CN116754377A - Loading method and loading device for restraining long-term deformation of lightweight aggregate under compression condition - Google Patents
Loading method and loading device for restraining long-term deformation of lightweight aggregate under compression condition Download PDFInfo
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- CN116754377A CN116754377A CN202310830070.9A CN202310830070A CN116754377A CN 116754377 A CN116754377 A CN 116754377A CN 202310830070 A CN202310830070 A CN 202310830070A CN 116754377 A CN116754377 A CN 116754377A
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- 238000011068 loading method Methods 0.000 title claims abstract description 53
- 230000007774 longterm Effects 0.000 title claims abstract description 37
- 230000000452 restraining effect Effects 0.000 title claims abstract description 25
- 230000006835 compression Effects 0.000 title claims abstract description 21
- 238000007906 compression Methods 0.000 title claims abstract description 21
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 44
- 229910052742 iron Inorganic materials 0.000 claims abstract description 22
- 238000005259 measurement Methods 0.000 claims abstract description 6
- 238000001514 detection method Methods 0.000 claims description 9
- 239000000463 material Substances 0.000 claims description 7
- 238000012360 testing method Methods 0.000 claims description 7
- 238000001035 drying Methods 0.000 claims description 6
- 238000009434 installation Methods 0.000 claims description 6
- 238000012216 screening Methods 0.000 claims description 4
- 238000013461 design Methods 0.000 claims description 3
- 230000005484 gravity Effects 0.000 claims description 3
- 239000002245 particle Substances 0.000 abstract description 10
- 229910000831 Steel Inorganic materials 0.000 description 8
- 239000010959 steel Substances 0.000 description 8
- 238000007790 scraping Methods 0.000 description 4
- 238000000034 method Methods 0.000 description 3
- 238000011161 development Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000010881 fly ash Substances 0.000 description 2
- 229910000639 Spring steel Inorganic materials 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
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- 201000010099 disease Diseases 0.000 description 1
- 208000037265 diseases, disorders, signs and symptoms Diseases 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 230000008014 freezing Effects 0.000 description 1
- 238000007710 freezing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/02—Details
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/02—Details
- G01N3/06—Special adaptations of indicating or recording means
- G01N3/062—Special adaptations of indicating or recording means with mechanical indicating or recording means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/0605—Mechanical indicating, recording or sensing means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/06—Indicating or recording means; Sensing means
- G01N2203/067—Parameter measured for estimating the property
- G01N2203/0682—Spatial dimension, e.g. length, area, angle
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Abstract
The invention provides a loading method and a loading device for restraining long-term deformation of lightweight aggregate under a compression condition, wherein the loading method mainly comprises the following steps: pouring the lightweight aggregate into a surrounding pressing cylinder, and pressurizing a pressure-bearing cylinder consisting of the surrounding pressing cylinder, a guide cylinder and a stamping die by utilizing a creep instrument consisting of a pressing plate, a nut, a screw rod and a spring to provide constraint, so that the lightweight aggregate particles are pressurized for a long time, and the long-term performance of the lightweight aggregate under constraint is obtained. The loading device mainly comprises a confining pressure cylinder, a guide cylinder, a stamping die, a strain conduction iron rod and a dial indicator, wherein the upper end of the confining pressure cylinder is connected with the lower end of the stamping die through the guide cylinder, the fixed plate is connected with the first mounting end of the strain conduction iron rod through the dial indicator, the second mounting end of the strain conduction iron rod is connected with a round hole threaded bolt, and the connecting hole of the upper pressing plate is connected with the base through a screw rod. The invention uses the average value of the four dial indicators as the judgment of whether the pressurization balance exists, so that the measured deformation data of the lightweight aggregate has less interference, and the measurement precision is ensured.
Description
Technical Field
The invention relates to the field of detection of mechanical properties of lightweight aggregates, in particular to a loading method and a loading device for restraining long-term deformation of the lightweight aggregates under a compression condition.
Background
The lightweight aggregate concrete has the advantages of light weight, high strength, excellent freezing resistance, good fire resistance and the like, and has good application prospect in large-span structures, ocean engineering and assembled buildings. The lightweight aggregate concrete is applied to a large-span bridge structure with relatively high constant load, so that the cross section size can be effectively reduced, the specific strength can be improved, and the span capacity can be increased. The creep of the lightweight aggregate concrete causes bridge deflection overrun, severe cracking and other variable diseases, and brings adverse effects on the service performance of the structure and also causes great potential safety hazard.
At present, the understanding of the long-term performance of lightweight aggregate concrete is still insufficient, the aggregate is one of the important components of the concrete, and the long-term deformation characteristic of the aggregate has obvious influence on the creep development rate and development trend of the concrete. The conventional creep theory holds that the aggregate of the common concrete has no viscoelastic characteristic and can play a role in restraining the deformation of surrounding cement stones, but the porous lightweight aggregate has unclear deformation rule, and the related test method is deficient and needs to be further researched.
The existing pressure-bearing cylinder method utilizes the pressure of a stamping die pressed into 20mm to obtain the cylinder pressure intensity of the lightweight aggregate particles, and cannot obtain the deformation rule of the lightweight aggregate particles pressed for a long time (180-360 days) under the constraint condition. Based on the method, the dial indicator and the strain conduction iron rod are respectively connected to the outer surfaces of the stamping die and the confining pressure cylinder, the cylinder pressure intensity test is carried out by adopting the device, the value of the strain change along with time when the lightweight aggregate particles are pressed under the constraint condition can be obtained, and therefore the long-term compression performance of the lightweight aggregate particles under the constraint condition is analyzed, and the materials and the dimensions of the device are provided.
Disclosure of Invention
Aiming at the problems existing in the prior art, the invention provides a loading method and a loading device for restraining long-term deformation of lightweight aggregate under a pressed condition, which mainly apply long-term and constant restraining pressure to the lightweight aggregate positioned on a confining pressure cylinder by utilizing a creep gauge consisting of a lower pressing plate, an upper pressing plate, a nut, a screw rod and a spring, and measure the deformation corresponding to the deformation of the piled lightweight aggregate by utilizing a dial gauge on the outer wall of the confining pressure cylinder to obtain the stress-strain relation of the lightweight aggregate under the long-term load, thereby obtaining the long-term performance of the lightweight aggregate particles pressed under the restraining condition.
The invention provides a loading method for restraining long-term deformation of lightweight aggregate under a compression condition, which comprises the following steps:
s1, preparing a lightweight aggregate sample:
s2, filling the lightweight aggregate obtained in the step S1 into a confining pressure cylinder, sequentially connecting the lightweight aggregate with the lower ends of a guide cylinder and a stamping die, and uniformly arranging four dial indicators and four strain conduction iron rods on the circumference of an outer ring of the confining pressure cylinder, thereby obtaining a bearing device;
s3, moving the bearing device obtained in the step S2 into the central part of the lower pressing plate, and contacting the lower surface of the upper pressing plate with the upper end of the stamping die through a nut, wherein the thickness t of the bottom plate in the stamping die 1 The range of the value of (2) is t 1 >6mm, thickness t of the side wall of the stamping die 5 The following should be satisfied:
wherein t is 5 Is the thickness of the side wall of the stamping die;is the stability factor of the stamping die; e (E) 1 Is the elastic modulus of the stamping die; d (D) 2 Is the outer diameter of the stamping die; f (f) s Is the barrel pressure strength of the lightweight aggregate;
s4, aligning the press machine with the center of the upper pressing plate, reading initial readings of a dial indicator, centering and loading the bearing device obtained in the step S2 at a constant speed of 300N-500N per second, and obtaining the variation of the dial indicator when the pressure is 20% of the pressure intensity of the lightweight aggregate cylinder, wherein the cylinder pressure intensity is generated by a confining pressure cylinder and a guide cylinder, and the thickness t of the second end of the confining pressure cylinder is equal to the thickness t of the second end of the confining pressure cylinder 3 The following expression should be satisfied:
wherein t is 3 The thickness of the second end of the confining pressure cylinder is the thickness; p (P) 1 The pressure value when the depth of the surrounding pressure cylinder for pressing the sample into the stamping die reaches 20 mm; p (P) 2 Is the gravity of the stamping die; d (D) 1 Is the outer diameter of the confining pressure cylinder; sigma is allowable stress of the selected material at the design temperature; s is the area of a stamping die bottom plate;
thickness t of the first end of the confining pressure cylinder 4 The following expression should be satisfied:
thickness t of bottom plate in the confining pressure cylinder 2 The range of the value of (2) is t 2 >10mm；
If the variation of each dial indicator is smaller than 10% of the average value of the variation of the four dial indicators, loading is continued, and step S5 is carried out; if the variation of one or more dial gauges is greater than or equal to 10% of the variation average value of the four dial gauges, unloading stress, and re-pressurizing after adjustment;
s5, continuously pressurizing the loaded bearing device in the step S4 to 40% of the cylinder pressure intensity of the lightweight aggregate, obtaining the variation of the dial indicators, and taking the average value of the variation of the four dial indicators at the moment as an initial deformation value under the condition that the load is 40% of the cylinder pressure intensity; then, screwing a nut at the joint of the screw rod and the upper pressing plate, unloading stress, recording the readings of four dial gauges, and if the deformation of any dial gauge is changed by more than 10%, re-pressurizing to 40% of the pressure intensity of the lightweight aggregate cylinder, and adjusting the tightness of the nut until the deformation of each dial gauge after unloading is changed by less than 10%;
s6, recording the reading of the dial indicator at the specified detection time, and calculating to obtain the strain epsilon of the lightweight aggregate a Drawing the time-epsilon of the lightweight aggregate a Curve, obtaining the long-term deformation rule of the lightweight aggregate under the constraint compression condition, wherein the strain epsilon of the lightweight aggregate a The expression of (2) is as follows:
wherein x is t When the pressure is increased to 40% of the pressure of the lightweight aggregate cylinder, the deformation average value measured by the four dial indicators is measured; t is t 6 The cylinder height of the confining pressure cylinder is the cylinder height of the confining pressure cylinder; x is x 1 Is the initial deformation value at 40% of the barrel pressure strength.
Preferably, the specific implementation process of the step S1 is as follows:
s11, screening a certain amount of lightweight aggregate with the nominal size of 10-20 mm, and putting the lightweight aggregate into a drying box for drying to constant;
s12, uniformly pouring the dried lightweight aggregate obtained in the step S11 from a position 50mm away from the upper end opening of the confining pressure cylinder until the lightweight aggregate at the upper end opening of the confining pressure cylinder forms a triangular cone shape, stopping pouring and strickling;
and S13, placing the confining pressure cylinder filled with the lightweight aggregate in the step S12 on a concrete test vibration table for vibration until the lightweight aggregate in the confining pressure cylinder is compacted.
Preferably, in the step S1, the volume content of the lightweight aggregate of the nominal size fraction of 10mm to 15mm accounts for 50% to 70% of the total volume of the lightweight aggregate.
It is preferable that the measurement time from centering loading to obtaining the initial deformation value is less than or equal to 30min in steps S4 and S5.
Preferably, in step S6, the detection duration is 360 days, and the specified detection times are 1, 3, 7, 14, 28, 45, 90, 120, 150, 180, 270 and 360 days, respectively.
The invention provides a loading device for a loading method for restraining long-term deformation of lightweight aggregate under a compression condition, which comprises a confining pressure cylinder, a guide cylinder, a stamping die, a strain conduction iron rod, a dial indicator, a lower pressing plate, an upper pressing plate, a screw rod, a spring and a base, wherein a fixed plate is arranged at the lower end of the outer wall of the confining pressure cylinder, a round hole threaded bolt is arranged at the upper end of the outer wall of the stamping die, the upper end of the confining pressure cylinder is connected with the lower end of the guide cylinder, the upper end of the guide cylinder is connected with the lower end of the stamping die, a hole on the fixed plate is connected with the first mounting end of the dial indicator, the second mounting end of the dial indicator is connected with the first mounting end of the strain conduction iron rod, and the second mounting end of the strain conduction iron rod is connected with the round hole threaded bolt; the first installation end of the screw rod is connected with the connecting hole of the upper pressing plate through a nut and a nut gasket, the second installation end of the screw rod sequentially penetrates through the connecting hole of the lower pressing plate and the spring to be connected with the base, and the spring is located between the lower pressing plate and the base.
Preferably, the central axes of the confining pressure cylinder, the guide cylinder, the stamping die, the upper pressure plate, the lower pressure plate and the base are on the same straight line, and the central axes of the screw rod and the spring are on the same straight line.
Preferably, the diameter d of the wire rod 2 The following should be satisfied:
wherein d 2 Is the diameter of the wire rod; e (E) 2 Is the elastic modulus of the screw rod.
Compared with the prior art, the invention has the following advantages:
1. the invention provides the size requirements of a stamping die, a spring and a screw rod required by long-term compression performance of lightweight aggregate under constraint conditions, the constraint conditions are provided by pressurizing a pressure-bearing cylinder consisting of a confining pressure cylinder, a guide cylinder and the stamping die by utilizing a creep meter consisting of a lower pressing plate, an upper pressing plate, a nut, the screw rod and the spring, and the lightweight aggregate particles are pressurized for 180-360 days, so that the long-term compression performance of the lightweight aggregate particles under constraint conditions can be obtained.
2. The invention provides the lower limit chemical index of parameters such as the thickness of the bottom plate in the stamping die, the thickness of the bottom plate in the confining pressure cylinder, the thickness of the second end of the confining pressure cylinder, the thickness of the side wall of the stamping die and the like for guaranteeing the rigidity of the long-term loading device, and the device size matched with the lightweight aggregate to be measured can be designed through simple calculation, so that the measurement precision is effectively guaranteed.
3. According to the invention, the four dial indicators are erected on the outer side of the pressure-bearing cylinder, and the displacement of instruments such as a universal tester is not adopted, so that the average value of the four dial indicators can be used for judging whether the pressure balance is achieved, and the measured deformation data of the lightweight aggregate in the cylinder has less interference and high precision.
Drawings
FIG. 1 is a block diagram of a loading device for restraining long-term deformation of lightweight aggregate under compression according to the present invention;
FIG. 2 is a front view of a loading device for restraining long-term deformation of lightweight aggregate under compression in accordance with the present invention;
FIGS. 3 a-3 c are block diagrams of a confining pressure cylinder, a guide cylinder and a stamping die in a loading device for restraining long-term deformation of lightweight aggregate under pressure according to the invention;
FIG. 4 is a flow chart of the loading method of the present invention for restraining long-term deformation of lightweight aggregate under compression.
The main reference numerals:
the device comprises a confining pressure cylinder 1, a guide cylinder 2, a stamping die 3, a fixing plate 4, a round hole threaded bolt 5, a strain conduction iron rod 6, a dial indicator 7, a lower pressing plate 8, an upper pressing plate 9, a nut 10, a screw rod 11, a spring 12 and a base 13.
Detailed Description
In order to make the technical content, the structural features, the achieved objects and the effects of the present invention more detailed, the following description will be taken in conjunction with the accompanying drawings.
The loading device for restraining long-term deformation of the lightweight aggregate under the compression condition is shown in fig. 1, and comprises a confining pressure cylinder 1, a guide cylinder 2, a stamping die 3, a strain conduction iron rod 6, a dial indicator 7, a lower pressure plate 8, an upper pressure plate 9, a screw rod 11, a spring 12 and a base 13, wherein an inner boss is arranged at the lower end of the guide cylinder 2 as shown in fig. 3b, an outer boss is arranged at the upper end of the confining pressure cylinder 1 as shown in fig. 3c, and the inner boss is connected with the outer boss.
As shown in fig. 2, the lower end of the outer wall of the confining pressure cylinder 1 is provided with a fixing plate 4, the upper end of the outer wall of the stamping die 3 is provided with a round hole threaded bolt 5, the upper end of the confining pressure cylinder 1 is connected with the lower end of the guide cylinder 2, the upper end of the guide cylinder 2 is sleeved with the lower end of the stamping die 3, a hole on the fixing plate 4 is connected with the first mounting end of the dial indicator 7, the second mounting end of the dial indicator 7 is connected with the first mounting end of the strain conduction iron rod 6, and the second mounting end of the strain conduction iron rod 6 is connected with the round hole threaded bolt 5.
The first installation end of the screw rod 11 is connected with the connecting hole of the upper pressing plate 9 through a nut 10 and a nut gasket, the second installation end of the screw rod 11 sequentially penetrates through the connecting hole of the lower pressing plate 8 and a spring 12 to be connected with a base 13, the spring 12 is positioned between the lower pressing plate 8 and the base 13, and the spring 12 is a square surrounded by 2 multiplied by 2.
In order to ensure that the whole loading device carries out long-term constraint loading on the lightweight aggregate, the central axes of the confining pressure cylinder 1, the guide cylinder 2, the stamping die 3, the upper pressure plate 9, the lower pressure plate 8 and the base 13 are ensured to be on the same straight line, and the central axes of the screw rod 11 and the spring 12 are ensured to be on the same straight line.
Under test load, the tensile stress of the screw rod 11 should not be greater than 30% of the material yield point, the working pressure of the spring 12 should not exceed 80% of the allowable limit load, and the compression deformation of the spring 12 should not be less than 20mm when working, the diameter d of the screw rod 11 2 The following should be satisfied:
wherein d 2 For screw 11Diameter; e (E) 2 The elastic modulus of the screw 11.
The dimensions of the spring 12 should satisfy the following expression:
wherein C is the coiling ratio of the spring 12; d is the diameter of the spring 12; f is the amount of deflection of the spring 12 under the operating load; τ is the shear stress; [ tau ] is allowable shear stress; g is shear elastic modulus; n is the effective number of turns of the spring 12; d is the center diameter of the spring 12.
In another aspect of the present invention, there is provided a loading method for restraining long-term deformation of lightweight aggregate under compression, as shown in fig. 4, pouring the screened and dried lightweight aggregate into a confining pressure cylinder 1 with a cylinder bottom, then assembling the confining pressure cylinder 1 with other parts of a measuring device in sequence, pressurizing by consisting of a lower pressure plate 8, an upper pressure plate 9, a nut 10, a screw rod 11 and a spring 12, and then collecting and analyzing data, comprising the following specific implementation steps:
s1, preparing a lightweight aggregate sample:
s11, screening 5L of lightweight aggregate samples with the nominal size of 10-20 mm, and in a preferred embodiment, allowing the fly ash ceramsite to be in the nominal size of 10-15 mm, and placing the ultra-lightweight ceramsite in a drying box to be dried to constant according to the nominal size of 5-10 mm or 5-20 mm. Specifically, the volume content of the lightweight aggregate sample with the nominal size of 10 mm-15 mm accounts for 50% -70% of the total volume.
S12, pouring the dried lightweight aggregate sample obtained in the step S11 from a position 50mm away from the upper end opening of the confining pressure cylinder 1 or symmetrically by adopting a standard funnel, so that the lightweight aggregate sample naturally falls down and cannot collide with the confining pressure cylinder 1 until the lightweight aggregate sample at the upper end opening of the confining pressure cylinder 1 forms a triangular cone shape, stopping pouring and scraping the lightweight aggregate sample from the center to two sides along the edge of the confining pressure cylinder 1 by using a ruler, and filling the surface concave positions with lightweight aggregate with smaller particle size.
And S13, placing the confining pressure cylinder 1 filled with the lightweight aggregate sample in the step S12 on a concrete test vibration table for vibration until the lightweight aggregate sample in the confining pressure cylinder is compacted. Specifically, the confining pressure cylinder 1 is used for loading the lightweight aggregate sample to the position higher than the port of the confining pressure cylinder 1, the lightweight aggregate sample is placed on a concrete test vibration table to vibrate for 3s, the lightweight aggregate sample is then placed on the vibration table to vibrate for 5s higher than the port of the confining pressure cylinder 1, and the port of the Ji Weiya cylinder 1 is used for scraping or filling the lightweight aggregate sample.
S2, connecting the confining pressure cylinder 1 filled with the lightweight aggregate sample in the step S13 with the guide cylinder 2 and the stamping die 3 in sequence, and uniformly arranging four dial indicators 7 and four strain conduction iron rods 6 on the circumference of the outer ring of the confining pressure cylinder 1, thereby obtaining the bearing device.
S3, the bearing device obtained in the step S2 is moved into the central part of the lower pressing plate 8, and the lower surface of the upper pressing plate 9 is contacted with the upper end of the stamping die 3 through the nut 10, as shown in FIG. 3a, wherein the thickness t of the bottom plate in the stamping die 3 1 The range of the value of (2) is t 1 >Thickness t of side wall of stamping die 3 of 6mm 5 The following should be satisfied:
wherein t is 5 Is the thickness of the side wall of the stamping die 3;is the stability factor of the stamping die 3; e (E) 1 The elastic modulus of the stamping die 3; d (D) 2 Is the outer diameter of the stamping die 3; f (f) s Is the barrel pressure strength of the lightweight aggregate.
S4, aligning the press machine with the center of the upper pressing plate 9, reading the initial 7 readings of the dial indicator, centering and loading the bearing device obtained in the step S2 at a constant speed of 300N-500N per second, and reading the readings of the dial indicator 7 when the pressure is increased to 20% of the pressure intensity of the lightweight aggregate cylinderSubtracting the initial 7 readings of the dial indicator to obtain the variation of the dial indicator 7, wherein the cylinder pressure strength is generated by the confining pressure cylinder and the guide cylinder, the cylinder pressure strength is one of structures of the device for generating constraint conditions, and the thickness t of the second end of the confining pressure cylinder 1 3 The following expression should be satisfied:
wherein t is 3 Is the thickness of the second end of the confining pressure cylinder 1; p (P) 1 The pressure value when the depth of the surrounding pressure cylinder 1 for pressing the sample into the stamping die 3 reaches 20 mm; p (P) 2 Is the gravity of the stamping die 3; d (D) 1 Is the outer diameter of the confining pressure cylinder 1; sigma is allowable stress of the selected material at the design temperature; s is the area of the bottom plate of the stamping die 3.
Thickness t of first end of confining pressure cylinder 1 4 The following expression should be satisfied:
as shown in FIG. 3c, the thickness t of the bottom plate in the confining pressure cylinder 1 2 The range of the value of (2) is t 2 >10mm。
If the reading variation of each dial indicator 7 is less than 10% of the variation average value of the four dial indicators 7, loading is continued, and step S5 is performed; and if the variation of one or more dial indicators 7 is greater than or equal to 10% of the variation average value of the four dial indicators 7, unloading the stress, readjusting and pressurizing.
S5, continuously pressurizing the loaded bearing device in the step S4 to 40% of the pressure intensity of the lightweight aggregate cylinder, reading the readings of the four dial indicators 7, subtracting the readings of the four dial indicators from the initial 7 readings of the dial indicators to obtain the variation of the dial indicators 7, and taking the average value of the variation of the four dial indicators 7 at the moment as the initial deformation value under the condition that the load is 40% of the pressure intensity of the cylinder; and then the nut 10 at the joint of the screw rod 11 and the upper pressing plate 9 is screwed down, the stress is unloaded, the readings of the four dial indicators 7 are recorded, if the deformation of any dial indicator 7 is changed by more than 10%, the pressure of the lightweight aggregate cylinder is increased to 40%, and the tightness of the nut 10 is adjusted until the deformation of each dial indicator 7 is changed by less than 10% after unloading.
Specifically, in the loading method of the present invention, the measurement time from centering loading to obtaining the initial deformation value is less than or equal to 30 minutes.
S6, recording readings of dial indicators 7 in 1, 3, 7, 14, 28, 45, 90, 120, 150, 180, 270 and 360 days, and calculating to obtain the strain epsilon of the lightweight aggregate sample a The time-epsilon of the lightweight aggregate sample is plotted a Curve to obtain the long-term deformation rule, strain epsilon, of the lightweight aggregate sample under constraint and compression conditions a The expression of (2) is as follows:
wherein x is t When the pressure is increased to 40% of the pressure of the lightweight aggregate cylinder, the deformation average value measured by the four dial indicators 7 is measured; t is t 6 Is the cylinder height of the confining pressure cylinder 1; x is x 1 Is the initial deformation value at 40% of the barrel pressure strength.
Further, the detection duration was 360 days.
The following describes a loading method and apparatus for restraining long-term deformation of lightweight aggregate under a compression condition with reference to examples:
in this embodiment, as shown in fig. 3, specific dimensions of each part in the loading device are: the inner diameter of the base of the confining pressure cylinder 1 is 135mm, the inner diameter height is 8mm, the outer diameter is 160mm, the outer diameter height is 20mm, and the steel is Q235; the inner diameter of the confining pressure cylinder 1 is 115mm, the outer diameter is 135mm, the height is 100mm, and the seamless steel tube is made of Q235; the inner diameter of the guide cylinder 2 is 115mm, the outer diameter is 135mm, the height is 100mm, and the seamless steel tube is made of Q235; the inner diameter of the stamping die 3 is 93mm, the inner diameter is 128mm, the outer diameter is 113mm, the outer diameter is 140mm, and the steel material is Q345; the length of the fixing plate 4 with the dial indicator screw hole is 55mm, the width is 30mm, the height is 5mm, and the steel block is made of Q235; the threaded bolt 5 with holes adopts a cross groove circle with the length of 15mm and the diameter of 4mmThe top of the column head screw is welded with a steel small ring; the length of the strain conduction iron rod 6 is 80mm, and the diameter is 10mm; the height of the dial indicator 7 is 130mm, and the width is 57mm; screw rod 11 is a screw steel of 700mm in height and 25mm in cross-section diameter of common HRB 335; the nut 10 is a nut matched with the screw rod 11; spring 12 is made of spring steel 60CrMnA, the center diameter D is 120mm, and the free height H 0 275mm, total number of turns n 1 Number of support turns n=6 z Effective turns n=4.5, =1.5; the upper pressing plate 9, the lower pressing plate 8 and the base 13 are made of steel with the side length of 250mm, the thickness of 15mm and the material quality of Q235.
The loading method of the specific embodiment is realized as follows:
s1, preparing a lightweight aggregate sample:
s11, screening 5L of lightweight aggregate samples with the nominal size of 10-20 mm, wherein the fly ash ceramsite is allowed to be in the nominal size of 10-15 mm, and the ultra-lightweight ceramsite is placed into a drying box to be dried to constant according to the nominal size of 5-10 mm or 5-20 mm. Wherein, the volume content of the lightweight aggregate sample with the nominal size of 10 mm-15 mm accounts for 50-70% of the total volume.
S12, uniformly pouring the dried lightweight aggregate sample obtained in the step S11 from a position 50mm away from the upper end cylinder opening of the confining pressure cylinder 1 by using a sampling spoon, allowing the lightweight aggregate sample to naturally fall down, and preventing the lightweight aggregate sample from colliding with the confining pressure cylinder 1 until the lightweight aggregate sample at the upper end cylinder opening of the confining pressure cylinder 1 forms a triangular cone shape, stopping pouring, scraping the lightweight aggregate sample from the center to two sides along the edge of the confining pressure cylinder 1 by using a straight ruler, and filling the surface concave positions with lightweight aggregate with smaller particle size.
S13, filling the lightweight aggregate sample with the confining pressure cylinder 1 to be higher than the port of the confining pressure cylinder 1, placing the lightweight aggregate sample on a concrete test vibration table to vibrate for 3S, then filling the lightweight aggregate sample to be higher than the port of the confining pressure cylinder 1, placing the lightweight aggregate sample on the vibration table to vibrate for 5S, and scraping or filling the lightweight aggregate sample with the port of the Ji Weiya cylinder 1.
S2, connecting the confining pressure cylinder 1 filled with the lightweight aggregate sample in the step S13 with the guide cylinder 2 and the stamping die 3 in sequence, and uniformly arranging four pairs of dial indicators 7 and strain conducting iron rods 6 on the circumference of the outer ring of the confining pressure cylinder 1, thereby obtaining the bearing device.
The upper end of a confining pressure cylinder 1 is sleeved with the lower end of a guide cylinder 2, the confining pressure cylinder 1 and a strain conduction iron rod 6 are connected to the conduction iron rod screw hole of the confining pressure cylinder 1 through a bolt 5 with round holes, a dial indicator 7 is fixedly connected with the stamping die 3 through the dial indicator screw hole of the stamping die 3 and a fixed plate 4, the stamping die 3 is embedded into the guide cylinder 2 along the inner surface of a loading device, the scale mark of the stamping die 3 is aligned with the upper edge of the guide cylinder 2, the lower end of the dial indicator 7 is connected with the first end of the strain conduction iron rod 6, a lower pressing plate 8 is arranged at the upper end of a base 13 with 4 screw rods 11 and 25 springs 12 through holes corresponding to the screw rods, an upper pressing plate 9 is arranged at the upper end of the loading device through holes corresponding to the screw rods 11, spring gaskets with slightly larger inner diameters than the holes are arranged at the upper ends of the holes corresponding to the screw rods 11, and nuts 10 corresponding to the screw rods 11 are arranged on the spring gaskets.
And S3, moving the bearing device obtained in the step S2 into the central part of the lower pressing plate 8 through a handle, and contacting the lower surface of the upper pressing plate 9 with the upper end of the stamping die 3 through a nut 10.
S4, aligning the press to the center of the upper pressing plate 9, reading initial 7 readings of the dial indicators, centering and loading the bearing device obtained in the step S2 at a constant speed of 300N-500N per second, when the pressure is increased to 20% of the pressure intensity of the lightweight aggregate cylinder, reading the readings of the dial indicators 7, subtracting the readings from the initial 7 readings of the dial indicators, and if the variation of each dial indicator 7 is smaller than 10% of the variation average value of the four dial indicators 7 at the moment, continuing loading, and carrying out the step S5; if the variation of one or more dial indicators 7 is greater than or equal to 10% of the variation mean value of four dial indicators 7, unloading the stress, readjusting and pressurizing.
S5, continuously pressurizing the loaded bearing device obtained in the step S4 to 40% of the pressure intensity of the lightweight aggregate cylinder, reading the readings of the four dial indicators 7, subtracting the readings of the four dial indicators from the initial 7 readings of the dial indicators to obtain the variation of the dial indicators 7, and taking the average value of the variation of the four dial indicators 7 as the initial deformation value under the condition that the load is 40% of the pressure intensity of the cylinder; and then the nut 10 at the joint of the screw rod 11 and the upper pressing plate 9 is screwed down, the stress is unloaded, the readings of the four dial indicators 7 are recorded, if the deformation of any dial indicator 7 is changed by more than 10%, the pressure is increased again to 40% of the pressure intensity of the lightweight aggregate cylinder, and the tightness of the nut 10 is adjusted until the deformation of each dial indicator 7 is changed by less than 10% after unloading.
Specifically, in this implementation, the measurement time from centering loading to obtaining the initial deformation value is less than or equal to 30 minutes.
S6, in the specific embodiment, the detection time is 360 days, so that readings of dial indicators 7 in 1, 3, 7, 14, 28, 45, 90, 120, 150, 180, 270 and 360 days are recorded respectively, and the strain epsilon of the lightweight aggregate sample is calculated a The time-strain ε of the lightweight aggregate sample is shown a And (5) obtaining a long-term deformation rule of the lightweight aggregate sample under the constraint compression condition by the curve.
The above examples are only illustrative of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention, and various modifications and improvements made by those skilled in the art to the technical solution of the present invention should fall within the scope of protection defined by the claims of the present invention without departing from the spirit of the present invention.
Claims (8)
1. A loading method for restraining long-term deformation of lightweight aggregate under a pressurized condition, comprising the steps of:
s1, preparing a lightweight aggregate sample:
s2, filling the lightweight aggregate obtained in the step S1 into a confining pressure cylinder, sequentially connecting the lightweight aggregate with the lower ends of a guide cylinder and a stamping die, and uniformly arranging four dial indicators and four strain conduction iron rods on the circumference of an outer ring of the confining pressure cylinder, thereby obtaining a bearing device;
s3, moving the bearing device obtained in the step S2 into the central part of the lower pressing plate, and contacting the lower surface of the upper pressing plate with the upper end of the stamping die through a nut, wherein the thickness t of the bottom plate in the stamping die 1 The range of the value of (2) is t 1 >6mm, thickness t of the side wall of the stamping die 5 The following should be satisfied:
wherein t is 5 Is a ramThickness of the die sidewall;is the stability factor of the stamping die; e (E) 1 Is the elastic modulus of the stamping die; d (D) 2 Is the outer diameter of the stamping die; f (f) s Is the barrel pressure strength of the lightweight aggregate; s is the area of a stamping die bottom plate;
s4, aligning the press machine with the center of the upper pressing plate, reading initial readings of a dial indicator, centering and loading the bearing device obtained in the step S2 at a constant speed of 300N-500N per second, and obtaining the variation of the dial indicator when the pressure is 20% of the pressure intensity of the lightweight aggregate cylinder, wherein the cylinder pressure intensity is generated by a confining pressure cylinder and a guide cylinder, and the thickness t of the second end of the confining pressure cylinder is equal to the thickness t of the second end of the confining pressure cylinder 3 The following expression should be satisfied:
wherein t is 3 The thickness of the second end of the confining pressure cylinder is the thickness; p (P) 1 The pressure value when the depth of the surrounding pressure cylinder for pressing the sample into the stamping die reaches 20 mm; p (P) 2 Is the gravity of the stamping die; d (D) 1 Is the outer diameter of the confining pressure cylinder; sigma is allowable stress of the selected material at the design temperature; s is the area of a stamping die bottom plate;
thickness t of the first end of the confining pressure cylinder 4 The following expression should be satisfied:
thickness t of bottom plate in the confining pressure cylinder 2 The range of the value of (2) is t 2 >10mm；
If the variation of each dial indicator is smaller than 10% of the average value of the variation of the four dial indicators, loading is continued, and step S5 is carried out; if the variation of one or more dial gauges is greater than or equal to 10% of the variation average value of the four dial gauges, unloading stress, and re-pressurizing after adjustment;
s5, continuously pressurizing the loaded bearing device in the step S4 to 40% of the cylinder pressure intensity of the lightweight aggregate, obtaining the variation of the dial indicators, and taking the average value of the variation of the four dial indicators at the moment as an initial deformation value under the condition that the load is 40% of the cylinder pressure intensity; then, screwing a nut at the joint of the screw rod and the upper pressing plate, unloading stress, recording the readings of four dial gauges, and if the deformation of any dial gauge is changed by more than 10%, re-pressurizing to 40% of the pressure intensity of the lightweight aggregate cylinder, and adjusting the tightness of the nut until the deformation of each dial gauge after unloading is changed by less than 10%;
s6, recording the reading of the dial indicator at the specified detection time, and calculating to obtain the strain epsilon of the lightweight aggregate a The time-strain epsilon of the lightweight aggregate is plotted a Curve, obtaining the long-term deformation rule of the lightweight aggregate under the constraint compression condition, wherein the strain epsilon of the lightweight aggregate a The expression of (2) is as follows:
wherein x is t When the pressure is increased to 40% of the pressure of the lightweight aggregate cylinder, the deformation average value measured by the four dial indicators is measured; t is t 6 The cylinder height of the confining pressure cylinder is the cylinder height of the confining pressure cylinder; x is x 1 Is the initial deformation value at 40% of the barrel pressure strength.
2. The loading method for restraining long-term deformation of lightweight aggregate under pressure according to claim 1, wherein the specific sub-steps of step S1 are:
s11, screening a certain amount of lightweight aggregate with the nominal size of 10-20 mm, and putting the lightweight aggregate into a drying box for drying to constant;
s12, uniformly pouring the dried lightweight aggregate obtained in the step S11 from a position 50mm away from the upper end opening of the confining pressure cylinder until the lightweight aggregate at the upper end opening of the confining pressure cylinder forms a triangular cone shape, stopping pouring and strickling;
and S13, placing the confining pressure cylinder filled with the lightweight aggregate in the step S12 on a concrete test vibration table for vibration until the lightweight aggregate in the confining pressure cylinder is compacted.
3. The loading method for restraining long-term deformation of a lightweight aggregate under a pressurized condition according to claim 1 or 2, wherein in step S1, the volume content of the lightweight aggregate of 10mm to 15mm nominal size fraction is 50% to 70% of the total volume of the lightweight aggregate.
4. The loading method for restraining long-term deformation of lightweight aggregate under pressure according to claim 1, wherein the measurement time from centering loading to obtaining initial deformation value is less than or equal to 30min in steps S4 and S5.
5. The loading method for restraining long-term deformation of lightweight aggregate under pressure according to claim 1, wherein in step S6, the detection period is 360 days, and the prescribed detection time is 1 day, 3 days, 7 days, 14 days, 28 days, 45 days, 90 days, 120 days, 150 days, 180 days, 27 days, or 360 days, respectively.
6. A loading device for restraining a long-term deformation of lightweight aggregate under a compression condition according to one of claims 1 to 5, comprising a confining pressure cylinder, a guide cylinder, a stamping die, a strain conduction iron rod, a dial indicator, a lower pressing plate, an upper pressing plate, a screw rod, a spring and a base, wherein a fixed plate is arranged at the lower end of the outer wall of the confining pressure cylinder, a round hole threaded bolt is arranged at the upper end of the outer wall of the stamping die, the upper end of the confining pressure cylinder is connected with the lower end of the guide cylinder, the upper end of the guide cylinder is connected with the lower end of the stamping die, a hole on the fixed plate is connected with the first mounting end of the dial indicator, the second mounting end of the dial indicator is connected with the first mounting end of the strain conduction iron rod, and the second mounting end of the strain conduction iron rod is connected with the round hole threaded bolt; the first installation end of the screw rod is connected with the connecting hole of the upper pressing plate through a nut and a nut gasket, the second installation end of the screw rod sequentially penetrates through the connecting hole of the lower pressing plate and the spring to be connected with the base, and the spring is located between the lower pressing plate and the base.
7. The loading device for the loading method for restraining the long-term deformation of the lightweight aggregate under the pressurized condition according to claim 6, wherein the central axes of the confining pressure cylinder, the guide cylinder, the press die, the upper press plate, the lower press plate and the base are on the same straight line, and the central axes of the screw rod and the spring are on the same straight line.
8. The loading device for restraining a loading method of long-term deformation of a lightweight aggregate under pressure according to claim 6, wherein the diameter d of the wire rod 2 The following should be satisfied:
wherein d 2 Is the diameter of the wire rod; e (E) 2 Is the elastic modulus of the screw rod.
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| CN202310830070.9A CN116754377A (en) | 2023-07-07 | 2023-07-07 | Loading method and loading device for restraining long-term deformation of lightweight aggregate under compression condition |
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| CN202310830070.9A CN116754377A (en) | 2023-07-07 | 2023-07-07 | Loading method and loading device for restraining long-term deformation of lightweight aggregate under compression condition |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117538154A (en) * | 2023-11-15 | 2024-02-09 | 东北石油大学 | 3D printing proportioning cement stone ultra-early short-term creep test method based on pressing method |
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- 2023-07-07 CN CN202310830070.9A patent/CN116754377A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117538154A (en) * | 2023-11-15 | 2024-02-09 | 东北石油大学 | 3D printing proportioning cement stone ultra-early short-term creep test method based on pressing method |
| CN117538154B (en) * | 2023-11-15 | 2024-04-30 | 东北石油大学 | 3D printing proportioning cement stone ultra-early short-term creep test method based on pressing method |
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