Concrete strength heavy-duty rebound method detection equipment and method

Abstract

The invention belongs to the technical field of nondestructive detection of concrete strength, and discloses equipment and a method for detecting the concrete strength by a heavy rebound method. The equipment comprises a tubular shell, a striking rod, a guide rod, an impact hammer, a sliding block, a tension spring and an adjusting sleeve, the adjusting sleeve drives the sliding block to switch two preset mounting positions in the shell, and 4.5 J and 5.5 J double-kinetic-energy stable output is achieved; the method is combined with double kinetic energy characteristics of equipment, and concrete strength is converted by adopting exclusive strength measurement curves of riverways, plains and plateaus in diverse landform characteristic regions. The problems that existing equipment is insufficient in kinetic energy and cannot detect high-grade concrete are solved, coring is not needed to damage the structure, the detection error meets the national standard requirement, the device adapts to C40-C60 concrete, the quality detection requirement of large-load projects such as bridges and tunnels is met, and the detection precision and efficiency are remarkably improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of strength detection, and particularly relates to a concrete strength heavy rebound method detection device and method. BACKGROUND

[0002] The rebound hammer is a core nondestructive testing equipment for detecting the compressive strength of concrete in the engineering field. Its working principle is based on the positive correlation between the surface hardness of concrete and the internal compressive strength. A heavy hammer is driven by a spring inside the equipment to impact a striking rod on the surface of the concrete with a preset kinetic energy. The rebound value generated after the striking rod rebounds can be quickly obtained by conversion through the strength curve. The equipment is widely used in the quality detection of concrete structures such as buildings, bridges, tunnels and foundations due to its convenient operation and nondestructive integrity, and is a key tool for engineering construction acceptance and quality supervision.

[0003] However, with the wide application of high-grade concrete (C50 and above, corresponding to a compressive strength of ≥59.9 MPa) in large load engineering (such as bridge bearing structures, tunnel lining and large foundations), the existing rebound hammer and detection method gradually exposes technical defects that are difficult to overcome: On the one hand, the nominal kinetic energy of the existing rebound hammer is only 2.2 J. In the face of 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 striking rod, large dispersion of the rebound value, detection error exceeding the national standard allowable range (≤10%), and inability to reflect the true strength of the concrete. Ultimately, it needs to rely on core verification, which not only destroys the structural integrity but also reduces the detection efficiency; On the other hand, the existing equipment lacks a stable and reliable kinetic energy adjustment structure. If a conventional stepless adjustment screw thread extension design is used, the threads may slip and loosen after a long time of impact. If a detachable component adjustment is used, the spring may lose its limit and shrink out of control, making it impossible to reconnect. It is difficult to achieve precise kinetic energy switching for different strength high-grade concrete. At the same time, the existing detection method uses a universal strength curve without considering the differences in different regional materials, climate and curing conditions, further amplifying the detection deviation and failing to meet the precise detection needs of high-grade concrete. SUMMARY

[0004] To solve the problems existing in the prior art, the application provides a concrete strength heavy rebound method detection device and method, which adjusts and adapts to more scene use through a double kinetic energy device, and provides more accurate detection reference calculation through the determination of correction values for various topographic features in different regions.

[0005] The technical solution adopted by the application is as follows: The first aspect, the present application provides a kind of concrete strength heavy rebound method detection equipment, using double kinetic energy mode carries out concrete strength detection, including the shell of tubular, the first opening of shell one end has for inside knock rod to go out, and tail portion is fixed by the second opening of bottom cover buckle; The shell is also provided with an impact hammer and a clamping mechanism sliding along the axis of the shell, the clamping mechanism is connected to the impact hammer by a guide rod provided inside the knock rod and sleeved with the knock rod, and the clamping mechanism is provided with a jaw for releasing the impact hammer by contacting the bottom cover; The shell is also provided with a sliding block, and a tension spring is provided outside the guide rod between the sliding block and the impact hammer; The shell has at least two mounting positions for limiting the length of the tension spring, and the first opening of the shell is provided with an adjusting sleeve sleeved outside the knock rod, the adjusting sleeve has an operating end outside the shell and a connecting end extending into the shell from the first opening and cooperating with the sliding block to adjust the mounting position of the sliding block.

[0006] In combination with the first aspect, the present application provides a first embodiment of the first aspect, the adjusting sleeve is threadedly connected with the shell, and the position of the sliding block in the two mounting positions in the shell is adjusted by replacing the adjusting sleeve with different lengths of the connecting end.

[0007] In combination with the first embodiment of the first aspect, the present application provides a second embodiment of the first aspect, the adjusting sleeve is threadedly connected with the sliding block, and the shell is further provided with a latch having an operating end outside the shell, the latch is inserted into the sliding block in the mounting position corresponding to the longest initial length of the tension spring to achieve limiting and fixing, and the adjusting sleeve is replaced when the latch fixes the sliding block, and the adjusting sleeve and the shell are threadedly fixed in the same direction when the adjusting sleeve is threadedly fixed with the sliding block.

[0008] In combination with the first aspect, the present application provides a third embodiment of the first aspect, the channel from the first opening to the second opening of the shell is respectively a sleeve channel for limiting the sliding of the adjusting sleeve and an impact channel for limiting the sliding of the impact hammer, the sleeve channel is provided with an adjusting channel having a larger cross-sectional radius than the sleeve channel, the sliding block is limited to slide along the axis of the shell in the adjusting channel, and the two ends of the adjusting channel are respectively two mounting positions, each mounting position is provided with an internal thread.

[0009] In combination with the third embodiment of the first aspect, the present application provides a fourth embodiment of the first aspect, the connecting end of the adjusting sleeve is a tubular structure between the sleeve channel and the knock rod, the end of the connecting end extending into the shell is provided with a stop ring corresponding to the sliding block and limiting the sliding of the sliding block towards the first opening, the outer wall of the connecting end close to the stop ring is provided with a tooth block, and the sliding block is provided with a tooth groove corresponding to the tooth block. The tooth block and the tooth groove are connected and matched to rotate the adjusting sleeve, the sliding block and the mounting position are fixed / released, the adjusting sleeve is pulled, the sliding block is limited by the blocking ring, the sliding block position is adjusted by overcoming the pulling force of the tension spring to the second opening.

[0010] With reference to the fourth implementation manner of the first aspect, the present application provides a fifth implementation manner of the first aspect, the shell is provided with external threads on the outer wall of the first opening, the operating end of the adjusting sleeve is provided with internal threads matched with the external threads, when the internal threads of the adjusting sleeve are in contact with the external threads of the shell, the tooth groove is out of contact with the tooth block and the sliding block is fixed on the mounting position with the shortest initial length of the tension spring.

[0011] In the second aspect, the present application provides a detection method, which uses the heavy-type rebound method detection equipment for concrete strength detection of the concrete structure of roads and bridges in areas with various topographic features, and specifically as follows: Step 1: determine the design strength grade range of the high-grade concrete to be detected, if the strength grade is C40~C55, switch the detection equipment to the 4.5J kinetic energy position through the adjusting sleeve; if the strength grade is C55~C60, switch to the 5.5J kinetic energy position; Step 2: arrange the measurement area on the concrete member to be detected, the measurement area is evenly distributed on the measurable surface of the member, avoiding the embedded parts and defect parts, the distance between adjacent measurement areas is not greater than 2m, the distance between the measurement area and the end of the member is 0.2-0.5m, the number of measurement areas of a single member is not less than 10, and the area of the measurement area is not greater than 0.04m2; Step 3: use the detection equipment to perform rebound detection on each measurement area, ensure that the equipment axis is perpendicular to the concrete detection surface, read 16 rebound values for each measurement area, and the reading is accurate to 1; Step 4: eliminate 3 maximum values and 3 minimum values in each measurement area, calculate the average rebound value of the remaining 10 rebound values in the measurement area, and the accuracy is 0.1; Step 5: determine the type of the area to be detected as one of a river, a plateau or a plain, and retrieve the three-quarter correction value parameters corresponding to the kinetic energy position and the area type; Step 6: substitute the average rebound value of the measurement area and the corresponding correction value parameter into the high-grade concrete special strength measurement curve to calculate the concrete strength conversion value of each measurement area, and then determine the concrete strength presumption value of the member according to the number of measurement areas, when the number of measurement areas is not less than 10, the presumption strength is calculated according to the requirement that the guarantee rate is not less than 95%.

[0012] In combination with the second aspect, the application provides a first implementation of the second aspect, when the detection device adopts a 4.5J kinetic energy gear, the corresponding third quarter correction value parameter is that the correction coefficient of the river area is 0.95-1.05, the correction coefficient of the plateau area is 1.02-1.12, and the correction coefficient of the plain area is 0.98-1.08, and the correction value parameter is obtained based on the ground material characteristics, maintenance conditions and concrete strength test data of the corresponding area in the third quarter.

[0013] In combination with the second aspect, the application provides a second implementation of the second aspect, when the detection device adopts a 5.5J kinetic energy gear, the corresponding third quarter correction value parameter is that the correction coefficient of the river area is 1.00-1.10, the correction coefficient of the plateau area is 1.05-1.15, and the correction coefficient of the plain area is 1.02-1.12, and the correction value parameter is calibrated based on the same group of area test data as the 4.5J gear parameter.

[0014] In combination with the second aspect, the application provides a third implementation of the second aspect, before the rebound detection in the step 3, the detection device needs to be calibrated on a standard steel anvil, and the calibrated rebound value meets the device calibration requirement; in the step 4, if the average rebound value of the measurement area has a large discreteness, the Grubbs test method is used to eliminate the abnormal value, and the number of the remaining rebound values is not less than 8 after the elimination, otherwise the measurement area is reselected for detection.

[0015] The application has the following beneficial effects: (1) The device of the application realizes stable and accurate switching of 4.5J and 5.5J double kinetic energy through the cooperative design of the front end adjusting sleeve and the slider, and both schemes avoid the defects of the traditional adjusting structure: scheme one controls the pin limit slider through the button, when the adjusting sleeve with different depth is replaced, the stretch spring contraction is avoided, the operation is simple and efficient, and the kinetic energy switching can be completed without complex tools; scheme two uses the combination structure of the spline transmission and the double thread fixation, so that the slider is fixed rigidly with the rebound instrument shell after being adjusted in place, the adjusting sleeve only bears the sliding sleeve function and does not bear the impact load, the problems of wire slipping and loosening in long-term use are solved, and the stability of kinetic energy output is ensured. (2) The double kinetic energy design of the application accurately adapts to high-grade concrete of different strength grades, the 4.5J gear can efficiently detect C40-C55 concrete, and the 5.5J gear can effectively break through the hardness barrier of C55-C60 concrete, so that the rebound value and the actual strength have significantly improved correlation, the detection error is controlled within 10%, the problem of inaccurate measurement caused by insufficient kinetic energy of the existing device is solved, and nondestructive testing is realized without core verification, which protects the integrity of the engineering structure. (3) The application establishes special strength measurement curves for different regions and different ground materials in areas with various landform features, realizes double-precision detection of kinetic energy adaptation and curve specificity, avoids the problem of soil and water not being suitable for general curves in regional engineering, makes the detection results more in line with engineering practice, and provides a reliable basis for quality control of large-load high-grade concrete structures such as bridges, tunnels, and foundations. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is the initial isometric view of the detection equipment in the rotating adjustable scheme in the embodiment of the application under the condition of 5.5J kinetic energy; Figure 2 is the initial plan view of the detection equipment in the rotating adjustable scheme in the embodiment of the application under the condition of 5.5J kinetic energy; Figure 3 is the isometric view of the inward abutment of the detection equipment in the rotating adjustable scheme in the embodiment of the application under the condition of 5.5J kinetic energy; Figure 4 is the plan view of the inward abutment of the detection equipment in the rotating adjustable scheme in the embodiment of the application under the condition of 5.5J kinetic energy; Figure 5 is the isometric view of the release of the impact hammer of the detection equipment in the rotating adjustable scheme in the embodiment of the application under the condition of 5.5J kinetic energy; Figure 6 is the plan view of the release of the impact hammer of the detection equipment in the rotating adjustable scheme in the embodiment of the application under the condition of 5.5J kinetic energy; Figure 7 is the plan view of the detection equipment in the rotating adjustable scheme in the embodiment of the application under the condition of 4.5J kinetic energy; Figure 8 is the plan view of the detection equipment in the rotating adjustable scheme in the embodiment of the application when adjusting the kinetic energy state; Figure 9 is the isometric view of the detection equipment in the rotating adjustable scheme in the embodiment of the application without a spring; Figure 10 is the A partial enlarged view in the embodiment of the application. Figure 9

[0017] In the figure: 1 - shell, 2 - bottom cover, 3 - adjusting sleeve, 4 - striking lever, 5 - guide rod, 6 - impact hammer, 7 - clamping mechanism, 8 - clamping jaw, 9 - tension spring, 10 - sliding block, 11 - tooth groove, 12 - tooth block. DETAILED DESCRIPTION

[0018] The application will be further explained below in combination with the drawings and specific embodiments.

[0019] ​To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the following will be combined with the accompanying drawings to make a clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the accompanying drawings can be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without making creative efforts fall within the scope of protection of the present application.

[0021] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0022] In the description of the present application, it should be noted that if the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship when the product of the present application is usually placed, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, if the terms "first", "second" and the like appear in the description of the present application, they are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0023] In addition, if the terms "horizontal", "vertical" and the like appear in the description of the present application, they do not mean that the component must be absolutely horizontal or vertical, but can be slightly inclined. For example, "horizontal" only means that its direction is relatively more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0024] In the description of the present application, it should also be noted that unless otherwise explicitly specified and limited, if the terms "set", "mount", "connected", "connected" appear, they should be understood in a broad sense, for example, can be fixedly connected, can be detachably connected, or integrally connected; can be mechanically connected, can be electrically connected; can be directly connected, can be indirectly connected through an intermediate medium, and can be connected inside two elements. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0025] Embodiment 1: 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: 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.

[0026] 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.

[0027] 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.

[0028] 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: 1. Power Gear Selection 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 level by adjusting sleeve 3; if the strength grade is C55-C60, the equipment is switched to the 5.5J kinetic energy level.

[0029] 2. Survey area layout 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.

[0030] 3. Equipment calibration and rebound testing Before testing, the equipment should be vertically placed on a high-strength steel anvil for calibration. The calibration rebound value at the 4.5J setting should be within the range of 85±1, and the calibration 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.

[0031] 4. Rebound value processing 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.

[0032] 5. Region type determination and correction parameter selection 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 characteristics from January to March 2025. 4.5J kinetic energy level correction parameters: river area correction coefficient K1=0.98, plateau area correction coefficient K2=1.06, plain area correction coefficient K3=1.03; 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.

[0033] 6. Strength Calculation and Estimation 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 energy level correction coefficient. It is a dedicated correction parameter designed for different geographical regions and different equipment energy levels in areas 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.

[0034] 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. : Formula for the strength measurement curve specific to the 4.5J gear setting: =0.85R c +2.3 (unit: MPa); Formula for a specific strength measurement curve for the 5.5J gear setting: =0.92R c′ +1.8 (unit: MPa).

[0035] When the number of test areas for a component is no less than 10, the minimum value of the converted strength value of the test areas shall be taken as the estimated value of the concrete strength of the component, in accordance with the requirement that the guarantee rate is no less than 95%. f cu,e ,Right now f cu,e =min( f cu,1， f cu,2 ... f cu,n (n is the number of survey areas).

[0036] Example 2: This embodiment discloses a heavy-duty rebound method testing device for concrete strength, as detailed below: 1. Limitations of the shell 1 and internal channel structure 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.

[0037] 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: 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. 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.

[0038] 2. Layout and fit of internal components From the first opening of the housing 1 towards the second opening, the internal components are arranged and fitted in the following order: 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. 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 3. Principle for determining the dual-kinetic energy installation position 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: 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.

[0044] 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.

[0045] 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.

[0046] IV. Function Implementation and Usage 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. Kinetic energy switching process: 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] Testing and usage procedures: 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. 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. 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.

[0051] Example 3: 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.

[0052] 1. Structural Foundation Description 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.

[0053] However, in this embodiment, the housing 1 is provided with three channels 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; 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.

[0054] 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.

[0055] 2. Layout and fit of internal components The arrangement and fit of the internal components from the first opening to the second opening of the housing 1 are as follows: Reference Figure 2The 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 3. Principle for determining the dual-kinetic energy installation position 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: 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. 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. 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.

[0064] 4. Functionality and Usage Core functions of the equipment: 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.

[0065] Kinetic energy switching process: 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] Testing and usage procedures: 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. 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. 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.

[0070] Example 4: This embodiment discloses a detection method based on the detection equipment of the above embodiments, as detailed below: 1. Core Methodological Basis 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. = aR c +b； in This is a converted value for concrete strength. R cThe corrected rebound value, a , b These are region-specific regression coefficients.

[0071] 2. Experimental Data Basis 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.

[0072] 3. Detailed testing and calculation process (1) Preliminary preparation 1) Equipment calibration: Calibrate on a high-strength steel anvil before testing, calibrating the rebound value R at the 4.5J setting. s =85±1, 5.5J gear R s =90±1. If the calibration fails, the equipment needs to be adjusted and recalibrated.

[0073] 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.

[0074] (2) Survey area layout and data acquisition 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.

[0075] 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: R=(83+85+84+86+85+85+84+83+86+84) / 10=84.5 (3) Springback value correction The correction factor is selected based on the region type. For plains areas, the correction factor K=1.03 for the 4.5J gear. The rebound value after correction is as follows: R c=R× K =84.5 × 1.03 = 87.035 ≈ 87.0; (4) Strength conversion Retrieve the formula for the 4.5J intensity measurement curve for plain areas: =0.87 R c +1.9, substitute R c =87.0, calculated to be 77.59MPa.

[0076] (5) Intensity estimation in multiple test areas 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.

[0077] (6) Example of 5.5J gear calculation For a C60 concrete component in a certain river area, the average rebound value R in the test area is 89.2. The correction factor for the 5.5J level in the river area is... K′ =1.05, corrected rebound value R c′ =89.2×1.05=93.66; Formula for the special intensity measurement curve of 5.5J range in river area: =0.95 R c′ +1.2, substituting, we get =0.95×93.66+1.2=89.177MPa≈89.2MPa.

[0078] 4. Complete parameters of dedicated intensity measurement curve Table 1. Predicted curves under the 4.5J kinetic energy mode Region 1: Samples from most river channels; Region 2: Samples from most plateau regions; Region 3: Samples from most plain regions.

[0079] Table 2. Predicted curves under the 5.5J kinetic energy mode.

[0080] Region 1: Samples from most river channels; Region 2: Samples from most plateau regions; Region 3: Samples from most plain regions.

[0081] 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 proposed 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.

[0082] This invention is not limited to the optional embodiments described above, and anyone can derive other various forms of products based on the teachings 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 housing (1) has an adjusting sleeve (3) sleeved outside the striking rod (4) at the first opening. 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).

2. The heavy-duty rebound test equipment for concrete strength according to claim 1, characterized in that: The adjusting sleeve (3) is threadedly connected to the housing (1). By changing the adjusting sleeve (3) with different lengths of the connecting end, the position of the slider (10) in the two mounting positions inside the housing (1) can be adjusted.

3. The heavy-duty rebound method testing equipment for concrete strength according to claim 2, characterized in that: The adjusting sleeve (3) is threadedly engaged with the slider (10). The housing (1) is also provided with a pin with an operating end on the outside of the housing (1). The pin is inserted into the housing (1) into the slider (10) at the installation position corresponding to the longest initial length of the tension spring (9) to achieve limiting and fixing. When the pin fixes the slider (10), the adjusting sleeve (3) is replaced. When the adjusting sleeve (3) and the slider (10) are threadedly fixed, the adjusting sleeve (3) and the housing (1) are threadedly fixed in the same direction at the same time.

4. The heavy-duty rebound method testing equipment for concrete strength according to claim 1, characterized in that: 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.

5. The heavy-duty rebound method testing equipment for concrete strength according to claim 4, characterized in that: 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).

6. The heavy-duty rebound method testing equipment for concrete strength according to claim 5, 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.

7. A detection method, characterized in that: The heavy rebound concrete strength testing equipment described in any one of claims 1-6 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 level by adjusting the sleeve (3); if the strength grade is C55-C60, switch to the 5.5J kinetic energy level. 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%.

8. The detection method according to claim 7, 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.

9. The detection method according to claim 7, 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.

10. The detection method according to claim 7, 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 must meet the equipment calibration requirements. In step 4, if the average rebound value of the test area has a large dispersion, 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 should be reselected for testing.

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