CN112665985A

CN112665985A - Method for detecting compressive strength of thin-layer concrete by lateral pressure method

Info

Publication number: CN112665985A
Application number: CN202110197379.XA
Authority: CN
Inventors: 程彦; 程杰; 郑骞; 左丽梅; 黄翔; 章建成; 任丽丽
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-02-22
Filing date: 2021-02-22
Publication date: 2021-04-16

Abstract

A method for detecting the compressive strength of thin-layer concrete by a lateral compression method is characterized by comprising the following steps: the method comprises the following steps: (1) drilling a core sample containing thin concrete at a proper position of the solid concrete; (2) polishing the end surface of the core sample to be flat, and cutting the side surface of the core sample into pressed surfaces symmetrically distributed on two sides of the core sample to prepare a side pressure test piece; (3) flatly placing a compression surface on one side of a side compression test piece on a pressure bearing plate of a press machine provided with a side compression head, and contacting thin-layer concrete on the compression surface on the other side with the side compression head; (4) starting a press machine to apply pressure until the lateral pressure of the thin-layer concrete of the lateral pressure test piece is damaged, and recording the maximum lateral pressure value; (5) and (4) estimating the compressive strength of the thin-layer concrete according to a conversion formula established between the compressive strength of the concrete and the lateral pressure value. The method has the advantages of scientific design route, high accuracy and strong practicability.

Description

Method for detecting compressive strength of thin-layer concrete by lateral pressure method

Technical Field

The invention relates to a side pressure method for detecting the compressive strength of thin-layer concrete.

Background

The compressive strength is one of important performance parameters of concrete, and is directly related to the quality safety and normal use of concrete structural members and even the whole engineering. Therefore, it is a very important task to measure the compressive strength of concrete.

In the prior art, there are many common methods for detecting the compressive strength of concrete, which are briefly described as follows: (1) a shearing and pressing method. The concrete shear-compression instrument is utilized to apply pressure perpendicular to the pressure bearing surface to the surface of the right-angle side of the concrete member, so that the right-angle side of the concrete member generates local shear-compression damage, and the compressive strength of the concrete member is estimated according to the shear pressure at the moment. The method has the following defects: the thin-layer concrete without right-angle edges can not be detected, and the detection practicability is influenced if the ground surface layer is used. (2) Core drilling method. And drilling a concrete test piece on the concrete member, processing the concrete test piece into a standard core sample, and detecting the compressive strength of the standard core sample on a pressure testing machine. The detection method has the following defects: the prepared standard core sample size is 100mm and 100mm, and the thickness of thin-layer concrete with the thickness of 10mm to 80mm, such as a ground surface layer, is generally 40mm to 60 mm, so that the thickness cannot be detected, and the detection practicability is influenced. (3) Rebound method. And estimating the compressive strength of the concrete member according to the relationship between the surface hardness and the strength of the concrete member. The detection method has the following defects: through the relationship between the surface hardness and the strength, the derived compressive strength has lower precision, and the detection accuracy is influenced; the method is not suitable for unfixed thin structural members and structural members aged for more than 1000 days, and the detection practicability is influenced. (4) An ultrasonic rebound synthesis method. The compressive strength of the concrete is estimated based on the hardness of the surface of the concrete member and the ultrasonic wave velocity in the concrete member. The detection method has the following defects: the test operation flow is complicated, the test influence factors are more, various test deviations are easy to generate, and the detection accuracy is influenced; the method is not suitable for unfixed thin structural members and structural members aged for more than 2000 days, and the detection practicability is influenced. (5) And (4) a drawing-out method. The compressive strength of the concrete is estimated according to the pulling-out force of the concrete member when the concrete member is damaged within the range of 30mm of the surface layer of the concrete member. The detection method has the following defects: the detection process needs complex drilling and groove grinding procedures, the thickness of the detected structural member is larger than 80mm, and for thin-layer concrete with the thickness of 10-80 mm, such as a ground surface layer, the thickness is generally 40-60 mm, so that the detection cannot be carried out, and the detection practicability is influenced. (6) A pull-off method. A core sample specimen having a diameter of 44mm and a depth of 44mm is drilled on the hardened concrete member, a pull-out test is performed by a device having an automatic clamping device, and the compressive strength of the concrete is estimated from the pull-out strength value of the core sample specimen. The detection method has the following defects: when the stress of the pull-off test piece is calculated, the diameter size of the mutually vertical position close to the fracture part of the test piece needs to be measured, and the accurate measurement is difficult due to the small diameter of the test piece, so that the detection accuracy is influenced; the detection of thin concrete with the thickness of 10mm-44mm cannot be realized, and the detection practicability is influenced.

In summary, when thin-layer concrete with the thickness of 10mm-80mm is detected, the above methods have various defects, so that innovative design is required.

Disclosure of Invention

The invention provides a side-pressing method for detecting the compressive strength of thin-layer concrete, which has strong practicability and accurate detection. The method can solve the problems of various existing methods when detecting the thin-layer concrete with the thickness of 10mm-80 mm.

The technical scheme adopted by the invention is as follows: a method for detecting the compressive strength of thin-layer concrete by a lateral compression method comprises the following steps: (1) drilling a core sample containing thin concrete at a proper position of the solid concrete; (2) polishing the end surface of the core sample to be flat, and cutting the side surface of the core sample into pressed surfaces symmetrically distributed on two sides of the core sample to prepare a side pressure test piece; (3) flatly placing a compression surface on one side of a side compression test piece on a pressure bearing plate of a press machine provided with a side compression head, and contacting thin-layer concrete on the compression surface on the other side with the side compression head; (4) starting a press machine to apply pressure until the lateral pressure of the thin-layer concrete of the lateral pressure test piece is damaged, and recording the maximum lateral pressure value; (5) and (4) estimating the compressive strength of the thin-layer concrete according to a conversion formula established between the compressive strength of the concrete and the lateral pressure value.

Further, the step (1) is to use solid concrete comprising a surface thin layer concrete and an inner base layer concrete; the diameter of the core sample is not less than 70mm, and the length of the core sample is not less than 50 mm; the longitudinal axis of the core sample is perpendicular to the thin concrete layer.

Further, the compression surface in the step (2) is rectangular, the long side is as long as the core sample and is parallel to the longitudinal axis of the core sample, the short side is perpendicular to the longitudinal axis of the core sample and is positioned in the plane of the end face, the length of the short side is 20mm or 30mm or 40mm, the length of the short side is not more than 1/3 of the diameter of the core sample, the length of the short side is not more than 2 times of the thickness of the thin-layer concrete, and the length of the short side is not less than the maximum aggregate particle size.

Further, the side pressure head in the step (3) is made of steel, and is formed by cutting a cylinder with the same diameter as the length of the short side of the pressure-bearing surface along a longitudinal axis, and the longitudinal section of the cylinder is vertical to the pressure-bearing surface and is in the same plane with the end face of one end of the thin-layer concrete of the side pressure test piece; the whole end face of one end of the side pressure head is in contact with the pressure-bearing surface of the side pressure test piece, and the other end of the side pressure head is installed on the press machine.

The invention has the beneficial effects that: (1) the concrete core sample is drilled to prepare a side pressure test piece, a press machine provided with a side pressure head is used for applying pressure until the thin-layer concrete of the side pressure test piece is damaged, the maximum side pressure value is recorded, the compressive strength of the thin-layer concrete is estimated according to a conversion formula established between the compressive strength of the concrete and the side pressure value, the design route is scientific, and the accuracy is high; (2) high-end detection equipment is not needed, and required instruments and equipment are convenient to purchase and process, so that the practicability is high; (2) the method solves various problems existing in the prior method when detecting the thin-layer concrete with the thickness of 10mm-80 mm.

Drawings

Fig. 1 is a schematic front view of the present invention in use.

Figure 2 is a schematic cross-sectional view of the present invention using D-D.

Figure 3 is a schematic cross-sectional view of the invention using a-a.

Fig. 4 is a schematic cross-sectional view of the present invention using B-B.

Figure 5 is a schematic cross-sectional view of the invention using C-C.

Detailed Description

The present invention is further illustrated by the following examples, which are not intended to limit the invention to these embodiments. It will be appreciated by those skilled in the art that the present invention encompasses all alternatives, modifications and equivalents as may be included within the scope of the claims.

Referring to fig. 1-5, a method for detecting the compressive strength of thin concrete by a lateral pressure method comprises the following steps: (1) drilling a core sample containing thin-layer concrete 5 at a proper position of the solid concrete; (2) polishing the end surface of the core sample to be flat, and cutting the side surface of the core sample into a pressed surface 7 and a pressed surface 8 which are symmetrically distributed on two sides of the core sample to prepare a side pressure test piece 3; (3) flatly placing a pressure surface 8 of a side pressure test piece 3 on a pressure bearing plate 4 of a press machine 1 provided with a side pressure head 2, and enabling a thin layer of concrete 5 of a pressure surface 7 to be in contact with the side pressure head 2; (4) starting a press machine 1 to apply pressure until the lateral pressure of the thin-layer concrete 5 of the lateral pressure test piece 3 is damaged, and recording the maximum lateral pressure value; (5) and (4) estimating the compressive strength of the thin-layer concrete 5 according to a conversion formula established between the compressive strength of the concrete and the lateral pressure value.

The solid concrete obtained in the step (1) of the embodiment comprises a surface thin layer concrete 5 and an internal base layer concrete 6, wherein the thickness of the thin layer concrete 5 is 40 mm; the diameter of the core sample is 100mm, and the length of the core sample is 100 mm; the longitudinal axis of the core sample is perpendicular to the thin concrete layer 5.

In this embodiment, the compression surface 7 and the compression surface 8 in step (2) are rectangular, the long side is 100mm and is parallel to the longitudinal axis of the core sample, the short side is perpendicular to the longitudinal axis of the core sample and is located in the plane of the end face, the length of the short side is 30mm, and the maximum aggregate particle size of the solid concrete is 20 mm.

In the embodiment, the side pressure head 2 in the step (3) is made of steel and is formed by cutting a cylinder with the diameter of 30mm along a longitudinal axis, and the longitudinal section of the cylinder is vertical to the compression surface 7 and is in the same plane with the end surface of one end of the thin-layer concrete 5 of the side pressure test piece 3; the whole terminal surface of side pressure head 2 one end contacts with receiving surface 7, and the other end is installed on press 1.

In this embodiment, the conversion formula is as follows:

Yi=AXi+B

wherein: yi is the compressive strength conversion value (MPa) of the ith thin-layer concrete 5 when the detection method is adopted; xi is the maximum lateral pressure value (N) applied to the ith concrete sheet 5 when tested by the present invention; A. and B is the regression coefficient of the regression equation.

Of course, the conversion formula of the concrete compressive strength and the lateral pressure value may be other than the above formula, and is not limited to the above formula.

Claims

1. A method for detecting the compressive strength of thin-layer concrete by a lateral compression method is characterized by comprising the following steps: the method comprises the following steps: (1) drilling a core sample containing thin concrete at a proper position of the solid concrete; (2) polishing the end surface of the core sample to be flat, and cutting the side surface of the core sample into pressed surfaces symmetrically distributed on two sides of the core sample to prepare a side pressure test piece; (3) flatly placing a compression surface on one side of a side compression test piece on a pressure bearing plate of a press machine provided with a side compression head, and contacting thin-layer concrete on the compression surface on the other side with the side compression head; (4) starting a press machine to apply pressure until the lateral pressure of the thin-layer concrete of the lateral pressure test piece is damaged, and recording the maximum lateral pressure value; (5) and (4) estimating the compressive strength of the thin-layer concrete according to a conversion formula established between the compressive strength of the concrete and the lateral pressure value.

2. The method for detecting the compressive strength of the thin-layer concrete by the lateral compression method according to claim 1, wherein the method comprises the following steps: the solid concrete in the step (1) comprises a surface thin layer concrete and an internal base layer concrete; the diameter of the core sample is not less than 70mm, and the length of the core sample is not less than 50 mm; the longitudinal axis of the core sample is perpendicular to the thin concrete layer.

3. The method for detecting the compressive strength of the thin-layer concrete by the lateral compression method according to claim 1, wherein the method comprises the following steps: the compression surface in the step (2) is rectangular, the long side is as long as the core sample and is parallel to the longitudinal axis of the core sample, the short side is perpendicular to the longitudinal axis of the core sample and is positioned in the plane of the end surface, the length of the short side is 20mm or 30mm or 40mm, the length of the short side is not more than 1/3 of the diameter of the core sample, the length of the short side is not more than 2 times of the thickness of the thin-layer concrete, and the length of the short side is not less than the maximum aggregate particle.

4. The method for detecting the compressive strength of the thin-layer concrete by the lateral compression method according to claim 1, wherein the method comprises the following steps: the side pressure head in the step (3) is made of steel and is formed by cutting a cylinder with the same diameter as the length of the short side of the pressure-bearing surface along a longitudinal axis, and the longitudinal section of the side pressure head is vertical to the pressure-bearing surface and is in the same plane with the end face of one end of the thin-layer concrete of the side pressure test piece; the whole end face of one end of the side pressure head is in contact with the pressure-bearing surface of the side pressure test piece, and the other end of the side pressure head is installed on the press machine.