CN112763378A - Asphalt apparent viscosity testing method based on dynamic shear rheometer - Google Patents
Asphalt apparent viscosity testing method based on dynamic shear rheometer Download PDFInfo
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- G01N11/00—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
- G01N11/10—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties by moving a body within the material
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Abstract
The invention discloses an asphalt apparent viscosity testing method based on a dynamic shear rheometer, which comprises three stages, wherein the first stage is an experiment preparation stage, the second stage is an operation testing stage, and the third stage is a data processing stage. The temperature change mode and the shear rate system of the asphalt to be tested are firstly established through three stages, program codes are set in the dynamic shear rheometer, and controllable testing can be carried out on various data of the asphalt by starting the program codes. Because the dynamic shear rheometer can realize the temperature active change and the rotating speed (shear rate) active change in the viscosity testing process through programming, the method can realize the viscosity-temperature scanning curve test of asphalt viscosity along the temperature change under the fixed shear rate; a viscosity-shear rate sweep curve of asphalt viscosity along the change in shear rate at a fixed temperature; the viscosity of the bitumen is scanned over the entire surface along a viscosity-temperature-shear rate profile where temperature and shear rate are varied together.
Description
Technical Field
The invention relates to the technical field of asphalt viscosity testing, in particular to an asphalt apparent viscosity testing method based on a dynamic shear rheometer.
Background
In road engineering construction, the asphalt viscosity-temperature curve in the range of 135-175 ℃ is determined according to the construction temperature (mixing and compacting temperature) of asphalt concrete, and the viscosity of asphalt generally changes within the range of 10 < -1 > to 102 Pa-s in the temperature range.
The currently common asphalt viscosity test method, namely the Brookfield rotational viscosity test method, is limited by a test principle, and the used rotor and rotating speed collocation need to be continuously changed in the viscosity-temperature curve test process so as to meet the requirements of continuously changing test precision and measuring range, so that the shear rate cannot be actively controlled when the method is used for testing the asphalt viscosity-temperature curve within the temperature range.
Due to the defects of the Brookfield rotational viscosity test method, the test stability of the modified asphalt with remarkable non-Newtonian characteristics (mainly represented by the asphalt with obvious viscosity dependence on shear rate) is poor when the modified asphalt is subjected to viscosity-temperature curve measurement by using the method, and finally, the asphalt construction temperature prediction work based on the viscosity-temperature curve is greatly deviated.
In addition, the method is insensitive to the change of the viscosity-temperature curve in a small range after various modifiers (such as warm mixing agents, flame retardants and the like) with different mixing amounts are added into the asphalt, finally, the test result is difficult to accurately express the temperature change range of the modified asphalt, a new sample needs to be prepared and heat preservation needs to be carried out again when the rotor and the rotating speed are replaced every time, and the method is complex in operation and consumes a lot of time.
Therefore, the research on the viscosity testing method capable of actively controlling the shear rate in the asphalt viscosity-temperature curve testing process has important practical significance for improving the precision and efficiency of the modified asphalt construction temperature prediction and deeply researching the comprehensive properties of the viscosity-temperature-shear rate of the asphalt.
Disclosure of Invention
The invention aims to provide an asphalt apparent viscosity testing method based on a dynamic shear rheometer, which can solve the problems that the traditional Brinell rotary viscosity testing method is difficult to actively control the shear rate in the asphalt viscosity-temperature curve testing process, so that the method cannot test asphalt with shear rate dependence characteristics according to a specific shear rate, and finally a series of asphalt performance tests based on the viscosity-temperature curve, such as construction temperature prediction, viscosity-temperature characteristic test and the like, have significant deviation.
In order to achieve the purpose, the invention provides a method for testing the apparent viscosity of asphalt based on a dynamic shear rheometer, which comprises the following steps:
s1: preparing an asphalt test piece, and setting the temperature in a test cavity of a dynamic shear rheometer as a test temperature;
s2: clamping an asphalt test piece, and applying torsion loading with a set rotating speed in a single direction to the asphalt test piece;
s3: testing the torque resistance of the parallel plate in the loading process, and calculating the apparent viscosity of the asphalt test piece at the current temperature through a formula 1;
s4: changing the temperature, and repeating the operations from S1 to S3 to obtain the viscosity-temperature curve and the temperature change mode of the tested asphalt test piece;
s5: changing the rotating speed omega p of an upper flat plate in the clamp according to the viscosity-temperature curve, testing the shearing rate, and establishing a system of a torsion loading mode under the specified shearing rate;
s6: setting a temperature rise path and a shear rate change path in sequence through the mode established in the step S4 and the system established in the step S5, and completing a temperature scanning test of viscosity, a shear rate scanning test of viscosity and a coordination scanning test of viscosity with respect to temperature and shear rate;
s7: recording test data and ending the test;
wherein, the formula 1 is
Wherein, the polar inertia moment of the top surface of the Ip-25 mm cylindrical asphalt test piece is a fixed value;
t-the resisting torque and the test value of the upper flat plate in the test piece selecting process;
h-25 mm of height of the cylindrical asphalt test piece, 1mm, fixed value;
the testing rotating speed and the set value set by the omega p-DSR are set;
eta-viscosity of the measured asphalt.
The beneficial effect who adopts above-mentioned scheme is: firstly, preparing asphalt into a uniform test piece which can be directly detected by a dynamic shear rheometer, and setting an initial temperature; the dynamic shear rheometer is used for controlling a flat plate to clamp a test piece, torsion loading with a set rotating speed in a single direction is applied to the test piece, the torque resistance T of an upper parallel plate during testing is recorded by the dynamic shear rheometer in the torsion loading process, and the apparent viscosity of the tested asphalt at the current temperature can be calculated through a formula 1. The system for testing the viscosity-temperature curve and the shear rate can be obtained by changing the temperature and the rotating speed of the flat plate, and the dynamic shear rheometer can be controlled to detect the active temperature change and the active shear rate change in the asphalt viscosity testing process through the tested curve and system. Wherein the dynamic shear rheometer can be one of Discover HR-2, Discover HR-3 and ARES-G2.
Further, the method for preparing the asphalt test piece in the step S1 includes: the asphalt to be tested is poured into an oblate asphalt test piece with the height H being 1mm and the diameter D being 25mm by using a metal test mould or a silica gel mould.
The beneficial effect who adopts above-mentioned scheme is: for a cylindrical test piece 25mm in diameter and 1mm in height: h and Ip are fixed values, and the apparent viscosity of the asphalt can be calculated by the formula 1 by only programming a control program of the dynamic shear rheometer to enable the upper parallel plate of the clamping test piece to rotate at a constant speed by omega p and record the torque resistance T and the temperature of the upper parallel plate during testing while the lower flat plate is stationary.
Further, the clamping method in step S2 is: and putting the asphalt test piece into a dynamic shear rheometer, controlling the upper flat plate of the clamp to descend, clamping the asphalt test piece, setting the gap between the upper flat plate and the lower flat plate to be 1mm, and scraping the extruded asphalt by using a hot scraper.
Further, in the torsion loading in step S2, the lower plate of the jig is fixed, and the upper plate rotates at a constant speed at the set angular velocity ω p.
The beneficial effect who adopts above-mentioned scheme is: in the whole testing process, the rotating speed omega p of the upper flat plate is controlled, so that the shearing rate when the asphalt viscosity is tested is controlled, and the torque of each test can be automatically recorded or the torque can be further used for calculating the output viscosity.
Further, step S7 specifically includes the following steps: and recording test data, taking out the asphalt test piece, taking down the 25mm flat plate fixture for cleaning, closing the dynamic shear rheometer, and finishing the test.
In summary, the invention has the following advantages:
the method can realize that: (1) testing the viscosity-temperature scanning curve (namely the viscosity-temperature curve) of the asphalt viscosity along the temperature change at a fixed shear rate; (2) a viscosity-shear rate sweep curve of asphalt viscosity along the change in shear rate at a fixed temperature; (3) the viscosity of the bitumen is scanned over the entire surface along a viscosity-temperature-shear rate profile where temperature and shear rate are varied together.
Drawings
FIG. 1 is a loading schematic of the present invention;
FIG. 2 is a schematic flow chart of an operation performed by the present invention;
wherein, 1, an upper flat plate; 2. asphalt test pieces; 3. and (5) a lower flat plate.
FIG. 3 is a viscosity-temperature curve of No. 70 base asphalt in example 1 and comparative example 1;
FIG. 4 is a viscosity-temperature curve of 110# base asphalt in example 1 and comparative example 1;
fig. 5 is a variation coefficient (C.V.) of viscosity at each temperature point of the 70# base asphalt in example 1 and comparative example 1;
fig. 6 is a variation coefficient (C.V.) of viscosity at each temperature point of 110# base asphalt in example 1 and comparative example 1;
FIG. 7 is a viscosity temperature curve of SBS modified asphalt of example 2 and comparative example 2;
FIG. 8 is a viscosity-temperature curve of SBR modified asphalt in example 2 and comparative example 2;
FIG. 9 is the coefficient of variation (C.V.) in viscosity at each temperature point for SBS modified asphalt in example 2 and comparative example 2;
FIG. 10 is the coefficient of variation (C.V.) in viscosity at each temperature point for SBR-modified asphalt in example 2 and comparative example 2;
FIG. 11 is a viscosity-temperature curve of SBS modified asphalt with addition of 4 types of common warm-mix agents in example 3;
FIG. 12 is a viscosity-temperature curve of the SBS modified asphalt of the comparative example 3 with the addition of the common warm-mix agents of class 4;
FIG. 13 is a graph of viscosity as a function of shear rate and temperature for matrix No. 70 bitumen in example 1;
FIG. 14 is a plot of viscosity as a function of shear rate and temperature for the SBS modified asphalt of example 2.
Detailed Description
The following description specifically describes the substance and effects of the present invention with reference to the examples, but the scope of the present invention is not limited thereto. The experimental procedures not described in detail in the experiments are all routine experimental procedures well known to the person skilled in the art.
First, the derivation process for equation 1 is as follows:
the basic assumption of the method is still Newton's internal friction law, the viscosity of the asphalt cement obtained by the test still belongs to the apparent viscosity, and the Newton's internal friction law is that the shear stress tau borne by the tested object is equal to the viscosity eta and the shear rate (velocity gradient)
The product of (c) is shown in equation 2:
wherein, eta is viscosity;
τ -shear stress;
The loading mode of the invention is that the lower parallel plate is fixed and the upper parallel plate is at a selected angular velocity omegapThe rotating shaft rotates at a constant speed,taking the center of the lower surface of the test piece as the origin of the center, the linear velocity of the position with the radius r of the upper surface should be v ═ ωp·。
On a cylindrical surface infinitesimal with radius r, the linear velocity v is also from omega to the lower surfacepR is reduced to 0, and the velocity gradient distribution in the direction of the height of the cylinder
(i.e., shear rate) can be expressed by the form of equation 3, where it should be noted that: the height and radius of the test piece are determined, so that the rotation speed omega of the upper flat plate is controlledpControl of the test shear rate can be achieved.
In the formula (I), the compound is shown in the specification,
-velocity gradient profile (shear rate);
ωp-the rotational speed;
h-specimen height;
r-radius of test piece
Since the asphalt test piece is subjected to a torsional load, the torsional shear stress τ of the asphalt test piece at each round section infinitesimal along the height direction can be expressed by formula 3:
in the formula: i isp-the polar moment of inertia of the top surface of the circular test piece;
τ — torsional shear stress;
r-specimen radius;
t is the torque applied to the upper plate by the asphalt test piece.
The newton's law of internal friction, which is expressed by bringing formulas 3 and 4 into formula 2, can yield formula 5:
wherein τ is torsional shear stress;
eta-viscosity;
ωp-the rotational speed;
h-specimen height.
By transforming equation 5, the second integration is performed along the radius and height directions, respectively, and the integration boundary conditions are: when H is H, ω is ωpWhen h is 0, ω is 0, as shown in formula 6:
by performing the integration of equation 6, the apparent viscosity of asphalt of the present invention can be obtained as equation 1.
The invention provides an asphalt apparent viscosity testing method based on a dynamic shear rheometer, wherein a temperature change mode and a temperature change system are established for the dynamic shear rheometer, and the method comprises the following steps:
s1: preparing an asphalt test piece, and setting the temperature in a test cavity of a dynamic shear rheometer as a test temperature;
s2: clamping an asphalt test piece, and applying torsion loading with a set rotating speed in a single direction to the asphalt test piece;
s3: testing the torque resistance of the parallel plate in the loading process, and calculating the apparent viscosity of the asphalt test piece at the current temperature through a formula 1;
s4: changing the temperature, and repeating the operations from S1 to S3 to obtain the viscosity-temperature curve and the temperature change mode of the tested asphalt test piece;
s5: and changing the rotating speed omega p of the upper flat plate in the clamp according to the viscosity-temperature curve, testing the shear rate, establishing a system of a torsion loading mode under the specified shear rate, and setting a program code.
Example 1
The invention provides an asphalt apparent viscosity testing method based on a dynamic shear rheometer, which is characterized in that the viscosity-temperature curves of ordinary matrix asphalt No. 70 and No. 110 are measured by the dynamic shear rheometer after the temperature change mode and the system are established, the mixing and compacting temperatures are determined according to the viscosity-temperature curves, and the testing result is compared with the result obtained by the traditional Brinell rotational viscosity testing method. Wherein the step of determining the viscosity-temperature curve comprises the following steps:
1. heating the asphalt to be tested, and pouring the asphalt to be tested into an oblate columnar asphalt test piece with the height H being 1mm and the diameter D being 25mm by using a metal test mold; simultaneously entering a starting process of the dynamic shear rheometer, and setting the installation temperature of the test piece to be 60 ℃ after calibration;
2. placing an asphalt test piece into a dynamic shear rheometer, controlling an upper flat plate of a clamp to descend, clamping the asphalt test piece, setting a gap between the upper flat plate and the lower flat plate to be 1mm, and scraping extruded asphalt by using a hot scraper;
3. calling program code to set a fixed value shear rate of 40s-1The temperature variation mode is that viscosity test is carried out once every 10 ℃, 10 times of parallel viscosity test is carried out on each temperature point, the average value is taken as the viscosity test value of the temperature point,
4. running a control program, and recording torque, shear rate and temperature information in the test process;
5. substituting the torque into a formula 1, calculating the apparent viscosity of the measured asphalt, and drawing a viscosity change curve of the asphalt;
6. and completing the test and closing the equipment.
Comparative example 1
The viscosity-temperature curves of ordinary matrix asphalt 70# and 110# are measured by using a traditional method, and the traditional method is used for testing according to an asphalt viscosity method given in the section of road engineering asphalt and asphalt mixture test procedure (JTG E20-2011) T0625-2011 asphalt rotational viscosity test of the trade Specification of Ministry of transportation; and simultaneously, carrying out viscosity test at the temperature of every 10 ℃, carrying out 10 times of parallel viscosity tests on each temperature point, obtaining an average value as a viscosity test value of the temperature point, and connecting obtained data points to form a viscosity-temperature curve.
The basic properties of the tested matrix asphalt are shown in Table 1, and the basic indexes of the matrix asphalt meet technical Specifications for road asphalt pavement construction (JTG F40-2004) of the Ministry of transportation in China.
TABLE 170 # and 110# base asphalt technical indexes (JTG F40-2004 technical Standard)
The viscosity-temperature curves of the same base asphalt obtained in example 1 and the same base asphalt obtained in comparative example 1 are placed in the same coordinate system, and the differences of the viscosity-temperature curve test results under the two test methods are compared. The viscosity-temperature curves of the 70#, 110# base asphalts are shown in fig. 3 and 4, respectively, and the coefficient of variation of viscosity (C.V.) at each temperature point is shown in fig. 5 and 6.
In order to compare the differences of viscosity values measured by the new method and the old method at each temperature point, the difference of the test results of the two test methods is analyzed from the statistical angle through a t-type hypothesis test of double sample variance to carry out a test, the significance level is selected to be 0.05, under the threshold condition, when the calculated p value (p-value) between the data groups of the two methods is more than or equal to 0.05, the probability that the test method does not cause the difference of the results is more than or equal to 95 percent, and the statistical expression is that no significant difference exists, in short, at a certain temperature, if the p value between 10 groups of viscosity data obtained by the invention and 10 groups of viscosity data obtained by the traditional method is more than 0.05, the method can be considered as follows: statistically, the method has no significant influence on the test result, i.e. the test effect of the invention is consistent with that of the traditional method, otherwise, if the p value is less than 0.05, the method is considered to have significant influence on the result, and the test result is inconsistent, and the p value distribution between the two methods is shown in a secondary coordinate system in fig. 3 and fig. 4.
Referring to the principle of "isothermal viscosity" (that is, referring to the stipulations in the section of road engineering asphalt and asphalt mixture test regulation (JTG E20-2011) of the ministry of transportation industry, T0625-2011 asphalt rotational viscosity test, the temperature corresponding to the viscosity of 0.28 ± 0.3pa.s is the mixing temperature, and the temperature range corresponding to the viscosity of 0.17 ± 0.2pa.s is the compacting temperature), the predicted construction temperature values of the two matrix asphalts under the two methods can be further determined through viscosity-temperature curves, and are shown in table 2:
TABLE 2 construction temperature of 70# and 110# base asphalt predicted by the present invention and conventional method
For the No. 70 matrix asphalt, when the temperature exceeds 102 ℃, the two methods have no significant difference (p-value is more than or equal to 0.05) in the test result, because the non-Newtonian fluid characteristic of the matrix asphalt is gradually weakened along with the increase of the temperature, the Newtonian fluid characteristic is shown, the viscosity is not sensitive to the shear rate, and the effect of the method on the test result is not significant.
In addition, the coefficient of variation (C.V.) of 10 parallel test data obtained in example 1 is smaller than that of the conventional method at all test temperature points, the reduction amplitude is more than 50%, and the test data dispersion is smaller.
Also for 110# base asphalt, due to the lower viscosity degree compared with 70# asphalt, the invention can replace the traditional method when the temperature reaches above 80 ℃ (p-value is more than or equal to 0.05), and besides, the tested variation coefficient (C.V.) is more than twice smaller than that of the invention, and the testing precision is higher.
Since the viscosity temperature curves of the two base asphalts at 100 ℃ and above are substantially the same under the two methods, the predicted mixing temperature and compaction temperature values predicted by the two methods are substantially the same, as detailed in table 2.
It can be seen from example 1 that, for the conventional 70# and 110# base asphalt, the new viscosity testing method with controllable shear rate on the viscosity-temperature curves and construction temperature tests of the two can completely replace the traditional viscosity testing method, and the testing precision is higher.
Example 2
The invention provides an asphalt apparent viscosity testing method based on a dynamic shear rheometer, which is characterized in that the viscosity-temperature curves of SBS and SBR of modified asphalt are measured by the dynamic shear rheometer after the temperature change mode and the system are established, the mixing and compacting temperatures are determined according to the viscosity-temperature curves, and the testing result is compared with the result obtained by the traditional Brookfield rotational viscosity testing method. Wherein the step of determining the viscosity-temperature curve comprises the following steps:
1. heating the asphalt to be tested, and pouring the asphalt to be tested into an oblate columnar asphalt test piece with the height H being 1mm and the diameter D being 25mm by using a metal test mold; simultaneously entering a starting process of the dynamic shear rheometer, and setting the installation temperature of the test piece to be 60 ℃ after calibration;
2. placing an asphalt test piece into a dynamic shear rheometer, controlling an upper flat plate of a clamp to descend, clamping the asphalt test piece, setting a gap between the upper flat plate and the lower flat plate to be 1mm, and scraping extruded asphalt by using a hot scraper;
3. calling program code to set a fixed value shear rate of 40s-1The temperature variation mode is that viscosity test is carried out once every 10 ℃, 10 times of parallel viscosity test is carried out on each temperature point, the average value is taken as the viscosity test value of the temperature point,
4. running a control program, and recording torque, shear rate and temperature information in the test process;
5. substituting the torque into a formula 1, calculating the apparent viscosity of the measured asphalt, and drawing a viscosity change curve of the asphalt;
6. and completing the test and closing the equipment.
Comparative example 2
Comparative example 2 the process is the same as comparative example 1 and will not be described further here.
The viscosity-temperature curves of the same base asphalt obtained in example 2 and the same base asphalt obtained in comparative example 2 are placed in the same coordinate system, and the differences of the viscosity-temperature curve test results under the two test methods are compared.
The basic properties of the modified asphalt to be tested are shown in Table 3, and the basic indexes of the modified asphalt meet the technical Specification for road asphalt pavement construction (JTG F40-2004) of the Ministry of transportation in China.
TABLE 3 main technical indexes of SBS and SBR modified asphalt for test (F40-2004 technical standard)
The viscosity-temperature curves of SBS and SBR modified asphalts are shown in FIG. 7 and FIG. 8, respectively, and the coefficient of variation of viscosity (C.V.) at each temperature point is shown in FIG. 9 and FIG. 10.
In order to compare the difference of viscosity values measured by the two methods at each temperature point, the difference of the test results of the two test methods is analyzed from the statistical angle by a t-type hypothesis test of double sample variance to test, the significance level is selected to be 0.05, under the threshold condition, when the calculated p value (p-value) between the data groups of the two methods is more than or equal to 0.05, the probability that the test method causes no difference on the results is more than or equal to 95%, and the statistical expression is that no significant difference exists, in short, at a certain temperature, if the p value between 10 groups of viscosity data obtained by the invention and 10 groups of viscosity data obtained by the traditional method is more than 0.05, the method can be considered as follows: statistically, the method has no significant influence on the test result, i.e. the test effect of the invention is consistent with that of the conventional method, otherwise, if the p value is less than 0.05, the method is considered to have significant influence on the result, and the test result is inconsistent, and the p value distribution between the two methods is shown in a secondary coordinate system in fig. 7 and fig. 10.
Referring to the principle of "isothermal viscosity" (that is, referring to the stipulations in the section of road engineering asphalt and asphalt mixture test regulation (JTG E20-2011) of the ministry of transportation industry, T0625-2011 asphalt rotational viscosity test, that the temperature corresponding to the viscosity of 0.28 ± 0.3pa.s is the mixing temperature, and the temperature range corresponding to the viscosity of 0.17 ± 0.2pa.s is the compacting temperature), the predicted construction temperature values of the two modified asphalts under the two methods can be further determined through viscosity-temperature curves, and are shown in table 4:
TABLE 4 construction temperatures for SBS and SBR based asphalts predicted by the present invention and conventional methods
For SBS pitch, when the temperature is below 175 deg.C, the non-Newtonian fluid shear thinning property is very strong, in order to meet the measuring range and precision of the test, the traditional method must change the rotor and the rotation speed many times in the test process of the temperature change, from 90 deg.C-175 deg.C, the traditional viscosity test method changes 4 times rotor rotation speed collocation, the shear rate is 1.4s-1, 5.6s-1, 9.3s-1, 18.6s-1 in turn but less than 40s-1 adopted by the invention, therefore, below 175 deg.C, the viscosity value obtained by the traditional method test is higher than the method of the invention, the position of the viscosity-temperature curve is higher, the curvature is larger the lower the temperature, the two test results show obvious difference (p < 0.05), after exceeding 175 deg.C, although the traditional viscosity test method changes collocation 1 time (corresponding to the shear rate is changed from 18.6s-1 to 46.5s-1), however, the viscosity values tested were not very different from the results of the present invention (p.gtoreq.0.05).
For another modified asphalt SBR, when the temperature reaches about 150 ℃, the viscosity-temperature curve obtained by the new viscosity testing method has no difference with the result given by the traditional viscosity method in statistics, but before 150 ℃, the viscosity value measured by the new viscosity method is obviously smaller than that of the traditional method, the position of the curve is lower, and the curvature is smaller than that of the traditional method.
Because the viscosity-temperature curves of the modified asphalt measured by the two methods have great difference, the construction temperature difference obtained by prediction is great, and for SBS modified asphalt, the predicted mixing temperature is obviously reduced by about 16 ℃ and the compaction temperature is reduced by 17 ℃ compared with the traditional method; in the invention, compared with the traditional method, the predicted values of the mixing temperature and the compaction temperature of the SBR modified asphalt are respectively reduced by 5 ℃ and 6 ℃.
It can be seen from example 2 that, when the modified asphalt is tested, the viscosity-temperature curves and the construction temperature prediction results of the modified asphalt provided by the new viscosity testing method and the traditional viscosity testing method are greatly different. According to engineering experience judgment, for general SBS modified asphalt, the mixing temperature of 196-200 ℃ obtained by the traditional method and the compaction temperature of 186-190 ℃ are obviously higher, and the prediction result given by the invention is obviously closer to the actual engineering
Whether the predicted construction temperature of the modified asphalt of the present invention can be used to guide production will be exemplified in test example 1.
Example 3
The invention provides an asphalt apparent viscosity testing method based on a dynamic shear rheometer, which is characterized in that a temperature change mode and a system post-establishing dynamic shear rheometer are used for measuring viscosity-temperature curves before and after 4 types of common warm-mixing agents (external additives specially used for reducing the asphalt construction temperature by 15-30 ℃ to meet the construction environmental protection requirement) are added into SBS modified asphalt, and the mixing and compacting temperature changes of the SBS modified asphalt are measured, and the test result is compared with the result obtained by the traditional Brinell rotational viscosity testing method. Wherein the step of determining the viscosity-temperature curve comprises the following steps:
1. heating the asphalt to be tested, and pouring the asphalt to be tested into an oblate columnar asphalt test piece with the height H being 1mm and the diameter D being 25mm by using a metal test mold; simultaneously entering a starting process of the dynamic shear rheometer, and setting the installation temperature of the test piece to be 60 ℃ after calibration;
2. placing an asphalt test piece into a dynamic shear rheometer, controlling an upper flat plate of a clamp to descend, clamping the asphalt test piece, setting a gap between the upper flat plate and the lower flat plate to be 1mm, and scraping extruded asphalt by using a hot scraper;
3. calling program code to set a fixed value shear rate of 40s-1The temperature variation mode is that viscosity test is carried out once every 10 ℃, 10 times of parallel viscosity test is carried out on each temperature point, the average value is taken as the viscosity test value of the temperature point,
4. running a control program, and recording torque, shear rate and temperature information in the test process;
5. substituting the torque into a formula 1, calculating the apparent viscosity of the measured asphalt, and drawing a viscosity change curve of the asphalt;
6. and completing the test and closing the equipment.
Comparative example 3
The method for measuring the viscosity of asphalt at 135 ℃ and 175 ℃ and then connecting into a viscosity-temperature curve is given in the section of road engineering asphalt and asphalt mixture test procedure (JTG E20-2011) T0625-2011 asphalt rotational viscosity test of the Ministry of transportation.
Wherein, the 4 kinds of warm-mixing agents added are common warm-mixing agents in road engineering, and are respectively a surface active type warm-mixing agent A, an organic viscosity reduction type warm-mixing agent B, a foam viscosity reduction type warm-mixing agent C, an inorganic viscosity reduction type warm-mixing agent D, SBS modified asphalt and warm-mixing modified asphalt formed by respectively adding 4 kinds of warm-mixing agents, and the main technical indexes are shown in a table 5. TABLE 5 main technical indexes of SBS modified asphalt for test and warm mix modified asphalt formed by adding 4 warm mixing agents (F40-2004 technical standard)
The viscosity-temperature curves of the warm-mixed SBS modified asphalt measured in example 3 and comparative example 3 are shown in FIGS. 11 and 12, respectively, and the viscosity value at each temperature point is an average value of 10 parallel tests.
Referring to the principle of "isothermal viscosity" (i.e. referring to the stipulations in the section "road engineering asphalt and asphalt mixture test procedure (JTG E20-2011)" T0625-2011 asphalt rotational viscosity test "of the ministry of transportation industry, the temperature corresponding to the viscosity of 0.28 ± 0.3pa.s is the mixing temperature, and the temperature range corresponding to the viscosity of 0.17 ± 0.2pa.s is the compacting temperature), the construction temperature of the 4 warm-mix modified asphalts and the construction temperature change before and after adding the warm-mix agent can be further determined by the viscosity-temperature curve as shown in table 6:
TABLE 6 construction temperature and temperature reduction amplitude of 4 warm-mix modified asphalts determined by the present invention and conventional method
In this embodiment, the viscosity-temperature curves obtained by the conventional method and the test of the present invention have different forms, and it can be seen from comparing fig. 11 and fig. 12 that the viscosity-temperature curves obtained by the conventional method by measuring the viscosities of two points are actually a straight line in a semi-logarithmic coordinate system, and each viscosity-temperature curve in the present invention has an obvious curvature because it has more data points, and for this reason, the temperature widths obtained by the two viscosity-temperature curves in the two methods when intersecting with the horizontal lines of the two viscosity ranges of the "isothermal viscosity" are obviously different, and the temperature range width obtained by the present invention is obviously wider than that obtained by the conventional method.
In addition to the curvature problem, when the temperature is lower (around 135 ℃), the viscosity value given by the invention is lower than that given by the traditional method due to stronger non-Newtonian fluid characteristics of each warm mixing-modified asphalt, and the viscosity test values of the two methods are basically consistent when the temperature is around 210 ℃, so that the overall slope of the invention is smaller than that of the traditional method, and the overall position of the viscosity-temperature curve of the invention is lower than that of the viscosity-temperature curve obtained by the traditional method.
The example 3 shows that the viscosity reduction performance of the warm-mixing agent is seriously underestimated by the traditional viscosity testing method, generally, the requirement on the temperature reduction performance of the warm-mixing agent is generally about 15-30 ℃, and the mixing temperature reduction effect given by the traditional method is only 5 ℃ taking the surface active type warm-mixing agent A which is widely applied in China as an example, which is obviously unreasonable.
Compared with the invention, the cooling amplitude given by the traditional method is generally smaller by 40-50%, the estimation of the cooling performance of the warm-mix agent is too conservative, the heating temperature of the warm-mix SBS modified asphalt is higher, and the predicted value of the construction temperature given by the invention is closer to the actual construction.
Whether the predicted construction temperatures of 4 warm mix-modified asphalts of the present invention can be used to guide production will be exemplified in test example 1.
Test example 1
Whether the construction temperature of the total 8 kinds of asphalt, namely the 70#, 110# base asphalt, the SBS, the SBR modified asphalt and the A, B, C, D warm mix-SBS modified asphalt, determined by the asphalt apparent viscosity testing method with the variable shear rate can meet the actual production requirement is tested through the mixture void ratio test.
The purpose of this example is to verify that the construction temperature determined in accordance with the invention in examples 1, 2 and 3 does not affect the quality of the asphalt concrete produced at a later stage.
Specifically, 8 kinds of asphalts (4 kinds of warm mix modified asphalts formed by adding A, B, C, D warm mixing agents to 70# base asphalt, 110# base asphalt, SBS modified asphalt, SBR modified asphalt and SBS respectively) appearing in examples 1, 2 and 3 were prepared into asphalt mixture standard Marshall test pieces according to the same SMA-13 gradation and oilstone ratio (5.8%), the heating temperature of each asphalt was selected according to the mixing temperature determined in the previous examples 2 and 3, the temperature at the time of mold-loading was selected according to the previously obtained compaction temperature, and the conditions were the same except that the two temperature conditions were different, and the porosity (index reflecting the quality of asphalt concrete) of the prepared Marshall test pieces was examined to determine whether the temperature for preparing the test pieces (i.e., the construction temperature determined by the present invention) could satisfy the actual production requirements.
The SMA-13 mix composition used is shown in table 7; the manufacturing process of the Marshall test piece of the asphalt mixture is strictly carried out according to the manufacturing method of a standard Marshall test piece in the section of road engineering asphalt and asphalt mixture test procedure JTG E20-2011 of T0702 plus 2011 asphalt mixture test piece manufacturing method (compaction method) of the industry standard of the Ministry of transportation; the method for measuring the void ratio of the Marshall test piece of the asphalt mixture is strictly carried out according to a method for testing and calculating the void ratio in section of road engineering asphalt and asphalt mixture test procedure JTG E20-2011T 0705 and 2011 compacted asphalt mixture density test (table dry method) of the trade Specification of the Ministry of transportation.
TABLE 7 SMA-13 mineral aggregate grading
In this example, the influence of the construction temperature determined by the conventional method and the present invention on the quality (void ratio) of the asphalt concrete test piece was compared, except that the mixture was prepared at the construction temperature determined by the present invention, a group of parallel test pieces with identical conditions was prepared for each asphalt mixture according to the construction temperature determined by the conventional method as a control, and the void ratio of each asphalt mixture marshall test piece produced under the guidance of the construction temperature determined by the two methods is shown in table 8.
TABLE 8 porosity of Marshall test pieces of asphalt mixture produced under the guidance of construction temperature determined by two methods
According to the specification in technical Specification for road asphalt pavement construction (JTG F40-2004), the void ratio of the SMA-13 mixture reaching the standard is 3-4%, the construction temperature provided by the two methods is basically consistent for 70# and 110# base asphalt (the construction temperature is shown in Table 2), and the mixture is fully compacted under the guidance of the two methods.
For SBS and SBR modified asphalt, under the guidance of the construction temperature provided by the invention, the void ratio of each mixture test piece is slightly higher than that under the guidance of the BV method, but the void ratio control requirement of 3-4% of SMA-13 mixture produced by using SBS modified asphalt is still met; therefore, the invention does not cause obvious influence on the quality of the modified asphalt mixture, and the data discrete degree does not change obviously, which shows that the modified asphalt mixture product with the qualified quality can be produced by adopting the construction temperature provided by the invention, and simultaneously, the part with the higher construction temperature of 15-20 ℃ provided by the traditional method is meaningless, and the ageing of the asphalt and the useless energy consumption can be caused.
Although the void ratio of the corresponding mixture of the warm-mix asphalt and the SBS modified asphalt formed by adding the 4 types of warm-mix agents in the SBS modified asphalt does not exceed the standard at the construction temperature given by the two methods, the traditional method does not effectively reflect the cooling and viscosity reduction effects of the warm-mix agents and gives a relatively conservative result, but the construction temperature given by the invention can reasonably reflect the real viscosity reduction performance of the warm-mix agents and can guide the production of the warm-mix modified asphalt mixture with the qualified quality.
Test example 2
Taking the viscosity-temperature curve of 10 temperature points of the SBR modified asphalt obtained in the example 2 as an example, the testing efficiency of the method is compared with that of the traditional method.
The cylindrical flat plate test piece adopted by the invention consumes about 2.5g of asphalt, and because the test sample amount is small, the temperature control of the constant temperature cavity of the dynamic shear rheometer is flexible, when the viscosity-temperature curve test is carried out, the time is consumed for about 1min when the temperature rises by 10 ℃, the constant temperature of the single-temperature point test is kept for about 15min, and the single-point viscosity test time is about 1 min.
The viscosity-temperature curve of the SBR-modified asphalt at the temperature point 10 in fig. 8 was obtained, the time of the present invention took about 178 minutes, and the specific operation steps and time-consuming parameter statistics are shown in table 9, which are derived from the actual test statistics of experienced operators.
In the traditional method, 9-11g of asphalt samples are required to be filled in a test tube, a new asphalt sample is required to be filled for testing each time the size of a rotor is changed according to the requirements of road engineering asphalt and asphalt mixture test procedure (JTG E20-2011) T0625-2011 asphalt rotational viscosity test, and the test tube is required to be stored at a constant temperature for 90min after the new asphalt sample is filled, so that the traditional method needs to change the rotor for 3 times in a viscosity-temperature curve test of SBR modified asphalt at 10 temperature points, the total consumed time is 530 min, which is about 3 times of the consumed time of the method, the specific operation steps and consumed time parameter statistics are shown in Table 9, and the consumed time statistics are derived from real test statistics of operators with abundant experience.
TABLE 9 comparison of test efficiency of the present invention with conventional methods
Example 4
The invention provides an asphalt apparent viscosity testing method based on a dynamic shear rheometer, which is used for carrying out comprehensive scanning test on the viscosity-temperature-shear rate of asphalt by the dynamic shear rheometer after the temperature change mode and the system are established, and comprises the following steps:
1. heating the asphalt to be tested, and pouring the asphalt to be tested into an oblate columnar asphalt test piece with the height H being 1mm and the diameter D being 25mm by using a metal test mold; simultaneously entering a starting process of the dynamic shear rheometer, and setting the installation temperature of the test piece to be 60 ℃ after calibration;
2. placing an asphalt test piece into a dynamic shear rheometer, controlling an upper flat plate of a clamp to descend, clamping the asphalt test piece, setting a gap between the upper flat plate and the lower flat plate to be 1mm, and scraping extruded asphalt by using a hot scraper;
3. calling program codes, setting a temperature change mode to be that the temperature is increased from 70 ℃ by taking 10 ℃ as a step length to be increased to 160 ℃, and then the shear rate is within 0.01-100 s < -1 > at each temperature point, and uniformly increasing in 30 steps;
4. running a control program, and recording torque, shear rate and temperature information in the test process;
5. substituting the torque into a formula 1, calculating the apparent viscosity of the measured asphalt, and drawing a viscosity change curve of the asphalt;
6. and completing the test and closing the equipment.
The test results are shown in fig. 13 and fig. 14, the change situation of the apparent viscosity of the tested asphalt along with the temperature change and the shear rate change can be clearly obtained, and the asphalt apparent viscosity test method based on the dynamic shear rheometer provided by the invention has important practical significance in improving the accuracy and efficiency of the modified asphalt construction temperature prediction and deeply researching the comprehensive properties of the viscosity-temperature-shear rate of the asphalt.
While the present invention has been described in detail with reference to the illustrated embodiments, it should not be construed as limited to the scope of the present patent. Various modifications and changes may be made by those skilled in the art without inventive step within the scope of the appended claims.
Claims (4)
1. A method for testing the apparent viscosity of asphalt based on a dynamic shear rheometer is characterized by comprising the following steps:
s1: preparing an asphalt test piece, and setting the temperature in a test cavity of a dynamic shear rheometer as a test temperature;
s2: clamping an asphalt test piece, and applying torsion loading with a set rotating speed in a single direction to the asphalt test piece;
s3: testing the torque resistance of the parallel plate in the loading process, and calculating the apparent viscosity of the asphalt test piece at the current temperature through a formula 1;
s4: changing the temperature, and repeating the operations from S1 to S3 to obtain the viscosity-temperature curve and the temperature change mode of the tested asphalt test piece;
s5: changing the rotating speed omega p of an upper flat plate in the clamp according to the viscosity-temperature curve, testing the shearing rate, and establishing a system of a torsion loading mode under the specified shearing rate;
s6: setting a temperature rise path and a shear rate change path in sequence through the mode established in the step S4 and the system established in the step S5, and completing a temperature scanning test of viscosity, a shear rate scanning test of viscosity and a coordination scanning test of viscosity with respect to temperature and shear rate;
s7: recording test data and ending the test;
wherein, the formula 1 is
Wherein, the polar inertia moment of the top surface of the Ip-25 mm cylindrical asphalt test piece is a fixed value;
t-the resisting torque and the test value of the upper flat plate in the test piece selecting process;
h-25 mm of height of the cylindrical asphalt test piece, 1mm, fixed value;
the testing rotating speed and the set value set by the omega p-DSR are set;
eta-viscosity of the measured asphalt.
2. The method for testing the apparent viscosity of the asphalt based on the dynamic shear rheometer as claimed in claim 1, wherein the method for preparing the asphalt test piece in the step S1 is as follows: the asphalt to be tested is poured into an oblate asphalt test piece with the height H being 1mm and the diameter D being 25mm by using a metal test mould or a silica gel mould.
3. The method for testing the apparent viscosity of asphalt based on dynamic shear rheometer according to claim 1, wherein the clamping in step S2 is performed by: and putting the asphalt test piece into a dynamic shear rheometer, controlling the upper flat plate of the clamp to descend, clamping the asphalt test piece, setting the gap between the upper flat plate and the lower flat plate to be 1mm, and scraping the extruded asphalt by using a hot scraper.
4. The method for testing the apparent viscosity of the asphalt based on the dynamic shear rheometer of claim 1, wherein in the step S2, during the torsion loading, the lower plate of the clamp is fixed, and the upper plate rotates at a constant speed at a set angular speed ω p.
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