A rapid evaluation method for tunnel slag quality based on comprehensive properties of slag powder

Abstract

The present invention discloses a method for rapidly evaluating the quality of tunnel slag based on the comprehensive properties of slag powder, belonging to the field of building materials technology, and comprising the following steps: (1) sampling: randomly selecting tunnel slag with a clean surface and naturally air-dried; (2) pulverizing: grinding the obtained tunnel slag and passing it through a 0.075 mm sieve to collect slag powder with a particle size of less than 0.075 mm; (3) testing: rapidly testing the fluidity of the collected slag powder slurry and rapidly testing the sulfide and sulfate content of the collected slag powder in terms of SO3 mass; (4) evaluation: evaluating the quality of the tunnel slag based on the comprehensive properties of the slag powder slurry fluidity, sulfide and sulfate content. Compared with the existing technology, the present invention has the advantages of advanced concept, simple operation, rapid testing, accurate evaluation, and on-site applicability.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials and relates to a method for quickly evaluating the quality of tunnel slag based on the comprehensive properties of slag powder. Background Art

[0002] Utilizing tunnel slag not only reduces the number of waste dumps and minimizes environmental damage, but also transforms waste into valuable resources, generating significant social and economic benefits. However, unlike parent rock, tunnel slag exhibits significant performance fluctuations and contains high levels of harmful substances. To ensure the reliability of tunnel slag applications, rapid evaluation of the parent rock properties of tunnel slag is necessary.

[0003] Currently, rapid evaluation of tunnel slag performance primarily focuses on mechanical properties, while rapid testing of slag powder fluidity and sulfide and sulfate content is lacking. Patent CN111596030A, "A Rapid Evaluation Method for Tunnel Slag Suitable for Preparing Machine-Made Aggregates," uses a crushing index to rapidly evaluate tunnel slag performance within the same potential energy range, but this method is only applicable to characterizing mechanical properties. Patent CN114791402A, "A Rapid Comprehensive Evaluation Method and Apparatus for Tunnel Slag for Machine-Made Sand and Gravel," proposes an evaluation method and apparatus that simultaneously and rapidly tests the physical, mechanical, and durability properties of slag. However, this method lacks analysis of the content of harmful substances in slag and fails to consider the impact of slag powder on the performance of cement-based materials. "Limestone Powder Concrete" (GB / T 14685-2011) proposes a test method and indicators for the fluidity ratio of limestone powder, but this method requires additional materials such as cement and standard sand, and the test indicators are only applicable to limestone powder; "Construction Sand" (GB / T 14684-2022) proposes a test method for the sulfide and sulfate content of sand, but the testing process of this method is relatively cumbersome.

[0004] Therefore, how to provide a method for rapid evaluation of tunnel slag quality based on the comprehensive properties of slag powder with the advantages of advanced concept, simple operation, fast testing, accurate evaluation and applicability to the field is a technical problem that technical personnel in this field urgently need to solve. Summary of the Invention

[0005] In view of this, the present invention provides a method for quickly evaluating the quality of tunnel slag based on the comprehensive properties of slag powder.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for quickly evaluating tunnel slag quality based on the comprehensive properties of slag powder comprises the following steps:

[0008] (1) Sampling: Randomly select tunnel slag with clean surface and natural air drying;

[0009] (2) Powdering: Grind the obtained tunnel slag and pass it through a 0.075 mm sieve to collect the slag powder with a particle size less than 0.075 mm;

[0010] (3) Testing: Rapidly test the fluidity of the collected slag powder slurry, and quickly test the sulfide and sulfate content of the collected slag powder in terms of SO3 mass;

[0011] (4) Evaluation: The quality of tunnel slag is evaluated by the comprehensive performance of the slag slurry fluidity, sulfide and sulfate content.

[0012] Furthermore, the above step (1) specifically includes the following steps: before sampling, observe the state and size of the tunnel slag, randomly select multiple samples to form a collection of tunnel slag samples, and the tunnel slag samples should be selected from tunnel slag with a clean surface, naturally air-dried, and a length, width, and height greater than 5 cm.

[0013] The beneficial effects of adopting the above-mentioned further technical solution are: it is clarified that tunnel slag should be selected with a clean surface, naturally air-dried, and with a length, width and height greater than 5 cm. This can reduce the mixing of impurities such as soil, which affects the performance of the slag powder. At the same time, natural air-drying is conducive to powder making, and no additional heating and drying is required, saving time; slag greater than 5 cm is generally cleaner, and the random selection of multiple samples is mainly based on probability statistics, making the sampling more representative.

[0014] The above-mentioned random selection refers to sampling every 5-10 meters in the tunnel excavation direction, with 2 to 5 samples each time and a mass of 10kg to 30kg.

[0015] Furthermore, in the above step (2), the specific surface area of ​​the collected slag powder is 300~1000m 2 / kg.

[0016] Furthermore, in the above step (3), the method for quickly testing the fluidity of the collected slag powder slurry specifically includes the following steps:

[0017] Weigh 300 g of slag powder, add 150 g of water, and stir for 5 minutes to prepare a slag powder slurry, which is then loaded into a truncated cone test mold with an upper diameter of 36 mm, a lower diameter of 60 mm, and a height of 60 mm. After lifting the test mold, the average value of the maximum diameter in the vertical direction of the slag powder slurry when it flows on the glass plate for 30 seconds is taken as the fluidity of the slag powder slurry.

[0018] The beneficial effects of adopting the above-mentioned further technical solution are as follows: compared with the standard of ordinary cement paste, the amount of water added is increased and the stirring time is prolonged, which is more conducive to uniform stirring of the slag powder slurry. At the same time, the innovation is to only use slag powder as the slurry without adding cement, which makes the operation simpler; in addition, the indicator is easy to test.

[0019] Furthermore, in the above step (3), the method for quickly testing the sulfide and sulfate content of the collected slag powder specifically includes the following steps:

[0020] Mix 50-300g of slag powder thoroughly, put the mixed slag powder into the sample tray, use a portable XRF detector to measure, aim the instrument at the sample, measure different parts of the sample, and take the average value of the SO3 mass fraction in different parts.

[0021] The beneficial effect of adopting the above-mentioned further technical solution is that compared with the chemical titration method specified in the conventional national standard, the SO3 mass fraction can be quickly obtained by using XRF.

[0022] Furthermore, the above-mentioned different parts refer to the upper, middle and lower parts.

[0023] Furthermore, the mixing speed is 475 r / min and the mixing time is 5 min.

[0024] Furthermore, in the above step (4), when the fluidity of the tunnel slag powder slurry is ≥160mm and the SO3 mass fraction is ≤0.8%, the tunnel slag is a Class I qualified tunnel slag; when the fluidity of the tunnel slag powder slurry is ≥160mm and the SO3 mass fraction is 0.8%<1.2% or the fluidity of the tunnel slag powder slurry is 120mm≤<160mm and the SO3 mass fraction is ≤0.8%, the tunnel slag is a Class II qualified tunnel slag; when the fluidity of the tunnel slag powder slurry is 120mm≤<160mm and the SO3 mass fraction is 0.8%<1.2%, the tunnel slag is a Class III qualified tunnel slag; when the fluidity of the tunnel slag powder slurry is <120mm or the SO3 mass fraction is >1.2%, the tunnel slag is an unqualified tunnel slag.

[0025] The beneficial effects of adopting the above-mentioned further technical solution are as follows: an innovative approach is proposed to comprehensively consider the fluidity of the slag powder slurry and the SO3 mass fraction to characterize the slag performance, and an evaluation grade of the slag powder slurry and the SO3 mass fraction is given.

[0026] Beneficial effects of this statement: Compared with the prior art, the present invention has the following advantages:

[0027] 1. Comprehensively reflect the harmful substance content in tunnel slag and its impact on the performance of concrete: The proposed method can simultaneously and rapidly test two indicators, namely the fluidity of tunnel slag powder paste and the sulfide and sulfate content. It can comprehensively reflect the harmful substance content in tunnel slag and its impact on the performance of concrete, overcoming the difficulty of testing a single performance indicator and establishing a connection between tunnel slag and the performance of concrete.

[0028] 2. Improving the reliability of slag performance based on probability and statistical evaluation methods: A collection of slag specimens is composed of multiple samples. Based on the probability and statistical evaluation method, the fluctuating performance of slag can be homogenized, thereby ensuring the authenticity and reliability of the slag powder test and evaluation results.

[0029] 3. The test process is fast, convenient and highly accurate: The fluidity test of slag powder slurry only requires slag powder, water and a simple testing device. The sulfide and sulfate content can be quickly tested using handheld XRF. There are fewer influencing factors during the test process, and the accuracy rate is high.

[0030] 4. Applicable to on-site instant evaluation after tunnel slag is discharged: This method can be used to conduct instant evaluation on-site after tunnel slag is discharged, which can realize rapid sorting of tunnel slag and ensure the quality of tunnel slag from the source. DETAILED DESCRIPTION

[0031] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0032] The portable XRF detector used in Example 1 is the PORT-X600 handheld XRF produced by Gangyan Nanotechnology Co., Ltd.

[0033] The portable XRF detector used in Example 2 is the Thermo Fisher Niton XL2 500. Example 1

[0034] A 100m tunnel section was used as the research object, and the tunnel slag performance evaluation was carried out every 20m. A total of 5 sample batches needed to be evaluated. The lithology of the tunnel slag was limestone, and the surrounding rock grade was Grade III.

[0035] The rapid evaluation method of tunnel slag quality based on the comprehensive properties of slag powder includes the following steps:

[0036] (1) Sampling: Every 20 m of the tunnel section, randomly select 20 samples from different sections to form a collection of tunnel slag samples. The tunnel slag samples should be clean, naturally air-dried, and have a length, width, and height of 5 to 20 cm.

[0037] (2) Powdering: Grind the obtained tunnel slag using a small grinding mill for 1 hour and pass it through a 0.075 mm sieve to collect 1000 g of slag powder with a particle size less than 0.075 mm. The specific surface area of ​​the collected slag powder is 300~1000 m 2 / kg;

[0038] (3) Test: Weigh 300 g of slag powder and pour it into a stirring pot, add 150 g of water, and stir for 5 minutes to prepare a slag powder slurry. Then put it into a truncated cone test mold with an upper diameter of 36 mm, a lower diameter of 60 mm, and a height of 60 mm. After lifting the test mold, the average value of the maximum diameter in the vertical direction of the slag powder slurry when it flows on the glass plate for 30 seconds is taken as the fluidity of the slag powder slurry.

[0039] 100g of slag powder was fully mixed at a mixing speed of 475r / min for 5min. A small amount of the mixed slag powder was placed in a sample tray and measured using a portable XRF detector. The instrument was aimed at the sample and the upper, middle and lower parts of the sample were measured to obtain the SO3 mass fraction and take the average value.

[0040] (4) Evaluation: The quality of tunnel slag is evaluated by the comprehensive performance of the slag slurry fluidity, sulfide and sulfate content. When the slag slurry fluidity is ≥160mm and the SO3 mass fraction is ≤0.8%, the tunnel slag is a Class I qualified slag; when the slag slurry fluidity is ≥160mm and the SO3 mass fraction is 0.8% < 1.2% or when the slag slurry fluidity is 120mm≤ and the SO3 mass fraction is ≤160mm, the tunnel slag is a Class II qualified slag; when the slag slurry fluidity is 120mm≤ and the SO3 mass fraction is 0.8% < 160mm, the tunnel slag is a Class III qualified slag; when the slag slurry fluidity is <120mm or the SO3 mass fraction is >1.2%, the tunnel slag is an unqualified slag.

[0041] The specific test results are shown in Table 1.

[0042] Table 1 Test results of performance indexes of slag powder

[0043] It can be seen from Table 1 that the tunnel slag powder in the 100m section has excellent performance and is basically Class I qualified slag, indicating that the slag quality in this section is good. Example 2

[0044] A 120m tunnel section was selected as the research object, and the tunnel slag performance evaluation was carried out every 24m. A total of 5 sample batches were required to be evaluated. The lithology of the tunnel slag was granite, and the surrounding rock grade was Grade III.

[0045] The rapid evaluation method of tunnel slag quality based on the comprehensive properties of slag powder includes the following steps:

[0046] (1) Sampling: Every 24 m tunnel section, randomly select 30 samples from different sections to form a collection of tunnel slag samples. The tunnel slag samples should be clean, naturally air-dried, and have a length, width, and height of 10 to 30 cm.

[0047] (2) Powdering: Grind the obtained tunnel slag using a small grinder for 2 h, and pass it through a 0.075 mm sieve to collect 1500 g of slag powder with a particle size less than 0.075 mm. The specific surface area of ​​the collected slag powder is 300~1000 m 2 / kg;

[0048] (3) Test: Weigh 300 g of slag powder and pour it into a stirring pot. Add 150 g of water and stir for 5 min to prepare a slag powder slurry. Then put it into a truncated cone test mold with an upper diameter of 36 mm, a lower diameter of 60 mm, and a height of 60 mm. After lifting the test mold, the average value of the maximum diameter in the vertical direction of the slag powder slurry when it flows on the glass plate for 30 seconds is taken as the fluidity of the slag powder slurry.

[0049] 150g of slag powder was thoroughly mixed at a mixing speed of 475r / min for 5min. A small amount of the mixed slag powder was placed in a sample tray. A portable XRF detector was used for measurement. The instrument was aimed at the sample and the upper, middle and lower parts of the sample were measured to obtain the SO3 mass fraction and take the average value.

[0050] (4) Evaluation: The quality of tunnel slag is evaluated by the comprehensive performance of the slag slurry fluidity, sulfide and sulfate content. When the slag slurry fluidity is ≥160mm and the SO3 mass fraction is ≤0.8%, the tunnel slag is a Class I qualified slag; when the slag slurry fluidity is ≥160mm and the SO3 mass fraction is 0.8% < 1.2% or when the slag slurry fluidity is 120mm≤ and the SO3 mass fraction is ≤160mm, the tunnel slag is a Class II qualified slag; when the slag slurry fluidity is 120mm≤ and the SO3 mass fraction is 0.8% < 160mm, the tunnel slag is a Class III qualified slag; when the slag slurry fluidity is <120mm or the SO3 mass fraction is >1.2%, the tunnel slag is an unqualified slag.

[0051] The specific test results are shown in Table 2.

[0052] Table 2 Test results of performance indexes of slag powder

[0053] It can be seen from Table 2 that the performance of the tunnel slag powder in the 120m section is poor, and most of it is unqualified slag, with a small part being qualified Class II and Class III slag, indicating that the slag quality in this section is poor.

[0054] The disclosed embodiments are described to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is to be construed in the widest possible manner consistent with the principles and novel features disclosed herein.

Claims

1. A method for rapid evaluation of tunnel slag quality based on the comprehensive properties of slag powder, characterized in that: The following steps are involved: (1) Sampling: Randomly select tunnel slag with clean surface and natural air drying; (2) Powdering: Grind the obtained tunnel slag and pass it through a 0.075 mm sieve to collect the slag powder with a particle size less than 0.075 mm; (3) Testing: Rapidly test the fluidity of the collected slag powder slurry, and quickly test the sulfide and sulfate content of the collected slag powder in terms of SO3 mass; (4) Evaluation: The quality of tunnel slag is evaluated by the comprehensive performance of the slag slurry fluidity, sulfide and sulfate content; The step (1) specifically includes the following steps: before sampling, observe the state and size of the tunnel slag, randomly select multiple samples to form a collection of tunnel slag samples, and the tunnel slag samples should be clean, naturally air-dried, and have a length, width, and height greater than 5 cm; Random selection refers to sampling every 5-10 meters in the tunnel excavation direction, with 2 to 5 samples each time, with a mass of 10kg to 30kg; In step (3), the method for quickly testing the fluidity of the collected slag powder slurry specifically includes the following steps: Weigh 300g of slag powder, add 150g of water, and stir for 5 minutes to prepare a slag powder slurry. Then, put it into a truncated cone test mold with an upper diameter of 36mm, a lower diameter of 60mm, and a height of 60mm. After lifting the test mold, the average value of the maximum diameter in the vertical direction of the slag powder slurry when it flows on the glass plate for 30 seconds is used as the flowability of the slag powder slurry. In step (3), the method for quickly testing the sulfide and sulfate content of the collected slag powder specifically comprises the following steps: Mix 50-300g of slag powder thoroughly, place the mixed slag powder in a sample tray, and use a portable XRF detector to measure. Aim the instrument at the sample and measure different parts of the sample to obtain the SO3 mass fraction in different parts and take the average value. The different parts mentioned refer to the upper, middle and lower parts; The mixing speed is 475 r / min and the mixing time is 5 min; In step (2), the specific surface area of ​​the collected slag powder is 300 to 1000 m 2 / kg; In the step (4), when the fluidity of the tunnel slag powder slurry is ≥160mm and the SO3 mass fraction is ≤0.8%, the tunnel slag is a Class I qualified tunnel slag; when the fluidity of the tunnel slag powder slurry is ≥160mm and the SO3 mass fraction is 0.8% <1.2% or the fluidity of the tunnel slag powder slurry is 120mm≤<160mm and the SO3 mass fraction is ≤0.8%, the tunnel slag is a Class II qualified tunnel slag; when the fluidity of the tunnel slag powder slurry is 120mm≤<160mm and the SO3 mass fraction is 0.8% <1.2%, the tunnel slag is a Class III qualified tunnel slag; when the fluidity of the tunnel slag powder slurry is <120mm or the SO3 mass fraction is >1.2%, the tunnel slag is an unqualified tunnel slag.

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