Normalized method for characterizing homogeneity of lightweight aggregate concrete

Abstract

A normalized method for characterizing the homogeneity of lightweight aggregate concrete, the method comprising: preparing a lightweight aggregate concrete specimen (S1); cutting the lightweight aggregate concrete specimen along a height direction and through a central axis in the height direction, so as to obtain n cut sections ai (S2); photographing each cut section ai and performing image recognition, obtaining a total area A and a lightweight aggregate phase area Ai of each cut section ai, and calculating a lightweight aggregate phase area ratio bi = Ai / A (S3); and on the basis of the differences |bi-bj| between the lightweight aggregate phase area ratios bi of the respective cut sections in a same lightweight aggregate concrete specimen, determining the homogeneity of the lightweight aggregate concrete (S4). A normalized approach for calculating the homogeneity of lightweight aggregate concrete is used to take into account complete section information of lightweight aggregate concrete specimens and the impact of differences in lightweight aggregate usage on the homogeneity of different lightweight aggregate concretes, thereby achieving rapid and accurate determination of the homogeneity level of aggregate distribution in the lightweight aggregate concrete.

Description

A normalized method for characterizing the homogeneity of lightweight aggregate concrete Technical Field

[0001] The present disclosure relates to the technical field of engineering material testing, and more particularly, to a normalized lightweight aggregate concrete homogeneity characterization method. Background Art

[0002] Lightweight aggregate concrete is widely used due to its many advantages such as light weight, thermal insulation, fire resistance, earthquake resistance and good durability. However, the apparent density of lightweight aggregate is relatively small, which is significantly different from the density of other components in concrete, resulting in homogeneity problems. The uneven distribution of lightweight aggregate in concrete seriously affects the performance of concrete, thereby limiting its application in structural engineering.

[0003] Currently, there are two main approaches to studying the homogeneity of lightweight aggregate concrete. One involves using the stratification method to determine the wet apparent density or aggregate mass of fresh concrete by taking the upper and lower concrete mixtures and calculating the stratification based on the mixture density and aggregate mass to determine the homogeneity of lightweight aggregate concrete. The other involves cutting the concrete specimen into equal parts vertically and testing the strength of the upper and lower concrete layers for comparative analysis, or slicing the concrete specimen and performing image recognition on the cross-section to perform a simple comparative analysis of the aggregate distribution quantity and area across the cross-section. These methods either only consider the upper and lower concrete layers without analyzing the data in the middle of the specimen, which reduces the authenticity of the concrete homogeneity determination results, or only compare the aggregate distribution of the test section, resulting in limitations in concrete homogeneity determination.

[0004] Chinese patent application number 201210136478.8 discloses a method for testing the homogeneity of lightweight aggregate concrete. This method involves sectioning a lightweight aggregate concrete specimen along a plane perpendicular to the casting surface. The cross-section is then divided into upper and lower sections for imaging. The images of the upper and lower sections are then input into image analysis software to calculate the amount and area of ​​lightweight aggregate in each section. Based on the distribution of lightweight aggregate in the cross-section, the homogeneity of the concrete is then determined. While this method is convenient to use, it has limitations. It cannot quantitatively compare the homogeneity of lightweight aggregate concretes with different aggregate contents and types. Furthermore, dividing the cross-section into only upper and lower sections is not accurate enough.

[0005] Different lightweight aggregate concretes have different amounts and types of lightweight aggregate. The aforementioned methods for evaluating lightweight aggregate homogeneity are unable to eliminate the effects of these differences on the homogeneity of different lightweight aggregate concretes. They are also unable to quantitatively compare the distribution of lightweight aggregate between different lightweight aggregate concretes, significantly limiting their scope of application. In fact, the engineering and scientific research communities have a greater need for methods to quantitatively compare the homogeneity of different lightweight aggregate concretes. If such methods could be implemented, they would be able to better assess the pros and cons of lightweight aggregate flotation suppression technologies and more comprehensively determine lightweight aggregate homogeneity and its impact on performance.

[0006] Therefore, a fast and accurate method to test the homogeneity of lightweight aggregate distribution in lightweight aggregate concrete is needed.

[0007] Summary of the Invention

[0008] In view of this, the main purpose of the present disclosure is to provide a normalized lightweight aggregate concrete homogeneity characterization method to solve the problem that the current concrete homogeneity determination methods based on experiments or digital image processing technology have limitations.

[0009] In order to achieve the above objectives, the present disclosure provides a normalized lightweight aggregate concrete homogeneity characterization method, the method comprising:

[0010] Preparation of lightweight aggregate concrete specimens;

[0011] The lightweight aggregate concrete specimen is cut along the height direction and through the central axis of the height direction to obtain n slice sections a i , where i = 1, ..., n;

[0012] For each slice section a i Take pictures and perform image recognition to obtain each slice section a i The total area A and the lightweight aggregate phase area A i , calculate the lightweight aggregate phase area ratio b i =A i / A;

[0013] According to the lightweight aggregate phase area ratio b between each slice section in the same lightweight aggregate concrete specimen i The difference of |b i -b j |, determine the homogeneity of the lightweight aggregate concrete, where i = 1, ..., n, j = 1, ..., n.

[0014] In the above scheme, the lightweight aggregate concrete specimen is cut along the height direction and through the central axis of the height direction to obtain n slice sections a i In the steps, the distribution of lightweight aggregate in any slice section is uniform.

[0015] In the above scheme, the area ratio b of the lightweight aggregate phase between the sections of the same lightweight aggregate concrete specimen is i The difference of |b i -b j |, determine the homogeneity of the lightweight aggregate concrete, including: comparing the lightweight aggregate phase area ratio b between the sections of the same lightweight aggregate concrete specimen i The difference of |b i -b j |, if |b i -b j |>threshold, the lightweight aggregate concrete is judged to be inhomogeneous; if |b i -b j |≤threshold, the lightweight aggregate concrete is judged to be homogeneous.

[0016] In the above solution, the threshold is 4% to 6%.

[0017] In the above solution, after determining that the lightweight aggregate concrete is homogeneous, the method further includes: calculating and characterizing the homogeneity of the lightweight aggregate distribution in the lightweight aggregate concrete.

[0018] In the above scheme, the calculation and characterization of the homogeneity of the lightweight aggregate distribution in the lightweight aggregate concrete includes: calculating each slice section a i Lightweight aggregate distribution uniformity coefficient S i ; According to each slice section a i Lightweight aggregate distribution uniformity coefficient S i , characterizing the homogeneity of lightweight aggregate distribution in the lightweight aggregate concrete.

[0019] In the above scheme, the calculation of each slice section a i Lightweight aggregate distribution uniformity coefficient S i , including: for each slice section a i Divide the area equally along the height direction, and the single slice section a i The number of partitions is m, and the height of each partition is h1. For the i-th slice section a i , from bottom to top the partitions are marked as a i，j , where i = 1, ..., n; j = 1, ..., m, and each partition a is obtained i，j Lightweight aggregate area A i，j and lightweight aggregate area ratio b i，j , calculate each slice section a i Lightweight aggregate distribution uniformity coefficient S i for:

[0020] in, is the standard deviation of the lightweight aggregate area ratio in the slice section, SNOR，i is the standardized parameter of the standard deviation of the lightweight aggregate area ratio in the slice section, and S NOR，i =1 / 2(b i -b i 2 ), lightweight aggregate distribution uniformity coefficient S i Between 0 and 1, it is possible to achieve horizontal quantitative comparison of aggregate distribution homogeneity in lightweight aggregate concrete with different aggregate contents and types.

[0021] In the above scheme, the i Lightweight aggregate distribution uniformity coefficient S i , characterizes the homogeneity of lightweight aggregate distribution in the lightweight aggregate concrete, including: according to each slice section a i Lightweight aggregate distribution uniformity coefficient S i , when the homogeneity coefficient S i The closer it is to 0, the more uniform the distribution of lightweight aggregate in lightweight aggregate concrete is; when the homogeneity coefficient S i The closer it is to 1, the worse the homogeneity of lightweight aggregate concrete.

[0022] In the above scheme, the preparation of lightweight aggregate concrete specimens includes: determining the gradation curve of lightweight aggregate, the maximum particle size d max , average particle size d ave ; Determine the shape and size of the lightweight aggregate concrete specimen used. The shape of the lightweight aggregate concrete specimen is a prism or a cylinder, where the size of the prism is length × width × height = d1 × d1 × h1, and the size of the cylinder is diameter × height = d2 × h2, and d1 ≥ 10 × d max , h1≥10×d max ; d2≥10×d max , h2≥10×d max ; Prepare lightweight aggregate concrete specimens and cure them to a compressive strength ≥10MPa.

[0023] In the above scheme, the lightweight aggregate is any one or more of clay ceramsite, fly ash ceramsite or shale ceramsite, the particle size of the ceramsite is ≥2 mm, and the shape is not limited. The ceramsite on the cross section is colored using a fluorescent resin dye so that it appears as an orange-red bright spot under ultraviolet light with an emission wavelength of 365 nm.

[0024] It can be seen from the above technical solutions that the normalized lightweight aggregate concrete homogeneity characterization method provided by the present disclosure has at least the following beneficial effects:

[0025] 1. The normalized lightweight aggregate concrete homogeneity characterization method provided in the present disclosure takes into account the complete cross-sectional information of the lightweight aggregate concrete specimen by adopting a normalized lightweight aggregate concrete homogeneity calculation method, and obtains a more realistic judgment result by refining and zoning the sliced ​​cross-section. At the same time, it takes into account the influence of the difference in lightweight aggregate dosage on the homogeneity of different lightweight aggregate concretes, realizes the horizontal quantitative comparison of the degree of lightweight aggregate distribution between different lightweight aggregate concretes, and thus can realize the rapid and accurate determination of the degree of aggregate distribution homogeneity in lightweight aggregate concrete.

[0026] 2. The normalized lightweight aggregate concrete homogeneity characterization method provided by the present disclosure takes into account the complete cross-sectional information of the lightweight aggregate concrete specimen and adopts a method of finely partitioning the slice section to avoid human operational errors caused by horizontal cutting of the concrete slices. In addition, the method does not require material characterization. The method is simple to operate and has a wide range of applications. It can quickly and effectively determine the homogeneity of lightweight aggregate distribution in lightweight aggregate concrete.

[0027] 3. The normalized lightweight aggregate concrete homogeneity characterization method provided in the present disclosure can accurately test the homogeneity of lightweight aggregate distribution in lightweight aggregate concrete by adopting a normalized lightweight aggregate concrete homogeneity calculation method. The homogeneity characterized by the normalized homogeneity calculation method is between 0 and 1, realizing a horizontal quantitative comparison of the homogeneity of concrete sections with different lightweight aggregate contents. The method is simple to operate and has a wide range of applications. It can simply, quickly and effectively determine the homogeneity of lightweight aggregate in lightweight aggregate concrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to further illustrate the content of the present disclosure, the present disclosure is described in detail below with reference to the accompanying drawings, wherein:

[0029] FIG1 is a flow chart of a normalized lightweight aggregate concrete homogeneity characterization method provided by the present disclosure.

[0030] FIG2 is a schematic diagram of lightweight aggregate concrete and random distribution of lightweight aggregate according to an embodiment of the present disclosure;

[0031] FIG3 is a schematic diagram of lightweight aggregate concrete specimen types and cutting according to an embodiment of the present disclosure;

[0032] FIG4 is a schematic diagram of a cross-sectional partition of a lightweight aggregate concrete slice according to an embodiment of the present disclosure;

[0033] FIG5 is a cross-sectional view of a slice of lightweight aggregate concrete according to an embodiment of the present disclosure;

[0034] FIG6 is a cross-sectional lightweight aggregate area ratio distribution curve according to an embodiment of the present disclosure;

[0035] FIG7 is a schematic diagram of three distribution states of lightweight aggregate in a cross section of lightweight aggregate concrete according to an embodiment of the present disclosure;

[0036] FIG8 is a graph comparing standard deviation and homogeneity coefficient of lightweight aggregate under three distribution states of a lightweight aggregate concrete slice according to an embodiment of the present disclosure.

[0037] Reference numerals: lightweight aggregate concrete 1; mortar 2; lightweight aggregate 3 DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the present disclosure more clear, the present disclosure is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. In the detailed description below, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is obvious that one or more embodiments can also be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0039] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0040] Furthermore, the shapes and sizes of the components in the figures do not reflect the actual sizes and proportions, but are merely illustrative of the contents of the embodiments of the present disclosure. In addition, in the claims, any reference signs placed between brackets should not be construed as limiting the claims.

[0041] Furthermore, the word "comprise" or "comprising" does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

[0042] In order to solve the problem of limitations of the current concrete homogeneity determination methods based on experiments or digital image processing technology, avoid human operation errors caused by re-cutting sample slices and reduce the authenticity of the determination results due to only taking the upper and lower layers of concrete as research objects, and omit the material characterization step, the present disclosure proposes a normalized lightweight aggregate concrete homogeneity characterization method. By adopting a normalized lightweight aggregate concrete homogeneity calculation method, the complete cross-sectional information of the lightweight aggregate concrete specimen is taken into account, and a more realistic determination result is obtained by refining and zoning the slice section; at the same time, the influence of the difference in lightweight aggregate dosage on the homogeneity of different lightweight aggregate concretes is taken into account, and a horizontal quantitative comparison of the degree of lightweight aggregate distribution between different lightweight aggregate concretes is realized, thereby realizing a rapid and accurate determination of the degree of homogeneity of aggregate distribution in lightweight aggregate concrete.

[0043] As shown in FIG1 , FIG1 is a flow chart of a normalized lightweight aggregate concrete homogeneity characterization method provided by the present disclosure, and the method comprises the following steps:

[0044] Step S1: preparing lightweight aggregate concrete specimens;

[0045] In this step, first determine the grading curve of lightweight aggregate, the maximum particle size d max , average particle size d ave Next, determine the shape and size of the lightweight aggregate concrete specimen used. The shape of the lightweight aggregate concrete specimen is a prism or a cylinder, where the size of the prism is length × width × height = d1 × d1 × h1, and the size of the cylinder is diameter × height = d2 × h2, and d1 ≥ 10 × d max , h1≥10×d max ; d2≥10×d max , h2≥10×d max ; Then, lightweight aggregate concrete specimens were prepared and cured to a compressive strength ≥ 10 MPa.

[0046] Step S2: Cut the lightweight aggregate concrete specimen along the height direction and through the central axis of the height direction to obtain n slice sections a i , where i = 1, ..., n;

[0047] In this step, the lightweight aggregate concrete specimen is cut along the height direction and through the central axis of the height direction to obtain n slice sections a i , the distribution of lightweight aggregate in any slice section is uniform.

[0048] Step S3: For each slice section a i Take pictures and perform image recognition to obtain each slice section a i The total area A and the lightweight aggregate phase area A i, calculate the lightweight aggregate phase area ratio b i =A i / A;

[0049] Step S4: According to the lightweight aggregate phase area ratio b between each slice section in the same lightweight aggregate concrete specimen i The difference of |b i -b j |, determine the homogeneity of the lightweight aggregate concrete, where i = 1, ..., n, j = 1, ..., n;

[0050] In this step, the area ratio b of the lightweight aggregate phase between the sections of the same lightweight aggregate concrete specimen is calculated. i The difference of |b i -b j |, determine the homogeneity of the lightweight aggregate concrete, specifically including: comparing the lightweight aggregate phase area ratio b between each slice section in the same lightweight aggregate concrete specimen i The difference of |b i -b j |, if |b i -b j |>threshold, the lightweight aggregate concrete is judged to be inhomogeneous and the process ends; if |b i -b j |≤threshold, the lightweight aggregate concrete is determined to be homogeneous and the next step is performed.

[0051] Optionally, the threshold is 4% to 6%, for example, the threshold may be 5%.

[0052] Step S5: Calculating and characterizing the homogeneity of the lightweight aggregate distribution in the lightweight aggregate concrete, specifically including:

[0053] Step S51: Calculate each slice section a i Lightweight aggregate distribution uniformity coefficient S i ;

[0054] For each slice section a i Divide the area equally along the height direction, and the single slice section a i The number of partitions is m, and the height of each partition is h1. For the i-th slice section a i , from bottom to top the partitions are marked as a i，j , where i = 1, ..., n; j = 1, ..., m, and each partition a is obtained i，j Lightweight aggregate area A i，j and lightweight aggregate area ratio b i，j , calculate each slice section a i Lightweight aggregate distribution uniformity coefficient S i for:

[0055] in, is the standard deviation of the lightweight aggregate area ratio in the slice section, S NOR，i is the standardized parameter of the standard deviation of the lightweight aggregate area ratio in the slice section, and S NOR，i =1 / 2(b i -b i 2 ), lightweight aggregate distribution uniformity coefficient S i Between 0 and 1, it is possible to achieve horizontal quantitative comparison of aggregate distribution homogeneity in lightweight aggregate concrete with different aggregate contents and types.

[0056] Step S52: According to each slice section a i Lightweight aggregate distribution uniformity coefficient S i , characterizes the uniformity of the distribution of lightweight aggregate in the lightweight aggregate concrete. Specifically, according to each slice section a i Lightweight aggregate distribution uniformity coefficient S i , when the homogeneity coefficient S i The closer it is to 0, the more uniform the distribution of lightweight aggregate in lightweight aggregate concrete is; when the homogeneity coefficient S i The closer it is to 1, the worse the homogeneity of lightweight aggregate concrete.

[0057] In the normalized lightweight aggregate concrete homogeneity characterization method provided in the present disclosure, the lightweight aggregate is any one or more of clay ceramsite, fly ash ceramsite or shale ceramsite, the particle size of the ceramsite is ≥2 mm, and the shape is not limited. The ceramsite of the slice section is colored using a fluorescent resin dye so that it appears as an orange-red bright spot under ultraviolet light with an emission wavelength of 365 nm.

[0058] Therefore, the normalized lightweight aggregate concrete homogeneity characterization method proposed in the present disclosure takes into account the complete cross-sectional information of the lightweight aggregate concrete specimen by adopting a normalized lightweight aggregate concrete homogeneity calculation method, and obtains a more realistic judgment result by refining and zoning the slice section; at the same time, it takes into account the influence of the difference in lightweight aggregate dosage on the homogeneity of different lightweight aggregate concretes, realizes the horizontal quantitative comparison of the degree of lightweight aggregate distribution between different lightweight aggregate concretes, and thus can realize the rapid and accurate determination of the degree of homogeneity of aggregate distribution in lightweight aggregate concrete.

[0059] The normalized lightweight aggregate concrete homogeneity characterization method provided by the present disclosure is shown in Figures 2-4. A lightweight aggregate concrete specimen 1 is cut along the central axis in the height direction. The size of the concrete specimen can be a prism or a cylinder. The number of cut sections is n, and each cut section is marked as a. i , where i = 1, ..., n; take a picture of the slice section, use digital image technology to identify lightweight aggregate 3 and mortar 2, and record each slice section ai The total area A of the “lightweight aggregate phase” is A i and the area AA of “other phases except lightweight aggregate” i , calculate the lightweight aggregate area ratio b i =A i / A; Compare the lightweight aggregate area ratio b between multiple sections of the same specimen i Difference|b i -b j |, if |b i -b j |≤5%, where i=1, ..., n, j=1, ..., n, the lightweight aggregate concrete is determined to be homogeneous; otherwise, the lightweight aggregate concrete is determined to be inhomogeneous, and the determination of the homogeneity of the lightweight aggregate concrete ends.

[0060] Furthermore, after determining that the lightweight aggregate concrete is homogeneous, the method further includes: for each slice section a i Divide the area equally along the height direction, and each slice section a i The number of partitions of a single slice section is m, and the height of each partition is h1. For the i-th section, the partitions from bottom to top are marked as a i，j , where i = 1, ..., n; j = 1, ..., m, calculate each partition a i，j Lightweight aggregate area A i，j and lightweight aggregate area ratio b i，j ; Determine each slice section a i Lightweight aggregate distribution uniformity coefficient S i , The homogeneity represented by the normalized homogeneity calculation formula is between 0 and 1. i The closer it is to 0, the more uniform the distribution of lightweight aggregate in lightweight aggregate concrete is. On the contrary, when the homogeneity coefficient S i The closer it is to 1, the worse the uniformity of lightweight aggregate distribution in lightweight aggregate concrete.

[0061] The normalized lightweight aggregate concrete homogeneity characterization method provided by the present disclosure will be further described in detail below with reference to examples.

[0062] This embodiment combines the previous team's experimental research on the problem of aggregate floating in lightweight aggregate concrete. The test uses fly ash composite ceramsite (particle size 2-6 mm) as the lightweight aggregate, and the concrete specimen is a 150 mm × 150 mm × 150 mm cubic standard specimen. The experiment designed three groups of test mix ratios for comparative analysis, namely, No. 1 composite admixture group (admixed with fiber and mineral thickener), No. 2 single fiber admixture group, and No. 3 blank group (without fiber and mineral thickener). The test mix ratios are shown in Table 1.

[0063] Table 1 Test mix ratio

[0064] Prepare lightweight aggregate concrete according to the mix proportion in Table 1 and cure until the compressive strength is ≥10MP a The lightweight aggregate concrete specimen was cut along the central axis in the height direction to obtain two slice sections. Image-Pro Plus 6.0 was used to process any slice section. In order to accurately identify the ceramsite in the section, the ceramsite in the section was highlighted in red. The three groups of lightweight aggregate concrete slice sections are shown in Figure 5. After image recognition of "lightweight aggregate phase" 3 and "other phases except lightweight aggregate" (ie, mortar 2), the total area A of the three groups of slice sections and the area A of "lightweight aggregate phase" were recorded respectively. i , calculate the lightweight aggregate area ratio b on the entire slice section i , compare the difference in lightweight aggregate area ratio between two sections of the same specimen |b i -b j |, determine whether the lightweight aggregate concrete under the three experimental proportions is uniform, and the calculation results are shown in Table 2.

[0065] Table 2 Calculation results

[0066] From the calculation results in Table 2, we can see that the difference in the distribution area ratio of lightweight aggregate between the two sections of lightweight aggregate concrete under the three experimental proportions |b i -b j | are all less than 5%, so it can be determined that the three groups of lightweight aggregate concrete are uniform. On this basis, the three groups of concrete slices are divided into 30 equal parts at 5mm height along the height direction, and the "lightweight aggregate phase" area A of each part of the three groups of slices is recorded respectively. i，j , calculate the lightweight aggregate area ratio b of each partition i，j The curves of the lightweight aggregate distribution area ratio of each section under the three test mix ratios are shown in Figure 6. The variance, standard deviation and homogeneity coefficient of the lightweight aggregate area ratio of the concrete slice section are further analyzed, and the calculation results are shown in Table 3.

[0067] Table 3 Calculation results

[0068] Figure 6 shows the degree of uniformity of lightweight aggregate distribution: 1 (compounding) > 2 (fiber-only) > > 3 (blank). Further analysis of the standard deviation of the cross-sectional lightweight aggregate area ratio, based on the calculation results in Table 3, also directly determines the uniformity of lightweight aggregate distribution across the cross section. Analysis of the homogeneity coefficient reveals that the composite-mixing group (0.171) > fiber-only (0.221) > blank group (0.274), yielding consistent results. This validates the rationality of the normalized lightweight aggregate uniformity calculation method proposed in this disclosure.

[0069] In order to better illustrate the advantages of the normalized lightweight aggregate concrete homogeneity characterization method provided by the present disclosure, the most uniform and most non-uniform distribution states of lightweight aggregate in the lightweight aggregate concrete of the above three groups of experimental proportions are now supplemented for analysis. The schematic diagrams of the three distribution states of lightweight aggregate in lightweight aggregate concrete under the three groups of experimental proportions are shown in Figure 7, wherein (a) is a schematic diagram of the most uniform distribution state of lightweight aggregate in the cross section, (b), (c) and (d) are schematic diagrams of the actual distribution states of lightweight aggregate in the cross section in the 1-compound, 2-fiber and 3-blank groups, respectively, and (e), (f) and (g) are schematic diagrams of the most non-uniform distribution state of lightweight aggregate in the cross section in the 1-compound, 2-fiber and 3-blank groups, respectively. The standard deviation and uniformity coefficient of lightweight aggregate in the most uniform distribution state and the most non-uniform distribution state of lightweight aggregate in the lightweight aggregate concrete of the above three groups of experimental proportions are further calculated, and the calculation results are obtained as shown in Table 4. The comparison curves of the standard deviation and uniformity coefficient of lightweight aggregate in the three distribution states are drawn as shown in Figure 8.

[0070] Table 4 Calculation results

[0071] As can be seen from the calculation results in Table 4 and the comparison curve in Figure 8, the method of determining the lightweight aggregate area ratio variance and standard deviation of concrete slice sections has certain limitations. When the aggregate content is different, the standard deviation calculated for the most uneven distribution of lightweight aggregate is different. This method cannot be used to compare the homogeneity of lightweight aggregate distribution in lightweight aggregate concrete. The normalized lightweight aggregate concrete homogeneity characterization method provided in this disclosure is based on the standard deviation of the lightweight aggregate area ratio of the slice section. The homogeneity represented by the normalized homogeneity calculation formula is between 0 and 1. The closer the homogeneity coefficient is to 0, the more uniform the aggregate distribution in the lightweight aggregate concrete; conversely, the closer the homogeneity coefficient is to 1, the worse the aggregate distribution homogeneity in the lightweight aggregate concrete. In this example, when the aggregate contents varied across the three experimental mixes, the homogeneity coefficient for each group was 1 under the most uneven aggregate distribution conditions. This demonstrates that the normalized lightweight aggregate concrete homogeneity characterization method provided by the present disclosure can achieve a horizontal comparison of the homogeneity of lightweight aggregate distribution in lightweight aggregate concretes with varying aggregate contents, and that this determination method is more accurate. Therefore, the normalized lightweight aggregate concrete homogeneity characterization method provided by the present disclosure can quickly and accurately determine the homogeneity of lightweight aggregate distribution in lightweight aggregate concrete.

[0072] The embodiments of the present disclosure have been described in detail with reference to the accompanying drawings. It should be noted that any implementations not depicted or described in the drawings or the main text of the specification are known to those skilled in the art and are not described in detail. Furthermore, the above definitions of the various elements and methods are not limited to the various specific structures, shapes, or methods described in the embodiments, and can be easily modified or replaced by those skilled in the art.

[0073] The use of ordinal numbers in the specification and claims, such as "step S1" and "step S2", to modify corresponding elements, does not in itself mean that the elements have any ordinal numbers, nor does it represent the order of one element relative to another, or the order of the manufacturing method. The use of such ordinal numbers is only used to clearly distinguish one element with a certain name from another element with the same name.

[0074] Similarly, it should be understood that in order to streamline the present disclosure and aid in understanding one or more of the various disclosed aspects, in the above description of exemplary embodiments of the present disclosure, various features of the present disclosure are sometimes grouped together into a single embodiment, figure, or description thereof. However, this disclosed approach should not be interpreted as reflecting an intention that the claimed disclosure requires more features than are expressly recited in each claim. Rather, as reflected in the claims below, the disclosed aspects consist of fewer than all the features of the individual embodiments disclosed above. Accordingly, the claims that follow the detailed description are hereby expressly incorporated into the detailed description, with each claim standing on its own as a separate embodiment of the present disclosure.

[0075] It has been verified that the specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present disclosure in detail. It should be understood that the above description is only a specific embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the scope of protection of the present disclosure.

Claims

1. A normalized lightweight aggregate concrete homogeneity characterization method, the method comprising: Preparation of lightweight aggregate concrete specimens; The lightweight aggregate concrete specimen is cut along the height direction and through the central axis in the height direction to obtain n slice sections a i , where i = 1, ..., n; For each slice section a i Take pictures and perform image recognition to obtain each slice section a i The total area A and lightweight aggregate area A i , calculate the lightweight aggregate phase area ratio b i =A i / A; According to the lightweight aggregate phase area ratio b between the sections of the same lightweight aggregate concrete specimen i The difference b i -b j |, determine the homogeneity of the lightweight aggregate concrete, where i = 1, ..., n, j = 1, ..., n.

2. The normalized lightweight aggregate concrete homogeneity characterization method according to claim 1, wherein the lightweight aggregate concrete specimen is cut along the height direction and through the central axis of the height direction to obtain n slice sections a i In the steps, the distribution of lightweight aggregate in any slicing section is uniform.

3. The normalized lightweight aggregate concrete homogeneity characterization method according to claim 1, wherein the lightweight aggregate phase area ratio b between each slice section in the same lightweight aggregate concrete specimen is i The difference of |b i -b j |, determine the homogeneity of the lightweight aggregate concrete, including: Compare the lightweight aggregate phase area ratio b between the slice sections in the same lightweight aggregate concrete specimen i The difference of |b i -b j |, if |b i -b j |>threshold, the lightweight aggregate concrete is judged to be inhomogeneous; if |b i -b j |≤threshold, the lightweight aggregate concrete is judged to be homogeneous.

4. The normalized lightweight aggregate concrete homogeneity characterization method according to claim 3, wherein the threshold value is 4% to 6%.

5. The normalized lightweight aggregate concrete homogeneity characterization method according to claim 3, after determining that the lightweight aggregate concrete is homogeneous, further comprising: Calculate and characterize the homogeneity of lightweight aggregate distribution in the lightweight aggregate concrete.

6. According to the normalized lightweight aggregate concrete homogeneity characterization method of claim 5, the calculating and characterizing the homogeneity of lightweight aggregate distribution in the lightweight aggregate concrete comprises: Calculate each slice section a i Lightweight aggregate distribution uniformity coefficient S i ; According to each slice section a i Lightweight aggregate distribution uniformity coefficient S i , characterizing the lightweight aggregate mix Homogeneity of lightweight aggregate distribution in concrete.

7. The normalized lightweight aggregate concrete homogeneity characterization method according to claim 6, wherein the calculation of each slice section a i Lightweight aggregate distribution uniformity coefficient S i ,include: For each slice section a i Divide equally along the height direction, a single slice section a i The number of partitions is m, and the height of each partition is h1. For the i-th slice section a i , from bottom to top, the partitions are marked as a i，j , where i = 1, ..., n; j = 1, ..., m, and each partition a is obtained i，j Lightweight aggregate area A i，j and lightweight aggregate area ratio b i，j , calculate each slice section a i Lightweight aggregate distribution uniformity coefficient S i for: in, is the standard deviation of the lightweight aggregate area ratio in the slice section, S NOR，i is the standardized parameter of the standard deviation of the lightweight aggregate area ratio in the slice section, and S NOR，i =-1 / 2(b i -b i 2 ), lightweight aggregate distribution uniformity coefficient S i Between 0 and 1, it is possible to achieve a horizontal quantitative comparison of the aggregate distribution homogeneity in lightweight aggregate concrete with different aggregate contents and types.

8. The normalized lightweight aggregate concrete homogeneity characterization method according to claim 7, wherein the i Lightweight aggregate distribution uniformity coefficient S i , characterizes the homogeneity of lightweight aggregate distribution in the lightweight aggregate concrete, including: According to each slice section a i Lightweight aggregate distribution uniformity coefficient S i , when the homogeneity coefficient S i The closer it is to 0, the more uniform the distribution of lightweight aggregate in lightweight aggregate concrete is; when the homogeneity coefficient S i The closer it is to 1, the worse the homogeneity of lightweight aggregate concrete.

9. The normalized lightweight aggregate concrete homogeneity characterization method according to claim 1, wherein the step of preparing a lightweight aggregate concrete specimen comprises: Determine the grading curve of lightweight aggregate and the maximum particle size d max , average particle size d ave ; Determine the shape and size of the lightweight aggregate concrete specimen used. The shape of the lightweight aggregate concrete specimen is a prism or a cylinder, where the size of the prism is length × width × height = d1 × d1 × h1, and the size of the cylinder is diameter × height = d2 × h2, and d1 ≥ 10 × d max , h1≥10×d max ; d2≥10×d max , h2≥10×d max ; Prepare lightweight aggregate concrete specimens and cure them to a compressive strength ≥ 10MPa.

10. The normalized lightweight aggregate concrete homogeneity characterization method according to claim 1, wherein the lightweight aggregate is any one or more of clay ceramsite, fly ash ceramsite or shale ceramsite, the particle size of the ceramsite is ≥2 mm, and the shape is not limited, and the ceramsite of the slice section is colored with a fluorescent resin dye so that it appears as an orange-red bright spot under ultraviolet light with an emission wavelength of 365 nm.

Images