Calcined muck activity evaluation method and system based on combination of macroscopic mechanical property and microscopic ion dissolution property

Abstract

The invention discloses a calcined muck activity evaluation method based on combination of macroscopic mechanical properties and microscopic ion dissolution performance. The method comprises the following steps: pretreating building muck; calcining the muck at different temperatures; carrying out an ion dissolution test to determine the dissolution concentrations of Ca < 2 + >, Al < 3 + > and Si < 4 + >; mixing the calcined muck cement mortar test piece, and measuring the fracture resistance / compressive resistance of the calcined muck cement mortar test piece; and finally, comprehensively evaluating the activity of the calcined muck by combining the ion dissolution concentration of the calcined muck in the alkali liquor and the test result of the mechanical strength of the test block. Through macro-micro combination, false coagulation phenomenon misjudgment is avoided, multi-dimensional and dynamic evaluation of activity is realized, long-term performance can be accurately predicted, a calcination process can be optimized, and the method is suitable for resource utilization of muck of different sources and has comprehensiveness, accuracy, high efficiency and environmental benefits.

Description

Technical Field

[0001] This invention relates to the field of building materials and solid waste resource utilization technology, specifically to an activity evaluation technology in the process of building waste resource utilization, and more particularly to a comprehensive evaluation method for the activity of calcined waste that combines macroscopic mechanical property testing and microscopic ion dissolution behavior analysis, as well as an intelligent system for implementing the method. Background Technology

[0002] With the rapid advancement of urbanization in my country, infrastructure construction and renovation have generated a massive amount of construction waste, with construction waste making up the majority. The traditional method of disposing of this large amount of waste is primarily landfilling, which not only occupies valuable land resources but also poses environmental pollution and safety hazards such as landslides. Therefore, promoting the resource utilization of construction waste and transforming it into valuable building materials has become an inevitable trend in the industry.

[0003] Currently, the main technical approach to improving the cementitious activity of construction waste is the calcination activation method. This involves high-temperature heat treatment (usually 600-900℃) to dehydrate and dissociate the layered silicate minerals (such as kaolinite and illite) in the waste, transforming them into amorphous metakaolinite and other substances with high pozzolanic activity. However, scientifically and accurately assessing the activity of the calcined waste is a crucial prerequisite for guiding its efficient resource utilization.

[0004] Existing technologies for assessing the activity of calcined slag generally suffer from the following shortcomings:

[0005] 1. Limited Evaluation Dimensions: This method primarily relies on using slag as an admixture to prepare mortar or concrete test blocks, testing their macroscopic mechanical properties (such as compressive strength and flexural strength), and calculating the strength activity index. This approach only reflects the final mechanical contribution of slag in a specific cementitious system, completely ignoring the microscopic essential properties of its own active components, such as dissolution characteristics, rates, and long-term stability.

[0006] 2. Separation of macroscopic and microscopic properties: Macroscopic mechanical strength is the macroscopic manifestation of the accumulation of microscopic chemical reactions, but existing methods cannot establish a correlation between the two. For example, the same 28-day compressive strength may correspond to drastically different ion dissolution behaviors, the latter of which directly affects the long-term durability of materials, but traditional methods cannot identify this difference, let alone predict the problem of inflated early strength caused by phenomena such as "false solidification".

[0007] 3. Weak process guidance: The effects of calcination process parameters (temperature, time, cooling rate) on the activity of slag and soil are complex and nonlinear. Existing single mechanical evaluation methods are insufficient to quantify this complex relationship and cannot accurately identify the optimal activation process window for slag and soil from different sources and with different mineral compositions. This results in high energy consumption and low efficiency in actual production, and a lack of data support for process optimization.

[0008] Therefore, developing a method for evaluating the activity of calcined slag that can integrate macroscopic and microscopic properties, achieve dynamic quantitative assessment, and effectively guide process optimization is of great practical significance for improving the level of slag resource utilization technology and promoting the development of the green building materials industry. Summary of the Invention

[0009] This invention aims to overcome the aforementioned shortcomings of existing technologies and provide a comprehensive, accurate, and dynamic method and system for evaluating the activity of calcined slag. The core of this invention lies in the creative combination of macroscopic mechanical property testing and microscopic ion dissolution behavior analysis to construct a multi-dimensional, quantitative activity evaluation system.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] In a first aspect, the present invention provides a method for evaluating the activity of calcined slag soil based on a combination of macroscopic mechanical properties and microscopic ion dissolution properties, comprising the following steps:

[0012] S1. Pre-treat the construction waste to obtain the waste sample to be tested;

[0013] S2. The slag sample to be tested is calcined at at least two different temperatures to obtain calcined slag samples at different calcination temperatures;

[0014] S3. Conduct an ion leaching test on the calcined slag sample to determine its ion leaching concentration in an alkaline solution;

[0015] S4. Mix the calcined slag sample with cement and mortar to prepare a specimen, and conduct mechanical property tests to determine its mechanical strength;

[0016] S5. Based on the results of the ion leaching concentration and the mechanical strength of the mortar test block, determine the activity evaluation results of the calcined slag soil sample.

[0017] Further, in step S1, the pretreatment includes: air-drying the construction waste, mechanically crushing it, screening it to a particle size of no more than 1.25 mm, and using X-ray diffraction to analyze its mineral composition, focusing on identifying the content of key minerals such as kaolinite and illite.

[0018] Furthermore, in step S2, based on the mineral composition analysis results, a calcination temperature gradient covering the range of 600℃ to 900℃ is set, the calcination heating rate is 10℃ / min, and after reaching the predetermined temperature, the temperature is kept constant for 2 hours.

[0019] Further, in step S3, the ion leaching test specifically involves: mixing a certain mass of calcined slag sample with a sodium hydroxide solution of a specific concentration at a fixed solid-liquid ratio (e.g., 1g:20ml), placing it in a constant temperature water bath (e.g., 25℃) and continuously stirring; taking samples at different time points (e.g., 2 hours and 24 hours); and determining the Ca in the filtrate using inductively coupled plasma mass spectrometry. 2+ Al 3+ Si 4+ The concentrations of characteristic ions are determined. The concentration of the sodium hydroxide solution is preferably at least one of 2 mol / L, 6 mol / L, and 10 mol / L, to investigate the dissolution behavior under different alkalinity conditions.

[0020] Further, in step S4, the mechanical property test includes: preparing calcined slag-cement specimens according to the standard mass ratio (e.g., calcined slag: cement = 3:7), curing them to the specified age (e.g., 7 days and 28 days) according to the standard, determining their compressive strength and flexural strength according to the national standard, and calculating the strength activity index relative to the reference specimen.

[0021] Furthermore, in step S5, by integrating ion dissolution kinetic data at different calcination temperatures with mechanical strength development data of mortar specimens, a multidimensional correlation model between "calcination temperature - ion dissolution characteristics - macroscopic mechanical properties" is established. This model can be used to: a) comprehensively evaluate the absolute activity and activity development law of slag soil; b) identify the optimal calcination process parameters; and c) predict the long-term performance of different slag soils under specific application scenarios.

[0022] Secondly, the present invention provides an intelligent evaluation system for the activity of calcined slag soil used in implementing the above-mentioned method, characterized in that it comprises:

[0023] The data acquisition module is used to standardize the input or automatically acquire ion dissolution concentration data, mortar test block mechanical strength data, and calcination process parameters generated in the evaluation method.

[0024] The data analysis module has an embedded activity evaluation algorithm based on the multidimensional correlation model, which is used to process input data, calculate the activity index, and perform process optimization analysis.

[0025] The output module is used to generate and output a structured activity evaluation report, which includes at least an activity level evaluation, recommended optimal calcination process parameters, and performance prediction.

[0026] The beneficial effects of this invention are as follows:

[0027] 1. Comprehensive assessment and reliable results: By combining macroscopic mechanical properties with microscopic ion dissolution, a full-dimensional assessment of the activity of calcined slag soil is achieved, overcoming the one-sidedness of single-index assessment. The results are more scientific and reliable, and can effectively identify "false activity".

[0028] 2. Dynamic quantification and accurate prediction: By setting different dissolution time points and alkali concentrations, dynamic dissolution curves of active components were obtained, realizing a quantitative description of the activity development process, which is beneficial for predicting the long-term performance of materials.

[0029] 3. Guiding processes and improving efficiency: The established correlation model clarifies the influence of calcination process parameters on macroscopic and microscopic properties, and can accurately recommend the optimal calcination regime for slag from different sources, thereby reducing energy consumption and improving resource utilization efficiency and product performance.

[0030] 4. Intelligent system, convenient application: The evaluation method is software-based and systematized to form an intelligent evaluation tool, which greatly reduces the technical threshold and operating cost of evaluation, and is conducive to the standardization, promotion and application of the technology.

[0031] 5. Significant environmental and social benefits: This invention helps promote the high-value-added resource utilization of construction waste, reduces the stockpiling of solid waste and the consumption of natural raw materials, and is in line with the green, low-carbon and circular sustainable development strategy. Attached Figure Description

[0032] Figure 1 These are X-ray diffraction patterns of slag and soil after calcination at different temperatures in this invention.

[0033] Figure 2 This is a comparison diagram of the flexural strength of calcined slag-cement mortar in this invention.

[0034] Figure 3 This is a comparison diagram of the compressive strength of calcined slag soil-cement mortar in this invention.

[0035] Figure 4 This is a comparison chart of the strength and activity indices of calcined slag soil in this invention.

[0036] Figure 5 This is a schematic diagram showing the ion dissolution results of calcined slag in NaOH solution in this invention. Detailed Implementation

[0037] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0038] It should be noted that when a component is said to be "fixed to" another component, it can be directly attached to the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component.

[0039] Unless otherwise defined, 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. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0040] This invention addresses the shortcomings of existing calcined slag activity assessment technologies by proposing a quantitative assessment method based on a combination of macroscopic mechanical properties and microscopic ion leaching properties. By integrating macroscopic mechanical property tests of slag-cement mortar with ICP ion leaching tests, a quantitative assessment model for calcined slag activity is derived. This aims to achieve multi-dimensional and dynamic assessment of calcined slag activity and process optimization, providing a theoretical basis and technical support for efficient resource utilization. Its core technical route is as follows:

[0041] Example 1: Activity assessment of clayey slag from a subway project in South China

[0042] S1. Pretreatment: A representative sample of slag soil was taken, air-dried, crushed, and passed through a 1.25 mm square-hole sieve. X-ray diffraction (XRD) analysis was used to determine that its main mineral composition was kaolinite (approximately 35%), illite (approximately 20%), quartz (approximately 30%), and a small amount of feldspar.

[0043] S2. Calcination Treatment: The pretreated slag was calcined in muffle furnaces at 600℃, 700℃, 750℃, 800℃, and 900℃ for 2 hours respectively, and then cooled with the furnace to obtain a series of calcined slag samples, numbered C600, C700, C750, C800, and C900. Figure 1 As shown, XRD pattern analysis of untreated slag and slag calcined at different temperatures (600℃, 700℃, 800℃, and 900℃) revealed that heat treatment significantly altered the mineral phase composition of the slag. When the calcination temperature was below 750℃, the kaolinite phase in the slag failed to fully transform into metakaolinite, resulting in insufficient release of active components. However, when the temperature exceeded 750℃, some components began to crystallize, inhibiting the release of active silica-alumina components. The sample calcined at 750℃ for 2 hours exhibited the best active transformation characteristics.

[0044] S3. Ion dissolution test: Weigh 1.00 g of each calcined sample and place it in a 150 mL Erlenmeyer flask. Add 20 mL of 6 mol / L NaOH solution and stir the mixture at a constant temperature of 25 °C. Take samples at 2 h and 24 h, centrifuge and filter, and determine the Ca content in the filtrate using ICP-MS. 2+ Al 3+ and Si 4+ The concentrations were determined, and the experimental results are shown in Table 1. Figure 5 As shown, the Al of C750 sample at 24h 3+ The highest leaching rate was observed. In 6M NaOH solution, the calcined slag exhibited the best ion leaching behavior. Lower alkali concentrations were insufficient to effectively break Al-O and Si-O bonds, while excessively high alkali concentrations would rapidly form products on the raw material surface, inhibiting the subsequent leaching of active components. Experimental data showed that the total leaching rate of 27Al was approximately 7-8 times that of 29Si, while the leaching rate of 44Ca was almost negligible. This is due to the higher charge radius of Si4+ compared to... Less than Furthermore, the calcium content in the slag is relatively low. In addition, the dissolution behavior of 27Al and 29Si exhibits non-steady-state characteristics, with rapid dissolution in the early stage, followed by a gradual stabilization.

[0045] The uneven dissolution of active alumina, silica, and calcium components in calcined slag explains the poor performance of its hardened system in terms of strength and durability development. This is due to the failure to form sufficient CHS or NASH gel. This finding highlights the limitations of using slag alone as a precursor for preparing alkali-activated materials (AAMs) or geopolymers (GPs). Additional silica and calcium sources must be added to improve performance.

[0046] Table 1. Experimental Design Table of Factors Affecting the Dissolution of Ions in Calcined Slag in NaOH Solution

[0047]

[0048] As shown in Table 1, the ion leaching concentration of calcined slag at 750℃ was significantly higher than that at other temperatures over 24 hours, with Al... 3+ The dissolution rate increased by about 40%, indicating that the active components were most fully converted at this temperature.

[0049] S4. Mechanical Property Tests: Mortar flowability was tested according to GB / T 2419-2005 "Method for Determination of Flowability of Cement Mortar"; flexural strength and compressive strength of mortar specimens were tested sequentially according to GB / T 17671-2021 "Method for Testing the Strength of Cement Mortar (ISO Method)". The leaching concentrations of Ca2+, Al3+, and Si4+ ions in calcined slag at different concentrations and leaching times in NaOH solution were tested according to GB / T37667-2019 "Determination of Iron, Calcium, Magnesium, Potassium, Sodium, Manganese, Phosphorus, Aluminum, Titanium, Barium and Strontium in Fly Ash by Inductively Coupled Plasma Atomic Emission Spectrometry". Cement mortar specimens were prepared. The reference group (PM) consisted of pure cement mortar. The experimental group used 30% calcined slag (C700, C750, C800) by mass to replace cement. Compressive strength was tested at 7 days and 28 days. Figure 2 and Figure 3 As shown in Table 2, the C750 group had the highest compressive strength at 28 days, with a Strength Activity Index (SAI) of 0.93. Figure 4 As shown, the Strength Activity Index (SAI) of calcined slag soils at 700℃ and 750℃ were both greater than 1 after 7 days of curing, exhibiting a significant early strength advantage. However, the SAI values ​​at 28 days were generally lower than those at 7 days, indicating that the long-term strength development rate slowed down compared to the earlier stages. The SAI values ​​of calcined slag soils (C700, C750, and C800) at 28 days were 0.88, 0.93, and 0.84, respectively, indicating that 750℃ was the optimal temperature for enhancing the activity of the slag soils.

[0050] Table 2. Summary of 7-day and 28-day compressive and flexural strengths

[0051]

[0052] S5. Comprehensive Assessment and Model Building: Comprehensive Figure 3 and Figure 4 Data revealed that the C750 sample simultaneously possessed optimal Al... 3+ Dissolution rate and highest 28-day compressive strength. The calcination temperature (T) and 24-hour Al content at different temperature points were compared. 3+ Dissolution amount (C) _A1 ) and 28-day compressive strength (f _c By performing multiple regression analysis, a functional relationship f can be established. _c =F(T, C) _Al According to this model, the optimal calcination temperature for this slag is 750℃, and its activity assessment result is "excellent". Based solely on mechanical strength, there is little difference between C700 and C750; however, considering leaching data, C750 has superior long-term activity potential.

[0053] Example 2: Activity evaluation at different alkali concentrations

[0054] To verify the universality of the present invention, the calcined slag from Example 1 at 750℃ was used to conduct ion leaching tests with 2M, 6M, and 10M NaOH solutions, respectively, with other conditions the same as in Example 1.

[0055] The experimental results are shown in Table 3:

[0056]

[0057] As shown in Table 3, both the ion dissolution concentration and mechanical strength increase with increasing alkali concentration. However, 6M NaOH can meet most application requirements, while 10M NaOH, although more effective, is more expensive. This invention allows for flexible selection of alkali concentration based on actual application needs.

[0058] Example 3: Application of Intelligent Evaluation System

[0059] Based on Example 1 and a large amount of similar data, an intelligent evaluation system for the activity of calcined slag was developed. Users input or select the preliminary XRD analysis results (main mineral types) of the slag through the data acquisition module. The system recommends a default calcination temperature gradient (e.g., 600-900℃, 50℃ increments) and test scheme. After completing steps S3 and S4, users input ion dissolution data and mechanical strength data into the system. The data analysis module calls a pre-trained correlation model to automatically calculate the comprehensive activity score for each temperature point and generate an evaluation report. The output module's report shows: "Based on the input data, the recommended optimal calcination process is 755℃ for 2 hours. It is predicted that under these conditions, when the slag is used as a 30% cement substitute, the 28-day strength activity index can reach 0.92±0.03, indicating excellent long-term durability."

[0060] Application prospects:

[0061] 1) In the field of green building materials: it provides a scientific evaluation method for the application of calcined slag in green building materials such as cement substitutes and geopolymers, and promotes the low-carbon development of the construction industry.

[0062] 2) Solid waste resource utilization: By optimizing the calcination process, the efficiency of waste soil resource utilization is improved, the pressure of solid waste storage on the environment is reduced, and the construction of "zero waste city" is contributed.

[0063] 3) Engineering application and promotion: Provide high-performance, low-cost calcined slag soil-based materials for engineering applications such as road base and wall materials, significantly reducing engineering costs.

[0064] 4) Technical standardization: Provide standardized methods for evaluating the activity of calcined slag and promote the formulation of industry technical specifications and standards.

[0065] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0066] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for evaluating the activity of calcined slag soil based on a combination of macroscopic mechanical properties and microscopic ion dissolution properties, characterized in that, Includes the following steps: S1. Pre-treat the construction waste to obtain the waste sample to be tested; S2. The slag sample to be tested is calcined at at least two different temperatures to obtain calcined slag samples at different calcination temperatures; S3. Conduct an ion leaching test on the calcined slag sample to determine its ion leaching concentration in an alkaline solution; S4. Mix the calcined slag sample with cement and mortar to prepare a specimen, and conduct mechanical property tests to determine its mechanical strength; S5. Based on the results of the ion leaching concentration and the mechanical strength of the mortar test block, determine the activity evaluation results of the calcined slag soil sample.

2. The evaluation method according to claim 1, characterized in that, In step S1, the pretreatment includes: air-drying, crushing, and screening the construction waste to a particle size of no more than 1.25 mm, and performing mineral composition analysis.

3. The evaluation method according to claim 1, characterized in that, In step S2, the calcination temperature range is 600℃ to 900℃, the calcination heating rate is 10℃ / min, and after reaching the predetermined temperature, the temperature is kept constant for 2 hours.

4. The evaluation method according to claim 1, characterized in that, In step S3, the ion leaching test specifically involves mixing the calcined slag sample with a sodium hydroxide solution, stirring the mixture under constant temperature conditions, taking samples at different time points, and determining the presence of at least Ca in the solution. 2+ Al 3+ Si 4+ The concentration of ions included.

5. The evaluation method according to claim 4, characterized in that, The concentration of the sodium hydroxide solution is at least one of 2 mol / L, 6 mol / L, and 10 mol / L.

6. The evaluation method according to claim 4, characterized in that, The different time points include 2 hours and 24 hours.

7. The evaluation method according to claim 1, characterized in that, In step S4, the mechanical property test includes: measuring the compressive strength and flexural strength of the specimen at 7 days and 28 days, and calculating the strength activity index.

8. The evaluation method according to claim 1, characterized in that, In step S5, an activity evaluation model is established by correlating the calcination temperature, the ion dissolution concentration, and the mechanical strength of the mortar sample to achieve quantitative evaluation of the activity.

9. The evaluation method according to any one of claims 1-8, characterized in that, In step S3, inductively coupled plasma mass spectrometry was used to determine the ion dissolution concentration; in step S1, X-ray diffraction was used to analyze the mineral composition.

10. An intelligent evaluation system for the activity of calcined slag, characterized in that, include: The data acquisition module is used to acquire ion dissolution concentration data and mortar test block mechanical strength data generated in the method described in any one of claims 1-9; The data analysis module has a built-in activity assessment model, which is used to process the data and generate activity assessment results; An output module is used to output the activity evaluation results, which include at least the recommended optimal calcination process parameters.

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