Geopolymer improved granite residual soil as well as preparation method and application thereof

Abstract

The invention provides geopolymer improved granite residual soil as well as a preparation method and application thereof, and belongs to the technical field of geopolymer materials. The geopolymer improved granite residual soil comprises granite residual soil, a gel material and a carbonate alkali activator, the mixing amount of the gel material is 10-20% of the total mass of improved dry soil, the mass of equivalent Na2O generated by the carbonate alkali activator is 2.5-6.5% of the mass of the gel material, and the content of the equivalent Na2O generated by the carbonate alkali activator is 10-20% of the total mass of the granite residual soil. The gel material comprises the following components in parts by weight: 35-50 parts of glass superfine powder, 20-40 parts of petroleum refining deactivated catalyst powder and 10-35 parts of circulating fluidized bed combustion ash. The composite system reacts to generate an interpenetrating gel network and a compact pore structure, saltpetering of the material can be inhibited, long-term stabilization of heavy metal is realized, and freeze-thaw resistance, dynamic load fatigue resistance and dry-wet cycle resistance of the material are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of geopolymer materials technology, specifically relating to a geopolymer-modified granite residual soil, its preparation method, and its application. Background Technology

[0002] Granite residual soil, with its mineral composition dominated by quartz and kaolinite, has a loose structure and uneven gradation. It softens easily when exposed to water, and as embankment filler, it often presents engineering problems such as difficulty in compaction, inconsistent permeability and strength, water loss during the rainy season, and long-term deformation. Although traditional lime or cement amendments can improve early strength and stiffness, they result in high carbon emissions, limited durability in sulfate or chloride environments, insufficient bonding of weakly weathered skeleton particles, and a tendency to crack and pulverize under hot and humid climates and repeated wetting and drying processes. Therefore, they fail to meet the comprehensive requirements of current transportation infrastructure for low carbon emissions, durability, and long-term performance.

[0003] In recent years, geopolymer modification technology has attracted attention due to its ability to form gels such as NASH and C-(A)-SH. However, most existing methods rely on common solid wastes such as fly ash, slag, steel slag, and red mud, and employ high alkalinity activation. In the open-air, large-volume embankment construction scenario, high concentrations of soluble alkali metal ions tend to migrate to the surface and crystallize under early dehydration and capillary action, leading to efflorescence, white bloom, and surface powdering, affecting appearance and durability, and incurring additional maintenance costs. Simultaneously, some raw materials contain migratable heavy metals or halide impurities. Without effective encapsulation and fixation mechanisms and pore structure control, leaching under long-term infiltration conditions is uncertain, making it difficult to meet environmental standards. More critically, embankments are subjected to long-term traffic dynamic loads, wet-dry cycles, and freeze-thaw cycles. Microcracks within the material are prone to propagate under cyclic stress and volume changes, causing strength and stiffness degradation, increased cumulative deformation, and the reactivation of permeation channels. Existing systems remain insufficient in terms of freeze-thaw resistance, dynamic load fatigue resistance, and wet-dry degradation resistance.

[0004] Therefore, it is necessary to provide a method for preparing geopolymer-modified granite residual soil and its application to solve the above problems. Summary of the Invention

[0005] This invention provides a geopolymer-modified granite residual soil, its preparation method, and its application. It utilizes ultrafine glass powder to provide controllable silicon supply, petroleum refining deactivated catalyst powder to provide reactive aluminum and ion trapping sites, and circulating fluidized bed combustion ash to provide active calcium and densification capabilities. The (N,K)-ASH gel and C-(A)-SH gel generated by the composite system form an interpenetrating gel network and construct a dense porous structure, thereby inhibiting alkali blooming in the material from the source and achieving long-term stability of heavy metals. Simultaneously, it significantly improves the material's resistance to freeze-thaw cycles, dynamic fatigue, and wet-dry cycles, thus effectively solving at least one of the technical problems mentioned in the background art.

[0006] To solve the above-mentioned technical problems, the present invention is implemented as follows: A geopolymer-modified granite residual soil comprises granite residual soil, a gel material, and a carbonate-alkali activator. The amount of gel material is 10-20% of the total mass of the modified dry soil, and the equivalent Na2O mass generated by the carbonate-alkali activator is 2.5-6.5% of the mass of the gel material. The gel material comprises the following components by weight: 35-50 parts of ultrafine glass powder, 20-40 parts of petroleum refining deactivated catalyst powder, and 10-35 parts of circulating fluidized bed combustion ash and / or waste incineration bottom ash fine powder.

[0007] As a preferred improvement, the ultrafine glass powder has a SiO2 content ≥70wt%, a specific surface area ≥500m² / kg, and a D0.05 50 The particle size is 10-25 μm; the D of the deactivated catalyst powder from petroleum refining is... 50 The thickness is 5-20 μm, the loss on ignition is ≤8%, and the total amount of Al2O3 and SiO2 is ≥80 wt%; the circulating fluidized bed combustion ash has a CaO content <2 wt%, an SO3 content <3 wt%, and a Cl content <2 wt%. - The content is <0.05wt%; the SiO2 content of the fine powder from the waste incineration bottom ash is 35-55wt%, the CaO content is 15-30wt%, the SO3 content is <3wt%, and the Cl content is <0.05wt%. - The content is <0.05wt%; the carbonate alkali activator is Na2CO3 or a Na2CO3 / K2CO3 composite carbonate with a Na:K molar ratio of (3-5):1.

[0008] As a preferred improvement, the total Si:Al atomic ratio in all raw materials of the geopolymer-modified granite residual soil is 1.6-2.8, the Ca:Si molar ratio is 0.2-0.8, and the soluble Na... + The total amount is 0.18-0.96 wt%.

[0009] As a preferred improvement, the geopolymer-modified granite residual soil further includes chopped fibers, the volume of which accounts for 0.15-0.35% of the volume of the gel material, and the length of which is 6-12 mm, and which are selected from at least one of polypropylene fibers and basalt fibers.

[0010] As a preferred improvement, the geopolymer-modified granite residual soil also contains hollow glass microspheres, the volume of which accounts for 0.5-1.5% of the volume of the gel material.

[0011] As a preferred improvement, the geopolymer-modified granite residual soil also includes MgO powder, wherein the amount of MgO powder is 0.1-1.5% of the mass of the gel material.

[0012] As a preferred improvement, the geopolymer-modified granite residual soil also includes ultrafine powder of phosphate rock tailings with hydroxyapatite as the main phase, with an admixture amount of 3-6% of the mass of the gel material.

[0013] As a preferred improvement, the geopolymer-modified granite residual soil, when cured at 20±2℃ and with a relative humidity ≥95% for the first 7 days, exhibits an unconfined compressive strength of 1.5-3.0 MPa after 28 days, a top surface resilient modulus ≥120 MPa, and a permeability coefficient of 10. -6 -10 -7 m / s, UCS retention rate ≥80% after 25 freeze-thaw cycles and 12 wet-dry cycles, 10 5 -10 6 Stiffness retention rate after secondary dynamic load fatigue ≥ 80%; 28-day salt frost grade ≤ 1; surface Na + The precipitation flux is ≤0.2 mg / cm²·28d.

[0014] A method for preparing geopolymer-modified residual granite soil as described above includes the following steps: S1, according to the mass fraction, 35-50 parts of glass ultrafine powder, 20-40 parts of petroleum refining deactivated catalyst powder and 10-35 parts of circulating fluidized bed combustion ash are dry-mixed for 30-60 seconds to form a gel material dry material, and the gel material dry material is mixed with granite residual soil. S2, prepare a carbonate alkali activator solution and spray it evenly onto the mixture of dry material and granite residual soil, and then wet mix it to complete the preparation.

[0015] An application of geopolymer-modified residual granite soil, as described above, is used as roadbed fill material.

[0016] The beneficial effects of this invention are as follows: (1) Significantly suppresses efflorescence and improves surface durability. Low-alkali carbonate is used to excite glass powder to form low-modulus water glass in situ. Combined with ion trapping at zeolite sites of deactivated catalysts in petroleum refining and densification by CFB ash, the soluble Na+ content is significantly reduced. + The driving force of migration and crystallization can control the surface salt frost level to ≤1, avoiding white frost and powdering, and reducing the cost of early maintenance and sealing treatment. (2) Heavy metals are stable in the long term and have high environmental safety. Hydroxyapatite in phosphate mine tailings forms insoluble phosphates with potential heavy metals and is fixed in conjunction with LDH / boehmite and other containment phases; the dense porous structure and wet sealing maintenance reduce the leaching flux, so that the leaching of TCLP / EN12457 is stable below the limit value, which meets the environmental access and operation and maintenance supervision requirements of embankment projects; (3) Excellent overall durability, adaptable to multiple service conditions. The C-(A)-SH and (N,K)-ASH interpenetrating gels generated by the composite system enhance toughness and crack resistance, while the hollow microspheres construct closed microbubbles and fiber bridging inhibits microcrack propagation, enabling the material to withstand 25 freeze-thaw cycles, 12 wet-dry cycles, and 10 [unclear text - possibly related to crack resistance]. 5 -10 6 After secondary dynamic load fatigue, the strength / stiffness retention rate is ≥80%, the cumulative deformation is controlled, and the long-term stability is significantly better than that of the traditional improved system; (4) High-efficiency resource utilization and low-carbon benefits of uncommon solid waste. Using uncommon solid wastes such as decommissioned ultrafine glass powder, deactivated catalysts from petroleum refining, and purified circulating fluidized bed combustion ash as the main components, high-energy-consuming cementitious materials are replaced, expanding the spectrum of solid waste utilization; while ensuring a 28dUCS of 1.5-3.0 MPa and a permeability coefficient of 10... -6 -10 -7 While achieving the performance target of m / s, we aim to reduce carbon emissions and costs throughout the material's lifespan, thus unifying engineering, environmental, and social benefits. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] This embodiment provides a geopolymer-modified granite residual soil, comprising granite residual soil, a gel material, and a carbonate-alkali activator. The amount of gel material is 10-20% of the total mass of the modified dry soil, and the equivalent Na2O generated by the carbonate-alkali activator is 2.5-6.5% of the mass of the gel material. The gel material comprises the following components by weight: 35-50 parts of glass ultrafine powder (WG), 20-40 parts of petroleum refining deactivated catalyst powder (SFCC), and 10-35 parts of circulating fluidized bed combustion ash (CFB) and / or waste incineration bottom ash fine powder (MBA).

[0019] It should be noted that the total weight of the improved dry soil is set according to the actual engineering needs, and is used as the basis for selecting the dosage of the gel material.

[0020] The ultrafine glass powder contains no less than 70 wt% SiO2, has a specific surface area of ​​no less than 500 m² / kg, and a particle size D. 50 It is 10-25μm.

[0021] The total mass percentage of Al2O3 and SiO2 in the petroleum refining deactivated catalyst powder shall not be less than 80%, and the loss on ignition shall not be higher than 8%.

[0022] The circulating fluidized bed combustion ash contains less than 2% CaO and less than 3% SO3 by mass, and less than 2% Cl. - The quality percentage is less than 0.05%.

[0023] The carbonate activator is Na₂CO₃ or a Na₂CO₃ / K₂CO₃ composite carbonate with a Na:K molar ratio of (3-5):1. A small amount of K₂CO₃ can act as an auxiliary activator to reduce the oxidizing effect of Na₂CO₃ alone. + Migration. The solid-to-liquid ratio (including process water) of the gel material mixture is controlled between 0.18 and 0.32, determined in conjunction with the compaction curve. Low-modulus sodium silicate with an equivalent modulus Ms≈1.8-2.6 is formed through the in-situ reaction of WG and Na₂CO₃. The key stoichiometric ratios of the entire system are constrained to an atomic ratio of Si to Al of 1.6-2.8 and a molar ratio of Ca to Si of 0.2-0.8, and soluble Na₂CO₃ is also considered. + The total amount is controlled at a low to medium level (0.18-0.96 wt%) to reduce the driving force of efflorescence.

[0024] As a preferred improvement, the geopolymer gel material may further include the following components: The chopped fibers, comprising 0.15-0.35% of the volume of the gel material, have a length of 6-12 mm and are selected from at least one of polypropylene fibers and basalt fibers. These chopped fibers are used to enhance toughness and resistance to freeze-thaw cycles and salt swelling.

[0025] The ultrafine powder of phosphate rock tailings with hydroxyapatite as the main phase is added at a dosage of 3-6% of the mass of the gel material to form insoluble metal phosphates and perform micro-filling.

[0026] MBA is used to supplement Ca and Si, improve glass phase contribution and early strength, and synergistically form a calcium aluminate carbohydrate-C-(A)-SH / N-(K)-ASH interpenetrating network with Na2CO3. The composition of MBA includes: SiO2 35-55wt%, CaO 15-30wt%, Al2O3 5-18wt%, Fe2O3 1-10wt%, MgO 1-5wt%, SO3 <3wt%, Cl... - Content < 0.05 wt%, LOI (loss on ignition) ≤ 5 wt%; specific surface area ≥ 400 m² 2 / kg, D 50 It is 10-40μm.

[0027] Hollow glass microspheres, wherein the volume of the hollow glass microspheres accounts for 0.5-1.5% of the volume of the gel material.

[0028] MgO powder, wherein the amount of MgO powder is 0.1-1.5% of the mass of the gel material. The MgO powder is selected as lightly calcined / stabilized MgO to achieve micro-expansion control.

[0029] This invention achieves mild and efficient polymerization of aluminum-silicon species through low-alkali carbonate activation. Na₂CO₃ and WG generate low-modulus water glass in situ within the system, maintaining the equivalent silicate modulus (Ms) at a low to medium level of around 2.0. This significantly reduces the amount of soluble Na while ensuring reactivity. + Initial concentration and migration driving force; CFB provides active Ca and promotes C-(A)-SH gel formation, soluble silica species dissolved from WG / MBA / CFB and aluminate ions dissolved from SFCC, in the Na2CO3 / K2CO3 provided by Na + / K + In a weakly to moderately alkaline environment, C-(A)-SH gel polymerizes with in-situ low-modulus water glass to form (N,K)-ASH gel. The C-(A)-SH gel and (N,K)-ASH gel form an interpenetrating network, which improves the gel crosslinking degree and crack resistance, achieving a synergistic effect of strength and volume stability. The zeolite framework of SFCC provides abundant cation exchange sites to trap Na. + / K + Together, they inhibit the migration of alkali metal ions to the surface. Hydroxyapatite in phosphate rock tailings forms insoluble metal phosphates with heavy metals. At the same time, under weakly alkaline conditions, it promotes the formation of layered double hydroxides (LDH) or gibbsite phases, achieving dual stability through chemical fixation and mineral inclusion. Hollow microspheres construct closed microbubbles and form multi-scale crack bridging with short-cut fibers. Combined with low shrinkage ratio and wet sealing curing, they refine and stabilize pore size distribution, taking into account both density and toughness, and improving the resistance to freeze-thaw, fatigue and dry-wet degradation from the microstructure level of the material.

[0030] All raw materials need to be pretreated before addition to reduce impurities and stabilize reactivity. The pretreatment process is as follows: CFB ash undergoes washing, sieving, natural carbonization, and low-temperature drying. The solid-liquid ratio during washing is controlled at 1:3-1:5, and stirring is performed during the washing process. After stirring for 10-20 minutes, sedimentation or filtration is used to remove soluble Cl. - With SO3; sieving is used to remove particles with a diameter >0.6mm; natural carbonization for 7-14 days to dissipate excess CaO and improve volume stability; finally, drying at a low temperature of 60-80℃ to make the CaO content <2%, SO3 content <3%, and Cl content <2%. - Content < 0.05%.

[0031] MBA first undergoes magnetic separation to remove metallic impurities, followed by water washing and aging to reduce the content of chloride salts and free alkali, making its index comparable to that of CFB ash.

[0032] WG improves fineness through ball milling or vertical milling, achieving a specific surface area ≥500m² / kg and D 90 <45μm, and add 0.05%-0.1% dispersant if necessary to control water requirement.

[0033] If SFCC has a high oil content or high organic residual carbon content, it should be calcined at 450-550℃ for 1-2 hours to remove organic matter and subjected to dust removal and protection. (Powder D) 50 The range is controlled between 5-20 μm to ensure both reactivity and safety.

[0034] Phosphate tailings ground to D 50 The thickness is 5-15 μm to enhance interface filling ability and accelerate the formation kinetics of metal phosphates.

[0035] The geopolymer-modified granite residual soil was cured at 20±2℃ with a relative humidity of not less than 95% for the first 7 days.

[0036] The properties of the geopolymer-modified residual granite soil are as follows: In terms of mechanics, the 7-day unconfined compressive strength reaches 0.8-1.5 MPa, the 28-day unconfined compressive strength reaches 1.5-3.0 MPa, and the resilient modulus of the top surface of the subgrade is not less than 120 MPa; In terms of hydraulics, the permeability coefficient is 10. -6 -10 -7 m / s, which can meet the structural objectives of drainage or seepage prevention; In terms of durability, after 25 freeze-thaw cycles and 12 wet-dry cycles, the mass loss is no more than 5%, and the UCS (unconfined compressive strength) retention rate is no less than 80%; after 10 5 -10 6 After several indoor constant or variable amplitude dynamic load fatigue treatments (stress level of 0.1-0.2fc), the stiffness retention rate is not less than 80%. In terms of environmental aspects, leaching tests according to TCLP or EN12457 proved that heavy metal leaching was below the limit, and the surface salt efflorescence level was ≤1; the surface Na content was ≤1 after 28 days. + Precipitation flux ≤ 0.2 mg / cm³ 2 This indicates good resistance to efflorescence; In terms of volume stability, the 28-day shrinkage rate does not exceed 0.05%, and the linear expansion rate does not exceed 0.02%.

[0037] This embodiment also provides a method for preparing the above-mentioned geopolymer-modified granite residual soil, comprising the following steps: S1, according to the mass fraction, 35-50 parts of glass ultrafine powder, 20-40 parts of petroleum refining deactivated catalyst powder and 10-35 parts of circulating fluidized bed combustion ash are dry-mixed for 30-60 seconds to form a gel material dry material, and the gel material dry material is mixed with granite residual soil. S2, prepare a carbonate alkali activator solution and spray it evenly onto the mixture of dry material and granite residual soil, and then wet mix it to complete the preparation.

[0038] This embodiment also provides an application of geopolymer-modified granite residual soil as a roadbed material.

[0039] In actual construction scenarios, the original foundation is first leveled and treated, and then the geopolymer-modified residual granite soil provided by this invention is laid as a filler layer. The thickness of the layer is generally not less than 2.0m, and it can be implemented in sections and layers. A 0.3-0.5m dense layer can be arranged on the top surface, and the cementitious material content is reduced to 10%-12% to balance economy and top surface E value. During construction, the thickness of each layer after compaction is strictly controlled not to exceed 25cm, and the construction moisture content is stabilized at the optimum moisture content wopt±1%. The number of compaction passes and mechanical combination are optimized through test sections to obtain a uniform and sufficient compaction effect. In terms of drainage and sealing... For the surface, side ditches and blind drains are set up on both sides to form an effective drainage system. The slope is covered by spraying or thin-layer sealing, and water-based silane or siloxane spraying can be used to further inhibit early surface alkali migration and rain erosion. In terms of material and structural compatibility, PP or PE-based geosynthetic materials are preferred and alkali immersion-tensile compatibility tests are completed to avoid potential degradation of PET in alkaline environments. In terms of climate and open traffic, the construction period and maintenance measures are adjusted appropriately under low temperature (<5℃) or exposure to direct sunlight (≥35℃) conditions. Loading and traffic can only be allowed when all the release thresholds such as E value, deflection, water content and appearance are met.

[0040] Example 1 This embodiment provides a benchmark geopolymer-modified granite residual soil for use as a secondary highway embankment material in general climatic environments.

[0041] In this embodiment, residual granite soil with a natural moisture content of 16% (particles >31.5mm removed) was selected. The total content of the cementitious material was 15% based on the mass of the improved dry soil. The internal proportions of the cementitious material were: 42% decommissioned glass ultrafine powder (WG), 28% petroleum refining deactivated catalyst powder (SFCC), 25% circulating fluidized bed combustion ash (CFB ash, pretreated by "water washing—screening—natural carbonization—low-temperature drying"), and 5% phosphate rock tailings powder. 0.25% polypropylene short fiber (volume fraction, 9mm length), 1.0% hollow microspheres (volume fraction), and 0.8wt% lightly calcined MgO (as a percentage of the cementitious material) were introduced. The activation system used a Na2CO3 solution, with an equivalent Na2O content of 5% of the cementitious material mass, and no K2CO3 was used for activation. The liquid-to-solid ratio (including process water) was controlled at 0.24 to ensure the mixture reached the optimal moisture content ±1% for heavy compaction tests. Construction follows the process of "centralized mixing → transportation → layered paving → 6-8 passes of vibratory rolling → static final compaction → wet curing for 4 days". After compaction, the thickness of a single layer is ≤25cm, and the compaction degree of each layer is tested to be ≥95% (heavy compaction). The relative humidity is maintained at ≥95% for 7 days before curing, and specimens are left for 7 / 28 / 56 days at 20±2℃.

[0042] Test results: 7-day unconfined compressive strength (UCS) was 1.05 MPa, 28-day was 2.12 MPa, and 56-day was 2.45 MPa; the measured resilient modulus (Evd) of the subgrade top surface was 126-148 MPa; the variable head permeability coefficient was 3.7 × 10⁻⁶. -7 m / s; after 25 freeze-thaw cycles and 12 wet-dry cycles, the mass loss was 2.1% and 2.8%, respectively, and the UCS retention rates were 88% and 85%, respectively; 10 5 After a constant amplitude dynamic load (stress level 0.15fc), the stiffness retention rate was 87%, and the cumulative plastic strain met the project limits; the heavy metals leached by TCLP were below the limits; the surface salt frost level after 28 days was 0-1, and the Na content measured by the filter paper method was [data missing]. + Precipitation flux: 0.08 mg / cm³ 2 No pulverization was observed. The main fill layer of the embankment is 2.0m thick, with a 0.35m denser layer (with the admixture content reduced to 12%) on the top surface. The side ditches and blind ditches on both sides are connected. The slope is sealed with a thin layer once, and traffic is opened after 28 days.

[0043] Example 2 This embodiment provides a cold-region frost-resistant geopolymer-modified granite residual soil for use as a roadbed material for seasonally frozen soil in frigid regions.

[0044] This embodiment selects residual granite soil with a natural moisture content of 14%, and increases the total content of cementitious materials to 18%. The internal composition is: WG 45%, SFCC 30%, CFB ash 20%, phosphate rock tailings 5%; basalt fiber 0.30% (volume fraction, length 12mm), hollow microspheres 1.5% (volume fraction); lightly calcined MgO 1.0wt%. The activation system uses Na2CO3 solution with an equivalent Na2O of 6%, and K2CO3 is added to make the Na:K molar ratio 4:1 to reduce the single Na content. + Migration; L / S controlled at 0.23. During the construction period, the ambient temperature fluctuates between -5 and -5℃ from day to night. A comprehensive approach is adopted, including heating the mixture at the mixing plant to 10-15℃, heat preservation during transportation, and covering the paving with insulation blankets and wet sealing for 7 days. The thickness of a single layer after compaction is ≤22cm.

[0045] Performance results: 7d UCS 1.25MPa, 28d 2.48MPa; Evd 135-160MPa; mass loss after 50 constant temperature-constant load freeze-thaw cycles 4.3%, UCS retention rate 82%; retention rate after 12 dry-wet cycles 84%; 10 6 After fatigue under dynamic load with secondary amplitude variation, the stiffness retention rate is 81%, and the cumulative deformation meets the design requirements; the permeability coefficient is 5.2 × 10⁻⁶. -7 m / s; surface salt frost level ≤ 1; TCLP leaching stability low. This formulation significantly improves freeze-thaw and dynamic load toughness by increasing fiber and microsphere content and enhancing the micro-expansion of Ca, Si and MgO, meeting the requirements of roadbeds in cold regions.

[0046] Example 3 This embodiment provides a heavy-duty traffic fatigue-resistant geopolymer-modified granite residual soil for use as a subgrade material for primary and secondary highways or roads with high logistics traffic.

[0047] This embodiment uses residual granite soil with a natural moisture content of 15%, and the total cementitious material content is 16%. The internal mix proportions are: WG 40%, SFCC 30%, CFB ash 25%, MBA (purified) 5%; phosphate rock tailings were not added (the Ca and Si content was adjusted by the MBA and CFB ash to meet the requirements). The fiber is a blend of PP and basalt, with a total component of 0.30% (PP 0.15% and basalt 0.15%), and lengths of 9mm and 12mm respectively; hollow microspheres 1.0%; MgO 0.5wt%. The activation system has Na2CO3 equivalent to 5% Na2O, Na, K = 5:1; L / S = 0.23. Construction employs centralized mixing and layered paving, with a single layer thickness ≤25cm after compaction. The number of compaction passes was optimized from the test section to 8 passes, and the Evd of the top surface was controlled ≥140MPa; wet curing was performed for 5 days.

[0048] Indoor dynamic load fatigue (0.1-0.2fc, 10) 6After (number of cycles), the stiffness retention rate was 85%, and the cumulative deformation decreased by approximately 22% compared to the baseline model; the 28-day UCS was 2.35 MPa, and the 56-day UCS was 2.62 MPa; the permeability coefficient was 4.4 × 10⁻⁶. -7 m / s; retention rates after 12 wet and dry cycles and 25 freeze-thaw cycles were 86% and 89%, respectively; 28-day salt frost rating was 0-1; TCLP and EN12457 leaching standards were met. In this embodiment, the introduction of MBA balances early strength and structural densification, and the fiber blending improves crack control and fatigue resistance, making it suitable for heavy-duty traffic.

[0049] Example 4 This embodiment provides a geopolymer-modified residual granite soil with high sulfate environment durability, which can be used as a roadbed material in coastal areas with high salt spray and surface / groundwater sulfate content.

[0050] This embodiment uses residual granite soil with a natural moisture content of 17%, and the total amount of cementitious material is 15%. The internal composition is: WG 43%, SFCC 27%, CFB ash 20%, phosphate rock tailings 8% to improve the chemical fixation of heavy metals and soluble salts; hollow microspheres 1.0%, PP fiber 0.20% (volume fraction, length 9mm); MgO 0.6wt%. The activation system uses Na2CO3 equivalent to Na2O 4%, Na, K = 3:1; L / S = 0.25. The CFB ash is strictly washed with water until Cl... - Content <0.03wt%, SO3 <2.5wt%. Construction is the same as the baseline type, but a water-based silane spray is applied to the slope (7 days) and then re-sprayed on 28 days to reduce surface ion migration and rain erosion driven by sea wind.

[0051] Test results: 28dUCS = 2.06 MPa; Evd = 128-145 MPa; permeability coefficient = 3.9 × 10⁻⁶ MPa. -7 m / s; Accelerated sulfate attack test (15 cycles of immersion-drying in 5% Na2SO4 solution) showed volume stability with a mass loss of 2.6%; Retention rates after 25 freeze-thaw cycles and 12 wet-dry cycles were 86% and 84%, respectively; Surface salt bloom rating was 0-1; Cl - The permeability equivalence index is low; the release of heavy metals (TCLP) and ions (EN12457) both meet the limits. By increasing the proportion of phosphate rock tailings and using double sealing, this embodiment maintains good durability under sulfate and salt spray environments.

[0052] Example 5 This embodiment provides an economical geopolymer-modified granite residual soil for use as a backfill material for municipal roads / field roads.

[0053] To balance economic efficiency and low carbon footprint, this embodiment selects residual granite soil with a natural moisture content of 18%, reducing the total cementitious material content to 12%. Internal mix design: WG 41%, SFCC 26%, CFB ash 28%, phosphate rock tailings 5%; MBA is not used. Fiber 0.20% (PP), hollow microspheres 0.8%, MgO 0.5wt%. The activation system has an equivalent Na2CO3 content of 3.5% Na2O and no K2CO3; L / S = 0.26. In-situ mixing (reverse mixing ≥2 times) and centralized moisture content monitoring for online correction are employed. Layered paving and compaction are used, with a single layer thickness ≤25cm after compaction; wet curing for 4 days.

[0054] Results: 7dUCS 0.85 MPa, 28d 1.72 MPa; Evd 120-132 MPa; permeability coefficient 6.1 × 10⁻⁶ -7 m / s; the retention rates after 25 freeze-thaw cycles and 12 wet-dry cycles were 82% and 81%, respectively; 10 5 Secondary dynamic load stiffness retention rate is 83%; salt frost grade is 1, with no pulverization observed; TCLP / EN12457 standard is met. This embodiment significantly reduces material usage and carbon emissions while ensuring the E-value and durability baseline of the subgrade top surface, making it suitable for backfilling of municipal roads and access roads.

[0055] The mechanical, durability, hydraulic and environmental properties of the above five embodiments are detailed in Tables 1-4.

[0056] Table 1 Mechanical Properties Table 2 Durability Indicators Table 3 Hydraulic Indicators Table 4 Environmental Indicators As can be seen from the table above, by adjusting the proportions of different raw materials, roadbed materials that meet the needs of different scenarios can be obtained.

[0057] The embodiments of the present invention have been described above, but the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit of the present invention, and all of these forms are within the protection scope of the present invention.

Claims

1. A geopolymer modified granite residual soil, characterised in that, The geopolymer modified granite residual soil comprises granite residual soil, gel material and carbonate alkali activator, the content of the gel material is 10-20% of the total mass of the dry soil after modification, the equivalent Na2O mass generated by the carbonate alkali activator is 2.5-6.5% of the mass of the gel material, wherein the gel material comprises the following components in parts by weight: 35-50 parts of glass ultrafine powder, 20-40 parts of petroleum refining deactivated catalyst powder and 10-35 parts of circulating fluidized bed combustion ash and / or waste incineration bottom slag fine powder.

2. The geopolymer-modified granite residual soil according to claim 1, characterized in that, The SiO2 content of the glass superfine powder is ≥70wt%, the specific surface area is ≥500m2 / kg, and the D 50 value is 10-25μm; the D 50 value of the petroleum refining deactivated catalyst powder is 5-20μm, the loss on ignition is ≤8%, and the total amount of Al2O3 and SiO2 is ≥80wt%; the CaO content of the circulating fluidized bed combustion ash is <2wt%, the SO3 content is <3wt%, the Cl - content is <0.05wt%; the SiO2 content of the waste incineration bottom ash superfine powder is 35-55wt%, the CaO content is 15-30wt%, the SO3 content is <3wt%, and the Cl - content is <0.05wt%; and the carbonate alkali activator is Na2CO3 or a composite carbonate of Na2CO3 / K2CO3 with a molar ratio of Na:K of (3-5):

1.

3. The geopolymer-modified granite residual soil according to claim 1, characterized in that, The total Si and Al atom ratio in all raw materials of the geopolymer modified granite residual soil is 1.6-2.8, the Ca and Si mole ratio is 0.2-0.8, and the soluble Na + The total amount is 0.18-0.96wt%.

4. The geopolymer-modified granite residual soil according to claim 1, characterized in that, The geopolymer modified granite residual soil further comprises chopped fibers, the volume of the chopped fibers is 0.15-0.35% of the volume of the gel material, the length of the chopped fibers is 6-12 mm, and the chopped fibers are selected from at least one of polypropylene fibers and basalt fibers.

5. The geopolymer-modified granite residual soil according to claim 1, wherein, The geopolymer modified granite residual soil further comprises hollow glass microbeads, the volume of the hollow glass microbeads is 0.5-1.5% of the volume of the gel material.

6. The geopolymer-modified granite residual soil according to claim 1, wherein, The geopolymer modified granite residual soil further comprises MgO powder, the content of the MgO powder is 0.1-1.5% of the mass of the gel material.

7. The geopolymer-modified granite residual soil according to claim 1, wherein, The geopolymer modified granite residual soil further comprises phosphorite tailings ultrafine powder with a main phase of hydroxyapatite, the content of the phosphorite tailings ultrafine powder is 3-6% of the mass of the gel material.

8. The geopolymer-modified granite residual soil according to claim 1, wherein, The geopolymer-modified granite residual soil was cured at 20±2℃ and with a relative humidity of ≥95% for the first 7 days. After 28 days, its unconfined compressive strength was 1.5-3.0 MPa, its top surface resilient modulus was ≥120 MPa, and its permeability coefficient was 10. -6 -10 -7 m / s, UCS retention rate ≥80% after 25 freeze-thaw cycles and 12 wet-dry cycles, 10 5 -10 6 Stiffness retention rate after secondary dynamic load fatigue ≥ 80%; 28-day salt frost grade ≤ 1; surface Na + The precipitation flux is ≤0.2 mg / cm²·28d.

9. A method of preparing a geopolymer-modified granite residual soil according to any one of claims 1 to 8, characterised in that, The method comprises the following steps: S1, dry mixing 35-50 parts of glass ultrafine powder, 20-40 parts of petroleum refining deactivated catalyst powder and 10-35 parts of circulating fluidized bed combustion ash for 30-60 seconds to form gel material dry material, and mixing the gel material dry material with granite residual soil; S2, preparing a carbonate alkali activator solution and uniformly spraying the solution into the mixture of the dry material and the granite residual soil and wet mixing to complete the preparation.

10. Use of geopolymer-modified granite residual soil according to any one of claims 1 to 8, characterized in that, The geopolymer modified granite residual soil is used as roadbed filler.

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