A research method for determining the measuring points of concrete rebound test hammer segment rate

Abstract

The invention discloses a research method for measuring points of segmented calibration of a concrete rebound test hammer. By exploring the relationship between the calibration value of a medium-sized concrete rebound test hammer on a light steel needle and the hardness and weight of a steel anvil within a calibration period, it is obtained that when the Rockwell hardness of the steel anvil is 60±2 and the weight is 1.03kg, the calibration value of the concrete rebound test hammer is 40±1, the calibration value of the rebound test hammer is reduced, and the stability and use accuracy of the rebound rate of the rebound test hammer in a commonly used concrete strength range are improved. At the same time, an optimization processing method for evaluating the calibration results is designed, the calibration accuracy is improved, the gap in this field at home and abroad is filled, and the use accuracy of the rebound test hammer in a commonly used concrete strength range is improved.

Description

Technical Field

[0001] The invention relates to the technical field of construction equipment detection, and in particular to a research method for determining measuring points of a concrete rebound test hammer segment rate. Background Art

[0002] The rebound test hammer is an instrument used to test the compressive strength of concrete, mortar and bricks. Its principle is to obtain the rebound value by hitting the surface of the object being tested, and use the rebound value as a parameter related to the compressive strength of the object being tested to infer the compressive strength of the object being tested. As the simplest and most convenient non-destructive testing method, the rebound method for testing the compressive strength of concrete has become the most widely used on-site testing method for concrete entities.

[0003] The standard state of the rebound tester and whether the measurement and calibration are accurate are the first major factors affecting the accuracy of the rebound tester. At present, the national metrological verification regulations "Rebound Tester" 817 and the industry standard "Technical Regulations for Testing Concrete Compressive Strength by Rebound Method" JGJ / T23 on the verification of rebound tester and the application of rebound method have made detailed provisions on the standard state, verification and maintenance of the instrument; among them, the rebound rate is required to be in Rockwell hardness HRC The rebound hammer is a mechanical instrument that is repeatedly used within the calibration cycle. The instrument may be repeatedly struck thousands or tens of thousands of times within a six-month calibration cycle. The performance of the instrument is affected by the test environment, the number of strikes, spring fatigue, pointer wear, and the internal structure of the body. The standard state is prone to change due to multiple factors such as contamination, so the application regulations of the rebound method also require that the instrument be calibrated with anvils before and after the test to ensure that the instrument's indication is stable within the calibration period. However, in the study, we found that different rebound hammers that have passed the calibration and whose daily calibration values ​​of the anvils are within the range of 80±2 within the calibration period still have rebound values ​​that differ by 3-4 scale values ​​on some concrete components. The reason is that the rebound hammer produces elastic-plastic deformation on the concrete surface, which is different from the nearly elastic deformation during the anvil calibration, and there is no linear relationship between the two deformations. The rebound hammer can cause a difference of (3-4) MPa in the strength value of the concrete measurement area within the commonly used indication range of 20-60 by 3-4 scale values, which directly affects the accuracy of engineering inspection.

[0004] How to make the rebound hammer that has passed the calibration overcome the problem of occasional low detection accuracy of the above-mentioned rebound hammer during actual detection when used, and further improve the stability and accuracy of the measurement value of the rebound hammer during the calibration cycle, is an important research topic in this field. Summary of the invention

[0005] In view of the above-mentioned problems, the present invention aims to provide a research method for the segmented calibration measuring points of the concrete rebound test hammer. By exploring the relationship between the calibration value of the medium-sized concrete rebound test hammer on a light steel needle and the hardness and weight of the steel anvil within the calibration period, it is found that when the Rockwell hardness of the steel anvil is 60±2 and the weight is 1.03kg, the calibration value of the rebound test hammer is 40±1, which reduces the calibration value of the rebound test hammer and improves the stability and usage accuracy of the rebound test hammer in the commonly used concrete strength range.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A method for studying the segmented rate determination of measuring points of a concrete rebound test hammer, the method comprising:

[0008] S1: Study the relationship between the rebound test value and the hardness and quality of the steel anvil, and determine the factors affecting the rebound test value;

[0009] S2: After determining the factors influencing the calibration value of the rebound hammer, the best calibration point of the rebound hammer is found by using the segmented calibration method, and the standard steel anvil at the calibration point is defined as the light steel anvil;

[0010] S3: Evaluate the permissible error value of the concrete rebound test hammer using a lightweight steel anvil at the optimal measuring point;

[0011] S4: Use the classification research method to explore the allowable deviation of the light steel anvil at the optimal metering point and determine the allowable deviation of the light steel anvil at the optimal metering point.

[0012] Preferably, the specific process of studying the relationship between the rebound tester calibration value and the hardness and mass of the standard steel anvil and determining the influencing factors of the rebound tester calibration value in step S1 is:

[0013] S1.1 Study on the influence of anvil hardness change on the rebound test value

[0014] By controlling the hardness of low-hardness light steel anvils, the influence of the hardness change of low-hardness light steel anvils on the calibration value of the rebound tester was explored. The results showed that the hardness of the steel anvil decreased by 22 degrees from HRC60 to HRC38, while the calibration average value decreased by only 2 divisions from 40 to 38, and the change range was very limited.

[0015] S1.2 Study on the influence of the weight change of the steel anvil on the rating of the rebound test hammer

[0016] By controlling the weight of the steel anvil, the influence of the weight change of the standard steel anvil on the rebound tester rate value was investigated. The results showed that when the weight of the standard steel anvil was 697g, 1032.5g, 1443.5g and 2286.5g, the corresponding steel anvil rate values ​​were 30, 40, 50 and 60 respectively. The weight change has a significant influence on the steel anvil rate value.

[0017] Preferably, the specific process of finding the best segmented metering point by using the segmented rate measurement method described in step S2 is:

[0018] S2.1 After obtaining the significant influence of the steel anvil weight change on the steel anvil calibration value through step S1.2, find the best measurement point, specifically, turn and remove the weight of the 16.0 kg standard steel anvil, turn 1.0 kg each time, and measure the calibration value;

[0019] S2.2 preliminarily selects light steel anvils with rated values ​​of 30, 40, 50 and 60 respectively, compares the weight of the steel anvils with corresponding rated values ​​with the weight of the corresponding rated values ​​in step S2.1, and finds that the light steel anvils with rated values ​​of 30, 50 and 60 are not suitable as segmented metering points. Select the light steel anvil with a rated value of 40 as the segmented metering point.

[0020] Preferably, the specific process of evaluating the allowable error value of the concrete rebound test hammer using the light steel anvil at the optimal measurement point in step S3 is:

[0021] S3.1. A steel anvil with a metering point of 40 was selected and placed steadily on a cement floor with a relatively high rigidity for testing. Five rebound testers with a calibration value of 80 on a standard steel anvil were selected for the test. Six test personnel calibrated a total of 3,600 times in three months.

[0022] S3.2 processes and evaluates the above 3600 data, showing that the calibration value [39,41] has the highest probability of occurrence, proving that setting the optimal segmented calibration point to 40 is reasonable and feasible.

[0023] Preferably, the calibration process and calibration conditions described in step S3.1 are:

[0024] (1) The calibration test should be carried out at room temperature of 5 to 35°C;

[0025] (2) The surface of the anvil should be dry and clean, and should be placed firmly and flat on a rigid object;

[0026] (3) The rebound value should be the average value of the stable rebound results of five consecutive downward bounces, excluding the maximum and minimum values;

[0027] (4) The calibration test should be carried out in four directions, and the impact rod should be rotated 90 degrees before impacting in each direction. The average rebound value in each direction should be 40±1.

[0028] Preferably, the specific process of exploring the allowable deviation of the light steel anvil at the optimal metering point by using the classification research method described in step S4 is:

[0029] S4.1 Explore the relationship between hardness ±2 and rating value ±2

[0030] (1) Using a standard steel anvil weighing 16.0 kg and a light steel anvil, steel cores with hardnesses of 58, 60, and 62 are made for calibration tests;

[0031] (2) The results show that when the anvil hardness is in the range of HRC [58,62], the hardness change has almost no effect on the calibration result, that is, there is no necessary connection between the hardness ±2 and the calibration value ±2, and there is no error transmission;

[0032] S4.2 Permissible Deviations for Lightweight Anvils in Determining Optimum Gauge Points

[0033] It can be seen from the experimental results of step S3 that the probability that the light steel anvil rate setting value at the best metering point falls within the interval of 40±1 is above 95%. Therefore, it is feasible to set the accuracy of the allowable deviation of the light steel anvil rate setting value to ±1.

[0034] Preferably, the rebound hammer used in this research method is a digital medium-sized rebound hammer.

[0035] The beneficial effects of the present invention are as follows: the present invention discloses a method for studying the measuring points of the segmented rate of a concrete rebound test hammer. Compared with the prior art, the present invention has the following improvements:

[0036] (1) In view of the problems existing in the background technology, the present invention designs a research method for measuring points of segmented calibration of a concrete rebound test hammer. By exploring the relationship between the calibration value of a medium-sized concrete rebound test hammer on a light steel needle and the hardness and weight of the steel anvil within the calibration period, it is found that when the Rockwell hardness of the steel anvil is 60±2 and the weight is 1.03kg, the calibration value of the concrete rebound test hammer is 40±1, which reduces the calibration value of the rebound test hammer and improves the stability and use accuracy of the rebound rate of the rebound test hammer in the commonly used concrete strength range;

[0037] (2) At the same time, the present invention designs an optimization processing method for evaluating the calibration results based on the current specifications. After the steel anvil with a calibration value of 40 is processed by this method, the probability that the calibration value of the rebound tester 40±1 falls within this interval is more than 95%, which proves that it is feasible to set the accuracy of the allowable deviation of the calibration value of the light steel anvil to ±1. In addition, the present invention provides the specific operation and method of the calibration measurement of the light steel anvil in combination with the calibration method of the standard steel anvil;

[0038] (3) This method proves that it is completely feasible to use a light steel anvil to perform segmented calibration measurement of the rebound hammer within the commonly used range. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The graph is a relationship between the weight change of the steel anvil and the rated value of the present invention.

[0040] Figure 2 It is a curve diagram of the relationship between the rated value and frequency of the light steel anvil of the present invention.

[0041] Figure 3 It is a curve diagram of the relationship between the rated value and probability of the light steel anvil of the present invention.

[0042] Among them: Figure 1 Middle: (a) is the MR curve diagram of the steel anvil weight change and the calibration value; (b) is the Ln(M)-R curve diagram of the steel anvil weight change and the calibration value. DETAILED DESCRIPTION

[0043] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0044] Example 1: See Figure 1-3 As shown, a segmented calibration measurement research method for a lightweight rebound hammer calibration anvil, the research method comprising:

[0045] S1: Study the relationship between the rebound test value and the hardness and quality of the steel anvil, and determine the influencing factors of the rebound test value. The specific process is as follows:

[0046] According to the principle of the rebound tester, the calibration value of the rebound tester under standard conditions is mainly determined by two factors: one is the hardness of the steel anvil, and the other is the weight of the steel anvil. This step mainly explores the influence of hardness and weight on the calibration value of the steel anvil, and finds the best measurement point for segmented calibration based on their influence on the rate. The specific process is as follows:

[0047] S1.1 Study on the influence of anvil hardness change on the rebound test value

[0048] In order to explore the feasibility of adjusting the anvil rate value by hardness, two groups of anvils with different hardness were designed for experiments. The experimental results are shown in Table 1:

[0049] Table 1: Comparison of calibration results of steel anvils with different hardness

[0050]

[0051] From the experimental results in Table 1, it can be seen that the hardness of two light steel anvils of the same weight decreased by 22 degrees from HRC60 to HRC38, while the average value of the calibration value decreased by only 2 divisions from 40 to 38, and the change range was very limited. It can be seen that the calibration value is not sensitive to the change of hardness. If the hardness of the steel anvil is further reduced, it is necessary to find it in non-metallic materials. However, the stability and reusability of low-hardness non-metallic materials are poor. Therefore, the effect of adjusting the calibration value of the steel anvil by adjusting the hardness is not ideal.

[0052] S1.2 Study on the influence of the weight change of the steel anvil on the rating of the rebound test hammer

[0053] Four light steel anvils with hardness of HRC60±2 were designed to calibrate the concrete rebound test hammer. The calibration values ​​are shown in Table 2:

[0054] Table 2: Specifications of Lightweight Steel Anvil

[0055]

[0056] From Table 2, it can be seen that the weight change of the anvil has a significant effect on the calibration value;

[0057] S2: After determining the factors affecting the calibration value of the rebound hammer, the best measurement point of the calibration value of the rebound hammer is found by using the measurement method of segmented calibration. The specific process is as follows:

[0058] S2.1 Select a 16.0kg standard steel anvil and start turning to remove weight from the 16.0kg standard steel anvil, turning 1.0kg each time, and find the law of the change of the calibration value with weight. The test results are shown in Table 3:

[0059] Table 3: Exploration of anvil weight and corresponding rate values

[0060]

[0061] It can be seen from the experimental data in Table 3 that the results prove that the calibration value changes nonlinearly with the weight of the steel anvil; this indicates that the calibration value is affected by many factors, such as the weight of the steel anvil, the stability of the steel anvil in contact with the ground, the shaking of the steel anvil during impact, and the verticality of the personnel during impact. In addition, during the exploration process, it was found that the light steel anvil is lighter in weight and has a poorer fit with the ground. Moreover, the light steel anvil is more sensitive to the stiffness and flatness of the base layer under the steel anvil during instrument calibration, and the verticality of the instrument during personnel operation. Therefore, a special rubber base is specially designed for the light steel anvil. The base is made of rubber and silicone soft rubber with a Shore hardness of 70. The flat inner surface of the rubber base can better wrap the steel anvil. The bottom surface of the rubber base is designed with anti-slip grooves, which has better fit and grip, further ensuring that the steel anvil is in stable contact with the ground to ensure the stability of the calibration value.

[0062] S2.2 Since the common scale range of the rebound hammer is 20 to 60, we initially envisioned that the light steel anvils with the calibration values ​​of 30, 40, 50, and 60 were used. However, through experiments (see the results), Figure 1 ) is compared with the measurement result of step S2.1 (Table 3). It is found that when the mass of the steel anvil is 0.7kg, the stability of the calibration value is poor, and when it is around 2.4kg, the calibration value is very sensitive to the weight of the steel anvil. Therefore, the calibration value of 30 corresponding to 0.7kg and the calibration value of 60 corresponding to 2.4kg are not suitable as segmented measurement points; the calibration values ​​of 40 and 50 are relatively stable, but considering that within the commonly used range of concrete strength, the rebound value of about 40 is used more frequently, the value is more characteristic, and it is just in the middle of the linear segment. Therefore, it is more reasonable to set the segmented measurement point to 40. The relationship curve between the weight change of the steel anvil and the calibration value is shown in Figure 1 As shown in (a) and (b);

[0063] From the experimental data and Figure 1 It can be seen from the relationship curve that when the weight of the steel anvil is between 7.0kg and 16.0kg, the calibration result is still in the range of 80±2, and the calibration value is not sensitive to the change of the weight of the steel anvil; in the range of 6kg to 2.5kg, the calibration value is relatively stable and changes evenly; when it drops from 2.5kg to 2.4kg, the calibration value suddenly drops to about 60, indicating that when it is around 2.4kg, the calibration value is very sensitive to the change of the weight of the steel anvil; from 2.4kg-1.4kg-1.0kg-0.7kg, the influence of the steel anvil weight on the calibration value is close to a linear relationship and is relatively stable; when the weight of the steel anvil is 0.7kg, the calibration result is between 22-35, because the weight of the steel anvil is light, and the steel anvil is easy to bounce during the impact, resulting in large data fluctuations;

[0064] Through the analysis of the test data and relationship curve between the anvil weight and the calibration value, it is reasonable and feasible to set the optimal segmented calibration point to 40 for the following reasons:

[0065] (1) The concrete strength of the measured area corresponding to the rebound value of 40, which is the most commonly used 40MPa in our daily life, is an ideal daily rate measurement point.

[0066] (2) According to the test curve ( Figure 1 (a) and (b) show that the linear relationship between the calibration values ​​30, 40, and 50 is good, and 40 is located in the middle of the linear segment. The anvil weight and the calibration value are relatively stable in this segment.

[0067] (3) According to the exploratory test, when the calibration value is below 30, the stability of the measured calibration value is poor because the weight of the steel anvil is too light;

[0068] (4) According to the exploratory test, when the calibration value is in the range of 50-70, the linearity of the curve between the steel anvil weight and the calibration value is poor, the calibration value is sensitive to the change of the steel anvil weight, and the steel anvil weight is difficult to control;

[0069] (5) The standard steel anvil rate is set at 80, and the light steel anvil rate is set at 40, which is exactly half of the standard steel anvil rate. The data is more distinctive and convenient to use and remember;

[0070] S3: Use the light steel anvil at the best measuring point to evaluate the allowable error value of the concrete rebound test hammer. The specific process is as follows:

[0071] S3.1 In order to ensure the precision and accuracy of the rebound tester, the allowable error of the calibration results of the instrument at each metering point must be tested and analyzed. The test uses a light steel anvil with a metering point of 40, which is stably placed on a cement floor with greater rigidity for testing. In order to reduce the error caused by the instrument and personnel, the test uses 5 instruments with a calibration value of 80 on a standard steel anvil. Six testers have calibrated 3,600 times in 3 months;

[0072] S3.2 The above 3600 data are processed and evaluated, and the evaluation method includes a standardized evaluation method and an improved evaluation method:

[0073] (1) Standard evaluation method: Evaluation shall be carried out in accordance with the calibration method of Technical Specification for Testing Concrete Compressive Strength by Rebound Method JGJ / T23;

[0074] The improved evaluation method and its operating specifications include:

[0075] (1) Method 1: The calibration test operation is consistent with the current specification requirements and is carried out in four directions, with three shots in each direction. However, the range of the results of the three shots in each direction is required to be no greater than 1, otherwise the calibration data in that direction will be invalidated;

[0076] (2) Method 2: The calibration test is performed in accordance with the current specification requirements and is conducted in four directions. Five shots are fired in each direction, and one maximum value and one minimum value are removed.

[0077] The steel anvil calibration results shown in Table 4 are obtained:

[0078] Table 4: Comparison of evaluation methods for anvil calibration results

[0079]

[0080] It can be seen from Table 4 that the calibration value range of No. Ⅱ steel anvil directly measured according to the standard method is 37-42, the average value is 39.78, the standard deviation is 0.950 (referring to the standard deviation compared with the standard rebound value), and the coefficient of variation is 0.024 (referring to the coefficient of variation compared with the standard rebound value); Method 1 and Method 2 are the results obtained by processing the data that do not meet the requirements according to the improved evaluation method. Since Method 1 and Method 2 in the table eliminate the points with large discreteness, the calibration interval, standard deviation and coefficient of variation are slightly reduced, and the average value does not change much; the calibration values ​​of the three methods and their frequency and probability curves are shown in Figure 2 and Figure 3 As shown;

[0081] pass Figure 2 , Figure 3 It can be seen that the frequency of occurrence of the steel anvil calibration values ​​corresponding to the three methods is basically the same, and the frequency of occurrence is 39, 41, 40, 38, 42, and 37 from high to low. The probability of the calibration value [39, 41] is the highest, among which the probability of the standard method, method one, and method two is 93.86%, 95.10%, and 96.44% respectively. 6.14% of the calibration values ​​of the standard method fall outside the interval [39, 41], and 4.90% and 3.56% of the calibration values ​​of method one and method two fall outside the interval [39, 41] respectively. This shows that the evaluation methods of method one and method two can ensure that the guarantee rate of the calibration value allowable deviation of ±1 reaches more than 95%, and method two is better than method one.

[0082] Step S4: Using the classification research method to explore the allowable deviation of the light steel anvil at the optimal metering point, determine the allowable deviation of the light steel anvil at the optimal metering point, and the specific process is as follows:

[0083] S4.1 Explore the relationship between hardness ±2 and rating value ±2

[0084] (1) The standard steel anvil used for medium-sized rebound hammer calibration has a hardness of HRC60 and an allowable deviation of ±2. Is it feasible to accurately allow the allowable deviation of the rebound hammer calibration value to ±1? We used a standard steel anvil weighing 16.0 kg and a light steel anvil to make steel cores with hardnesses of 58, 60, and 62 for calibration tests. The results of the steel anvil hardness calibration tests are shown in Tables 4 and 5:

[0085] Table 5: Comparison of calibration results of steel anvils with different hardness (16kg standard steel anvil)

[0086]

[0087] Table 6: Comparison of calibration results of steel anvils with different hardness (light steel anvil)

[0088]

[0089] It can be seen from the test data in Table 5 that the calibration values ​​of the 16.0 kg standard steel anvil with hardness of 58, 60, and 62 are all between 78 and 82, and the hardness change has almost no effect on the calibration results;

[0090] It can be seen from the test data in Table 6 that the calibration values ​​of the light steel anvil when the hardness is 58, 60, and 62 are all between 38 and 41, and the hardness change has almost no effect on the calibration results;

[0091] Therefore, it can be seen from the results of Tables 5 and 6 that, whether it is a standard steel anvil or a light steel anvil, when the hardness is in the range of [58,62], the hardness has little effect on the calibration result of the ordinary medium-sized rebound hammer; because the hardness of the steel anvil and the impact rod is equivalent, when the hardness of the steel anvil is in the range of HRC [58,62], the deformation of the steel anvil and the impact rod is approximately elastic deformation, and the slight change in hardness has a very limited effect on the calibration value, that is, the allowable deviation of the hardness ±2 will not be transferred to the calibration value or amplified thereby, that is, there is no necessary connection between the hardness ±2 and the calibration value ±2, and there is no error transmission;

[0092] S4.2 Determination of allowable deviations of rating values ​​for light steel anvils

[0093] It can be seen from the experimental results of the standard evaluation method in step S3 that the stable interval of the calibration value of light steel anvils is [37-42], and after processing the steel anvil with a calibration value of 40 through step three method two (improved calibration method), the calibration value interval is [38-42]. The probability that the calibration value 40±1 falls within this interval is above 95%. Therefore, it is feasible to set the accuracy of the allowable deviation of the calibration value of light steel anvils to ±1.

[0094] Preferably, the rebound hammer used in this research method is a digital medium-sized rebound hammer.

[0095] Through the above research methods, the present invention determines the specific operation methods and requirements of the rebound hammer calibration as follows (selected evaluation method):

[0096] The specific operation method of the rebound hammer segmented calibration measurement is based on the provisions of Article 3.2.2 of the Technical Specification for Testing Concrete Compressive Strength by Rebound Method JGJ / T 23-2011 and Article 7.2.3.10 of the Rebound Hammer JJG817-2011. The specific requirements are as follows:

[0097] (1) The calibration test should be carried out at room temperature of (5-35)°C;

[0098] (2) The surface of the anvil should be dry and clean, and should be placed firmly and flat on a rigid object;

[0099] (3) The rebound value should be the average value of the stable rebound results of five consecutive downward bounces, excluding the maximum and minimum values ​​(method one); range method: the rebound value should be the stable rebound results of three consecutive downward bounces, and the range should not be greater than 1 (method two)

[0100] (4) The calibration test should be carried out in four directions, and the impact rod should be rotated 90 degrees before impacting in each direction. The average rebound value in each direction should be 40±1.

[0101] And through the exploration process of the above research methods, we determined:

[0102] (1) Specific parameters of the lightweight rebound hammer calibration steel anvil as described in the present invention, the hardness and weight of the lightweight steel anvil used for rebound hammer calibration, i.e., Rockwell hardness 60±2 and weight 1.03 kg;

[0103] (2) The segmented measuring points in the commonly used interval within the range of the rebound tester are determined, that is, the point with a fixed value of 40 on the light steel anvil studied in this paper;

[0104] (3) It was determined that it is feasible to calibrate the rebound hammer on a light steel anvil with a hardness of HRC60±2 with an allowable deviation of ±1, and an optimized processing method for evaluating the calibration results was given;

[0105] (4) Combined with the calibration method of standard steel anvil, the specific operation and method of calibration measurement of light steel anvil are given;

[0106] (5) The research and application of rebound hammer segmented calibration measurement has filled the gap in this field at home and abroad, and improved the accuracy of rebound hammer in the commonly used concrete strength range;

[0107] (6) It is completely feasible to use a light steel anvil to perform segmented calibration measurement in the commonly used range of the rebound tester.

[0108] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A research method for determining the measuring points of the concrete rebound test hammer segment rate, characterized by: The method comprises: S1: Study the relationship between the rebound test value and the hardness and quality of the steel anvil, and determine the factors affecting the rebound test value; The specific process of studying the relationship between the rebound test value and the hardness and mass of the standard steel anvil and determining the influencing factors of the rebound test value described in step S1 is as follows: S1.1 Study on the influence of anvil hardness change on the rebound test value By controlling the hardness of low-hardness light steel anvils, the influence of the hardness change of low-hardness light steel anvils on the calibration value of the rebound tester was explored. The results showed that the hardness of the steel anvil decreased by 22 degrees from HRC60 to HRC38, while the calibration average value decreased by only 2 divisions from 40 to 38, and the change range was very limited. S1.2 Study on the influence of the weight change of the steel anvil on the rating of the rebound test hammer By controlling the weight of the steel anvil, the influence of the weight change of the standard steel anvil on the rebound test value was explored. The results showed that when the weight of the standard steel anvil was 697g, 1032.5g, 1443.5g, and 2286.5g, the corresponding steel anvil values ​​were 30, 40, 50, and 60, respectively. The weight change had a significant effect on the steel anvil value. S2: After determining the factors influencing the calibration value of the rebound hammer, the best calibration point of the rebound hammer is found by using the segmented calibration method, and the standard steel anvil at the calibration point is defined as the light steel anvil; The specific process of finding the best segmented metering point by using the segmented rate measurement method described in step S2 is as follows: S2.1 After obtaining the significant influence of the steel anvil weight change on the steel anvil calibration value through step S1.2, find the best measurement point, specifically, turn and remove the weight of the 16.0 kg standard steel anvil, turn 1.0 kg each time, and measure the calibration value; S2.2 Preliminarily select light steel anvils with rated values ​​of 30, 40, 50, and 60, respectively, and compare the weights of the steel anvils with the corresponding rated values ​​with the weights of the steel anvils with the corresponding rated values ​​in step S2.

1. It is found that the light steel anvils with rated values ​​of 30, 50, and 60 are not suitable for segmented measurement points, and the light steel anvil with a rated value of 40 is selected as the segmented measurement point; S3: Evaluate the permissible error value of the concrete rebound test hammer using a lightweight steel anvil at the optimal measuring point; The specific process of evaluating the allowable error value of the concrete rebound test hammer using the light steel anvil at the optimal measurement point described in step S3 is as follows: S3.

1. A steel anvil with a metering point of 40 was selected and placed steadily on a cement floor with a relatively high rigidity for testing. Five rebound testers with a calibration value of 80 on a standard steel anvil were selected for the test. Six test personnel calibrated a total of 3,600 times in three months. S3.2 processes and evaluates the above 3600 data, showing that the calibration value [39,41] has the highest probability of occurrence, proving that setting the optimal segmented calibration point to 40 is reasonable and feasible; The calibration process and calibration conditions described in step S3.1 are: (1) The calibration test should be carried out at room temperature of 5 to 35°C; (2) The surface of the anvil should be dry and clean, and should be placed firmly and flat on a rigid object; (3) The rebound value should be the average value of the stable rebound results of five consecutive downward bounces, excluding the maximum and minimum values; (4) The calibration test should be carried out in four directions, and the impact rod should be rotated 90 degrees before impacting in each direction. The average rebound value in each direction should be 40±1; S4: Use the classification research method to explore the allowable deviation of the light steel anvil at the optimal metering point and determine the allowable deviation of the light steel anvil at the optimal metering point; The specific process of exploring the allowable deviation of the light steel anvil at the optimal metering point by using the classification research method described in step S4 is as follows: S4.1 Explore the relationship between hardness ±2 and calibration value ±2 (1) Using a standard steel anvil weighing 16.0 kg and a light steel anvil, steel cores with hardnesses of 58, 60, and 62 were made for calibration tests; (2) The results show that when the anvil hardness is in the range of HRC [58,62], the hardness change has almost no effect on the calibration result, that is, there is no necessary connection between the hardness ±2 and the calibration value ±2, and there is no error transmission; S4.2 Permissible Deviations for Lightweight Anvils to Determine Optimal Gauge Point It can be seen from the experimental results of step S3 that the probability that the light steel anvil rate setting value at the optimal metering point falls within the interval of 40±1 is above 95%. Therefore, it is feasible to set the accuracy of the allowable deviation of the light steel anvil rate setting value to ±1.

2. The method for determining the measuring points of the concrete rebound test hammer segment rate according to claim 1 is characterized by: The rebound hammer used in this research method is a digital medium-sized rebound hammer.

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