CN113447398A

CN113447398A - Testing device and testing method for steel fiber concrete fluidity representation

Info

Publication number: CN113447398A
Application number: CN202110680656.2A
Authority: CN
Inventors: 刘军; 张宝东; 万璐; 邓永刚
Original assignee: Shenyang Ligong University
Current assignee: Shenyang Ligong University
Priority date: 2021-06-18
Filing date: 2021-06-18
Publication date: 2021-09-28

Abstract

The invention relates to the technical field of concrete materials, in particular to a steel fiber concrete fluidity testing device, a characterization mode and a testing method. The device comprises a bottom ring, a shearing ring, a pressure bearing plate, a precision pressure gauge I and a precision pressure gauge II; bottom ring one side is sealed, and one side opening, opening upwards place subaerial, shear ring both sides opening is located the bottom ring top, the bearing plate is located the shear ring top, precision pressure gauge I is connected with the top center of bearing plate is perpendicular, precision pressure gauge II and shear ring's lateral wall horizontal connection. The shear force data under the unit positive pressure of the steel fiber concrete is used for fitting the slope of the curve to represent the fluidity of the steel fiber concrete, so that the adverse effect caused by vibration is avoided, and the accuracy of a steel fiber framework in the steel fiber concrete is ensured; the pressure on the two precision pressure gauges can be directly read, and errors caused when the concrete slump is read are avoided.

Description

Testing device and testing method for steel fiber concrete fluidity representation

Technical Field

The invention relates to the technical field of concrete materials, in particular to a steel fiber concrete fluidity testing device, a characterization mode and a testing method.

Background

The flowability of fresh concrete is an important parameter for representing the workability of steel fiber concrete construction, the most widely used representing mode at present is to represent the slump, but the slump can be tested due to some defects, so that the testing accuracy is influenced: 1. in the process of filling the material into the slump cone for inserting and tamping, because the inserting and tamping degrees are different, the density of concrete can be influenced, and further the slump is influenced; 2. the state of the fibers randomly distributed in the concrete can be damaged in the vibrating process, and the slump obtained by testing cannot accurately represent the concrete with the steel fibers randomly distributed; 3. in the slump test process, finding the highest point of the concrete slump is difficult, and certain error exists in measuring the distance from the highest point slump to the top surface of the cylinder. Therefore, it is very important to design a testing method and a testing device which can avoid the influence of human factors and accurately test the flowability of the fresh concrete.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a method for representing the fluidity of steel fiber concrete by utilizing the shear force data fitting curve slope under the unit positive pressure of the steel fiber concrete, which can reduce the interference of external factors and improve the test precision of the fluidity of the steel fiber concrete.

In order to achieve the above object, the present invention provides a device for testing the fluidity of steel fiber concrete, the device comprising a bottom ring, a shear ring, a bearing plate, a precision pressure gauge i and a precision pressure gauge ii; bottom ring one side is sealed, and one side opening, opening upwards place subaerial, the equal opening in both sides about the shearing ring is located the bottom ring top, the bearing plate is located the shearing ring top, precision pressure gauge I is connected with the top center of bearing plate is perpendicular, precision pressure gauge II and the lateral wall horizontally connect of shearing ring.

In the above technical solution, further, the inner diameter of the bottom ring is 80-130 mm: the inner diameter of the shearing ring is 50-100mm, and the diameter of the pressure bearing plate is 40-90 mm; the inner diameter of the bottom ring is larger than the inner diameter of the shearing ring and the diameter of the bearing plate.

In the above technical scheme, further, the precision pressure gauge I and the precision pressure gauge II are both push-pull force gauges.

In the above technical scheme, further, the precision of the precision pressure gauge I is not lower than 0.1, and the precision of the precision pressure gauge II is not lower than 0.001.

In the above technical solution, furthermore, the side wall of the shear ring is from bottom to top 1/4.

In another aspect of the present invention, a method for improving the flowability of steel fiber concrete comprises the following steps:

filling steel fiber concrete which is just stirred into a bottom ring;

step two, mounting the shearing ring above the concrete, and filling the steel fiber concrete to be tested into the shearing ring;

thirdly, placing the bearing plate above the concrete in the shear ring;

step four, pressing the pressure bearing plate, and respectively recording the pressure values tested by the precision pressure gauge I and the precision pressure gauge II;

and fifthly, representing the fluidity of the concrete by calculating the slope of the shear force fitting curve under the unit positive pressure.

In the above technical solution, further, in the first step, the filling height of the concrete in the bottom ring is 3-5mm higher than the height of the bottom ring.

In the above technical scheme, further, in the second step, the concrete filling height in the shear ring is 3-5mm higher than the height of the shear ring.

The invention has the beneficial effects that:

compared with the prior art, the testing device has the advantages that the flowability of the steel fiber concrete is represented by fitting the slope of the curve through the shear stress data under the unit normal stress, so that the adverse effect caused by vibration is avoided, and the accuracy of the steel fiber framework in the steel fiber concrete is ensured; the pressure on the two precision pressure gauges can be directly read, and errors caused when the concrete slump is read are avoided.

Drawings

FIG. 1 is a schematic structural diagram of a testing apparatus according to the present invention;

FIG. 2 is a schematic structural view of a testing apparatus (front view) according to the present invention;

FIG. 3 is a schematic diagram of the structure of the testing device (left side view) of the present invention;

FIG. 4 is a schematic structural diagram of a testing apparatus (top view) according to the present invention;

FIG. 5 is a fitting graph of SF-0 positive pressure-shear force data;

FIG. 6 is a fitting graph of SF-4 positive pressure-shear force data;

FIG. 7 is a fitting graph of SF-8 positive pressure-shear force data;

FIG. 8 is a fitting graph of SF-12 positive pressure-shear force data;

FIG. 9 is a graph of steel fiber loading versus fitted slope;

FIG. 10 is a graph of steel fiber loading versus slump;

wherein: 1. a bottom ring; 2. a shear ring; 3. a pressure bearing plate; 4. a precision pressure gauge I; 5. and a precision pressure gauge II.

Detailed Description

A testing device for the fluidity representation of steel fiber concrete is structurally shown in figures 1-4 and comprises a bottom ring 1, a shearing ring 2, a bearing plate 3, a precision pressure gauge I4 and a precision pressure gauge II 5; the inner diameter of the bottom ring 1 is 115mm, the thickness is 2mm, the height is 28mm, one side of the bottom ring 1 is closed, one side is opened, and the opening is upwards placed on the ground; the inner diameter of the shearing ring 2 is 76mm, the thickness is 2mm, the height is 30mm, the upper side and the lower side of the shearing ring 2 are both opened and are positioned above the bottom ring 1; the diameter of the pressure bearing plate 3 is 65mm, the thickness is 4mm, and the pressure bearing plate is positioned above the shearing ring 2; the precision pressure gauge I4 is vertically connected with the center of the top of the pressure bearing plate 3 and used for testing positive pressure, and the precision is not lower than 0.1; and the precision pressure gauge II 5 is positioned on the side wall of the shearing ring 2 from bottom to top 1/4 and used for testing the shearing force, and the precision is not lower than 0.001.

The method for testing the fluidity of the steel fiber concrete by using the testing device comprises the following specific steps:

firstly, filling steel fiber concrete which is just stirred into a bottom ring 1, wherein the filling height of the concrete in the bottom ring 1 is 3mm higher than that of the bottom ring 1;

step two, installing the shearing ring 2 above concrete, filling steel fiber concrete to be tested into the shearing ring 2, wherein the filling height of the concrete in the shearing ring 2 is 4mm higher than that of the shearing ring 2;

thirdly, placing the pressure bearing plate 3 above the concrete in the shearing ring 2;

step four, pressing the pressure bearing plate 3, and respectively recording a positive pressure value tested by the precision pressure gauge I4 and a shear force value tested by the precision pressure gauge II 5;

C80 steel fiber concrete is adopted, the water-cement ratio is 0.2, the fiber mixing amount is 0, 0.5, 1 and 1.5 percent, and the fiber mixing amount is respectively marked as SF-0, SF-4, SF-8 and SF-12. The test data using the test apparatus of the present invention are shown in table 1:

TABLE 1

Fitting is carried out on the positive pressure-shearing force of the steel fiber concrete with different fiber doping amounts, the fitting result is shown in fig. 5-8, fitting slopes of data of the positive pressures of SF-0, SF-4, SF-8 and SF-12 and the shearing force are 14.28201, 20.92103, 24.83378 and 31.55175 respectively along with the increase of the steel fiber doping amount, and the concrete fluidity is reduced along with the increase of the steel fiber doping amount as can be seen from fig. 9. The reason is that as the mixing amount of the steel fibers increases, the fibers form a relatively stable framework in the concrete, a layer of water film exists on the surfaces of the fibers, so that the fluidity of the concrete is gradually reduced, and a larger positive pressure is required for the concrete to generate corresponding shearing force.

The slump cone tamping mode is used for testing, the test results are shown in the table 2,

TABLE 2

Test number	SF-0	SF-4	SF-8	SF-12
					Slump (cm)	18.7	16.8	14.5	8.8

As can be seen from FIG. 10, with the increase of the amount of the steel fibers, the slump is respectively 18.7cm, 16.8cm, 14.5cm and 8.8cm, the fluidity is reduced, and when the amount of the fibers is 1.5%, the concrete is dry in the blending process, and the slurry is less in the vibrating process.

Therefore, the test method is basically consistent with the slump cone inserting and tamping method in the prior art in the fluidity test results corresponding to different steel fiber mixing amounts, the test method is feasible, the fluidity of the steel fiber concrete is represented by the slope of the shear stress data fitting curve under unit normal stress, the adverse effect caused by vibration is avoided, and the accuracy of the steel fiber framework in the steel fiber concrete is ensured; the pressure on the two precision pressure gauges can be directly read, and errors caused when the concrete slump is read are avoided.

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. The utility model provides a testing arrangement of steel fibre concrete fluidity representation which characterized in that: the device comprises a bottom ring (1), a shearing ring (2), a pressure bearing plate (3), a precision pressure gauge I (4) and a precision pressure gauge II (5);

bottom ring (1) one side is sealed, and the other side opening, the opening upwards place subaerial, the equal opening in both sides about shearing ring (2) is located bottom ring (1) top, bearing plate (3) are located the shearing ring top, precision pressure gauge I (4) are connected with the top center of bearing plate (3) is perpendicular, precision pressure gauge II (5) and the lateral wall horizontally connect of shearing ring (2).

2. The apparatus of claim 1, wherein: the inner diameter of the bottom ring (1) is 80-130 mm: the inner diameter of the shearing ring (2) is 50-100mm, and the diameter of the pressure bearing plate (3) is 40-90 mm; the inner diameter of the bottom ring (1) is larger than that of the shearing ring (2) and larger than that of the bearing plate (3).

3. The apparatus of claim 1, wherein: and the precision pressure gauge I (4) and the precision pressure gauge II (5) are both push-pull force gauges.

4. The apparatus of claim 1, wherein: the precision of the precision pressure gauge I (4) is not lower than 0.1, and the precision of the precision pressure gauge II (5) is not lower than 0.001.

5. The apparatus of claim 1, wherein: the side wall of the shearing ring (2) is from bottom to top 1/4.

6. A method for testing the flowability of a steel fibre concrete using the device according to any one of claims 1 to 5, characterized in that: the method comprises the following steps:

firstly, filling steel fiber concrete which is just stirred into a bottom ring (1);

step two, installing the shearing ring (2) above the concrete, and filling the steel fiber concrete to be tested into the shearing ring (2);

thirdly, placing the pressure bearing plate (3) above the concrete in the shearing ring (2);

step four, pressing the pressure bearing plate (3), and respectively recording pressure values tested by the precision pressure gauge I (4) and the precision pressure gauge II (5);

7. The method of claim 6, wherein: in the first step, the filling height of the concrete in the bottom ring (1) is 3-5mm higher than that of the bottom ring (1).

8. The method of claim 6, wherein: in the second step, the filling height of the concrete in the shearing ring (2) is 3-5mm higher than that of the shearing ring (2).