JP2506755Y2 - Asphalt pavement with low μ road surface - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION << Industrial Application Field >> The present invention relates to an asphalt pavement having a low μ road surface (low road friction coefficient), which is useful as a test road.

《Prior art》 As a test road to evaluate the running stability of automobiles on slippery roads, a low μ road surface that is similar to the slippery road surface that is encountered in rainy weather on an asphalt pavement on public roads is always reproduced. A paved road that has been made is required.

As shown in FIG. 10, the required slip characteristics of the low μ road surface (B) have an intermediate property between the slip characteristics of the ordinary asphalt pavement road surface (A) and the slip characteristics of the snow and ice road surface (C). It is a thing. "Lock μ" shown in Fig. 10 is μ (friction coefficient) when the tire is locked.
And “peak μ” represents μ when the maximum value is reached.

That is, the above-mentioned road surfaces (A), (B) and (C) are distinguished by the following characteristics: Normal asphalt pavement road surface (A) ... The level of μ is high and the difference between the lock μ and the peak μ is large; The road level (C) ... μ is high, and there is almost no difference between the lock μ and the peak μ; the low μ road level (B) ... μ level is between (A) and (C), and is as low as (C). Although not present, the difference between lock μ and peak μ is small.

The slippery road surface of the conventional test road is mainly a reproduction of the snow and ice road surface, and the test road having such an extremely low level friction coefficient is relatively easy by finishing with materials such as tiles and concrete. Can be installed on.

On the other hand, it is not possible to easily make a low-μ road surface Alfalto pavement that exhibits specific slip characteristics. A low-μ road surface, which is not as thick as a snow-ice road surface but is considerably slippery than a normal asphalt pavement surface, is sometimes encountered while driving a car on a public road.Therefore, a running stability test for a car on a low-μ road surface is essential. Can not.

Means for producing a test road having such a low μ road surface are suggested in JP-A-63-11588 and JP-A-63-130801.

Also, although it is not intended for low μ, it is disclosed in JP-A-61-254.
Japanese Patent No. 706 also discloses a method of constructing a vehicle test course.

<Problems to be solved by the invention> Japanese Patent Laid-Open No. 63-11588 proposes that a carbon fiber / carbon composite plate-shaped molded body is impregnated with a wax-like substance having a high melting point of 60 ° C. or higher. It is said that the road surface made by laying this road surface material gives the test driver a visual discomfort different from the normal road surface and affects the sensory evaluation of vehicle running stability. There's a problem. In addition, it is expensive in terms of construction cost, and because it is not made of asphalt, there is a difference in terms of slip characteristics from that of ordinary asphalt pavement.

On the other hand, the one proposed in Japanese Patent Laid-Open No. 63-130801 is a vehicle running course made by spraying particulate matter such as sand on a base surface made of mortar, concrete, asphalt, etc. Although it is inexpensive, there is a problem that the slip characteristics are fundamentally different from the slippery road surface encountered on asphalt paved roads on public roads. In addition, a great deal of labor is required to maintain and replenish the particulate matter whose arrangement state changes due to braking.

Japanese Patent Laid-Open No. 61-254706 proposes a vehicle test course construction method in which an asphalt road surface paved from an asphalt mixture using a high hardness aggregate with a large grain size and a low hardness aggregate with a small grain size is used. Then, the low-hardness aggregate having a small particle diameter and the asphalt are removed by shot blasting to expose the high-hardness aggregate having a large particle diameter to obtain an uneven road surface. However, the uneven road surface is approximated to a coarse-grained road surface of asphalt in which road noise is likely to occur, and in that embodiment, as a slag is used as a high-hardness aggregate having a large particle diameter, it has a large particle diameter. Originally, high hardness aggregates have no roundness, and shot blasting is also a process for forming a rough road surface, not a process for obtaining a low μ road surface.

The present invention has been made to solve the above problems, and the problem to be solved is visually the same as an ordinary asphalt pavement, and is similar to a fairly slippery road surface sometimes encountered on an ordinary road. It is an object of the present invention to provide an asphalt pavement having a low μ road surface, which exhibits slip characteristics and is low in construction cost and maintenance cost.

<< Means for Solving the Problems >> The asphalt pavement with a low μ road surface of the present invention for solving the above problems has a rough aggregate of the asphalt mixture exposed on the asphalt surface, and the rough aggregate under the asphalt surface. Around the aggregate is a mixture of asphalt with fine aggregate, and around the coarse aggregate is a mixture of asphalt with fine aggregate, and the exposed portion of the coarse aggregate is rounded And

A low-μ road surface asphalt pavement in which the exposed portion of the coarse aggregate is further reduced in surface roughness by polishing is particularly preferable.

Aggregates such as gravel, crushed stone, and sand that are mixed with asphalt to make Alfalto mix for paving generally have a grain size of 2.
Although it is divided into coarse aggregate and fine aggregate with a boundary of 5 mm, the coarse aggregate as referred to in this specification should not be understood exactly as such, and is generally a relative proportion of classified aggregate. It can be understood as meaning a large class.

In order to expose the coarse aggregate on the asphalt surface, the asphalt coating including the fine aggregate may be removed by laying the asphalt mixture and then grinding the road surface with a metal brush, a water jet or the like. However, a large amount of removal leads to a decrease in the strength of the pavement surface, so it is necessary to determine the degree of removal of the asphalt coating in consideration of the road surface μ value and strength balance. Further, as a method of exposing the coarse aggregate, the coarse aggregate may be sprayed on the hot asphalt pavement surface which still has softness, and then the coarse aggregate may be embedded at an appropriate depth by a road roller.

The exposed portion of the coarse aggregate has a rounded shape, which means that the exposed portion of the coarse aggregate may have a curved concave-convex shape without sharp portions or corners. The exposed portion of the coarse aggregate may be rounded by rubbing with an appropriate brush. This work can be performed at the same time during the work of exposing the coarse aggregate by grinding the asphalt mixture laying road surface with a hard brush or the like. It should be noted that coarse aggregate that has already been rounded, for example, river gravel may be used from the beginning.

In order to further reduce the surface roughness of the exposed surface of the coarse aggregate, it is preferable to use fine polishing powder and polish the exposed portion of the coarse aggregate along the entire shape with a fibrous pad. . It should be noted that polishing only the upper end surface of the coarse aggregate does not result in a slippery road surface.

It is preferable to use limestone as the coarse aggregate. Limestone is rarely used as an aggregate for paved roads because of its poor wear resistance, but it is relatively easy to make it round and to reduce the surface roughness. Although the wear resistance is inferior, the abrasion amount of general-purpose aggregate is about 15% and the abrasion amount of limestone is about 20%, which meets the condition of 30% or less of the pavement guideline standard.

The low-μ road surface asphalt pavement of the present invention preferably has a relatively porous portion or unevenness on the road surface layer in order to improve the supply of water to the contact surface with the tire.

As the asphalt mix, open-grained ascon (pavement material that produces a porous road surface with a small amount of fine particles and asphalt content) is the most suitable in consideration of slipperiness, but the pavement strength remains uncertain because there are many voids. . Gap ascon (asphalt pavement material made by removing aggregates in the middle particle size of the continuous particle size distribution from coarse particles to fine particles) is superior in consideration of the severity of braking during dry There is.

Therefore, depending on how the test road is used, the road surface made of the open-grained ascon and the road surface made of the gap ascon can be distinguished so that the vehicle can be driven in a place where there is a large impact during braking or a place where the usage condition is severe as a test course. It can be said that it is appropriate to use the gap ascon and use the open grain size ascon in places where the vehicle is relatively gentle (for example, on an uphill road or a course where only straight roads are available).

<Operation> When the coarse aggregate is exposed on the asphalt surface, the tire contacts only the coarse aggregate and does not contact the asphalt surface. As a result, the anti-slip effect due to the contact of the tire with the asphalt surface is lost. Further, it becomes easy to supply water between the tire and the road surface, and the supplied water makes the tire slippery.

Reducing the surface roughness of the coarse aggregate lowers the road surface μ and makes the tire more slippery.

The exposed portion having a rounded shape does not have a corner portion so that the slipperiness of the tire is not adversely affected, water is easily introduced between the aggregate surface and the tire surface, and the tire is further slippery. Further, the rounded shape of the aggregate eliminates a feeling of strangeness in driving feeling caused by the exposed (protruding) aggregate.

Visually, the paved road of this configuration does not give the test driver a feeling of strangeness different from that of a normal asphalt paved road, and does not adversely affect the sensory evaluation of the running stability of the vehicle.

<< Embodiment >> An embodiment of the present invention will be described below with reference to the drawings.

Example 1 The low-μ road surface asphalt pavement of this example was made as a test road, and as shown in FIG. 1, in the main pavement 1, coarse aggregate 3 was exposed on the asphalt surface 2a. ing. The asphalt mixture composed of the coarse aggregate 3, the fine aggregate 4, the asphalt 2, and the filler (fine particles) not shown is the same as the one usually used. Exposed part of coarse aggregate 3
3b has a round shape, and its exposed surface 3a has a small surface roughness.

The paved road 1 is made by the following construction method.

First, coarse sand is sprinkled on a normal asphalt pavement 5 as shown in FIG.
As shown in the figure, the road surface treatment wheel 9 to which the iron brush rotary brush 8 is attached is moved to remove the asphalt surface layer 10 to a depth at which it does not contact the tire. FIG. 3 shows the pavement 6 treated in this way, where 7 in the figure represents the removed asphalt surface. Then, after spraying a mixture of fine polishing powder (silicon powder 4000 ^# ) and water on the road surface, the road surface is polished with a cleaner 12 equipped with a pad 11 made of polyester fiber as shown in FIG. As shown in FIG. 4, the exposed surface of the coarse aggregate 3 is finished to have a small surface roughness.

When the tire 13 of the traveling vehicle comes into contact with the main paved road 1 thus completed as shown in FIG.
As shown in the figure, the tire contact surface of the pavement 1 is exclusively the surface 3a of the coarse aggregate 3 having a small surface roughness. And asphalt surface
The water 14 that can be supplied between the tire 2 and the tire 2a makes the tire 13 slippery.

Comparative Example A paved road is prepared in almost the same manner as in Example 1, except that the exposed upper part of the coarse aggregate is ground with a polishing machine equipped with a flat plate-shaped grindstone instead of brushes, as shown in FIG. Then, the exposed surface 3a of the coarse aggregate 3 is finished to be flat. The surface roughness is the same as that of the first embodiment.

In such a paved road, since the corners 3c of the coarse aggregate 3 form the corners, the paved road acts to stop the slipping tire, and thus does not exhibit desired slip characteristics. Further, since the water supplied onto the asphalt surface is almost vertical at the corners and below due to the existence of the corners 3c, it is difficult for the water to enter between the tire and the upper surface of the coarse aggregate. It is hard to slip.

Example 2 Example 1 except using limestone (crushed stone) as coarse aggregate
The same procedure is used to make a paved road with a similar structure and similar sliding characteristics. Since the coarse aggregate of limestone used here is easy to grind, this pavement is less laborious to construct than the pavement of Example 1 using ordinary coarse aggregate. If the coarse aggregate is worn down due to long-term use or extreme use, the pavement can be restored to its original state by removing the asphalt surface layer again.

Test Example The characteristics of the road surface shapes of several paved roads manufactured according to Example 1 were examined with a surf tester. BPN value as an alternative measure of μ value (BPN = B ritish P ortable skid resistance
tester N omber) was used.

BPN50 (μ conversion 0.45-0.55) Fig. 11 (a), (b)
And the average surface roughness of each road surface shown in the oscillographs of (c) is 2.12, and it is shown in the oscillographs of BPN30 (0.25-0.35 μ conversion) in Fig. 12 (a), (b) and (c). There was a clear difference with the average surface roughness of 0.81 for each road surface. This shows that the μ value of the road surface can be controlled by changing the surface roughness of the exposed surface of the coarse aggregate.

The explanatory symbols in the oscillographs in Fig. 11 and Fig. 12 mean the following: CUTOFF = 0.8mm ... Indicates that measurement is impossible if there is a height difference of 0.8mm or more per measurement length. ． TRAUERSING LENGTH = 2.5mm ... Indicates that the measurement length is 2.5mm. MAG. = 2000 ... Indicates that the vertical magnification is 2000 times. Ra: center line average roughness. Rt: maximum height [sum of height above the center line (P side) and opposite side (V side)]. Rmax: Maximum height obtained by correcting the inclination of the center line. Rz: 10-point average roughness (value obtained by averaging 5 peaks and 5 valleys in the tilt correction cross section).

<Effect of device> As is clear from the above description, the low-μ road surface asphalt pavement of the present invention is formed with appropriate unevenness for facilitating water supply over the entire road surface. Since the desired friction coefficient-slip characteristics are exhibited by the specific shape and surface roughness, it is possible to constantly reproduce the fairly slippery road surface encountered on public roads.

Also, since the coarse aggregate under the asphalt surface of the pavement of the present invention is a mixture of asphalt and fine aggregate,
The coarse aggregate is firmly fixed on the asphalt surface.

Therefore, the paved road of the present invention is suitable as a test running road for evaluating the slip stability of a vehicle on the most concerned road surface, and can greatly contribute to improving the safety of the vehicle.

In addition, the pavement of the present invention is made of general asphalt pavement material without using any special material, so it can be constructed at low cost as a test road with a low μ road surface, can be constructed in a short period of time, and has no discomfort with ordinary roads. There is no special maintenance cost.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an asphalt pavement with a low μ road surface according to an embodiment of the present invention, FIGS. 2 to 4 are views showing a continuous construction process of the pavement, and FIG. 5 is an asphalt surface layer. FIG. 6 is a diagram showing a method of removing the coarse aggregate, FIG. 6 is a diagram showing a method of polishing the exposed coarse aggregate, FIG. 7 is a diagram showing a state where the tire is in contact with the paved road of one embodiment, and FIG. FIG. 9 is a partially enlarged view of the figure, FIG. 9 is a cross-sectional view showing a paved road of a comparative example, FIG. 10 is a view showing μ change on various road surfaces, and FIGS. 11 (a), (b) and (c) are The figure which shows the result of having investigated the surface condition of the road surface of three examples of BPN50 with the surf tester, and FIG. 12 (a), (b) and (c) is a figure regarding the road surface of BPN30 similarly. In the figure: 1 ... paved road, 2 ... asphalt 3 ... coarse aggregate, 3a ... exposed surface 3b ... exposed part 7 ... removed asphalt surface layer 13 ... tire, 14 ... water

Claims (2)

(57) [Scope of utility model registration request] 1. A coarse aggregate of an asphalt mixture is exposed on the asphalt surface, and a fine aggregate is mixed with asphalt around the coarse aggregate under the asphalt surface, and an exposed portion of the coarse aggregate. The low-μ road surface asphalt pavement is characterized by a round shape. 2. The low-μ road surface asphalt pavement according to claim 1, wherein the exposed portion of the coarse aggregate is further reduced in surface roughness by polishing.