A method for testing the compressive strength of thin concrete using lateral pressure method
By drilling and processing the concrete core sample, using the side press head to press the side pressure failure of the thin concrete layer by recording the maximum side pressure value and estimating the compressive strength, the detection of thin concrete in the prior art is solved. Inadequately, high accuracy and strong practical detection methods are achieved.
Patent Information
- Application Number
- CN202110197379.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-02-22
- Publication Date
- 2024-12-27
- Estimated Expiration
- 2041-02-22
AI Technical Summary
It is difficult for the prior art to effectively detect the compressive strength of thin concrete with a thickness of 10mm-80mm, especially the ground surface layer. The detection method has problems such as low accuracy and strong inapplicability.
The concrete core sample is drilled, polished and cut into a side pressure specimen, and pressed into the press using the side pressure head to the side pressure failure of the thin layer of concrete, record the maximum side pressure value, and estimate the compressive strength through the conversion formula.
Accurate detection of thin concrete with a thickness of 10mm-80mm is achieved, which improves the practicality and accuracy of the inspection, and solves the shortcomings of the existing methods.
Smart Images
Figure CN112665985B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a method for detecting the compressive strength of thin-layer concrete using a lateral pressure 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 structural 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 briefly introduced 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 edge surface of the concrete component, causing local shear compression failure of the right-angled edge 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 impossible to detect thin layers of concrete without right-angled edges, such as the ground surface layer, which affects the practicality of the test. (2) Core drilling method. Drill concrete specimens on the concrete component and process them into standard core samples, and then perform compressive strength testing on a pressure testing machine. The shortcomings of this test method are: since the size of the prepared standard core sample is ø100×100㎜, it is impossible to detect thin layers of concrete with a thickness of 10mm-80mm, such as the ground surface layer, which is generally 40㎜~60㎜, 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: the accuracy of the compressive strength derived from the relationship between surface hardness and strength is low, which affects the accuracy of the test; it is not suitable for unfixed thin structural components and structural components with an age of more than 1000 days, 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 concrete component surface and the ultrasonic wave velocity in the concrete component. The shortcomings of this test method: the test operation process is relatively cumbersome, there are many factors affecting the test, and it is easy to produce multiple test deviations, which affects the accuracy of the test; it is not suitable for unfixed thin structural components and structural components with an age of more than 2000 days, 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 the range of 30mm on the surface of the concrete component. The shortcomings of this detection method: the detection process requires complex drilling and grooving procedures. The thickness of the structural member to be tested should be greater than 80mm. For thin layers of concrete with a thickness of 10mm-80mm, such as the ground surface layer, the thickness is generally 40mm~60mm, which cannot be detected, affecting the practicality of the detection. (6) Pull-off method. On the hardened concrete member, drill a core specimen with a diameter of 44mm and a depth of 44mm, and use a device with automatic clamping of the specimen to perform a pull-off test. The compressive strength of the concrete is estimated based on the pull-off strength value of the core specimen. The shortcomings of this detection method: when calculating the stress of the pull-off specimen, it is necessary to measure the diameter size at a mutually perpendicular position close to the fracture of the specimen. Due to the small diameter of the specimen, accurate measurement is difficult, affecting the accuracy of the detection; for thin layers of concrete with a thickness of 10mm-44mm, it cannot be detected, affecting the practicality of the detection.
[0004] In summary, when testing thin layers of concrete with a thickness of 10mm-80mm, the above methods all have various shortcomings, so innovative designs are needed. Summary of the invention
[0005] The present invention proposes a lateral pressure method for testing the compressive strength of thin-layer concrete, which is highly practical and accurate, and can solve the problems existing in various existing methods when testing thin-layer concrete with a thickness of 10mm-80mm.
[0006] The technical solution adopted by the present invention is: a method for testing the compressive strength of thin-layer concrete by lateral pressure, comprising the following steps: (1) drilling a core sample containing a thin layer of concrete at a suitable position of solid concrete; (2) grinding the end face of the core sample until it is flat, cutting the side face of the core sample with pressure surfaces symmetrically distributed on both sides of the core sample to form a lateral pressure test piece; (3) placing the pressure surface of one side of the lateral pressure test piece flat on a pressure plate of a press equipped with a lateral pressure head, and the thin layer of concrete on the pressure surface of the other side contacts the lateral pressure head; (4) starting the press to apply pressure until the thin layer of concrete of the lateral pressure test piece is destroyed by lateral pressure, and recording the maximum lateral pressure value; (5) estimating the compressive strength of the thin layer of concrete according to a conversion formula established between the compressive strength of concrete and the lateral pressure value.
[0007] Furthermore, the solid concrete in step (1) includes a thin layer of concrete on the surface and a base layer of concrete inside; the core sample has a diameter of not less than 70 mm and a length of not less than 50 mm; and the longitudinal axis of the core sample is perpendicular to the thin layer of concrete.
[0008] Furthermore, the pressure surface of step (2) is rectangular, with a long side equal to the core sample and parallel to the longitudinal axis of the core sample, a short side perpendicular to the longitudinal axis of the core sample and located in the end plane, a short side length of 20 mm, 30 mm or 40 mm, a short side length not greater than 1 / 3 of the core sample diameter, a short side length not greater than 2 times the thickness of the thin layer of concrete, and a short side length not less than the maximum aggregate particle size of the solid concrete.
[0009] Furthermore, the side pressure head in step (3) is made of steel and is cut along the longitudinal axis from a cylinder with a diameter the same as the short side length of the pressure surface. The longitudinal section is perpendicular to the pressure surface and is in the same plane as the end face of one end of the thin layer of concrete of the side pressure specimen. The entire end face of one end of the side pressure head is in contact with the pressure surface of the side pressure specimen, and the other end is installed on the press.
[0010] The beneficial effects of the present invention are as follows: (1) a lateral pressure test piece is made by drilling a concrete core sample, and a press machine equipped with a lateral pressure head is used to apply pressure to the thin layer of concrete of the lateral pressure test piece until it is destroyed, and the maximum lateral pressure value is recorded. The compressive strength of the thin layer of concrete is estimated based on a conversion formula established between the compressive strength of the concrete and the lateral pressure value. The design route is scientific and accurate. (2) high-end testing equipment is not required, and the required instruments and equipment are easy to purchase and process, and are highly practical. (2) various problems existing in the existing methods when testing thin layers of concrete with a thickness of 10 mm to 80 mm are solved. BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Figure 1 It is a front view schematic diagram of the use of the present invention.
[0012] Figure 2 It is a schematic diagram of the DD cross section of the present invention.
[0013] Figure 3 It is a schematic diagram of the AA cross section of the present invention.
[0014] Figure 4 It is a schematic diagram of the BB cross section of the present invention.
[0015] Figure 5 It is a schematic diagram of the CC cross section of the present invention. DETAILED DESCRIPTION
[0016] 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.
[0017] Reference Figure 1-5 A method for testing the compressive strength of thin-layer concrete by lateral pressure method comprises the following steps: (1) drilling a core sample containing a thin layer of concrete 5 at a suitable position of solid concrete; (2) grinding the end face of the core sample until it is flat, cutting the side face of the core sample with a pressure surface 7 and a pressure surface 8 symmetrically distributed on both sides of the core sample to form a lateral pressure test piece 3; (3) placing the pressure surface 8 of the lateral pressure test piece 3 flat on a pressure plate 4 of a press 1 equipped with a lateral pressure head 2, so that the thin layer of concrete 5 on the pressure surface 7 contacts the lateral pressure head 2; (4) starting the press 1 to apply pressure until the thin layer of concrete 5 of the lateral pressure test piece 3 is destroyed by lateral pressure, and recording the maximum lateral pressure value; (5) estimating the compressive strength of the thin layer of concrete 5 according to a conversion formula established between the compressive strength of concrete and the lateral pressure value.
[0018] The solid concrete in step (1) of this embodiment includes a thin layer of concrete 5 on the surface and a base layer of concrete 6 inside. The thickness of the thin layer of concrete 5 is 40 mm. The core sample has a diameter of 100 mm and a length of 100 mm. The longitudinal axis of the core sample is perpendicular to the thin layer of concrete 5.
[0019] The pressure surfaces 7 and 8 in step (2) of this embodiment are rectangular, with a long side of 100 mm and parallel to the longitudinal axis of the core sample, a short side perpendicular to the longitudinal axis of the core sample and located in the end plane, a short side length of 30 mm, and a maximum aggregate particle size of 20 mm in the solid concrete.
[0020] The side pressure head 2 in step (3) of this embodiment is made of steel and is cut along the longitudinal axis from a cylinder with a diameter of 30 mm. The longitudinal section is perpendicular to the pressure surface 7 and is in the same plane as the end surface of the thin layer of concrete 5 of the side pressure specimen 3. The entire end surface of one end of the side pressure head 2 is in contact with the pressure surface 7, and the other end is installed on the press 1.
[0021] In this embodiment, the conversion formula is as follows:
[0022] Yi=AXi+B
[0023] Wherein: Yi is the converted value (MPa) of the compressive strength of the i-th thin layer of concrete 5 when the present invention is used for detection; Xi is the maximum lateral pressure value (N) applied to the i-th thin layer of concrete 5 when the present invention is used for detection; A and B are the regression coefficients of the regression equation.
[0024] Of course, in addition to the above formula, the conversion formula between concrete compressive strength and lateral pressure value can also be other formulas and is not limited to the above formula.
Claims
1. A method for testing the compressive strength of thin concrete using a lateral pressure method, characterized in that: The following steps are involved: (1) Drill a core sample containing a thin layer of surface concrete and an inner base concrete at an appropriate location of the solid concrete. The core sample diameter shall not be less than 70 mm, the core sample length shall not be less than 50 mm, and the longitudinal axis of the core sample shall be perpendicular to the surface of the thin layer of concrete; (2) Grind the end face of the core sample until it is flat, and cut the side surface of the core sample with compressive surfaces symmetrically distributed on both sides of the core sample to make a lateral pressure test piece; (3) Place the compressive surface of one side of the lateral pressure test piece flat on the pressure plate of a press equipped with a lateral pressure head, and the thin layer of concrete on the other side of the compressive surface is in contact with the lateral pressure head; (4) Start the press and apply pressure until the thin layer of concrete of the lateral pressure test piece is destroyed by lateral pressure, and record the maximum lateral pressure value; (5) Estimate the compressive strength of the thin layer of concrete based on the conversion formula established between the compressive strength of concrete and the lateral pressure value.
2. A method for testing the compressive strength of thin-layer concrete by lateral pressure method according to claim 1, characterized in that: The pressure surface of step (2) is rectangular, with a long side equal to the core sample and parallel to the longitudinal axis of the core sample, a short side perpendicular to the longitudinal axis of the core sample and located in the end plane, a short side length of 20 mm, 30 mm or 40 mm, a short side length not greater than 1 / 3 of the core sample diameter, a short side length not greater than 2 times the thickness of the thin layer of concrete, and a short side length not less than the maximum aggregate particle size of the solid concrete.
3. The method for testing the compressive strength of thin-layer concrete by lateral pressure method according to claim 1, characterized in that: The side pressure head in step (3) is made of steel and is cut along the longitudinal axis from a cylinder with the same diameter as the short side length of the pressure surface. The longitudinal section is perpendicular to the pressure surface and is in the same plane as the end face of one end of the thin layer of concrete of the side pressure specimen. The entire end face of one end of the side pressure head is in contact with the pressure surface of the side pressure specimen, and the other end is installed on the press.