A method for mix proportion design of solid waste cementitious material considering characteristics of loess

Abstract

The present application relates to a kind of design methods of solid waste cementitious material considering loess characteristics, belong to solid waste utilization and building material technical field.The method includes: with calcareous solid waste, silico-aluminous solid waste, gypsum and cement clinker as raw material, with mechanical property as index, initial solid waste cementitious material is selected;The active oxide content of loess is obtained;The dosage of calcareous solid waste and silico-aluminous solid waste is adjusted, so that the silicon-aluminum ratio and silicon-calcium ratio of loess reinforced by cementitious material are same with initial solid waste cementitious material, and the optimal dosage of calcareous solid waste and silico-aluminous solid waste is obtained;The SO3 content of gypsum and loess is measured respectively, so that the SO3 content of reinforced loess is same with initial solid waste cementitious material, and the optimal dosage of gypsum is obtained;The mix proportion of solid waste cementitious material is obtained.The mechanical property of solid waste cementitious material reinforced loess designed by the present application is better, and the optimal mix proportion of solid waste cementitious material can be quickly designed according to the clay content and SO3 content of loess in different regions.

Description

Technical Field

[0001] This invention belongs to the field of solid waste utilization and building materials technology, and relates to a mix design method for solid waste cementitious materials that takes into account the characteristics of loess. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Collapsible loess is characterized by its large porosity, under-compactment, and collapsibility. When exposed to water, it easily undergoes significant subsidence and deformation under the combined pressure of its own weight and the saturated weight of the overlying soil, or a combination of its own weight and additional pressure, causing damage or destruction to buildings and structures. Therefore, when using loess as a raw material for building foundations or roadbeds, it is necessary to reinforce the loess with cementing materials to eliminate its collapsibility and improve its strength. For better environmental benefits, solid waste cementing materials are often used.

[0004] Currently, the common practice is to first prepare mortar or mortar specimens of solid waste cementitious materials using several solid waste raw materials, and then determine the optimal mix ratio of the solid wastes based on the maximum compressive strength of the specimens. The solid waste cementitious material with the optimal mix ratio is then used for loess reinforcement. This mix design method ensures that the reaction system of the solid waste cementitious material is in an optimal oxide ratio state, but it only considers the properties of the solid waste cementitious material itself and does not take into account the properties of loess. Because loess contains a large amount of clay minerals that can participate in volcanic ash reactions, and also contains soluble sulfates (mainly Na₂SO₄, MgSO₄, and CaSO₄), which can participate in the reaction of the solid waste cementitious material to form expansive ettringite, the composite reaction system of clay minerals-solid waste cementitious material-sulfate formed after the solid waste cementitious material with the optimal mix ratio is not in an optimal oxide ratio state, thus affecting the performance of the solid waste cementitious material in reinforcing loess.

[0005] Alternatively, response surface methodology or orthogonal design can be used, taking the raw material content of solid waste cementitious materials as an influencing factor and the mechanical properties (mainly 28-day compressive strength) of the loess reinforced by solid waste cementitious materials as the response value, to determine the optimal mix proportion of the solid waste cementitious materials. This method considers the influence of the loess itself on the performance of the solid waste cementitious materials, but the results obtained are only applicable to loess with a fixed composition in a specific area where mix proportion design experiments are actually conducted. Because the properties of loess composition vary greatly with spatial distribution, and loess in different regions exhibits differences in clay minerals and collapsibility, each type of loess requires independent solid waste cementitious material mix design. The design process requires 28 days of curing for each type of solid waste cementitious material reinforced loess, resulting in a long design cycle and a large workload, thus lacking universality. This method is not suitable for construction projects with large areas and long mileage. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a mix design method for solid waste cementitious materials that takes into account the characteristics of loess. In the design process of the solid waste cementitious material mix ratio, optimizing the mix ratio based on the clay mineral and SO3 content in the loess can achieve excellent reinforcement effects; furthermore, this method can quickly obtain the corresponding mix ratios for different types of loess, exhibiting greater versatility.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A mix design method for solid waste cementitious materials that takes into account the characteristics of loess includes the following steps:

[0009] S1. Prepare solid waste cementitious materials to be screened using calcareous solid waste, siliceous aluminous solid waste, gypsum and cement clinker as raw materials. Use mechanical properties as an indicator to screen and obtain the initial optimal mix ratio of each raw material. The cementitious materials are the initial solid waste cementitious materials.

[0010] S2. Measure the active oxide content of the raw materials in the initial solid waste cementitious material, and calculate the silicon-aluminum ratio and silicon-calcium ratio of the initial solid waste cementitious material;

[0011] S3. Measure the clay content of loess, measure the clay mineral reaction rate of clay particles, and obtain the active oxide content of loess.

[0012] S4. Adjust the dosage of calcareous solid waste and siliceous aluminous solid waste so that the silica-alumina ratio and silica-calcium ratio of the reinforced loess obtained after mixing the cementitious material with the loess are the same as those of the initial solid waste cementitious material, thereby obtaining the optimized dosage of calcareous solid waste and siliceous aluminous solid waste.

[0013] S5. Measure the SO3 content of gypsum and loess respectively, so that the SO3 content of the reinforced loess obtained after mixing the cementitious material with loess is the same as that of the initial solid waste cementitious material, and obtain the optimized dosage of gypsum.

[0014] S6. Based on the optimized dosage of calcareous solid waste, silica-alumina solid waste and gypsum, obtain the mix proportion of solid waste cementitious material for reinforcing loess, taking into account the characteristics of loess.

[0015] The beneficial effects of this invention are as follows:

[0016] 1. This invention addresses the problem that clay minerals and sulfates in loess participate in the hydration and volcanic ash reactions of solid waste cementitious materials, thus affecting the original oxide ratio in the reaction system. It proposes a mix design method for solid waste cementitious materials that considers the characteristics of loess: First, an initial optimal mix design method for the initial solid waste cementitious material with the best mechanical properties is obtained. Then, the method maintains the silica-alumina ratio, silica-calcium ratio, and SO3 content in the initial solid waste cementitious material reaction system as indicators. The amount of activatable solid waste (including calcareous and silica-alumina solid waste) is adjusted according to the active oxide content of the clay minerals in the loess, and the amount of industrial by-product gypsum (desulfurization gypsum) is adjusted according to the SO3 content in the loess, thus determining the optimized optimal mix design method for solid waste cementitious materials considering the characteristics of loess. Compared to the solid waste cementitious material with the initial optimal mix design method, loess reinforced with the solid waste cementitious material considering the characteristics of loess obtained using the optimized optimal mix design method exhibits higher mechanical properties and demonstrates the advantages of directional design.

[0017] 2. This invention is applicable to various types of loess in different regions. After completing the mix design optimization steps S1 to S6 for a type of loess, for loess in other regions, only the clay content and SO3 content of the loess need to be tested. The amount of solid waste material to be added to the loess can be quickly calculated through steps S4 to S5. There is no need to repeat the mechanical property test of solid waste cementitious material to reinforce loess, which saves curing time and workload. It has the advantages of universality, modularity and rapid design.

[0018] 3. This invention focuses on the sulfate composition and clay particles in loess, and separates the clay particles from the loess. Based on the mineral composition of the clay particles, the reaction rate of clay minerals, and the clay particle content, the active oxide content in the loess is calculated. Clay particles are taken as the component in loess that has the greatest impact on the active oxide content. This invention can accurately evaluate the impact of loess on the reaction system during the reinforcement of loess with solid waste cementitious materials, and improve the accuracy of the optimization results. Attached Figure Description

[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0020] Figure 1 This is a flowchart illustrating Embodiment 1 of the present invention. Detailed Implementation

[0021] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0023] In the following content, the percentages of dosage and content are all mass percentages.

[0024] One or more embodiments of the present invention provide a mix design method for solid waste cementitious materials that takes into account the characteristics of loess, comprising the following steps:

[0025] S1. Prepare solid waste cementitious materials to be screened using calcareous solid waste, siliceous aluminous solid waste, gypsum and cement clinker as raw materials. Use mechanical properties as an indicator to screen and obtain the initial optimal mix ratio of each raw material. The cementitious materials are the initial solid waste cementitious materials.

[0026] S2. Measure the active oxide content of the initial solid waste cementitious material raw material, and calculate the silicon-aluminum ratio and silicon-calcium ratio of the initial solid waste cementitious material;

[0027] S3. Measure the clay content of loess, measure the clay mineral reaction rate of clay particles, and obtain the active oxide content of loess.

[0028] S4. Adjust the dosage of calcareous solid waste and siliceous aluminous solid waste so that the silica-alumina ratio and silica-calcium ratio of the reinforced loess obtained after mixing the cementitious material with the loess are the same as those of the initial solid waste cementitious material, thereby obtaining the optimized dosage of calcareous solid waste and siliceous aluminous solid waste.

[0029] S5. Measure the SO3 content of gypsum and loess respectively, so that the SO3 content of the reinforced loess obtained after mixing the cementitious material with loess is the same as that of the initial solid waste cementitious material, and obtain the optimized dosage of gypsum.

[0030] S6. Based on the optimized dosage of calcareous solid waste, silica-alumina solid waste and gypsum, obtain the mix proportion of solid waste cementitious material for reinforcing loess, taking into account the characteristics of loess.

[0031] In the above process, the initial optimal mix proportion with the best mechanical properties is obtained without considering loess. The cementitious material that meets the initial optimal mix proportion is the initial solid waste cementitious material, and the silicon-aluminum ratio and silicon-calcium ratio at this time are obtained. Then, the clay particles in the loess are measured separately to obtain the content of active oxides and SO3 in the loess. While ensuring that the silicon-aluminum ratio, silicon-calcium ratio and SO3 content are the same as the initial solid waste cementitious material, the dosage of each solid waste raw material relative to the loess is adjusted, and the optimized mix proportion of each raw material is obtained based on the optimized dosage obtained by adjustment. The cementitious material that meets the optimized mix proportion is the solid waste cementitious material that takes into account the characteristics of loess. When using the solid waste cementitious material that takes into account the characteristics of loess to reinforce loess, higher mechanical properties can be obtained than when using the initial solid waste cementitious material to reinforce loess.

[0032] Optionally, in S1, the mechanical properties include unconfined compressive strength; the 28-day unconfined compressive strength of the initial solid waste cementitious mortar specimens is tested according to the standard "Test Method for Strength of Cement Mortar (ISO Method)" (GB / T 17671-2021) to determine the initial optimal mix proportion.

[0033] Optionally, in S1, calcareous solid waste and silicoaluminous solid waste are reactivatable solid wastes; reactivatable solid wastes contain active or potentially active SiO2, Al2O3, and CaO, and the content of active SiO2, active Al2O3, and active CaO can be increased through mechanical grinding, high-temperature heating, etc., thereby improving the reactivity of reactivatable solid wastes; calcareous solid wastes can provide calcium, including one or more of blast furnace slag, steel slag, and furnace slag; silicoaluminous solid wastes can provide silicon and aluminum, including one or more of fly ash, tailings (selected from one or more of iron tailings, copper tailings, and gold tailings), coal gangue, red mud, and silica fume; gypsum is selected as industrial by-product gypsum, including one or more of desulfurized gypsum, phosphogypsum, citric acid gypsum, fluorogypsum, salt gypsum, monosodium glutamate gypsum, copper gypsum, and titanium gypsum.

[0034] Optionally, in S1, the siliceous aluminous solid waste is selected as iron tailings and fly ash; the calcareous solid waste is selected as blast furnace slag; and the gypsum is selected as desulfurized gypsum. The initial optimal mix proportions include: the mix proportions of iron tailings, blast furnace slag, fly ash, desulfurized gypsum, and cement clinker. Iron tailings are solid waste generated after mineral processing, mainly composed of quartz, hematite, siderite, and aluminosilicates (mica, clay minerals, feldspar), etc.; blast furnace slag is a byproduct of blast furnace ironmaking, consisting of granular material mainly composed of silicates and aluminosilicates formed by the reaction of impurities such as silica and alumina in iron ore with lime, etc.; fly ash is fine ash and bottom ash collected from the flue gas of coal-fired boilers; desulfurized gypsum is a byproduct of boiler flue gas desulfurization, mainly composed of calcium sulfate dihydrate; iron tailings, blast furnace slag, fly ash, desulfurized gypsum, and cement clinker are selected as the mix proportions. Blast furnace slag, fly ash, and other solid wastes contain active oxides (active SiO2, active Al2O3, and active CaO), which can undergo pozzolanic or hydration reactions. Cement clinker not only provides active oxides but also produces Ca(OH)2 after hydration, providing an alkaline environment for the pozzolanic reaction of solid wastes. Iron tailings, blast furnace slag, fly ash, and cement clinker form CSH and CASH gels during the reaction, playing a cementing role in solid waste cementitious materials. Desulfurized gypsum provides CaSO4, which does not participate in the pozzolanic reaction but reacts further with the reaction intermediate CAH of solid waste cementitious materials to form expansive ettringite (AFt), playing a densifying role in solid waste cementitious materials. All raw materials are processed to a specific surface area of ​​300 m². 2 / kg~400m 2 / kg, to fully release its reactivity.

[0035] Optionally, in S1, the initial optimal mix proportion of various raw materials in the initial solid waste cementitious material is determined by response surface methodology. The amount of each raw material in the solid waste cementitious material under the initial optimal mix proportion is the initial optimal amount. The amount of cement clinker in the initial solid waste cementitious material (i.e., the mass percentage of cement clinker in the initial solid waste cementitious material) is a fixed value between 15% and 25%. The amounts of calcareous solid waste and siliceous aluminous solid waste in the solid waste cementitious material are taken as influencing factors, and gypsum is used to make up the total amount of raw materials to 100%.

[0036] Optionally, in S2, SiO2, Al2O3, and CaO in calcareous solid waste, siliceous aluminous solid waste, and cement clinker are determined by XRF method. The active oxide content in calcareous solid waste and siliceous aluminous solid waste is calculated by the active oxide index, and all oxides in cement clinker are active oxides. Here, active oxides refer to oxides that participate in the reaction; the active oxide index refers to the proportion of oxides that participate in the reaction to the total amount of such oxides.

[0037] Specifically, active oxides in calcareous and aluminosilicate solid wastes can react with OH groups generated during cement hydration. -The reaction occurs, and according to the standard "Pozzolanic Blend Materials for Cement" (GB / T 2847-2022), the 28-day activity index of calcareous solid waste and silica-alumina solid waste are tested respectively. The 28-day activity index can be used to measure the active oxide index of this type of solid waste.

[0038] Optionally, in S2, the proportion of active SiO2 to total SiO2 is the active SiO2 index, the proportion of active Al2O3 to total Al2O3 is the active Al2O3 index, and the proportion of active CaO to total CaO is the active CaO index. The active SiO2 index, active Al2O3 index, and active CaO index of this type of solid waste are set to be the same, all equal to the 28-day activity index. Then, the contents of various active oxides in calcareous solid waste and siliceous aluminous solid waste can be obtained through equations (2-1) to (2-3).

[0039]

[0040] In the formula: subscript i Represents calcareous solid waste or silica-alumina solid waste; C i (SiO2), C i (Al2O3) and C i (CaO) represents respectively i The content (%) of SiO2, Al2O3 and CaO in the sample; AI i Represent i 28d activity index (%); C i (SiO2) act , C i (Al2O3) act , C i (CaO) act Represent i The content (%) of active SiO2, active Al2O3, and active CaO in the sample.

[0041] Optionally, in S2, the silicon-aluminum ratio refers to the ratio of the total active SiO2 content in calcareous solid waste, siliceous-aluminous solid waste, and cement clinker obtained by formula (2-4) to the total active Al2O3 content obtained by formula (2-5), as shown in formula (2-7); the silicon-calcium ratio refers to the ratio of the total active SiO2 content in calcareous solid waste, siliceous-aluminous solid waste, and cement clinker obtained by formula (2-4) to the total active CaO content obtained by formula (2-6), as shown in formula (2-8); since the main component of gypsum is CaSO4, and the CaO in it does not participate in the pozzolanic reaction, the CaO in desulfurized gypsum is not included in the calculation of active oxide content in S2.

[0042]

[0043] In the formula: subscript CM Represents the initial solid waste cementitious material; C CM (SiO2) act , C CM (Al2O3) act , C CM (CaO) act These represent the total active SiO2 content, total active Al2O3 content, and total active CaO content (%) in the initial solid waste cementitious material; subscripts i Represents calcareous solid waste or silica-alumina solid waste; C i (SiO2) act , C i (Al2O3) act , C i (CaO) act Represent i The content (%) of active SiO2, active Al2O3, and active CaO in the sample; R i represent i The initial optimal dosage (%); the subscript cement represents cement clinker; C cement (SiO2), C cement (Al2O3) C cement (CaO) represents the content (%) of SiO2, Al2O3 and CaO in cement clinker; R cement The initial optimal admixture of cement clinker is a fixed value between 15% and 25%. R S / ARepresents the silicon-aluminum ratio under the initial optimal mix proportion (i.e., the initial solid waste cementitious material); R S / C This represents the silicon-to-calcium ratio under the initial optimal mix proportion (i.e., the initial solid waste cementitious material).

[0044] Optionally, in S3, clay particles in loess are collected and oriented sections of clay soil samples are prepared; cement clinker is added to the clay particles and cement clinker is used to reinforce the clay soil.

[0045] XRD patterns of two types of oriented sections were obtained, and the reaction amount of clay minerals that react with cement clinker in the clay particles was determined, and the reaction rate of clay minerals was further obtained. Clay particles (soil particles <0.002mm) are the main carriers and enrichment sites of clay minerals in loess. Therefore, clay minerals in loess can be analyzed by separating clay particles from loess.

[0046] Specifically, clay particles in loess are separated and collected using a sedimentation siphon method, including:

[0047] (1) Remove organic matter: Weigh out the air-dried loess, put it into a beaker, and slowly add 20-30% hydrogen peroxide solution in small amounts. After no more bubbles are produced, heat the beaker at a low temperature (<70℃) on a hot plate to drive away the residual hydrogen peroxide and decompose any unreacted organic matter.

[0048] (2) Removal of calcium carbonate cement: Slowly add 0.8~1 mol / L HCl solution to the loess in the beaker with a dropper. When no more bubbles emerge from the loess-acid mixture, wash the loess repeatedly by "centrifugation-discarding the supernatant-resuspending with distilled water" until the supernatant is neutral when tested with pH paper. Dry the washed loess sample at 100~105℃ and crush it for later use.

[0049] (3) Add 40-50g of treated loess to 800-900mL of 20℃ distilled water and 15-20mL of 3-4% sodium hexametaphosphate solution, and stir at high speed for 10-15 minutes to ensure that all loess agglomerates are broken up and a uniform loess suspension is formed; quickly rinse the loess suspension and transfer it to a settling tank, and make up the volume with 20℃ distilled water.

[0050] (4) According to Stokes' Law, it is calculated that in water at 20℃, it takes 8 hours for a particle with a diameter of 0.002mm to settle 10cm. Therefore, the settling cylinder is placed in a constant temperature water bath at 20℃ and left to stand for 8 hours. Then, the loess suspension 10cm below the original liquid surface is sucked out by a siphon tube in 1~2 minutes. After that, 20℃ distilled water is added back to the settling cylinder to the mark line when the volume is fixed in step (3). The process of stirring, standing and siphoning is repeated 2~3 times to ensure that all clay particles are extracted.

[0051] (5) Let the siphoned loess suspension stand and let it settle naturally for at least 3 days; pour off the supernatant, put the concentrated clay slurry at the bottom into the oven to dry, and you can get a pure clay soil sample.

[0052] Optionally, in S3, the clay minerals include kaolinite, montmorillonite, and illite, according to the "X-ray Diffraction Analysis Methods for Clay Minerals and Common Non-Clay Minerals in Sedimentary Rocks" (SY / T According to 5163-2018, three types of oriented slices of clay samples were prepared: natural oriented slices (N slices), ethylene glycol saturated slices (EG slices), and high-temperature slices. The XRD patterns of the three types of oriented slices were measured and analyzed to determine the contents of kaolinite, montmorillonite, and illite in the clay samples. Following the same method, three types of oriented slices of cement clinker-reinforced clay samples were prepared and the contents of kaolinite, montmorillonite, and illite in the cement clinker-reinforced clay samples were determined. The difference between the clay mineral content in the oriented slices of the clay samples and the clay mineral content in the oriented slices of the cement clinker-reinforced clay samples is the reaction amount of the clay minerals. Then, the ratio of the reaction amount of clay minerals to the original amount of clay minerals in the clay was calculated to obtain the clay mineral reaction rate, as shown in Equation (3-1).

[0053]

[0054] In the formula: subscript j Represents kaolinite, montmorillonite, or illite; α j represent j Clay mineral reaction rate (%); C j (clay) represents the clayey soil sample. j Content (%) C j (Solid) represents the cement clinker-reinforced clay sample. j The content (%).

[0055] Optionally, in S3, the active oxides of loess include active SiO2 and active Al2O3. Since clay minerals such as kaolinite, montmorillonite, and illite are mainly composed of silicates, their main chemical components are SiO2 and Al2O3, and the CaO content is extremely low, only the amount of SiO2 and Al2O3 involved in the reaction is analyzed: it is assumed that in an alkaline environment, SiO2 and Al2O3 in clay minerals dissolve in equal proportions and react with OH-. - If a reaction occurs, the reaction rate of the clay minerals... αMultiplying by the median value of the SiO2 content range of kaolinite, montmorillonite, or illite in clay minerals, the content of active SiO2 in kaolinite, montmorillonite, and illite can be obtained. Similarly, the content of active Al2O3 in kaolinite, montmorillonite, and illite can be obtained, as shown in formulas (3-2) to (3-3). Then, according to formulas (3-4) to (3-5), the content of active oxides in the three clay minerals (kaolinite, montmorillonite, and illite) is multiplied by the proportion of clay minerals in the clay particles and then added together to obtain the total content of active SiO2 and active Al2O3 in the clay particles, and further the total content of active oxides in loess is obtained. Similar to S2, active SiO2 and active Al2O3 refer to the oxides that participate in the reaction.

[0056]

[0057] In the formula: subscript j Represents kaolinite, montmorillonite, or illite; C j (SiO2) act , C j (Al2O3) act Represent j The content (%) of active SiO2 and active Al2O3 in the sample; α j represent j Clay mineral reaction rate (%); β j (SiO2), β j (Al2O3) respectively represent j The median (%) of the SiO2 and Al2O3 content ranges in the sample. C clay (SiO2) act , C clay (Al2O3) act The values ​​represent the contents (%) of active SiO2 and active Al2O3 in the clay sample, respectively. C j (clay) represents the clayey soil sample. j The content (%).

[0058] Optionally, in S3, the clay content in loess is determined by the pipette method according to the standard "Standard for Geotechnical Testing Methods" (GB 50123-2019); the active oxide content in loess can be obtained by multiplying the clay content in loess by the active oxide content in the clay; among them, the CaO content of clay minerals in loess is extremely low and can be ignored.

[0059] Optionally, in S4, when solid waste cementitious materials are used to reinforce loess, the total active SiO2 content, the total active Al2O3 content, and the total active CaO content in the reinforced loess obtained after mixing the solid waste cementitious materials with loess are obtained from equations (4-1) to (4-3); correspondingly, the silicon-aluminum ratio and silicon-calcium ratio of the reinforced loess obtained after mixing the solid waste cementitious materials with loess are calculated according to equations (4-4) to (4-5).

[0060]

[0061] In the formula: C total (SiO2) act , C total (Al2O3) act and C total (CaO) act The values ​​represent the total active SiO2 content, total active Al2O3 content, and total active CaO content (%) of the reinforced loess obtained after mixing solid waste cementitious materials with loess. m Represents the clay content (%) in loess; n This represents the amount of solid waste cementitious material used when reinforcing loess, i.e., the mass ratio of solid waste cementitious material to dry loess soil (%). C clay (SiO2) act , C clay (Al2O3) act The values ​​represent the contents (%) of active SiO2 and active Al2O3 in the clay sample, respectively. C CM-优 (SiO2) act , C CM-优 (Al2O3) act and C CM-优 (CaO) act The values ​​represent the contents (%) of active SiO2, active Al2O3, and active CaO in the reinforced loess obtained by mixing solid waste cementitious materials with loess. R S / A The silica-alumina ratio represents the reinforced loess obtained by mixing solid waste cementitious materials with loess. R S / C The silica-calcium ratio represents the reinforced loess obtained by mixing solid waste cementitious materials with loess.

[0062] Referring to equations (2-4) to (2-6), the calculation formulas (4-6) to (4-8) for each active oxide in the solid waste cementitious material considering loess characteristics were obtained. When the solid waste cementitious material considering loess characteristics, obtained from calcareous solid waste and silicoaluminous solid waste as raw materials, is used to reinforce loess, the silica-alumina ratio and silica-calcium ratio of the reinforced loess obtained after mixing with loess are equal to the silica-alumina ratio and calcium-silicon ratio under the initial optimal mix ratio obtained in S2. The calculation method for the optimal dosage of calcareous solid waste and silicoaluminous solid waste relative to loess in the solid waste cementitious material considering loess characteristics is as follows: Simultaneously solving equations (4-4) to (4-8), and substituting the values ​​of the silica-alumina ratio and silica-calcium ratio in S2 into equations (4-4) to (4-5), the optimal dosage of calcareous solid waste and silicoaluminous solid waste relative to loess in the solid waste cementitious material considering loess characteristics is obtained. r i .

[0063]

[0064] In the formula: n This represents the amount of solid waste cementitious material used when reinforcing loess, i.e., the mass ratio of solid waste cementitious material to dry loess soil (%). C CM-优 (SiO2) act , C CM-优 (Al2O3) act , C CM-优 (CaO) act The subscripts represent the percentage (%) of active SiO2, active Al2O3, and active CaO in solid waste cementitious materials considering loess characteristics. i Represents calcareous solid waste or silica-alumina solid waste; C i (SiO2), C i (Al2O3) C i (CaO) represents respectively i Content of SiO2, Al2O3, and CaO in the medium (%); r i represent i Optimal admixture ratio (%) relative to loess; subscript cement represents cement clinker; C cement (SiO2), C cement (Al2O3) C cement (CaO), C cement(Fe2O3) represents the content (%) of SiO2, Al2O3, CaO and Fe2O3 in cement clinker; R cement This represents the initial optimum dosage of cement clinker. The dosage of cement clinker in solid waste cementitious materials considering the characteristics of loess is the same as the initial optimum dosage, which is a fixed value between 15% and 25%.

[0065] Optionally, in S5, the SO3 content in loess and the SO3 content in gypsum are determined by XRF method. The total SO3 in loess is used to replace the equivalent amount of SO3 provided by gypsum to obtain the optimal dosage of gypsum in solid waste cementitious materials considering the characteristics of loess, as shown in formula (5-1):

[0066]

[0067] In the formula: R FGD-优 The optimal dosage (%) of gypsum in solid waste cementitious materials considering the characteristics of loess is determined. R FGD The initial optimal dosage (%) of gypsum in initial solid waste cementitious materials; C loess (SO3) represents the SO3 content (%) in loess. n This represents the amount of solid waste cementitious material used when reinforcing loess, i.e., the mass ratio of solid waste cementitious material to dry loess soil (%). C FGD (SO3) represents the SO3 content (%) in gypsum; 170 represents the molecular weight of CaSO4·2H2O, and 80 represents the molecular weight of SO3.

[0068] Optionally, in S6, based on S4~S5 and according to Equation (6-1), the optimal dosage of calcareous solid waste and siliceous aluminum solid waste considering loess characteristics is calculated. Combined with the optimal dosage of desulfurized gypsum in solid waste cementitious materials considering loess characteristics and the dosage of cement clinker in solid waste cementitious materials considering loess characteristics (fixed at 20%), the optimal mix proportion of each raw material is obtained.

[0069]

[0070] In the formula: subscript i Representing calcareous solid waste and silica-alumina solid waste; R i-优 Represent i Optimized dosage (%) of solid waste cementitious materials considering loess characteristics; r i represent i Optimal admixture ratio (%) relative to loess; R cementThe initial optimal dosage of cement clinker is the same as the initial optimal dosage, which is a fixed value between 15% and 25% in solid waste cementitious materials that take into account the characteristics of loess. R FGD-优 The optimal dosage (%) of desulfurized gypsum in solid waste cementitious materials considering the characteristics of loess is determined. n The amount of solid waste cementitious material used in loess reinforcement, taking into account the characteristics of loess, is the mass ratio of solid waste cementitious material to dry loess soil (%).

[0071] Optionally, it also includes S7: selecting loess from other locations, determining the clay content and obtaining the active oxide content of the loess from other locations, and testing the SO3 content of the loess from other locations; substituting the active oxide content and SO3 content of the loess from other locations into S4~S5 to obtain the mix proportion of the solid waste cementitious material considering the characteristics of loess for reinforcing the loess from other locations.

[0072] The present invention will be further described below with reference to specific embodiments.

[0073] Example 1

[0074] A mix design method for solid waste cementitious materials that takes into account the characteristics of loess, such as... Figure 1 As shown, it includes the following steps:

[0075] S1. Using three types of reactivatable solid waste (iron tailings, blast furnace slag, and fly ash), one type of industrial by-product gypsum (desulfurization gypsum), and cement clinker as raw materials, a solid waste cementitious material to be screened was prepared. All raw materials were processed to a specific surface area of ​​350±50 m². 2 / kg, with the cement clinker content in the solid waste cementitious material to be screened fixed at 20%, the content of iron tailings, blast furnace slag, and fly ash in the solid waste cementitious material to be screened were taken as influencing factors. The content of iron tailings in the solid waste cementitious material to be screened included three levels: 10%, 20%, and 30%; the content of blast furnace slag in the solid waste cementitious material to be screened included three levels: 20%, 30%, and 40%; and the content of fly ash in the solid waste cementitious material to be screened included three levels: 10%, 20%, and 30%. The content was supplemented to 100% with the addition of desulfurized gypsum. The Box-Benhnken model of response surface methodology was used to design the experimental scheme. The 28-day compressive strength of the mortar specimen of the solid waste cementitious material to be screened was used as the response value. The experimental factors were coded as shown in Table 1.

[0076] Table 1. Influencing Factor Coding and Level Table

[0077]

[0078] The design of the response surface methodology includes 17 sets of tests, as shown in Table 2. According to the standard "Test Method for Strength of Cement Mortar (ISO Method)" (GB / T 17671-2021), mortar specimens were prepared by replacing cement with the solid waste cementitious materials represented by each test scheme in Table 2. After curing for 28 days, the unconfined compressive strength of the mortar specimens was tested. The results of the 28-day unconfined compressive strength are shown in Table 2. Among them, the schemes with 20% iron tailings, 30% blast furnace slag, and 20% fly ash were used as the center points of the response surface methodology. The center points were repeated 5 times (including test numbers 2, 5, 6, 10, and 17) to evaluate the test error.

[0079] Table 2 Response Surface Methodology Test Scheme and Compressive Strength Results

[0080]

[0081] The experimental results were analyzed, and the quadratic polynomial regression equation of the response surface model between the measured values ​​of the influencing factors and the response values ​​is shown below:

[0082] Y =-1.4625+0.32675A+1.36825B+0.723C-4.12×10 -17 AB-0.00125AC-0.00075BC-0.0162A 2 -0.0157B 2 -0.01795C 2 .

[0083] Analysis of variance was performed on the response surface model, and the results are shown in Table 3. Table 3 shows that the 28-day unconfined compressive strength response surface model of the solid waste cementitious materials to be screened... P The value <0.0001 is highly significant; the lack-of-fit term is not significant, indicating that the proportion of abnormal errors in the process of fitting the quadratic polynomial regression equation to the experimental data is small, and the 28-day unconfined compressive strength response surface model is reliable.

[0084] Table 3. Results of Analysis of Variance

[0085]

[0086] Based on the "Optimization-Numerical" module of the data analysis software Design Expert, the goal was to obtain the maximum 28-day unconfined compressive strength of the solid waste cementitious material to be screened. The initial optimal dosages of iron tailings, blast furnace slag, and fly ash in the solid waste cementitious material were determined. Combined with the dosages of desulfurized gypsum and cement clinker, the initial optimal dosages of all raw materials were obtained (see Table 4): iron tailings 11.2%, blast furnace slag 38.9%, fly ash 20.4%, desulfurized gypsum 9.5%, and cement clinker 20.0%. These dosage ratios represent the initial optimal mix proportions. Under these initial optimal mix proportions, the predicted initial 28-day compressive strength of the solid waste cementitious material is 36.0 MPa.

[0087] Table 4 Initial Optimal Dosage

[0088]

[0089] The initial solid waste cementitious material was prepared based on the initial optimal dosage, and its 28-day unconfined compressive strength was remeasured, which was 36.3 MPa. The deviation from the predicted value was small, indicating the reliability of the response surface model and the initial optimal mix proportion.

[0090] S2. The oxide (including SiO2, Al2O3 and CaO) content of the raw materials of the initial solid waste cementitious material, namely iron tailings, blast furnace slag, fly ash and cement clinker, was measured by XRF method. The results are shown in Table 5.

[0091] Table 5. Oxide Content of Iron Tailings, Blast Furnace Slag, Fly Ash, and Cement Clinker

[0092]

[0093] According to the standard GB / T 2847-2022 "Pozzolanic Blends for Cement", the 28-day activity indices of iron tailings, blast furnace slag, and fly ash were tested. The results were as follows: 76.2% for iron tailings, 98.7% for blast furnace slag, and 79.4% for fly ash. The active SiO2, active Al2O3, and active CaO indices of blast furnace slag were set to be the same as those of blast furnace slag, and the active SiO2, active Al2O3, and active CaO indices of fly ash were also set to be the same as their 28-day activity indices. The active SiO2, active Al2O3, and active CaO indices of fly ash were set to be the same as their 28-day activity indices. The SiO2 index, active Al2O3 index, and active CaO index are the same as their 28-day activity index; as shown in equations (2-1) to (2-3), the content of oxides in each raw material in Table 5 is multiplied by the 28-day activity index of that raw material to obtain the content of active oxides in each raw material. All oxides in cement clinker are active oxides, as shown in Table 6. Since the main component of desulfurized gypsum is CaSO4, and the CaO in it does not participate in the pozzolanic reaction, the CaO in desulfurized gypsum is not included in the calculation of the active oxide content of the initial solid waste cementitious material.

[0094]

[0095] In the formula: subscript i Represents iron tailings, blast furnace slag, or fly ash; C i (SiO2), C i (Al2O3) and C i (CaO) represents respectively i The content (%) of SiO2, Al2O3 and CaO in the sample; AI i Represent i 28d activity index (%); C i (SiO2) act , C i (Al2O3) act , C i (CaO) act Represent i The content (%) of active SiO2, active Al2O3, and active CaO in the sample.

[0096] Table 6. Content of active oxides in iron tailings, blast furnace slag, fly ash, and cement clinker.

[0097]

[0098] As shown in equations (2-4) to (2-6), the active SiO2 content in Table 6 is multiplied by the initial optimal dosage of the raw material in Table 4, and then the results are added together to obtain the total active SiO2 content of the initial solid waste cementitious material. The total active Al2O3 content and the total active CaO content of the initial solid waste cementitious material are obtained by the same method, and the results are shown in Table 7. Then, as shown in equations (2-7) to (2-8), the silicon-aluminum ratio and silicon-calcium ratio of the initial solid waste cementitious material are calculated, and the results are shown in Table 8.

[0099]

[0100] In the formula: subscript CM Represents the initial solid waste cementitious material; C CM (SiO2) act , C CM (Al2O3) act , C CM (CaO) act These represent the total active SiO2 content, total active Al2O3 content, and total active CaO content (%) in the initial solid waste cementitious material; subscripts i Represents iron tailings, blast furnace slag, or fly ash; C i (SiO2) act , C i (Al2O3) act , C i (CaO) act Represent i The active SiO2 content, active Al2O3 content, and active CaO content (%) in the sample. R i represent i The initial optimal dosage (%); the subscript cement represents cement clinker; C cement (SiO2), C cement (Al2O3) C cement (CaO) represents the SiO2 content, Al2O3 content, and CaO content (%) in cement clinker, respectively. R cement The initial optimal admixture content of cement clinker is fixed at 20%. R S / A The silicon-to-aluminum ratio represents the initial solid waste cementitious material; R S / C The silicon-to-calcium ratio represents the initial solid waste cementitious material.

[0101] Table 7. Content of active oxides in initial solid waste cementitious materials

[0102]

[0103] Table 8. Silicon-aluminum ratio and silicon-calcium ratio of initial solid waste cementitious materials

[0104]

[0105] S3.1 Separating and collecting clay particles from loess using a sedimentation siphon method, including the following steps:

[0106] (1) Remove organic matter: Weigh out the air-dried loess, put it into a beaker, and slowly add 30wt% hydrogen peroxide solution in small amounts. After no more bubbles are produced, heat the beaker at a low temperature (<70℃) on a hot plate to drive away the residual hydrogen peroxide and decompose any unreacted organic matter.

[0107] (2) Removal of calcium carbonate cement: Slowly add 1 mol / L HCl solution to the loess in the beaker with a dropper. When no more bubbles emerge from the loess-acid mixture, wash the loess repeatedly by centrifuging, discarding the supernatant, and resuspending it with distilled water until the supernatant is neutral when tested with pH paper. Dry the washed loess sample at 105℃ and crush it for later use.

[0108] (3) Add 50g of treated loess to 900ml of 20℃ distilled water and 20mL of 4% sodium hexametaphosphate solution, and stir at high speed for 10 minutes to ensure that all loess agglomerates are broken up and a uniform loess suspension is formed; quickly rinse the loess suspension and transfer it to a 1000mL settling cylinder, and make up to 1000mL with 20℃ distilled water.

[0109] (4) According to Stokes' law, it is calculated that it takes 8 hours for a particle with a diameter of 0.002 mm to settle 10 cm in water at 20℃. Place the settling cylinder in a constant temperature water bath at 20℃ and let it stand. After 8 hours, use a siphon tube to suck out the loess suspension 10 cm below the original liquid surface within 1~2 minutes. Add 20℃ distilled water to the settling cylinder to the 1000mL mark and repeat the process of stirring, standing and siphoning twice to ensure that all clay particles are extracted.

[0110] (5) Collect the siphoned loess suspension in a large container and let it stand for at least 3 days to allow it to settle naturally; pour off the supernatant and put the concentrated clay slurry at the bottom into an oven (105℃) to dry it, and you can get a pure clay soil sample.

[0111] S3.2 Prepare oriented sections of clay samples, and add cement clinker to the clay to prepare oriented sections of cement clinker-reinforced clay samples. Determine the clay mineral reactivity rate in loess based on the oriented sections of the clay samples and the cement clinker-reinforced clay samples. Specifically:

[0112] Pure clay soil samples were used, and the optimal moisture content w (14.8%) and maximum dry density ρ (1.78 g / cm³) of the loess were determined. 3 Clay soil specimens were prepared and designated as Specimen 1. These specimens were cured for 28 days under standard conditions (temperature 20±2℃, relative humidity above 95%). The cement clinker was mixed with the clay soil sample using 6% cement (the mass ratio of cement to dry loess), a common practice in conventional roadbed engineering for cement-reinforced loess. The optimal moisture content w (14.8%) and maximum dry density ρ (1.78 g / cm³) of the loess were determined. 3 Specimens of cement clinker-reinforced clay were prepared and designated as Specimen 2, and cured under standard conditions for 28 days. According to the "X-ray Diffraction Analysis Method for Clay Minerals and Common Non-Clay Minerals in Sedimentary Rocks" (SY / T 5163-2018), three types of oriented sections were prepared for Specimen 1 and Specimen 2: naturally oriented section (N section), ethylene glycol saturated section (EG section), and high-temperature section. The XRD patterns of the three types of oriented sections for Specimen 1 and Specimen 2 were measured and analyzed to determine the contents of kaolinite, montmorillonite, and illite in Specimen 1 and Specimen 2. The decrease in content of kaolinite in Specimen 2 compared to Specimen 1 represents the reaction amount of this clay mineral. The ratio of the reaction amount of this clay mineral to the total amount of this type of clay mineral in Specimen 1 was calculated using formula (3-1), obtaining the reaction rates of the three clay minerals in the clay that can react with cement clinker. The calculation results are shown in Table 9.

[0113]

[0114] In the formula: subscript j Represents kaolinite, montmorillonite, or illite; α j represent j Clay mineral reaction rate (%); C j (clay) represents the clayey soil sample. j Content (%) C j (Solid) represents the solidified clay sample containing cement clinker. j Content (%) C j (sticky)- C j (Solid) represents the amount of clay minerals reacted (%).

[0115] Table 9 Clay Mineral Reactivity Table

[0116]

[0117] S3.3 Calculation of the content of active oxides in clay minerals. Since clay minerals such as kaolinite, montmorillonite, and illite are mainly composed of silicates, with SiO2 and Al2O3 as the main chemical components and very little CaO, only the role of SiO2 and Al2O3 in the reaction is analyzed. The content of SiO2 and Al2O3 in kaolinite, montmorillonite, and illite is measured respectively, and the median value of the content range is taken. The SiO2 and Al2O3 that can be dissolved in kaolinite are defined as active SiO2 and active Al2O3, and the dissolution ratio of SiO2 and Al2O3 is the same, which is equal to the clay mineral reaction of kaolinite. Similarly, the SiO2 and Al2O3 that can dissolve in montmorillonite are defined as active SiO2 and active Al2O3, and their dissolution ratio is the same, which is equal to the clay mineral reaction rate of montmorillonite; the SiO2 and Al2O3 that can dissolve in illite are defined as active SiO2 and active Al2O3, and their dissolution ratio is the same, which is equal to the clay mineral reaction rate of illite. The active oxide content in the clay sample is calculated according to formulas (3-2) to (3-3), and the results are shown in Table 10; similar to S2, active SiO2 and active Al2O3 refer to the oxides that participate in the reaction.

[0118]

[0119] In the formula: subscript j Represents kaolinite, montmorillonite, or illite; C j (SiO2) act , C j (Al2O3) act Represent j The content (%) of active SiO2 and active Al2O3 in the sample; α j represent j Clay mineral reaction rate (%); β j (SiO2), β j (Al2O3) respectively represent j The median (%) of the SiO2 and Al2O3 content ranges in the sample. C clay (SiO2) act , C clay (Al2O3) act The values ​​represent the contents (%) of active SiO2 and active Al2O3 in the clay sample, respectively. Cj (clay) represents the clayey soil sample. j The content (%).

[0120] Table 10 Content of reactive oxides in clay minerals participating in the reaction

[0121]

[0122] Multiply the active oxide content of each clay mineral in Table 10 by the reaction rate of each clay mineral in Table 9, and then add them together to obtain the active oxide content in the clay particles. The results are shown in Table 11.

[0123] Table 11 Content of active oxides in clay particles

[0124]

[0125] S3.4 According to the pipette method in the standard "Standard for Geotechnical Testing Methods" (GB 50123-2019), the clay content m in loess was measured to be 19.4%. Multiplying the clay content in loess by the content of active oxides in the clay particles yields the content of active oxides in the loess. The CaO content of clay minerals in loess is extremely low and can be ignored; therefore, it is unnecessary to calculate the content of active CaO in loess.

[0126] S4. Based on the content of active oxides in loess, obtain the total active SiO2 content, the total active Al2O3 content and the total active CaO content in the reinforced loess obtained after mixing the solid waste cementitious material with loess during the process of solid waste cementitious material reinforcement of loess according to formulas (4-1) to (4-3). Accordingly, calculate the silicon-aluminum ratio and silicon-calcium ratio of the reinforced loess obtained after mixing the solid waste cementitious material with loess according to formulas (4-4) to (4-5).

[0127]

[0128] In the formula: C total (SiO2) act , C total (Al2O3) act , C total (CaO) act The values ​​represent the total active SiO2 content, total active Al2O3 content, and total active CaO content (%) of the reinforced loess obtained after mixing solid waste cementitious materials with loess. m Represents the clay content (%) in loess; n This represents the amount of solid waste cementitious material used when reinforcing loess, i.e., the mass ratio of solid waste cementitious material to dry loess soil (%). Cclay (SiO2) act , C clay (Al2O3) act The values ​​represent the contents (%) of active SiO2 and active Al2O3 in the clay sample, respectively. C CM-优 (SiO2) act , C CM-优 (Al2O3) act , C CM-优 (CaO) act The values ​​represent the contents (%) of active SiO2, active Al2O3, and active CaO in the reinforced loess obtained by mixing solid waste cementitious materials with loess. R S / A The silica-alumina ratio represents the reinforced loess obtained by mixing solid waste cementitious materials with loess. R S / C The silica-calcium ratio represents the reinforced loess obtained by mixing solid waste cementitious materials with loess.

[0129] Based on equations (2-4) to (2-6), calculation formulas (4-6) to (4-8) for various active oxides in solid waste cementitious materials considering loess characteristics were obtained. When solid waste cementitious materials considering loess characteristics, obtained by mixing iron tailings, blast furnace slag, and fly ash, are used to reinforce loess, the silica-alumina ratio and silica-calcium ratio of the reinforced loess obtained after mixing with loess are equal to the silica-alumina ratio and calcium-silicon ratio under the initial optimal mix ratio obtained in S2. The calculation method for the optimal dosage of iron tailings, blast furnace slag, and fly ash relative to loess in solid waste cementitious materials considering loess characteristics is as follows: Simultaneously combining equations (4-4) to (4-8), and substituting the values ​​of the silica-alumina ratio and silica-calcium ratio in S2 into equations (4-4) to (4-5), the optimal dosage of iron tailings, blast furnace slag, and fly ash relative to loess in solid waste cementitious materials considering loess characteristics is obtained. r i .

[0130]

[0131] In the formula: n This represents the amount of solid waste cementitious material used when reinforcing loess, i.e., the mass ratio of solid waste cementitious material to dry loess soil (%). C CM-优 (SiO2) act , C CM-优 (Al2O3) act , C CM-优 (CaO) actThe subscripts represent the percentage (%) of active SiO2, active Al2O3, and active CaO in solid waste cementitious materials considering loess characteristics. i Represents iron tailings, blast furnace slag, or fly ash; C i (SiO2), C i (Al2O3) C i (CaO) represents respectively i Content of SiO2, Al2O3, and CaO in the medium (%); r i represent i Optimal admixture ratio (%) relative to loess; subscript cement represents cement clinker; C cement (SiO2), C cement (Al2O3) C cement (CaO), C cement (Fe2O3) represents the content (%) of SiO2, Al2O3, CaO and Fe2O3 in cement clinker; R cement This represents the initial optimum dosage of cement clinker. The dosage of cement clinker in solid waste cementitious materials considering the characteristics of loess is the same as the initial optimum dosage, which is fixed at 20%.

[0132] Substituting the values ​​of the silicon-aluminum ratio and silicon-calcium ratio from Table 8 in S2 into equations (4-4) to (4-5), we obtain equations (4-9) to (4-10); substituting equations (4-9) to (4-10) and the content of active oxides in the raw materials into equations (4-6) to (4-8), we obtain a system of four linear equations in four variables, equations (4-11) to (4-13), where the four unknowns are respectively n , r IOT , r BFS , r FA .

[0133]

[0134] In the formula: n This represents the amount of solid waste cementitious material used when reinforcing loess, i.e., the mass ratio of solid waste cementitious material to dry loess soil (%). C CM-优 (SiO2) act , C CM-优 (Al2O3) act ,C CM-优 (CaO) act The values ​​represent the contents (%) of active SiO2, active Al2O3, and active CaO in solid waste cementitious materials considering the characteristics of loess. r IOT , r BFS , r FA These represent the optimized admixture amounts (%) of iron tailings, blast furnace slag, and fly ash relative to loess.

[0135] The dosage of solid waste cementitious materials was set separately when reinforcing loess. n The optimal dosages of iron tailings, blast furnace slag, and fly ash relative to loess were calculated by combining equations (4-11) to (4-12) for 6%, 7%, and 8%, as shown in Table 12.

[0136] Table 12 Optimal dosage of solid waste under different dosages of solid waste cementitious materials in loess reinforcement

[0137]

[0138] The amount of solid waste cementitious material used in loess reinforcement n At 7%, the ratio of iron tailings to fly ash is relatively closer, which is conducive to the co-processing and utilization of iron tailings and fly ash, and to the synergistic improvement of the utilization rate of iron tailings and fly ash; therefore, 7% was selected. n The optimal admixture amounts of iron tailings, blast furnace slag, and fly ash relative to loess are 7%.

[0139] S5. Using XRF method, the SO3 content in desulfurized gypsum was found to be 54.45%, and the SO3 content in loess was found to be 0.22%. Based on the amount of solid waste cementitious material set in S4 for loess reinforcement... n The dosage is 7%, with SO3 from the loess replacing an equivalent amount of SO3 provided by the desulfurization gypsum, thus reducing the amount of desulfurization gypsum accordingly. Based on equation (5-1), the optimal dosage of desulfurization gypsum in solid waste cementitious materials considering the characteristics of loess is calculated. R FGD-优 The concentration was 9.38%, which is lower than the initial doping concentration in Table 4.

[0140]

[0141] In the formula: R FGD-优 The optimal dosage (%) of desulfurized gypsum in solid waste cementitious materials considering the characteristics of loess is determined. R FGD The initial optimal dosage of desulfurized gypsum (%). Cloess (SO3) represents the SO3 content (%) in loess. n This represents the amount of solid waste cementitious material used in loess reinforcement, i.e., the mass ratio of solid waste cementitious material to dry loess soil (%), which is set to 7% here; C FGD (SO3) represents the SO3 content in desulfurized gypsum; 170 represents the molecular weight of CaSO4·2H2O, and 80 represents the molecular weight of SO3.

[0142] S6. Based on the optimized dosages of iron tailings, blast furnace slag, and fly ash relative to loess, according to equation (6-1), the optimal dosages of iron tailings, blast furnace slag, and fly ash in solid waste cementitious materials considering loess characteristics are obtained; combined with the optimal dosage of desulfurized gypsum determined in S5. R FGD-优 With the cement clinker content fixed at 20%, the optimal dosage of various raw materials for solid waste cementitious materials considering the characteristics of loess was determined, as shown in Table 13.

[0143]

[0144] In the formula: subscript i Represents iron tailings, blast furnace slag, or fly ash; R i-优 Represent i Optimized dosage (%) of solid waste cementitious materials considering loess characteristics; r i represent i Optimal admixture ratio (%) relative to loess; R cement The initial optimal dosage of cement clinker is the same as that in solid waste cementitious materials considering the characteristics of loess, and is fixed at 20%. R FGD-优 The optimal dosage (%) of desulfurized gypsum in solid waste cementitious materials considering the characteristics of loess is 9.38%. n This represents the amount of solid waste cementitious material used in loess reinforcement, that is, the amount of solid waste cementitious material used in loess reinforcement considering the characteristics of loess, that is, the mass ratio of solid waste cementitious material to dry loess soil (%), which has been selected as 7% in S4.

[0145] Table 13 Optimal Mix Proportion of Solid Waste Cementitious Materials Considering Loess Characteristics

[0146]

[0147] In this embodiment, the optimal mix ratio of iron tailings, blast furnace slag, fly ash, desulfurized gypsum and cement clinker in the solid waste cementitious material considering the characteristics of loess is 11.76:48.76:10.10:9.38:20.00.

[0148] The solid waste cementitious material prepared according to the optimized dosage in Table 13 is the solid waste cementitious material considering the characteristics of loess obtained in this embodiment. According to the standard "Standard for Geotechnical Testing Methods" (GB / T 50123-2019), the dosage of solid waste cementitious material for loess reinforcement is 7%, with an optimal moisture content of 14.8% and a maximum dry density of 1.78 g / cm³. 3 Unconfined compressive strength specimens of loess reinforced with solid waste cementitious material were prepared. After curing under standard conditions for 28 days, the 28-day unconfined compressive strength was measured. It can be seen that the 28-day unconfined compressive strength of loess reinforced with solid waste cementitious material that takes into account the characteristics of loess obtained in this embodiment is 1.83 MPa.

[0149] Example 2

[0150] The loess used in Example 1 was named L1. Following step S7, different types of loess were selected from different regions and named L2 to L5 respectively. The clay content and SO3 content in the different types of loess were measured, as shown in Table 14. Figure 1 As shown, using the same iron tailings, blast furnace slag, fly ash, desulfurized gypsum, and cement clinker as in Example 1, and assuming the clay mineral composition in the clay particles of different types of loess is the same, the clay content and SO3 content of different types of loess were tested, and the corresponding active oxide content was determined. The amount of solid waste cementitious material to be used when reinforcing loess was then determined. n The value was 7%. Substituting this value into S4~S5, the optimal dosage and optimal mix ratio of solid waste cementitious materials considering the characteristics of loess were obtained. The results are shown in Table 14.

[0151] Prepare solid waste cementitious materials suitable for loess types L2 to L5 according to the optimized optimal dosage in Table 14; according to the standard "Standard for Geotechnical Testing Methods" (GB / T 50123-2019), use the prepared solid waste cementitious materials with the optimized optimal mix proportions, dry loess soil of types L2 to L5, and water, based on the amount of solid waste cementitious materials used when reinforcing loess. n It has a moisture content of 7%, an optimum moisture content of 14.8%, and a maximum dry density of 1.78 g / cm³. 3 Unconfined compressive strength specimens of reinforced loess were prepared and tested after curing under standard conditions for 28 days. The results are shown in Table 14.

[0152] Table 14. 28-day compressive strength of reinforced loess in this embodiment.

[0153]

[0154] Comparative Example

[0155] According to the initial optimal dosage of the initial solid waste cementitious material in Table 4 of Example 1, the initial solid waste cementitious material was prepared. Following the same specimen preparation method as in Example 2, unconfined compressive strength specimens of reinforced loess were prepared using one of the loess types L1 to L5 and the initial solid waste cementitious material as raw materials. After curing under standard conditions for 28 days, the 28-day unconfined compressive strength of the reinforced loess was tested. The results are summarized in Table 15 with those of Example 2.

[0156] Table 15 Technical Effects of Example 2 and Comparative Example 1

[0157]

[0158] It can be seen that, compared with the unoptimized initial solid waste cementitious material, the solidified loess of Example 2 has a higher unconfined compressive strength, that is, the loess reinforced by the solid waste cementitious material that takes into account the characteristics of loess exhibits a better reinforcement effect.

[0159] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for mix proportion design of solid waste cementitious material considering loess characteristics, characterized in that, The method comprises the following steps: S1, preparing a solid waste cementitious material to be screened by taking calcium solid waste, silico-alumina solid waste, gypsum and cement clinker as raw materials, screening the initial optimum mixing ratio of each raw material according to mechanical properties as an index, and the cementitious material is an initial solid waste cementitious material; In S1, the calcium solid waste includes one or more of blast furnace slag, steel slag and slag; the silico-alumina solid waste includes one or more of fly ash, tailings, coal gangue, red mud and silica ash; the gypsum is selected as industrial by-product gypsum, including one or more of desulfurization gypsum, phosphorus gypsum, citric acid gypsum, fluorine gypsum, salt gypsum, monosodium glutamate gypsum, copper gypsum and titanium gypsum; The initial optimum mixing ratio of various materials is determined by the response surface method; the cement clinker content is a fixed value between 15-25%, the calcium solid waste content in the solid waste cementitious material and the silico-alumina solid waste content in the solid waste cementitious material are taken as influencing factors, and the gypsum is used to supplement the total raw material content to 100%; S2, measuring the active oxide content of the initial solid waste cementitious material raw material, calculating the silicon-aluminum ratio and the silicon-calcium ratio of the initial solid waste cementitious material; S3, measuring the clay content of the loess, measuring the clay mineral reaction rate of the clay, and obtaining the active oxide content of the loess; S4, adjusting the contents of the calcium solid waste and the silico-alumina solid waste, so that the silicon-aluminum ratio and the silicon-calcium ratio of the reinforced loess obtained after the cementitious material is mixed with the loess are the same as those of the initial solid waste cementitious material, and the optimized contents of the calcium solid waste and the silico-alumina solid waste are obtained; S5, respectively measuring the SO3 contents of the gypsum and the loess, so that the SO3 content of the reinforced loess obtained after the cementitious material is mixed with the loess is the same as that of the initial solid waste cementitious material, and the optimized content of the gypsum is obtained; S6, according to the optimized contents of the calcium solid waste, the silico-alumina solid waste and the gypsum, the mixing ratio of the solid waste cementitious material considering the characteristics of the loess for reinforcing the loess is obtained.

2. The method for mix design of solid waste cementitious material considering loess characteristics according to claim 1, characterized in that, In S1, the mechanical properties include unconfined compressive strength. 3.The method of designing the mixture ratio of solid waste cementitious material considering the characteristics of loess according to claim 1, characterized in that, The SiO2, Al2O3 and CaO in the calcium solid waste, the silico-alumina solid waste and the cement clinker are determined by the XRF method, the active oxide content in the calcium solid waste and the silico-alumina solid waste is calculated by the active oxide index, and the oxides in the cement clinker are all active oxides.

4. The mixing ratio design method of the solid waste cementitious material considering the characteristics of the loess according to claim 1, wherein in S2, the silicon-aluminum ratio refers to the ratio of the total active SiO2 content to the total active Al2O3 content in the calcium solid waste, the silico-alumina solid waste and the cement clinker; and the silicon-calcium ratio refers to the ratio of the total active SiO2 content to the total active CaO content in the calcium solid waste, the silico-alumina solid waste and the cement clinker. 5.The method of designing the mixture ratio of solid waste cementitious material considering the characteristics of loess according to claim 1, characterized in that, In S3, the clay particles are collected and directional slices of clay particle soil samples are prepared, the cement clinker is added to the clay particles and directional slices of cement clinker reinforced clay particle soil samples are prepared; XRD patterns of the two types of directional slices are obtained respectively, the clay mineral reaction amount in the clay particles reacting with the cement clinker is determined, and the clay mineral reaction rate is obtained. 6.The method of claim 1, wherein in S3, the clay minerals include kaolinite, montmorillonite and illite; and the active oxides of the loess include active SiO 2 and active Al 2 O 3.

7. The method for mix design of solid waste cementitious material considering loess characteristics according to claim 1, characterized in that, In S3, the active oxide content of the loess is obtained by multiplying the clay content of the loess by the active oxide content of the clay. 8.The method of claim 1, wherein in S5, the SO 3 content of the loess and the SO 3 content of the gypsum are respectively measured by XRF method, and the optimal optimal dosage of the gypsum in the loess-based solid waste cementitious material is obtained by replacing the SO 3 provided by the gypsum with the total SO 3 content of the loess. 9.The method of designing the mixture ratio of solid waste cementitious material considering the characteristics of loess according to claim 1, characterized in that, Further comprising S7, selecting loess at other locations, measuring the clay content and obtaining the active oxide content of the loess at other locations, and testing the SO 3 content of the loess at other locations; and substituting the active oxide content and the SO 3 content of the loess at other locations into S4-S5 to obtain the mix proportion of the loess-based solid waste cementitious material for reinforcing the loess at other locations.

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