A device for testing the compressive strength of solid concrete by top-pull method

Abstract

A device for testing the compressive strength of solid concrete by a top-pull method comprises a top-pull specimen in the solid concrete, on which a rectangular steel pressure head, a spherical support, a micro screw hydraulic jack and a rectangular reaction steel plate are arranged in sequence; L-shaped reaction steel pull feet that can face each other and hook the top-pull specimen are symmetrically installed on the short sides of both sides of the rectangular reaction steel plate; the rectangular reaction steel plate and the L-shaped reaction steel pull feet jointly cover the rectangular steel pressure head, the spherical support and the micro screw hydraulic jack; the longitudinal axes of the top-pull specimen, the rectangular steel pressure head, the spherical support, the micro screw hydraulic jack and the rectangular reaction steel plate are coaxial. The present invention hooks the top-pull sample in the solid concrete through the L-shaped reaction steel pulling foot, and then applies the top-pull force to the top-pull sample through the rectangular steel pressure head, the spherical support, the micro screw hydraulic jack, and the rectangular reaction steel plate until the top-pull sample is destroyed, reads the maximum top-pull force value, and infers the compressive strength of the concrete according to the conversion formula established between the compressive strength of the concrete and the top-pull force value. The design is reasonable, the practicability is strong, and the detection is accurate.

Description

Technical Field

[0001] The invention relates to a device for detecting the compressive strength of solid concrete by a top-pull method. Background Art

[0002] Compressive strength is one of the important performance parameters of concrete, which is directly related to the quality, safety and normal use of concrete components and even the entire project. Therefore, testing the compressive strength of solid concrete is a very important task.

[0003] In the prior art, there are many commonly used methods for testing the compressive strength of solid concrete, which are as follows: (1) Shear compression method. Using a concrete shear compression instrument, a pressure perpendicular to the pressure-bearing surface is applied to the right-angled surface of the concrete component, causing local shear compression damage to the right-angled surface of the concrete component, and the compressive strength of the concrete component is estimated based on the shear pressure at this time. The shortcomings of this method are: it is not suitable for testing the compressive strength of cylindrical concrete components (such as columns, concrete culverts, etc.), which affects the practicality of the test. (2) Core drilling method. Drill concrete specimens on concrete components and process them into standard core samples, and then perform compressive strength tests on pressure testing machines. The shortcomings of this test method are: since the size of the prepared standard core sample is ø100×100㎜, the degree of damage is relatively large and the repair requirements are high, which affects the practicality of the test. (3) Rebound method. Based on the relationship between the surface hardness and strength of the concrete component, the compressive strength of the concrete component is estimated. The shortcomings of this test method: It is not suitable for testing the compressive strength of cylindrical concrete components (such as columns, concrete culverts, etc.) with a curvature radius of ≤250mm, which affects the practicality of the test. (4) Ultrasonic rebound comprehensive method. The compressive strength of concrete is estimated based on the hardness of the surface of the concrete component and the ultrasonic wave velocity in the concrete component. The shortcomings of this test method: It is not suitable for testing the compressive strength of cylindrical concrete components (such as columns, concrete culverts, etc.) with a curvature radius of ≤250mm, which affects the practicality of the test. (5) Pull-out method. The compressive strength of concrete is estimated based on the pull-out force when the concrete component is destroyed within 30mm of the surface of the concrete component. The shortcomings of this test method: The test process requires complex drilling and grooving processes, and the surface must be flat. It is not suitable for testing the compressive strength of cylindrical concrete components (such as columns, concrete culverts, etc.) with a curvature radius of ≤250mm, which affects the practicality of the test. (6) Pull-off method. On the hardened concrete component, a core specimen with a diameter of 44 mm and a depth of 44 mm is drilled, and a pull-off test is performed using a device with an automatic clamping test specimen. The concrete compressive strength is estimated based on the pull-off strength value of the core specimen. The shortcomings of this detection method are: when calculating the stress of the pull-off specimen, the diameter size of the mutually perpendicular position near the fracture of the specimen needs to be measured. Due to the small diameter of the specimen, accurate measurement is difficult, which affects the detection accuracy.

[0004] In summary, the above detection methods cannot effectively detect the compressive strength of cylindrical concrete components (such as columns, concrete culverts, etc.) with a curvature radius of ≤250mm, so design improvements are needed. Summary of the invention

[0005] The present invention proposes a solid concrete compressive strength top-pull method detection device with reasonable design, strong practicality and accurate detection, and also provides a detection method using the device. The device and detection method can solve the problem that various existing solid concrete compressive strength detection methods cannot effectively detect the compressive strength of cylindrical concrete components (such as columns, concrete culverts, etc.) with a curvature radius of ≤250mm.

[0006] The technical solution adopted by the present invention is: a device for detecting the compressive strength of solid concrete by a top-pull method, comprising a top-pull specimen located in the solid concrete, on which a rectangular steel pressure head, a spherical support, a micro-screw hydraulic jack, and a rectangular reaction steel plate are arranged in sequence; L-shaped reaction steel pull feet that can face each other and hook the top-pull specimen are symmetrically installed on the short sides of both sides of the rectangular reaction steel plate; the rectangular reaction steel plate and the L-shaped reaction steel pull feet jointly cover the rectangular steel pressure head, the spherical support, and the micro-screw hydraulic jack; the longitudinal axes of the top-pull specimen, the rectangular steel pressure head, the spherical support, the micro-screw hydraulic jack, and the rectangular reaction steel plate are coaxial. The present invention hooks a top-pull specimen in solid concrete by means of an L-shaped reaction steel pull leg, and then applies a top-pull force to the top-pull specimen by means of a rectangular steel pressure head, a spherical support, a micro screw hydraulic jack, and a rectangular reaction steel plate until the top-pull specimen is destroyed, reads the maximum top-pull force value, and infers the concrete compressive strength according to a conversion formula established between the concrete compressive strength and the top-pull force value.

[0007] Furthermore, the top-pull specimen comprises a lower rectangular parallelepiped, a middle square body and an upper arched body; the lower rectangular parallelepiped has a long side of 100 mm, a short side of (78-79) mm, a high side of (11-21) mm, a lower surface connected to the solid concrete, an upper surface connected to the lower surface of the middle square body, a side surface parallel to the axial section of the solid concrete, an end surface parallel to the radial section of the solid concrete, and a longitudinal axis located in the axial section of the solid concrete; the middle square body has a side length of 100 mm, a lower surface connected to the solid concrete, and an end surface parallel to the radial section of the solid concrete. The upper surface of the lower rectangular parallelepiped is connected, and the upper surface is coincidently connected with the lower surface of the upper arched body; the lower surface of the upper arched body is coincidently connected with the upper surface of the middle square body, and the upper surface is in tight contact with the lower surface of the rectangular steel pressure head. Two positioning grooves with a width of 1mm and a depth of 1mm are symmetrically distributed in the middle of the upper surface in a direction parallel to the axial section. The side walls of the two positioning grooves are parallel to the side surfaces of the middle square body. The distance between the inner walls of the two positioning grooves is 20mm, and the vertical distance from the bottom of the groove to the lower surface of the middle square body is 30mm.

[0008] Furthermore, the rectangular steel pressure head has a long side of 100 mm, a short side of 20 mm, a thickness of (10-20) mm, an end face in the same plane as the end face of the bow, a lower surface in contact with the upper surface of the bow of the top-pull specimen, and the center of the upper surface is connected to the head of the micro-screw hydraulic jack through a spherical support.

[0009] Furthermore, a threaded sleeve perpendicular to the longitudinal axis of the micro screw hydraulic jack is connected to the circumferential side surface of the micro screw hydraulic jack, a screw is arranged in the threaded sleeve, and a T-shaped socket wrench for applying a top pulling force is installed at the end of the screw; a digital pressure gauge is also connected to the circumferential side surface of the micro screw hydraulic jack; the tail of the micro screw hydraulic jack is fixedly connected to a rectangular reaction force steel plate.

[0010] Furthermore, the rectangular reaction steel plate has a long side of (120-140) mm, a short side of 100 mm, and a thickness of (10-20) mm; three connecting circular holes for connecting with two L-shaped reaction steel pull feet are evenly drilled on the edges of the short sides on both sides.

[0011] Furthermore, the L-shaped reaction steel pull foot includes a lower cuboid and an upper cuboid; the outer side of the upper surface of the lower cuboid is fixedly connected to the lower surface of the upper cuboid; the long side of the lower cuboid is 100 mm, the high side is (10-20) mm, the side surface is parallel to the side surface of the lower cuboid of the top-pulling specimen, and the end surface is in the same plane as the end surface of the lower cuboid of the top-pulling specimen; the long side of the upper cuboid is 100 mm, the short side is (10-20) mm, the high side is > (30 + thickness of the cuboid steel pressure head + height of the spherical support + height of the micro screw hydraulic jack), the side surface is parallel to the side surface of the lower cuboid of the top-pulling specimen, and the end surface is in the same plane as the end surface of the lower cuboid of the top-pulling specimen; 3 connecting screw holes corresponding to the positions of the connecting circular holes are drilled on the upper surface of the upper cuboid, and the connecting bolts can pass through the connecting circular holes and screw into the connecting screw holes; the distance from the inner side surface of the lower cuboid to the inner side surface of the upper cuboid is 10 mm; the distance between the inner side surfaces of the two facing lower cuboids is 80 mm.

[0012] The beneficial effects of the present invention are as follows: (1) During the detection process, a detection device is used to apply a top tensile force to the concrete, and the maximum top tensile force value is measured. The concrete compressive strength is estimated based on the conversion formula established between the concrete compressive strength and the top tensile force value. The design is reasonable, the practicability is strong, and the detection is accurate. (2) The problem that the existing solid concrete compressive strength shear method, coring method, rebound method, ultrasonic-rebound method, pull-out method, and pull-off method cannot effectively detect the compressive strength of cylindrical concrete components (such as columns, concrete culverts, etc.) with a curvature radius of ≤250mm is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a front view schematic diagram of the use of the present invention.

[0014] Figure 2It is a schematic diagram of the aa cross section of the present invention.

[0015] Figure 3 It is a schematic diagram of the bb cross section of the present invention.

[0016] Figure 4 It is a schematic plan view of the auxiliary steel support of the present invention.

[0017] Figure 5 It is a schematic diagram of the operation slot cutting of the present invention.

[0018] Figure 6 It is a schematic diagram of the operation groove grinding of the present invention.

[0019] Figure 7 It is a schematic diagram of the positioning groove cutting of the present invention. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all possible alternatives, improvements and equivalents within the scope of the claims.

[0021] Reference Figure 1-7 A device for testing the compressive strength of solid concrete by a top-pull method comprises a top-pull sample 15 located in a solid concrete 13, on which a rectangular steel pressure head 16, a spherical support 10, a micro screw hydraulic jack 2, and a rectangular reaction steel plate 1 are arranged in sequence; L-shaped reaction steel pull feet 11 that can face each other and hook the top-pull sample 15 are symmetrically installed on the short sides of both sides of the rectangular reaction steel plate 1; the rectangular reaction steel plate 1 and the L-shaped reaction steel pull feet 11 jointly cover the rectangular steel pressure head 16, the spherical support 10, and the micro screw hydraulic jack 2 therein; the longitudinal axes of the top-pull sample 15, the rectangular steel pressure head 16, the spherical support 10, the micro screw hydraulic jack 2, and the rectangular reaction steel plate 1 are coaxial. The present invention hooks the top-pull sample 15 in the solid concrete 13 through the L-shaped reaction steel pull foot 11, and then applies a top-pull force to the top-pull sample 15 through the rectangular steel pressure head 16, the spherical support 10, the micro-screw hydraulic jack 2, and the rectangular reaction steel plate 1 until the top-pull sample 15 is destroyed, reads the maximum top-pull force value, and infers the concrete compressive strength according to the conversion formula established between the concrete compressive strength and the top-pull force value.

[0022] The solid concrete 13 described in this embodiment is a cylinder with a diameter of 400 mm.

[0023] The top pull test specimen 15 described in this embodiment includes a lower rectangular parallelepiped, a middle square body and an upper arched body; the lower rectangular parallelepiped has a long side of 100 mm, a short side of 78 mm, a high side of 15 mm, a lower surface connected to the solid concrete, an upper surface connected to the lower surface of the middle square body, a side surface parallel to the axial section of the cylindrical concrete, an end surface parallel to the radial section of the solid concrete, and a longitudinal axis located in the axial section of the solid concrete; the middle square body has a side length of 100 mm, a high side of 24 mm, a lower surface connected to the lower The upper surface of the rectangular parallelepiped is connected, and the upper surface coincides with the lower surface of the upper arched body; the lower surface of the upper arched body coincides with the upper surface of the middle square body, and the upper surface is in tight contact with the lower surface of the rectangular steel pressure head. Two positioning grooves with a width of 1mm and a depth of 1mm are symmetrically distributed in the middle of the upper surface parallel to the axial section. The side walls of the two positioning grooves are parallel to the side surfaces of the middle square body. The distance between the inner walls of the two positioning grooves is 20mm, and the vertical distance from the bottom of the groove to the lower surface of the middle square body is 30mm.

[0024] The rectangular steel pressure head 16 described in this embodiment has a long side of 100 mm, a short side of 20 mm, a thickness of 12 mm, an end face in the same plane as the end face of the bow-shaped body, a lower surface in contact with the upper surface of the bow-shaped body, and the center of the upper surface is connected to the head of the micro screw hydraulic jack 2 through a spherical support 10.

[0025] The micro screw hydraulic jack 2 described in this embodiment is connected to a threaded sleeve 8 perpendicular to the longitudinal axis of the micro screw hydraulic jack 2 on the circumferential side surface, and a screw 9 is arranged inside the threaded sleeve 8. The end of the screw 9 is installed with a T-shaped socket wrench 7 for applying a top pulling force; a digital pressure gauge 6 is also connected to the circumferential side surface of the micro screw hydraulic jack 2; the tail of the micro screw hydraulic jack 2 is fixedly connected to a rectangular reaction force steel plate 1.

[0026] The rectangular reaction steel plate 1 described in this embodiment has a long side of 128mm, a short side of 100mm, and a thickness of 14mm; three connecting circular holes 4 with a hole diameter of 9mm are evenly drilled on the edges of the short sides on both sides for connecting with two L-shaped reaction steel pull feet 11.

[0027] The L-shaped reaction steel pull foot 11 described in this embodiment includes a lower cuboid and an upper cuboid; the outer side of the upper surface of the lower cuboid is fixedly connected to the lower surface of the upper cuboid; the long side of the lower cuboid is 100mm, the high side is 14mm, the side surface is parallel to the side surface of the lower cuboid of the top-pull specimen, and the end surface is in the same plane as the end surface of the lower cuboid of the top-pull specimen; the long side of the upper cuboid is 100mm, the short side is 14mm, the high side is 140mm, the side surface is parallel to the side surface of the lower cuboid of the top-pull specimen, and the end surface is in the same plane as the end surface of the lower cuboid of the top-pull specimen; three connecting screw holes 5 corresponding to the position of the connecting circular hole 4 are drilled on the upper surface of the upper cuboid, with a specification of 8mm, and the M8 connecting bolt 3 can pass through the connecting circular hole 4 and screw into the connecting screw hole 5; the distance from the inner side surface of the lower cuboid to the inner side surface of the upper cuboid is 10mm; the distance between the inner side surfaces of the two facing lower cuboids is 80mm.

[0028] The detection steps of this embodiment are as follows: (1) Grasp the handle 20 on the auxiliary steel support 19 with your hand, so that the two legs 23 press the surface of the solid concrete 13; (2) Use a portable concrete cutter 17 equipped with three cutting blades 22 (with a total spacing of 30 mm), adjust the depth of the cutting blade 22, and place the concrete cutter 17 flat on the upper surface of the auxiliary steel support 19. The cutting blade 22 passes through the axial operation groove cutting opening 21, and moves axially to cut the solid concrete 13, forming an operation groove 12 with an inner wall depth of 39 mm and a width of 30 mm. Chisel out the concrete in the operation groove 12 and grind the bottom of the groove to make it flat; (3) Use a portable concrete cutter 17 equipped with three cutting blades 22 (with a total spacing of 30 mm). Adjust the depth of the cutting blade 22, and place the concrete cutter 17 flat on the upper surface of the auxiliary steel support 19. A portable concrete cutter 17 with a single cutting blade 22 is used. The depth of the cutting blade 22 is adjusted. The concrete cutter 17 is placed flat on the upper surface of the auxiliary steel bracket 19. The cutting blade 22 passes through the axial positioning groove cutting opening 18 and moves axially to cut the solid concrete 13, thereby forming a positioning groove 14 with a depth of 1 mm and a width of 1 mm. (4) An angle grinder 24 is used. The length of the extension rod 26 is adjusted. The extension rod 26 and the sintered grinding head 25 are installed. The distance between the outer edge of the extension rod 26 and the outer edge of the sintered grinding head 25 is 11 mm. The angle grinder 24 is placed flat on the upper surface of the auxiliary steel bracket 19. The extension rod 26 passes through the axial operation groove cutting opening 2 1 and close to the inner wall of the operation groove 12, axially move and grind the concrete on the inner wall of the operation groove 12; (5) Use a portable concrete cutting machine 17 equipped with a single cutting blade 22, adjust the depth of the cutting blade 22, place the concrete cutting machine 17 flat on the upper surface of the auxiliary steel bracket 19, axially move the auxiliary steel bracket 19, the cutting blade 22 passes through the radial positioning groove cutting opening 27, radially move and cut the solid concrete 13, the cutting depth is 45mm, and the top pull specimen 15 is formed; (6) Remove the auxiliary steel bracket 19, extend the two L-shaped reaction steel feet 11 into the operation groove 12 to hook the top pull specimen 15; (7) On the top pull specimen 15, Arrange the rectangular steel pressure head 16, spherical support 10, micro screw hydraulic jack 2, and rectangular reaction steel plate 1, and screw the connecting bolt 3 through the connecting circular hole 4 into the connecting screw hole 5 and tighten it; (8) Put the T-type socket wrench 7 on the end of the screw 9, and continuously and evenly rotate the screw 9 to apply force, so that the rectangular steel pressure head 16 presses against the upper surface of the top-pull specimen 15, and at the same time drives the L-shaped reaction steel pull foot 11 to move upward relative to the top-pull specimen 15 through the rectangular reaction steel plate 1 until the top-pull specimen 15 is destroyed, read the maximum top-pull force value, and estimate the concrete compressive strength based on the conversion formula established between the concrete compressive strength and the top-pull force value.

[0029] In this embodiment, the conversion formula is as follows:

[0030] Yi=AXi+B

[0031] Wherein: Yi is the converted value of the compressive strength of the i-th concrete 13 during the test (MPa); Xi is the maximum top tensile force value (N) applied to the i-th concrete 13 during the test; A and B are the regression coefficients of the regression equation.

[0032] Of course, in addition to the above formula, the conversion formula between concrete compressive strength and top tensile force value may also be other formulas and is not limited to the above formula.

Claims

1. A device for testing the compressive strength of solid concrete by top-pull method, characterized in that: It comprises a top-pull specimen located in solid concrete, on which a rectangular steel pressure head, a spherical support, a micro screw hydraulic jack, and a rectangular reaction steel plate are arranged in sequence; the top-pull specimen comprises a lower rectangular parallelepiped, a middle square body, and an upper arched body; the lower rectangular parallelepiped has a long side of 100 mm, a short side of 78 mm-79 mm, a high side of 11 mm-21 mm, a lower surface connected to the solid concrete, an upper surface connected to the lower surface of the middle square body, a side surface parallel to the axial section of the solid concrete, an end surface parallel to the radial section of the solid concrete, and a longitudinal axis located in the axial section of the solid concrete; the middle square body has a side length of 100 mm, a lower surface connected to the upper surface of the lower rectangular parallelepiped, and an upper surface coincidently connected to the lower surface of the upper arched body; the upper arched body has a side length of 100 mm, a lower surface connected to the upper surface of the lower rectangular parallelepiped, and an upper surface coincidently connected to the lower surface of the upper arched body; The lower surface of the body is overlapped and connected with the upper surface of the middle square body, and the upper surface is in tight contact with the lower surface of the rectangular steel pressure head. Two positioning grooves with a width of 1mm and a depth of 1mm are symmetrically distributed in the middle of the upper surface in the direction parallel to the axial section. The side walls of the two positioning grooves are parallel to the side surfaces of the middle square body. The distance between the inner walls of the two positioning grooves is 20mm, and the vertical distance from the bottom of the groove to the lower surface of the middle square body is 30mm; the tail of the micro screw hydraulic jack is fixedly connected to the rectangular reaction steel plate; the short sides of both sides of the rectangular reaction steel plate are symmetrically installed with L-shaped reaction steel feet that can hook the top pull test sample face to face; the rectangular reaction steel plate and the L-shaped reaction steel feet jointly set the rectangular steel pressure head, the spherical support, and the micro screw hydraulic jack cover therein; The longitudinal axes of the top-pull test specimen, the rectangular steel pressure head, the spherical support, the micro screw hydraulic jack and the rectangular reaction steel plate are coaxial.

2. A device for testing the compressive strength of solid concrete by top-pull method according to claim 1, characterized in that: The rectangular steel pressure head has a long side of 100 mm, a short side of 20 mm, a thickness of 10 mm-20 mm, an end face in the same plane as the end face of the bow, a lower surface in contact with the upper surface of the bow of the top-pulling specimen, and the center of the upper surface is connected to the head of a micro screw hydraulic jack through a spherical support.

3. A device for testing the compressive strength of solid concrete by top-pull method according to claim 1, characterized in that: A screw sleeve perpendicular to the longitudinal axis of the micro screw hydraulic jack is connected to the circumferential side of the micro screw hydraulic jack, a screw is arranged in the screw sleeve, and a T-shaped socket wrench for applying a top pulling force is installed at the end of the screw; a digital pressure gauge is also connected to the circumferential side of the micro screw hydraulic jack.

4. The device for testing the compressive strength of solid concrete by top-pull method according to claim 1, characterized in that: The rectangular reaction steel plate has a long side of 120mm-140mm, a short side of 100mm, and a thickness of 10mm-20mm; three connecting circular holes for connecting with two L-shaped reaction steel pull feet are evenly drilled on the edges of the short sides on both sides.

5. The device for testing the compressive strength of solid concrete by top-pull method according to claim 1, characterized in that: The L-shaped reaction steel pull leg includes a lower cuboid and an upper cuboid; the outer side of the upper surface of the lower cuboid is fixedly connected to the lower surface of the upper cuboid; the long side of the lower cuboid is 100mm, the high side is 10mm-20mm, the side surface is parallel to the side surface of the lower cuboid of the top-pull specimen, and the end surface is in the same plane as the end surface of the lower cuboid of the top-pull specimen; the long side of the upper cuboid is 100mm, the short side is 10mm-20mm, the side surface is parallel to the side surface of the lower cuboid of the top-pull specimen, and the end surface is in the same plane as the end surface of the lower cuboid of the top-pull specimen; 3 connecting screw holes corresponding to the positions of the connecting circular holes are drilled on the upper surface of the upper cuboid, and the connecting bolts can pass through the connecting circular holes and screw into the connecting screw holes; the distance from the inner side surface of the lower cuboid to the inner side surface of the upper cuboid is 10mm; the distance between the inner side surfaces of the two facing lower cuboids is 80mm.

6. A method for testing a solid concrete compressive strength top-pull method testing device, using the testing device as claimed in claim 1, comprising the following testing steps: (1) grasping the handle on the auxiliary steel support by hand so that the two legs press the solid concrete surface; (2) using a portable concrete cutter equipped with three cutting blades with a total spacing of 30 mm, adjusting the depth of the cutting blades, placing the concrete cutter flat on the upper surface of the auxiliary steel support, and passing the cutting blade through the axial operating groove cutting port, axially moving to cut the solid concrete, forming an inner wall with a depth of 39 mm and a width of 30 mm m operation groove, chisel out the concrete in the operation groove and grind the groove bottom to be flat; (3) Use a portable concrete cutter equipped with a single cutting blade, adjust the cutting blade depth, place the concrete cutter flat on the upper surface of the auxiliary steel bracket, and let the cutting blade pass through the cutting opening of the axial positioning groove. Move axially to cut the solid concrete to form a positioning groove with a depth of 1 mm and a width of 1 mm; (4) Use an angle grinder, adjust the length of the extension rod, install the extension rod and the sintered grinding head, and the distance from the outer edge of the extension rod to the outer edge of the sintered grinding head is 11 mm. Place the angle grinder flat on the auxiliary steel bracket. The extension rod passes through the axial operation groove cutting opening and is close to the inner wall of the operation groove, and moves axially to grind the concrete on the inner wall of the operation groove; (5) Use a portable concrete cutting machine equipped with a single cutting blade, adjust the cutting blade depth, place the concrete cutting machine flat on the upper surface of the auxiliary steel bracket, move the auxiliary steel bracket axially, and the cutting blade passes through the radial positioning groove cutting opening, and moves radially to cut the solid concrete with a cutting depth of 45 mm to form a top-pull specimen; (6) Remove the auxiliary steel bracket, extend the two L-shaped reaction steel feet into the operation groove to hook the top-pull specimen; (7) Arrange the rectangular steel pressure head, spherical support, micro screw hydraulic jack, and rectangular reaction steel plate in sequence, and screw the connecting bolts through the connecting circular holes into the connecting screw holes and tighten them; (8) Put a T-type socket wrench on the end of the screw, and rotate the screw continuously and evenly to apply force so that the rectangular steel pressure head presses against the upper surface of the top-pull specimen. At the same time, the L-shaped reaction steel pull leg is driven upward relative to the top-pull specimen through the rectangular reaction steel plate until the top-pull specimen is destroyed. Read the maximum top-pull force value, and estimate the concrete compressive strength based on the conversion formula established between the concrete compressive strength and the top-pull force value.

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