Improved red sandstone roadbed filler based on multi-source solid waste and mixing ratio optimization method

Abstract

The application discloses a kind of based on multiple-source solid waste's improved red sandstone roadbed filler and mix proportion optimization method, belong to the field of red sandstone filler green low carbon improvement.Improved red sandstone roadbed filler is red sandstone as improved matrix, with match calcium carbide slag, rice husk ash, fly ash as cementing component preparation, wherein calcium carbide slag provides calcium source and alkaline environment, rice husk ash provides silicon source, fly ash provides aluminum source, three reactions occur in alkaline environment and generate abundant cementing products, realize red sandstone improvement.At the same time, with three cementing component contents as design variable, with bearing ratio, unconfined compressive strength, water stability coefficient as road evaluation index, construct road performance response model, through multi-index optimization, clear cementing component optimization ratio range.The method can exert the synergistic effect of multiple-source solid waste chemical composition, can be optimized according to different application scene performance requirements Ratio, realize red sandstone efficient improvement and multiple-source solid waste high-value utilization, with economic benefit and environmental benefit.

Description

Technical Field

[0001] This invention relates to the field of green and low-carbon improvement technology for red sandstone fillers, and in particular to an improved red sandstone roadbed filler based on multi-source solid waste and a method for optimizing its mix proportion. Background Technology

[0002] Red sandstone strata are widely distributed in the eastern and southern parts of Anhui Province, my country. The cementing material of this type of red sandstone is mainly composed of argillaceous and calcareous components. Due to its high porosity and well-developed fissures, coupled with the fact that its mineral composition is easily affected by weathering, red sandstone is prone to softening and disintegration when exposed to water, resulting in a significant decrease in its mechanical properties, making it unsuitable for direct use as roadbed fill.

[0003] According to the "Anhui Provincial Expressway Network Plan (2020-2035)," large-scale road projects will traverse and be constructed in areas with red sandstone distribution in the future. To implement the concept of green transportation development, roadbed fill materials should prioritize local sourcing to avoid resource waste and increased costs associated with long-distance transportation and replacement. Therefore, if local red sandstone fill materials can be improved using appropriate technologies to meet roadbed filling requirements, significant economic and environmental benefits will be generated.

[0004] Chemical remediation is currently a widely applicable and effective method for remediating red sandstone. In traditional engineering practice, cement or lime is commonly used as remediation materials for red sandstone. Practice has shown that the hydration reaction and ion exchange of cement or lime can effectively improve the deformation characteristics, strength properties, and water stability of red sandstone fillers. However, the production processes of cement and lime consume large amounts of resources and energy, and are accompanied by high carbon emissions, which does not align with the development concept of green and low-carbon road construction.

[0005] Meanwhile, my country's cumulative solid waste stockpile has reached approximately 60 billion tons, with an annual increase of nearly 3 billion tons. The comprehensive utilization rate is low, highlighting the urgent need to cultivate green, efficient, and high-value utilization models for multi-source solid waste. Most solid wastes contain components with cementing functions, such as calcium oxide, silicon dioxide, and alumina. In recent years, an increasing number of geotechnical engineers have begun applying various types of solid waste to the chemical improvement research of special soil and rock masses.

[0006] Calcium carbide slag is a waste residue generated during acetylene production, primarily composed of calcium hydroxide. When used for soil improvement, the increase in the mechanical properties of the improved soil is closely related to the subsequent pozzolanic reaction. If the improved soil system cannot provide sufficient active silica and alumina to meet the needs of the secondary pozzolanic reaction, it will greatly limit the increase in soil strength and long-term service performance. Rice husk ash is a solid waste generated from biomass power plants, containing abundant highly active amorphous silica and possessing potential pozzolanic activity. However, when used alone, rice husk ash has insufficient cementing properties and usually requires activation in a certain alkaline environment, combined with other materials for modification. Fly ash is a solid waste generated from thermal power plants, rich in alumina and silica. It has a relatively mature application in the field of soil and rock improvement; however, it also requires activation in an alkaline environment and combined modification with other materials to fully exert its effects.

[0007] Carbide slag, rice husk ash, and fly ash are three typical solid wastes with huge emissions and low utilization rates, while possessing certain potential cementitious activity. Effectively utilizing these three solid wastes for red sandstone improvement and roadbed filling would undoubtedly bring significant benefits. However, the advantageous cementitious components and their contents differ considerably among these three solid wastes. Furthermore, when used individually, each solid waste exhibits a relatively simple composition of cementitious functional components, with a severe imbalance in the proportions of chemical components such as calcium, silicon, and aluminum. These deficiencies in chemical composition often lead to a lack of theoretical guidance and reliance on experience when using these three solid wastes for soil and rock improvement, hindering the full realization of their effective functional value. Therefore, fully utilizing the advantages of the chemical composition of these three solid wastes to create a synergistic effect when used together, achieving complementary utilization, is of great significance for improving the improvement effect of red sandstone roadbed filling and realizing the efficient and high-value utilization of multi-source solid waste. Summary of the Invention

[0008] To address the aforementioned issues, this invention aims to propose an improved red sandstone roadbed filler based on multi-source solid waste and a method for optimizing its mix proportion. It combines the advantages and disadvantages of carbide slag, rice husk ash, and fly ash in their respective chemical compositions. Carbide slag provides a calcium source and alkaline environment, rice husk ash provides a silicon source, and fly ash provides an aluminum source, thus constructing an improved system with the synergistic effect of multiple solid waste sources. Simultaneously, by establishing a road performance response model for the improved red sandstone filler, the mix proportion parameters of the multi-source solid waste can be rapidly optimized according to the performance requirements of different engineering scenarios, achieving efficient improvement of the red sandstone filler and high-value utilization of the multi-source solid waste.

[0009] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0010] An improved red sandstone roadbed filler based on multi-source solid waste is prepared from red sandstone, carbide slag, rice husk ash and fly ash as raw materials, wherein carbide slag, rice husk ash and fly ash are used as cementing components and red sandstone is used as the matrix to be improved.

[0011] Furthermore, the red sandstone is obtained by crushing, screening, and drying of Class I and II easily disintegrating red sandstone that is not suitable for direct use as roadbed fill material, and the particle size of the red sandstone after treatment is less than 5mm.

[0012] Furthermore, the calcium oxide content in the carbide slag is not less than 90%, which is used to provide a calcium source for the red sandstone improvement system and create an alkaline environment; the silicon dioxide content in the rice husk ash is not less than 70%, which is used to provide a silicon source for the red sandstone improvement system; and the aluminum oxide content in the fly ash is not less than 25%, which is used to provide an aluminum source for the red sandstone improvement system.

[0013] Furthermore, the particle size of the carbide slag, rice husk ash, and fly ash is all less than 0.075 mm to ensure that the cementitious components fully contact and react with the red sandstone matrix.

[0014] To achieve the above objectives, the present invention also provides a method for optimizing the mix proportion of an improved red sandstone roadbed filler based on multi-source solid waste, as described above, comprising the following steps:

[0015] (1) Determine the proportion of cementitious components: The proportion of cementitious components should be controlled between 9% and 18%;

[0016] (2) Design of experimental variables and schemes: Using the content of carbide slag X1, rice husk ash X2, and fly ash X3 in the cementitious components as design variables, design at least 7 sets of experiments, and in each set of experiments, the design variables satisfy X1+X2+X3=1, where X1, X2, and X3 are all non-negative values;

[0017] (3) Preparation of improved filler: Weigh red sandstone, carbide slag, rice husk ash and fly ash according to the design mix ratio, add water with the optimal moisture content and mix evenly to obtain improved red sandstone roadbed filler;

[0018] (4) Testing road performance: The specimens were prepared by static pressure method, cured to the test age according to standard, and the load-bearing ratio CBR, 28-day unconfined compressive strength and water stability coefficient were determined.

[0019] (5) Optimize mix ratio: Based on the performance test results, construct a road performance response model, draw performance contour maps and overlay them to determine the mix ratio optimization range that meets multiple road performance requirements.

[0020] Furthermore, the optimal moisture content and maximum dry density of the modified red sandstone subgrade filler under different mix proportions in step (3) need to be determined by compaction tests in accordance with the "Specifications for Geotechnical Testing of Highways" (JTG3430-2020).

[0021] Furthermore, the determination of bearing ratio (CBR) and 28-day unconfined compressive strength in step (4) should be completed by bearing ratio test and unconfined compressive strength test respectively in accordance with the "Specifications for Testing Geotechnical Engineering for Highways" (JTG3430-2020).

[0022] Furthermore, the formula for calculating the water stability coefficient in step (4) is as follows:

[0023] In the formula, This is the water stability coefficient; The unconfined compressive strength of the specimen under standard curing conditions; The unconfined compressive strength is determined by removing the sample one day before the standard curing period and immersing it in deionized water for 24 hours.

[0024] Furthermore, the functional expression Y(X1, X2, X3) of the improved red sandstone fill road performance response model in step (5) is expressed as:

[0025] In the formula, The model response values ​​for the road performance of the improved red sandstone roadbed fill material - CBR, unconfined compressive strength, and water stability coefficient; These are the individual action coefficients for carbide slag, rice husk ash, and fly ash, respectively. The interaction coefficient between carbide slag and rice husk ash; The interaction coefficient between carbide slag and fly ash; The interaction coefficient between rice husk ash and fly ash; The coefficients of interaction among carbide slag, rice husk ash, and fly ash.

[0026] Furthermore, in step (2), the range of variation for design variables X1 is 0.5-1.0, the range of variation for X2 is 0-0.5, and the range of variation for X3 is 0-0.5, in order to balance the reaction efficiency of the gelling components and cost control.

[0027] The underlying mechanism of this invention:

[0028] The main component of carbide slag is calcium hydroxide, which can provide a calcium source and create an alkaline environment in the red sandstone improvement system. However, it lacks the silicon and aluminum sources required to promote the pozzolanic reaction, resulting in insufficient cementitious properties. Rice husk ash is rich in highly active silica. Although its cementitious properties are not obvious when used alone, it can provide a silicon source for the red sandstone improvement system when used in combination with carbide slag. It can also react with the calcium hydroxide in the carbide slag to form hydrated calcium silicate gel. Fly ash contains a certain amount of alumina. Although its own hydration activity is low, it can provide an aluminum source for the red sandstone improvement system in the alkaline environment provided by carbide slag, promote the pozzolanic reaction, and enrich the formation of gel products (hydrated calcium aluminate and hydrated calcium aluminosilicate). Based on the chemical composition characteristics and advantages of carbide slag, rice husk ash and fly ash, this invention combines the three for the improvement of red sandstone filler. By constructing a response model between the road performance of the improved red sandstone filler and the composition of multi-source solid waste, and using multiple road performance indicators as constraints, the mixing ratio parameters of multi-source solid waste are optimized, thereby achieving efficient improvement of red sandstone filler and high-value utilization of multi-source solid waste.

[0029] Beneficial effects: (1) Based on the chemical improvement of red sandstone filler and the demand for cementing components, this invention analyzes the chemical composition characteristics of carbide slag, rice husk ash, and fly ash, and proposes corresponding improved red sandstone subgrade filler and mix ratio optimization methods. Carbide slag provides calcium source and creates an alkaline environment, and its hydration produces Ca 2+ The water sensitivity of the red sandstone filler is reduced through ion exchange; rice husk ash provides the silicon source, and fly ash provides the aluminum source, both reacting with Ca under alkaline conditions. 2+ A volcanic ash reaction occurs, generating various cementing products that improve the physical and mechanical properties of the red sandstone packing material. This method can effectively and specifically utilize the advantageous cementing functional components of solid waste, enabling different solid wastes to form a synergistic and complementary effect, fully leveraging the functional value of solid waste, and achieving efficient improvement of the red sandstone packing material.

[0030] (2) This invention establishes a response model between the road performance of the improved red sandstone filler and the composition of multi-source solid waste. Based on the performance requirements of different engineering scenarios, and with multiple road performance indicators as constraints, the optimal range of mixing ratio parameters for multi-source solid waste can be optimized and determined. This method not only meets the needs of diversified engineering applications, but also selects the most cost-effective mixing ratio scheme while ensuring that the filler performance meets the standards, thus achieving the optimal match between filler performance and cost.

[0031] (3) This invention applies three typical solid wastes, namely carbide slag, rice husk ash and fly ash, to the preparation of improved red sandstone roadbed filler, realizing "turning waste into treasure" and effectively solving the environmental pollution and resource waste problems caused by the large-scale stockpiling of solid waste; at the same time, the prepared improved red sandstone roadbed filler has strong bearing capacity, high strength and good water stability, which can effectively alleviate the shortage of high-quality filler in road construction in red sandstone areas and achieve the dual goals of high-value utilization of solid waste and green and low-carbon road construction. Attached Figure Description

[0032] 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 undue limitation of the invention. In the drawings:

[0033] Figure 1 This is a map showing the locations of multi-source solid waste batching points in a method for optimizing the mix proportion of improved red sandstone roadbed filler based on multi-source solid waste, as described in an embodiment of the present invention.

[0034] Figure 2 This is a CBR contour map from an embodiment of the present invention, illustrating a method for optimizing the mix proportion of an improved red sandstone roadbed filler based on multi-source solid waste.

[0035] Figure 3 This is a contour map of the 28-day unconfined compressive strength in a mix proportion optimization method for an improved red sandstone roadbed filler based on multi-source solid waste, as described in an embodiment of the present invention.

[0036] Figure 4 This is a contour map of the water stability coefficient in a mix proportion optimization method for an improved red sandstone roadbed filler based on multi-source solid waste, as described in an embodiment of the present invention.

[0037] Figure 5 This refers to the preferred mix proportion range of solid waste raw materials in the mix proportion optimization method for an improved red sandstone roadbed filler based on multi-source solid waste described in this embodiment of the invention. Detailed Implementation

[0038] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0039] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0040] Example 1

[0041] An improved red sandstone roadbed filler based on multi-source solid waste is prepared from red sandstone, carbide slag, rice husk ash and fly ash as raw materials, wherein carbide slag, rice husk ash and fly ash are used as cementing components and red sandstone is used as the matrix to be improved.

[0042] This embodiment combines the advantages and disadvantages of carbide slag, rice husk ash and fly ash in their respective chemical compositions. By using carbide slag to provide calcium and an alkaline environment, rice husk ash to provide silicon, and fly ash to provide aluminum, an improved system with synergistic effects of multiple solid waste sources is constructed.

[0043] In a specific example, the red sandstone is obtained by crushing, screening and drying of Class I and II easily disintegrating red sandstone that is not suitable for direct use as roadbed fill material, and the particle size of the red sandstone after treatment is less than 5mm.

[0044] This embodiment limits the red sandstone to Class I or II easily disintegrating red sandstone with a particle size of less than 5 mm to ensure that the red sandstone meets the improvement requirements, guarantee the improvement effect and stability, and avoid the improvement effect being affected by the quality of the red sandstone.

[0045] In a specific example, the calcium oxide content in the carbide slag is not less than 90%, which is used to provide a calcium source for the red sandstone improvement system and create an alkaline environment; the silicon dioxide content in the rice husk ash is not less than 70%, which is used to provide a silicon source for the red sandstone improvement system; and the aluminum oxide content in the fly ash is not less than 25%, which is used to provide an aluminum source for the red sandstone improvement system.

[0046] This embodiment specifies the content of key components in carbide slag, rice husk ash, and fly ash to ensure that they can effectively provide calcium, silicon, and aluminum sources, thus guaranteeing the function of the cementitious components.

[0047] In a specific example, the particle size of the carbide slag, rice husk ash, and fly ash is all less than 0.075 mm to ensure that the cementitious components fully contact and react with the red sandstone matrix.

[0048] In this embodiment, the particle size of the three gelling components is limited to less than 0.075 mm to ensure that the components are fully mixed and reacted, thereby improving the improvement effect.

[0049] Example 2

[0050] To achieve the above objectives, this embodiment also provides a method for optimizing the mix proportion of improved red sandstone roadbed filler based on multi-source solid waste, as described above, including the following steps:

[0051] (1) Determine the proportion of cementitious components: The proportion of cementitious components (the ratio of the mass of cementitious components to the mass of the red sandstone matrix to be improved) should be controlled between 9% and 18%;

[0052] (2) Design of experimental variables and schemes: Using the content of carbide slag X1, rice husk ash X2, and fly ash X3 in the cementitious components as design variables, design at least 7 sets of experiments, and in each set of experiments, the design variables satisfy X1+X2+X3=1, where X1, X2, and X3 are all non-negative values;

[0053] (3) Preparation of improved filler: Weigh red sandstone, carbide slag, rice husk ash and fly ash according to the design mix ratio, add water with the optimal moisture content and mix evenly to obtain improved red sandstone roadbed filler;

[0054] (4) Testing road performance: The test specimens were prepared by static pressure method (compaction degree controlled at 96%), and after standard curing to the test age, the bearing ratio CBR, 28-day unconfined compressive strength were measured, and the water stability coefficient was calculated.

[0055] (5) Optimize mix ratio: Based on the performance test results, construct a road performance response model, draw performance contour maps and overlay them to determine the mix ratio optimization range that meets multiple road performance requirements.

[0056] It should be noted that the equation X1+X2+X3=1 represents a 3D coordinate plane of a triangle. Represents the coordinates of any point in this 3D plane, i.e., any combination of carbide slag (calcium source), rice husk ash (silicon source), and fly ash (aluminum source).

[0057] In the specific implementation, based on the road performance response model function of the improved red sandstone filler, contour maps of the road performance of the improved red sandstone filler as a function of the multi-source solid waste composition are plotted in the triangular 3D coordinate plane.

[0058] In a specific example, the optimal moisture content and maximum dry density of the modified red sandstone subgrade filler under different mix proportions in step (3) need to be determined by compaction test in accordance with the "Specifications for Geotechnical Testing of Highways" (JTG3430-2020).

[0059] This embodiment clearly determines the optimum moisture content and maximum dry density according to the "Specifications for Testing Geotechnical Engineering for Highways", ensuring the accuracy and standardization of the test data and providing reliable data support for subsequent preparation and performance testing.

[0060] In a specific example, the determination of bearing ratio (CBR) and 28-day unconfined compressive strength in step (4) needs to be completed by bearing ratio test and unconfined compressive strength test respectively in accordance with the "Specifications for Testing Geotechnical Engineering for Highways" (JTG3430-2020).

[0061] The specified bearing ratio and unconfined compressive strength are tested according to the "Specifications for Testing Geotechnical Engineering for Highways", so that the test results are scientific, accurate and comparable, providing a unified standard for evaluating the performance of improved red sandstone subgrade filler.

[0062] In a specific example, the formula for calculating the water stability coefficient in step (4) is:

[0063] In the formula, This is the water stability coefficient; The unconfined compressive strength of the specimen under standard curing conditions; The unconfined compressive strength is determined by removing the sample one day before the standard curing period and immersing it in deionized water for 24 hours.

[0064] This embodiment provides a formula for calculating the water stability coefficient, unifies the calculation standard, and makes the water stability performance under different mix proportions comparable, providing accurate data for performance evaluation and mix proportion optimization.

[0065] In a specific example, the functional expression Y(X1, X2, X3) of the performance response model of the improved red sandstone fill road in step (5) is expressed as:

[0066] In the formula, The model response values ​​for the road performance of the improved red sandstone roadbed fill material - CBR, unconfined compressive strength, and water stability coefficient; The individual action coefficients are carbide slag (calcium source), rice husk ash (silicon source), and fly ash (aluminum source), respectively. The interaction coefficient between carbide slag (calcium source) and rice husk ash (silicon source); The interaction coefficient between carbide slag (calcium source) and fly ash (aluminum source); The interaction coefficient between rice husk ash (silicon source) and fly ash (aluminum source); The coefficients represent the interaction of calcium carbide slag (calcium source), rice husk ash (silicon source), and fly ash (aluminum source).

[0067] This embodiment constructs a road performance response model, quantifies the relationship between various factors, provides a tool for analyzing and optimizing mix proportions, can predict road performance under different mix proportions, and improves R&D efficiency.

[0068] In a specific example, in step (2), the range of variable X1 is 0.5-1.0, the range of X2 is 0-0.5, and the range of X3 is 0-0.5, so as to balance the reaction efficiency of the gelling components and cost control.

[0069] This embodiment limits the range of design variables, narrows the scope of experiments and optimizations, improves R&D efficiency, reduces costs, focuses on better mix proportions, and enhances practicality and economic value.

[0070] Example 3

[0071] In its specific implementation, this embodiment relates to a method for optimizing the mix proportion of a modified red sandstone roadbed filler based on multi-source solid waste, which specifically includes the following steps:

[0072] (1) Raw material selection and testing

[0073] The red sandstone was selected from a representative section of the Xuancheng-Jingxian Expressway in southern Anhui Province, and X-ray diffraction analysis showed that its main mineral components and mass fractions were: 25.9% quartz, 37.1% chlorite, 13.9% albite, 1.4% siderite, and 21.7% muscovite. The red sandstone was crushed, dried to constant weight, and sieved through a 5mm sieve before being used as filler for the roadbed to be improved. Calcium carbide slag, rice husk ash, and fly ash were dried and sieved through a 0.075mm sieve as cementing components. X-ray fluorescence spectroscopy analysis showed that the calcium carbide slag contained 92.05% CaO, the rice husk ash contained 75% SiO2, and the fly ash contained 29% Al2O3.

[0074] (2) Design of mix proportion scheme for multi-source solid waste modified red sandstone roadbed filler

[0075] The incorporation rate of the cementitious component (mass of cementitious component / mass of the matrix to be improved) was set at 12%. Based on the different proportions of carbide slag, rice husk ash, and fly ash, a total of 11 groups of improved red sandstone filler samples were designed. The specific distribution of the solid waste cementitious component composition is shown in Table 1 and... Figure 1 .exist Figure 1 In the diagram, the three coordinate axes of the triangle represent the content of the three types of solid waste. The coordinates of any point within the diagram are ( X 1, X 2, X 3) A combination of three types of solid waste, satisfying the following conditions: .

[0076] Table 1. Composition Design of Multi-Source Solid Waste

[0077]

[0078] (3) Preparation and road performance testing of improved red sandstone filler

[0079] according to Figure 1 Based on the mix proportions designed in Table 1, and in accordance with the "Specifications for Geotechnical Testing of Highways" (JTG3430-2020), the optimum moisture content and maximum dry density of the modified red sandstone filler under different mix proportions were determined through compaction tests. Under the optimum moisture content conditions, according to the designed mix proportions, the corresponding masses of red sandstone, carbide slag, rice husk ash, fly ash, and water were weighed and thoroughly mixed to obtain the modified red sandstone subgrade filler.

[0080] Modified red sandstone subgrade fill samples were prepared using the static compaction method, with a compaction degree controlled at 96%. After standard curing to the test age, CBR and 28-day unconfined compressive strength tests were conducted according to the "Specifications for Geotechnical Testing of Highways" (JTG3430-2020). The water stability coefficient was calculated using the following formula. ,

[0081]

[0082] In the formula, This is the water stability coefficient; The unconfined compressive strength of the specimen under standard curing conditions; The unconfined compressive strength is determined by removing the sample one day before the standard curing period and immersing it in deionized water for 24 hours.

[0083] (4) Construction of road performance response model for improved red sandstone filler and optimization of mix proportion parameters

[0084] Based on the measured values ​​of various road performance characteristics of the improved red sandstone filler, the contents of carbide slag (calcium source), rice husk ash (silicon source), and fly ash (aluminum source) were used as design variables (denoted as ). X 1. X 2. X 3) Construct an improved performance response model for road use of red sandstone fill material, and its functional expression is as follows: Y ( X 1. X 2. X 3) Represented as:

[0085]

[0086] In the formula, The model response values ​​are for the road performance (CBR, unconfined compressive strength, and water stability coefficient) of the improved red sandstone roadbed fill material. The individual action coefficients are carbide slag (calcium source), rice husk ash (silicon source), and fly ash (aluminum source), respectively. The interaction coefficient between carbide slag (calcium source) and rice husk ash (silicon source); The interaction coefficient between carbide slag (calcium source) and fly ash (aluminum source); The interaction coefficient between rice husk ash (silicon source) and fly ash (aluminum source); The coefficients represent the interaction of calcium carbide slag (calcium source), rice husk ash (silicon source), and fly ash (aluminum source).

[0087] Contour maps of CBR, 28-day unconfined compressive strength, and water stability coefficient of modified red sandstone subgrade filler under different mix proportions are shown below. Figure 2 , 3 As shown in Figure 4.

[0088] Based on measured data, the CBR response model function expression for the improved red sandstone subgrade fill is constructed as follows:

[0089]

[0090] In addition, the measured CBR values, predicted values, and prediction relative errors of the improved red sandstone roadbed filler are shown in Table 2.

[0091] Table 2 Comparison of Measured and Predicted Values ​​of CBR

[0092]

[0093] Based on measured data, the functional expression of the 28-day unconfined compressive strength response model for the improved red sandstone subgrade fill is as follows:

[0094]

[0095] In addition, the measured values, predicted values, and prediction relative errors of the 28-day unconfined compressive strength of the improved red sandstone roadbed fill are shown in Table 3.

[0096] Table 3 Comparison of Measured and Predicted Values ​​of Unconfined Compressive Strength

[0097]

[0098] Based on measured data, the functional expression of the improved red sandstone subgrade fill water stability coefficient response model is constructed as follows:

[0099]

[0100] In addition, the measured values, predicted values, and prediction relative errors of the water stability coefficient of the improved red sandstone roadbed filler are shown in Table 4.

[0101] Table 4 Comparison of Measured and Predicted Values ​​of Water Stability Coefficient

[0102]

[0103] The CBR, 28-day unconfined compressive strength, and water stability coefficient of the improved red sandstone subgrade fill material were selected as the main road performance indicators. The performance constraints were assumed to be: CBR ≥ 72.68%, 28-day unconfined compressive strength ≥ 173.4 kPa, and water stability coefficient ≥ 0.5011. The contour maps of each road performance indicator were overlaid on the same map, as shown below. Figure 5 As shown. Figure 5 The overlapping area (blue area) represents the optimal range of solid waste raw materials that meets the set constraints. Considering all performance requirements, a dosage of 50%–58.8% carbide slag, 12.9%–18.04% rice husk ash, and 25.5%–37.3% fly ash can satisfy all requirements. Finally, based on the reserves and market prices of carbide slag, rice husk ash, and fly ash in different engineering areas, and combined with the above optimal ranges, the optimal mix proportion can be determined through comprehensive comparison.

[0104] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for optimizing the mix proportion of improved red sandstone roadbed filler based on multi-source solid waste, characterized in that, The improved red sandstone roadbed filler is prepared from red sandstone, carbide slag, rice husk ash, and fly ash as raw materials, wherein carbide slag, rice husk ash, and fly ash are used as cementing components, and red sandstone is used as the matrix to be improved; the mix proportion optimization method of the improved red sandstone roadbed filler includes the following steps: (1) Determine the proportion of cementitious components: The proportion of cementitious components should be controlled between 9% and 18%; (2) Design of experimental variables and schemes: Using the content of carbide slag X1, rice husk ash X2, and fly ash X3 in the cementitious components as design variables, design at least 7 sets of experiments, and in each set of experiments, the design variables satisfy X1+X2+X3=1, where X1, X2, and X3 are all non-negative values; (3) Preparation of improved filler: Weigh red sandstone, carbide slag, rice husk ash and fly ash according to the design mix ratio, add water with the optimal moisture content and mix evenly to obtain improved red sandstone roadbed filler; (4) Testing road performance: The specimens were prepared by static pressure method, cured to the test age according to standard, and the load-bearing ratio CBR, 28-day unconfined compressive strength and water stability coefficient were determined. (5) Optimize mix proportion: Based on the performance test results, construct a road performance response model, draw and overlay performance contour maps, and determine the mix proportion optimization range that meets multiple road performance requirements; the functional expression Y(X1, X2, X3) of the improved red sandstone filler road performance response model in step (5) is expressed as: In the formula, The model response values ​​for the road performance of the improved red sandstone roadbed fill material - CBR, unconfined compressive strength, and water stability coefficient; These are the individual action coefficients for carbide slag, rice husk ash, and fly ash, respectively. The interaction coefficient between carbide slag and rice husk ash; The interaction coefficient between carbide slag and fly ash; The interaction coefficient between rice husk ash and fly ash; The coefficients of interaction among carbide slag, rice husk ash, and fly ash.

2. The method for optimizing the mix proportion of improved red sandstone roadbed filler based on multi-source solid waste according to claim 1, characterized in that, The red sandstone is obtained by crushing, screening and drying of Class I and II easily disintegrating red sandstone that is not suitable for direct use as roadbed fill material, and the particle size of the red sandstone after treatment is less than 5mm.

3. The method for optimizing the mix proportion of improved red sandstone roadbed filler based on multi-source solid waste according to claim 1, characterized in that, The calcium oxide content in the carbide slag is not less than 90%, which is used to provide a calcium source for the red sandstone improvement system and create an alkaline environment; the silicon dioxide content in the rice husk ash is not less than 70%, which is used to provide a silicon source for the red sandstone improvement system; and the aluminum oxide content in the fly ash is not less than 25%, which is used to provide an aluminum source for the red sandstone improvement system.

4. The method for optimizing the mix proportion of improved red sandstone roadbed filler based on multi-source solid waste according to claim 1, characterized in that, The particle size of the carbide slag, rice husk ash, and fly ash is all less than 0.075 mm to ensure that the cementing components fully contact and react with the red sandstone matrix.

5. The method for optimizing the mix proportion of improved red sandstone roadbed filler based on multi-source solid waste according to claim 1, characterized in that, The optimal moisture content and maximum dry density of the modified red sandstone subgrade filler under different mix proportions in step (3) need to be determined by compaction test in accordance with the "Specifications for Geotechnical Testing of Highways" (JTG3430-2020).

6. The method for optimizing the mix proportion of improved red sandstone roadbed filler based on multi-source solid waste according to claim 1, characterized in that, The determination of bearing ratio CBR and 28-day unconfined compressive strength in step (4) should be completed by bearing ratio test and unconfined compressive strength test respectively in accordance with the "Specifications for Testing Geotechnical Engineering for Highways" (JTG3430-2020).

7. The method for optimizing the mix proportion of improved red sandstone roadbed filler based on multi-source solid waste according to claim 1, characterized in that, The formula for calculating the water stability coefficient in step (4) is: In the formula, This is the water stability coefficient; The unconfined compressive strength of the specimen under standard curing conditions; The unconfined compressive strength is determined by removing the sample one day before the standard curing period and immersing it in deionized water for 24 hours.

8. The method for optimizing the mix proportion of improved red sandstone roadbed filler based on multi-source solid waste according to claim 1, characterized in that, In step (2), the design variables X1 are set to a range of 0.5-1.0, X2 to a range of 0-0.5, and X3 to a range of 0-0.5, in order to balance the reaction efficiency of the gelling components with cost control.

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