CN113686730B - Method for evaluating high-temperature viscoelasticity of asphalt mortar and asphalt mortar forming die - Google Patents
Method for evaluating high-temperature viscoelasticity of asphalt mortar and asphalt mortar forming die Download PDFInfo
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Abstract
The invention discloses a method for evaluating the high-temperature viscoelasticity of asphalt mortar and an asphalt mortar forming die, wherein the method comprises the following steps: providing an asphalt mortar test piece, and performing an improved multiple creep recovery (MSCR) test on the asphalt mortar test piece; fitting an improved fractional order creep recovery model and an MSCR test result to obtain a creep parameter of the asphalt mortar; and evaluating the high-temperature viscoelasticity performance of the asphalt mortar according to the obtained fractional order and the deformation factor. The invention provides a new test and analysis method for the evaluation of the high-temperature viscoelasticity of the asphalt mortar, and can more accurately and systematically research the high-temperature performance of the asphalt mortar.
Description
Technical Field
The invention relates to the field of asphalt mortar performance evaluation, in particular to a method for evaluating high-temperature performance of a multiple creep recovery test of asphalt mortar by using a fractional derivative theory and an asphalt mortar forming die.
Background
Ruts are a pavement defect specific to asphalt pavements, and are accumulated permanent deformation formed by repeated action of wheel loads in the long-term service process of the asphalt pavements. The occurrence and development of the ruts not only affect the comfort of the vehicle, but also threaten the safety of the vehicle. Research shows that various influencing factors are related to rutting deformation of the asphalt pavement, and the most important factors are road surface temperature and vehicle load. Under the conditions of high temperature and heavy load, the asphalt mixture shows stronger stress dependence and temperature sensitivity, so that the high-temperature performance of the asphalt mixture is reduced, and the generation and development of the rutting diseases of the asphalt pavement are accelerated.
On the basis of the multi-scale characteristics of the asphalt mixture composition structure, the asphalt pavement is divided into three scales, namely asphalt mixture under the macroscopic scale, asphalt mortar under the microscopic scale and aggregate and asphalt/asphalt mortar interface under the microscopic scale. As a transition structure for connecting the interaction relationship between the macroscopic scale and the microscopic scale of the asphalt mixture, the asphalt mortar is an important component under the microscopic hierarchical scale. The mortar theory of asphalt mixture is that asphalt mortar is composed of filler, fine aggregate, asphalt in the interface area of fine aggregate, effective asphalt and gaps. The rutting deformation characteristics of the asphalt pavement are directly related to the high-temperature creep property of the asphalt mixture, and from the aspect of the composition structure of the asphalt mixture, the high-temperature creep property of the asphalt mixture is mainly influenced by the high-temperature viscoelasticity characteristics of the asphalt mortar. In recent years, no matter in asphalt mixture test observation or microscopic numerical simulation analysis, most of the damage of the asphalt mixture is generated and expanded in an asphalt mortar phase, the characteristic dimension of the asphalt mortar is closer to that of the asphalt mixture, and the viscoelastic property of the asphalt mortar can better reflect the macroscopic performance of the asphalt mixture. It follows that asphalt mortar is a non-negligible constituent of asphalt pavement materials. However, the current research on the high temperature performance of asphalt mixtures still mainly focuses on 2 material scales of asphalt and asphalt mixtures. Therefore, it is necessary to develop a test for revealing the high-temperature viscoelasticity of the asphalt mortar material.
At present, creep curves, compression test curves and the like of asphalt mortar at normal temperature are generally adopted at home and abroad to analyze the viscoelastic change rule of the asphalt mortar, and the test is relatively single. The viscoelastic properties of asphalt mortar at high temperature are generally evaluated according to the test method and index of the high temperature performance of asphalt, i.e. the complex shear modulus G of asphalt mortar is obtained by frequency sweep test through DSR equipment * And a phase angle delta, thereby evaluating the high-temperature viscoelasticity performance of the asphalt mortar. However, this index has significant limitations in evaluating modified asphalt mortar.
Disclosure of Invention
In view of this, in order to perform a systematic study on the high-temperature viscoelasticity of the asphalt mortar, the invention provides a test and analysis method for evaluating the high-temperature viscoelasticity performance of the asphalt mortar and an asphalt mortar forming mold. The invention carries out a multiple creep recovery test (MSCR test) on the prepared asphalt mortar, describes the viscoelastic performance of the asphalt mortar by adopting a proposed fractional order creep recovery model, and evaluates the high-temperature viscoelasticity of the asphalt mortar by using the fractional order derivative order and a deformation factor. The invention provides a new test and analysis method for evaluating the high-temperature viscoelastic property of the asphalt mortar, so that the high-temperature property of the asphalt mortar can be studied more accurately, scientifically and systematically, and the method has low requirement on test equipment and is easy to realize under the existing test conditions.
The invention adopts a Dynamic Shear Rheometer (DSR) to carry out high-temperature viscoelasticity test research on the asphalt mortar. The formed asphalt mortar meets the requirements of loading clamps in DSR equipment. According to the clamp requirement of DSR equipment, asphalt mortar samples are uniformly formed into cylindrical test pieces with the diameter of 12mm and the height of 30mm. Therefore, the invention provides an asphalt mortar forming die.
The invention provides a test and analysis method for evaluating high-temperature viscoelasticity of asphalt mortar, which comprises the following steps:
step (1): providing an asphalt mortar test piece, and performing an improved multiple creep recovery test on the asphalt mortar test piece;
step (2): fitting an improved fractional order creep recovery model with the multiple creep recovery test result obtained in the step (1) to obtain a creep parameter of the asphalt mortar, wherein the improved fractional order derivative creep recovery model is as follows:
and (3): and (3) evaluating the high-temperature viscoelasticity performance of the asphalt mortar according to the fractional order and the deformation factor obtained in the step (2).
Further, providing the asphalt mortar test piece comprises:
determining the asphalt content in the asphalt mortar by a specific surface area method, namely considering that the asphalt film thickness of the aggregate surface is the same, and the asphalt dosage is linearly related to the aggregate specific surface area;
calculating the use levels of fine aggregates, mineral powder and asphalt according to the determined asphalt content in the asphalt mortar and the gradation, the void ratio and the theoretical density of the asphalt mortar, and mixing the fine aggregates, the mineral powder and the asphalt to form the asphalt mortar;
and pressing the asphalt mortar into the mold to form a mortar test piece.
Further, determining the asphalt content in the asphalt mortar by a specific surface area method, wherein the asphalt content in the asphalt mortar is determined by the following formula:
wherein: the maximum grain size of the fine aggregate in the asphalt mortar gradation is 2.36mm; p FAM : the asphalt-to-stone ratio of the asphalt mortar; p i : percent of pass of aggregates of different particle sizes; FA i : surface area coefficients of aggregates of different particle sizes; SA <2.36 : total specific surface area of aggregate passing through 2.36mm mesh, P a : the optimal oilstone ratio of the asphalt mixture; p is 2.36 : percent passing rate of 2.36mm mesh in asphalt mix.
Further, in the step of pressing the asphalt mortar into a mold to form a mortar test piece, the asphalt mortar is pressed into a forming mold for four times, the asphalt mortar is added each time and then is compacted by a heated stirring rod, after the asphalt mortar is completely pressed into the mold, the top surface of the mold is covered with a heavy object, and the mold is released after the mold is placed at room temperature for 24 hours.
Furthermore, the die comprises a front die, a rear die, a bottom plate and two fixed circular rings, wherein the front die and the rear die are spliced and then spliced with the bottom plate; the front die and the rear die are provided with forming cavities with the height of 30mm, each forming cavity comprises three coaxial cylinders, namely two cylinders with the distance of 4mm from the upper surface and the lower surface and the diameter of 14mm and a cylinder with the diameter of 12mm in the middle of the cavity; the two fixed circular rings are respectively arranged at two ends of the forming cavity, the outer diameter of each fixed circular ring is 14mm, the inner diameter of each fixed circular ring is 12mm, and the height of each fixed circular ring is 4mm;
the mould forms the asphalt mortar sample into a cylinder test piece with the diameter of 12mm and the height of 30mm so as to meet the loading requirement of the dynamic shear rheometer.
Further, the step (3): evaluating the high-temperature viscoelasticity performance of the asphalt mortar according to the fractional order and the deformation factor obtained in the step (2), wherein the evaluation comprises the following steps: the higher the fractional order is, the stronger the viscosity of the asphalt mortar is; the larger the deformation factor, the worse the high temperature stability of the asphalt mortar.
Further, the step (1): providing an asphalt mortar test piece, and carrying out an improved multiple creep recovery test on the asphalt mortar test piece, wherein the test comprises the following steps: the stress in the multiple creep recovery test was 1.2kPa, 3.2kPa, 6.4kPa, 12.8kPa, 25.6kPa, respectively; the stress is loaded from small to large in sequence, and no time interval is set between the stresses of different grades; each stage of stress was subjected to 10 loading cycles, each cycle of the loading cycle comprising a 1.0s loading phase and a 9.0s unloading phase.
Further, parameter obtaining is to perform parameter fitting on the asphalt mortar multiple creep recovery test data by using an improved fractional order creep recovery model by using a Levenberg-Marquardt optimization algorithm to obtain the fractional order and the deformation factor in a loading stage and an unloading stage.
The invention also provides an asphalt mortar forming die applied to the test and analysis method for evaluating the high-temperature viscoelasticity performance of the asphalt mortar, wherein the asphalt mortar forming die comprises a front die, a rear die, a bottom plate and two circular ring clamps; the front die and the rear die are spliced with the bottom plate, the front die and the rear die form a forming cavity, the cavity height is 30mm, the forming cavity comprises three coaxial cylinder cavities, namely a cylinder with a diameter of 14mm and a cylinder with a diameter of 12mm at the middle part within a range of 4mm from the upper surface and the lower surface, the two ring clamps are respectively arranged in the two cylinder cavities at the two ends, the outer diameter of each ring clamp is 14mm, the inner diameter of each ring clamp is 12mm, and the height of each ring clamp is 4mm.
Furthermore, the front die and the rear die are two parts of a polytetrafluoroethylene cuboid provided with a forming cavity and cut from a middle line; the front die, the rear die and the bottom plate are connected with limiting holes communicated with each other through screws to be spliced.
Has the advantages that: the invention discloses a method for testing and evaluating the high-temperature performance of asphalt mortar, which aims at the shortage of asphalt mortar high-temperature viscoelasticity testing and evaluating methods at home and abroad, can test and evaluate the viscoelasticity of the asphalt mortar with different stress levels at high temperature, and has the characteristics of simple test operation, small variability, economy and the like. The invention provides a new test and evaluation method for evaluating the high-temperature viscoelastic property of the asphalt mortar, and the high-temperature property of the asphalt mortar can be researched more systematically and accurately.
The invention adopts a Dynamic Shear Rheometer (DSR) to carry out high-temperature viscoelasticity test research on the asphalt mortar. The formed asphalt mortar meets the requirements of loading clamps in DSR equipment. According to the clamp requirement of DSR equipment, asphalt mortar samples are uniformly formed into cylindrical test pieces with the diameter of 12mm and the height of 30mm. Therefore, the invention provides an asphalt mortar forming die.
Drawings
FIG. 1 is a schematic view of an asphalt mortar molding die and a molded sample;
FIG. 2 is a MSCR test strain curve of asphalt mortar;
FIG. 3 is MSCR test strain curve and model curve of SBS modified asphalt mortar under different stresses.
The names of the parts represented by numbers or letters in the drawings are as follows: (1) is a front mold; (2) is a rear mold; (3) is a bottom plate; (4) is a limiting hole; (5) is a circular ring clamp; (6) is an asphalt mortar sample; (7) is a spliced mould.
Detailed Description
A test and analysis method for evaluating the high-temperature viscoelasticity performance of asphalt mortar comprises the following steps:
step (1): providing an asphalt mortar test piece, and performing an improved multiple creep recovery test on the asphalt mortar test piece;
step (2): fitting an improved fractional order creep recovery model with the multiple creep recovery test result obtained in the step (1) to obtain a creep parameter of the asphalt mortar, wherein the improved fractional order derivative creep recovery model is as follows:
and (3): and (3) evaluating the high-temperature viscoelasticity performance of the asphalt mortar according to the fractional order and the deformation factor obtained in the step (2).
An asphalt mortar forming die applied to a test and analysis method for evaluating the high-temperature viscoelasticity of asphalt mortar comprises a front die, a rear die, a bottom plate and two circular ring clamps; the front die and the rear die are spliced with the bottom plate, the front die and the rear die form a forming cavity, the cavity height is 30mm, the forming cavity comprises three coaxial cylinder cavities, namely a cylinder with a diameter of 14mm and a cylinder with a diameter of 12mm at the middle part within a range of 4mm from the upper surface and the lower surface, the two ring clamps are respectively arranged in the two cylinder cavities at the two ends, the outer diameter of each ring clamp is 14mm, the inner diameter of each ring clamp is 12mm, and the height of each ring clamp is 4mm.
The front die and the rear die are two parts of a polytetrafluoroethylene cuboid provided with a forming cavity and cut from a middle line; the front die, the rear die and the bottom plate are connected with limiting holes communicated with each other through screws to be spliced.
A test and analysis method for evaluating the high-temperature viscoelasticity performance of asphalt mortar comprises the following steps:
step (1): design of asphalt mortar forming die
An asphalt mortar forming die is made of polytetrafluoroethylene and comprises a front die, a rear die, a bottom plate, screws and a circular ring clamp; the front die and the rear die are two parts of a polytetrafluoroethylene cuboid provided with a forming cavity and cut from a middle line, and the height of the cavity is 30mm. The front mould and the rear mould are spliced with the bottom plate.
The internal forming cavity is composed of three coaxial cylinders, wherein the cavity is a cylinder with the diameter of 14mm within 4mm from the upper surface and the lower surface of a polytetrafluoroethylene cuboid respectively, and the rest part of the cavity is a cylinder with the diameter of 12 mm.
The invention relates to a splicing of a forming die, which is characterized in that a front die, a rear die and a bottom plate are connected by screws through mutually communicated limiting holes.
In the mortar test piece forming die, the open ends of the internal forming cavities are respectively provided with a fixed ring; the outer diameter of the circular ring is 14mm, the inner diameter is 12mm, and the height is 4mm.
Step (2): determination of asphalt content in asphalt mortar
The invention adopts a specific surface area method to determine the asphalt content in the asphalt mortar, and the calculation formula is as follows:
wherein: the maximum grain size of the fine aggregate in the asphalt mortar gradation is 2.36mm; p is FAM : the asphalt-to-stone ratio of the asphalt mortar; p i : percent of pass of aggregates of different particle sizes; FA i : surface area coefficients of aggregates of different particle sizes; SA <2.36 : total specific surface area of aggregate passing through 2.36mm mesh, pa: the optimal oilstone ratio of the asphalt mixture; p2.36: percent passing rate of 2.36mm mesh in asphalt mix.
And (3): preparation of asphalt mortar test piece
(1) And (3) assembling the mortar forming die according to the design method in the step (1).
(2) Determining the porosity of the prepared asphalt mortar, and determining the material weighing mass required by an asphalt mortar sample according to the theoretical density of the asphalt mortar and the volume of a forming die. In order to ensure the quality of the asphalt mortar, 5 asphalt mortar test pieces are prepared by one-time mixing.
(3) Weighing the mass of fine aggregate and mineral powder of each grade of 5 asphalt mortar test pieces according to an asphalt mortar grading curve, heating the fine aggregate and mineral powder in an oven at the temperature of between 170 and 175 ℃ for 4 hours, and simultaneously heating and preserving the heat of asphalt, a metal mixing rod and a metal disc in the oven at the temperature of between 165 and 170 ℃ for 4 hours;
(4) Keeping the temperature of the small mixing pot to 165 ℃, weighing asphalt according to the asphalt content calculated in the step (2), pouring the asphalt into the mixing pot, and immediately pouring the fine aggregate weighed in the step (3) into the mixing pot to be stirred for 60 seconds; after the mixing is finished, pouring the mineral powder weighed in the step (2) into a mixing pot to be mixed for 60 seconds; after the mixing is finished, the metal plate is filled with asphalt mortar and placed in an oven at 170 ℃.
(5) And pressing the weighed asphalt mortar material into the die for four times, and manually compacting the asphalt mortar added each time by adopting a heated stirring rod.
(6) And after the weighed asphalt mortar is completely pressed into the mold, covering a heavy object on the top surface of the mold, and standing at room temperature for storage. Demoulding can be carried out after 24 hours. And obtaining a complete asphalt mortar test piece.
It is understood that in other embodiments, steps (1) - (3) may be omitted and the asphalt mortar test pieces may be provided directly for subsequent testing.
And (4): multiple creep recovery test of asphalt mortar test piece
Based on the loading mode of the standard MSCR test, the improved MSCR test increases the original 2-grade stress level to 5 grades which are respectively 1.2kPa, 3.2kPa, 6.4kPa, 12.8kPa and 25.6kPa, properly widens the stress loading range and is beneficial to testing the high-temperature viscoelasticity of the asphalt mortar. The improved MSCR test adopts stress control loading, the stress is loaded from small to large in sequence, and no time interval is set between the stresses of different grades. Each stage of stress was subjected to 10 loading cycles, each cycle of the loading cycle comprising a 1.0s loading phase and a 9.0s unloading phase. In addition, the modified MSCR test temperature was 64 ℃ according to the standard test. The asphalt mortar obtains different strain response results for different loading stresses, and the strain curve of the asphalt shows typical creep and recovery characteristics along with the loading and unloading processes of the load in each loading cycle.
And (5): establishment of asphalt mortar creep recovery model and acquisition of parameters
Because the viscoelasticity of the asphalt material has stress dependence and temperature dependence, the invention provides an improved fractional order creep recovery model which can accurately describe the deformation characteristics of asphalt mortar in a loading stage and an unloading stage, and the model comprises the following steps:
wherein: epsilon (t) is the strain of the asphalt mortar; alpha and r are fraction orders of a loading stage and an unloading stage respectively and reflect the viscoelastic property of the asphalt material; A. b is deformation factors of a loading stage and an unloading stage respectively, and reflects the high-temperature stability of the asphalt performance;
the method utilizes a Levenberg-Marquardt optimization algorithm and uses an improved fractional order creep recovery model expression to perform parameter fitting on the MSCR test data of the asphalt mortar to obtain each parameter.
And (6): evaluation of high-temperature viscoelasticity of asphalt mortar
And (5) acquiring fractional order and deformation factors of the loading stage and the unloading stage at different stress levels at high temperature, describing the viscoelasticity of the asphalt mortar through the fractional order, and evaluating the high-temperature performance of the asphalt mortar through the deformation factors. The larger the fractional order, the stronger the viscosity of the material is, and the larger the deformation factor is, the poorer the high-temperature stability of the asphalt mortar is.
The first specific implementation way is as follows:
the invention is described in further detail below with reference to the following detailed description and accompanying drawings:
step (1): design of asphalt mortar forming die
As shown in fig. 1, the asphalt mortar forming mold of the present embodiment is made of polytetrafluoroethylene, and includes a front mold (1), a rear mold (2), a bottom plate (3), a ring clamp (5), and screws; the front die (1) and the rear die (2) are two parts of a polytetrafluoroethylene cuboid provided with a forming cavity and cut from a middle line.
The length, the width and the height of the polytetrafluoroethylene cuboid are respectively 50mm, 40mm and 30mm, the internal forming cavity is formed by three cylinders with different diameters, the cavity is a cylinder with the diameter of 14mm in a range of being 4mm away from the upper surface and the lower surface of the polytetrafluoroethylene cuboid, and the rest part of the cavity is a cylinder with the diameter of 12 mm.
As shown in figure 1, the front die (1) and the rear die (2) are spliced by connecting limiting holes (4) on the front die and the rear die through screws, wherein the limiting holes are positioned at 5mm positions on two sides of a forming cavity, the height of each hole position is 15mm, and the diameter of each hole is 2mm. Before the nut is screwed down, the circular ring clamp (5) is placed into the opening end of a cylinder with the diameter of 14mm at the two ends, then the nut is screwed down, and the front die (1) and the rear die (2) are spliced. Wherein the outer diameter of the circular ring is 14mm, the inner diameter is 12mm, and the height is 4mm.
Place on the bottom plate after front mould (1) and back mould (2) amalgamate each other, will connect the spacing hole between bottom plate and front mould (1), back mould (2) through the screw to it is fixed with the nut, wherein spacing hole site is in four angles of bottom plate, and the diameter is 2mm. Wherein, the bottom plate is polytetrafluoroethylene cuboid, and its size is 50mm 40mm 5mm. The split molding die is shown in fig. 1 (7).
Step (2): determination of asphalt content in asphalt mortar
In the embodiment, SBS modified asphalt is adopted, the specific surface area method is adopted to determine the asphalt content in the asphalt mortar, and the calculation formula is as follows:
wherein: the maximum grain size of the fine aggregate in the asphalt mortar gradation is 2.36mm; p FAM : the asphalt-stone ratio of the asphalt mortar is percent; p i : percent of passing rate of aggregates with different particle sizes of the asphalt mixture; FA i : surface area coefficients of aggregates with different particle sizes of the asphalt mixture; SA <2.36 : total specific surface area of aggregate passing through a 2.36mm mesh; p a : optimum oilstone ratio of the asphalt mixture,%; p 2.36 : percent of passing rate of 2.36mm sieve pores in the asphalt mixture.
In the embodiment, the asphalt-stone ratio of the asphalt mortar green mortar is calculated according to the corresponding gradation of the AC-13 asphalt mixture and the optimal asphalt-stone ratio, and the asphalt-stone ratio of the asphalt mortar is 10.6%.
And (3): preparation of asphalt mortar test piece
(1) The mortar forming mold is assembled according to the method provided by the asphalt mortar forming mold of the step (1) of the present embodiment.
(2) In the embodiment, the porosity of the asphalt mortar is 4%, and the material weighing mass required by one asphalt mortar sample is determined according to the theoretical density of the asphalt mortar and the volume of a forming die. In order to ensure the quality of the asphalt mortar, 5 asphalt mortar test pieces are prepared by one-time mixing.
(3) Weighing the mass of fine aggregate and mineral powder of each grade of 5 asphalt mortars according to the asphalt mortar grading curve, putting the fine aggregate and the mineral powder into an oven at 170-175 ℃, heating for 4 hours, and simultaneously putting asphalt, a metal mixing rod and a metal disc into the oven at 165-170 ℃, heating and preserving heat for 4 hours;
(4) Keeping the temperature of the small mixing pot to 165 ℃, weighing asphalt according to the asphalt content calculated in the step (2), pouring the asphalt into the mixing pot, and immediately pouring the fine aggregate weighed in the step (3) into the mixing pot to be stirred for 60 seconds; after the mixing is finished, pouring the mineral powder weighed in the step (2) into a mixing pot for stirring for 60 seconds; after the mixing is finished, the metal plate is filled with asphalt mortar and placed in an oven at 170 ℃.
(5) And pressing the weighed asphalt mortar material into the mold for four times, and manually compacting the asphalt mortar added each time by adopting a heated stirring rod.
(6) And after the weighed asphalt mortar is completely pressed into the mold, covering a heavy object on the top surface of the mold, and standing at room temperature for storage. Demoulding can be carried out after 24 hours. And obtaining a complete asphalt mortar test piece.
And (4): improved multiple creep recovery test for asphalt mortar test piece
The asphalt mortar test piece was mounted on a dynamic shear rheometer to carry out a multiple creep recovery test with stresses of 1.2kPa, 3.2kPa, 6.4kPa, 12.8kPa, and 25.6kPa, respectively. The stress is loaded from small to large in sequence, and no time interval is set between the stresses of different grades. Each stage of stress was subjected to 10 loading cycles, each cycle of the loading cycle comprising a 1.0s loading phase and a 9.0s unloading phase. The MSCR test temperature was 64 ℃ according to standard tests. After the test is finished, different response results of asphalt mortar strain to different loading stresses can be obtained. The results are shown in FIG. 2.
And (5): establishment of asphalt mortar creep recovery model and acquisition of parameters
Because the viscoelasticity of the asphalt material has stress dependence and temperature dependence, the invention provides an improved fractional derivative creep-recovery model which can accurately describe the deformation characteristics of asphalt mortar in a loading stage and an unloading stage, and the model comprises the following steps:
wherein: epsilon (t) is the strain of the asphalt mortar; alpha and r are fraction orders of a loading stage and an unloading stage respectively and reflect the viscoelastic property of the asphalt material; A. b is a deformation factor of a loading stage and a deformation factor of an unloading stage respectively, and reflects the high-temperature stability of the asphalt performance;
performing parameter fitting on the MSCR test data of the asphalt mortar by using an improved fractional derivative creep-recovery model expression by using a Levenberg-Marquardt optimization algorithm to obtain various model parameters, wherein the fitting results are shown in FIG. 3, and the parameters are as follows
Table 1 shows:
TABLE 1 asphalt modified mortar fractional order creep recovery model parameters
And (6): evaluation of asphalt mortar high-temperature viscoelasticity
And (5) acquiring fractional order and deformation factors of the loading stage and the unloading stage under different stress levels, wherein the fractional order can describe the viscoelasticity of the asphalt mortar, and the deformation factors can evaluate the high-temperature performance of the asphalt mortar. The larger the fractional order is, the stronger the viscosity of the material is, and the larger the deformation factor is, the poorer the high-temperature stability of the asphalt mortar is. Therefore, for the asphalt mortar of the embodiment, as the stress increases, the viscosity of the asphalt is gradually increased, the high-temperature performance is gradually weakened, and under the same stress, the viscoelasticity of the asphalt in the loading stage is inconsistent with that in the unloading stage, and the viscosity of the asphalt is increased and the high-temperature performance is weakened in the unloading stage compared with that in the loading stage.
The above-described examples are intended to be only a few, and not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, belong to the scope of the present invention.
Claims (9)
1. A method for evaluating the high-temperature viscoelasticity performance of asphalt mortar is characterized by comprising the following steps:
step (1): providing an asphalt mortar test piece, and carrying out an improved multiple creep recovery test on the asphalt mortar test piece, wherein the test comprises the following steps:
the stress of the improved multiple creep recovery test is 1.2kPa, 3.2kPa, 6.4kPa, 12.8kPa, 25.6kPa, respectively; the stress is loaded from small to large in sequence, and no time interval is set between the stresses of different grades; carrying out 10 loading cycles under each stage of stress, wherein each loading cycle period comprises a 1.0s loading stage and a 9.0s unloading stage;
step (2): fitting an improved fractional order derivative creep recovery model with the multiple creep recovery test result obtained in the step (1) to obtain a creep parameter of the asphalt mortar, wherein the improved fractional order derivative creep recovery model is as follows:
and (3): and (3) evaluating the high-temperature viscoelasticity performance of the asphalt mortar according to the fractional order and the deformation factor obtained in the step (2).
2. The method for evaluating the high-temperature viscoelasticity of asphalt mortar according to claim 1,
the asphalt mortar test piece is provided with:
determining the asphalt content in the asphalt mortar by a specific surface area method, namely considering that the asphalt film thicknesses of the aggregate surfaces are the same, and linearly correlating the asphalt dosage with the aggregate specific surface area;
calculating the use levels of fine aggregates, mineral powder and asphalt according to the determined asphalt content in the asphalt mortar and the gradation, the void ratio and the theoretical density of the asphalt mortar, and mixing the fine aggregates, the mineral powder and the asphalt to form the asphalt mortar;
and pressing the asphalt mortar into the mold to form a mortar test piece.
3. The method for evaluating the high-temperature viscoelasticity of the asphalt mortar according to claim 2, wherein the asphalt content in the asphalt mortar is determined by a specific surface area method, and is determined by the following formula:
wherein: the maximum grain size of the fine aggregate in the asphalt mortar gradation is 2.36mm; p is FAM : the asphalt-to-stone ratio of the asphalt mortar; p is i : percent of pass of aggregates of different particle sizes; FA i : surface area coefficients of aggregates of different particle sizes; SA <2.36 : total specific surface area of aggregate, P, passing through a 2.36mm mesh a : the optimal oilstone ratio of the asphalt mixture; p 2.36 : percent passing rate of 2.36mm mesh in asphalt mix.
4. The method for evaluating the high-temperature viscoelasticity of the asphalt mortar according to claim 2, wherein the asphalt mortar is pressed into the mold to form a mortar test piece, the asphalt mortar is pressed into the forming mold four times, the asphalt mortar is compacted by a heated stirring rod after being added each time, after the asphalt mortar is completely pressed into the mold, the top surface of the mold is covered with a heavy object, and the mold is released after being placed at room temperature for 24 hours.
5. The method for evaluating the high-temperature viscoelasticity of the asphalt mortar according to claim 2, wherein the mold comprises a front mold, a rear mold, a bottom plate and two fixing rings, and the front mold and the rear mold are spliced with the bottom plate; the front die and the rear die are provided with forming cavities with the height of 30mm, each forming cavity comprises three coaxial cylinders, namely two cylinders with the distance of 4mm from the upper surface and the lower surface and the diameter of 14mm and a cylinder with the diameter of 12mm in the middle of the cavity; the two fixed circular rings are respectively arranged at two ends of the forming cavity, the outer diameter of each fixed circular ring is 14mm, the inner diameter of each fixed circular ring is 12mm, and the height of each fixed circular ring is 4mm;
the mould forms the asphalt mortar sample into a cylindrical test piece with the diameter of 12mm and the height of 30mm so as to meet the loading requirement of the dynamic shear rheometer.
6. The method for evaluating the high-temperature viscoelasticity of the asphalt mortar according to claim 1, wherein the step (3): evaluating the high-temperature viscoelasticity performance of the asphalt mortar according to the fractional order and the deformation factor obtained in the step (2), wherein the evaluation comprises the following steps: the higher the fractional order is, the stronger the viscosity of the asphalt mortar is; the larger the deformation factor, the worse the high temperature stability of the asphalt mortar.
7. The method for evaluating the high-temperature viscoelasticity performance of the asphalt mortar according to claim 1, wherein the parameter obtaining is to perform parameter fitting on the asphalt mortar multiple creep recovery test data by using an improved fractional order creep recovery model by using a Levenberg-Marquardt optimization algorithm to obtain the fractional order and the deformation factor in a loading stage and an unloading stage.
8. An asphalt mortar forming die applied to the method for evaluating the high-temperature viscoelasticity of the asphalt mortar in claim 1, wherein the asphalt mortar forming die comprises a front die, a rear die, a bottom plate and two circular ring clamps; the front die and the rear die are spliced with the bottom plate, the front die and the rear die form a forming cavity, the cavity height is 30mm, the forming cavity comprises three coaxial cylinder cavities, namely a cylinder with a diameter of 14mm and a cylinder with a diameter of 12mm at the middle part within a range of 4mm from the upper surface and the lower surface, the two ring clamps are respectively arranged in the two cylinder cavities at the two ends, the outer diameter of each ring clamp is 14mm, the inner diameter of each ring clamp is 12mm, and the height of each ring clamp is 4mm.
9. The asphalt mortar molding die according to claim 8, wherein the front die and the rear die are two parts of a polytetrafluoroethylene cuboid provided with a molding cavity cut from a middle line; the front die, the rear die and the bottom plate are connected with limiting holes communicated with each other through screws for splicing.
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| CN105891013B (en) * | 2016-04-08 | 2018-10-12 | 东南大学 | A kind of determination method of asphalt high-temerature creep spinodal decomposition point flow number |
| CN106198942B (en) * | 2016-06-24 | 2018-01-16 | 东南大学 | A kind of asphalt virtual performance experiment predictor method based on meso-level simulation |
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| CN108896418A (en) * | 2018-04-25 | 2018-11-27 | 东南大学 | A kind of asphalt multisequencing local loading high-temperature behavior test method |
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