CN111487155B - Method for testing frost heaving stress resolution effect of asphalt mixture communicated pores - Google Patents
Method for testing frost heaving stress resolution effect of asphalt mixture communicated pores Download PDFInfo
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- CN111487155B CN111487155B CN202010268206.8A CN202010268206A CN111487155B CN 111487155 B CN111487155 B CN 111487155B CN 202010268206 A CN202010268206 A CN 202010268206A CN 111487155 B CN111487155 B CN 111487155B
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Abstract
The invention provides a method for testing the resolution effect of communicated pores of an asphalt mixture on frost heaving stress, which comprises the following steps: 1. scanning a test piece by using a CT (computed tomography) instrument, reconstructing a three-dimensional connected pore structure of the test piece, and extracting the number m of vertical connected pores and the number n of radial connected pores; 2. after the asphalt mixture test piece is saturated with water in vacuum, frost heaving stress test is carried out on the test piece to obtain initial frost heaving stress sigma in horizontal and vertical directionsH1And σV1(ii) a 3. After the test piece is thawed to normal temperature, cutting the test piece into four pieces along the horizontal symmetrical plane and the vertical symmetrical plane, inserting a plastic plate into a cutting plane, and adhering the cutting pieces in situ by using glue; 4. respective test of horizontal and vertical frost heaving stress sigma of the gel test pieceH2And σV2(ii) a 5. And calculating the resolution ratio.
Description
Technical Field
The invention relates to the field of asphalt mixture performance testing, in particular to a method for testing the resolution effect of communicated pores of an asphalt mixture on frost heaving stress.
Background
The road occupies an important part in modern traffic, wherein the asphalt pavement is widely applied in China due to the characteristics of high driving comfort, good stability, low noise and the like. Asphalt pavements, however, also have a number of problems, wherein the freeze-thaw durability of the pavement has been of constant interest to many researchers. The performance and the quality of the asphalt pavement are improved, so that the performance of the pavement material is adaptive to the environmental requirements, and the asphalt pavement material is the key point of research on road work.
In road engineering in cold areas, under the action of rainfall or snowfall weather, water can permeate into pores of the asphalt concrete pavement; when the air temperature is reduced, under the condition that the pore water saturation (the ratio of water to pore volume) of the asphalt concrete pavement is large, the pore water ice-condensation volume expands, the pore wall is subjected to frost heaving pressure stress of ice, and when the asphalt mixture is restrained, the pressure stress cannot be effectively released and dissipated, so that frost heaving stress is generated in the whole mixture structure, and frost heaving damage is caused; the frost heaving damage generated by the asphalt concrete can damage the pavement structure, the service life of the asphalt pavement is reduced, and the pavement is seriously damaged by freeze thawing; the damage of frost heaving stress to the asphalt concrete can reduce the pavement performance of the asphalt concrete, so the low-temperature performance of the asphalt concrete has very important research significance. In recent years, around the problem of freeze-thaw durability of asphalt mixtures, many road workers have conducted some researches on indoor simulation methods in the freeze-thaw cycle process, the performance decay law of the mixtures after freeze-thaw, aggregate and asphalt interface damage caused by freeze-thaw, and the like, and have achieved certain results.
However, in the current experimental research, the digestion effect of the asphalt concrete communicated pores on the frost heaving stress is not linked with the low-temperature performance of the asphalt concrete, and a test method for the digestion effect of the asphalt concrete communicated pores on the frost heaving stress is not provided; therefore, a test method is needed for researching the digestion effect of the communicated pores on the frost heaving stress, so that the performance of the asphalt mixture can be better evaluated.
Disclosure of Invention
The purpose of the invention is as follows: the invention aims to provide a method for testing the digestion effect of communicated pores of an asphalt mixture on frost heaving stress.
The technical scheme adopted by the invention is as follows:
a method for testing the resolution effect of communicated pores of an asphalt mixture on frost heaving stress comprises the following steps:
the method comprises the following steps: scanning an asphalt mixture test piece by using a CT (computed tomography) instrument, reconstructing a three-dimensional connected pore structure of the test piece according to a scanning result, and extracting the number m of vertical connected pores and the number n of radial connected pores;
step two: after the asphalt mixture test piece is saturated with water in vacuum, frost heaving stress test is carried out on the test piece to obtain initial frost heaving stress sigma in horizontal and vertical directionsH1And σV1；
Step three: unfreezing the test piece, cutting the test piece into four pieces along a horizontal symmetrical plane and a vertical symmetrical plane after the test piece is at normal temperature, inserting a plastic plate into the cut surface, and bonding the four pieces inserted into the plastic plate according to the original relative positions by using glue;
step four: respectively testing the frost heaving stress sigma in the horizontal direction and the vertical direction of the cemented asphalt mixture test pieceH2And σV2；
Step five: calculating the resolution ratios of the communicating holes in the horizontal direction and the communicating holes in the vertical direction to the frost heaving stress, wherein the resolution ratios are respectively alpha and beta, and the formula is as follows:
according to the invention, the expansion volume of water ice moves along the communication direction of the communication pore, so that the frost heaving stress is reduced, the frost heaving stress has a certain digestion effect, and the digestion effect of the communication pore on the frost heaving stress is evaluated by using the ratio alpha and beta obtained by comparing the frost heaving stress before and after the communication pore of the test piece is cut off.
As a further improvement of the present invention, the vertical cutting plane in step three is perpendicular to the radial direction selected in step one.
As a further improvement of the invention, the determination point of the frost heaving stress of the asphalt mixture after cementation in the fourth step is consistent with the determination point of the asphalt mixture before cutting in the second step.
As a further improvement of the invention, the frost heaving stress test is carried out in the second step and the fourth step by adopting the same test conditions.
As a further improvement of the invention, the test apparatus used is kept at the test ambient temperature before and after the test.
As a further improvement of the invention, the plastic plate adopts a hard plastic thin plate with the thickness of less than 1mm, and the shape and the size of the plastic thin plate are consistent with the cutting surface of the asphalt mixture.
Has the advantages that: the invention has the following advantages:
(1) the invention skillfully links the performance test of the asphalt mixture and the digestion effect of the communicated pores on the frost heaving stress, and evaluates the performance of the asphalt mixture from the communicated pores.
(2) According to the invention, the number n of the communicated pores in the horizontal direction and the number m of the communicated pores in the vertical direction are related to the digestion rates alpha and beta, so that the digestion effect of different numbers of the communicated pores on the frost heaving stress can be measured.
(3) The method utilizes the digestion rates alpha and beta to evaluate the digestion effect of the communicated pores on the frost heaving stress, and the digestion effect evaluation on the frost heaving stress is more pertinent.
Drawings
FIG. 1 is a schematic flow chart of a testing method of the present invention;
FIG. 2 is a frost heaving stress test chart of an uncut asphalt mixture;
FIG. 3 is a frost heaving stress test chart of the asphalt mixture after cementation;
FIG. 4 is a cross-sectional view of a frost heaving stress test of the asphalt mixture after cementation;
FIG. 5 is a constraint diagram of a frost heaving stress test specimen
Description of reference numerals: 1-asphalt mixture test piece, 2-pressure box, 3-communicating pore, 4-closed pore, 5-aggregate, 6-external constraint mechanism, 7-cementation test piece and 8-plastic plate.
Detailed Description
The invention is further described below with reference to the accompanying drawings; the following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby. The invention is implemented by the following steps:
(1) firstly, forming an asphalt mixture test piece 1 (hereinafter referred to as a test piece 1) in a rotary compaction mode; the method comprises the steps of scanning a test piece 1 by using a CT scanner to generate 162 vertical cross section images and 101 horizontal cross section images, importing the generated images into a Mimics image processing software to reconstruct a three-dimensional pore structure, and then acquiring characteristic parameters (information such as a starting point coordinate, an end point coordinate and a cross section average hydraulic radius of each pore) of the pores by using software OGFC (open glass flow control) asphalt mixture internal pore identification software), so that the number m of communicated pores 3 in the vertical direction and the number n of communicated pores 3 in the radial direction of the test piece 1 are extracted from the software.
(2) And (3) sequentially carrying out vacuum water saturation for 15min and normal-pressure soaking for 30min on the test piece 1 to obtain a normal-temperature water-saturated test piece. Then, carrying out freeze thawing treatment by adopting air-freezing water melting; firstly, carrying out low-temperature pretreatment on a frost heaving stress testing device, placing the frost heaving stress testing device in a low-temperature box at the temperature of minus 18 ℃ for 3 hours, then placing a test piece 1 in the frost heaving stress testing device at the temperature of minus 18 ℃, placing the testing device in the low-temperature box at the temperature of minus 18 ℃, carrying out frost heaving stress test on the test piece 1, recording the frost heaving stress of the test piece 1 in the horizontal direction and the vertical direction, and recording the frost heaving stress as sigmaH1And σV1. The structure of the device used in the test is shown in fig. 5: an external restraint mechanism 6 capable of clamping the pressure box 2 is arranged on the outer side of the test piece, a steel cylinder is adopted as the external restraint mechanism 6, gaps for placing the pressure box 2 are formed between the side surface, the upper surface and the lower surface of the steel cylinder and the placed test piece, and the pressure box 2 is fixed between the steel cylinder and the test piece. In the testing process, the steel cylinder is kept in an environment of 18 ℃ below zero in advance before the test piece 1 is placed in the steel cylinder, so that the influence of shrinkage stress generated by the steel cylinder at a low temperature is eliminated, and accurate frost heaving stress data of the asphalt mixture test piece 1 are obtained.
(3) After the frost heaving stress test is finished, dissolving the test piece 1 in normal temperature water for 4 hours; after the test piece is at normal temperature, cutting the dissolved asphalt mixture 1 into four blocks along the horizontal symmetrical surface and the vertical symmetrical surface, washing the cutting surface with water in the cutting process, and preventing the aggregate 5 scraps from splashing in the cutting process; wherein the vertical cutting surface of the test piece is perpendicular to the radial direction selected in the step one; the ABS hard plastic thin plate 8 with the thickness of 1mm is inserted into a cutting surface of the asphalt mixture, the size and the shape of the ABS plastic thin plate 8 are the same as those of the cutting surfaces of the asphalt mixture in the horizontal direction and the vertical direction, glue is uniformly and thinly coated on two sides of the ABS hard plastic thin plate 8, and the four blocks are bonded according to the original relative positions; the hard plastic plate can effectively block the communicating pores of the asphalt mixture, eliminate the digestion effect of the communicating pores on frost heaving stress, and the thin plate with the thickness of 1mm can not cause great changes in the volume and the quality of a cemented asphalt mixture test piece.
(4) And (3) performing frost heaving stress test on the test piece which is inserted into the plastic thin plate 8 and cemented by adopting the same conditions and treatment process as those in the step (2), and recording the frost heaving stress of the cemented test piece 7 in the horizontal direction and the vertical direction as sigmaH2And σV2(ii) a The purpose of low-temperature pretreatment on the frost heaving stress testing device is to eliminate the influence of shrinkage stress generated by the steel cylinder at a low temperature, so that accurate data of the frost heaving stress of the cemented test piece 7 after cementation can be obtained; in order to obtain more accurate resolution of the communicated pores 3 to the frost heaving stress before and after the test, the measurement point for measuring the frost heaving stress of the cemented test piece 7 after the cementation should be consistent with the measurement point of the test piece 1 before the cutting; and will be
Defined as the resolution ratio of single connected pore in the n connected pores 3 in the horizontal direction to the frost heaving stress
The resolution ratio of single communicated pores in the vertical direction to the frost heaving stress is defined, and then the resolution effect of the asphalt mixture communicated pores on the frost heaving stress is evaluated through alpha and beta.
The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (6)
1. A method for testing the resolution effect of communicated pores of an asphalt mixture on frost heaving stress is characterized by comprising the following steps of:
the method comprises the following steps: scanning an asphalt mixture test piece by using a CT (computed tomography) instrument, reconstructing a three-dimensional connected pore structure of the test piece according to a scanning result, and extracting the number m of vertical connected pores and the number n of radial connected pores;
step two: after the asphalt mixture test piece is saturated with water in vacuum, frost heaving stress test is carried out on the test piece to obtain initial frost heaving stress in the horizontal direction and the vertical direction
And
；
step three: unfreezing the test piece, cutting the test piece into four pieces along a horizontal symmetrical plane and a vertical symmetrical plane after the test piece is at normal temperature, inserting a plastic plate into the cut surface, and bonding the four pieces inserted into the plastic plate according to the original relative positions by using glue;
step four: respectively testing the frost heaving stress of the cemented asphalt mixture test piece in the horizontal direction and the vertical direction
And
；
step five: calculating the resolution ratios of the communicating holes in the horizontal direction and the communicating holes in the vertical direction to the frost heaving stress respectively
And
the formula is as follows:
2. the method for testing the resolution effect of the communicated pores of the asphalt mixture on the frost heaving stress according to claim 1, wherein the method comprises the following steps: and the vertical cutting surface in the third step is perpendicular to the radial direction selected in the first step.
3. The method for testing the resolution effect of the communicated pores of the asphalt mixture on the frost heaving stress according to claim 1, wherein the method comprises the following steps: and the measuring point of the frost heaving stress of the asphalt mixture after cementation in the fourth step is consistent with the measuring point of the frost heaving stress of the asphalt mixture before cutting in the second step.
4. The method for testing the resolution effect of the communicated pores of the asphalt mixture on the frost heaving stress according to claim 1, wherein the method comprises the following steps: and step two and step four adopt the same test condition to carry on the frost heaving stress test.
5. The method for testing the resolution effect of the communicated pores of the asphalt mixture on the frost heaving stress according to claim 4, wherein the method comprises the following steps: the test apparatus used was kept at the test ambient temperature before and after the test.
6. The method for testing the effect of the communicated pores of the asphalt mixture on the resolution of the frost heaving stress as claimed in claim 1, wherein the plastic plate is a hard plastic thin plate with the thickness of less than 1mm, and the shape and the size of the plastic thin plate are consistent with the cutting surface of the asphalt mixture.
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