowder concrete obtained in each application example, the heavy metal leaching performance after 28 days of curing, and the heavy metal leaching performance of the matrix after artificially applying a pressure of 20 MPa to introduce microcracks are shown in Table 4. The results indicate that the introduction of the two types of heavy metal solidification-blocking microparticles significantly reduced the heavy metal leaching of the steel slag concrete, demonstrating strong solidification ability. After artificially applying a pressure of 20 MPa, cracks appeared inside the steel slag concrete, and the heavy metal leaching amount increased in all groups. Compared to the control group, the increase in heavy metal leaching amount was significantly reduced after adding the heavy metal solidification-blocking microparticles. Furthermore, compared to the sample containing the blocking agent component, the sample without the blocking agent showed a greater heavy metal leaching amount, indicating that the blocking agent effectively repaired the cracks after they appeared and inhibited the leaching of heavy metals. The steel slag micropowder concrete obtained by this invention can balance good compressive strength and heavy metal leaching inhibition performance, and also has adaptive control performance.

[0122] As can be seen from Application Examples 1 and 2, the heavy metal leaching performance of concrete under acidic conditions is significantly improved by either heavy metal curing-blocking microparticles (i.e., comparative examples) or heavy metal curing agents alone. Among them, the heavy metal curing effect of the example is the best, and its mechanical properties are also slightly increased.

[0123] Compared to the blank groups (1-1 and 2-1), the steel slag micro-powder concrete with added curing and strengthening agent showed significantly enhanced curing ability for heavy metals such as As, Cd, and Pb under acidic conditions. The heavy metal leaching test results all met the Class III groundwater toxicology standards in GB / T 14848. Compared to comparative examples 1-3, 1-4 and 2-3, 2-4, the examples showed stronger curing ability for Cr, significantly reducing the risk of heavy metal leaching. Furthermore, the 28-day compressive strength of the concrete with added curing and strengthening agent was superior to the control and blank groups, with an increase between 5.3% and 13.0%, indicating a certain enhancing effect on the mechanical properties of the concrete.

[0124] The adaptive heavy metal solidification-blocking microparticles of this invention consist of three parts: a solidifying agent shell, a triggering capsule wall, and a blocking agent core. The main functions of the solidifying agent shell and the blocking agent core are early solidification and later blocking and inhibition of re-release, respectively. In the early stage of hydration, the surface solidifying agent shell first binds to the heavy metal ions released from the dissolution of steel slag through physical adsorption methods such as charge attraction, ion or ion cluster substitution, and steric hindrance. In a highly alkaline environment, it further generates CSH gels and ettringite-like solid solutions with a low calcium-to-silicon ratio through dissolution reactions, achieving chemical solidification of heavy metals. In the later stage of hardening, the blocking agent core is stably present in the matrix. When the external environment changes or cracks occur, causing changes in the pH of the pore solution, the changes in the hydration rate and hydration products of the steel slag will stimulate the blocking agent core to dissolve and hydrate, blocking the dissolution of heavy metals in the internal pore solution while repairing cracks. When using these adaptive heavy metal solidification-blocking microparticles to prepare high-content steel slag micropowder cement concrete, it can meet the requirements of multi-scenario service. Even if the concrete has slight cracks, it will not increase the risk of heavy metal leaching.

[0125] This invention is not limited to the embodiments described above. Those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. An adaptive heavy metal solidification-blocking microparticle, characterized in that, From the inside out, it comprises a heavy metal leaching inhibitor core, a triggering capsule wall, and a heavy metal curing agent shell layer arranged sequentially. The heavy metal leaching inhibitor core material is mainly composed of silicate and nano-sized active silica composite. The triggering capsule wall material includes a pH triggering material and a thermosetting resin. The heavy metal curing agent shell layer material is mainly composed of modified kaolin-based composite intercalation material, a calcium-silicon ratio regulator, and sulfate composite. The core material of the heavy metal leaching inhibitor comprises the following components and their mass percentages: 65-75% nano-sized active silica and 25-35% silicate; the silicate is solid sodium silicate or potassium silicate powder. The heavy metal curing agent shell material comprises the following components and their mass percentages: 47-75% modified kaolin composite intercalating material, 22-50% calcium-silicon ratio regulator, and 3-5% sulfate. The pH triggering material is one or more of ethyl cellulose and polyvinylpyrrolidone; The modified kaolin composite intercalation material is prepared from kaolin materials and intercalation materials.

2. The adaptive heavy metal solidification-blocking microparticles according to claim 1, characterized in that, The inner core of the heavy metal leaching inhibitor has a diameter of 60-80 μm, the wall thickness of the triggering capsule is 3-10 μm, and the thickness of the heavy metal curing agent shell is 20-40 μm.

3. The adaptive heavy metal solidification-blocking microparticles according to claim 1, characterized in that, The silicate has an average particle size of 5-30 μm and a modulus of 0.5-3.0; the nanoscale active silica is mainly one of silica ash and pure silica seed crystals or a mixture of the two, with a particle size of 50-300 nm.

4. The adaptive heavy metal solidification-blocking microparticles according to claim 1, characterized in that, The thermosetting resin is one of phenolic resin, urea-formaldehyde resin, melamine-formaldehyde resin, epoxy resin, unsaturated resin, polyurethane, and polyimide, with a viscosity of 10-500 mPa·s, a thermosetting temperature of 80-200℃, and a curing time of 15-30 min.

5. The adaptive heavy metal solidification-blocking microparticles according to claim 1, characterized in that, The mass ratio of the pH triggering material to the heavy metal leaching inhibitor core is 1:2.6-3.

2.

6. The adaptive heavy metal solidification-blocking microparticles according to claim 1, characterized in that, The modified kaolin composite intercalation material has a particle size of 1-10 μm; the calcium-silicon ratio regulator has a particle size of 5-15 μm and is selected from one or more of metakaolin, calcined coal gangue, and low-calcium fly ash, with its Al / Si ratio maintained between 0.3 and 0.5; or it is selected from one or more of mineral powder, high-calcium fly ash, carbide slag, phosphorus slag, and manganese slag, with its Al / Si ratio maintained below 0.

2.

7. The adaptive heavy metal solidification-blocking microparticles according to claim 1, characterized in that, The sulfate is selected from one or more of natural gypsum, desulfurized gypsum, phosphogypsum, and fluorogypsum; its particle size is 15-30 μm.

8. The method for preparing the adaptive heavy metal solidification-blocking microparticles according to any one of claims 1 to 7, characterized in that, Includes the following steps: 1) Dissolve the emulsifier in water to form an emulsifier solution, which serves as the aqueous phase; 2) Dissolve the pH triggering material and the core material of the heavy metal leaching inhibitor in an organic solvent in a certain proportion to form a homogeneous mixed solution, which serves as the oil phase; 3) Under stirring conditions, the oil phase is added dropwise to the aqueous phase to form an O / W type emulsion; the mixture is stirred, and then the speed and temperature are adjusted to allow the solvent to fully evaporate; the surface suspension of the resulting reaction product is removed, the mixture is allowed to stand, washed, and dried to obtain microcapsules; 4) Spray thermosetting resin onto the surface of the microcapsules to wet the surface of the microcapsules, and then add heavy metal curing agent shell material to make it evenly cover the surface of the microcapsules to form core-shell particles; 5) The obtained core-shell particles are heated and solidified to obtain the adaptive heavy metal solidification-blocking microparticles.

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