JP2002121388A - Asphalt mixture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an asphalt mixture which has excellent compression strength and deflection properties so that when a roadway or a roadbed is weak, a breaking or the like due to a traffic load does not occur, and which is suitable for a surface layer material of a water permeable pavement in a low traffic carriageway. SOLUTION: The asphalt mixture comprises adding a thermoplastic elastomer (SBS) and a middle-density polyethylene to asphalt. The mixture has excellent deflection properties and bending strength, and is strong against a replication of a load. For these reasons, when the traffic load occurs in a state of the roadway and the roadbed becoming weak, deformation flexibly corresponding to the load is possible to prevent destruction thereof, and further the breaking thereof hardly occurs.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an asphalt mixture used for paving a road such as a road. More particularly, the present invention relates to an asphalt mixture suitable as a surface material for permeable pavement on a low traffic road such as a living road.

[0002]

2. Description of the Related Art In recent years, in view of measures against rainwater accompanying the progress of urbanization,
It is required to provide permeable pavement on low traffic roads.
The surface layer material for permeable pavement has a porosity of 3 to 6 that of a general pavement material.
%, And the contact area between the aggregates is smaller than that of the conventional pavement material. For this reason, asphalt with stronger bonding power is required. Therefore, it has been attempted in various places to convert the surface material of drainable pavement using high-viscosity asphalt used for highways and the like into a permeable pavement of a low traffic road.

[0003]

However, the above-mentioned conventional trial has the following problems. In other words, the surface material of the permeable pavement is required to have compressive strength (marshall stability) and flexibility so that cracks and breakage do not occur due to traffic loads even when the roadbed and subgrade are softened. However, surface materials for drainage pavement have been developed on the premise that they are applied to roadbeds and subgrades that do not soften, so their flexibility is inadequate regardless of compressive strength. Therefore, even in the above trial, the actual location of the surface layer material is actually limited to a permeable sandy subgrade without fear of softening. This is because the surface material used on a non-sandy subgrade may be cracked due to low flexibility. It should be noted that the flexibility of the pavement material has hardly been considered in the past, and at present it is not specified in the asphalt pavement requirements.

[0004] The surface material of the permeable pavement for low traffic roads may have slightly lower compressive strength and dynamic stability than the surface material of drainage pavement used for heavy traffic roads such as highways.
Flexibility must be excellent. Also, compared with the surface layer material for permeable pavement used for pavement and parking lot, it is necessary to have excellent compressive strength, dynamic stability and flexibility.

[0005] The present invention has been made to solve the above-mentioned problems of the prior art. In other words, the problem is that it has a compressive strength and flexibility that does not cause cracks due to traffic load even if the roadbed or subgrade softens, and is suitable as a surface layer material of permeable pavement on low traffic roads. It is to provide an asphalt mixture.

[0006]

SUMMARY OF THE INVENTION The asphalt mixture according to the present invention made to solve this problem contains asphalt, a thermoplastic elastomer, and polyethylene. Generally, it further contains aggregates and fillers. In this asphalt composition, the thermoplastic elastomer exists in a state of being dissolved and mixed in the asphalt. That is, the thermoplastic elastomer is an asphalt modifier. on the other hand,
Polyethylene exists as a lump without being dissolved in asphalt. Therefore, it can be seen that polyethylene substantially functions as an aggregate (or a part thereof).

In the asphalt mixture of the present invention, it is desirable that the asphalt is semi-blown asphalt, the thermoplastic elastomer is a styrene / butadiene / styrene block copolymer, and the polyethylene is a medium density polyethylene. The composition was as follows: 4 to 5 parts by weight of an asphalt composition containing semi-blown asphalt and styrene / butadiene / styrene block copolymer;
What is necessary is just to consist of 0.7 to 1.4 parts by weight of medium density polyethylene and the balance of aggregate and filler. In addition, the composition of the asphalt mixture is semi-blown asphalt 90
It may be で あ れ ば 95 parts by weight and styrene-butadiene-styrene block copolymer 5５〜10 parts by weight.

[0008] The reason for using semi-blown asphalt as asphalt is that the asphalt mixture using the same shows compressive strength and bending strength while exhibiting the same degree of dynamic stability as that using straight asphalt. This is because they have excellent strength and bending strain. The reason that the styrene-butadiene-styrene block copolymer is used as the thermoplastic elastomer is that it does not contribute to the increase in the compressive strength of the asphalt mixture, but improves the bending strength and bending strain. If the mixing ratio is too large, the compatibility with asphalt deteriorates, so that a ratio within the above range is appropriate. The reason why the medium-density polyethylene is used as the polyethylene is that, although there is a tendency to slightly reduce the bending strength and bending strain of the asphalt mixture, the compression strength is greatly increased. If the mixing ratio is too large, the viscosity of the mixture increases and it becomes difficult to handle the mixture. If the mixing ratio is too small, the effect of the addition becomes low.

[0009]

Embodiments of the present invention will be described below. First, each component of the asphalt mixture will be described.

(1) Asphalt Asphalt includes petroleum asphalt obtained by removing soft components from petroleum and natural asphalt produced naturally. The former also includes straight asphalt obtained as a residue after distilling petroleum, and blown or semi-blown asphalt obtained by subjecting straight asphalt to polymerization treatment by blowing air. Semi-blown asphalt is suitable as a raw material of the asphalt mixture of the present invention. The reason for this is that the asphalt mixture using this has excellent compressive strength, bending strength and bending strain while exhibiting the same level of dynamic stability as compared with the one using straight asphalt.

(2) Thermoplastic Elastomer Thermoplastic elastomer is a polymer substance which exhibits large rubber elasticity near normal temperature and shows plastic deformability when the temperature rises. In the asphalt mixture of the present invention, a thermoplastic elastomer is used as an additive to increase the viscosity of the asphalt. This is for imparting flexibility that does not break even when subjected to bending deformation. Styrene-butadiene-styrene block copolymer (SBS) is suitable as the thermoplastic elastomer in the present invention. The reason is that it does not contribute to the increase in the compressive strength of the asphalt mixture, but improves the bending strength and the bending strain. The basic structure of the styrene / butadiene / styrene block copolymer is "-polystyrene-polybutadiene-polystyrene-". The molecular weight is preferably about 167 × 10 ³ .

(3) Polyethylene As polyethylene, granular polyethylene having a size of about 2.5 to 5 mm is used. It does not need to be new, and even waste materials used for any purpose can be used if there is no deterioration in quality. In the present invention, among the polyethylenes, a medium density polyethylene having a density in the range of 0.93 to 0.942 g / cm ³ is suitable.

(4) Aggregate and filler The aggregate and filler used are those generally used in ordinary asphalt mixtures. Aggregates Nos. 5 and 6 specified in JIS A5501 are suitable. The filler may be one specified in JISA5508.

The process for producing the asphalt mixture of the present invention is not particularly limited. That is, an ordinary method in which only the solid components (polyethylene grains, aggregates, and fillers) are dry-mixed, and then the liquid components (molten asphalt) are added and wet-mixed. The thermoplastic elastomer as an asphalt additive may be mixed in the asphalt in advance, or may be added together with the asphalt at the time of wet mixing. As a result, the aggregate and the polyethylene particles are mixed without bias, and a mixed state is obtained in which most of the gaps are filled with asphalt (in which the thermoplastic elastomer is dissolved) and the filler. In this state, the polyethylene grains bite between the aggregates to form an integral unit. Mixing temperature (about 150-160 ° C)
This is because polyethylene particles are softened. Paving work may be performed in the same manner as in the case of ordinary asphalt mixture.

[0015]

The present invention will be described more specifically with reference to the following examples. In the following description, all “%” in the blending ratio means weight% based on the entire asphalt mixture. The raw materials used and their compounding ratios are as shown in Table 1 (all units are%).

[0016]

[Table 1]

Of the above, various physical properties of the polyethylene particles were measured. The results were as follows.

[0018]

[Table 2]

Various properties were measured for the asphalt mixture produced at the above mixing ratio, and the results were as follows.

[0020]

[Table 3]

From these results, when the examples of the present invention were compared with the comparative examples, all of them showed excellent characteristics with respect to the comparative example 1 containing neither SBS nor polyethylene. Comparative Example 2
, The cantaburo loss amount is slightly inferior, but this is a level that does not cause any problem for low traffic roads. What should be particularly noted in the embodiments of the present invention is that bending strain, which is an index of flexibility, is excellent. This indicates that the asphalt mixture according to the example of the present invention is excellent as a surface layer material for permeable pavement. In other words, even if the roadbed and the subgrade are subjected to a traffic load in a softened state, they can be deformed in response to the load flexibly because of their excellent flexibility, and do not break because of their excellent bending strength. In addition, since the loss of cantabulo is low, even if the load is repeatedly applied, the separation between the aggregate and the asphalt is small, and the crack is hardly generated.

As described in detail above, according to the above embodiment and examples, the thermoplastic elastomer (SB
By adding S) and polyethylene (medium density polyethylene), an asphalt mixture having excellent flexibility and bending strength and strong against repeated loading is realized. Therefore, this asphalt mixture is strong against traffic loads when the roadbed and the roadbed are softened, and is suitable as a surface layer material for permeable pavement.

The reason why such characteristics can be obtained by adding a thermoplastic elastomer and polyethylene is presumed as follows. First, thermoplastic elastomers (SBS) that act as asphalt modifiers
Has the property of increasing the asphalt stickiness. As a result, the asphalt exhibits strong toughness even during deformation, and it is considered that the asphalt and the aggregate are unlikely to be separated. On the other hand, polyethylene, which functions as a substitute for aggregate, has some elasticity at room temperature. It is considered that this exerts a stress relaxation effect when a load is applied, an effect to allow flexural deformation, and a deformation recovery effect when the load is released. The above characteristics are obtained by these synergistic effects.

The above embodiments and examples are merely examples, and do not limit the present invention in any way.
Therefore, naturally, the present invention can be variously modified and modified without departing from the gist thereof.

[0025]

As is clear from the above description, according to the present invention, even if the roadbed and the roadbed are softened, the roadbed and the roadbed have compressive strength and flexibility so that cracks and the like due to traffic load do not occur. Asphalt mixtures suitable as surface materials for permeable pavements are provided.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) E01C 7/26 E01C 7/26 (72) Inventor Kiyoji Koide 507-2 Shinhocho, Tokai-shi, Aichi Toho (72) Inventor Kazuyoshi Fujimoto Inventor Kazuyoshi Fujimoto 507-2 Shintakara-cho, Tokai City, Aichi Prefecture Tokai Pavement Co., Ltd.F-term (reference) GL00

Claims (2)

[Claims] 1. An asphalt mixture comprising asphalt, a thermoplastic elastomer, and polyethylene. 2. The asphalt mixture according to claim 1, wherein the asphalt is semi-blown asphalt, the thermoplastic elastomer is a styrene / butadiene / styrene block copolymer, the polyethylene is a medium density polyethylene, 4 to 5 parts by weight of an asphalt composition containing 90 to 95 parts by weight of semi-blown asphalt and 4 to 5 parts by weight of a styrene / butadiene / styrene block copolymer; and 0.7 to 1.4 parts by weight of a medium density polyethylene. And an asphalt mixture characterized by being composed of the balance of aggregate and filler.