Precise characterization method for manufactured sand particle shape

Abstract

This invention provides a precise characterization method for manufactured sand particle shape. The manufactured sand of all particle sizes is divided into two parts with different particle size ranges: one part with particle size and the other with mass and mass , respectively, and a particle size less than . The particle shape of the manufactured sand with particle size is characterized using the unit flow time method, while introducing flow rate to transform the particle shape result into a dimensionless value. The particle shape of the manufactured sand with particle size is accurately and three-dimensionally characterized using the sphericity method. Based on the mass ratio of the two parts, the particle shape results of the two parts are converted into a particle shape index, thus transforming the abstract quality of manufactured sand particle shape into a concrete numerical value that can be mathematically calculated. This invention combines the flow time method and the sphericity method to form a new detection method. The new method effectively overcomes the shortcomings of single detection methods while leveraging their advantages of precise detection for a specific particle size range.

Description

Technical Field

[0001] This invention relates to the field of manufactured sand particle shape, and in particular to a precise characterization method for manufactured sand particle shape. Background Technology

[0002] Manufactured sand is made from raw materials such as rocks, pebbles, mine waste rock, and tailings, processed through mechanical crushing and screening to produce particles with a diameter of 4.75–0.075 mm. Manufactured sand is already the most important sand source in my country's construction market, but it generally suffers from poor particle shape and other quality problems, making it difficult to adequately meet the sand requirements of the construction industry. Documents such as the Ministry of Industry and Information Technology's Joint Document

[2019] No. 239 clearly state that key technologies and processes such as particle shaping of manufactured sand should be prioritized, and investment in research and development and technological innovation of key equipment for aggregate shaping should be strengthened. Some scholars have also conducted research on manufactured sand shaping technology. To evaluate the shaping effect of manufactured sand, it is necessary to scientifically characterize its particle shape.

[0003] Because manufactured sand is mostly irregular in shape, small in size, and widely distributed in particle size distribution, it is very difficult to reasonably characterize its particle shape. At present, there are various methods for characterizing the particle shape of manufactured sand, such as the strip sieve method, the flow time method, the tap density method, and digital image processing technology, both domestically and internationally. However, these methods all have certain shortcomings, and the evaluation of the particle shape of manufactured sand is not accurate or comprehensive. None of these methods have been widely recognized and universally applied.

[0004] The bar sieve method characterizes the particle shape of manufactured sand based on the content of flaky particles. This method requires multiple sieving processes using square-hole and bar sieves, which is not only cumbersome but also prone to sieve clogging, resulting in overly coarse measurement results. Furthermore, the bar sieve method cannot measure particles smaller than 2.36 mm, thus its assessment of particle shape is not comprehensive. The American ASTM C33 / C33M-18 standard shares some similarities with the bar sieve method, measuring particle shape by the content of needle-like, flaky, and flat particles. The British BS 882:1992 roughly classifies manufactured sand particle shape into six types, but the boundaries between these types are somewhat blurred, and quantitative evaluation is not possible.

[0005] The flow-time method measures the time it takes for manufactured sand to flow through a flow-time meter, using the duration of this flow to characterize particle shape. This method is prone to jamming when measuring coarser particle sizes, leading to test failure. Furthermore, it is easily affected by the gradation of the manufactured sand, the relative positions of the particles, and the operator's skill. However, this method is more convenient and accurate in characterizing the particle shape of finer-grained manufactured sand.

[0006] In recent years, digital image processing methods based on 3D imaging and derived methods such as roundness and sphericity ratio have emerged. These methods require expensive precision equipment and specialized processing software, demanding high levels of information processing and analysis skills from operators. They are easily affected by factors such as lighting conditions and particle placement, and cannot accurately reflect the shape characteristics of flaky particles. Furthermore, these methods cannot characterize the shape of manufactured sand particles smaller than 1.18 mm. The sphericity similarity method in the "Technical Specification for High-Performance Concrete with Manufactured Sand for Highways" uses volume ratios to measure the quality of manufactured sand particle shape using digital image processing technology; however, this method also cannot characterize the shape of manufactured sand particles smaller than 1.18 mm. Summary of the Invention

[0007] The main objective of this invention is to provide a precise method for characterizing the particle shape of manufactured sand, thereby solving problems such as the inability to characterize the particle shape of manufactured sand in the full range of 4.75-0.075mm, sieve clogging, inaccurate measurement results, and susceptibility to interference from other factors, which are present in other methods for characterizing the particle shape of manufactured sand, such as the strip sieve method, flow time method, tap density method, and digital image processing technology.

[0008] The technical solution adopted in this invention is: a method for accurately characterizing the particle shape of manufactured sand, characterized in that: the manufactured sand of all particle sizes is divided into two parts with different particle size ranges, the manufactured sand with particle size d1 and d2, and their masses are m1 and m2 respectively, and the particle size of d1 is smaller than the particle size of d2.

[0009] The particle shape of manufactured sand with a particle size of d1 is characterized by the unit flow time method, and the flow rate is introduced to transform the particle shape results into dimensionless values.

[0010] The sphericity method was used to accurately and three-dimensionally characterize the particle shape of manufactured sand with a particle size of d2.

[0011] Based on the mass ratio of the two parts d1 and d2, the particle shape results of the two parts are converted into a particle shape index, thereby transforming the abstract quality of the particle shape of manufactured sand into a specific numerical value that can be mathematically calculated.

[0012] In the preferred embodiment, the particle size of the manufactured sand with particle size d1 is 0.075 to 1.18 mm, and the particle size of the manufactured sand with particle size d2 is 1.18 to 4.75 mm.

[0013] In the preferred embodiment, the sphericity method is used to characterize the 1.18–4.75 mm particle size. The sphericity method is as follows: the sphericity of manufactured sand is the ratio of the actual volume of the manufactured sand to the volume of its smallest circumscribed sphere;

[0014] N grains of manufactured sand, ranging from 1.18 to 4.75 mm, were randomly selected. The mass m of a single grain of manufactured sand was determined using an electronic analytical balance. z Calculate its true volume

[0015] Measure the maximum length d of the manufactured sand using calipers, and calculate the volume of the smallest circumscribed sphere of the manufactured sand with diameter d.

[0016] The sphericity of this manufactured sand is

[0017] Calculate the sphericity of these N grains of manufactured sand and determine their average sphericity value.

[0018] In the preferred embodiment, the unit flow time method is used to characterize the 0.075–1.18 mm particle size. The unit flow time method is defined as the ratio of the unit flow time of manufactured sand to that of standard sand.

[0019] The flow time (s) of manufactured sand ranging from 0.075 to 1.18 mm was measured using a flow time meter, and the unit flow time of the manufactured sand was calculated.

[0020] Weigh out a mass of m b The flow time (s) of standard sand ranging from 0.075 to 1.18 mm was measured using a flow time meter. b Calculate the unit flow time of the standard sand.

[0021] The flowability of this portion of manufactured sand is

[0022] In the preferred scheme, the method for calculating the particle shape index of the manufactured sand across all particle sizes is as follows:

[0023] The mass ratio of the 0.075–1.18 mm portion is m1 / (m1+m2), and the mass ratio of the 1.18–4.75 mm portion is m2 / (m1+m2).

[0024] The particle shape index of fully graded manufactured sand is The smaller the particle shape index, the closer the manufactured sand is to a sphere, and the better its shape.

[0025] This invention provides a precise method for characterizing the particle shape of manufactured sand. Addressing the shortcomings of previous methods for detecting the particle shape of manufactured sand, this application creatively combines two different detection methods to form a new method. This new method effectively overcomes the deficiencies of individual detection methods while leveraging their advantages in precise detection of a specific particle size. It minimizes interference from factors such as manufactured sand gradation and human operation, accurately characterizing the particle shape of manufactured sand across all particle sizes. Specifically, considering that the sphericity method is simple and effective in characterizing the particle shape of coarser manufactured sand, but inconvenient for finer particles, this invention proposes using the sphericity method to characterize the coarser particle shape of the 1.18–4.75 mm particle size range. Similarly, considering that the flow time method is simple and effective in characterizing the particle shape of finer manufactured sand, but prone to jamming and inaccurate measurement of coarser particles, this invention proposes using the unit flow time method to characterize the finer particle shape of the 0.075–1.18 mm particle size range. To enable digital characterization of the particle shape of manufactured sand across all particle sizes, the particle shape results of the 0.075–1.18 mm particle size range are converted into dimensionless flow rates, which can then be used to perform digital calculations with the particle shape results of the 1.18–4.75 mm particle size range. Ultimately, this allows the particle shape of manufactured sand across all particle sizes to be converted into calculable values. Detailed Implementation

[0026] A precise characterization method for the particle shape of manufactured sand is provided. The manufactured sand of all particle sizes is divided into two parts with different particle size ranges: manufactured sand with particle size d1 and d2, and their masses are m1 and m2, respectively, and the particle size of d1 is smaller than that of d2.

[0027] To address the limitation that the flow time method can effectively characterize the particle shape of finer-grained manufactured sand, but is prone to jamming and has poor accuracy when measuring coarser-grained sand, a unit flow time method is proposed to characterize the particle shape of manufactured sand with a particle size of d1, i.e., 0.075–1.18 mm. At the same time, the flow rate is introduced to transform the particle shape results into dimensionless values.

[0028] To address the limitation that the sphericity method can simply and effectively characterize the particle shape of coarser manufactured sand, but is inconvenient to operate on fine-grained manufactured sand, a method for accurately and three-dimensionally characterizing the particle shape of coarser manufactured sand with a particle size of d2, i.e., 1.18–4.75 mm, is proposed.

[0029] Based on the mass ratio of the two parts d1 and d2, the particle shape results of the two parts are converted into a particle shape index, thereby transforming the abstract quality of the particle shape of manufactured sand into a specific numerical value that can be mathematically calculated.

[0030] Weigh a certain mass of fully graded manufactured sand and sieve it into two parts: 0.075–1.18 mm and 1.18–4.75 mm, with masses m1 and m2 respectively.

[0031] In the preferred embodiment, the sphericity method is used to characterize the 1.18–4.75 mm particle size. The sphericity method is as follows: the sphericity of manufactured sand is the ratio of the actual volume of the manufactured sand to the volume of its smallest circumscribed sphere;

[0032] N grains of manufactured sand, ranging from 1.18 to 4.75 mm, were randomly selected. The mass m of a single grain of manufactured sand was determined using an electronic analytical balance. z Calculate its true volume

[0033] Measure the maximum length d of the manufactured sand using calipers, and calculate the volume of the smallest circumscribed sphere of the manufactured sand with diameter d.

[0034] The sphericity of this manufactured sand is

[0035] Calculate the sphericity of these N grains of manufactured sand and determine their average sphericity value.

[0036] In the preferred embodiment, the unit flow time method is used to characterize the 0.075–1.18 mm particle size. The unit flow time method is defined as the ratio of the unit flow time of manufactured sand to that of standard sand.

[0037] The flow time (s) of manufactured sand ranging from 0.075 to 1.18 mm was measured using a flow time meter, and the unit flow time of the manufactured sand was calculated.

[0038] Weigh out a mass of m b The flow time (s) of standard sand ranging from 0.075 to 1.18 mm was measured using a flow time meter. b Calculate the unit flow time of the standard sand.

[0039] The flowability of this portion of manufactured sand is

[0040] In the preferred scheme, the method for calculating the particle shape index of the manufactured sand across all particle sizes is as follows:

[0041] The mass ratio of the 0.075–1.18 mm portion is m1 / (m1+m2), and the mass ratio of the 1.18–4.75 mm portion is m2 / (m1+m2).

[0042] The particle shape index of fully graded manufactured sand is The smaller the particle shape index, the closer the manufactured sand is to a sphere, and the better its shape.

[0043] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A precise characterization method for the shape of manufactured sand particles, characterized by: Full-size manufactured sand is divided into two parts with different particle size ranges, with particle sizes of... and The manufactured sand, with masses of respectively and ,and Particle size less than granularity; Particle size was characterized using the unit flow time method. The particle shape of the manufactured sand was determined by introducing flow rate to transform the particle shape result into a dimensionless value. The sphericity method is used to accurately and three-dimensionally characterize the particle size. The shape of the machine-made sand particles; according to and The mass ratio of the two parts converts the particle shape results of the two parts into a particle shape index, thereby transforming the abstract quality of the particle shape of manufactured sand into a specific numerical value that can be mathematically calculated. The 0.075–1.18 mm particle size was characterized using the unit flow time method; The unit flow time method characterizes the flowability of manufactured sand as the ratio of the unit flow time of manufactured sand to the unit flow time of standard sand. The flow time (s) of 0.075~1.18mm manufactured sand was measured using a flow time meter, and the unit flow time of the manufactured sand was calculated. ; Weigh out the mass as The flow time of standard sand with a diameter of 0.075~1.18mm was measured using a flow time meter. Calculate the unit flow time of the standard sand. ; The flowability of this portion of manufactured sand is ; The method for calculating the particle shape index of manufactured sand of all particle sizes is as follows: The mass ratio of the 0.075~1.18mm portion is... / ( + The mass ratio of the 1.18~4.75mm portion is... / ( + ); The particle shape index of fully graded manufactured sand is = / ( + )+ / ( + The smaller the particle shape index, the closer the manufactured sand is to a spherical shape, and the better its shape. This represents the average sphericity value.

2. The method for accurately characterizing the shape of manufactured sand particles according to claim 1, characterized in that: Particle size is The size of the manufactured sand is 0.075~1.18mm, and the particle size is... The size of the manufactured sand is 1.18~4.75mm.

3. The method for accurately characterizing the shape of manufactured sand particles according to claim 1, characterized in that: The sphericity method was used to characterize the 1.18~4.75mm particle size. The sphericity method is as follows: the sphericity of manufactured sand is the ratio of the actual volume of the manufactured sand to the volume of its smallest circumscribed sphere; N grains of manufactured sand, ranging from 1.18 to 4.75 mm, were randomly selected. The mass of each grain of manufactured sand was determined using an electronic analytical balance. Calculate its true volume ; Measure the maximum length d of the manufactured sand using calipers, and calculate the volume of the smallest circumscribed sphere of the manufactured sand with diameter d. ; The sphericity of this manufactured sand is ; Calculate the sphericity of these N particles of manufactured sand and determine their average sphericity value. .

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