Evaluation method of finishing materials and construction method of finishing materials

Abstract

To provide an evaluation method for a paving material that takes into account deformation caused by an external factor and environmental temperature, and a construction method for a paving material.SOLUTION: An evaluation method for a paving material comprises a deformation rate acquisition step in which a plate-shaped test piece P that imitates the paving material is held at test temperature, and while the outer edge of the test piece P is fixed, a protruding part A is formed by pressing a pressing member 3 against one plate surface of the test piece P and making the other plate surface protrude, and a deformation rate is acquired, which is the ratio of the height of the protruding part A to the pressing amount of the pressing member 3, and an evaluation step for acquiring deformation properties on the surface of the paving material on the basis of this deformation rate.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for evaluating paving materials and a method for constructing paving materials.

Background Art

[0002] Paving materials such as asphalt for paving roads are formed by laying a roadbed material on a roadbed, and further laying an asphalt mixture thereon and compacting it. Paving materials are damaged, worn, and deformed by external factors such as the load of passing vehicles and the friction received from tires, and are also deformed by external factors such as the expansion and subsidence of the roadbed material. In addition, the occurrence and degree of damage, wear, or deformation vary depending on the environment such as the temperature of the road surface. Therefore, it is important to evaluate the deformation characteristics of paving materials considering external factors and to construct (lay) paving materials taking into account their deformation characteristics.

[0003] Patent Document 1 discloses a method for evaluating an asphalt mixture, an evaluation apparatus, and a specimen. The test apparatus is for evaluating the rigidity, durability, and fluidity of an asphalt mixture by torsional shear. The test apparatus is configured to evaluate at least one of the shear elastic modulus, flow resistance, and durability of a specimen based on the response of the specimen when torsion is applied around the axis of a specimen formed by molding an asphalt mixture into a cylindrical shape. Patent Document 1 describes that in a real asphalt-paved road, the temperature in summer may exceed 60°C and torsional shear may occur.

[0004] Patent Document 2 discloses a method for suppressing the expansion of steelmaking slag, etc. Patent Document 2 describes that steelmaking slag is used for roadbed materials and geotechnical materials. In addition, Patent Document 2 describes that steelmaking slag may contain unreacted lime, unreacted magnesium oxide, etc., which have the property of reacting with water to cause volume expansion, and that due to this property, for example, when steelmaking slag is applied to a roadbed material, the asphalt laid on the roadbed material may bulge or cracks may occur.

Prior Art Documents

Patent Document

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] As described in Patent Document 1, there is a need to evaluate the durability and rigidity of paving materials such as asphalt-based paving materials in consideration of, for example, the use environment and environmental temperature. However, in the conventional evaluation method, regarding the deformation characteristics of paving materials such as asphalt-based paving materials, for example, it may not be possible to appropriately evaluate the deformation caused by external factors such as the expansion of the roadbed material in the asphalt-based paving material laid on the roadbed material laid on the road surface and the environmental temperature. Also, for this reason, there may be cases where the construction of paving materials considering the deformation caused by external factors and the environmental temperature cannot be carried out.

[0007] The present invention has been made in view of such a situation, and its object is to provide a method for evaluating paving materials and a method for constructing paving materials that take into account the deformation caused by external factors and the environmental temperature.

Means for Solving the Problems

[0008] The method for evaluating paving materials according to the present invention for achieving the above object is as follows.

[0009] [1] The method for evaluating paving materials is holding a plate-shaped test piece simulating the paving material at the test temperature, pressing a pressing member against one plate surface of the test piece with the outer edge of the test piece fixed to project the other plate surface to form a convex portion, and obtaining a deformation rate which is the ratio of the height of the convex portion to the pressing amount of the pressing member; a deformation rate obtaining step An evaluation step of obtaining the deformation characteristics of the surface of the paving material based on the deformation rate is included.

[0010] The evaluation method of the paving material according to the present invention may further be as follows.

[0011] [2] In the evaluation step, the evaluation method of the paving material according to [1] above, wherein the deformation characteristics are obtained based on the deformation rate obtained at two or more of the test temperatures and the test temperature.

[0012] [3] In the evaluation step, the evaluation method of the paving material according to [1] above, wherein the temperature dependence of the deformation rate is obtained based on the deformation rate obtained at two or more of the test temperatures and the test temperature.

[0013] [4] The paving material is an asphalt-based paving material laid on a roadbed material laid on a road surface, The evaluation method of the paving material according to any one of [1] to [3] above, including a prediction step of predicting the displacement amount of the surface of the asphalt-based paving material after the asphalt-based paving material is laid on the roadbed material based on the deformation rate and the predicted expansion amount of the roadbed material.

[0014] Using the evaluation method of the paving material in [4] above, furthermore, the following construction method of the paving material can be realized.

[0015] [5] A construction method of the paving material for adjusting the thickness of the asphalt-based paving material so that the predicted displacement amount is within a predetermined threshold value.

[0016] [6] A construction method of the paving material for adjusting the composition of the asphalt-based paving material so that the predicted displacement amount is within a predetermined threshold value.

[0017] [7] A construction method of the paving material for adjusting the composition of the roadbed material to adjust the predicted expansion amount so that the predicted displacement amount is within a predetermined threshold value.

[0018] [8] A method for constructing a paving material, comprising laying the asphalt-based paving material so that the predicted displacement amount is within a predetermined threshold value. When predicting the displacement amount, obtaining the maximum temperature of the road surface on which the asphalt-based paving material is to be laid. Adjusting at least one of the thickness of the asphalt-based paving material and the composition of the asphalt-based paving material so that the predicted displacement amount based on the deformation rate obtained at the test temperature corresponding to the maximum temperature is within a predetermined threshold value. A method for constructing a paving material.

[0019] [9] A method for constructing a paving material, comprising laying the asphalt-based paving material so that the predicted displacement amount is within a predetermined threshold value. When predicting the displacement amount, obtaining the maximum temperature of the road surface on which the asphalt-based paving material is to be laid. Adjusting the composition of the roadbed material to adjust the predicted expansion amount so that the predicted displacement amount based on the deformation rate obtained at the test temperature corresponding to the maximum temperature is within a predetermined threshold value. A method for constructing a paving material.

[14] [Advantages of the Invention]

[0020] According to the present invention, it is possible to provide a method for evaluating a paving material and a method for constructing a paving material that take into account deformation caused by external factors and environmental temperature.

[21] [Brief Description of the Drawings]

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

[39] [Embodiments for Carrying Out the Invention]

[0022] With reference to the drawings, an evaluation method for a paving material and a construction method for a paving material according to an embodiment of the present invention will be described.

[0023] First, an overview of the evaluation method for the paving material according to the present embodiment will be described.

[0024] FIG. 1 shows an example of a conceptual diagram of a test apparatus 100 used in the evaluation method for the paving material according to the present embodiment. The test apparatus 100 includes a housing container 1 that forms a housing space S for holding a plate-shaped test piece P simulating the paving material at a test temperature, a frame body 2 that fixes the outer edge of the test piece P, and a pressing member 3 that is pressed against one plate surface of the test piece P. The pressing member 3 is pressed perpendicular to the plate surface of the test piece P. In the present embodiment, the "plate-shaped test piece simulating the paving material" refers to a test piece having a thickness and composition corresponding to the paving material actually laid.

[0025] In the example shown in FIG. 1, the pressing member 3 is formed in a columnar shape and is arranged such that its axis is along the vertical direction. The frame body 2 holds the test piece P such that the plate surface of the test piece P is along the horizontal plane. Although the frame body 2 fixes the outer edge of the test piece P, both surfaces of the central portion of the test piece P are exposed in a vertical view (not hidden by the frame body 2). In the present embodiment, the frame body 2 has a circular opening 20 and exposes both surfaces of the central portion of the test piece P.

[0026] As shown in FIG. 1, the evaluation method for the paving material according to the present embodiment includes a deformation rate acquisition step of holding a plate-shaped test piece P simulating the paving material at a test temperature, fixing the outer edge of the test piece P, pressing the pressing member 3 against one plate surface (the lower surface in FIG. 1) of the test piece P to project the other plate surface (the upper surface in FIG. 1) to form a convex portion A (see FIG. 2), and acquiring a deformation rate that is the ratio of the height Y (see FIG. 2) of the convex portion A to the pressing amount X (see FIG. 2) of the pressing member 3, and an evaluation step of acquiring the deformation characteristics of the surface of the paving material based on this deformation rate.

[0027] According to the method for evaluating a paving material according to this embodiment, it is possible to provide a method for evaluating a paving material that takes into account deformation caused by external factors and environmental temperature, and a construction method for laying a paving material while taking into account deformation caused by external factors and environmental temperature.

[0028] Hereinafter, the method for evaluating a paving material according to this embodiment will be described in detail.

[0029] The paving material according to this embodiment is used for paving the road surface such as a road. The paving material according to this embodiment includes a roadbed material laid on the roadbed and an asphalt-based paving material such as an asphalt mixture laid on the roadbed material. In the following description, mainly, the case where the paving material is an asphalt-based paving material will be exemplified and described.

[0030] The method for evaluating a paving material according to this embodiment is to obtain the deformation characteristics of the surface of the paving material for a road. Taking a specific example, for a paving material such as an asphalt-based paving material laid on a roadbed material laid on a road surface, considering the deformation factors of the paving material caused by external factors such as the expansion of the roadbed material and the environmental temperature such as the temperature of the road surface, so-called deformation characteristics such as the ease of deformation and the degree of deformation of the surface of the paving material are obtained and evaluated. An example of the deformation characteristics of the surface of the paving material is the deformation rate itself. Another example of the deformation characteristics is the relationship between the environmental temperature and the deformation rate.

[0031] The method for evaluating a paving material according to this embodiment contributes to the realization of a construction method for laying a paving material while taking into account the deformation characteristics of the surface of the paving material by obtaining the deformation characteristics of the surface of the paving material. Specifically, when a paving material is constructed (laid) on a road, it is possible to realize the construction (laying) of the paving material with a thickness and composition that are less likely to deform after laying (after paving). Also, when a paving material is laid on a road, it is possible to realize construction (laying) in which the predicted expansion amount of the roadbed material (the expansion amount of the roadbed material predicted after laying the paving material) is adjusted according to the thickness (layer thickness) and composition of the paving material so that deformation is less likely to occur after laying. Note that the expansion amount of the roadbed material can be adjusted by adjusting the composition of the roadbed material (for example, the amounts of unslaked lime and crystallized CaO).

[0032] As described above, the method for evaluating the paving material according to this embodiment is performed by holding a plate-shaped test piece P simulating the paving material at the test temperature and fixing the outer edge of the test piece P, as shown in FIG. 1. Then, as shown in FIG. 2, the pressing member 3 is pressed against the test piece P to form the convex portion A. In this embodiment, the test piece P is in a flat plate shape.

[0033] The deformation rate α of the paving material is obtained as the ratio of the height Y of the convex portion A to the pressing amount X of the pressing member, as shown in the following formula (1).

[0034] Deformation rate α = Y(mm) / X(mm) ··· (1)

[0035] As shown in FIG. 2, the pressing amount X is the shortest distance between the position on the plate surface of the test piece P on the side facing the pressing member 3 before pressing the pressing member 3, that is, before deformation, and the pressing surface 30 of the pressing member 3 after pressing the pressing member 3 against the test piece P. Note that the position (position in the direction perpendicular to the plate surface) on the plate surface of the test piece P on the side facing the pressing member 3 before deformation is the same as the position (position in the direction perpendicular to the plate surface) of the plate surface that has not deformed even after pressing the pressing member 3 against the test piece P on the plate surface facing the pressing member 3.

[0036] The pressing surface 30 of the pressing member 3 is the surface of the pressing member 3 facing the test piece P (the surface pressed by the test piece P). When explained from the viewpoint of the displacement of the pressing member 3, the pressing amount X of the pressing member 3 is the same as the displacement amount of the pressing surface 30 from the position of the pressing surface 30 in the state where the pressing surface 30 is gently brought into contact with the test piece P to the pressing surface 30 after pressing the pressing member 3 against the test piece P.

[0037] As shown in Fig. 2, the height Y of the convex portion A is the shortest distance between the position on the opposite side of the plate surface of the test piece P before the pressing member 3 is pressed, that is, the position on the plate surface opposite to the side facing the pressing member 3 before deformation, and the top of the convex portion A formed after the pressing member 3 is pressed against the test piece P. Note that the position (the position in the direction perpendicular to the plate surface) on the plate surface opposite to the side facing the pressing member 3 in the test piece P before deformation is the same as the position (the position in the direction perpendicular to the plate surface) of the plate surface that has not deformed even after the pressing member 3 is pressed against the test piece P on the plate surface opposite to the side facing the pressing member 3.

[0038] Hereinafter, the operation of pressing a pressing member against a test piece to form a convex portion may sometimes be simply referred to as a penetration test.

[0039] The penetration test can be carried out by diverting, for example, the hydraulic system and the penetration piston used in the CBR test machine of the CBR test method specified in JIS A1211, the Amslter test machine (compression test), etc. The procedure of the penetration test can be carried out in the same manner as the CBR test method by replacing the mold of the CBR test method specified in JIS A1211 with a test piece of the paving material and replacing the penetration piston with a pressing member.

[0040] The moving speed of the pressing member when pressing the pressing member against the test piece (hereinafter, may sometimes be referred to as the penetration speed) is preferably about 1 mm / min, but the method is not limited as long as the pressing amount and the height of the convex portion can be measured.

[0041] The pressing amount when measuring the deformation rate is preferably about 5 mm, but it is not limited as long as the pressing member does not penetrate through the test piece.

[0042] As an example, the pressing member is cylindrical, but the shape is not particularly limited. Hereinafter, the case where the pressing member is cylindrical will be exemplified and described.

[0043] The size of the test piece, the thickness or diameter of the pressing member may be appropriately set in consideration of the evaluation purpose of the paving material. That is, the size of the test piece, the thickness or diameter of the pressing member may be appropriately set according to the type of assumed external factors, the amount of displacement or the magnitude of stress.

[0044] For example, when the paving material is an asphalt paving material laid on a roadbed material, it is likely to be affected by the expansion of the aggregate (slag) contained in the roadbed material. Therefore, when performing the penetration test, in order to evaluate the influence of this aggregate (slag), it is preferable that the diameter of the pressing member 3 shown in FIG. 1 corresponds to the maximum particle size of the aggregate of the roadbed material. In addition, if the pressing member 3 is too thin, convex portions may not be formed when the pressing member 3 is pressed against the test piece P. Therefore, the diameter of the pressing member 3 is preferably 10 mm or more, and it is preferably made changeable according to the evaluation purpose. Further, the inner diameter (diameter) of the opening 20 of the frame body 2 that holds the test piece P is preferably at least four times the length of the maximum particle size of the aggregate contained in the roadbed material. The inner diameter of the opening 20 may be, for example, four times the diameter of the pressing member 3.

[0045] The size of the test piece P depends on the diameter of the pressing member 3, but it is preferably a square having a side length of at least five times the length of the maximum particle size of the aggregate contained in the roadbed material. The length of one side in the case where the test piece P is a square may be, for example, five times or more the diameter of the pressing member 3.

[0046] The thickness of the test piece P is preferably set to the thickness (up to 100 mm maximum) assuming the paving material to be actually laid.

[0047] The test temperature of the test piece P may be adjusted by housing it in a thermostat with adjusted temperature or immersing it in water in a water tank. In the example shown in FIG. 1, the housing container 1 may be a thermostat or a water tank. Hereinafter, the case where the housing container is a thermostat will be exemplified and described below.

[0048] The physical properties of asphalt are greatly affected by temperature. Therefore, when the paving material is an asphalt-based paving material, it is preferable to keep the test piece within 3°C above and below the test temperature (not less than the test temperature - 3°C and not more than the test temperature + 3°C) when measuring the pressing amount and the height of the convex portion A.

[0049] In this embodiment, the deformation characteristics (for example, ease of deformation, deformability) of the surface of the paving material are obtained based on the above deformation rate.

[0050] The deformation characteristics may be obtained based on the deformation rates obtained at two or more test temperatures and the respective test temperatures at which the deformation rates were obtained. In this case, based on the deformation rates obtained at two or more test temperatures and the respective test temperatures at which the deformation rates were obtained, the temperature dependence of the deformation rate may be determined as the deformation characteristics.

[0051] The temperature dependence of the deformation rate can be obtained, for example, as a function α(T) of the temperature T of the test piece as shown in the following formula (2).

[0052] α(T)=aT + C (where a and C are constants) ···(2)

[0053] The function α(T) may be determined, for example, as follows. First, a penetration test is performed at a plurality of (two or more) test temperatures T, and the deformation rate α at each test temperature is obtained. Then, the relationship between each test temperature T and the deformation rate α at these temperatures is determined as a linear approximation function by, for example, the least squares method, and the approximation function is adopted as the function α(T).

[0054] FIG. 3 shows an example of a graph showing the relationship between the deformation rate α and the test temperature T at a certain pressing amount. In the graph shown in FIG. 3, the horizontal axis represents the test temperature T, and the vertical axis represents the deformation rate α, and it exemplifies a graph in which the deformation rate α for each test temperature T is plotted. In FIG. 3, the plots of white circles are the deformation rates α for each test temperature T. In FIG. 3, a graph (a linearly approximated graph) obtained by approximating these plots with a linear function by the least squares method is shown by a broken line. Details of the relationship shown in the graph of FIG. 3 will be described later (see Examples).

[0055] As described above, the physical properties of asphalt are greatly affected by temperature. For example, when the paving material is an asphalt-based paving material, the ease of deformation and the way of deformation change depending on the temperature. Generally, the higher the temperature of the asphalt-based paving material, the lower its strength and the more vulnerable it becomes, and it becomes more likely to deform under the influence of external factors. Therefore, it is preferable to prepare a plurality of test pieces, hold these plurality of test pieces at a plurality of different test temperatures, such as a temperature range from 0°C to 80°C, and perform a penetration test for each test temperature to calculate the deformation rate α. In the example shown in FIG. 3, since the pressing amount is constant, the higher the test temperature T, the smaller the deformation rate α.

[0056] When obtaining the deformation rate or the temperature dependence of the deformation rate, it is advisable to consider the maximum temperature assumed on the road surface at the planned laying location of the paving material as the test temperature. Specifically, it is preferable to adopt this maximum temperature as one of the test temperatures. Also, it is preferable to adopt at least one temperature above and below this maximum temperature as the test temperature. For example, it is preferable to adopt a temperature within -5°C of the maximum temperature and a temperature within +5°C of the maximum temperature as the test temperatures. More preferably, at least three temperatures including this maximum temperature and the temperatures above and below the maximum temperature should be adopted as the test temperatures. Of course, if the maximum temperature of the road surface at the planned laying location of the paving material has been specified in advance, only this maximum temperature point can be adopted as the test temperature, and the deformation rate corresponding only to this maximum temperature can be obtained. In this way, by setting the test temperature considering the maximum temperature assumed on the road surface at the planned laying location of the paving material, it is possible to obtain the deformation characteristics at the maximum temperature and evaluate the influence of external factors on the surface of the paving material at the maximum temperature, particularly the maximum amount of deformation that may occur.

[0057] When obtaining the deformation rate or the temperature dependence of the deformation rate using a test piece simulating the paving material, based on these, it is possible to predict the displacement amount of the surface of the paving material after laying due to external factors (for example, the expansion of members under the paving material such as the roadbed material) (an example of the prediction process). By predicting the displacement amount of the surface of the paving material after laying, it is possible to lay the paving material so that the displacement amount of the surface of the paving material after laying is within a predetermined threshold value (for example, the reference value in the required quality of the road after paving or the reference value specified in laws and regulations, etc.). For example, it becomes possible to adjust the thickness of the paving material such as the asphalt paving material or the composition of the paving material so that the displacement amount of the surface of the paving material after laying becomes the predetermined threshold value. Also, it becomes possible to adjust the composition of the roadbed material to adjust the predicted expansion amount (the predicted amount of expansion) of the roadbed material.

[0058] Taking the case where the paving material is an asphalt paving material laid on the roadbed material as an example, the method for predicting the displacement amount of the surface of the asphalt paving material after laying when the roadbed material expands is as follows.

[0059] When the temperature of the asphalt pavement material is Ta, the predicted value y of the displacement amount of the surface of the pavement material can be obtained by multiplying the value obtained by substituting the temperature Ta into the function α(T) shown in Equation (2) by the local predicted expansion amount x of the member under the pavement material (for example, the roadbed material), as shown in the following Equation (3).

[0060] y = α(Ta) × x ··· (3)

[0061] Note that the method of the water immersion expansion test used for calculating the local predicted expansion amount of the member under the pavement material is not limited. For example, when the pavement material is an asphalt pavement material laid on a roadbed material, and the roadbed material (including the case of the lower roadbed) contains slag (steelmaking slag) as an aggregate, the local predicted expansion amount of the roadbed material can be predicted by conducting, for example, the water immersion expansion test of road steel slag specified in JIS A 5015 (performed for 100 days). Note that the temperature and number of days of the water immersion expansion test may be changed (adjusted) from the values specified in the above regulations as necessary. The water immersion expansion test may be conducted, for example, as a continuous accelerated water immersion expansion test at a water temperature of 80°C for 40 days.

Example

[0062] Examples will be described below.

[0063] In Example 1, it is assumed that the pavement material is an asphalt pavement material and is laid on a roadbed material containing slag as an aggregate with a layer thickness (thickness) of 50 mm, and the deformation characteristics of the surface of the pavement material are obtained. In the following description, the composition (mix) of the asphalt pavement material in Example 1 is described as Composition A. Also, assuming that the maximum temperature (ambient temperature) of the road surface at the planned laying location of the pavement material is 70°C, the displacement amount of the surface of the pavement material is predicted. In Example 1, when the displacement amount of the surface of the pavement material after laying is 1.2 mm or less (an example of a predetermined threshold value), it is regarded as qualified in the shipment standard (quality standard as an asphalt pavement material), and when it exceeds 1.2 mm, it is determined as unqualified (defective).

[0064] In this embodiment, the maximum particle size (maximum diameter) of the aggregate contained in the asphalt pavement material is 19 mm.

[0065] In this embodiment, the layer thickness of the roadbed material was assumed to be 200 mm. Also, as the roadbed material, a material with a predicted maximum local expansion rate (an example of the predicted expansion amount) of 0.92% was used. The external factor that deforms the asphalt pavement material as the pavement material assumed in this embodiment is the expansion of the roadbed material.

[0066] In this embodiment, the local maximum expansion amount was estimated from the results of the water immersion expansion test specified in JIS A 5015 as described above. Specifically, for the roadbed material of each lot or grade (hereinafter simply referred to as lot), the water immersion expansion test was carried out a plurality of times, and the expansion amount obtained by each test was converted into an expansion rate. Then, the average expansion rate Vave of the lot and the standard deviation σ of the lot were obtained, and the local maximum expansion rate Vmax was obtained by applying them to the empirical formula (estimated from the actual results) shown in the following formula (4).

[0067] Vmax = Vave + 5σ ··· (4)

[0068] In this embodiment, as described above, the layer thickness of the roadbed material is assumed to be 200 mm. Therefore, the local maximum expansion amount predicted in the roadbed material is predicted to be 1.84 mm by multiplying the layer thickness of the roadbed material of 200 mm by the above maximum expansion rate of 0.92%.

[0069] Considering that the maximum particle size of the aggregate contained in the asphalt pavement material is 19 mm, the test piece for evaluation was made into a square with one side being 300 mm (a length exceeding 5 times the maximum particle size of the aggregate, which is 19 mm). Also, the thickness of the test piece was set to 50 mm corresponding to the laying conditions of the assumed pavement material (assuming laying at a thickness of 50 mm).

[0070] For the penetration test, a test apparatus with the configuration shown in Fig. 1 was used. First, the test piece was held on the frame in the accommodation container which is a thermostatic bath. Note that the temperature of the test piece before being held on the frame and the temperature inside the accommodation container (test temperature in this embodiment) were pre-adjusted to 20°C. Then, the upper surface of the cylindrical pressing member was brought into contact with the lower surface of the held test piece. Further, the pressing member was pushed upward along the vertical direction to press the pressing member against the test piece. Note that the diameter of the pressing member was 40 mm. Also, the penetration speed was set to 1 mm / min and the pressing amount was set to 4 mm. Then, the height of the convex portion formed on the upper surface of the test piece was measured. The height of the convex portion was measured with a laser displacement meter. And based on the pressing amount (4 mm) and the measured height of the convex portion, the deformation rate at a test temperature of 20°C was obtained.

[0071] In the same manner as above, while changing the temperature of the test piece before being held on the frame and the temperature inside the accommodation container from 30°C to 80°C in increments of 10°C, the penetration test was carried out at each test temperature, and the deformation rate at each test temperature was obtained.

[0072] The graph of Fig. 3 above plots the deformation rates at the test temperatures from 20°C to 80°C in this embodiment.

[0073] From the relationship between the deformation rate (α) and the test temperature (T) shown in Fig. 3, furthermore, as the temperature dependence of the deformation rate, the function α(T) was obtained. The function α(T) was obtained by approximating the relationship between the deformation rate (α) and the test temperature (T) with a linear function by the least squares method. In this embodiment, for the function α(T), the constant a was -0.0079 and the constant C was 1.0221. The function α(T) in this embodiment is shown in the following formula (5).

[0074] α(T)=-0.0079T + 1.0221 ···(5)

[0075] In this embodiment, since the maximum temperature of the road surface at the planned laying location of the paving material is assumed to be 70°C, from the above formula (5), the deformation rate at the maximum temperature of the road surface is predicted to be 0.4691.

[0076] When the predicted deformation rate of the paving material as described above is multiplied by the local maximum expansion amount (1.84 mm) of the roadbed material as the predicted expansion amount, a predicted value (about 0.86 mm) of the displacement amount on the surface of the paving material can be obtained (see Equation 3). This predicted value (about 0.86 mm) is determined to be qualified in light of the above shipment standard (the displacement amount on the surface of the paving material is 1.2 mm or less).

[0077] The results described above for Example 1 are shown in Table 1.

[0078]

Table 1

[0079] In Examples 2 to 5 and Comparative Examples 1 and 2, the composition or layer thickness of the asphalt paving material was changed, and the change rate and the predicted value of the displacement amount on the surface of the paving material were obtained in the same manner as in Example 1. These results are shown in Table 1 together.

[0080] The composition of the asphalt paving material in Examples 2 and 3 was set as Composition A in the same manner as in Example 1. The composition of the asphalt paving material in Examples 4 and 5 and Comparative Example 1 was set as Composition B. The composition of the asphalt paving material in Comparative Example 2 was set as Composition C. Here, there are differences in the particle size distribution (coarse particle content rate) of the aggregate among Compositions A to C. The particle size (coarse particle content rate) of the aggregate is in the order of Composition C, Composition B, and Composition A from small to large.

[0081] In Examples 4 and Comparative Example 2, the layer thickness of the asphalt paving material was set to 50 mm in the same manner as in Example 1. In Examples 2 and 5, unlike Example 1, the layer thickness of the asphalt paving material was set to 40 mm. In Examples 3 and Comparative Example 1, unlike Example 1, the layer thickness of the asphalt paving material was set to 30 mm.

[0082] For Examples 2 to 5 and Comparative Examples 1 and 2, the maximum temperature of the road surface at the planned paving location of the paving material was assumed to be 70°C in the same manner as in Example 1. Also, the roadbed material is the same as in the case of Example 1.

[0083] For Examples 2 to 5 and Comparative Examples 1 and 2, the criteria for passing or failing (being defective) are the same as those in Example 1. These judgment results are also shown in Table 1 together.

[0084] Examples 1 to 5 are judged to be qualified because the predicted displacement amount on the surface of the paving material is less than 1.2 mm.

[0085] As shown in Table 1, in Comparative Examples 1 and 2, since the predicted displacement amount on the surface of the paving material exceeds 1.2 mm, they are judged to be unqualified. From the results of Comparative Examples 1 and 2, it can be seen that the paving materials used in Comparative Examples 1 and 2 need to be improved so that their composition is changed (for example, the content rate of coarse grains of the aggregate is reduced) to make displacement less likely to occur, or the laying conditions of the assumed paving material are changed to perform condition changes such as laying with a thicker layer thickness. Also, it can be seen that it is necessary to adjust the composition of the roadbed material (for example, adjust to reduce the amount of unslaked lime, crystallized CaO, etc.) so that the expansion amount of the roadbed material becomes smaller corresponding to the thickness (layer thickness) and composition of the paving material assumed in Comparative Examples 1 and 2. The change of the laying conditions of the assumed paving material and the adjustment of the composition of the roadbed material may be carried out simultaneously.

[0086] In this way, if the deformation characteristics on the surface of the paving material are obtained, it is possible to realize a construction method of the paving material for laying the paving material in consideration of the deformation characteristics on the surface of the paving material. Specifically, when laying the paving material on a road, the paving material can be laid after being adjusted in advance to a thickness and composition in which deformation is less likely to occur after paving. Also, it becomes possible to adjust the composition of the roadbed material.

[0087] In the above manner, it is possible to provide an evaluation method and a construction method of the paving material according to this embodiment.

[0088] 〔Alternative Embodiment〕 (1) In the above embodiment, as an example of the evaluation method of the paving material according to the present embodiment, in FIG. 1, the case where the pressing member 3 is pressed against the lower surface of the test piece P with the outer edge of the test piece P fixed so that the plate surface is along the horizontal plane was illustrated and described. However, in the evaluation method of the paving material according to the present embodiment, it is not limited to the case where the pressing member 3 is pressed against the lower surface of the test piece P.

[0089] In the evaluation method of the paving material according to the present embodiment, as shown in FIG. 4, the pressing member 3 may be pressed against the upper surface of the test piece P. However, in this case, the test piece P may be deformed so as to be convex downward due to its own weight. Therefore, it is preferable to start the measurement promptly after fixing the test piece P to the frame body 2 and also to finish the measurement. For example, it is preferable to start the penetration test within 1 minute. In particular, when the penetration test is carried out by diverting a CBR tester, it is difficult to adjust the temperature of the test piece using a constant temperature bath or a water bath. Therefore, it is necessary to start the penetration test as soon as possible (for example, within 1 minute) after setting.

[0090] Also, in the evaluation method of the paving material according to the present embodiment, the pressing member 3 may be pressed against the plate surface of the test piece P with the outer edge of the test piece P fixed so that the plate surface intersects the horizontal plane.

[0091] (2) In the above embodiment, the case where the paving material to be evaluated is an asphalt-based paving material was illustrated and described, but the paving material to be evaluated is not limited to an asphalt-based paving material. For example, the paving material to be evaluated may be a roadbed material (a roadbed material laid under an asphalt-based paving material) laid on the roadbed.

[0092] In addition, when the paving material is a roadbed material, since the change in physical properties due to temperature is small (the influence due to temperature is small), it is often sufficient to select only the room temperature as the test temperature in the case of evaluating as a paving material.

[0093] Note that the configurations disclosed in the above embodiments (including other embodiments, the same applies hereinafter) can be applied in combination with the configurations disclosed in other embodiments as long as there is no contradiction. Also, the embodiments disclosed in this specification are examples, and the embodiments of the present invention are not limited thereto, and can be appropriately modified within the scope not departing from the object of the present invention.

Industrial Applicability

[0094] The present invention can be applied to a method for evaluating paving materials and a method for constructing paving materials.

Explanation of Reference Numerals

[0095] 1: Storage container 100: Testing device 2: Frame 20: Opening 3: Pressing member 30: Pressing surface A: Protrusion P: Test piece S: Storage space X: Pressing amount Y: Height

Claims

1. A plate-shaped test piece imitating a paving material is maintained at a test temperature, and while fixing the outer edge of the test piece, a pressing member is pressed against one plate surface of the test piece to protrude the other plate surface to form a convex portion, and a deformation rate acquisition step of acquiring a deformation rate which is a ratio of the height of the convex portion to the pressing amount of the pressing member; an evaluation step of acquiring the deformation characteristics of the surface of the paving material based on the deformation rate; A method for evaluating a paving material, wherein the deformation characteristics acquired in the evaluation step are a deformation rate or a temperature dependency of the deformation rate.

2. The method for evaluating a paving material according to claim 1, wherein in the evaluation step, the deformation characteristics are acquired based on the deformation rate acquired at two or more of the test temperatures and the test temperature.

3. The method for evaluating a paving material according to claim 1, wherein in the evaluation step, the temperature dependency of the deformation rate is obtained based on the deformation rate acquired at two or more of the test temperatures and the test temperature.

4. The paving material is an asphalt-based paving material laid on a roadbed material laid on a road surface, The method for evaluating a paving material according to any one of claims 1 to 3, including a prediction step of predicting the displacement amount of the surface of the asphalt-based paving material after the asphalt-based paving material is laid on the roadbed material based on the deformation rate and the predicted expansion amount of the roadbed material.

5. A construction method of a paving material, wherein the thickness of the asphalt-based paving material is adjusted so that the displacement amount predicted by using the method for evaluating a paving material according to claim 4 is within a predetermined threshold value.

6. A construction method of a paving material, wherein the composition of the asphalt-based paving material is adjusted so that the displacement amount predicted by using the method for evaluating a paving material according to claim 4 is within a predetermined threshold value.

7. A construction method of a paving material, wherein the composition of the roadbed material is adjusted to adjust the predicted expansion amount so that the displacement amount predicted by using the method for evaluating a paving material according to claim 4 is within a predetermined threshold value.

8. A construction method of a paving material, wherein the asphalt-based paving material is laid so that the displacement amount predicted by using the method for evaluating a paving material according to claim 4 is within a predetermined threshold value, In predicting the displacement amount, the maximum temperature of the road surface on which the asphalt-based paving material is to be laid is acquired, A method for constructing a paving material, which adjusts at least one of the thickness of the asphalt paving material and the composition of the asphalt paving material so that the displacement amount predicted based on the deformation rate obtained at the test temperature corresponding to the maximum temperature is within a predetermined threshold value.

9. A method for constructing a paving material, which lays the asphalt paving material so that the displacement amount predicted using the method for evaluating the paving material according to claim 4 is within a predetermined threshold value, wherein, when predicting the displacement amount, the maximum temperature of the road surface on which the asphalt paving material is to be laid is obtained, A method for constructing a paving material, which adjusts the composition of the roadbed material to adjust the predicted expansion amount so that the displacement amount predicted based on the deformation rate obtained at the test temperature corresponding to the maximum temperature is within a predetermined threshold value.

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