JPS6047403B2 - Method for modifying asphalt pavement materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for modifying asphalt pavement materials.

Specifically, it relates to a method for modifying asphalt pavement materials, which comprises adding a powdered polyolefin polymer and rubber latex in the form of paste during the mixing stage of producing a heated asphalt mixture in an asphalt plant. There is.

Asphalt has traditionally been widely used as a binding material for flexible pavement because it is durable, workable, and economical.

However, in recent years, due to the increase in traffic volume, the function of the pavement surface has deteriorated due to "abrasion" caused by ruts, wavy flow, tire chains, tire studs (spikes), etc. caused by the repeated passage of heavy vehicles, which has become a serious issue in the maintenance and management of road pavements. This causes many problems, and improvements are strongly desired.
In response to the demands of the times, recently asphalt production plants or intermediate processing plants have modified asphalt by adding a modifier in advance and supplied it to a heated asphalt mixing plant. A method of producing a heated asphalt mixture using mixed asphalt (hereinafter referred to as a premixing method), or a method of producing a heated asphalt mixture by adding a separately prepared modifier directly into the mixer according to the supply of asphalt during mixing in a heated asphalt mixture manufacturing plant. Many attempts have been made to modify asphalt using a method of modifying and producing a heated asphalt mixture (hereinafter referred to as the "plant mixing method"), or using a resin system as a modifying material, and some of these methods have shown no improvement results. However, there are some difficulties in the modification method.

For example, regarding a modification method using plant mixing method J in which the modification material is a solid resin such as powder, granules, or flakes, a predetermined amount of resin is heated during the mixing process stage of producing an asphalt mixture. The operation itself is extremely simple, as it consists of simply charging the resin into a mixer, but in order to obtain the desired modification effect, it is important to disperse the resin as evenly as possible in the heated asphalt mixture. However, the melting temperature of the resin used here is considerably higher than the mixing temperature of the heated asphalt mixture, and the mixing time must be kept to the minimum necessary to prevent asphalt deterioration. However, the time (the minimum time required for the asphalt film to uniformly cover the surface of the skeleton particles throughout the mixture, usually between 20 and 4 [phases]) is very short, so the state of dispersion of the asphalt in the modifier is It was by no means good. On the other hand, from the point of view of dispersibility, rubber latex, which is a rubber-based modifier,
A possible method is to use a resin emulsion of a resin-based modifier. This method has superior dispersibility compared to solid resins, but the resin used for resin emulsions is soft and has a relatively low melting point compared to solid resins due to emulsification. From where the system resin is used,
Due to the softness of the resin, it is difficult to obtain the desired modification effect. Furthermore, in the method of charging powdered resin and rubber latex into a mixer at the same time, a long mixing time is required for the powdered resin and rubber latex to be evenly dispersed and mixed in the asphalt. As the deterioration of the resin progresses, the effect of preventing thermal deterioration of the resin due to the moisture in the latex wears off, and if the mixing time is shortened to prevent this, the dispersion of the latex and resin will not be homogeneous and the modification effect will be diminished. Ru.

On the other hand, in the premix reforming method, a transport vehicle with premix production and storage equipment and a special tank is required. It is inconvenient and uneconomical because it requires vehicles, receiving storage equipment, heating equipment, weighing machines, etc., and when implementing it, there are losses due to residual items in the storage equipment and losses due to discrepancies between the transportation unit and the actual amount used. be.

In order to solve these drawbacks, the present inventors! We have invented a method of adding powdered resin and rubber latex in the form of a paste during the mixing stage when a heated asphalt mixture is produced in an asphalt plant, which will be described in detail below.

The asphalt plant in the present invention refers to a stationary or mobile plant equipped with a known aggregate heating device, measuring device, and mixing device, and the heated asphalt mixture refers to a plant made of heated aggregates of various particle size ranges. Asphalt refers to all asphalts that can be used for pavement, but usually refers to straight asphalt, and rubber latex refers to rubber latex such as chloroprene rubber, styrene-butadiene rubber, isoprene rubber, acrylonitrile rubber, butyl rubber, etc. Powdered resins include polyethylene, atactic polypropylene, isotactic polypropylene, ethylene-acetate pico-polymer, ethylene-ethyl acrylate copolymer, enoethylene-methyl copolymer, etc. selected from.

Preferably, it refers to a thermoplastic polyolefin polymer having a melt index of 20 to 4 (4) and a particle size of 0.3 W$L or less.

In addition, the term "glue-like" refers to all cases in which rubber latex and powdered resin form a paste state at an appropriate mixing ratio, but usually the ratio is in the range of 2:1 to 1:3 in terms of solid content weight ratio. It refers to a certain proportion, and there is no particular range to be specified for the amount added, but generally the paste composition of the present invention is 1 to 15% by weight based on asphalt.
The purpose is achieved by using proportions such that .

The paste-like composition according to the present invention can be prepared by placing a fixed amount in a polyethylene bag or container that easily melts at a temperature of 150°C or lower, and when using it, simply adding it to the mixer hairsphalt while kneading the mixture. It is convenient because the asphalt can be modified by adding a predetermined amount afterwards.

According to the method of the present invention, the pasty composition is simply put into the mixing process of an asphalt plant in a bag or container that easily dissolves at the mixing temperature of the heated asphalt mixture. There is no need for any special equipment as in the premixing method, and since the paste composition of the present invention is a paste composition of powdered polyolefin polymer and rubber latex,
Even when viewed microscopically, this composition has fine rubber latex solids and polyolefin polymer dispersed in a state in which they evenly coexist in liquid phase water.

Therefore, when this heated asphalt mixture is put into a mixer during mixing, the water contained in the paste-like composition according to the present invention is rapidly converted to steam, and the stirring and dispersion effect due to expansion and foaming causes the mixture to be mixed. The asphalt is also foamed by the water vapor, and the components in the pasty composition of the present invention as a modifier are easily mixed and dispersed in the asphalt in a short period of time. It diffuses into the mixture as water vapor and then into the outside air during the mixing process. In this way, since the asphalt in the heated asphalt mixture is cut off from contact with oxygen by the water vapor, not only the solid content of the latex and the polyolefin resin but also the asphalt in the heated asphalt mixture have a function of preventing deterioration. This is extremely large, and therefore the improvement effect is large. Furthermore, since the mixing time can be shortened due to the excellent dispersibility, this in itself can prevent the deterioration of the asphalt, the latex solid content in the pasty composition of the present invention, and the polyolefin resin itself during mixing, so it has the effect of killing two birds with one stone. be. Examples of the excellent dispersibility will be explained below.

Examples Table 1 shows those using the paste-like composition according to the present invention, those using rubber latex and powdered polyolefin-based polymer added separately, those using powdered polyolefin-based polymer alone, and those using the paste-like composition according to the present invention. The relationship between mixing time and wheel tracking test showed that the dispersibility was better than in either case.

The mixture is a dense-grained asphalt concrete based on the "Asphalt Paving Guidelines" published by the Japan Road Association, with an asphalt content of 6%.

(1) Asphalt is 60/80 strained asphalt.

(2) The powdered resin is amorphous polypropylene manufactured by Mitsubishi Yuka.

(3) Rubber latex is made by Japan Synthetic Rubber.

(4) For mixing, use a 25kg kneading machine mixer.

(5) The wheel tracking test was conducted according to the asphalt pavement guidelines with a wheel load of 8 tons. The specimen was 6 under the same conditions.
The batches were mixed, and test specimens prepared for each batch were used to determine the average value and standard deviation by a wheel tracking test.

Claims (1)

[Claims] 1. When producing a heated asphalt mixture in an asphalt plant, in the mixing stage, a pasty composition consisting of a powdered polyolefin polymer and rubber latex in a solid content weight ratio of 2:1 to 1:3 is added to asphalt. A method for modifying a paving material, the method comprising adding 1 to 15% by weight of the material.