JPH034682B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) This invention relates to a bituminous mixture used in special pavements such as bridge pavements. For more information,
In a binder made of bituminous material and an olefinic polymer, the olefinic polymer is made of an ionomer resin, resulting in a novel bituminous mixture in which the porosity of the mixture is 2% or less. (Conventional technology) Bridge surface pavement, which has conventionally required the most advanced performance and construction technology among pavements, especially the bituminous mixture used on steel deck slabs, has a performance that is limited to the deformation that occurs on steel deck slabs. It must have the flexibility to follow suit, it must have the stability to prevent flow or deformation due to wheel loads at high temperatures, it must have the elongation ability to prevent cracking due to embrittlement at low temperatures, and it must be able to resist moisture that corrodes the steel deck. It is required to be impermeable to water to prevent penetration.
Here, straight asphalt or asphalt modified material is used to generally
When using a conventional asphalt mixture heated to 10°C (heated asphalt mixture) as the bituminous mixture on the steel deck, the porosity of the asphalt mixture should be reduced to at least It was necessary to maintain it at 3% or higher. However, a bituminous mixture having such a porosity has a large permeability coefficient, and a problem arises in that the durability of the steel deck and steel girder is reduced due to oxidation corrosion of the steel deck by rainwater etc. that permeates through the bituminous mixture layer.
To prevent this, a waterproof layer has been provided between the steel deck slab and the bituminous mixture. However, providing a waterproof layer on the steel deck slab in this way increases the complexity and cost of construction, and the waterproof layer can also cause defects in the upper bituminous mixture layer that can slip and cause pavement failure. was also often seen. In addition, this conventional heated asphalt mixture is said to have poor flexibility and is prone to cracking, so it is not widely used. Under these circumstances, goose asphalt, which is a water-impermeable pavement mixture, is usually used as the bituminous mixture on the steel deck. This goose asphalt is generally paved by pouring and spreading a fluidized bituminous mixture (crushed stone, sand, stone powder, and asphalt) on steel slabs by curing at a high temperature of 210 to 251 degrees Celsius. , this goose asphalt is used in combination with straight asphalt with a bituminous content of 20/40 and natural asphalt with a bituminous content with a smaller penetration, and also with a filler content of stone powder of 20/40.
It is characterized by an extremely high content of ~30%, compared to several percent of ordinary heated asphalt mixtures. However, straight asphalt and natural asphalt with a penetration of 20/40 are materials that are not commonly used for paving, and are often inconvenient to obtain, handle, store, and heat. Requires extra equipment and storage of equipment and materials compared to manufacturing mixtures. In particular, natural asphalt is packaged in the form of a solid lump poured into a paper container, etc., so when it is used, it requires equipment and work to heat and melt it again after crushing it. In addition, when mixing, each material requires equipment that heats it to a higher temperature than the heated asphalt mixture normally used for paving, and since a large amount of filler is used in particular, the aggregate drum dryer that is normally used in heated asphalt plants cannot be used. It cannot be heated directly together with the aggregate, and a separate heating device is required. Furthermore, in order to improve work efficiency, from the time of mixing to the time immediately before construction, special equipment is required to heat, mix, or stir the mixture to around 230 degrees Celsius, which is several tens of degrees higher than the normal mixture temperature. Requires. In addition, because the temperature of the mixture during leveling is high, it can cause thermal deformation of the bridge girder and steel deck, which are the main structure of the bridge, and thermal deterioration of the anti-corrosion paint. There were many problems such as a decrease in rust prevention effect due to deterioration, and peeling of the coating due to decrease in adhesion. Furthermore, in terms of physical properties, there still remains a problem in that the flatness of the road surface is impaired by dents in ruts, that is, ruts, which occur due to plastic flow due to wheel loads at high temperatures in summer. (Problems to be Solved by the Invention) In order to solve these problems, a bituminous mixture for pavement that is impermeable to water and has high plastic flow resistance is manufactured and constructed using ordinary equipment from the viewpoint of versatility. To achieve this, it is possible to reduce the porosity of the bituminous mixture by increasing the amount of bituminous binder modified with an asphalt modifier or by increasing compaction energy. However, it is known that the bituminous mixture for pavement obtained in this way cannot be used for pavement purposes at all because the strength properties and plastic flow resistance decrease significantly with the decrease in porosity with the current asphalt modified material. It is being For example, increasing viscosity with hard asphalt (semi-blown asphalt) and other olefinic thermoplastic resins such as polyethylene, ethylene vinyl acetate copolymer, ethylene ethyl acrylic acid copolymer, atactic polypropylene, ethylene methacrylic acid copolymer, etc. When bituminous material is modified and the porosity is reduced by increasing the amount of binder, as shown in Table 1, as the porosity decreases, the dynamic stability as determined by the wheel tracking test, that is, the plastic flow decreases. The composition deteriorated significantly and it was not possible to obtain a bituminous paving mixture with sufficient durability to withstand traffic loads.

[Table] Therefore, the present invention aims to provide a bituminous mixture for pavement that has high plastic flow resistance at high temperatures, is impermeable to water, and has excellent flexibility while using ordinary construction equipment. be. (Means for Solving the Problems) In order to solve the above-mentioned conventional problems, the inventor of the present invention, as a result of intensive research, discovered the limit of porosity at which a bituminous mixture for pavement becomes impermeable to water. In this area, the use of a bituminous binder consisting of 93 to 75 parts by weight of bituminous material and 7 to 25 parts by weight of ionomer resin can be achieved without any changes to the production equipment or construction machinery for conventional hot asphalt mixtures. The inventors have discovered that a bituminous mixture for pavement that is permeable to water and has excellent plastic flow resistance and flexibility at high temperatures can be obtained, leading to the completion of the present invention. The present inventor believes that when the porosity of a bituminous mixture decreases based on the idea of impermeable pavement, the form of the pores changes from continuous pores that allow water to pass through, to individual bubbles, and as a result, it becomes impervious to water. Considering that there is a limit to the porosity, we measured the hydraulic conductivity of the mixture. There were four types of mixtures used in the test: dense-grained asphalt (13), fine-grained ascon (13), fine-grained asphalt (13F), and asphalt mortar as shown in the asphalt pavement guidelines (Japan Road Association). For each specimen, specimens with different porosity were created using a compaction device for marshal testing. The dimensions of the specimen used in the test were 10.16cm in diameter and 6.35cm in height, and the test was conducted at 15℃.
The experiments were carried out in a constant temperature room. The hydraulic conductivity is 2Kg
It was determined from the relationship between elapsed time and water permeability under a constant water head with a pressure of f/ ^cm2 , and the results are shown in Table 2.

【table】

[Table] Shows what was taken.
From this result, the bituminous mixture of any composition has water permeability when the porosity is 3% or more, but it becomes difficult to permeate when the porosity is less than 3%.
% or less, the mixture of any formulation becomes water-impermeable. This proves that if the porosity in the mixture, which was originally envisioned by the inventor, decreases, the air bubbles contained therein become independent and can no longer serve as paths for water to penetrate. be. From the above, it can be considered that it is sufficient for the area where the bituminous mixture for pavement according to the present invention is impermeable to water to have a porosity of 2% or less. The bituminous material can be used for paving,
When measured according to JIS-K2531, the softening point is 30~
130°C, preferably a softening point of 40-90°C, and is solid or semi-solid at room temperature (20-25°C). This bituminous material is selected from those that are solid or semi-solid at room temperature, such as straight asphalt, natural asphalt, semi-blown asphalt, blown asphalt, pitches, tars, and petroleum resin binders for colored pavement. Among these, straight asphalt, natural asphalt, semi-blown asphalt, blown asphalt, and petroleum resin binders for colored pavement are desirable because they have good compatibility with ionomer resins and have a large effect on improving strength properties. The ionomer resin is a copolymer of α-olefin and a monomer having a carboxylic acid, and is a polymer group in which molecular chains are cross-linked with metal ions using carboxyl groups, and the present invention does not include this meaning. ionomer resins are used.
Among these, ionomer resins having a structure in which the molecules of a copolymer of ethylene and unsaturated carboxylic acid (for example, acrylic acid, methacrylic acid, etc.) are crosslinked are preferable, and in particular, the metal ions are composed of Zn ions and the melt index is 1.0 or more. , and those having a large specific surface area such as granules, powders, flakes, and pellets are desirable because they have a large modifying effect. Note that powdered resin is better from the viewpoint of handling during work and processing. Although ionomer resin is a thermoplastic resin, it has metal ion bonds in the temperature range where it solidifies.
It is very strong like a thermosetting resin, has moderate elasticity and flexibility, and its ionic bonds weaken at high temperatures.
It has the property of being melted like a thermoplastic resin. Therefore, a bituminous binder modified with an ionomer resin has excellent plastic flow resistance and flexibility at high temperatures. The amount of ionomer resin added is determined by the wheel tracking test (ground contact 6.4 Kgf/cm ² , 60
In order to have as high a dynamic stability as possible (at least as high as that of goose asphalt) at 100° C.), it is necessary that the amount is 7 parts by weight or more based on 93 parts by weight of bituminous material. Moreover, if it is used in an amount exceeding 25 parts by weight based on 75 parts by weight of bituminous material, the viscosity of the bituminous pavement mixture increases, which is not preferable.

[Table] Ordinary sand, gravel, crushed stone, etc. are used as aggregates for the mixture. As the filler, materials commonly used for bituminous pavement such as calcium carbonate, slaked lime, and cement are used. The mixing ratio of the bituminous binder, aggregate, and stone powder varies depending on the composition ratio of the bituminous binder, the type of aggregate, stone powder, etc., but in the bituminous mixture according to the present invention, the porosity is 2% or less. The blending ratio of the bituminous binder is approximately 7 to 15 parts by weight based on the entire bituminous mixture. The bituminous mixture according to the present invention can be obtained by mixing a modified bituminous binder in which an ionomer resin is dissolved in preheated and melted bituminous material with separately heated aggregate and filler, or by mixing an ionomer resin with separately heated aggregate and filler. This can be easily carried out by ordinary mixing means, such as by adding the heated bituminous material, aggregate, and filler into a mixer at the time of mixing. In addition, anti-aging agents, anti-peeling agents, pigments, plasticizers, and other rubbers that are conventionally applied to paving materials can be used together with the ionomer resin as needed, but in general, the ionomer resin is used as an aggregate. It is preferable to use it when mixing with filler or filler. When producing the bituminous mixture according to the invention, the mixing temperature is preferably 165-180°C and the compaction temperature is preferably 150-180°C. Test Example 1 Next, a test example for obtaining the present invention will be explained. The relationship between the type of mixture of Test Example 1 and plastic flow resistance and water permeability was tested in a region where the porosity was 2.0% or less. As comparative examples, ethylene vinyl acetate copolymer, chloroprene rubber, semi-blown asphalt, straight asphalt, and goose asphalt were tested. The formulation of the bituminous binder used in Test Example 1 is shown in Table 4. The ionomer resin used is Himilan #1702 (manufactured by Mitsui Polychemical KK,
ionomer resin (trade name), ethylene vinyl acetate copolymer EVAFLEX #420 (manufactured by Mitsui Polychemicals KK, trade name of ethylene vinyl acetate copolymer), and chloroprene rubber (hardway type (manufactured by Denki Kagaku Kogyo KK, product name of chloroprene rubber)). As the semi-blown asphalt, AC-100 (manufactured by Shell Oil Co., Ltd.) was used.

【table】

[Table] The types of mixtures used in the test are 1-a to 1-e.
Regarding asphalt pavement guidelines (Japan Road Association), dense-grained ascon (13), fine-grained ascon (13F), and screenings,
The mortar was mixed with sand and stone powder, and for 1-f, goose asphalt was used. 1-a~
1-e was produced by mixing for 1 minute at about 165°C in a small 2-screw pug mill mixer, and 1-f was produced by baking at about 240°C for 50 minutes in a small-sized cookie cutter. Regarding the test, in the marshal stability test, 1-a to 1-e were made by tamping specimens 50 times on each side at 160℃ under the conditions specified in the Asphalt Pavement Guidelines (Japan Road Association). The stability and flow values were calculated using In addition, the hydraulic conductivity is sample number 1-a, 1-b, 1-c, 1- in Table-4.
For the specimens d and 1-e, the specimens were prepared in the same manner as the specimens for the Marshall stability test.
In addition, for sample number 1-f in Table 4, the test specimen was poured into a mold and produced at a rate of 2Kgf/ ^cm2.
It was calculated from the elapsed time and water permeability under a constant head of water. The molding of the specimens used for the wheel tracking test is based on the district inspection numbers 1-a, 1-b, and 1- in Table-4.
Samples c, 1-d, and 1-e were molded using a roller compactor to have the same porosity as the specimen for the marshal stability test, and sample number 1-f was used.
The material was poured into a mold and molded.
Test 1 was a running test of each specimen at a temperature of 60℃ and a ground pressure of 6.4Kgf/ ^cm2 .
Dynamic stability was determined. The results of this test 1 are shown in Table-5.
It was shown to.

[Table] Shows what happened.
As is clear from Table 5, ethylene-vinyl acetate copolymer, a thermoplastic resin, chloroprene, a rubber, etc., which were conventionally used as modifiers for bituminous binders, as shown in the comparative examples, In a bituminous mixture for pavement using semi-blown bituminous asphalt, the plastic flow resistance decreases significantly in areas with low porosity that exhibit water impermeability, and the dynamic stability is 500 or more, which is considered desirable for practical purposes. While it is not possible to secure
When using the bituminous binder modified with the ionomer resin according to Test Example 1, it showed an extremely high improvement effect on all types of mixtures, and the value was higher than that of Comparative Example in terms of dynamic stability. -b, 1
-c, 1-d, 1-e, 15~
It is 50 times more. Further, even in the case of the goose asphalt shown in Comparative Example 1-f, the value is only slightly over the practical minimum value of 300, which is by no means a desirable value. On the other hand, in the case of Test Example 1, it was observed that a mixture showing a value 4 to 13 times higher than that was obtained. Test Example 2 Here, a test was conducted on the flexibility at low temperatures in order to examine the ability to follow the deflection of steel deck slabs and the degree of embrittlement at cold temperatures. As comparative examples, those using chloroprene rubber and goose asphalt were tested. The formulation of the bituminous binder used in Test Example 2 is shown in Table 6. The ionomer resin used is Himilan #1702 (manufactured by Mitsui Polychemical KK,
(Product name of ionomer resin), hardware type (Denki Kagaku Kogyo KK,
(trade name of chloroprene rubber) was used.

【table】

[Table] In addition, the formulation of cloprene rubber shown in 2-b is
The reason why the amount is 6.5 parts by weight is that if more than this amount is added, the viscosity of the mixture will increase significantly, making the mixability and workability unfavorable. The types of mixtures used in Test 2 were fine-grained asphalt (13F) and goose asphalt as shown in the Asphalt Pavement Guidelines (Japan Road Association), and the former was mixed with a small two-shaft pug mill mixer to approx.
The mixture was mixed at 165°C for 1 minute and then molded using a roller compactor to a thickness of 5 cm to the specified density.For the latter goose asphalt, it was packed at about 240°C for 50 minutes using a small puncher. The sample was poured into a mold to have a width of 5 cm, and after being released, the sample was cut to a width of 5 cm using a concrete cutter to provide a specimen for bending tests. The bending test was performed using a bisecting point loading method with a span length of 20 cm, and the loading device was a servo pulser Lab-5U.
(manufactured by Shimadzu Corporation). The loading speed is
50mm/min, and the specimen temperature was -10℃. The strain at break is calculated using the following formula: ξ=6・h・d/I ^2Where , ξ: Strain at break h: Thickness of specimen (cm) d: True amount of deflection at break (cm ) I: Span length (cm) The deflection at break d was calculated from the amount of movement of the actuator and corrected all errors caused by the loading device and bending jig to determine the true amount of deflection of the specimen. The general formula for correction is as follows. d=d′+d″ Where, d: True deflection amount of the specimen (cm) d′: Actuator movement amount (cm) d″: Error due to deformation of loading device and bending jig (cm) (However, , displacement in the same direction as the deflection direction of the specimen is considered positive) The results of Test Example 2 are shown in Table 7.

[Table] As is clear from Table 7, the flexibility of the bituminous mixture according to Test Example 2 is extremely superior to that made of rubber, which is conventionally known to have excellent flexibility, and to goose asphalt. was recognized. (Example) Next, an example of the present invention will be shown below. A bituminous mixture according to the invention was produced in an asphalt plant in order to check the mixability in a conventional mixing plant. The asphalt plant was a batch type plant with a capacity of 800 kg/batch, the mixing temperature was 170°C, and the mixing time was 1 minute. The ionomer resin (manufactured by Mitsui Polychemical Co., Ltd., Himilan #1702) was added in powder form at the time of mixing the aggregate, filler, and asphalt (straight asphalt 60/80). Regarding the bituminous mixture thus produced, Test Example 1
Similarly, a marshal stability test and a wheel tracking test were conducted. The test results of this example are shown in Table-8.

[Table] Table 8 shows that in actual asphalt plants, as in the laboratory experiments, a mixture with a porosity of 2% or less, that is, water-impermeable mixture, and extremely high plastic flow resistance can be obtained. (Effects of the Invention) The present invention provides a mixture for pavement consisting of bituminous material, an ionomer resin, an aggregate, and a filler, which is heat-mixed, used for paving, and compacted. The resin has a structure in which metal ions are interposed in an olefinic polymer, and the ionomer resin is made by adding 7 to 25 parts by weight to 93 to 75 parts by weight of the bituminous material, and compacted. The intended objects of the present invention are achieved because the mixture is a bituminous paving mixture in which the porosity of the mixture is less than 2%. It has been shown that the bituminous mixture of the present invention, that is, one with a porosity of 2% or less, can be made water impermeable, and by modifying the bituminous binder with an ionomer resin, the porosity can be reduced to 2%. % or less, a bituminous mixture for pavement with sufficiently high plastic flow resistance can be obtained. Therefore, it is convenient because conventional mixing methods and construction methods can be used without the need for special equipment or machines that are conventionally used in the production and construction of goose asphalt as a bituminous mixture with a small porosity. In addition, when the porosity is 2% or less, it goes without saying that ordinary heated asphalt mixtures are used, as well as heated modified asphalt mixtures modified with conventional resin or rubber systems, or goose asphalt. However, although it lacks plastic flow resistance at high temperatures and flexibility at low temperatures, the bituminous mixture according to the present invention exhibits extremely excellent effects on plastic flow resistance and flexibility. Further, the bituminous mixture according to the present invention is effective not only for ordinary pavements but also for bridge surfaces, especially steel deck pavements, lining pavements, and places requiring waterproofness such as waterways.

Claims (1)

[Scope of Claims] 1. A mixture for paving consisting of bituminous material, ionomer resin, aggregate, and filler, which is heat-mixed, used for paving, and compacted, wherein the ionomer resin is It is a resin having a structure in which metal ions are interposed in an olefin-based polymer, and the ionomer resin is made by adding 7 to 25 parts by weight to 93 to 75 parts by weight of the bituminous material, and is a compacted mixture. A bituminous mixture for pavement use characterized by a porosity of 2% or less. 2. The bituminous mixture for paving according to claim 1, wherein the bituminous substance is straight asphalt. 3. The bituminous mixture for paving according to claim 1, wherein the bituminous substance is natural asphalt. 4. The bituminous mixture for paving according to claim 1, wherein the bituminous material is blown asphalt. 5 The ionomer resin contains Na ions or Zn between the molecules of the copolymer of ethylene and acrylic acid.
The bituminous mixture for paving according to claim 1, which has a structure in which ions are interposed. 6. The bituminous mixture for paving according to claim 1, wherein the ionomer resin has a structure in which Na ions or Zn ions are interposed between molecules of a copolymer of ethylene and methacrylic acid. 7 The ionomer resin is a melt index
1.0 or more and is in the form of a powder, the bituminous mixture for paving according to claim 1. 8. The bituminous mixture for paving according to claim 1, wherein the aggregate is one of sand, gravel, and crushed stone. 9. The bituminous mixture for paving according to claim 1, wherein the filler is one of calcium carbonate, slaked lime, and cement.