CN102879266B - Method for testing uniaxial compression elasticity modulus of inorganic binder stabilizing material - Google Patents

Abstract

The invention discloses an indoor uniaxial compression elastic modulus test method and device for an inorganic binder stabilized material, belonging to the field of road engineering tests. In this method, a press is used to continuously and uniformly apply axial pressure to the cylindrical specimen of the inorganic binder stabilized material in a monotonous loading manner until the maximum force that the specimen can withstand is reached. The axial displacement sensor in the middle section of the side of the specimen measures the axial deformation of the middle section of the specimen, and determines the uniaxial compression elastic modulus value of the specimen according to the linear range of the stress-strain curve at the initial stage of loading. Compared with the existing test method, the indoor uniaxial compression elastic modulus test method of the inorganic binder stabilized material of the present invention has eliminated the adverse influence of the end face effect, has the characteristics of high measurement accuracy, good reproducibility, simple test, etc., and has good results. promotion and application value.

Description

Test method for uniaxial compression modulus of elasticity of materials stabilized by inorganic binders

technical field

The invention relates to the field of road engineering tests, in particular to an indoor uniaxial compression elastic modulus test method of an inorganic binder stabilized material.

Background technique

Inorganic binder stabilizing materials play a pivotal role in the construction of highway pavement in my country. As the main load-bearing layer of pavement structure, it determines the length of service life of pavement. The elastic modulus of the material is the main design parameter of the pavement structure, and the accuracy of its value has an important impact on the rationality and economy of the pavement structure design.

In the existing indoor compressive rebound modulus test method for inorganic binder stabilized materials, the axial deformation measurement point of the specimen is located on the top and bottom surfaces of the specimen, and the loading method of loading and unloading step by step is adopted. During the loading process, due to the influence of the end surface effect of the specimen, the measured axial deformation of the top and bottom surfaces of the specimen is greater than the actual axial deformation, so that the measured elastic modulus is smaller than the actual elastic modulus of the material. The loading method of step loading and unloading has poor repeatability of the test, and it is difficult to obtain true, reliable and consistent results.

How to quickly and accurately measure the true elastic modulus of inorganic binder-stabilized materials has become one of the focal issues to be solved urgently in the highway transportation industry.

Contents of the invention

The technical task of the present invention is to provide an indoor uniaxial compression modulus of elasticity test method for inorganic binder stabilized materials with high measurement accuracy, good reproducibility and easy operation, aiming at the deficiencies of the above-mentioned prior art. The compressive modulus of elasticity reflecting the real stress-strain relationship of the material stabilized by the inorganic binder can be obtained by using the test method.

The technical task of the present invention is realized in the following manner: the indoor uniaxial compression elastic modulus test method of inorganic binder stabilized material is characterized in that: the cylindrical specimen of inorganic binder stabilized material is continuously and uniformly loaded by a press Apply axial pressure continuously until the maximum force that the specimen can withstand is reached.

During the loading process, the axial deformation of the middle section of the specimen is measured with an axial displacement sensor installed in the middle section of the side of the cylindrical specimen, and the uniaxial compression elasticity of the specimen is determined according to the linear range of the stress-strain curve at the initial stage of loading. modulus value.

During the loading process, from the beginning of loading, it takes 30-60 seconds to reach the maximum force that the specimen can bear.

Three axial displacement sensors are placed in the middle of the side of the test piece through the fixture. The axial displacement sensors are perpendicular to the end face of the test piece and are arranged at equal intervals along the circumferential direction of the test piece (that is, every two axial displacement sensors are 120° apart). During the loading process Among them, the compression deformation of the middle section of the specimen falls within the measurement range of the axial displacement sensor, and the axial deformation of the middle section of the specimen is the average value of the compression deformation measured by the three axial displacement sensors.

The clamp is mainly composed of a rigid ring, a positioning bolt and a detachable screw rod.

The two rigid rings are respectively fixed on the middle section of the side of the specimen by positioning bolts, and the detachable screw is arranged between the two rigid rings to determine the initial distance between the two rigid rings, that is, the distance between the measuring points of the axial deformation of the specimen.

The end of the positioning bolt is preferably hemispherical, so as to prevent the bolt from penetrating into the test piece and affecting the test accuracy.

The initial distance between the two rigid rings, that is, the distance between the measurement points of the axial deformation of the specimen, is preferably 0.45 to 0.5 times the height of the specimen.

During the loading process, the microcomputer is used to automatically record the load and axial deformation of the specimen every 0.001s after the loading starts.

Determine its elastic modulus value according to the stress and strain at the maximum force of 0.25~0.35.

The ratio of the diameter to the height of the cylindrical test piece is 1:1.2~1:1.8, and the diameter of the test piece is 100mm~150mm.

Vibration or static pressure is used to form cylindrical specimens in the room, and the cylindrical specimens are prepared by drilling cores on site. The cylindrical specimens should meet the design strength requirements.

Compared with the prior art, the method for testing the uniaxial compression elastic modulus of the inorganic binder stabilized material of the present invention has the following outstanding beneficial effects:

1. The middle section deformation measurement method overcomes the end effect problem of the top and bottom surface deformation measurement of the existing test method, and obtains the compressive elastic modulus that reflects the real stress-strain relationship;

2. Replace the loading method of step-by-step loading and unloading in the existing test method with monotonous linear loading, which improves the measurement accuracy, good reproducibility of test results, easy operation and short test period.

Description of drawings

Accompanying drawing 1 is the structural representation of uniaxial compressive modulus of elasticity testing device of the present invention;

Accompanying drawing 2 is the installation front view of uniaxial compressive modulus of elasticity test sensor of the present invention;

Accompanying drawing 3 is the installation top view of sensor of uniaxial compressive modulus of elasticity test of the present invention;

Accompanying drawing 4 is load-strain graph in the embodiment of the present invention.

Detailed ways

The indoor uniaxial compression elastic modulus test method and device of the present invention will be described in detail with reference to the accompanying drawings and specific examples.

Example:

Test device:

As shown in Figure 1, the test devices and components involved in the test process are mainly loading equipment, loading plate 1, LVDT sensor 2, rigid ring 3, positioning bolt 4, detachable bolt 5 and control system.

experiment procedure:

a) Preparation and processing of test specimens

Use vibration or static pressure forming equipment to form or drill cores on site to prepare cylindrical specimens with a diameter of 100mm~150mm and a ratio of diameter to height of 1:1.2~1:1.8. After indoor or on-site curing, forming or core drilling specimens Need to meet the design strength requirements.

b) Strain sensor installation

As shown in Figures 2 and 3, the two rigid rings 3 are respectively fixed in the middle of the cylindrical specimen 6 by three positioning bolts 4, and the initial distance between the two rigid rings 3 (that is, the distance between the axial deformation measurement points) is 0.45~0.5 times the height of the piece. Three LVDT sensors 2 are installed on the side of the middle part of the test piece 6 through a rigid ring 3 . The LVDT sensors 2 are perpendicular to the end face of the test piece, and are arranged at equal intervals along the circumferential direction of the test piece (that is, every two are 120° apart). The end of the positioning bolt 4 is hemispherical to avoid penetrating into the inside of the test piece 6 . During the loading process, the average value of the compression deformation measured by the three LVDT sensors 2 is the average axial deformation of the middle section of the specimen , thus obtaining the strain ε.

A detachable bolt 5 is arranged between two rigid rings 3 . The length of the part of the detachable bolt 5 between the two rigid rings 3 is the same as the distance between the measurement points of the LVDT sensor 2 , which is used to determine the initial distance between the two rigid rings 3 .

c) Load application and data acquisition and processing

The loading plate 1 is made of a hard steel plate or a treated high-strength aluminum plate, and its diameter is equal to or greater than that of the test piece 6 . Two loading discs 1 are placed on the bottom and top of the test piece 6 respectively, and are used to transfer the load from the loading device to the test piece 6 . The loading equipment needs to adopt the monotonic loading method to apply the load continuously and evenly according to the set loading speed, and there must be no pause during the loading process.

Determination of loading speed: Estimate the maximum force that the specimen can withstand before loading, and then do a loading test to destroy the specimen within 30~60s, so as to determine the loading speed.

Data acquisition: During the test, the control system is controlled by a microcomputer, which records the load and axial deformation of the specimen every 0.001s after the start of loading, and draws the load-strain curve, as shown in Figure 4.

Based on the data recorded from the curves in Figure 4 the obtained and 0.3 corresponding strain .

Data processing: According to the collected data, the elastic modulus It can be calculated by the formula i.

Formula i:

: Elastic modulus of specimen, MPa;

: the maximum force that the specimen bears, N;

: The load reaches 0.3 The corresponding strain value when is dimensionless;

: diameter of specimen, mm.

Claims (8)

1. Inorganic binder stabilized material uniaxial compression modulus of elasticity test method is characterized in that: use press machine to apply axial pressure continuously and evenly by monotone loading mode to the inorganic binder stabilized material cylinder specimen until reaching the desired value of the specimen. the maximum force it can withstand, During the loading process, the axial deformation of the middle section of the specimen is measured with an axial displacement sensor installed in the middle section of the side of the cylindrical specimen, and the uniaxial compression elasticity of the specimen is determined according to the linear range of the stress-strain curve at the initial stage of loading. modulus value, The method for measuring the axial deformation of the middle section of the test piece: three axial displacement sensors are placed in the middle of the side of the test piece through the fixture, the axial displacement sensors are perpendicular to the end surface of the test piece, and are arranged at equal intervals along the circumferential direction of the test piece, During the loading process, the compression deformation of the middle section of the specimen falls within the measurement range of the axial displacement sensor, and the axial deformation of the middle section of the specimen is the average value of the compression deformation measured by the three axial displacement sensors. 2. Inorganic binder stabilized material uniaxial compression modulus of elasticity test method according to claim 1, is characterized in that, in the loading process, it takes 30 to 60 seconds to reach the maximum force that the test piece can bear from the beginning of loading . 3. Inorganic binder stable material uniaxial compression modulus of elasticity test method according to claim 1, is characterized in that, described clamp mainly is made of rigid ring, positioning bolt and detachable screw rod, The two rigid rings are respectively fixed on the middle section of the side of the specimen by positioning bolts, and the detachable screw is arranged between the two rigid rings to determine the initial distance between the two rigid rings. 4. Inorganic binder stabilized material uniaxial compression modulus of elasticity test method according to claim 3, is characterized in that, the initial spacing of two rigid rings is 0.45～0.5 times of specimen height. 5. Inorganic binder stabilized material uniaxial compression modulus of elasticity test method according to claim 1, is characterized in that, adopts microcomputer to automatically record the load that test piece bears every 0.001s after starting to load and produce in the loading process axial deformation. 6. Inorganic binder stabilized material uniaxial compression modulus of elasticity test method according to claim 1, is characterized in that, its modulus of elasticity value is determined by the stress and strain during the maximum force of 0.25 ~ 0.35. 7. inorganic binder stabilized material uniaxial compression modulus of elasticity test method according to claim 1, is characterized in that, the ratio of the diameter of described cylindrical specimen and height is 1:1.2～1:1.8, and specimen The diameter is 100mm~150mm. 8. inorganic binder stabilized material uniaxial compression modulus of elasticity test method according to claim 7, is characterized in that, indoor adopts vibration or static pressure molding cylinder specimen, prepares cylinder specimen by drilling core on the spot, cylinder The body test piece shall meet the design strength requirements.