A quantitative evaluation method for rapid ultrasonic testing of homogeneity of lightweight aggregate concrete

Abstract

This invention discloses a quantitative evaluation method for the homogeneity of lightweight aggregate concrete based on rapid ultrasonic testing, belonging to the field of engineering materials testing technology. The method includes: S1, obtaining the shear wave velocity and longitudinal wave velocity at multiple test points of a series of lightweight aggregate concrete reference specimens; S2, calculating the shear modulus and bulk modulus at each test point of each reference specimen; S3, calculating the elastic modulus at each test point of each reference specimen; S4, constructing a relationship between the lightweight aggregate volume content, shear wave velocity, and longitudinal wave velocity based on the elastic modulus obtained in step S3; S5, obtaining the shear wave velocity and longitudinal wave velocity at each test point of the specimen to be tested, and calculating the lightweight aggregate volume content at each test point of the specimen to be tested based on the relationship; S6, evaluating the homogeneity of the specimen to be tested based on the lightweight aggregate volume content calculated in step S5. This invention solves the technical problem of insufficient accuracy in ultrasonic testing results for the homogeneity of lightweight aggregate concrete.

Description

Technical Field

[0001] This invention belongs to the field of engineering material testing technology, and in particular relates to a quantitative evaluation method for rapid ultrasonic testing of the homogeneity of lightweight aggregate concrete. Background Technology

[0002] Lightweight aggregate concrete, with its excellent properties such as light weight, high strength, and thermal insulation, has been widely used in bridge and building engineering. However, due to the significant density difference between lightweight aggregate and cementitious matrix, segregation, known as "aggregate floating and mortar settling," easily occurs during concrete construction. This phenomenon is mainly caused by the following factors: an excessively high water-cement ratio or excessively low mortar viscosity, resulting in insufficient mortar coating of the expanded clay aggregate; excessively long vibration time or excessive vibration force, exacerbating the separation of lightweight aggregate and mortar; and excessively high pouring height or too fast pouring speed, further promoting the floating of lightweight aggregate. These problems lead to reduced strength in the upper lightweight aggregate concentration area of ​​the concrete structure, while increased shrinkage in the lower mortar concentration area, thus seriously affecting the mechanical and durability properties of the structure. Therefore, it is necessary to strictly control relevant parameters and strengthen structural testing to ensure the uniformity and overall performance of lightweight aggregate concrete.

[0003] Currently, common methods for testing homogeneity in lightweight aggregate concrete include image analysis and density methods. However, these methods typically require sampling and cutting of the concrete, which are time-consuming and destructive. CT scanning is also used, but it is costly, requires sample pretreatment, is time-consuming, and cannot be implemented on-site, limiting its engineering applicability. In contrast, ultrasonic testing technology, due to its non-destructive, rapid, portable, and high-precision advantages, shows considerable application potential in the field of lightweight aggregate concrete. Homogeneity evaluation is mainly achieved through indirect methods, such as comparing differences in ultrasonic velocity or indirectly fitting physical quantities like compressive strength or elastic modulus from ultrasonic velocity. However, due to the significant variations in raw materials and mix proportions of lightweight aggregate concrete, there is a lack of a unified and precise formula for expressing the fitting relationship between ultrasonic waves and mechanical properties, which limits its practical application and affects the accuracy of ultrasonic testing results for lightweight aggregate concrete homogeneity. Summary of the Invention

[0004] To address the aforementioned shortcomings in existing technologies, this invention provides a quantitative evaluation method for the homogeneity of lightweight aggregate concrete based on rapid ultrasonic testing, thereby solving the technical problem of insufficient accuracy in ultrasonic testing results for the homogeneity of lightweight aggregate concrete in existing technologies.

[0005] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: a quantitative evaluation method for the homogeneity of lightweight aggregate concrete based on rapid ultrasonic testing, comprising the following steps:

[0006] S1. Obtain the transverse wave velocity at multiple test points on a series of lightweight aggregate concrete reference specimens. and longitudinal wave velocity ;

[0007] S2. Based on the shear wave velocity obtained in step S1 and longitudinal wave velocity Calculate the shear modulus at each test point of each reference specimen. and bulk modulus ;

[0008] S3. Based on the shear modulus calculated in step S2 and bulk modulus Calculate the elastic modulus at each test point of each reference specimen. ;

[0009] S4. Based on the elastic modulus obtained in step S3 Constructing lightweight aggregate volumetric admixture transverse wave velocity and longitudinal wave velocity Relationship;

[0010] S5. Obtain the transverse wave velocity at each test point of the test piece. and longitudinal wave velocity The volumetric content of lightweight aggregate at each test point of the test specimen is calculated based on the formula. ;

[0011] S6. Calculate the volumetric aggregate content at each test point based on the values ​​calculated in step S5. The homogeneity of the test specimen is evaluated.

[0012] The beneficial effects of this invention are as follows: In this solution, ultrasonic signals are acquired at different test points of the specimen using ultrasonic waves; and the physical characteristics of the material at different test points are calculated based on the ultrasonic signals acquired at different test points; then, a calculation formula is established between the volumetric content of lightweight aggregate and the physical characteristics of lightweight aggregate concrete; and the volumetric content of lightweight aggregate at each test point of the specimen is calculated based on this calculation formula. Thus, the overall distribution of lightweight aggregate in lightweight aggregate concrete can be calculated and evaluated; achieving a non-destructive, rapid, and high-precision homogeneity evaluation of lightweight aggregate concrete.

[0013] Further, in step S1, the steps for acquiring ultrasonic signals at multiple test points include:

[0014] S101. For each reference specimen, without using a coupling agent to couple with the test surface of the reference specimen, measure the transverse wave velocity at each test point. :

[0015]

[0016] in, For the first i Shear wave velocity at each test point For the first i The distance between the transmitting and receiving transducers at each test point, or the actual sound path of the ultrasonic wave. For the first i The time difference between the transmitting and receiving transducers at each test point;

[0017] S102. For each reference specimen, couple with the test surface of the reference specimen using a coupling agent, and measure the longitudinal wave velocity at each test point. :

[0018]

[0019] in, For the first i Shear wave velocity at each test point For the first i The time difference between the transmitting and receiving transducers at each test point.

[0020] The beneficial effect of the above further scheme is that it allows for the measurement of shear wave velocity. With longitudinal wave velocity Calculations are performed to provide data support and preparation for subsequent analysis.

[0021] Furthermore, the transverse wave velocities at each test point were obtained. and longitudinal wave velocity Determine the transverse wave velocity at each test point. Is it less than the longitudinal wave velocity? If so, then the transverse wave velocity at the test point is obtained. and longitudinal wave velocity If it meets the standard, otherwise, measure again.

[0022] The beneficial effect of the above further scheme is that it allows for the measurement of shear wave velocity. With longitudinal wave velocity Comparative verification was conducted to ensure the detected shear wave velocity was accurate. With longitudinal wave velocity The numerical values ​​are more accurate, avoiding errors in the test results caused by operational reasons during the testing process, which could affect the accuracy of subsequent calculation and analysis results.

[0023] Further, step S2 specifically includes:

[0024] S201, via transverse wave velocity Calculate the shear modulus at each test point :

[0025]

[0026]

[0027] In the formula, For the first i Shear modulus at each test point For the first i Apparent density of lightweight aggregate concrete at each test point For the first i Shear wave velocity at each test point For the first i Lightweight aggregate volume content at each test point The apparent density of the mortar phase in lightweight aggregate concrete. The apparent density of lightweight aggregate;

[0028] S202, Combined P-wave velocity transverse wave velocity and apparent density Calculate the bulk modulus of lightweight aggregate concrete at each test point. :

[0029]

[0030] In the formula, For the first i Bulk modulus at each test point For the first i Shear wave velocity at each test point For the first i Shear wave velocity at each test point.

[0031] The beneficial effect of the above further scheme is: based on the detected shear wave velocity With longitudinal wave velocity Information such as shear modulus With bulk modulus This calculation facilitates the subsequent adjustment of the volumetric admixture of lightweight aggregate. Perform the calculation.

[0032] Furthermore, in step S3, the elastic modulus The expression is:

[0033]

[0034] In the formula, For the first i The elastic modulus at each test point For the first i Bulk modulus at each test point For the first iShear modulus at each test point.

[0035] Further, step S4 specifically includes:

[0036] S401, Constructing the volumetric admixture of lightweight aggregate With elastic modulus Relationship:

[0037]

[0038] In the formula, For the first i Lightweight aggregate volume content at each test point For the first i The elastic modulus at each test point a Lightweight aggregate volumetric admixture The coefficient of the quadratic term, The elastic modulus of the mortar phase. The elastic modulus of lightweight aggregate, b Lightweight aggregate volumetric admixture The coefficient of the first term;

[0039] S402, based on the volumetric admixture of lightweight aggregate With elastic modulus Relationship to construct lightweight aggregate volume content transverse wave velocity and longitudinal wave velocity Relationship:

[0040]

[0041]

[0042] In the formula, For the density of lightweight aggregate, The apparent density of the mortar phase in lightweight aggregate concrete. For a polynomial related to the speed of sound, For the first i Shear wave velocity at each test point For the first i Shear wave velocity at each test point;

[0043] S403. Obtain the quadratic coefficients by fitting data from lightweight aggregate concrete reference specimens. a coefficient of the first term b .

[0044] The beneficial effects of the above further scheme are: based on the volumetric admixture of lightweight aggregate With elastic modulus The relationship between ultrasonic velocity and lightweight aggregate volume fraction The relationship between them is constructed as a two-variable linear equation, which makes the relationship between the volumetric admixture of lightweight aggregates... During calculations, the volumetric content of lightweight aggregate can be quickly determined based on information such as the detected ultrasonic velocity and the discriminant of a linear equation in two variables. Does the numerical value have a unique solution for the lightweight aggregate volumetric admixture? The efficiency of calculation and discrimination can be greatly improved.

[0045] Further, step S6 specifically involves: calculating the volumetric content of lightweight aggregate at each test point based on the values ​​obtained in step S5. Calculate the volumetric admixture of lightweight aggregate. coefficient of variation CV According to the coefficient of variation CV The homogeneity of lightweight aggregate concrete specimens was evaluated:

[0046]

[0047] In the formula, The standard deviation of lightweight aggregate volume content. This represents the average volumetric content of lightweight aggregate. For the first i Lightweight aggregate volume content at each test point This represents the total number of test points.

[0048] The beneficial effects of the above further scheme are: by adjusting the volumetric admixture of lightweight aggregate... coefficient of variation CV Calculations are performed to facilitate subsequent evaluation of the homogeneity of the lightweight aggregate concrete specimens.

[0049] Furthermore, the statement based on the coefficient of variation CV The homogeneity of lightweight aggregate concrete specimens was evaluated by determining the coefficient of variation. CV If the value is less than or equal to the coefficient of variation threshold, then the lightweight aggregate is evenly distributed; otherwise, the lightweight aggregate is unevenly distributed.

[0050] The beneficial effect of the above-mentioned further scheme is that it enables rapid determination of the coefficient of variation of lightweight aggregate at each test point in the specimen when assessing the overall homogeneity of the lightweight aggregate concrete specimen. CV To ensure the ease of evaluation of the homogeneity of lightweight aggregate concrete. Attached Figure Description

[0051] Figure 1 This is a flowchart of a quantitative evaluation method for rapid ultrasonic detection of the homogeneity of lightweight aggregate concrete in an embodiment of the present invention.

[0052] Figure 2 This is a distribution diagram of ultrasonic detection points in an embodiment of the present invention;

[0053] Figure 3 This is a schematic diagram of the ultrasonic detection structure in an embodiment of the present invention. Detailed Implementation

[0054] The reference numerals in the accompanying drawings of the instruction manual include: 1. Lightweight aggregate concrete; 2. Test point; 3. Sound path; 4. Shear wave transmitting transducer; 5. Shear wave receiving transducer; 6. Shear wave acquisition instrument; 7. Longitudinal wave transmitting transducer; 8. Longitudinal wave receiving transducer; 9. Longitudinal wave acquisition instrument.

[0055] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0056] In one embodiment of the present invention, a quantitative evaluation method for the homogeneity of lightweight aggregate concrete based on rapid ultrasonic detection is provided, such as... Figure 1 As shown, it includes the following steps:

[0057] S1. Prepare a series of lightweight aggregate concrete reference specimens and test specimens, and obtain the transverse wave velocity at multiple test points on each lightweight aggregate concrete reference specimen and each test specimen. and longitudinal wave velocity ;

[0058] In this embodiment, the lightweight aggregate concrete specimen is a cube, and the dimensions of the cube are length × thickness × height = d 1× d 2× h , d 1≥10cm, 40cm≥ d 2≥10cm, h ≥10cm; the test point on the test surface is the thickness = d For two parallel surfaces in two directions, the measured thickness is ≤40cm, and the concrete age is ≥7 days.

[0059] Specifically, in this embodiment, the lightweight aggregate selected is fly ash composite ceramsite (where the ceramsite particle size is approximately 6 mm, the compressive strength is 7 MPa, and the apparent density of the ceramsite is 1409 kg / m³). 3 (The saturated mass water absorption rate is approximately 8.2%), and the concrete specimens are 150mm×150mm×150mm cube specimens.

[0060] In this embodiment, five sets of experimental mix proportions were designed for comparative analysis. Specimen C1 was the baseline specimen with 0% ceramsite content; specimens LC2-LC5 were to be tested, with LC2 and LC3 containing 30% ceramsite and LC4 and LC5 containing 50%. The apparent density of specimens LC2 and LC3 was 2213 kg / m³, and the apparent density of specimens LC4 and LC5 was 2048 kg / m³. The mix proportions of each lightweight aggregate concrete specimen are shown in Table 1.

[0061] Table 1. Mix proportions of lightweight aggregate concrete 1 for the test subjects

[0062]

[0063] Of the above specimens, LC2 and LC4 were vibrated for 5 seconds after casting, while LC3 and LC5 were vibrated for 20 seconds. All specimens were placed under standard curing conditions (temperature 20±2℃, relative humidity ≥95%) for 28 days before performance testing.

[0064] In the arrangement of test points 2 on the lightweight aggregate concrete specimen 1, multiple test points 2 are distributed in multiple layers on the lightweight aggregate concrete specimen 1, with each layer of multiple test points ≥2cm apart, the horizontal spacing ≥2cm, and the number of test points in each layer being the same and ≥3; as shown in the attached figure. Figure 2 As shown, in this embodiment, the side of the specimen is divided into 5 measurement areas along the height direction (interlayer height h1=30mm), and 3 measuring points are arranged at equal intervals in each layer. The ultrasonic parameter characteristics at different measuring points are obtained by ultrasonic testing, thereby obtaining aggregate distribution data at each measuring point to evaluate the effect of vibration time on homogeneity.

[0065] In step S1, when performing ultrasonic testing on the specimen, as shown in the attached... Figure 3 As shown, the radiating surfaces of the longitudinal wave transmitting transducer 7 and the longitudinal wave receiving transducer 8 are coupled with a coupling agent to ensure good coupling with the test surface of the specimen. The radiating surfaces of the transverse wave transmitting transducer 4 and the transverse wave receiving transducer 5 are not coupled with a coupling agent. The specific details of the coupling agent are existing technology and will not be elaborated here. When the transverse wave acquisition instrument 6 and the longitudinal wave acquisition instrument 9 are used to sequentially acquire the first wave of the ultrasonic transverse wave and longitudinal wave, the geometric center overlap error between the transmitting end face and the receiving end face of the two transducers is ≤1mm, realizing the spatial homogeneity of wave type excitation and reception, and ensuring the consistency of the ultrasonic wave propagation path in the lightweight aggregate concrete 1. Specifically, when acquiring the ultrasonic signal on the lightweight aggregate concrete 1 specimen, multiple test points i are arranged on the series of lightweight aggregate concrete 1 specimens to be tested. i =1~ n Then, the transverse wave velocity at each test point 2 was measured sequentially. With longitudinal wave velocity Take measurements.

[0066] In step S1, when performing ultrasonic testing on each test point 2, each test point 2 is measured 3 times consecutively. The acoustic time measurement is accurate to 0.1 μs, the size measurement is accurate to 1 mm, and the ultrasonic velocity is accurate to 0.01 km / s. The ultrasonic velocity representative value is the average sound velocity value of the 3 measurements at that test point.

[0067] Shear wave velocity at each test point 2 in step S1 The calculation formula is Longitudinal wave velocity at each test point 2 The calculation formula is ,in, This indicates the distance between the transmitting and receiving transducers, or the actual sound path of the ultrasonic wave. This represents the time difference between the transmitting transducer and the receiving transducer. Table 2 shows the ultrasonic velocity measurement results for each reference specimen and the test specimen in this embodiment.

[0068] Table 2. Results of Ultrasonic Velocity Measurement

[0069]

[0070] Analysis of the ultrasonic test results in Table 2 shows that lightweight aggregate concrete specimens with different ceramsite volume fractions exhibited significant differences in acoustic performance. Specifically, the ultrasonic propagation speed range for specimens with 30% ceramsite content was: shear wave 2.66~2.77 km / s, longitudinal wave 4.54~4.79 km / s; while the corresponding parameters for specimens with 60% ceramsite content were shear wave 2.41~2.58 km / s, and longitudinal wave 4.28~4.48 km / s. This difference in sound velocity is mainly due to the change in the internal structure of the material caused by the variation in ceramsite content. A gradient variation in ultrasonic velocity was observed in different parts of the same specimen, with the wave velocity in the bottom layer generally higher than that in the top layer. This phenomenon may be related to the aggregate settlement and uneven distribution of pores during the material forming process. Ultrasonic waves are highly sensitive to changes in the internal microstructure of materials and can effectively detect the distribution of lightweight aggregate in the concrete matrix.

[0071] Step S1 also includes S11, checking the shear wave velocity. With longitudinal wave velocity To verify, when the shear wave velocity With longitudinal wave velocity When the verification results do not verify the comparison conditions, specifically regarding the shear wave velocity... With longitudinal wave velocity During verification, the transverse wave velocity is compared. Is it less than the longitudinal wave velocity? ,like Less than The accuracy of the measurement is then verified, and the shear wave velocity is measured. With longitudinal wave velocity Remeasure.

[0072] S2. Based on the shear wave velocity obtained in step S1 and longitudinal wave velocity Calculate the shear modulus at each test point of the reference specimen. and bulk modulus Specifically, this includes:

[0073] S201, based on the wave theory in solid elastic media, uses the transverse wave velocity... Determine the shear modulus at each test point 2. ; Shear modulus at each test point 2 of the reference specimen The calculation formula is as follows:

[0074]

[0075] In the formula, For the first i Shear modulus at each test point For the first i Apparent density of lightweight aggregate concrete at each test point For the first i Shear wave velocity at each test point.

[0076] S202, Combined P-wave velocity transverse wave velocity and apparent density Calculate the bulk modulus at each test point 2. Among them, the bulk modulus at each test point 2 The calculation formula is as follows:

[0077]

[0078] In the formula, For the first i The apparent density of lightweight aggregate concrete 1 at each test point For the first i Bulk modulus at each test point For the first i Shear wave velocity at each test point For the first i Shear wave velocity at each test point.

[0079] S3. Based on the shear modulus calculated in step S2 and bulk modulus Calculate the elastic modulus at each test point of the reference specimen. Specifically, in step S3, the bulk modulus of each test point 2 of the reference specimen calculated in step S2 can be used as a reference. With shear modulus Through the generalized Huco's law E - K - G” The expression for the elastic modulus of lightweight aggregate concrete 1 The elastic modulus at test point 2 of the lightweight aggregate concrete 1 was determined. The calculation formula is:

[0080]

[0081] In the formula, For the first i The elastic modulus at each test point For the first i Bulk modulus at each test point For the first i Shear modulus at each test point.

[0082] S4. Based on the elastic modulus obtained in step S3 Constructing lightweight aggregate volumetric admixture transverse wave velocity and longitudinal wave velocity The relational expression; where the content of the relational expression construction is specifically as follows:

[0083] Constructing lightweight aggregate volume content With elastic modulus Relationship:

[0084]

[0085] In the formula, For the first i Lightweight aggregate volume content at each test point For the first i The elastic modulus at each test point The elastic modulus of the mortar phase. The elastic modulus of lightweight aggregate, For the density of lightweight aggregate, a Lightweight aggregate volumetric admixture The coefficient of the quadratic term, b Lightweight aggregate volumetric admixture The coefficient of the first-order term.

[0086] When constructing the formula for calculating the relationship between ultrasonic velocity and lightweight aggregate volume fraction, wave theory can be used to determine the relationship between lightweight aggregate volume fraction and ultrasonic velocity. With elastic modulus The relationship is constructed; specifically, the bulk modulus in step S2 is... With shear modulus The calculation formula, and the elastic modulus in step S3. Substituting the calculation formula into the volumetric admixture of lightweight aggregate With elastic modulus The relation can be obtained as follows:

[0087]

[0088] Apparent density It is related to the volumetric content of lightweight aggregate, among which apparent density The calculation formula is:

[0089]

[0090] In the formula, The volumetric content of lightweight aggregate at test point 2 of lightweight aggregate concrete 1 is given. The apparent density of the mortar phase in lightweight aggregate concrete is given. The apparent density of lightweight aggregate.

[0091] Therefore, apparent density Substituting the calculation formula into the volumetric admixture of lightweight aggregate With elastic modulus The relation, after simplification, can be obtained as follows:

[0092]

[0093] In the formula, For the density of lightweight aggregate, The apparent density of the mortar phase in lightweight aggregate concrete. For the first i Shear wave velocity at each test point For the first i Shear wave velocity at each test point; Represents a polynomial related to the speed of sound. .

[0094] The quadratic coefficients were obtained by fitting data from the benchmark specimens of lightweight aggregate concrete. a coefficient of the first term b In this preferred embodiment, the fitted a The value is 0.272. b The value is 0.042. a and b The specific fitting process is based on existing technology and will not be elaborated here.

[0095] S5. Obtain the transverse wave velocity at the test points of each test piece. and longitudinal wave velocity And calculate the wave velocity of each shear wave according to the formula. and longitudinal wave velocity Lightweight aggregate volume content ;

[0096] In terms of the volumetric admixture of lightweight aggregate The calculation is performed as follows:

[0097] Solve for the simplified lightweight aggregate volume content in step S4. With elastic modulus Lightweight aggregate volume ratio in the formula and the coefficients of the quadratic term obtained after fitting. a coefficient of the first term b The volumetric content of lightweight aggregate can be obtained by using the formula for solving a quadratic equation. The formula for solving the relation is:

[0098]

[0099] in The discriminant for solving a quadratic equation in one variable is... The formula for calculation is:

[0100]

[0101] According to the definition of solving a quadratic equation, the volumetric admixture of lightweight aggregate... When solving, the discriminant can be... The value is used to make a judgment when When it equals 0, then the dosage is... There is only one solution; when When the value is greater than 0, there are two solutions. Removing the results with values ​​less than 0 and greater than 1 will yield a unique solution.

[0102] In the above formula, the elastic modulus of the mortar phase is... The measurements were obtained using mortar test blocks with the same mix proportion as the mortar in lightweight aggregate concrete 1. The specific details of the mortar test block measurements are existing technology and will not be elaborated here.

[0103] When performing the above calculations, the data from the tests in step S1 can be entered into a computer program for calculation to obtain the volumetric weight of lightweight aggregate at each test point 2. The specific details of numerical calculations using computer programs are existing technologies and will not be elaborated upon here.

[0104] S6. Calculate the volumetric aggregate content at each test point based on the values ​​calculated in step S5. The homogeneity of the test specimens was evaluated. Specifically, the volumetric aggregate content at each test point 2 of each test specimen was calculated. coefficient of variation CV Calculations are performed, including the coefficient of variation. CV The calculation formula is:

[0105]

[0106] In the formula, The standard deviation of the volumetric content of lightweight aggregate is given by , where the standard deviation is . The calculation formula is:

[0107]

[0108] The average volumetric content of lightweight aggregate is given. The calculation formula is:

[0109]

[0110] In the formula, n is the total number of test points. For the first i Lightweight aggregate volume content at each test point

[0111] When evaluating the homogeneity of lightweight aggregate concrete test specimens, the coefficient of variation of each test specimen is determined. CV Is the value less than or equal to the coefficient of variation threshold? CV When the value is less than or equal to the coefficient of variation threshold, the lightweight aggregate is uniformly distributed. CV When the coefficient of variation exceeds the threshold, the lightweight aggregate distribution is uneven; preferably, in this embodiment, the coefficient of variation threshold is 10%, that is, when evaluating the homogeneity of the lightweight aggregate concrete specimen 1, when coefficient of variation CV When the content is ≤10%, the lightweight aggregate is evenly distributed. CV When the content is greater than 10%, the distribution of lightweight aggregate is uneven.

[0112] Specifically, in this embodiment, the calculation results of the admixture dosage and the homogeneity evaluation content of each lightweight aggregate concrete 1 test specimen are shown in Table 3:

[0113] Table 3 Calculation and evaluation results of doping levels for each test specimen

[0114]

[0115] Table 3 shows that the volumetric ceramsite content of specimens LC3 and LC5 exhibits significant non-uniformity along the vertical direction, with relatively large coefficients of variation. This phenomenon can be attributed to the upward migration of lightweight aggregates due to their lower density during prolonged vibration of the fresh concrete, leading to a gradient change in the distribution of ceramsite within the specimens and exacerbating the material's non-uniformity. These results further verify the sensitivity of ultrasonic testing technology to changes in the internal structure of lightweight aggregate concrete 1, and also indicate that the vibration process has a significant impact on the uniformity of lightweight aggregate distribution. Therefore, in practical engineering, it is necessary to optimize the construction process to improve the stability of material properties.

[0116] Compared to existing technologies, this solution uses ultrasonic testing to acquire ultrasonic signals at different test points on the specimen; calculates the physical characteristics of the material at different test points based on the wave theory in solid elastic media; and then establishes a calculation formula between the volumetric admixture of lightweight aggregate and the physical characteristics of lightweight aggregate concrete. It can obtain multi-dimensional data such as ultrasonic velocity, bulk modulus, shear modulus, and lightweight aggregate admixture in local areas at different test points of the component, enabling the evaluation of the homogeneity of the entire cross-section of lightweight aggregate concrete components, and achieving non-destructive, rapid, and high-precision homogeneity evaluation of lightweight aggregate concrete.

[0117] This solution utilizes ultrasonic technology, requiring only the placement of measuring points on the specimen surface to complete the test, fully preserving the integrity of the component and ensuring high repeatability. During the testing process, a portable ultrasonic testing instrument is sufficient for rapid on-site testing. The equipment is lightweight, easy to operate, significantly reducing testing costs, and requires no dedicated testing environment. Testing can be completed simply by placing measuring points on the component surface, avoiding the cumbersome process of sample transportation and preparation, and improving the adaptability of the testing method to different testing environments.

[0118] Meanwhile, this scheme constructs a precise calculation model for lightweight aggregate volumetric content and ultrasonic parameters through multi-parameter fusion, significantly improving testing accuracy compared to traditional non-destructive testing methods. This model achieves direct quantitative conversion of ultrasonic parameters to lightweight aggregate volumetric content, accurately characterizing the key performance indicator of lightweight aggregate content. It effectively overcomes the limitations of existing indirect evaluation methods, providing a more precise technical solution for the homogeneity testing of lightweight aggregate concrete.

Claims

1. A quantitative evaluation method for the homogeneity of lightweight aggregate concrete based on rapid ultrasonic testing, characterized in that, Includes the following steps: S1. Obtain the transverse wave velocity at multiple test points on a series of lightweight aggregate concrete reference specimens. and longitudinal wave velocity ; S2. Based on the shear wave velocity obtained in step S1 and longitudinal wave velocity Calculate the shear modulus at each test point of each reference specimen. and bulk modulus ; S3. Based on the shear modulus calculated in step S2 and bulk modulus Calculate the elastic modulus at each test point of each reference specimen. ; S4. Based on the elastic modulus obtained in step S3 Constructing lightweight aggregate volumetric admixture transverse wave velocity and longitudinal wave velocity Relationship; S5. Obtain the transverse wave velocity at each test point of the test piece. and longitudinal wave velocity The volumetric content of lightweight aggregate at each test point of the test specimen is calculated based on the formula. ; S6. Calculate the volumetric aggregate content at each test point based on the values ​​calculated in step S5. The homogeneity of the test specimen is evaluated. Step S4 specifically involves: S401, Constructing the volumetric admixture of lightweight aggregate With elastic modulus Relationship: In the formula, For the first i Lightweight aggregate volume content at each test point For the first i The elastic modulus at each test point a Lightweight aggregate volumetric admixture The coefficient of the quadratic term, The elastic modulus of the mortar phase. The elastic modulus of lightweight aggregate, b Lightweight aggregate volumetric admixture The coefficient of the first term; S402, based on the volumetric admixture of lightweight aggregate With elastic modulus Relationship to construct lightweight aggregate volume content transverse wave velocity and longitudinal wave velocity Relationship: In the formula, The apparent density of lightweight aggregate, The apparent density of the mortar phase in lightweight aggregate concrete is given. For a polynomial related to the speed of sound, For the first i Shear wave velocity at each test point For the first i Shear wave velocity at each test point; S403. Obtain the quadratic coefficients by fitting data from lightweight aggregate concrete reference specimens. a coefficient of the first term b ; Step S6 specifically involves: calculating the volumetric aggregate content at each test point based on the values ​​in step S5. Calculate the volumetric admixture of lightweight aggregate. coefficient of variation CV According to the coefficient of variation CV The homogeneity of lightweight aggregate concrete specimens was evaluated: In the formula, The standard deviation of lightweight aggregate volume content. This represents the average volumetric content of lightweight aggregate. For the first i Lightweight aggregate volume content at each test point This represents the total number of test points.

2. The quantitative evaluation method for the homogeneity of lightweight aggregate concrete based on rapid ultrasonic testing according to claim 1, characterized in that, Step S1 specifically involves: S101. For each reference specimen, without using a coupling agent to couple with the test surface of the reference specimen, measure the transverse wave velocity at each test point. : in, For the first i Shear wave velocity at each test point For the first i The distance between the transmitting and receiving transducers at each test point, or the actual sound path of the ultrasonic wave. For the first i The time difference between the transmitting and receiving transducers at each test point; S102. For each reference specimen, couple with the test surface of the reference specimen using a coupling agent, and measure the longitudinal wave velocity at each test point. : in, For the first i Shear wave velocity at each test point For the first i The time difference between the transmitting and receiving transducers at each test point.

3. The quantitative evaluation method for the homogeneity of lightweight aggregate concrete based on rapid ultrasonic testing according to claim 2, characterized in that, The transverse wave velocity at each test point was obtained. and longitudinal wave velocity Determine the transverse wave velocity at each test point. Is it less than the longitudinal wave velocity? If so, then the transverse wave velocity at the test point is obtained. and longitudinal wave velocity If it meets the standard, otherwise, measure again.

4. The quantitative evaluation method for the homogeneity of lightweight aggregate concrete based on rapid ultrasonic testing according to claim 1, characterized in that, Step S2 specifically involves: S201, via transverse wave velocity Calculate the shear modulus at each test point : In the formula, For the first i Shear modulus at each test point For the first i Apparent density of lightweight aggregate concrete at each test point For the first i Shear wave velocity at each test point For the first i Lightweight aggregate volume content at each test point The apparent density of the mortar phase in lightweight aggregate concrete is given. The apparent density of lightweight aggregate; S202, Combined P-wave velocity transverse wave velocity and apparent density Calculate the bulk modulus at each test point : ； In the formula, For the first i Bulk modulus at each test point For the first i Shear wave velocity at each test point For the first i Shear wave velocity at each test point.

5. The quantitative evaluation method for the homogeneity of lightweight aggregate concrete based on rapid ultrasonic testing according to claim 1, characterized in that, The elastic modulus in step S3 The expression is: In the formula, For the first i The elastic modulus at each test point For the first i Bulk modulus at each test point For the first i Shear modulus at each test point.

6. The quantitative evaluation method for the homogeneity of lightweight aggregate concrete based on rapid ultrasonic testing according to claim 1, characterized in that, According to the coefficient of variation CV The homogeneity of lightweight aggregate concrete specimens was evaluated by determining the coefficient of variation. CV If the value is less than or equal to the coefficient of variation threshold, then the lightweight aggregate is evenly distributed; otherwise, the lightweight aggregate is unevenly distributed.

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