Testing device and method for flexural strength and compressive strength of structural concrete

Abstract

The present invention discloses a testing device and method for the flexural strength and compressive strength of structural concrete. The testing device includes a thrust rod, a thrust tooth, a reaction ring, a hollow jack, and a cylindrical force sensor. One end of the thrust rod passes horizontally through the side wall of the reaction ring, and the other end of the thrust rod passes through the hollow jack. The thrust tooth is fixed to the thrust rod and located inside the reaction ring. The device also includes a cylindrical force sensor, which is sleeved on the thrust rod and abuts against the outside of the hollow jack to assist in measuring the strength of the concrete entity. The testing device and method for the flexural strength and compressive strength of structural concrete provided by the present invention have a reasonable structure and can complete the flexural strength and compressive strength tests at one time, with the advantage of high testing efficiency. At the same time, the test is a micro-damage test, and the damage to the concrete during the test process is very small. After the test surface is repaired, it will not affect the safe use of the solid structure.

Description

Technical Field

[0001] The invention belongs to the technical field of construction engineering, and relates to a testing device and method for the flexural strength and compressive strength of structural solid concrete. Background Art

[0002] Because concrete pavements are directly affected by repeated vehicle loads and environmental factors such as temperature and humidity, their design requires high flexural strength, durability, wear resistance, and skid resistance. Flexural strength is a key quality control indicator for concrete pavements; whether it meets design requirements directly impacts the overall quality and service life of the pavement.

[0003] The "Standard for Test Methods for the Physical and Mechanical Properties of Concrete" (GBT50081-2019) specifically specifies test methods for concrete flexural strength and compressive strength. The flexural strength of concrete specified in this standard is determined by testing 150mm×150mm×550mm beam specimens under standard curing conditions at pure bending failure with a clear span of 450mm and double-support loading at 28 days after the specified age. The compressive strength of concrete specified in this standard is determined by testing 150mm×150mm×150mm cube specimens under standard curing conditions at 28 days after the specified age in a press. However, this method is limited to testing specially fabricated beam or cube specimens under standard curing conditions. This means that the test results can only indicate whether the concrete mix meets the design requirements in terms of proportions. During the construction of actual structural concrete pavements, the hardening process of concrete is not subject to standard curing, which is far from the molding conditions of the standard specimens. That is to say, it is unknown whether the actual structural concrete flexural strength and compressive strength meet the design requirements.

[0004] Therefore, people are eager to know whether the flexural and compressive strengths of structural concrete after construction meet the design requirements. However, in the current construction of roads, bridges, buildings, and airport runways, there are no test methods or testing devices that can directly confirm the flexural strength of concrete entities.

[0005] Therefore, there is an urgent need to design a testing device and method for the flexural strength and compressive strength of structural solid concrete to solve the technical problems existing in the prior art. Summary of the Invention

[0006] The purpose of the present invention is to solve some of the technical problems existing in the prior art to a certain extent at least. The device and method for testing the flexural strength and compressive strength of structural concrete are provided. The device and method have a reasonable structure and can complete the test of the flexural strength and compressive strength of structural concrete in one test, which has the advantage of high testing efficiency. At the same time, the test is a micro-damage test, and the damage to the concrete during the test process is very small. The test surface will not affect the safe use of the solid structure after repair.

[0007] In order to solve the above technical problems, the present invention provides a testing device for the flexural strength and compressive strength of structural solid concrete, which includes a thrust rod, a thrust tooth, a reaction ring and a hollow jack, one end of the thrust rod passes through the side wall of the reaction ring, and the other end of the thrust rod passes through the hollow jack, and the thrust tooth is fixed to the thrust rod and located inside the reaction ring; it also includes a cylindrical force sensor, which is sleeved on the thrust rod and abuts against the outside of the hollow jack to measure the lateral thrust value at the moment of concrete breaking; the reaction ring is sleeved in the outer ring groove of the double ring groove on the surface of the concrete entity, the thrust tooth is clamped in the inner ring groove of the double ring groove, and the reaction ring is pushed by the hollow jack, and the thrust tooth pushes the concrete column formed by the inner ring groove in the opposite direction, and the cylindrical force sensor records the load when the concrete column breaks.

[0008] In some embodiments, the reaction ring is a circular ring structure, and its size matches the size of the outer ring groove.

[0009] In some embodiments, the thrust tooth is a circular ring structure, which is 1 / 8-1 / 4 of the entire circular ring; the shape of the thrust tooth matches the size of the inner ring groove.

[0010] In some embodiments, a boss is provided at the lower end of the thrust tooth, and the boss is formed to extend horizontally toward the outside.

[0011] In some embodiments, the testing device for the flexural strength and compressive strength of structural solid concrete also includes a limiting assembly, which includes a support rod and a limiting wheel, the limiting wheel is installed on the support rod and fixed in the reaction ring; and the support rod is perpendicular to the thrust rod.

[0012] In some embodiments, the support rod and the thrust rod are vertically staggered; the outer peripheral wall of the limiting wheel is configured with an arc surface, and the arc surface is matched with the outer diameter of the thrust rod.

[0013] In some embodiments, the end of the thrust rod is configured with a limit nut and a locking nut, the limit nut is arranged adjacent to the reaction ring, and the locking nut is arranged adjacent to the cylindrical force sensor, and both are threadedly connected to the thrust rod to fix the reaction ring and the cylindrical force sensor to the thrust rod respectively.

[0014] In addition, the present invention also provides a method for testing the flexural strength and compressive strength of structural concrete, which uses the above-mentioned testing device for the flexural strength and compressive strength of structural concrete, comprising:

[0015] Step 1: Select a plane to be measured on the concrete structure to be measured, and use a coaxial double drill bit to cut a double annular groove to form an outer annular groove and an inner annular groove, wherein the cutting depth of the inner annular groove is greater than or equal to 2 times the diameter of the inner annular groove;

[0016] Step 2: Insert the reaction ring into the outer ring groove, adjust the position of the thrust rod in the reverse ring, insert the thrust teeth at the front end of the thrust rod into the inner ring groove, tighten the limit nut on the outside of the reaction ring, and sequentially sleeve the hollow jack and the cylindrical force sensor on the thrust rod and secure them with the locking nut;

[0017] Step 3: Clear the load table connected to the cylindrical force sensor, start the hollow jack when the concrete column is not under force, and abut the inner and outer walls of the reaction ring with the inner and outer walls of the outer ring groove to form reverse support. Apply lateral force to the concrete column through the thrust teeth until the concrete column is destroyed by the combined external force of bending and shearing.

[0018] Step 4: Record the thrust value N at the moment of concrete column failure, the distance L between the failure section and the point of lateral thrust application, and the diameter d of the concrete column. Substitute the above data into the previously established concrete flexural strength and compressive strength calculation formulas to estimate the flexural strength and compressive strength of the measured concrete entity.

[0019] In some embodiments, the diameter of the outer ring groove is 1.6 times the diameter of the inner ring groove, and the diameter of the inner ring groove is greater than 2 times the particle size of concrete coarse aggregate.

[0020] In some embodiments, the flexural strength of the concrete body is The compressive strength of the concrete entity

[0021] Where: N is the lateral thrust between the specimens, in Newtons;

[0022] L is the length from the thrust point to the fracture position of the specimen, i.e. the length of the lever arm (mm);

[0023] d is the specimen diameter (mm).

[0024] Beneficial effects of the present invention:

[0025] The device and method for testing the flexural strength and compressive strength of structural concrete provided by the present invention have a reasonable structure and have the following technical effects:

[0026] a. The flexural strength and compressive strength tests can be completed at one time, with the advantages of low testing cost and high testing efficiency;

[0027] b. This test is a micro-damage test. The test process causes minimal damage to the concrete structure. The repaired test surface will not affect the safe use of the physical structure.

[0028] c. This test method has the advantages of high detection accuracy, easy portability and quick operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The above advantages of the present invention will become clearer and easier to understand through the detailed description made in conjunction with the following drawings, which are only exemplary and do not limit the present invention, wherein:

[0030] Figure 1 Schematic diagram of a testing device for the flexural strength and compressive strength of structural concrete provided by one embodiment of the present invention;

[0031] Figure 2 yes Figure 1 The corresponding force diagram of the solid concrete of the test structure;

[0032] Figure 3 is a schematic diagram of the thrust tooth of the present invention;

[0033] Figure 4 This is a schematic diagram of the assembly of a limit assembly, a thrust rod, and a reverse ring provided by one embodiment of the present invention;

[0034] Figure 5 is a cross-sectional view of the reaction ring of the present invention;

[0035] Figure 6 is a schematic diagram of the limiting wheel of the present invention;

[0036] Figure 7 is a schematic diagram of a testing device for the flexural strength and compressive strength of structural concrete provided by another embodiment of the present invention;

[0037] Figure 8 yes Figure 6 Flowchart of the test method for the flexural strength and compressive strength of structural concrete

[0038] Figure 9 FIG. 1 is a schematic diagram of a dual drill bit provided in accordance with an embodiment of the present invention. DETAILED DESCRIPTION

[0039] Figures 1 to 9 Schematic diagram of the testing device and method for the flexural strength and compressive strength of structural concrete described in the present application. The present invention is described in detail below in conjunction with specific embodiments and drawings.

[0040] The embodiments described herein are specific embodiments of the present invention and are used to illustrate the concept of the present invention. They are illustrative and exemplary and should not be construed as limiting the embodiments and scope of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the claims and the disclosure of the specification, including technical solutions that adopt any obvious substitutions and modifications to the embodiments described herein.

[0041] The drawings in this specification are schematic diagrams that assist in illustrating the concepts of the present invention and schematically illustrate the shapes of the various components and their interrelationships. Please note that to clearly illustrate the structures of the various components of the embodiments of the present invention, the drawings are not drawn to the same scale. The same reference numerals are used to indicate the same parts.

[0042] A schematic diagram of a testing device for the flexural strength and compressive strength of structural concrete according to the present invention, as shown in FIG. Figure 1 A testing device for the flexural and compressive strength of structural concrete includes a thrust rod 10, a thrust tooth 20, a reaction ring 30, and a hollow jack 40. One end of the thrust rod 10 passes through the side wall of the reaction ring 30, and the other end of the thrust rod 10 passes through the hollow jack 40. The thrust tooth 20 is fixed to the thrust rod 10 and located inside the reaction ring 30.

[0043] Furthermore, the testing device for the flexural strength and compressive strength of structural concrete also includes a cylindrical force sensor 50, which is sleeved on the thrust rod 10 and abuts against the outer side of the hollow jack 40 to measure the lateral thrust value at the moment the concrete column 70 breaks.

[0044] The reaction ring 30 is sleeved in the outer ring groove 61 of the double ring groove 60 cut in advance in the concrete body ( Figure 2 As shown), the thrust tooth 20 is clamped in the inner ring groove 62 of the double annular groove 60, and the reaction ring 30 is pushed by the hollow jack 40. The thrust tooth 20 pushes the concrete column 70 formed by the inner ring groove 62 in the opposite direction, and the cylindrical force sensor 50 records the lateral thrust value of the concrete column 70 at the moment of breaking.

[0045] As an embodiment of the present invention, the reaction ring 30 is a circular ring structure, and its size matches the size of the outer ring groove 61 .

[0046] Furthermore, the thrust tooth 20 is a circular ring structure, which is 1 / 8-1 / 4 of the entire circular ring; the shape of the thrust tooth 20 matches the size of the inner ring groove 62.

[0047] The lower end of the thrust tooth 20 is provided with a boss 21. Figure 3 As shown, the boss 21 is formed by extending horizontally toward the outside. It can be understood that the thrust tooth 20 is an annular structure, and accordingly, the boss 21 is also an annular structure so as to abut against the outer wall of the concrete column 70. Figure 3 In the embodiment, the vertical height of the boss 21 is 1 mm, so that the thrust teeth 20 can act on the outer wall of the concrete column 70 through the narrow boss 21, thereby causing the concrete column 70 to be subjected to lateral thrust and destroyed.

[0048] Figure 1 In the embodiment shown, the end of the thrust rod 10 is provided with a limit nut 91 and a locking nut 92. The limit nut 91 is arranged adjacent to the reaction ring 30, and the locking nut 92 is arranged adjacent to the cylindrical force sensor 50. Both are threadedly connected to the thrust rod 10. The locking nut 92 limits the reaction ring 30, the cylindrical force sensor 50 and the hollow jack 40 to the thrust rod 10, and can move freely axially relative to the thrust rod 10.

[0049] As an embodiment of the present invention, the testing device for the flexural strength and compressive strength of structural concrete further includes a limiting component 80, such as Figure 4 As shown, the limiting assembly 80 includes a support rod 81 and a limiting wheel 82 that can rotate freely on the support rod 81. The limiting wheel 82 is installed on the support rod 81 and fixed in the reaction ring 30. In addition, the support rod 81 is perpendicular to the thrust rod 10.

[0050] Figure 8 In the illustrated embodiment, the support rods 81 and the thrust rods 10 are vertically staggered to avoid interference between the thrust rods 10 and the limiting wheels 82 . Figure 5 yes Figure 4 The cross-sectional view of the reaction ring 30 in the embodiment shows that the through-holes through which the thrust rod 10 passes and the through-holes that secure the thrust rod 10 are vertically staggered along the sidewall of the reaction ring 30. This allows the thrust rod 10 to engage within the groove of the retaining wheel 82. Consequently, during testing, the thrust rod 10 always moves along its axis without deflection. This prevents the thrust rod 10 from slightly shifting perpendicular to its axis during testing, which could affect testing accuracy.

[0051] Figure 5 In the embodiment, a depth limiting ring 31 is provided at the lower end of the reaction ring 30, so that the wall thickness of the lower end of the reaction ring 30 is smaller, so that the reaction ring 30 can be smoothly engaged with the interior of the outer ring groove 61; at the same time, the setting of the depth limiting ring 31 ensures that the depth of the lower end of the reaction ring 30 inserted into the inner ring groove 62 is the same during each test.

[0052] Furthermore, the outer peripheral wall of the limiting wheel 82 is provided with an arc surface 82a, such as Figure 6 As shown, the arcuate surface 82 a is matched with the outer diameter of the thrust rod 10 .

[0053] At the same time, the present invention also provides a testing device and method for the flexural strength and compressive strength of structural concrete, which uses the testing device for the flexural strength and compressive strength of structural concrete described above, and its flow chart is as follows: Figure 8 As shown, including:

[0054] Step 1: Select a plane to be measured on the concrete structure entity to be measured, and use the coaxial double drill bit 100 ( Figure 9 (shown) cutting a double annular groove 60 to form an outer annular groove 61 and an inner annular groove 62, wherein the cutting depth of the inner annular groove 62 is greater than or equal to 2 times the diameter of the inner annular groove; further, the diameter of the outer annular groove 61 is 1.6 times the diameter of the inner annular groove 62, and the diameter of the inner annular groove 62 is greater than 2 times the particle size of the concrete coarse aggregate.

[0055] During the machining of the double annular groove 60, the inner drill 110 of the coaxial dual drill bit 100, in conjunction with a general-purpose drilling rig, was used to separate the test concrete from the structural concrete, leaving only the cylindrical concrete base (concrete column 70) connected to the structural concrete. Simultaneously, the outer drill 120 of the coaxial dual drill bit 100 was used to cut a groove (inner annular groove 62) in the structural concrete for applying reaction force during subsequent testing, and to remove any remaining cooling water.

[0056] Step 2: Insert the reaction ring 30 into the outer ring groove 61, adjust the position of the thrust rod 10 in the reaction ring 30 until the thrust teeth 20 at the front end of the thrust rod 10 are inserted into the inner ring groove 62, and sequentially install the hollow jack 40 and the cylindrical force sensor 50 on the thrust rod 10 and tighten the lock nut 92;

[0057] Step 3: Clear the load meter 51 connected to the cylindrical force sensor 50, and start the hollow jack 40 when the concrete column 70 is not under any force. The inner and outer walls of the reaction ring 30 abut against the inner and outer walls of the outer ring groove 61 to form a reverse support, and then gradually apply a lateral thrust to the concrete column 70 through the thrust teeth 20 until the concrete column 70 is destroyed by the combined external force of bending and shearing.

[0058] Step 4: Follow Figure 2 Schematic diagram, record the thrust value N at the moment of concrete column 70 failure, the distance L between the failure section and the point of lateral thrust application, and the diameter d of the concrete column 70, substitute the above data into the pre-established concrete flexural strength calculation formula and compressive strength calculation formula, and then infer the flexural strength and compressive strength of the measured concrete entity.

[0059] Wherein, N is the thrust of the test device on the concrete column 70 (test piece), and N1 and N2 are the reaction forces of the structural concrete entity on the test device. The numerical relationship between them is N=N1+N2.

[0060] Flexural strength of the concrete entity The compressive strength of the concrete entity

[0061] Where N is the lateral thrust between the specimens, in Newton; L is the length from the thrust application point to the fracture position of the specimen, that is, the length of the lever arm (mm); and d is the diameter of the specimen (mm).

[0062] The determination of flexural (compressive) strength values ​​is based on the following basic principles:

[0063] ① The arithmetic average of the estimated strengths at the three measuring points shall be used as the flexural (compressive) strength value of the batch of poured concrete, which shall be accurate to 0.1 MPa;

[0064] ② If the difference between the maximum or minimum value of the estimated strength at the three measuring points and the median value exceeds 15% of the median value, the maximum and minimum values ​​should be discarded and the median value should be taken as the flexural strength value of the group of specimens;

[0065] ③ When the difference between the maximum and minimum values ​​of the estimated intensity at the three measuring points and the median value exceeds 15% of the median value, the test results of this group of measuring points are invalid.

[0066] When establishing the test strength formula in advance, the N, L, and d values ​​for each test set should be recorded, along with the concrete flexural and compressive strengths obtained from the destructive tests on standard specimens. Statistical analysis should then be performed on the flexural and compressive strengths to develop practically applicable test formulas for these strengths.

[0067] It should be noted that the formulas for the flexural strength and compressive strength of the above-mentioned concrete entities are obtained by using sand and gravel aggregates and cement commonly used in Beijing, and configuring concrete of eight strength grades of C15, C20, C25, C30, C35, C40, C50, and C60 to make test specimens for testing. The flexural strength and compressive strength calculation formulas were obtained after statistical regression analysis of the test data.

[0068] The correlation coefficient for the flexural strength calculation formula above is r = 0.97, which is highly correlated. The coefficients for the flexural strength calculation formula established will vary depending on the concrete materials, such as sandstone aggregates and cement, used in different regions. The correlation coefficient for the compressive strength calculation formula above is r = 0.96, also highly correlated. The coefficients for the compressive strength calculation formula established will also vary depending on the concrete materials, such as sandstone aggregates and cement, used in different regions.

[0069] The present invention provides a testing device and method for the flexural and compressive strength of structural concrete. By randomly arranging measuring points on hardened concrete using a dual drill bit, the test results are representative. The obtained strengths are the compressive and flexural strengths of the concrete entity. The device and method are suitable for testing concrete roads, bridges, buildings, and airport runways of various strength grades, and have the advantage of a wide range of uses.

[0070] The present invention is not limited to the above-mentioned embodiments. Anyone can derive other forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, any product with the same or similar technical solutions as the present application falls within the scope of protection of the present invention.

Claims

1. A testing device for the flexural strength and compressive strength of structural concrete, characterized in that: The invention comprises a thrust rod (10), a thrust tooth (20), a reaction ring (30), a hollow jack (40) and a cylindrical force sensor (50), wherein one end of the thrust rod (10) passes horizontally through the side wall of the reaction ring (30), and the other end of the thrust rod (10) passes through the hollow jack (40), and the thrust tooth (20) is fixed to the thrust rod (10) and is located inside the reaction ring (30); and further comprises a cylindrical force sensor (50), which is sleeved on the thrust rod (10) and abuts against the outer side of the hollow jack (40) to measure The lateral thrust value at the moment when the concrete column (70) breaks is measured; the reaction ring (30) is sleeved in the outer ring groove (61) of the double ring groove (60) on the surface of the concrete entity, and the thrust teeth (20) are engaged in the inner ring groove (62) of the double ring groove (60). The reaction ring (30) is pushed horizontally by the hollow jack (40), and the thrust teeth (20) push the concrete column (70) formed by the inner ring groove (62) in the opposite direction. The cylindrical force sensor (50) records the lateral thrust value when the concrete column (70) breaks.

2. The testing device according to claim 1, wherein: The reaction ring (30) is a circular ring structure, and its size matches the size of the outer ring groove (61).

3. The testing device according to claim 1, wherein: The thrust tooth (20) is a circular ring structure, which is 1 / 8-1 / 4 of the entire circular ring; the shape of the thrust tooth (20) matches the size of the inner ring groove (62).

4. The testing device according to claim 3, characterized in that: A boss (21) is provided at the lower end of the thrust tooth (20), and the boss (21) is formed to extend horizontally toward the outside.

5. The testing device according to claim 1, wherein: It also includes a limiting assembly (80), which includes a support rod (81) and a limiting wheel (82), wherein the limiting wheel (82) is mounted on the support rod (81) and fixed in the reaction ring (30); and the support rod (81) is perpendicular to the thrust rod (10).

6. The testing device according to claim 5, characterized in that: The support rod (81) and the thrust rod (10) are arranged in a vertically staggered manner; the outer peripheral wall of the limiting wheel (82) is provided with an arcuate surface (82a), and the arcuate surface (82a) is matched with the outer diameter of the thrust rod (10).

7. The testing device according to claim 1, characterized in that The end of the thrust rod (10) is provided with a limit nut (91) and a locking nut (92), wherein the limit nut (91) is arranged adjacent to the reaction ring (30), and the locking nut (92) is arranged adjacent to the cylindrical force sensor (50), and both are threadedly connected to the thrust rod (10) to respectively fix the reaction ring (30) and the cylindrical force sensor (50) to the thrust rod (10).

8. A method for testing the flexural strength and compressive strength of structural concrete, characterized in that: Use of the testing device according to any one of claims 1 to 7, comprising: Step 1: Select a plane to be measured on the concrete structure to be measured, and use a coaxial double drill bit to cut a double annular groove (60) to form an outer annular groove (61) and an inner annular groove (62), wherein the cutting depth of the inner annular groove (62) is greater than or equal to 2 times the diameter of the inner annular groove (62); Step 2: embed the reaction ring (30) into the outer ring groove (61), adjust the position of the thrust rod (10) in the reaction ring (30), insert the thrust tooth (20) at the front end of the thrust rod (10) into the inner ring groove (62), lock the limit nut (91) outside the reaction ring (30), and sequentially sleeve the hollow jack (40) and the cylindrical force sensor (50) on the thrust rod (10) and fix them with the locking nut (92); Step 3: Clear the load table connected to the cylindrical force sensor (50), start the hollow jack (40) when the concrete column (70) is not subjected to force, and form a reverse support by abutting the inner and outer walls of the reaction ring (30) with the inner and outer walls of the outer ring groove (61), and apply a lateral force to the concrete column (70) through the thrust teeth (20) until the concrete column (70) is destroyed by the combined external force of bending and shearing; Step 4: Record the thrust value N at the moment of failure of the concrete column (70), the distance L between the failure section and the point of action of the lateral thrust, and the diameter d of the concrete column (70), and substitute the above data into the previously established formula for calculating the flexural strength and compressive strength of concrete to estimate the flexural strength and compressive strength of the measured concrete entity.

9. The testing method according to claim 8, characterized in that: The diameter of the outer annular groove (61) is 1.6 times the diameter of the inner annular groove (62), and the diameter of the inner annular groove (62) is greater than 2 times the particle size of the concrete coarse aggregate.

10. The testing method according to claim 8, characterized in that: Flexural strength of the concrete entity ; The compressive strength of the concrete entity ; Where: N is the lateral thrust between the specimens, in Newtons; L is the length from the thrust point of the specimen to the fracture position, that is, the length of the lever arm, in mm; d is the specimen diameter, in mm.

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