Composite correction detection method for content of primary salt in fly ash improved soil
Through pH adjustment and composite precipitation steps, the error problem in the detection of soluble salts in fly ash-improved soil was solved, the accurate determination of the real soluble salts was achieved, and the risk of engineering misjudgment and disposal costs were reduced.
Patent Information
- Application Number
- CN202510874885.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-27
- Publication Date
- 2025-09-19
AI Technical Summary
The existing methods for detecting soluble salts in fly ash-amended soil have errors, leading to engineering misjudgments and unnecessary increases in treatment costs. This is mainly because calcium hydroxide and calcium sulfate in fly ash are easily soluble during water extraction, resulting in test values significantly higher than the actual effective salt content.
The pH adjustment and composite precipitation steps were adopted. By adjusting the pH value of the mixed solution to 7.0±0.5, carbonate solution, BaCl2 solution and AgNO3 solution were used for precipitation treatment to remove pseudo salts and retain only real soluble salt ions, including Ca2+, SO42- and Cl-.
The false salt in the fly ash-improved soil was effectively removed, and the accuracy of detection was improved. The recovery rates of Ca2+ and SO42- reached 99.5% and 98.5% respectively, avoiding the cost of saline soil disposal caused by misjudgment.
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Figure CN120668902A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of soil sample detection, and in particular relates to a composite correction detection method for soluble salt content in fly ash-improved soil. Background Art
[0002] Fly ash, a finely powdered solid waste generated in coal-fired power plants, is primarily composed of the incombustible mineral components remaining after coal combustion. It plays an increasingly important role in modern industry and environmental protection, transforming waste into treasure. Due to its lightweight, gelling activity, and cost-effectiveness, it is widely used in highway subgrade improvement.
[0003] Soluble salt testing in highway engineering involves quantitatively analyzing the content and composition of soluble salts in soil. These salts are readily soluble in water and can repeatedly dissolve and crystallize under temperature and humidity fluctuations, causing structural damage to the roadbed. Fly ash-amended soil is a mixture of undisturbed soil and fly ash. However, the calcium hydroxide (Ca(OH)2) and calcium sulfate (CaSO4) present in fly ash are readily dissolved and released during water extraction. This results in the total salt content measured using the 5:1 water-soil ratio extraction method specified in the current "Highway Soil Test Code" (JTG 3430-2020) being significantly higher than the actual effective salt content. When fly ash content in fly ash-amended soil was 5%, 10%, 15%, 20%, 25%, and 30%, respectively, the soluble salt contents measured using the current soluble salt testing method were 5.9, 6.8, 7.4, 8.5, 9.2, 10.2, and 5.2 g / kg. This error may lead to engineering misjudgments, such as overestimating the risk of salt expansion and increasing unnecessary treatment costs. Summary of the Invention
[0004] In view of the shortcomings of the existing technology, the present invention proposes a composite correction detection method for the soluble salt content of fly ash-improved soil.
[0005] The technical solution of the present invention is: A composite correction detection method for the original salt content of fly ash-improved soil comprises the following steps: S1. pH adjustment: mixing undisturbed soil and fly ash to obtain fly ash-amended soil, pre-treating the fly ash-amended soil, and mixing it with the extract to obtain a mixed solution A, adjusting the pH of the mixed solution A to 7.0±0.5, and centrifuging to obtain a supernatant B; S2. Composite precipitation: carbonate solution, BaCl2 solution, and AgNO3 solution are sequentially added to the supernatant B, stirred, centrifuged, and filtered to obtain a final extract. The ion content of the final extract is measured and the soluble salt content of the fly ash is removed to obtain the corrected primary salt content of the fly ash-amended soil.
[0006] Furthermore, the mass ratio of undisturbed soil to fly ash in the fly ash-improved soil in step S1 is (95-70):(5-30).
[0007] Furthermore, the specific steps of pre-treating the fly ash-improved soil in step S1 are: air-drying, grinding, and sieving the fly ash-improved soil.
[0008] Furthermore, the technical parameters of the air-drying are: air-drying the fly ash-improved soil at room temperature for 24-48 hours.
[0009] Furthermore, the pretreated fly ash improved soil described in step S1: extract = 1g: 5ml.
[0010] Furthermore, the carbonate solution in step S2 is a sodium carbonate solution.
[0011] Furthermore, the concentration of the carbonate solution and the BaCl2 solution in step S2 is 10-12%. Furthermore, the concentration of the AgNO3 solution in step S2 is 4-7%.
[0012] Compared with the prior art, the present invention has at least the following advantages: The present invention relates to a composite correction detection method for the primary salt content of fly ash-improved soil. The composite correction detection method comprises the steps of pH adjustment and composite precipitation of the fly ash-improved soil extract. The pH adjustment can reduce the solubility of Ca(OH)2 and eliminate the interference of Ca(OH)2. The composite precipitation can sequentially remove Ca(OH)2. 2+ 、SO4 2- and Cl - , exclude false salt, retain only the real soluble salt ions in the improved soil, avoid the cost of saline soil disposal caused by misjudgment, after testing, the composite correction detection method of the original salt content of fly ash improved soil Ca 2+ The recovery rate is 99.5%, SO4 2- The recovery rate was 98.5%. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] In order to more clearly illustrate the specific embodiments of the present invention, the following briefly introduces the drawings required for the specific embodiments or the description of the prior art.
[0014] Figure 1 This is a SEM image of fly ash, the raw material used in the present invention; Figure 2 The XRD pattern of fly ash, the raw material used in the present invention; Figure 3This is the XRD analysis diagram of the crystals of the improved soil of the present invention after drying in the soluble salt detection test in the "Highway Geotechnical Test Code" (JTG 3430-2020). DETAILED DESCRIPTION
[0015] The present invention is described in further detail below. It is necessary to point out that the following specific implementation methods are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above application content.
[0016] This document provides general and / or specific descriptions of the materials and experimental methods used in the experiments. Unless otherwise specified, all experimental or testing methods are conventional methods. All reagents and instruments used, unless the manufacturer is specified, are commercially available, conventional products and were prepared or used using conventional methods.
[0017] The current "Highway Geotechnical Test Code" (JTG3430-2020) soil soluble salt detection method is as follows: first prepare a fly ash-amended soil sample, take the original soil, add fly ash to the original soil at a mass ratio of 5-30%, and stir evenly to obtain fly ash-amended soil; then, according to the JTG 3430-2020 code, extract the soluble salt content in the fly ash at a water-soil ratio of 5:1, and the soluble salt content in the extracted improved soil. The original soil salt content is calculated using the following formula: , The meaning of each parameter in the formula: S original : the original salt content per unit mass of undisturbed soil; C mix : Salt concentration measured after leaching of fly ash-amended soil (unit: mg / kg or mg / L); m soil : Mass of the original soil of the raw material (unit: kg or g); m flyash : Mass of raw material fly ash (unit: kg or g); C flyash : Soluble salt content of fly ash extracted from raw material (unit: C mix consistent); C mix ×(m soil + m flyash ): total salt mass in fly ash-amended soil; C flyash ×m flyash : Salt mass in fly ash.
[0018] The XRD analysis of the dried crystals was tested by the current soil soluble salt detection method. Figure 1 As shown in the figure, it can be seen that the calcium salt content in the dried crystals is relatively high. The calcium hydroxide (Ca(OH)2) and calcium sulfate (CaSO4) rich in fly ash are easily dissolved and released during the water extraction process, resulting in the total salt content determined by the above-mentioned soluble salt detection method being significantly higher than the actual effective salt.
[0019] Reagent Source: Na2CO3 solution: analytical grade, purchased from Sinopharm Group; BaCl2 solution: analytical grade, purchased from Sinopharm Group; AgNO3 solution: high purity, purchased from Alfa Aesar; Ion chromatography calibration solution: mixed anion / cation standard; Dionex six kinds of anion / cation mixed standard solution; Original soil: taken from the saline soil area of Zhundong coal power industry base in Qitai County, Changji, Xinjiang; Fly ash: F-class II fly ash from Wanneng Jiangbu Power Plant; SEM image of fly ash is as follows Figure 2 As shown in the figure, it can be seen that the fly ash particles are irregular in shape and poorly dispersed; the XRD pattern of fly ash is as follows Figure 3 The main chemical components of the fly ash are shown in Table 1. Figure 3 As can be seen from Table 1, the CaO content in fly ash is relatively high.
[0020] Table 1 Main chemical components of fly ash Ion chromatography-related reagents and equipment: Chromatographic column models: Dionex lonPac AS11-HC (anion analysis), CS12A (cation analysis); Mobile phase: Anion: 30 mmol / L KOH (gradient elution); Cation: 20 mmol / L methanesulfonic acid (MSA); Flow rate: 1.0 mL / min; Detector: Conductivity detector (suppressed type).
[0021] Example 1 Composite Correction Detection Method for Primary Salt Content of Fly Ash-Improved Soil of the Present Invention S1. Preparation of fly ash-amended soil samples: 9.5 g of undisturbed soil was mixed with 0.5 g of fly ash at a 5% mass ratio to obtain the amended soil. The soil was air-dried at 25°C for 48 h, protected from direct sunlight, ground in an agate mortar, and passed through a 2 mm standard sieve. The soil was then cured for 7 days to obtain the amended soil sample. The extractability of soluble salts in the fly ash was previously determined. S2. Prepare an extract and determine the soluble salt content of the improved soil: The extract is deionized water with a conductivity of ≤0.2 μS / cm. Add 50 ml of the extract to the improved soil sample prepared in S1 at a water-to-soil ratio of 5:1. Stir thoroughly to obtain a mixed solution A. Add 0.1 mol / L dilute hydrochloric acid dropwise to the mixed solution A to adjust the pH to 7.0. Oscillate the mixture at 200 vibrations / min at 25°C for 2 h, allow it to stand for 24 h, and centrifuge at 3000 rpm to separate the supernatant B. S3. Compound precipitation correction: S31. After adding 10% Na2CO3 solution to the supernatant separated by centrifugation in step S2 (according to the CO3 in Na2CO3), 2- Compared with the Ca measured in S1 2+ The mixture was stirred at 200 r / min for 30 min, centrifuged at 4000 r / min, and filtered through a 0.45 μm filter membrane to remove the CaCO3 precipitate to obtain intermediate solution C. S32 was added to the intermediate solution C obtained in step S31 10ml of a 10% BaCl2 solution, stirred at 200r / min for 30min, centrifuged at 4000r / min, and filtered through a 0.45μm membrane to remove the BaSO4 precipitate to obtain an intermediate solution D; S33. Add 5 ml of 5% AgNO3 solution to the intermediate solution D obtained in step S32, stir at 200 r / min for 30 min, centrifuge at 4000 r / min, filter the AgCl precipitate with a 0.45 μm filter membrane to obtain a final extract, and determine the Cl content in the final extract by ion chromatography (equipment ICS-5000+). - 、SO4 2- , Ca 2+ 、Na + ion content, and removing the fly ash soluble salt extraction value obtained in step S1, the final improved soil soluble salt content is 5.3g / kg.
[0022] The present invention takes the final extract obtained in Example 1 as an example to test the Ca content in the extract. 2+ 、SO4 2- The recovery rates were 99.5% and 98.5% respectively.
[0023] Example 2 The steps of this embodiment are basically the same as those of the first embodiment, except that in step S1, 9 g of original soil is taken, 1 g of fly ash is added to the original soil at a mass ratio of 10%, and the content of soluble salt in the final improved soil is 5.5 g / kg.
[0024] Example 3 The steps of this embodiment are basically the same as those of the first embodiment, except that in step S1, 8.5 g of original soil is taken, 1.5 g of fly ash is added to the original soil at a mass ratio of 15%, and the content of soluble salt in the final improved soil is 5.8 g / kg.
[0025] Example 4 The steps of this embodiment are basically the same as those of the first embodiment, except that in step S1, 8 g of original soil is taken, 2 g of fly ash is added to the original soil at a mass ratio of 20%, and the content of soluble salt in the final improved soil is 6.0 g / kg.
[0026] Example 5 The steps of this embodiment are basically the same as those of the first embodiment, except that in step S1, 7.5 g of original soil is taken, and 2.5 g of fly ash is added to the original soil at a mass ratio of 25%, and the content of soluble salt in the final improved soil is 6.3 g / kg.
[0027] Example 6 The steps of this embodiment are basically the same as those of the first embodiment, except that in step S1, 7 g of original soil is taken, 3 g of fly ash is added to the original soil at a mass ratio of 30%, and the content of soluble salt in the final improved soil is 6.5 g / kg.
[0028] Example 7 The steps of this embodiment are basically the same as those of the first embodiment, except that fly ash is not added in step S1, and the content of soluble salt in the final improved soil is 5.0 g / kg.
[0029] Test Case This test example uses the method described in the prior art as a control, and fly ash is added to the original soil at a mass ratio of 0%, 5%, 10%, 15%, 20%, 25%, and 30% to obtain fly ash-improved soil. The soluble salt content of the improved soil is tested, and the soluble salt content of the improved soil measured by the prior art method is compared with that of Examples 1 to 7. The results are shown in the following table: Table 2: Soluble salt content of improved soil measured by prior art methods in Examples 1-7 As can be seen from Table 2, when the fly ash content is between 0-30%, the higher the fly ash content, the greater the relative deviation between the soluble salt content obtained by the detection method of the present invention and the soluble salt content obtained by the method of the comparative example, and there is a significant difference between the two data.
[0030] The present invention relates to a composite correction detection method for the original salt content of fly ash improved soil. The traditional detection method of soluble salt in improved soil includes a leaching step, and fly ash is rich in CaO, SO4 2- 、Al 3+When fly ash is dissolved in water, CaO generates Ca(OH)2 when it meets water, which makes the extract alkaline (pH>10). The solubility of Ca(OH)2 increases with the increase of pH. The traditional method of detecting soluble salts in improved soil will misjudge it as soluble salts, causing deviation in the measured value. In addition, SO4 in fly ash 2- With Ca 2+ Under alkaline conditions, CaSO4 is slightly soluble, Al 3+ With Cl - Easy to form complex [AlCl4] - This also causes deviations in measured values, leading to engineering misjudgments and increased saline soil disposal costs. The present invention's composite correction detection method for the native salt content of fly ash-improved soil combines pH adjustment and composite precipitation correction to remove interfering factors and restore the true soluble salt value of the improved soil, showing promising application prospects.
[0031] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.
Claims
1. A composite correction detection method for the original salt content of fly ash-improved soil, characterized in that: The following steps are involved: S1. pH adjustment: mixing undisturbed soil and fly ash to obtain fly ash-amended soil, pre-treating the fly ash-amended soil, and mixing it with the extract to obtain a mixed solution A, adjusting the pH of the mixed solution A to 7.0±0.5, and centrifuging to obtain a supernatant B; S2. Composite precipitation: carbonate solution, BaCl2 solution, and AgNO3 solution are sequentially added to the supernatant B, stirred, centrifuged, and filtered to obtain a final extract. The ion content of the final extract is measured and the soluble salt content of the fly ash is removed to obtain the corrected primary salt content of the fly ash-amended soil.
2. The composite correction detection method according to claim 1, characterized in that: The mass ratio of undisturbed soil to fly ash in the fly ash-improved soil in step S1 is (95-70):(5-30).
3. The composite correction detection method according to claim 2, characterized in that: The specific steps of pre-treating the fly ash-improved soil in step S1 are: air-drying, grinding, and sieving the fly ash-improved soil.
4. The composite correction detection method according to claim 3, characterized in that: The technical parameters of the air drying are: air drying the fly ash improved soil at room temperature for 24-48 hours.
5. The composite correction detection method according to claim 1, characterized in that: The fly ash-improved soil after the pretreatment described in step S1: the extract = 1g: 5ml.
6. The composite correction detection method according to claim 1, characterized in that: The carbonate solution in step S2 is a sodium carbonate solution.
7. The composite correction detection method according to claim 6, characterized in that: The concentration of the carbonate solution and the BaCl2 solution in step S2 is 10-12%.
8. The composite correction detection method according to claim 7, characterized in that: The concentration of the AgNO3 solution in step S2 is 4-7%.