JP5051847B2 - Evaluation method and apparatus for asphalt mixture - Google Patents

Description

The present invention, which relates to the evaluation method and evaluation equipment of the asphalt mixture, in particular those suitable for the development and design of asphalt mixture.

  The asphalt mixture is mainly composed of bituminous material and aggregate. In designing the composition of the asphalt mixture, a material test is performed for each of these two types of materials. When this material test is completed, the mixture of these two types of materials is tested to evaluate the flow resistance and the like. It will be.

  The flow resistance of asphalt mixtures has heretofore been evaluated by dynamic stability obtained by performing a wheel tracking test (see, for example, Patent Document 1 and Non-Patent Document 1). In this wheel tracking test, a test wheel is applied to the surface of a 300 mm square × 50 mm thick asphalt mixture plate surface, and a horizontal back-and-forth motion is repeatedly applied to determine dynamic stability from the amount of deformation per unit time.

  Further, in designing a structure using an asphalt mixture, the elastic modulus of the asphalt mixture is evaluated.

  The elastic modulus of the asphalt mixture has heretofore been obtained from an indirect tensile mode test (see, for example, Non-Patent Document 2). In this indirect tensile mode test, the vertical load, the vertical displacement and the horizontal displacement of the specimen when a cyclic load is applied in the vertical direction with a cylindrical specimen having a diameter of about 100 mm and a thickness of about 50 mm lying on its side. To determine the elastic modulus. If the Poisson's ratio is known, the shear elastic modulus can be obtained. When the temperature of the specimen became 40 ° C. or higher, the specimen became soft, so that there was a drawback that the test accuracy dropped sharply and the test could not be performed.

Similar to this indirect tensile mode test is the American Association of State Highway and Transportation Officials test (AASHTO).
Designation 320-03). This is a horizontal displacement using a test device that shears the top and bottom surfaces in a horizontal direction while controlling the vertical load so that vertical movement of the upper and lower surfaces of the cylindrical specimen of asphalt mixture with a diameter of 150 mm and a thickness of 38 mm to 50 mm does not occur. This is a test for measuring a vertical load and a horizontal load to obtain a shear elastic modulus and a plastic shear strain.
JP 2006-170680 A Japan Road Association Pavement Test Method Handbook separate volume pp117-134 Japan Road Association Pavement Test Method Handbook separate volume pp249-259

  By the way, on an actual asphalt paved road, the temperature in summer may exceed 60 ° C, and torsional shear may occur. However, in the above test method, the rigidity, durability and fluidity of these are directly measured. I could not ask. That is, until now, there has been no evaluation method that can appropriately evaluate the rigidity, durability, and fluidity of the asphalt mixture by torsional shearing at high temperatures.

  In addition, in order to perform the wheel tracking test of Patent Document 1 and Non-Patent Document 1, a special test device is required for repeatedly applying horizontal back-and-forth motion by applying a test wheel to the surface of the asphalt mixture plate specimen. There was a drawback. Further, the test specimen that can be handled by the test apparatus is a plate specimen of an asphalt mixture having a size of 300 mm square x 50 mm thickness, and there is a disadvantage that a large specimen cannot be handled.

  Furthermore, in the indirect tension mode test of Non-Patent Document 2 and similar methods, when the temperature of the specimen becomes 40 ° C. or higher, the specimen becomes soft, so that there is a drawback that the test accuracy drops sharply and the test cannot be performed. In addition, the specimen that can be handled by the test apparatus is a cylindrical specimen of an asphalt mixture having a diameter of 150 mm and a thickness of 38 mm to 50 mm. In this case, there is also a drawback that a large specimen cannot be handled.

The present invention has been made in view of such circumstances, and an asphalt mixture evaluation method and evaluation device capable of appropriately evaluating the rigidity, durability, and fluidity of the asphalt mixture by torsional shearing at high temperatures. It is intended to provide a device.

By the way, when evaluating the flow resistance of the specimen based on the response of the specimen when twisted around the axis of the specimen formed into a cylindrical shape of the asphalt mixture, the flow resistance of the specimen is measured. The relationship between the cumulative rotation angle and the number of times of loading at each torque, which is an index of sexuality, changes as the torque is repeatedly loaded until it exceeds the elastic range. Accordingly, the present invention is an evaluation method of asphalt mixture, when the asphalt mixture repeatedly loading while increasing the torque of the order added twist around the axis of the specimen was formed into a cylindrical shape stepwise The fluid resistance of the specimen is evaluated based on the relationship between the cumulative rotation angle at each torque and the number of times of loading .

According to the present invention, loading the accumulated rotation angles of the respective torque when the asphalt mixture repeatedly loading while increasing the torque of the order added twist around the axis of the specimen was formed into a cylindrical shape stepwise Since the flow resistance of the specimen is evaluated based on the relationship with the number of times, it is possible to evaluate according to the actual situation by directly obtaining the torsional shear that may occur on an actual asphalt paved road. .

  In addition, in order to perform the wheel tracking test of Patent Document 1 and Non-Patent Document 1, a special test device is required for repeatedly applying horizontal back-and-forth motion by applying a test wheel to the surface of the asphalt mixture plate specimen. However, the present invention does not require such a special test apparatus. Further, in this test apparatus, the size of the specimen that can be handled is a plate specimen of an asphalt mixture having a size of 300 mm square x 50 mm thickness, and there is a disadvantage that a large specimen cannot be handled. There is no limit.

  Furthermore, in the indirect tension mode test of Non-Patent Document 2 and the similar method, when the temperature of the specimen becomes 40 ° C. or higher, the specimen becomes soft, so that there is a drawback that the test accuracy drops sharply and the test cannot be performed. In the present invention, even when the temperature of the specimen exceeds 60 ° C., the test accuracy does not drop sharply and the test cannot be performed. Moreover, the size of the specimen that can be handled by this test apparatus is a cylindrical specimen of an asphalt mixture having a diameter of 150 mm and a thickness of 38 mm to 50 mm. In this case, there was a drawback that a large specimen could not be handled. Then there is no such restriction.

As a result, under high temperature, so that the we that liquidity in torsional shear asphalt mixtures can be appropriately evaluated.

In this case, in order to accurately determine the flow resistance of the specimen, it is preferable to use a torque indicating the relationship between the sudden change in the cumulative rotation angle and the number of times of loading. Therefore, as in the invention of claim 2, wherein the flow resistance is Rukoto evaluated in torque when the accumulated rotation angle in relation to the loading times and the accumulated rotation angle is rapidly increased is preferred.

According to the second aspect of the present invention, the flow resistance is evaluated by the torque when the cumulative rotational angle suddenly increases in the relationship between the cumulative rotational angle and the number of times of loading. By grasping the torque indicating the relationship between the sudden change in the cumulative rotation angle and the number of times of loading, the fluid resistance of the specimen can be more accurately evaluated.

  By the way, the torsional rigidity of the specimen needs to be obtained in its elastic region, while the durability needs to be obtained in a region beyond its plastic region. Therefore, as in the invention according to claim 3, the torsion of the specimen is based on the relationship between the torque and the rotation angle when the torque for applying the torsion to the specimen is monotonously increased. It is preferable to evaluate at least one of rigidity and durability.

  According to the invention described in claim 3, based on the relationship between the torque and the rotation angle when the torque for applying the torsion to the specimen is monotonously increased and loaded, the torsional rigidity of the specimen and Since at least one of the durability is evaluated, the torsional rigidity of the specimen can be reliably determined in its elastic range, and the durability can be reliably determined beyond the plastic range, thereby Both can be accurately evaluated.

  Further, in order to accurately obtain the torsional rigidity of the specimen, it is preferable to use the initial response in the elastic proportional range. Therefore, as in the invention described in claim 4, it is preferable that the torsional rigidity is evaluated by a shear elastic modulus calculated using a value near an initial value in the relationship between the torque and the rotation angle.

  According to the invention of claim 4, the torsional rigidity is evaluated by a shear elastic modulus calculated using a value near an initial value in the relationship between the torque and the rotation angle. It can be obtained accurately in the elastic proportional range, and the torsional rigidity of the specimen can be evaluated more accurately.

  Preferably, the durability is evaluated by a peak value of the torque in the relationship between the torque and the rotation angle.

  According to the invention described in claim 5, since the durability is evaluated by the peak value of the torque in the relationship between the torque and the rotation angle, the durability can be evaluated more accurately.

  On the other hand, the relationship between the torque and the rotation angle, which is an index of the torsional rigidity of the specimen, becomes constant by repeatedly loading the torque in the elastic proportional range. Therefore, as in the invention described in claim 6, based on the relationship between each torque and the rotation angle when repeatedly loading while increasing the torque for applying the torsion to the specimen in a stepwise manner, the specimen It is preferable to evaluate the torsional rigidity.

  According to the sixth aspect of the present invention, the torsion of the specimen is based on the relationship between the torque and the rotation angle when repeatedly loading while increasing the torque for applying the torsion to the specimen. Since the rigidity is evaluated, it becomes possible to accurately evaluate the torsional rigidity of the specimen by using the relationship between the torque and the rotation angle that are made constant.

  In this case, in order to accurately obtain the torsional rigidity of the specimen, it is preferable to use the final response at each torque at which the relationship between the most constant torque and the rotation angle is obtained. Therefore, as in the invention described in claim 7, it is preferable that the torsional rigidity is evaluated by a shear elastic modulus calculated by using a value near the final value for each torque in the relationship between each torque and the rotation angle. .

  According to the invention of claim 7, the torsional rigidity is evaluated by a shear elastic modulus calculated using a value near the final value for each torque in the relationship between each torque and the rotation angle. Using the relationship between each torque and the rotation angle, a more accurate evaluation of the torsional rigidity of the specimen can be performed.

ここに、Ｇはせん断弾性係数、Ｈは供試体高さ、Ｒは供試体半径、Ｔはトルク、Δθは回転角を示す。 As in the invention described in claim 8, it is preferable that the shear elastic modulus is expressed by the following equation.

Here, G is the shear modulus, H is the specimen height, R is the specimen radius, T is the torque, and Δθ is the rotation angle.

  According to the invention described in claim 8, since the shear elastic modulus is expressed by the above formula (Equation 2), the shear elastic modulus is used to further accurately evaluate the torsional rigidity of the specimen. Will be able to do.

As in the ninth aspect of the invention, the evaluation is preferably performed in a state where the specimen is immersed in a thermostatic bath set at a temperature higher than 0 ° C. and lower than 100 ° C.

According to invention of Claim 9 , since the said evaluation is performed in the state immersed in the thermostat set to the temperature higher than 0 degreeC and lower than 100 degreeC, the temperature in summer is set to 60 degreeC. The evaluation according to the actual situation of the asphalt paved road in Japan that exceeds.

The invention according to claim 10 is a loading platform erected on a base, a specimen configured to be detachably set on the loading platform after forming an asphalt mixture into a cylindrical shape, and the loading platform described above A torque loading unit for loading a torque for applying torsion around the axis of the specimen set in the control unit, and a control unit for controlling the operation of the torque loading unit so as to repeatedly load while increasing the torque stepwise And an asphalt mixture evaluation apparatus characterized by comprising:

According to the asphalt mixture evaluation device of the invention described in claim 10, the loading table erected on the base, and the asphalt mixture formed into a columnar shape so as to be detachably set on the loading table. The configured specimen, a torque loading unit for loading torque for applying a twist around the axis of the specimen set on the loading platform, and the torque so as to repeatedly load the torque stepwise. Since the control unit for controlling the operation of the loading unit is provided, the evaluation according to the actual situation can be performed by directly obtaining the torsional shear that may occur on the actual asphalt pavement.

  In addition, in order to perform the wheel tracking test of Patent Document 1 and Non-Patent Document 1, a special test device is required for repeatedly applying horizontal back-and-forth motion by applying a test wheel to the surface of the asphalt mixture plate specimen. However, the present invention does not require such a special test apparatus.

  Furthermore, in the indirect tension mode test of Non-Patent Document 2 and the similar method, when the temperature of the specimen becomes 40 ° C. or higher, the specimen becomes soft, so that there is a drawback that the test accuracy drops sharply and the test cannot be performed. In the present invention, even when the temperature of the specimen exceeds 60 ° C., the test accuracy does not drop sharply and the test cannot be performed.

As in the invention described in claim 11 , further comprising a load loading unit for loading a load in a direction perpendicular to the end surface of the specimen set on the loading platform , wherein the control unit increases the torque stepwise. when to cyclic loading, Rukoto controls also the operation of the load loading unit to loading the load is preferred.

According to an eleventh aspect of the present invention, the apparatus further includes a load loading unit that loads a load in a direction perpendicular to the end surface of the specimen set on the loading platform, and the control unit increases the torque stepwise. Since the operation of the load loading unit is also controlled so as to load the load when repeatedly loaded, the evaluation according to the actual situation can be performed by taking into account the load as occurs on an actual asphalt paved road. Will be able to.

As in the invention described in claim 12, it is preferable to provide a thermostatic bath capable of immersing the specimen.

According to the twelfth aspect of the invention, since the thermostatic bath capable of immersing the specimen is provided, by setting the thermostatic bath to a temperature higher than 0 ° C and lower than 100 ° C, Evaluation according to the actual situation of asphalt paved roads in Japan where the temperature exceeds 60 ° C can be performed.

According to the present invention, loading the accumulated rotation angles of the respective torque when the asphalt mixture repeatedly loading while increasing the torque of the order added twist around the axis of the specimen was formed into a cylindrical shape stepwise Since the flow resistance of the specimen is evaluated based on the relationship with the number of times, it is possible to evaluate according to the actual situation by directly obtaining the torsional shear that may occur on an actual asphalt paved road. .

  In addition, in order to perform the wheel tracking test of Patent Document 1 and Non-Patent Document 1, a special test device is required for repeatedly applying horizontal back-and-forth motion by applying a test wheel to the surface of the asphalt mixture plate specimen. However, the present invention does not require such a special test apparatus. Further, in this test apparatus, the size of the specimen that can be handled is a plate specimen of an asphalt mixture having a size of 300 mm square x 50 mm thickness, and there is a disadvantage that a large specimen cannot be handled. There is no limit.

  Furthermore, in the indirect tension mode test of Non-Patent Document 2 and the similar method, when the temperature of the specimen becomes 40 ° C. or higher, the specimen becomes soft, so that there is a drawback that the test accuracy drops sharply and the test cannot be performed. In the present invention, even when the temperature of the specimen exceeds 60 ° C., the test accuracy does not drop sharply and the test cannot be performed. Moreover, the size of the specimen that can be handled by this test apparatus is a cylindrical specimen of an asphalt mixture having a diameter of 150 mm and a thickness of 38 mm to 50 mm. In this case, there was a drawback that a large specimen could not be handled. Then there is no such restriction.

As a result, under high temperature, so that the we that liquidity in torsional shear asphalt mixtures can be appropriately evaluated.

According to the asphalt mixture evaluation device of the invention described in claim 10, the loading table erected on the base, and the asphalt mixture formed into a columnar shape so as to be detachably set on the loading table. The configured specimen, a torque loading unit for loading torque for applying a twist around the axis of the specimen set on the loading platform, and the torque so as to repeatedly load the torque stepwise. Since the control unit for controlling the operation of the loading unit is provided, the evaluation according to the actual situation can be performed by directly obtaining the torsional shear that may occur on the actual asphalt pavement.

  In addition, in order to perform the wheel tracking test of Patent Document 1 and Non-Patent Document 1, a special test device is required for repeatedly applying horizontal back-and-forth motion by applying a test wheel to the surface of the asphalt mixture plate specimen. However, the present invention does not require such a special test apparatus.

  Furthermore, in the indirect tension mode test of Non-Patent Document 2 and the similar method, when the temperature of the specimen becomes 40 ° C. or higher, the specimen becomes soft, so that there is a drawback that the test accuracy drops sharply and the test cannot be performed. In the present invention, even when the temperature of the specimen exceeds 60 ° C., the test accuracy does not drop sharply and the test cannot be performed.

Figure 1 is a schematic diagram showing the overall configuration of a test apparatus 1 for evaluating the asphalt mixture according to an embodiment of the present invention, FIG 2 is a shows to view the configuration of the specimen 4, (a ) Is a front view, and (b) is an AA cross-sectional view in (a). 3 and 4 are charts showing composition examples of the asphalt mixture constituting the specimen 4.

  As shown in FIG. 1, a test apparatus (corresponding to an evaluation apparatus) 1 for evaluating an asphalt mixture according to this embodiment mainly includes a loading table 3 erected on a base 2 and a loading table. A specimen 4 that is detachably set near the center of 3, and a vertical load loading unit (corresponding to a load loading unit) 5 that is disposed on the top of the loading table 3 and applies a vertical load to the upper surface of the specimen 4. A torque loading unit 6 that is arranged at the lower part of the loading table 3 and that applies a torque for applying a twist around the axis of the specimen 4; a thermostatic chamber 7 in which the specimen 4 is immersed; and a control unit 8 It is made up of.

  The loading table 3 includes an intermediate member 31, a lower member 32, a lower column 33 that stands upright on the base 2 and supports the intermediate member 31 and the lower member 32 at first and second predetermined heights, and an upper member 34, respectively. And an upper column 35 which stands upright on the intermediate member 31 and supports the upper member 34 at a third predetermined height.

  As shown in FIG. 2, the specimen 4 is obtained by forming an asphalt mixture 41 into a cylindrical shape having a diameter of about 100 to 200 mm and a thickness of about 50 to 200 mm. The upper and lower surfaces of the asphalt mixture 41 are respectively bonded to the adhesive 44. , 45 are fixed to flange-shaped upper and lower caps 42, 43. Holes 46 and 47 are opened at appropriate positions of the upper and lower caps 42 and 43, respectively. As the asphalt mixture 41, for example, drainage asphalt having a composition as shown in FIG. 3 and dense grain asphalt having a composition as shown in FIG. 4 are used for the test.

  The vertical load loading unit 5 includes a compressor 51, a pneumatic cylinder 54 that is reciprocally driven by compressed air from the compressor 51, a load meter 57 attached to a drive shaft of the pneumatic cylinder 54, and a lower portion of the load meter 57. And a biaxial piston 58 provided.

  The compressed air from the compressor 51 is supplied to and exhausted from the pneumatic cylinder 54 via pneumatic lines 55 and 56 each having an air regulator 52 and a pressure gauge 53 attached thereto. The biaxial piston 58 is connected to an upper loading plate 59 that passes through the intermediate member 31 and is attached immediately below the intermediate member 31. The upper loading plate 59 is formed with a hole (not shown). The hole and the hole 46 of the upper cap 42 are aligned in a plane, and then the upper loading plate 59 and the upper cap 42 are connected to each other. Bolt connection is possible.

  The torque loading unit 6 is provided at a hydraulic pump 61, a hydraulic cylinder 62 reciprocally driven by the hydraulic pump 61, a load meter 63 attached to a drive shaft of the hydraulic cylinder 62, and a front portion of the load meter 63. A torsion arm 64 that converts the reciprocating motion of the drive shaft of the hydraulic cylinder 62 into a torsional motion, and a torsional displacement meter 65 attached to the torsion arm 64 are provided. As the torsional displacement meter 65, for example, a winding wire displacement meter was used.

  The pressure oil from the hydraulic pump 61 is supplied to a servo valve 66 attached to the hydraulic cylinder 62 via a hydraulic line 66a. The torsion arm 64 passes through the lower member 32 with its rotation shaft interposed by a thrust bearing 67, and is connected to a lower loading plate 68 attached immediately above. A hole (not shown) is formed in the lower loading plate portion 68, and the lower loading plate 68 and the lower cap 43 are aligned with the hole 47 and the hole 47 of the lower cap 43 in a plane. The bolt can be connected.

  The thermostat 7 is immersed in a water tank 71 for immersing the specimen 4, a water pan 72 that receives water overflowing from the water tank 71, and an electric heater 73 that is stored in the water pan 72 and automatically controlled to a set temperature. And a submersible pump 74 for supplying the water (warm water) to the water tank 71. A thermometer 77 is provided at an appropriate place of the water tank 71 or the specimen 4.

  When the water tank 71 is submerged, the water adjusted to a predetermined temperature in the water pan 72 is supplied to the water tank 71 via the water line 76 by driving the submersible pump 74 and overflows from the water tank 71. The water is returned to the water pan 72 through the water line 75. When the water tank 71 is not submerged, the water in the water tank 71 may be collected in the water pan 72 via a water line provided in the lower part thereof.

  The control unit 8 includes a function generator 81, a servo amplifier 82, and a data logger 83. The function generator 81 can perform loading control at 0.01 to 10 Hz, and can be set to a monotonic loading (monotonically increasing) signal and a loading time of 0.1 seconds to an arbitrary value toward the servo amplifier 82, and It is possible to input a resting time of 0.1 second to an arbitrarily settable repetitive loading (for example, a harbor sign wave having a loading time of 0.1 second and a resting time of 0.6 seconds). The input signal may be a triangular wave, a rectangular wave, or other waveforms.

  A torque signal is input from the load meter 63 to the data logger 83, a torsion displacement signal is input from the torsion displacement meter 65, a vertical load signal is input from the load meter 57, and a temperature signal is input from the thermometer 77. The data logger 83 outputs a feedback signal to the servo amplifier 82. In FIG. 1, signal routes input from the sensors 63, 65, 57, and 77 to the data logger 83 are omitted for convenience.

  The servo amplifier 82 reciprocates the hydraulic cylinder 62 by operating the servo valve 66 of the hydraulic cylinder 62 based on the input signal from the function generator 81 and the feedback signal from the data logger 83. Thus, a predetermined torque for monotonous loading or repeated loading is generated. Further, by operating the pneumatic cylinder 54 using the air regulator 52 and the pressure gauge 53, the pneumatic cylinder 54 is reciprocated to generate a predetermined vertical load.

  In this way, torque is monotonously applied to the lower cap 43 by the torque loading unit 6 while applying a vertical load to the upper cap 42 by the vertical load applied by the vertical load loading unit 5 or stopping the vertical movement of the upper cap 42. The data logger 83 collects the measured values of the torque, the rotation angle of the lower cap 43 and the vertical load when the load is increased or repeatedly applied. From the data logger 83, the relationship between the loading time, the relationship between the vertical load and the loading time, the relationship between the rotation angle and the loading time, the relationship between the torque and the rotation angle, and the relationship between the vertical load and the rotation angle are shown. Each data is output. Based on these output data, the shear elastic modulus (torsional rigidity), torsional shear resistance (durability), and cumulative rotation angle of the asphalt mixture 41 when the monotonous loading test or repeated loading test is performed. (Flow resistance) is being evaluated.

  Here, a method for calculating the shear elastic modulus G using the test apparatus 1 will be described. FIG. 5 is an explanatory diagram showing the relationship between the force and displacement acting on the cylindrical specimen 4, FIG. 6 is an explanatory diagram showing the relationship between the stress and strain acting on the microelements, and FIG. 7 is a shear stress cylinder. It is explanatory drawing which shows distribution on a coordinate. Hereinafter, in each figure, R is the radius of the specimen 4, H is the height, ΔH is the amount of change in height, T is the torque, Fv is the vertical load, Δθ is the rotation angle, and r is the radial direction (r direction). The distance, z is the distance in the vertical direction (z direction), and θ is the angle in the circumferential direction (θ direction).

  In the test apparatus 1, the vertical load Fv is loaded on the upper surface of the specimen 4 and the torque T is loaded on the lower surface. 4 is preferably loaded, and FIG. 5 assumes such a case.

となる。 As shown in FIGS. 5 and 6, when the stress acting on the minute elements of the cylindrical specimen 4 is σ _r , σ _θ , σ _z , τ _zr , τ _zθ , τ _θr , the torque T applied to the shaft is ,

It becomes.

Consider the shear stress τ _zθ acting on the specimen 4.

At this time, from the above equation, it is first necessary to assume the distribution of the shear stress τ _{zθ in} the r direction. For example, as shown in the lower part of FIG. 7, the shear stress τ _zθ is considered to have a linear distribution with respect to r. When,
τ _zθ (r) = αr
It is. Α is a coefficient.

最大値τ_ｍａｘはｒ＝Ｒのときで、

となる。 Therefore,

The maximum value τ _max is when r = R,

It becomes.

となる。 Further, assuming that the shear stress at r = R / 2 is an average shear stress τ _ave ,

It becomes.

となる。 Further, assuming that the area average is the average shear stress τ _ave ,

It becomes.

となる。 Next, if the displacements of the microelements of the cylindrical specimen 4 are u _r , u _θ , u _z and the strains are ε _r , ε _θ , ε _z , γ _rz , γ _zθ , γ _rθ ,

It becomes.

となる。 The shear strain γ _zθ is

It becomes.

となる。 The maximum value when r = R

It becomes.

となる。 As for the average values γ _{zθ and ave} , assuming that γ _zθ increases linearly with r from the axis center (Equation 12),

It becomes.

となる。 Considering γ _zθ at the position of r = R / 2 as an average value, from ( _Equation 12),

It becomes.

となる。 The shear strain ε _z is

It becomes.

したがって、以下、
（１）τ_ａｖｅとγ_ａｖｅとして平均値（数１０、数１５）を用いる場合を左側に表示し、
（２）τ_ａｖｅとγ_ａｖｅとしてｒ＝Ｒ／２での値（数８、数１６）を用いる場合を右側に表示すると、

となる。 That is, to obtain the shear elastic modulus G, assuming a linear elastic body,

Therefore,
(1) The case where average values ( _Equation 10 and Equation 15) are used as τ _ave and γ _ave is displayed on the left side,
(2) When the case of using values (Equation 8 and Equation 16) at r = R / 2 as τ _ave and γ _ave is displayed on the right side,

It becomes.

  Since the height H and radius R of the specimen 4 are known from the final equation of (Equation 19), it can be understood that the shear elastic modulus G can be calculated by giving the torque T and the rotation angle Δθ.

  FIG. 8 and FIG. 9 are flowcharts showing procedures for performing various tests on the specimen 4 using the test apparatus 1. This will be described below.

  In the main flow shown in FIG. 8A, first, the specimen 4 is installed between the upper and lower loading plates 59 and 68 of the loading table 3 (step S1). Here, in the subflow shown in FIG. 4B, the asphalt mixture 41 having the composition shown in FIGS. 3 and 4 is formed in a cylindrical shape. The upper cap 42 is bonded to the upper surface of the asphalt mixture 41 with the adhesive 44, and the lower cap 43 is bonded to the lower surface with the adhesive 45 to obtain the specimen 4 (step S11). Next, the specimen 4 is set on the loading table 3, and the upper and lower caps 42 and 43 and the upper and lower loading plates 59 and 68 are fixed with bolts while adjusting the vertical movement of the upper loading plate 59 (step S12). Then, the water stored in the water pan 72 is heated to a predetermined temperature (for example, 20 ° C. or 60 ° C.) by the electric heater 73, and the hot water is supplied from the water pan 72 to the water tank 71 by the submersible pump 74. The temperature of the specimen 4 is adjusted (step S13).

  Returning to the main flow, it is selected whether to perform a monotonous loading test or a repeated loading test (step S2). Now, a monotonous loading test is performed (step S3). At this time, as shown in the subflow shown in FIG. 9A, an arbitrary vertical load Fv is applied by the vertical loading unit 5 or the vertical movement of the upper cap 42 is fixed (step S31). Here, when applying the vertical load Fv, the compressed air from the compressor 51 of the vertical load loading unit 5 is controlled using the air regulator 52 and the pressure gauge 53, and the pneumatic cylinder 54 is controlled by the controlled compressed air. The reciprocating drive is performed, and the vertical load Fv is loaded on the upper surface of the specimen 4 through the load meter 57, the biaxial piston 58 and the upper loading plate 59. Next, the initial value of the torque T is read by the load meter 63, the initial value of the rotation angle Δθ is read by the torsional displacement meter 65, the initial value of the vertical load Fv is read by the load meter 57, and the temperature of the specimen 4 is read by the thermometer 77. The initial value of Te is read (step S32).

  Next, torque T is applied to the lower cap 43 by the torque loading unit 6 and torsional shearing is started (step S33). At this time, the servo amplifier 82 operates the servo valve 66 of the hydraulic cylinder 62 of the torque loading unit 6 based on the input signal from the function generator 81 and the feedback signal from the data logger 83, and the hydraulic cylinder 62. Are reciprocally driven, and a monotonously increasing torque T is loaded on the lower surface of the specimen 4 via the load meter 63, torsion arm 64, torsion displacement meter 65, thrust bearing 67, and lower loading plate 68. During torsional shear, torque T is measured with load meter 63, rotation angle Δθ is measured with torsion displacement meter 65, vertical load Fv is measured with load meter 57, and temperature Te of specimen 4 is measured with thermometer 77. (Step S34). Then, the test at the time when the rotation angle Δθ reaches 45 degrees or the specimen 4 is torsionally broken is finished (step S35), and the process returns.

  10 to 12 are graphs showing actual measurement values when a monotonous torsion test is performed. FIG. 10 is a drainage asphalt mixture (test temperature 20 ° C., water immersion), and FIG. 11 is a drainage asphalt mixture. In the case of (specimen temperature 60 ° C., water immersion), FIG. 12 shows the case of a dense particle size asphalt mixture (specimen temperature 20 ° C., water immersion). This will be described below.

(1) In the case of drainage asphalt mixture (specimen temperature 20 ° C., water immersion) In the relationship between the torque T shown in the upper left of FIG. 10 and the loading time t, if the loading time t is less than 20 seconds, the torque T is It gradually increases in proportion to the time t, and shows a peak when T = 380 N · m in 20 seconds. Thereafter, the torque T decreases rapidly, and T = 0 N · m in 30 seconds. ing. This means that the specimen 4 was broken at t = 20 seconds.

  Here, in the relationship between the vertical load Fv and the loading time t shown in the upper right of the figure, it is assumed that the vertical load Fv is not applied and the upper cap 42 is fixed. Due to the reaction force when the torque T is applied, the vertical load Fv gradually increases in proportion to the loading time t when the loading time t is less than 20 seconds. Then, a peak is shown when the vertical load Fv = 20N in 20 seconds, and then the vertical load Fv decreases rapidly, and after 30 seconds, the vertical load Fv = 0N. This is consistent with the specimen 4 breaking at t = 20 seconds.

  Further, also in the relationship between the rotation angle Δθ and the loading time t shown in the center of the figure, when the loading time t = less than 20 seconds, the rotation angle Δθ gradually increases in proportion to the loading time t. A peak is shown when Δθ = 45 degrees in seconds, and the rotation angle Δθ = 45 degrees (constant) thereafter. This also corresponds to the fact that the specimen 4 broke at t = 20 seconds.

  When the relationship between the torque T and the rotation angle Δθ is obtained, it is as shown in the lower left of the figure. That is, since the initial rotation angle θ and the torque T are in a proportional relationship, by substituting these initial values (or values in the vicinity thereof) into the final formula of (Equation 19), the shear elasticity of the specimen 4 is obtained. The coefficient G can be calculated. Thereby, torsional rigidity is evaluated. Further, the rotation angle Δθ = 5 degrees and the peak of torque T = 380 N · m, and the shear resistance of the specimen 4 can be obtained by this peak value. Thereby, durability is evaluated.

  Further, when the relationship between the vertical load Fv and the rotation angle Δθ is obtained, it is as shown in the lower right of FIG. That is, the peak of the vertical load Fv = 20 N is obtained at the rotation angle Δθ, and the dilatancy (volume change due to shear) characteristic of the specimen 4 can be obtained by this peak value.

(2) In the case of drainage asphalt mixture (specimen temperature 60 ° C., water immersion) In the relationship between the torque T shown in the upper left of FIG. 11 and the loading time t, if the loading time t is less than 5 seconds, the torque T is It gradually increases in proportion to time t, and shows a peak when T = 80 N · m in 5 to 10 seconds. Thereafter, torque T gradually decreases, and T = 0 N · m in 20 seconds. It has become. This means that the specimen 4 was broken at t = 10 seconds.

  Further, in the relationship between the vertical load Fv and the loading time t shown in the upper right of the figure, the vertical load Fv is not applied and the upper cap 42 is fixed. At this time, due to the reaction force when the torque T is applied, the vertical load Fv slightly increases in proportion to the loading time t when the loading time t is less than 2 seconds. Then, a peak is shown when the vertical load Fv = 5N in 2 to 10 seconds, and thereafter, the vertical load Fv rapidly decreases and becomes the vertical load Fv = 0N. This is consistent with the specimen 4 breaking at t = 10 seconds.

  Further, in the relationship between the rotation angle Δθ and the loading time t shown in the center of the figure, when the loading time t is less than 35 seconds, the rotation angle θ gradually increases in proportion to the loading time t. A peak is shown when the rotation angle Δθ = 45 degrees in seconds, and then the rotation angle Δθ = 45 degrees (constant). As described above, this does not coincide with the fact that the specimen 4 was broken at the loading time t = 10 seconds. This is presumed to be due to the stickiness of the asphalt mixture 41 at a high temperature.

  When the relationship between the torque T and the rotation angle Δθ is obtained, it is as shown in the lower left of the figure. That is, since the initial rotation angle Δθ and the torque T are in a proportional relationship, the shear elasticity of the specimen 4 can be obtained by substituting these initial values (or values in the vicinity thereof) into the final formula of the above (Equation 19). The coefficient G can be calculated. Thereby, it is evaluated that the torsional rigidity is considerably smaller than in the case of (1). Further, the torque T = 80 N · m at the rotation angle θ = 5 degrees, and the shear resistance of the specimen 4 can be obtained by this peak value. Thereby, it is evaluated that the durability is considerably smaller than in the case of (1).

  Further, when the relationship between the vertical load Fv and the rotation angle Δθ is obtained, it is as shown in the lower right of FIG. That is, the rotation angle Δθ = 5 degrees and the peak of the vertical load Fv = 5N, and the dilatency characteristic of the specimen 4 can be obtained by this peak value.

(3) In the case of a dense particle size asphalt mixture (specimen temperature 20 ° C., water immersion) In the relationship between the torque T and the loading time t shown in the upper left of FIG. 12, if the loading time t is less than 35 seconds, the torque T is It gradually increases in proportion to the time t, and shows a peak when T = 680 N · m in 35 seconds. Thereafter, the torque T decreases rapidly, and T = 0 N · m in 40 seconds. ing. This means that the specimen 4 was broken at t = 35 seconds.

  Further, in the relationship between the vertical load Fv and the loading time t shown in the upper right of the figure, the vertical load Fv is not applied here, and the upper cap is fixed. At this time, due to the reaction force when the torque T is applied, the vertical load Fv slightly increases in proportion to the loading time t when the loading time t is less than 5 seconds. A peak is shown when the vertical load Fv = 20 N in 5 to 10 seconds, and then the vertical load Fv decreases rapidly, and after 20 seconds, the vertical load Fv = 0 N. This is consistent with the specimen 4 breaking at t = 35 seconds.

  Further, in the relationship between the rotation angle Δθ and the loading time t shown in the center of the figure, when the loading time t is less than 35 seconds, the rotation angle θ gradually increases in proportion to the loading time t. A peak is shown when Δθ = 45 degrees in seconds, and the rotation angle Δθ = 45 degrees (constant) thereafter. This also corresponds to the fact that the specimen 4 broke at t = 35 seconds.

  When the relationship between the torque T and the rotation angle Δθ is obtained, it is as shown in the lower left of the figure. That is, since the initial rotation angle Δθ and the torque T are in a proportional relationship, the shear elasticity of the specimen 4 can be obtained by substituting these initial values (or values in the vicinity thereof) into the final formula of the above (Equation 19). The coefficient G can be calculated. Thus, although the torsional rigidity is slightly smaller than in the case of (1), it is evaluated that the torsional rigidity is larger than in the case of (2). Further, the rotation angle Δθ = 5 degrees and the peak of torque T = 680 N · m, and the shear resistance of the specimen 4 can be obtained by this peak value. Thereby, it is evaluated that there is greater durability than in the cases of (1) and (2).

  Further, when the relationship between the vertical load and the rotation angle is obtained, it is as shown in the lower right of the figure. That is, the rotation angle Δθ = 5 degrees and the peak of the vertical load Fv = 20 N, and the dilatency characteristic of the specimen 4 can be obtained by this peak value.

  On the other hand, it is assumed that the repeated loading test is performed by the selection in step S2 in the main flow of FIG. 8A (step S4). Here, in the subflow shown in FIG. 9B, an arbitrary vertical load Fv is applied by the vertical loading unit 5 or the vertical movement of the upper cap 42 is fixed (step S41). Here, when applying the vertical load Fv, the compressed air from the compressor 51 of the vertical load loading unit 5 is controlled using the air regulator 52 and the pressure gauge 53, and the pneumatic cylinder 54 is controlled by the controlled compressed air. The reciprocating drive is performed, and the vertical load Fv is loaded on the upper surface of the specimen 4 through the load meter 57, the biaxial piston 58 and the upper loading plate 59.

  Next, the repetitive torque T, the loading time t, and the loading number N are set (step S42). The initial value of the torque T is read by the load meter 63, the initial value of the rotation angle Δθ is read by the torsional displacement meter 65, the initial value of the vertical load Fv is read by the load meter 57, and the temperature Te of the specimen 4 is measured by the thermometer 77. The initial value is read (step S43).

  Next, the torque loading unit 6 starts torsion repeatedly (step S44). At this time, the servo amplifier 82 operates the servo valve 66 of the hydraulic cylinder 62 of the torque loading unit 6 based on the input signal from the function generator 81 and the feedback signal from the data logger 83, and the hydraulic cylinder 62. And a torque T is loaded on the lower surface of the specimen 4 through the load meter 63, the torsion arm 64, the torsion displacement meter 65, the thrust bearing 67 and the lower loading plate 68 so as to be repeated at a predetermined timing. During repeated torsion, the load meter 63 measures the torque T, the torsion displacement meter 65 measures the rotation angle Δθ, the load meter 57 measures the vertical load Fv, the unillustrated counter measures the number of loadings N, and the temperature The temperature Te of the specimen 4 is measured with a total of 77 (step S45).

  Then, the test at the time when the rotation angle Δθ = 45 degrees is reached or the specimen 4 is torsionally broken is finished (step S46), and the process returns. If the rotation angle Δθ does not reach 45 degrees in step S46 and the specimen 4 reaches the predetermined number of loadings without being twisted, the test is terminated at that point (step S47) and the process returns. .

FIG. 13 and FIG. 14 are graphs showing estimations when a repeated torsion test is performed, and FIG. 13 shows repeated loading of a minute torque (when a plurality of torques T _q1 , T _q2 ,... T _qn are loaded). FIG. 14 shows repeated loading of medium torque (when torque T _q1 <T _q2 ). This will be described below.

(1) Repeated loading of minute torque (when loading a plurality of torques T _q1 , T _q2 ,... T _qn )
In the relationship between the torque T and the rotation angle Δθ shown in FIG. 13, when the minute torques T _q1 , T _q2 ,... T _qn are repeatedly loaded on the specimen 4, the rotation angle Δθ and the torques T _q1 , T _q2 , ... Specimen 4 by substituting the value (final value of each torque or a value in the vicinity thereof) at the time when the slope formed with T _qn becomes substantially constant into the final equation of (Equation 19). Each shear modulus G can be calculated to evaluate torsional stiffness.

(2) Repetitive loading of medium torque (when torque T _q1 <T _q2 )
As shown in the upper left of FIG. 14, in the relationship between the torque T and the rotation angle Δθ when the medium torque T _q1 is loaded on the specimen 4, the inclination between the rotation angle Δθ and the torque T _q1 gradually increases. As shown in the upper right of FIG. 14, in the relationship between the torque and the rotation angle when the medium torque T _q2 is loaded on the specimen 4, the inclination between the rotation angle θ and the torque T _q1 is It gradually becomes smaller and does not become constant.

Accordingly, in the relationship between the loading number N and the cumulative rotation angle θ shown in the lower part of FIG. 14, when the torque T _q1 is loaded, the cumulative rotation angle θ is constant, whereas the torque T _q2 is loaded. In this case, the cumulative rotation angle θ increases rapidly at a certain loading number N. Thereby, the fluid resistance of the specimen 4 is evaluated.

  As described above, according to this embodiment, the specimen 4 is based on the response of the specimen 4 when a twist is applied around the axis of the specimen 4 in which the asphalt mixture 41 is formed into a cylindrical shape. Since at least one of the shear elastic modulus G, flow resistance and durability is evaluated, the torsional shear that may occur on actual asphalt pavement roads can be directly calculated so that evaluation according to the actual situation can be performed. Become.

  In addition, in order to perform the wheel tracking test of Patent Document 1 and Non-Patent Document 1, a special test device is required for repeatedly applying horizontal back-and-forth motion by applying a test wheel to the surface of the asphalt mixture plate specimen. However, in this embodiment, such a special test apparatus is not necessary. In addition, the test apparatus of Patent Document 1 and Non-Patent Document 1 has a defect that the size of the specimen that can be handled is a plate specimen of an asphalt mixture having a size of 300 mm square x 50 mm, and cannot handle a large specimen. In this embodiment, there is no such limitation.

  Furthermore, in the indirect tension mode test of Non-Patent Document 2 and the similar method, when the temperature of the specimen becomes 40 ° C. or higher, the specimen becomes soft, so that there is a drawback that the test accuracy drops sharply and the test cannot be performed. In this embodiment, even when the temperature of the specimen 4 exceeds 60 ° C., the test accuracy does not drop sharply and the test cannot be performed. In addition, the size of the specimen that can be handled by a test apparatus such as Non-Patent Document 2 is a cylindrical specimen of an asphalt mixture having a diameter of 150 mm and a thickness of 38 mm to 50 mm. In this case, there is a drawback that a large specimen cannot be handled. However, there is no such limitation in this embodiment.

  As a result, it is possible to appropriately evaluate the rigidity, durability, and fluidity of the asphalt mixture 41 due to torsional shearing at high temperatures, so that it is possible to perform evaluation according to the actual situation.

In the above embodiment, the evaluation is performed based on the relationship between the torque T and the rotation angle Δθ. However, from the equation (Equation 19), the torque T and the rotation angle Δθ are expressed by the shear stress τ _ave and the shear strain. Of course, the evaluation may be performed by replacing each with γ _ave .

In the above embodiment, wherein the, first is the r direction of the distribution of shear stress tau _{z [theta]} was assumed linear elastic, for example, as shown in the upper part of FIG. 7, the tau _{z [theta]} is matter r of equation (3) Considering a uniform distribution (perfect plasticity)
τ _zθ (r) = τ _max = const
It is.

となるから、平均せん断応力τ_ａｖｅは、

となる。 Therefore,

_Therefore , the average shear stress τ _ave is

It becomes.

  Moreover, in the said embodiment, although the side pressure of the specimen 4 is made into atmospheric pressure (constant), it is good also as giving side pressure repeatedly by making side pressure variable. Moreover, although the upper cap 42 of the specimen 4 is restrained, the axial load that changes statically or repeatedly may be applied by reciprocating the vertical load loading unit 5. By conducting these experiments, the specimen 4 can be further evaluated. Further, the drive source of the vertical load loading unit 5 may be a hydraulic cylinder or the like instead of the compressed air cylinder 54, and the drive source of the torque load unit 6 may be a compressed air cylinder or the like instead of the hydraulic cylinder 62.

  Moreover, in the said embodiment, although the specimen 4 is immersed in the thermostat 7 and temperature control is performed, it is good also as air-conditioning around the specimen 4 being performed.

  Further, in the above embodiment, a winding-type wire displacement meter is used as the torsional displacement meter 65. However, instead of this, for example, a laser displacement meter is used so that the measurement accuracy of the minute rotation angle Δθ of the specimen 4 is measured. Can be further improved. Furthermore, the volume change amount ΔV of the specimen 4 and the loss amount ΔW of the specimen 4 may be measured. Thus, a more precise evaluation of the specimen 4 can be performed.

  In the above embodiment, from the data logger 83, the relationship between the torque T and the loading time t, the relationship between the vertical load Fv and the loading time t, the relationship between the rotation angle Δθ and the loading time t, the torque T and the rotation angle. Although the relationship between Δθ and the relationship between the vertical load Fv and the rotation angle Δθ is output as data, each data is input to a personal computer (not shown) in which a predetermined calculation program has been input in advance, and shear elasticity The coefficient G, the shear elastic resistance, and the cumulative rotational speed N may be calculated, and at least one of the torsional rigidity, durability, and flow resistance of the specimen 4 may be automatically evaluated based on these calculated values. .

It is a schematic diagram which shows the whole structure of the test apparatus for evaluating the asphalt mixture which concerns on one Embodiment of this invention. A shows to view the structure of the specimen, (a) represents a front view, (b) is an A-A sectional view in (a). It is a table | surface which shows the example of a composition of the asphalt mixture (in the case of drainage asphalt) which comprises a test body. It is a graph which shows the example of a composition of the asphalt mixture (in the case of dense particle size asphalt) which comprises a test body. It is explanatory drawing which shows the relationship between the force and displacement which act on a cylindrical-shaped test body. It is explanatory drawing which shows the relationship between the stress and distortion which act on the microelement of a cylindrical-shaped test piece. It is explanatory drawing which shows distribution on the cylindrical coordinate of a shear stress. It is a flowchart which shows the procedure which performs the various tests of an asphalt mixture using a test apparatus, Comprising: (a) is a main flowchart, (b) is a subflowchart of step S1 in (a). It is a flowchart which shows the procedure which performs the various tests of an asphalt mixture using a test apparatus, Comprising: (a) is a sub flowchart of step S3 in Fig.8 (a), (b) is a subflowchart of step S4 in FIG.8 (b). It is a flowchart. It is a graph which shows the actual value in the case of performing a monotonous torsion test (in the case of drainage asphalt mixture, specimen temperature 20 ° C., water immersion). It is a graph which shows the measured value when a monotonous torsion test is done (in the case of drainage asphalt mixture, specimen temperature 60 ° C., water immersion). It is a graph which shows the measured value when a monotonous torsion test is done (in the case of a dense particle size asphalt mixture, a specimen temperature of 20 ° C., and water immersion). It is a graph which shows estimation when the repeated torsion test is done (repeated loading of a minute torque). It is a graph which shows estimation when the repeated torsion test is done (repeated loading of medium torque).

Explanation of symbols

1 Test device (corresponds to evaluation device)
2 Base 3 Loading platform 4 Specimen 41 Asphalt mixture 42 Upper cap 43 Lower caps 44 and 45 Adhesive 5 Vertical load loading unit (corresponding to load loading unit)
54 Pneumatic cylinder 57 Load meter 59 Upper loading plate 6 Torque loading unit 62 Hydraulic cylinder 63 Load meter 64 Torsion arm 65 Torsion displacement meter 68 Lower loading plate 7 Constant temperature bath 71 Water tank 72 Water pan 73 Electric heater 77 Thermometer 8 Control unit 81 Function Generator 82 Servo amplifier 83 Data logger T Torque Fv Vertical load Δθ Rotation angle

Claims (12)

Based asphalt mixture on the relationship between the loading times and accumulated rotation angle for each torque when was repeatedly loading while increasing the torque of the order added twist around the axis of the specimen was formed into a cylindrical shape stepwise An evaluation method of an asphalt mixture characterized by evaluating the flow resistance of the specimen . 2. The method for evaluating an asphalt mixture according to claim 1, wherein the flow resistance is evaluated by a torque when the cumulative rotation angle suddenly increases in relation to the cumulative rotation angle and the number of times of loading.   Evaluating at least one of the torsional rigidity and durability of the specimen based on the relationship between the torque and the rotation angle when the torque for applying the torsion to the specimen is monotonously increased. The method for evaluating an asphalt mixture according to claim 1 or 2, characterized in that:   4. The asphalt mixture evaluation method according to claim 3, wherein the torsional rigidity is evaluated by a shear elastic modulus calculated using a value near an initial value in the relationship between the torque and the rotation angle.   4. The method for evaluating an asphalt mixture according to claim 3, wherein the durability is evaluated by a peak value of the torque in a relationship between the torque and a rotation angle.   The torsional rigidity of the specimen is evaluated based on the relationship between the torque and the rotation angle when the specimen is repeatedly loaded while gradually increasing the torque for applying the torsion to the specimen. Item 3. The method for evaluating an asphalt mixture according to item 1 or 2.   The evaluation of the asphalt mixture according to claim 6, wherein the torsional rigidity is evaluated by a shear elastic modulus calculated using a value near a final value for each torque in the relationship between each torque and a rotation angle. Method. The method for evaluating an asphalt mixture according to claim 4 or 7, wherein the shear elastic modulus is expressed by the following equation.

Here, G is the shear modulus, H is the specimen height, R is the specimen radius, T is the torque, and Δθ is the rotation angle. The asphalt mixture according to any one of claims 1 to 8, wherein the evaluation is performed in a state where the specimen is immersed in a thermostatic bath set at a temperature higher than 0 ° C and lower than 100 ° C. Evaluation method. A loading platform erected on the base, a specimen configured to be detachably set on the loading platform after the asphalt mixture is formed into a cylindrical shape, and an axis of the specimen set on the loading platform described above A torque loading unit for loading a torque for applying a twist around the core, and a control unit for controlling the operation of the loading unit so as to repeatedly load while increasing the torque stepwise. Evaluation equipment for asphalt mixture. A load loading unit that loads a load in a direction perpendicular to the end surface of the specimen set on the loading platform described above is further provided, and the control unit loads the load when repeatedly loading the torque stepwise. The apparatus for evaluating an asphalt mixture according to claim 10, wherein the operation of the load loading unit is also controlled. The apparatus for evaluating an asphalt mixture according to claim 10 or 11, further comprising a thermostatic bath in which the specimen can be immersed.

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