A concrete mechanical properties testing method based on sand ratio adjustment

Abstract

The present invention relates to the field of concrete material performance testing, and in particular to a concrete mechanical property testing method based on sand ratio adjustment. The method includes: generating a sand ratio path based on the sand ratio at different times; constructing a concrete uniformity index model to obtain a concrete uniformity index; constructing a joint function model based on the sand ratio and the uniformity index to obtain compressive strength and elastic modulus; designing and minimizing a comprehensive objective function to obtain the optimal sand ratio at different times, thereby generating an optimal sand ratio path; using the optimal sand ratio to prepare concrete samples, and conducting actual tests of mechanical properties to obtain actual test data; based on the actual test data, determining whether the optimal sand ratio needs to be adjusted. The method solves the problems that the prior art does not consider the impact of the dynamic adjustment of the sand ratio on the concrete performance; fails to establish the association between the uniformity index and the sand ratio adjustment and material performance; and fails to fully consider the complex nonlinear coupling relationship between the sand ratio and the uniformity index.

Description

Technical Field

[0001] The invention relates to the field of concrete material performance testing, and in particular to a concrete mechanical property testing method based on sand ratio adjustment. Background Art

[0002] As the core material in modern engineering construction, the mechanical properties of concrete directly affect the safety, durability and overall quality of buildings. Key indicators of mechanical properties, including compressive strength and elastic modulus, are not only affected by the material ratio, but also closely related to the dynamic changes of sand ratio during construction. In practical applications, concrete sand ratio (the proportion of fine aggregate in total aggregate) is an important parameter affecting the uniformity and mechanical properties of concrete materials. Reasonable sand ratio design can improve the working performance and mechanical properties of concrete, while deviation or fluctuation of sand ratio may lead to local density differences of concrete, unstable performance, and even affect the long-term service life of the structure. Therefore, scientifically testing and evaluating the impact of sand ratio on the mechanical properties of concrete is of great significance for optimizing concrete mix design and improving engineering quality.

[0003] However, in modern construction projects, the construction and use environment of concrete is becoming increasingly complex, and the adjustment and control of sand ratio are affected by multiple factors, such as fluctuations in raw materials, changes in construction technology, and limitations of site conditions. This dynamic and complex nature makes it difficult for traditional performance testing methods based on static sand ratio settings to fully reflect the behavioral characteristics of concrete materials under actual engineering conditions. In addition, with the increasing requirements for concrete performance in engineering construction, it is necessary not only to pay attention to mechanical properties such as compressive strength and elastic modulus, but also to achieve a balance between multiple performance indicators such as uniformity, workability, and durability, thereby improving the comprehensiveness and applicability of the testing technology. Therefore, establishing a method that combines dynamic sand ratio adjustment with mechanical performance testing is of great significance for both scientific research and engineering practice. Summary of the invention

[0004] The invention provides a concrete mechanical property testing method based on sand ratio adjustment, so as to solve the problems that the prior art does not consider the influence of dynamic adjustment of sand ratio on concrete performance, cannot reflect the potential influence of sand ratio fluctuation on material performance during construction, resulting in insufficient reliability of test results and applicability of actual engineering applications; fails to establish the correlation between uniformity index and sand ratio adjustment and material performance, and cannot comprehensively quantify the dynamic influence of sand ratio adjustment on material distribution and performance; and fails to fully consider the complex nonlinear coupling relationship between sand ratio and uniformity index, resulting in the inability to meet the multi-dimensional performance requirements in complex engineering application scenarios.

[0005] A concrete mechanical property testing method based on sand ratio adjustment comprises the following steps:

[0006] S1. Real-time collection of data on concrete material density, sand ratio change, mixing state and mechanical properties, and generation of sand ratio paths based on the calculated sand ratios at different times; construction of a concrete uniformity index model, quantification of the impact of the sand ratio path on the distribution of concrete materials, and the acquisition of a concrete uniformity index;

[0007] S2. Construct a joint function model based on sand ratio and uniformity index to obtain compressive strength and elastic modulus; design a comprehensive objective function, and obtain the optimal sand ratio at different times by minimizing the comprehensive objective function, thereby generating an optimal sand ratio path; use the optimal sand ratio to prepare concrete samples, and conduct actual tests on mechanical properties to obtain actual test data; based on the actual test data, determine whether the optimal sand ratio needs to be adjusted; when the optimal sand ratio needs to be adjusted, simultaneously observe the changes in uniformity index and mechanical properties, and verify the sensitivity of sand ratio adjustment to concrete performance.

[0008] Preferably, the S1 specifically includes:

[0009] The specific formula of sand rate is as follows:

[0010] ,

[0011] in, It's time The sand rate at that time; is the initial sand ratio; is the exponential decay coefficient describing the sand rate decay trend; and It is the adjustment coefficient that describes the dynamic fluctuation amplitude of sand rate, and controls the amplitude of cosine term and sine term respectively; and is a periodic parameter used to control the oscillation frequency of sand rate adjustment; is a time variable.

[0012] Preferably, the S1 specifically includes:

[0013] Divide the space into regions and monitor the density of each region; construct a concrete uniformity index model based on the deviation of each region's density data from the overall average density, the density discreteness within each region, and the correlation coefficient of mixing times;

[0014] The mathematical expression of the concrete uniformity index model is as follows:

[0015] ,

[0016] in, The sand rate is Concrete uniformity index at 10 ... It is Density of the area; Indicates the total number of regions; is the average density of all regions; It is The standard deviation of the regional density is used to quantify the discreteness of the density distribution; is the correlation coefficient of stirring times.

[0017] Preferably, the S2 specifically includes:

[0018] By defining the compressive strength and elastic modulus as the joint functions of sand ratio and uniformity index, the comprehensive influence of sand ratio and uniformity index on the mechanical properties is quantified.

[0019] Preferably, the S2 specifically includes:

[0020] The comprehensive objective function formula is as follows:

[0021] ,

[0022] in, is the comprehensive objective function; , , are the target weight coefficients, which are used to balance the optimization priorities of uniformity index, compressive strength and elastic modulus respectively; and are the target compressive strength and target elastic modulus; is the compressive strength; is the elastic modulus.

[0023] Preferably, the S2 specifically includes:

[0024] The comprehensive objective function is minimized through comprehensive analysis of sand ratio, uniformity index, compressive strength and elastic modulus.

[0025] Preferably, the S2 specifically includes:

[0026] The sand ratio is updated by the gradient descent method until the comprehensive objective function converges to obtain the optimal sand ratio, which is taken as the final solution of the comprehensive objective function.

[0027] Preferably, the S2 specifically includes:

[0028] Use the optimal sand ratio to prepare concrete samples, and actually test the compressive strength and elastic modulus to obtain actual test data; compare the actual test data with the calculated compressive strength and elastic modulus. When there are deviations between the compressive strength and elastic modulus and the actual test data, adjustments are made based on the optimal sand ratio. At the same time, changes in uniformity indicators and mechanical properties are observed to verify the sensitivity of sand ratio adjustment to concrete performance.

[0029] The beneficial effects of the technical solution of the present invention are:

[0030] 1. By generating a sand ratio path, it can accurately describe the nonlinear change and random disturbance characteristics of the sand ratio over time, dynamically capture the process of concrete material mixing and uniformity changes, overcome the limitations of sand ratio as a static parameter in traditional tests, and make the sand ratio adjustment more in line with the complex conditions in actual concrete construction; the sand ratio path reflects the nonlinear trend in the time dimension, and by introducing periodic disturbances and exponential attenuation factors, it comprehensively characterizes the actual mixing and molding process of concrete.

[0031] 2. The uniformity index model proposed in the present invention comprehensively considers the density deviation of different spatial regions, the density discreteness within the region and the dynamic influence of the mixing times, and can comprehensively evaluate the uniformity level of concrete during the dynamic sand ratio adjustment process; through the sensor, the density change is monitored in real time, and the regional density average, standard deviation and mixing times correlation coefficient are dynamically calculated. The uniformity index can accurately quantify the comprehensive influence of the sand ratio adjustment on the local and overall uniformity of concrete, improve the monitoring ability of the concrete material quality, and provide a reliable material basis for subsequent mechanical properties testing.

[0032] 3. As key indicators of mechanical properties, compressive strength and elastic modulus are defined as joint functions of sand ratio and uniformity in the present invention. The joint function model constructs a complex coupling relationship between the square term of sand ratio, linear term and uniformity index adjustment term by fitting the experimental data, which can accurately reflect the multiple effects of sand ratio and uniformity index on mechanical properties. This nonlinear modeling method breaks through the limitations of traditional linear assumptions, can more comprehensively reveal the essential change law of concrete performance, and is applicable to a variety of concrete materials and engineering conditions.

[0033] 4. The comprehensive objective function unifies the optimization requirements of sand ratio, uniformity index, compressive strength and elastic modulus into one framework, and realizes flexible allocation of priorities through weight adjustment. The comprehensive objective function is solved by the gradient descent method to dynamically guide the update of the sand ratio; through this solution process, the optimal sand ratio that meets the multi-dimensional performance requirements can be accurately found, so that the concrete material can achieve a balance in uniformity and mechanical properties, and improve the applicability and reliability of the test method. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The present invention is a flow chart of a concrete mechanical properties testing method based on sand ratio adjustment. DETAILED DESCRIPTION

[0035] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0037] The specific scheme of a concrete mechanical property testing method based on sand ratio adjustment provided by the present invention is described in detail below with reference to the accompanying drawings.

[0038] See attached Figure 1 , which shows a flow chart of a concrete mechanical property testing method based on sand ratio adjustment provided by an embodiment of the present invention, the method comprising the following steps:

[0039] S1. Real-time collection of data on concrete material density, sand ratio change, mixing state and mechanical properties, and generation of sand ratio paths based on the calculated sand ratios at different times; construction of a concrete uniformity index model, quantification of the impact of the sand ratio path on the distribution of concrete materials, and the acquisition of a concrete uniformity index;

[0040] The density, sand ratio change, mixing state and mechanical properties of concrete materials are monitored and recorded in real time. The density data of concrete materials are measured in real time by multi-point sensors distributed inside the mixing device. The density data corresponding to each measuring point is collected by the sensor, and the regional average density and density standard deviation are calculated. During the sand ratio adjustment process, the actual change value of the sand ratio is dynamically collected through the electronic scale and sensor system. The sand ratio is the proportion of fine aggregate in the total aggregate. For the mixing state, the correlation coefficient of the number of mixing times is recorded in real time through the built-in counting device of the mixing equipment to ensure the accuracy of the uniformity assessment. In addition, during the mechanical properties testing stage, the compressive strength and elastic modulus of the concrete samples under different loading conditions are recorded in real time through dedicated testing equipment, and the collected compressive strength and elastic modulus are used as the basic input for performance modeling throughout the entire testing process.

[0041] Specifically, in order to comprehensively evaluate the impact of sand ratio adjustment on the mechanical properties of concrete, a multi-period and multi-spatial area collection strategy is adopted, including the following two aspects:

[0042] (1) Multi-period collection

[0043] During the sand ratio adjustment process, the sand ratio data is collected dynamically in real time to capture the impact of sand ratio changes on the mechanical properties of concrete. During the mixing and molding stages, multi-period data is collected through the following mechanisms:

[0044] Collection of sand ratio: The change of sand ratio is recorded in real time through the electronic scale and sensor system, and a sand ratio value is collected at a fixed time interval (for example, 1 second).

[0045] Density collection: During the mixing process, the multi-point sensor collects density data at fixed intervals and records the density change curve over time.

[0046] Stirring times or stirring time: The cumulative number of stirring actions is recorded by the counter of the stirring equipment, that is, the stirring times correlation coefficient.

[0047] Multi-period data collection ensures that the dynamic changes of concrete materials are captured in real time during the entire process of sand ratio adjustment, providing input for the subsequent calculation of concrete uniformity indicators.

[0048] (2) Multi-area collection

[0049] In order to more accurately capture the effect of sand ratio adjustment on the mechanical properties of concrete, the concrete sample or mixing chamber is evenly divided into Each zone is monitored by a separate sensor:

[0050] Density data: Density data is collected by sensors at multiple measuring points in each area to calculate the average density and standard deviation of each area.

[0051] Regional distribution difference: By comparing the density deviation in different areas, the overall uniformity of concrete materials during the sand ratio adjustment process is evaluated.

[0052] Combining multi-period and multi-regional acquisition can provide comprehensive spatiotemporal data support, ensuring that the impact of sand ratio adjustment on concrete uniformity indicators and concrete mechanical properties can be fully quantified.

[0053] Through the sand ratio adjustment process, a dynamic time series path of the sand ratio is generated, namely the sand ratio path; the sand ratio path can show both a nonlinear adjustment trend and the characteristics of random disturbances during the mixing process of concrete materials. The sand ratios at different times constitute a sand ratio path that changes with time. The specific formula of the sand ratio is as follows:

[0054] ,

[0055] in, It's time The sand ratio at that time indicates the proportion of fine aggregate in the total aggregate, expressed in percentage; is the initial sand ratio, which is usually set between 20% and 60%, and the value is determined by the experimental requirements of concrete mix ratio; It is the exponential attenuation coefficient that describes the overall attenuation trend of the sand ratio. Its value is obtained by experimentally fitting the long-term effect of the change in sand ratio on the performance of concrete materials. and It is the adjustment coefficient that describes the dynamic fluctuation amplitude of the sand rate, which controls the amplitude of the cosine term and the sine term during the dynamic adjustment of the sand rate, respectively, and is determined by experiments; and It is a periodic parameter used to control the oscillation frequency of the sand ratio adjustment and is determined by fitting the concrete mixing cycle experiment; It is a time variable, which indicates the time parameter within the integral range. The introduction of the integral term ensures the nonlinearity and dynamics of the sand rate adjustment and can reflect the cumulative effect of time.

[0056] In order to evaluate the impact of sand ratio adjustment on concrete uniformity, it is necessary to clarify the density distribution of different spatial regions of concrete materials during the mixing and molding process. The spatial region refers to a local spatial unit in a concrete sample that is divided into several small volumes. The spatial region can be a specific location detected by a sensor or sampling device, such as a partition in a mold, different levels inside a mixing barrel, or a specific measurement point. By dividing the spatial region, the local density differences that may occur in concrete materials during the dynamic sand ratio adjustment process can be captured more accurately. Local density differences are an important basis for evaluating concrete uniformity.

[0057] In order to specify the division of the spatial region, the sample or stirring chamber is evenly divided into There are three regions, each of which is monitored by a sensor. The density data changes over time and is affected by the sand ratio path. In order to quantify the dynamic impact of sand ratio adjustment on concrete uniformity, a reasonable uniformity index model can be established. The construction of the uniformity index model requires comprehensive consideration of the following factors: (1) The deviation of the density data of each region from the overall average density to reflect the discreteness of the overall concrete material distribution; (2) The density discreteness within each region, that is, the local uniformity, is represented by the standard deviation of the density of each region; (3) Since the stirring action will have a direct impact on the concrete density during the sand ratio adjustment process, it is necessary to consider the dynamic impact of the number of stirring times or stirring time on the uniformity of concrete.

[0058] The mathematical expression of the uniformity index model is as follows:

[0059] ,

[0060] in, The sand rate is Concrete uniformity index at 10 ... It is The density of the area changes dynamically as the sand rate path changes; is the average density of all regions, and its calculation formula is ; It is The standard deviation of regional density is used to quantify the discreteness of density distribution. The formula is: , is the number of measurement points in the spatial region, It is Region No. The density of the measurement points changes dynamically with the change of the sand rate path. It is Average density of the area; It is the correlation coefficient of mixing times, which reflects the dynamic influence of mixing process on uniformity. The larger its value, the greater the contribution of mixing to uniformity. Through the uniformity index model, the dynamic influence of sand ratio path on the distribution of concrete materials in each region can be accurately quantified and integrated into the concrete uniformity index.

[0061] S2. Construct a joint function model based on sand ratio and uniformity index to obtain compressive strength and elastic modulus; design a comprehensive objective function, and obtain the optimal sand ratio at different times by minimizing the comprehensive objective function, thereby generating an optimal sand ratio path; use the optimal sand ratio to prepare concrete samples, and conduct actual tests on mechanical properties to obtain actual test data; based on the actual test data, determine whether the optimal sand ratio needs to be adjusted;

[0062] In order to further accurately describe the complex relationship between the compressive strength and elastic modulus in the mechanical properties of concrete and the combined influence of sand ratio and uniformity index, it is necessary to construct a joint function model based on sand ratio and uniformity index to reflect the direct nonlinear influence of sand ratio change on mechanical properties and the regulatory effect of uniformity index on mechanical properties as an indirect factor; the two key indicators of compressive strength and elastic modulus have significant coupling characteristics. In order to comprehensively quantify the comprehensive influence of sand ratio and uniformity index on mechanical properties, compressive strength and elastic modulus are defined as the joint function of sand ratio and uniformity index. The specific calculation formula of compressive strength is:

[0063] ,

[0064] in, is the compressive strength; , , , is the fitting coefficient, which is determined by fitting the experimental data to the curve of compressive strength changing with sand ratio and uniformity, and is optimized using the least squares method; parameter It reflects the overall contribution of sand ratio to compressive strength; and Control the weights of the square term and linear term of sand ratio; Describes the factors that influence the performance saturation when the sand ratio is too high; and The inhibitory effect of uniformity on compressive strength is reflected by the exponential decay term, which is obtained by fitting the decreasing trend of compressive strength when uniformity is poor in the experimental data.

[0065] Similarly, the calculation formula of the elastic modulus combines the influence of sand ratio and uniformity index and is expressed as:

[0066] ,

[0067] in, is the elastic modulus; , , , It is an experimental fitting parameter used to describe the complex nonlinear effect of sand ratio and uniformity index on elastic modulus. It is determined by fitting the nonlinear relationship curve of elastic modulus with sand ratio and uniformity index through experimental data. , Control the attenuation effect of sand ratio on elastic modulus; , The coupling effect of uniformity index on elastic modulus is introduced through logarithmic terms.

[0068] In order to achieve multi-objective coordinated optimization of sand ratio adjustment, concrete uniformity and concrete mechanical properties, a comprehensive objective function is designed to balance the different weights of concrete performance requirements by combining the complex coupling relationship between different test parameters. The test parameters refer to sand ratio, uniformity index, compressive strength and elastic modulus. The construction of the comprehensive objective function aims to minimize the comprehensive objective function through a comprehensive analysis of sand ratio, uniformity index, compressive strength and elastic modulus, and obtain the optimal sand ratio at different times, thereby generating a time series path of the optimal sand ratio, that is, the optimal sand ratio path, to meet the requirements of multi-dimensional performance indicators and achieve a balance between testing and application requirements. The formula of the comprehensive objective function is as follows:

[0069] ,

[0070] in, is the comprehensive objective function; , , are the target weight coefficients, which are used to balance the optimization priorities of uniformity index, compressive strength and elastic modulus respectively; and are the target compressive strength and target elastic modulus, which are specified by actual engineering requirements. In order to solve the optimal sand ratio, the comprehensive objective function updates the sand ratio by the gradient descent method, and the update rule of the sand ratio is:

[0071] ,

[0072] in, It's time The sand rate at that time is the updated sand rate; is the gradient descent learning rate, which is used to control the optimization step size and is determined by the convergence experiment analysis of the gradient descent method; It is the gradient of the comprehensive objective function to the sand ratio, reflecting the direction and magnitude of the impact of the sand ratio on the optimization target in each update. The specific expression of the gradient term is:

[0073] ,

[0074] Through the above calculation, the gradient term Can be solved step by step to guide the sand ratio The optimization process continues until the comprehensive objective function Convergence, i.e. the gradient term The absolute value of is less than the threshold preset according to the expert experience method. At this point, the iteration ends and the optimal sand ratio is obtained as the final solution that meets the comprehensive target performance.

[0075] Use the optimal sand ratio Prepare concrete samples and conduct actual tests on compressive strength, elastic modulus and other mechanical properties to obtain actual test data. Compare the actual test data with the calculated concrete mechanical properties. If there is a deviation between the concrete mechanical properties and the actual test data, make a small adjustment (for example, ±5%) based on the optimal sand ratio to obtain the adjusted sand ratio. At the same time, observe the changes in uniformity indicators and mechanical properties to verify the sensitivity of sand ratio adjustment to concrete performance. Repeat the above steps under different mix ratios, aggregate gradations and environmental conditions to verify the applicability of the optimal sand ratio in different application scenarios.

[0076] Specifically, the verification steps of the sensitivity of sand ratio adjustment to concrete performance are as follows:

[0077] (1) Comparison of theoretically calculated concrete mechanical properties with actual test data

[0078] To obtain the optimal sand ratio Afterwards, concrete samples were prepared and subjected to practical tests, including compressive strength and elastic modulus Compare the actual test data with the calculated concrete mechanical properties:

[0079] If the actual test data are consistent with the calculated concrete mechanical properties, it means that the sensitivity of sand ratio adjustment to concrete performance is accurately described.

[0080] If there is a deviation between the actual test data and the calculated concrete mechanical properties, the concrete uniformity index model or the joint function model is corrected by analyzing the source of the deviation.

[0081] (2) Sensitivity analysis of small-scale sand ratio adjustment

[0082] Optimum sand ratio Make small adjustments (e.g. ), and observe the changing trend of concrete mechanical properties;

[0083] Preparation of different sand ratios (such as , ) concrete samples and measured the corresponding compressive strength and elastic modulus respectively.

[0084] Analyze the slope of the curve of concrete mechanical properties changing with sand ratio to determine the sensitivity of sand ratio to concrete mechanical properties. If the change of concrete mechanical properties with sand ratio is large, it means that the sensitivity is high; if the change is small, the sensitivity is low.

[0085] The mathematical description of sensitivity analysis is as follows:

[0086] Sensitivity of compressive strength:

[0087] ,

[0088] in, is the sensitivity of compressive strength; is the adjustment range of sand ratio; is Compressive strength at sand ratio; is Compressive strength at sand ratio;

[0089] Sensitivity of elastic modulus:

[0090] ,

[0091] in, is the sensitivity of the elastic modulus; is Elastic modulus at sand rate; is Elastic modulus at sand rate.

[0092] Through sensitivity analysis, the influence of sand ratio adjustment on the mechanical properties of concrete can be clarified, providing verification for the reliability of sand ratio adjustment.

[0093] (3) Multi-scenario verification

[0094] The effect of the optimal sand ratio was repeatedly tested under different mix ratios, aggregate gradations and environmental conditions to verify its applicability. The test method is as follows:

[0095] Mix ratio verification: Test the effect of sand ratio adjustment on the mechanical properties of concrete under adjusted water-cement ratio or other mix ratio conditions.

[0096] Aggregate gradation verification: Change the aggregate particle size distribution and analyze whether the optimal sand ratio can still maintain the mechanical properties of concrete.

[0097] Environmental verification: Repeat the test under different temperature and humidity conditions to verify the adaptability of the final optimal sand ratio to the actual application scenario.

[0098] The adjusted sand rate is the optimal sand rate Based on the improved value obtained after sensitivity analysis and experimental verification, the actual compressive strength at each adjustment point is obtained by testing. and elastic modulus , and the corresponding uniformity index .

[0099] Record the performance deviations of compressive strength and elastic modulus at each adjustment point, for example:

[0100] ,

[0101] ,

[0102] in, and The time Performance deviation of compressive strength and elastic modulus at different times; and They are the target compressive strength and target elastic modulus. At the same time, the uniformity index is recorded. changes.

[0103] By analyzing the performance data of compressive strength and elastic modulus at multiple adjustment points, the sand ratio that meets the following conditions is selected :

[0104] Uniformity target met: Adjusted sand ratio Corresponding uniformity index Satisfy design requirements (e.g., meet or exceed thresholds set based on expert experience).

[0105] Minimum performance deviation of compressive strength and elastic modulus: Performance deviation of compressive strength and elastic modulus after sand ratio adjustment and Reach the minimum value and be within the design allowable range (for example, not exceeding ±5% of the target compressive strength and target elastic modulus, respectively).

[0106] Sensitivity tends to be stable: the slope of the concrete mechanical properties change curve around the adjustment point tends to be stable (that is, the sensitivity of sand ratio adjustment to concrete mechanical properties decreases), indicating that the sand ratio has approached the local optimal solution of concrete mechanical properties.

[0107] The final sand ratio is determined by the following optimized conditions :

[0108] ,

[0109] Among them, the weight , , The experimental requirements are set to balance the importance of uniformity index and mechanical properties of concrete.

[0110] In order to determine the adjusted sand rate Whether it can be used as the final available value requires the following verification steps:

[0111] (1) Repeated verification of multiple experiments

[0112] exist Under the same conditions, multiple groups of concrete samples were prepared and their compressive strength, elastic modulus and uniformity index were tested respectively. Multiple repeated experiments were performed to ensure that the mechanical properties of concrete statistically met the target values ​​and the results were sufficiently stable and consistent.

[0113] (2) Multi-condition verification

[0114] Repeat the test under different material ratios and aggregate gradations , ensuring that its applicability is not significantly restricted by the formula; for example: the deviation between the compressive strength corresponding to the adjusted sand ratio and the target compressive strength does not exceed 5%, the deviation between the elastic modulus corresponding to the adjusted sand ratio and the target elastic modulus does not exceed 5%, the uniformity index corresponding to the adjusted sand ratio shall not be lower than the set threshold (such as the minimum uniformity index design requirement defined before the experiment), and the fluctuation under different working conditions shall not exceed 10%; it can be determined that the applicability is not significantly restricted.

[0115] If the adjusted sand ratio can still maintain excellent performance under multiple working conditions, it can be determined as the final usable value; for example: the ratio of compressive strength to target compressive strength, and the ratio of elastic modulus to target elastic modulus (achievement rate) are more than 95% respectively, and the uniformity index not only meets the minimum uniformity index design requirements, but also reaches or exceeds 95% of the uniformity index value under the best working conditions, and at the same time satisfies the standard deviation of the concrete mechanical properties deviation not exceeding the self-set threshold, etc.; then the adjusted sand ratio is determined to be the final usable value, that is, the final optimal sand ratio.

[0116] In summary, a concrete mechanical properties testing method based on sand ratio adjustment was completed.

[0117] The order of the embodiments of the invention is for description only and does not represent the advantages and disadvantages of the embodiments. The processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

Claims

1. A concrete mechanical properties testing method based on sand ratio adjustment, characterized in that: The following steps are involved: S1. Collect data on concrete material density, sand ratio change, mixing state and mechanical properties in real time, and calculate the sand ratio at different times. The specific calculation formula of the sand ratio is as follows: ， in, It's time The sand rate at that time; is the initial sand ratio; is the exponential decay coefficient describing the sand rate decay trend; and It is the adjustment coefficient that describes the dynamic fluctuation amplitude of sand rate, and controls the amplitude of cosine term and sine term respectively; and is a periodic parameter used to control the oscillation frequency of sand rate adjustment; is a time variable; Based on the sand ratio at different times, a sand ratio path is generated; the spatial regions are divided and the density of each region is monitored; based on the deviation of the density data of each region from the overall average density, the density discreteness within each region and the correlation coefficient of the mixing times, a concrete uniformity index model is constructed to quantify the influence of the sand ratio path on the distribution of concrete materials and obtain the concrete uniformity index; the mathematical expression of the concrete uniformity index model is as follows: ， in, The sand rate is Concrete uniformity index at ; It is Density of the area; Indicates the total number of regions; is the average density of all regions; It is The standard deviation of the regional density is used to quantify the discreteness of the density distribution; is the correlation coefficient of stirring times; S2. By defining compressive strength and elastic modulus as a joint function of sand ratio and uniformity index, the comprehensive influence of sand ratio and uniformity index on mechanical properties is quantified; the specific calculation formula of compressive strength is: ， in, is the compressive strength; , , , are the fitting coefficients; and The exponential decay term reflects the inhibitory effect of uniformity on compressive strength; The calculation formula of elastic modulus is expressed as: ， in, is the elastic modulus; , , , are experimental fitting parameters; Design a comprehensive objective function, and by minimizing the comprehensive objective function, obtain the optimal sand rate at different times, thereby generating the optimal sand rate path; the specific formula of the comprehensive objective function is: ， in, is the comprehensive objective function; , , are the target weight coefficients, which are used to balance the optimization priorities of uniformity index, compressive strength and elastic modulus respectively; and are the target compressive strength and target elastic modulus; Use the optimal sand ratio to prepare concrete samples, and conduct actual tests on mechanical properties to obtain actual test data; based on the actual test data, determine whether the optimal sand ratio needs to be adjusted; when the optimal sand ratio needs to be adjusted, observe changes in uniformity indicators and mechanical properties at the same time, and verify the sensitivity of sand ratio adjustment to concrete performance.

2. The concrete mechanical properties testing method based on sand ratio adjustment according to claim 1 is characterized in that: The S2 specifically includes: The comprehensive objective function is minimized through comprehensive analysis of sand ratio, uniformity index, compressive strength and elastic modulus.

3. The concrete mechanical properties testing method based on sand ratio adjustment according to claim 2 is characterized in that: The S2 specifically includes: The sand ratio is updated by the gradient descent method until the comprehensive objective function converges to obtain the optimal sand ratio, which is taken as the final solution of the comprehensive objective function.

4. The concrete mechanical properties testing method based on sand ratio adjustment according to claim 3 is characterized in that: The S2 specifically includes: Use the optimal sand ratio to prepare concrete samples, and actually test the compressive strength and elastic modulus to obtain actual test data; compare the actual test data with the calculated compressive strength and elastic modulus. When there are deviations between the compressive strength and elastic modulus and the actual test data, adjustments are made based on the optimal sand ratio. At the same time, changes in uniformity indicators and mechanical properties are observed to verify the sensitivity of sand ratio adjustment to concrete performance.

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