Concrete strength heavy rebound method testing apparatus and method

Abstract

The present application belongs to the technical field of non-destructive testing of concrete strength, and discloses a heavy rebound method concrete strength detection device and method. The device comprises a tubular shell, a striking rod, a guide rod, an impact hammer, a sliding block, a tension spring and an adjusting sleeve. The two preset installation positions in the shell are switched by driving the sliding block through the adjusting sleeve to realize stable output of 4.5J and 5.5J double kinetic energy. The method combines the double kinetic energy characteristics of the device and adopts the river channel, plain and plateau special strength measurement curve to convert the concrete strength in various topographic features areas. The present application solves the problem of insufficient kinetic energy of the existing device and inaccurate measurement of high-grade concrete, does not need to take core and damage the structure, the detection error meets the national standard requirements, is suitable for C40-C60 concrete, meets the quality detection requirements of large load engineering such as bridges and tunnels, and significantly improves the detection accuracy and efficiency.

Description

Technical Field

[0001] This invention belongs to the field of strength testing technology, specifically relating to equipment and method for testing concrete strength using the heavy rebound method. Background Technology

[0002] The rebound hammer is a core non-destructive testing device in the engineering field used to test the compressive strength of concrete. Its working principle is based on the positive correlation between the surface hardness and internal compressive strength of concrete: a spring inside the device drives a hammer to impact a spring-loaded rod on the concrete surface with a preset kinetic energy. The rebound value generated after the spring bounces back is converted into a strength curve to quickly obtain the estimated strength of the concrete. Because of its ease of operation and non-destructive nature, this device is widely used for quality testing of concrete structures such as buildings, bridges, tunnels, and foundations, and is a key tool for engineering construction acceptance and quality supervision.

[0003] However, with the widespread application of high-grade concrete (C50 and above, corresponding to compressive strength ≥59.9MPa) in heavy-load engineering projects (such as bridge load-bearing structures, tunnel linings, and large foundations), existing rebound hammers and testing methods have gradually revealed insurmountable technical defects:

[0004] On the one hand, the nominal kinetic energy of the existing rebound hammer is only 2.2J. Faced with the higher density and surface hardness of high-grade concrete, this kinetic energy is easily absorbed by the rigidity of the concrete surface, resulting in insufficient rebound of the impact rod, large dispersion of rebound value, and detection error exceeding the national standard allowable range (≤10%). It cannot reflect the true strength of concrete and ultimately requires core sampling for verification, which damages the structural integrity and reduces the detection efficiency.

[0005] On the other hand, existing equipment lacks a stable and reliable kinetic energy adjustment structure. If a conventional stepless adjustment threaded telescopic design is used, long-term impact will cause problems such as slippage and loosening. If a detachable part adjustment is used, it is easy to encounter problems such as uncontrolled contraction after the spring loses its limit and cannot be reconnected, making it difficult to achieve the precise kinetic energy switching required for high-strength concrete of different grades. At the same time, the existing testing methods use a general strength test curve, which does not take into account the differences in local materials, climate and curing conditions in different regions, further amplifying the testing deviation and failing to meet the precise testing requirements of high-strength concrete. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a heavy-duty rebound method for testing concrete strength. It adapts to more scenarios by adjusting the dual-energy device, and provides a more accurate test reference calculation by determining correction values ​​for regions with diverse topographic features.

[0007] The technical solution adopted in this invention is as follows:

[0008] In a first aspect, the present invention provides a heavy-duty rebound method testing device for concrete strength, which uses a dual-energy mode to test concrete strength, including a tubular shell, one end of which has a first opening for an internal impact rod to pass through, and a second opening at the tail that is fastened and fixed by a bottom cover.

[0009] The housing is also equipped with an impact hammer and a clamping mechanism that slide along the housing axis. The clamping mechanism is connected to the end of a guide rod that is sleeved inside the impact rod and drives the impact hammer to slide. The clamping mechanism is equipped with a claw that releases the impact hammer by contacting the bottom cover.

[0010] The housing also contains a slider, and a tension spring is sleeved on the outside of the guide rod between the slider and the impact hammer.

[0011] The housing has at least two mounting positions for limiting the tension spring to the corresponding kinetic energy length of the slider. The first opening of the housing is provided with an adjusting sleeve sleeved outside the striking rod. The adjusting sleeve has an operating end outside the housing and a connecting end that extends into the housing from the first opening and cooperates with the slider to adjust the mounting position of the slider.

[0012] In conjunction with the first aspect, the present invention provides a first embodiment of the first aspect, wherein the adjusting sleeve is threadedly connected to the housing, and the position of the slider in the two mounting positions within the housing is adjusted by changing the adjusting sleeve with different length connecting ends.

[0013] In conjunction with the first embodiment of the first aspect, the present invention provides a second embodiment of the first aspect, wherein the adjusting sleeve is threadedly engaged with the slider, and the housing is further provided with a pin having an operating end on the outside of the housing. The pin is inserted into the slider at the mounting position corresponding to the longest initial length of the tension spring to achieve limiting and fixing. When the adjusting sleeve is fixed to the slider by the pin, the adjusting sleeve is replaced. When the adjusting sleeve is threadedly fixed to the slider, the adjusting sleeve and the housing are simultaneously threadedly fixed in the same direction.

[0014] In conjunction with the first aspect, the present invention provides a third embodiment of the first aspect, wherein the channels from the first opening to the second opening of the housing are respectively a sleeve channel for sliding limit of the adjusting sleeve and an impact channel for sliding limit of the impact hammer. The sleeve channel is provided with an adjusting channel whose cross-sectional radius is larger than that of the sleeve channel. The slider slides along the axis of the housing within the adjusting channel. The two ends of the adjusting channel are respectively two mounting positions, and each mounting position is provided with an internal thread.

[0015] In conjunction with the third embodiment of the first aspect, the present invention provides a fourth embodiment of the first aspect, wherein the connecting end of the adjusting sleeve is a tubular structure located between the sleeve channel and the striking rod, and the end of the connecting end extending into the housing has a corresponding slider and a retaining ring that pulls and limits the slider toward the first opening. A toothed block is provided on the outer wall of the connecting end near the retaining ring, and the slider has a toothed groove corresponding to the toothed block.

[0016] The adjusting sleeve is rotated by the engagement of the toothed block and the toothed groove to fix / release the slider to the mounting position. Pulling the adjusting sleeve causes the retaining ring to press against and restrict the slider, overcoming the tension of the tension spring towards the second opening to adjust the slider position.

[0017] In conjunction with the fourth embodiment of the first aspect, the present invention provides a fifth embodiment of the first aspect, wherein the housing is provided with an external thread on the outer wall of the first opening, and the operating end of the adjusting sleeve is provided with an internal thread that mates with the external thread. When the internal thread of the adjusting sleeve contacts the external thread of the housing, the tooth groove and the tooth block disengage and the slider is fixed at the mounting position of the tension spring with the shortest initial length.

[0018] Secondly, the present invention provides a testing method for testing the strength of concrete structures using the heavy rebound concrete strength testing equipment described in any of the above claims, as follows:

[0019] Step 1: Determine the design strength grade range of the high-grade concrete to be tested. If the strength grade is C40~C55, switch the testing equipment to the 4.5J kinetic energy setting by adjusting the sleeve; if the strength grade is C55~C60, switch to the 5.5J kinetic energy setting.

[0020] Step 2: Arrange test areas on the concrete component to be tested. The test areas should be evenly distributed on the testable surface of the component, avoiding embedded parts and defective parts. The distance between adjacent test areas should not be greater than 2m, and the distance between the test area and the end of the component should be 0.2-0.5m. The number of test areas for a single component should not be less than 10, and the area of ​​the test area should not be greater than 0.04m2.

[0021] Step 3: Use the testing equipment to perform rebound testing on each test area, ensuring that the equipment axis is perpendicular to the concrete test surface. Read 16 rebound values ​​for each test area, with the readings accurate to 1.

[0022] Step 4: Remove the 3 maximum and 3 minimum values ​​in each test area, and calculate the average rebound value of the remaining 10 rebound values, accurate to 0.1.

[0023] Step 5: Determine the type of the area to be detected, which is a river, plateau, or plain, and retrieve the third-quarter correction value parameters corresponding to the kinetic energy level and area type;

[0024] Step 6: Substitute the average rebound value and corresponding correction value parameters of the test area into the high-grade concrete strength test curve to calculate the concrete strength conversion value of each test area. Then, determine the estimated value of the concrete strength of the component according to the number of test areas. When the number of test areas is not less than 10, calculate the estimated strength according to the requirement that the guarantee rate is not less than 95%.

[0025] In conjunction with the second aspect, the present invention provides a first embodiment of the second aspect, wherein when the testing equipment adopts the 4.5J kinetic energy setting, the corresponding correction value parameters for the third quarter are: the correction coefficient for the river area is 0.95-1.05, the correction coefficient for the plateau area is 1.02-1.12, and the correction coefficient for the plain area is 0.98-1.08. The correction value parameters are obtained by fitting the material characteristics, curing conditions, and concrete strength test data of the corresponding area in the third quarter.

[0026] In conjunction with the second aspect, the present invention provides a second implementation method of the second aspect. When the detection equipment adopts the 5.5J kinetic energy setting, the corresponding correction value parameters for the third quarter are: the correction coefficient for the river area is 1.00-1.10, the correction coefficient for the plateau area is 1.05-1.15, and the correction coefficient for the plain area is 1.02-1.12. The correction value parameters and the 4.5J setting parameters are synchronously calibrated based on the same set of regional test data.

[0027] In conjunction with the second aspect, the present invention provides a third embodiment of the second aspect. Before the rebound test in step 3, the testing equipment needs to be calibrated on a standard steel anvil, and the calibrated rebound value meets the equipment calibration requirements. In step 4, if the average rebound value of the test area has a large dispersion, the Grubbs test method is used to remove outliers. After removal, the number of remaining rebound values ​​is not less than 8. Otherwise, the test area is reselected for testing.

[0028] The beneficial effects of this invention are as follows:

[0029] (1) The device of the present invention achieves stable and precise switching between 4.5J and 5.5J dual kinetic energy through the coordinated design of the front-end adjusting sleeve and the slider. Both schemes avoid the defects of traditional adjustment structures: Scheme 1 controls the pin limit slider by button control. When changing the adjusting sleeve with different depths, it can avoid the spring contraction and loss of control. The operation is simple and efficient, and the kinetic energy switching can be completed without complicated tools; Scheme 2 uses the combination structure of spline transmission and double-set thread fixing to make the slider rigidly fixed with the rebound spring housing after adjustment. The adjusting sleeve only undertakes the sliding sleeve function and does not bear the impact load, which completely solves the problem of stripping and loosening in long-term use and ensures the stability of kinetic energy output.

[0030] (2) The dual-energy design of this invention is precisely adapted to high-grade concrete of different strength grades. The 4.5J setting can efficiently detect C40-C55 concrete, and the 5.5J setting can effectively break through the hardness barrier of C55-C60 concrete, so that the impact kinetic energy is fully transferred to the inside of the concrete. The correlation between the rebound value and the actual strength is significantly improved, and the detection error is controlled within 10%. It completely solves the problem of inaccurate measurement caused by insufficient kinetic energy of existing equipment. Non-destructive testing can be achieved without core sampling verification, which protects the integrity of the engineering structure.

[0031] (3) The present invention has established special strength test curves for different regions and different materials in areas with diverse landforms, realizing dual precision detection of kinetic energy adaptation and curve exclusive, avoiding the problem of general curves not being suitable for regional projects, making the test results more in line with the actual project, and providing a reliable basis for the quality control of high-load, high-grade concrete structures such as bridges, tunnels, and foundations. Attached Figure Description

[0032] Figure 1 This is the initial isometric view of the detection device of the rotationally adjustable scheme in this embodiment of the invention under a kinetic energy state of 5.5J;

[0033] Figure 2 This is an initial plan view of the detection device of the rotary adjustable scheme in this embodiment of the invention under a kinetic energy state of 5.5J;

[0034] Figure 3 This is an isometric view of the inward contact of the detection device of the rotary adjustable scheme in this embodiment of the invention under a kinetic energy state of 5.5J;

[0035] Figure 4 This is a plan view of the detection device of the rotary adjustable scheme in this embodiment of the invention, in an inward contact state of 5.5J kinetic energy.

[0036] Figure 5 This is an isometric view of the release impact hammer of the detection device of the rotary adjustable scheme in this embodiment of the invention under a kinetic energy state of 5.5J;

[0037] Figure 6 This is a plan view of the release impact hammer of the detection device of the rotary adjustable scheme in the embodiment of the present invention under a kinetic energy state of 5.5J;

[0038] Figure 7 This is a plan view of the detection device of the rotary adjustable scheme in this embodiment of the invention under a kinetic energy state of 4.5J;

[0039] Figure 8 This is a plan view of the detection device of the rotary adjustable scheme in this embodiment of the invention when adjusting the kinetic energy state;

[0040] Figure 9This is an isometric view of the detection device of the rotationally adjustable scheme in this embodiment of the invention without a spring;

[0041] Figure 10 This is the present invention. Figure 9 A magnified view of part A in the diagram.

[0042] In the diagram: 1-shell, 2-bottom cover, 3-adjusting sleeve, 4-impact rod, 5-guide rod, 6-impact hammer, 7-clamping mechanism, 8-gripper, 9-tension spring, 10-slider, 11-tooth groove, 12-tooth block. Detailed Implementation

[0043] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments.

[0044] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0045] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0046] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0047] In the description of this application, it should be noted that the use of terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" to indicate orientation or positional relationships is based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationships commonly used when the product is in use. These terms are used solely for the convenience of describing this application and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the use of terms such as "first" and "second" in the description of this application is only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0048] Furthermore, the use of terms such as "horizontal" and "vertical" in the description of this application does not imply that the component is required to be absolutely horizontal or suspended, but rather that it may be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but rather that it may be slightly tilted.

[0049] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0050] Example 1:

[0051] This embodiment discloses a heavy-duty rebound method testing device for concrete strength. Its core feature lies in achieving precise switching between dual kinetic energy through adjusting the sleeve 3, adapting to the testing of high-strength concrete of different strength grades. Details are as follows:

[0052] like Figure 1 As shown, the device includes a tubular housing 1. One end of the housing 1 has a first opening through which the striking rod 4 passes, and the tail end is fastened with a bottom cover 2 to form a closed second opening. Inside the housing 1, the striking rod 4, guide rod 5, impact hammer 6, clamping mechanism 7 and slider 10 are arranged sequentially along the axis. The guide rod 5 is sleeved with the striking rod 4, and one end of the guide rod 5 is detachably connected to the clamping mechanism 7. The jaws 8 on the clamping mechanism 7 are used to clamp the enlarged end of one end of the impact hammer 6. The other side of the rotatable connection of the jaws 8 has an end that uses the lever principle to rotate the jaws 8 to release the impact hammer 6 when it contacts the bottom cover 2.

[0053] A tension spring 9 is provided between the slider 10 and the impact hammer 6, which is sleeved on the outside of the guide rod 5. An adjusting sleeve 3 is sleeved at the first opening of the housing 1, and its connecting end extends into the housing 1 to cooperate with the slider 10. By adjusting the two preset installation positions of the slider 10 in the housing 1, the switching of the impact kinetic energy can be realized.

[0054] The core design logic of this device is as follows: by adjusting the sleeve 3 to drive the slider 10 to switch between two fixed installation positions, the initial tension length of the tension spring 9 is changed, thereby achieving a stable output of two levels of impact kinetic energy of 4.5J and 5.5J, and the error of the two levels of kinetic energy is controlled within ±5%, which meets the requirements of the technical specification for testing the compressive strength of concrete by rebound method.

[0055] This embodiment also discloses a testing method based on the above-mentioned equipment, applicable to the strength testing of C40-C60 high-grade concrete structures (such as bridge load-bearing beams, tunnel linings, and large foundation caps). The specific steps are as follows:

[0056] 1. Energy Gear Selection

[0057] The design documents of the concrete component to be tested are checked to determine its strength grade: if the strength grade is C40-C55, the equipment is switched to the 4.5J kinetic energy setting by adjusting sleeve 3; if the strength grade is C55-C60, the equipment is switched to the 5.5J kinetic energy setting.

[0058] 2. Survey area layout

[0059] Test zones should be evenly distributed across the measurable surface of the concrete member, avoiding areas with embedded parts, cracks, honeycombing, or other defects. The distance between adjacent test zones should not exceed 2 meters, and the distance from each test zone to the ends and edges of the member should be 0.2-0.5 meters. Each member should have at least 10 test zones, with each zone having an area not exceeding 0.04 square meters. 2 (200mm×200mm) The surface of the test area needs to be cleaned and leveled to remove laitance, oil stains and loose layers.

[0060] 3. Equipment calibration and rebound testing

[0061] Before testing, the equipment should be placed vertically on a high-strength steel anvil for calibration. The calibrated rebound value at the 4.5J setting should be within the range of 85±1, and the calibrated rebound value at the 5.5J setting should be within the range of 90±1. The equipment can only be used after passing calibration. During testing, keep the equipment axis perpendicular to the concrete testing surface, slowly apply pressure until the impact rod 4 is fully retracted, and then release it to read the rebound value. 16 rebound values ​​should be read continuously for each test area, with readings accurate to 1.

[0062] 4. Rebound value processing

[0063] For each test area, 16 rebound values ​​are screened, and the three maximum and three minimum values ​​are removed. The arithmetic mean of the remaining 10 rebound values ​​is calculated, which is the average rebound value R for that test area, accurate to 0.1. If the dispersion of the remaining rebound values ​​is large (standard deviation greater than 3.0), the Grubbs test is used to further remove outliers. After removal, the number of remaining rebound values ​​should not be less than 8; otherwise, the test area is reselected for testing.

[0064] 5. Region type determination and correction parameter selection

[0065] Based on the geographical characteristics of the area where the project to be tested is located, the region type is determined to be either a river region, a plateau region, or a plain region. The corresponding third-quarter correction parameters are retrieved, and the results are fitted based on the material properties, curing conditions, and concrete strength test data of different regions with diverse geomorphological features from January to March 2025.

[0066] 4.5J kinetic energy gear correction parameters: river area correction coefficient K1=0.98, plateau area correction coefficient K2=1.06, plain area correction coefficient K3=1.03;

[0067] 5.5J kinetic energy level correction parameters: River area correction coefficient K 1′ =1.05, Plateau region correction factor K 2′ =1.10, correction factor K for plain areas 3′ =1.07.

[0068] 6. Strength Calculation and Estimation

[0069] Multiply the average rebound value R of the test area by the corresponding correction coefficient to obtain the corrected rebound value R. c =R×K (or Rc′=R×K′), where K represents the region and kinetic energy level correction coefficient. It is a dedicated correction parameter designed for different geographical areas and different equipment kinetic energy levels in regions with diverse topographic features. It is used to correct the influence of regional environment, material properties, and curing conditions on the rebound value. It is a dimensionless coefficient. Rc is the corrected rebound value, which is the core input parameter that is finally substituted into the dedicated strength measurement curve to calculate the concrete strength.

[0070] Substitute the values ​​into the formula for the strength test curve of high-grade concrete to calculate the converted strength value of the test area. :

[0071] Formula for strength measurement curve for 4.5J gear: =0.85R c +2.3 (unit: MPa);

[0072] Formula for a strength measurement curve specific to the 5.5J gear: =0.92R c′ +1.8 (unit: MPa).

[0073] When the number of test areas for a component is no less than 10, the minimum value of the converted strength values ​​of the test areas shall be taken as the estimated value f of the concrete strength of the component, in accordance with the requirement that the guarantee rate is no less than 95%. cu,e That is, f cu,e =min(f cu,1， ,f cu,2， ,...,f cu,n (n is the number of survey areas).

[0074] Example 2:

[0075] This embodiment discloses a heavy-duty rebound method testing device for concrete strength, as detailed below:

[0076] 1. Limitations of the shell 1 and internal channel structure

[0077] The detection device in this embodiment is based on the basic structure optimization of Embodiment 1. The core is that the stepped channel design of the housing 1 is adapted to the cooperation between the adjusting sleeve 3 and the slider 10.

[0078] The tubular housing 1 has a first opening at one end through which the striking rod 4 passes, and a second opening at the other end that is closed by a bottom cover 2. The housing 1 has two channels with different inner diameters, which are distributed sequentially from the first opening to the second opening:

[0079] Near the first opening is a sleeve mounting channel with a smaller inner diameter, used to fit and fix the connecting end of the adjusting sleeve 3.

[0080] Near the second opening is the impact working channel with a larger inner diameter, which provides space for the sliding of the impact hammer 6 and the release of energy. The two channels are separated by a smoothly transitioning stepped surface, which not only ensures the coaxiality of the component installation, but also provides an axial limiting reference for the slider 10.

[0081] 2. Layout and fit of internal components

[0082] From the first opening of the housing 1 towards the second opening, the internal components are arranged and fitted in the following order:

[0083] The adjusting sleeve 3 is sleeved on the outside of the striking rod 4, with its operating end exposed outside the first opening of the housing 1 for easy gripping and operation. The connecting end extends through the first opening into the sleeve installation channel. The outer wall of the adjusting sleeve 3 and the inner wall of the sleeve installation channel adopt a fixed fit to ensure that there is no loosening after installation.

[0084] The slider 10 is set in the sleeve mounting channel, and its outer diameter is precisely matched with the inner diameter of the sleeve mounting channel. It can slide smoothly along the axis of the housing 1 without radial offset. The end of the slider 10 near the adjusting sleeve 3 is provided with a fixing structure that matches the connecting end of the adjusting sleeve 3, so that the two can be firmly connected. The end face of the slider 10 near the second opening is flat and is used to connect the tension spring 9.

[0085] The tension spring 9 is sleeved on the outside of the guide rod 5. One end of the spring is fixedly connected to the end face of the slider 10, and the other end is fixed to the end face of the impact hammer 6. The axis of the tension spring 9 is aligned with the axis of the housing 1 to ensure uniform force distribution and no off-center load during the stretching and releasing process.

[0086] The impact hammer 6 is located inside the impact channel, and its outer diameter is adapted to the inner diameter of the impact working channel. It can slide freely along the channel axis. The side of the impact hammer 6 near the second opening is fixedly connected to the clamping mechanism 7, and the other end of the clamping mechanism 7 is rigidly connected to the end of the guide rod 5.

[0087] The guide rod 5 and the striking rod 4 are coaxially sleeved. One end of the guide rod 5 is embedded inside the striking rod 4, and there is a suitable movable gap between the two to ensure that the striking rod 4 can flexibly extend and retract relative to the guide rod 5. The other end of the guide rod 5 is fixed to the clamping mechanism 7, forming a linkage structure of striking rod 4-guide rod 5-clamping mechanism 7-impact hammer 6.

[0088] The gripper 8 on the clamping mechanism 7 faces the second opening of the housing 1. After the bottom cover 2 is fastened to the second opening, its inner end face corresponds to the trigger end of the gripper 8. When the clamping mechanism 7 slides with the guide rod 5 to be close to the bottom cover 2, the gripper 8 contacts the bottom cover 2 and triggers the release action, so that the impact hammer 6 is released from the constraint.

[0089] 3. Principle for determining the dual-kinetic energy installation position

[0090] The core of setting the two mounting positions is based on the correspondence between the elastic potential energy of tension spring 9 and the impact kinetic energy, which was precisely determined through experimental calibration:

[0091] First, determine the kinetic energy of the two target impacts. Then, based on the material properties and elastic coefficient of the tension spring 9, and according to the efficiency of converting elastic potential energy into kinetic energy, calculate the initial tension length of the tension spring 9 required for the corresponding target kinetic energy.

[0092] Through multiple tests, the slider 10 was set in different fixed positions in the sleeve installation channel, and the impact kinetic energy converted after the release of the pull spring 9 at each position was measured. Two fixed positions of slider 10 that can stably reach the target value of the second level of impact kinetic energy were selected.

[0093] The two tested and verified slider 10 fixed positions are the two mounting positions inside the housing 1. Each mounting position corresponds to an adjustment sleeve 3 of a certain length specification, ensuring that after the corresponding adjustment sleeve 3 is replaced, the slider 10 can be accurately fixed in that position, and the tension spring 9 maintains the corresponding initial tension length, thereby stabilizing the output of the target impact kinetic energy.

[0094] IV. Function Implementation and Usage

[0095] The core function of the equipment is to change the fixed position of the slider 10 in the sleeve installation channel (i.e., switch the installation position) by changing the adjusting sleeve 3 with different connection end lengths, thereby adjusting the initial tension length of the tension spring 9, realizing the precise switching between two levels of impact kinetic energy, and adapting to the testing needs of high-grade concrete with different strength grades.

[0096] Kinetic energy switching process:

[0097] Before switching, first operate the pin on the side wall of the housing 1 so that the pin extends into the sleeve mounting channel and engages with the slider 10, fixing the slider 10 in the current mounting position to prevent the tension spring 9 from causing the slider 10 to move due to contraction when disassembling the adjusting sleeve 3; and because it needs to be adapted to the mounting connection of the short adjusting sleeve 3, the pin is set in the mounting position near the first opening. At this time, when replacing, the slider 10 needs to be pulled to the mounting position near the first opening to fix the limit.

[0098] Then, grasp the operating end of the adjusting sleeve 3 to release its fixed relationship with the housing 1, and remove the adjusting sleeve 3 from the first opening. At this time, the slider 10 remains stationary under the limiting action of the pin, and the tension spring 9 maintains its current tension state.

[0099] Select the adjusting sleeve 3 corresponding to the target installation position, align its connecting end with the first opening and insert it into the sleeve installation channel, so that the connecting end of the adjusting sleeve 3 and the fixing structure of the slider 10 are precisely matched and locked. Since the pin restricts rotation and fixes, the adjusting sleeve 3 and the slider 10 can be fixed by threaded connection.

[0100] Then rotate the adjusting sleeve 3 to fix it to the housing 1, ensuring that there is no relative displacement between the adjusting sleeve 3 and the housing 1. Then operate the limit pin to disengage it from the slider 10 and release the limit.

[0101] Testing and usage procedures:

[0102] Before testing, align the equipment vertically with the concrete testing surface and slowly apply pressure to push the striking rod 4. The striking rod 4 drives the guide rod 5 to slide towards the second opening of the housing 1. The guide rod 5 simultaneously drives the clamping mechanism 7 and the impact hammer 6 to move. At this time, the tension spring 9 is further stretched and stores elastic potential energy.

[0103] When the clamping mechanism 7 slides close to the bottom cover 2, the gripper 8 contacts the inner end face of the bottom cover 2, triggering the release action of the clamping mechanism 7. Under the action of the elastic potential energy of the tension spring 9, the impact hammer 6 slides quickly along the impact working channel towards the first opening.

[0104] The impact hammer 6 strikes the end of the guide rod 5, transferring kinetic energy to the guide rod 5. The guide rod 5 then drives the striking rod 4 to bounce out quickly and impact the concrete surface. Subsequently, the striking rod 4 rebounds under the reaction force of the concrete, driving the impact hammer 6 to reset, completing one rebound test. Throughout the process, the elastic potential energy released by the tension spring 9 is stably converted into the target impact kinetic energy.

[0105] Example 3:

[0106] This embodiment discloses a heavy rebound method testing device for concrete strength, referring to... Figures 1-10 Based on the basic structure of Embodiment 1, the slider 10 is precisely adjusted and fixed through a three-section channel design.

[0107] 1. Structural Foundation Description

[0108] The tubular shell 1 is made of metal and is generally a one-piece structure with two openings. The first opening allows the striking rod 4 to pass through, and the second opening is closed by the bottom cover 2.

[0109] However, in this embodiment, the housing 1 is provided with three channel sections connected in sequence along the axis, two of which are core channels with different inner diameters: the one near the first opening is the sleeve sliding channel with a smaller inner diameter, which is used to adjust the axial sliding and circumferential rotation of the sleeve 3;

[0110] A sliding channel with an inner diameter larger than the sleeve channel is also provided inside the sleeve channel to provide space for the movement and fixation of the slider 10. The two ends of this channel are two preset mounting positions. Each mounting position is equipped with a locking structure that matches the slider 10 to ensure that the slider 10 has no displacement after it is fixed. The impact working channel is located near the second opening. Its inner diameter is the same as the inner diameter of the slider 10 adjustment channel, which provides space for the sliding of the impact hammer 6. The axes of the three channels coincide to ensure the coaxiality of all components.

[0111] For ease of installation (not shown in the figure in this embodiment), a split section is provided in the middle of the sliding channel, that is, the front area of ​​the housing 1 is also set as an assembly, which can be fixedly connected by threads or bolts, so that the sliding channel can be divided into two when disassembled, which facilitates the installation of internal components.

[0112] 2. Layout and fit of internal components

[0113] The arrangement and fit of the internal components from the first opening to the second opening of the housing 1 are as follows:

[0114] Reference Figure 2 The adjusting sleeve 3 is fitted over the striking rod 4, with its operating end exposed outside the first opening. The outer wall has an anti-slip structure for easy operation. A suitable gap is left between the inner wall of the adjusting sleeve 3 and the striking rod 4 to ensure that the striking rod 4 can extend and retract freely without interfering with the adjusting sleeve 3. The connecting end of the adjusting sleeve 3 passes through the first opening and extends into the adjusting channel of the slider 10. An annular retaining ring is provided at the end of the connecting end, with an outer diameter larger than the outer diameter of the main body of the adjusting sleeve 3. The outer wall of the connecting end has a uniformly distributed transmission structure. Since the tension spring 9 always acts on the slider 10, causing it to move towards the impact hammer 6, when the retaining ring of the adjusting sleeve 3 contacts the slider 10, it can pull it towards the first opening.

[0115] The slider 10 is set in the slider 10 adjustment channel, and its outer diameter is precisely matched with the inner diameter of the slider 10 adjustment channel, so that it can slide smoothly along the channel axis. The end face of the slider 10 near the adjustment sleeve 3 is provided with a matching structure that matches the transmission structure of the adjustment sleeve 3. The two can achieve power transmission through snap-fit. The outer wall of the slider 10 is provided with a fixing structure corresponding to the mounting position locking structure. The end face of the slider 10 near the second opening is fixedly connected to the tension spring 9.

[0116] For specific cooperation structure reference Figure 10 The adjusting sleeve 3 has several toothed blocks 12 evenly spaced on the outer wall of its adjusting end, forming a spline-like structure. On the corresponding end face of the slider 10, several toothed grooves 11 are provided. When rotated to a suitable angle, the toothed blocks 12 insert into the toothed grooves 11, thus forming a transmission relationship for circumferential rotation around the axis. Furthermore, because the tension spring 9 constantly pulls the slider 10 inwards, the slider 10 remains firmly against the retaining ring during sliding. The toothed grooves 11 and toothed blocks 12 engage, allowing the adjusting sleeve 3 to rotate and engage the slider 10 with the threaded connection at the mounting position when it reaches the mounting position close to the first opening, thereby fixing the slider 10 to the housing 1.

[0117] The tension spring 9 is sleeved on the outside of the guide rod 5. One end of the tension spring 9 is fixed to the end face of the slider 10, and the other end is fixed to the end face of the impact hammer 6. The length of the tension spring 9 is adapted to the movement distance of the slider 10 between the two mounting positions, ensuring that the tension spring 9 is in an effective tension state when the slider 10 is in any mounting position.

[0118] The impact hammer 6 is located in the impact working channel. Its outer diameter is adapted to the inner diameter of the channel and can slide freely along the axis. The side of the impact hammer 6 near the second opening is fixed to the clamping mechanism 7, and the other end of the clamping mechanism 7 is fixedly connected to the end of the guide rod 5.

[0119] The guide rod 5 and the striking rod 4 are coaxially sleeved. One end of the guide rod 5 is embedded inside the striking rod 4. The gap between the two ensures flexible relative movement. The other end of the guide rod 5 is rigidly connected to the clamping mechanism 7 to form a linkage transmission.

[0120] The gripper 8 on the clamping mechanism 7 faces the bottom cover 2. After the bottom cover 2 is closed, its inner end face is opposite to the triggering part of the gripper 8. When the clamping mechanism 7 slides with the guide rod 5 to contact the bottom cover 2, the gripper 8 triggers the release of the impact hammer 6. Since the gripper 8 is fixed on the clamping mechanism 7 with the same rotating connecting shaft, it can achieve the opposite release and clamping effect relative to the clamping mechanism 7. The X-shaped triggering structure at its tail is the rotating arm on the other side of the rotating shaft. It uses the lever principle to make it release at the bottom cover 2, which is consistent with the existing technology.

[0121] It should be noted that the accompanying drawings are only for illustrating the structural relationships. The tightness of the assembly and the dimensions are not limited to the style shown in the drawings. Furthermore, the dimensions of the drawings themselves may not absolutely meet the assembly and installation requirements, but they are sufficient to show the connection relationship between the components. For example, the threads are not shown in the drawings at the two mounting positions of the sliding channel and on the annular slider 10 structure. The textual description of this embodiment shall prevail.

[0122] 3. Principle for determining the dual-kinetic energy installation position

[0123] The determination of the two mounting positions is based on the correspondence between the elastic properties of tension spring 9 and the impact kinetic energy, and is achieved through experimental calibration:

[0124] By determining the two target impact kinetic energies, and combining the elastic coefficient and kinetic energy conversion efficiency of the tension spring 9, the range of the initial tension length of the tension spring 9 required to achieve the target kinetic energy is calculated.

[0125] Multiple candidate positions are set in the slider 10 adjustment channel. Multiple impact tests are performed on each candidate position. The impact kinetic energy of each test is measured, the data is recorded, and the stability is analyzed.

[0126] Two candidate positions are selected where the impact kinetic energy stably reaches the two target values ​​and the data dispersion meets the requirements. These two positions are then determined as the final installation positions. At the same time, corresponding locking structures are set at the installation positions to ensure that the initial tension length of the tension spring 9 remains constant after the slider 10 is fixed at the position, thereby ensuring the consistency of the impact kinetic energy.

[0127] 4. Functionality and Usage

[0128] Core functions of the equipment:

[0129] The slider 10 is moved by adjusting the axial sliding of the sleeve 3, and the slider 10 is fixed to the installation position by adjusting the circumferential rotation of the sleeve 3. Then, the initial tension length of the tension spring 9 is switched to achieve stable output of two levels of impact kinetic energy, which meets the requirements of accurate testing of high-grade concrete.

[0130] Kinetic energy switching process:

[0131] When switching kinetic energy, first hold the operating end of the adjusting sleeve 3 and rotate the adjusting sleeve 3 circumferentially to release its locking relationship with the outer wall of the first opening of the housing 1, so that the adjusting sleeve 3 can move axially along the sleeve sliding channel.

[0132] Pull the adjusting sleeve 3 to the outside or inside of the housing 1. The adjusting sleeve 3 abuts against the end face of the slider 10 through the retaining ring at the end, driving the slider 10 to move along the slider 10 adjustment channel to the target installation position. During the movement, ensure that the slider 10 does not get stuck with the inner wall of the channel.

[0133] When the slider 10 moves to the target installation position, the adjusting sleeve 3 is rotated, and the transmission structure at its connecting end engages with the matching structure of the slider 10, causing the slider 10 to rotate synchronously. This allows the fixing structure on the outer wall of the slider 10 to precisely match the locking structure of the installation position, thus achieving a firm fixation of the slider 10 at the installation position.

[0134] Continue to rotate the adjusting sleeve 3 until its operating end is locked again to the outer wall of the first opening of the housing 1. At this time, the adjusting sleeve 3 is disengaged from the transmission structure of the slider 10, and the adjusting sleeve 3 only serves as a protection and guide.

[0135] Testing and usage procedures:

[0136] During testing, the striking rod 4 of the device is aligned with the concrete testing surface, and vertical pressure is applied to push the striking rod 4. The striking rod 4 drives the guide rod 5 to slide towards the second opening of the housing 1. The guide rod 5 drives the clamping mechanism 7 and the impact hammer 6 to move synchronously, and the tension spring 9 is stretched and stores elastic potential energy.

[0137] When the clamping mechanism 7 moves to contact the bottom cover 2, the gripper 8 triggers the release action. Under the tension of the tension spring 9, the impact hammer 6 slides quickly along the impact working channel towards the first opening. The impact hammer 6 strikes the end of the guide rod 5 and transmits kinetic energy.

[0138] The guide rod 5 transmits kinetic energy to the striking rod 4, which quickly ejects and impacts the concrete surface. Then, under the reaction force of the concrete, it rebounds, driving the impact hammer 6 and the guide rod 5 to reset, completing one rebound test. Throughout the process, the elastic potential energy released by the tension spring 9 is stably converted into the preset impact kinetic energy.

[0139] Example 4:

[0140] This embodiment discloses a detection method based on the detection equipment of the above embodiments, as detailed below:

[0141] 1. Core Methodological Basis

[0142] The detection method in this embodiment is based on the regional characteristics of high-grade concrete in areas with diverse landforms. It combines a dual-energy detection device with a three-dimensional detection logic that includes energy level adaptation, regional correction, and a dedicated strength measurement curve. The dedicated strength measurement curve is obtained by fitting experimental data from three major regions—river channels, plateaus, and plains—in areas with diverse landforms from January to March 2025. The core formula is a linear regression formula.

[0143] =aR c +b;

[0144] in R is the converted value for concrete strength. c The rebound value is the corrected value, and a and b are region-specific regression coefficients.

[0145] 2. Experimental Data Basis

[0146] The experiment selected representative projects in river areas (riverside projects), plateau areas, and plain areas (ordinary expressway projects) with diverse geomorphological features. Concrete of four strength grades (C40, C50, C55, and C60) was mixed using local materials. Standard specimens were prepared at five ages: 14d, 28d, 60d, 90d, and 180d. For each strength grade, 40 sets of specimens were prepared per age (30 sets for C60). Rebound tests were conducted using kinetic energy of 4.5J and 5.5J, respectively, and compressive strength tests were performed simultaneously. A total of 1,500 sets of valid data were collected, and the specific strength curve parameters for each region were obtained through regression analysis.

[0147] 3. Detailed testing and calculation process

[0148] (1) Preliminary preparation

[0149] 1) Equipment calibration: Calibrate on a high-strength steel anvil before testing, using the 4.5J setting to calibrate the springback value R. s =85±1, 5.5J gear R s =90±1. If the calibration fails, the equipment needs to be adjusted and recalibrated.

[0150] 2) Project information collection: Determine the strength grade of the concrete to be tested, the pouring date (determine the age), the project location (river / plateau / plain), and the type of local materials (aggregate source, cement grade), etc.

[0151] (2) Survey area layout and data acquisition

[0152] The test area was arranged according to the requirements of Example 1. Sixteen rebound values ​​were collected in each test area. After removing the three maximum values ​​and three minimum values, the average rebound value R of the test area was calculated.

[0153] Example: For a C55 concrete component in a plain area, 16 rebound values ​​were obtained: 82, 83, 85, 84, 86, 85, 87, 85, 84, 83, 86, 88, 85, 84, 82, 87. After removing the maximum values ​​(88, 87, 87) and the minimum values ​​(82, 82, 83), the remaining 10 values ​​are: 83, 85, 84, 86, 85, 85, 84, 83, 86, 84. The average rebound value is as follows:

[0154] R=(83+85+84+86+85+85+84+83+86+84) / 10=84.5

[0155] (3) Springback value correction

[0156] The correction factor is selected based on the region type. For plains areas, the correction factor K=1.03 for 4.5J gear. The rebound value after correction is as follows:

[0157] R c =R×K=84.5×1.03=87.035≈87.0;

[0158] (4) Strength conversion

[0159] Retrieve the formula for the 4.5J speed-specific intensity measurement curve in plain areas: =0.87R c +1.9, substitute into R c =87.0, calculated to be 77.59MPa.

[0160] (5) Intensity estimation in multiple test areas

[0161] If the component has a total of 12 test zones, the strength conversion values ​​for each test zone are: 77.59MPa, 78.23MPa, 76.91MPa, 79.05MPa, 77.82MPa, 78.56MPa, 76.34MPa, 77.18MPa, 78.92MPa, 79.31MPa, 77.65MPa, and 78.17MPa. Based on the requirement of a 95% guarantee rate, the minimum value of 76.34MPa is taken as the estimated strength value of the component.

[0162] (6) Example of 5.5J gear calculation

[0163] For a C60 concrete component in a certain river area, the average rebound value R = 89.2. The correction coefficient K′ for the 5.5J stop in the river area is 1.05. The corrected rebound value R is... c′ =89.2×1.05=93.66; Formula for a special intensity measurement curve for the 5.5J range in river areas: =0.95R c′ +1.2, substituting, we get =0.95×93.66+1.2=89.177MPa≈89.2MPa.

[0164] 4. Complete parameters of dedicated intensity measurement curve

[0165] Table 1. Predicted curves under the 4.5J kinetic energy mode

[0166]

[0167] Region 1: Samples from most river channels; Region 2: Samples from most plateau regions; Region 3: Samples from most plain regions.

[0168] Table 2. Predicted curves under the 5.5J kinetic energy mode.

[0169]

[0170] Region 1: Samples from most river channels; Region 2: Samples from most plateau regions; Region 3: Samples from most plain regions.

[0171] It should be noted that the reference for the strength of this concrete structure is strongly related to the region and the material itself. The fitting curves provided in this embodiment for three different types of geological conditions in areas with diverse landforms were obtained by on-site testing of raw materials and trial blocks.

[0172] This invention is not limited to the optional embodiments described above, and anyone can derive other various forms of products based on the inspiration of this invention. The specific embodiments described above should not be construed as limiting the scope of protection of this invention; the scope of protection of this invention should be determined by the claims, and the specification can be used to interpret the claims.

Claims

1. A heavy-duty rebound concrete strength testing device, employing a dual-energy mode for concrete strength testing, characterized in that: It includes a tubular housing (1), one end of which has a first opening for the internal striking rod (4) to pass through, and a second opening at the tail that is fastened and fixed by a bottom cover (2); Inside the housing (1), there is also an impact hammer (6) and a clamping mechanism (7) that slide along the axis of the housing (1). The clamping mechanism (7) is connected to the end of the guide rod (5) which is located inside the striking rod (4) and sleeved with the striking rod (4), and drives the impact hammer (6) to slide. The clamping mechanism (7) is provided with a claw (8) that releases the impact hammer (6) by contacting the bottom cover (2). The housing (1) is also provided with a slider (10), and a tension spring (9) sleeved on the outside of the guide rod (5) is provided between the slider (10) and the impact hammer (6). The housing (1) has at least two mounting positions for limiting the tension spring (9) to the corresponding kinetic energy length of the slider (10). The first opening of the housing (1) is provided with an adjusting sleeve (3) sleeved outside the striking rod (4). The adjusting sleeve (3) has an operating end outside the housing (1) and a connecting end that extends into the housing (1) from the first opening and cooperates with the slider (10) to adjust the mounting position of the slider (10). The first opening to the second opening of the housing (1) contains a sleeve channel for the sliding limit of the adjusting sleeve (3) and an impact channel for the sliding limit of the impact hammer (6). The sleeve channel is provided with an adjusting channel whose cross-sectional radius is larger than that of the sleeve channel. The slider (10) slides along the axis of the housing (1) in the adjusting channel. The two ends of the adjusting channel are two mounting positions, and each mounting position is provided with an internal thread. The connecting end of the adjusting sleeve (3) is a tubular structure located between the sleeve channel and the striking rod (4). The end of the connecting end that extends into the housing (1) has a corresponding slider (10) and a retaining ring that pulls the slider (10) toward the first opening to limit its movement. A toothed block (12) is provided on the outer wall of the connecting end near the retaining ring. The slider (10) has a toothed groove (11) corresponding to the toothed block (12). The adjusting sleeve (3) is rotated by the engagement of the toothed block (12) and the toothed groove (11) to fix / release the slider (10) to the mounting position. Pulling the adjusting sleeve (3) causes the retaining ring to abut against the slider (10) to overcome the pulling force of the tension spring (9) toward the second opening and adjust the position of the slider (10).

2. The heavy-duty rebound test equipment for concrete strength according to claim 1, characterized in that: The housing (1) has an external thread on the outer wall of the first opening, and the operating end of the adjusting sleeve (3) has an internal thread that mates with the external thread. When the internal thread of the adjusting sleeve (3) contacts the external thread of the housing (1), the tooth groove (11) and the tooth block (12) disengage and the slider (10) is fixed on the mounting position of the tension spring (9) with the shortest initial length.

3. A detection method, characterized in that: The concrete strength heavy rebound method testing equipment described in claim 1 or 2 is used for concrete structure strength testing, as follows: Step 1: Determine the design strength grade range of the high-grade concrete to be tested. If the strength grade is C40~C55, switch the testing equipment to the 4.5J kinetic energy setting by adjusting the sleeve (3); if the strength grade is C55~C60, switch to the 5.5J kinetic energy setting. Step 2: Arrange test areas on the concrete component to be tested. The test areas should be evenly distributed on the measurable surface of the component, avoiding embedded parts and defective areas. The distance between adjacent test areas should not exceed 2m, and the distance between the test area and the end of the component should be 0.2-0.5m. The number of test areas on a single component should not be less than 10, and the area of ​​each test area should not exceed 0.04m². 2 ; Step 3: Use the testing equipment to perform rebound testing on each test area, ensuring that the equipment axis is perpendicular to the concrete test surface. Read 16 rebound values ​​for each test area, with the readings accurate to 1. Step 4: Remove the 3 maximum and 3 minimum values ​​in each test area, and calculate the average rebound value of the remaining 10 rebound values, accurate to 0.

1. Step 5: Determine the type of the area to be detected, which is a river, plateau, or plain, and retrieve the third-quarter correction value parameters corresponding to the kinetic energy level and area type; Step 6: Substitute the average rebound value and corresponding correction value parameters of the test area into the high-grade concrete strength test curve to calculate the concrete strength conversion value of each test area. Then, determine the estimated value of the concrete strength of the component according to the number of test areas. When the number of test areas is not less than 10, calculate the estimated strength according to the requirement that the guarantee rate is not less than 95%.

4. The detection method according to claim 3, characterized in that: When the testing equipment is set to 4.5J kinetic energy, the corresponding correction parameters for the third quarter are as follows: correction coefficient for river areas is 0.95-1.05, correction coefficient for plateau areas is 1.02-1.12, and correction coefficient for plain areas is 0.98-1.

08. The correction parameters are obtained by fitting the material characteristics, curing conditions, and concrete strength test data of the corresponding areas in the third quarter.

5. The detection method according to claim 3, characterized in that: When the testing equipment uses the 5.5J kinetic energy setting, the corresponding correction values ​​for the third quarter are as follows: the correction coefficient for river areas is 1.00-1.10, the correction coefficient for plateau areas is 1.05-1.15, and the correction coefficient for plain areas is 1.02-1.

12. The correction values ​​and the parameters for the 4.5J setting are calibrated synchronously based on the same set of regional test data.

6. The detection method according to claim 3, characterized in that: Before the rebound test in step 3, the testing equipment needs to be calibrated on a standard steel anvil. The calibrated rebound value meets the equipment calibration requirements. In step 4, if the standard deviation of the average rebound value dispersion in the test area is greater than 3.0, the Grubbs test is used to remove outliers. After removal, the number of remaining rebound values ​​should not be less than 8. Otherwise, the test area is reselected for testing.

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