WO2023084504A1

WO2023084504A1 - Ultra-elastic rubber asphalt using the polymerization method and symmetry technique

Info

Publication number: WO2023084504A1
Application number: PCT/IB2022/062103
Authority: WO
Inventors: Masoud ALIZADEH
Original assignee: Alizadeh Masoud
Priority date: 2021-12-13
Filing date: 2022-12-13
Publication date: 2023-05-19

Abstract

The claimed invention is " Ultra-Elastic Rubber Asphalt by Polymerization Method and the Symmetry Technique " with the aim to improve the mechanical and rheological properties of bitumen and asphalt to prevent susceptibility to damage and the occurrence of accidents for users, including cyclists. mixing rubber powder with bitumen is done by employing the "wet process". Next, favorable conditions for creating chemical bonds (transverse sulfur bond in the chain Di-en rubber)are created by mixing special bitumen with polymerization capability and fine-grained stone materials and adding rubber granules to the asphalt mixture mentioned above (dry process) in the presence of sulfur and ZnO at a 160 °C temperature. Mixing these compounds, and the simultaneous mixing of rubber powder and rubber granules with bitumen and asphalt (the symmetry technique) provide the conditions required for producing asphalt with high elasticity.

Description

Ultra-Elastic Rubber Asphalt Using the Polymerization Method and Symmetry Technique

This invention is an Ultra-elastic rubber asphalt using polymerization and symmetry techniques. It is associated with the fixed construction section- the road construction subsection (E01).

An effective property for the comfort of cycling is pavement quality. Hence, the smoothness and firmness of the pavement, as well as the appropriate flexibility of the asphalt surface, can play a crucial role in reducing cyclists' injuries during an accident. The best-known pavement for bike lanes, in terms of levelness and easy maintenance, is hot mix asphalt. Although experts in the relevant organizations are aware of the significance of asphalt flexibility in bike lanes, the need for good bitumen to produce resistant asphalt with high flexibility properties in the road construction industry makes them use asphalt sand or fine-grained asphalts. While such asphalts have a rough surface that cannot prevent damage to cyclers in accidents, considering the finer asphalt aggregates and a smoother surface compared with asphalts with coarser grains, they are the best option available presently. The invention of ultra-elastic asphalt by polymerization method and symmetry technique can be used as a new way to increase the safety of cyclists. According to research conducted worldwide, rubber powder does not tend to react with bitumen due to its network chemical structure. Based on the evidence from research around the world, researchers have only been able to mix up to 26% of the rubber powder with bitumen (with the help of lubricating oils), which is a physical mixture. Hence, mixing these two materials does not considerably increase bitumen's rheological properties. As rubber powder in asphalt as an elastomer increases the elastic property (recoverable deformation), many methods have been invented worldwide for mixing bitumen and rubber powder. Some of them are mentioned below, and their differences from our invention are described.

Patent No. EP1873212A1, registered in 2008, titled “Method for Modifying Bitumen with Waste Rubber Powder,” notes that rubber powder is first mixed with perfume oil. This mixture is mixed between 3 to 30 percent with bitumen at 140-200 °C for 5 to 40 minutes. The recorded tests revealed that the rheological properties of bitumen slightly improved. Studies conducted above indicate that the use of perfume oils raises the cost of the product, reduces the flash point of bitumen, and decreases the strength of the produced asphalts. On the other hand, the mixing of rubber powder was done merely by the wet process. According to the results of the experiments, the viscoelastic properties of the bitumen did not change significantly; therefore, the elasticity of the resulting asphalts will be minimal.

Furthermore, the article entitled "Comparison of the resistance properties of rubber asphalt and ordinary asphalt," presented at the 7th National Congress on Civil Engineering, in Shahid Nikbakht Faculty of Engineering, Zahedan by Mr. "Iqbal Shakeri" and "Fereydoun Moghadasnejad," points out that adding rubber powder to bitumen by 18 to 26% for 1 to 2 hours at a temperature of 190-218 °C, the mixture reacts with bitumen, increasing the viscosity of the bitumen and eventually remaining constant. This combination is possible by increasing the 3% of perfume oils as a lubricant. The paper says that this process leads to a relative increase in the rheological properties of asphalts made by this bitumen. However, the technology I invented for mixing rubber powder with bitumen does not use perfume oils; instead, it provides the conditions to break the rubber network structure and revive the sulfur bonds, thereby increasing the elasticity properties of bitumen. It has deployed rubber granules asphalt flexibility.

A paper titled "Investigation of the viscosity behavior of VB bitumen modified with rubber powder" was presented by Dr. Nader Tabatabai and Mrs. Zahra Kamali Abianeh at the Bitumen and Asphalt Institute of Iran in the Faculty of Civil Engineering at Sharif University.

In this paper, the maximum amount of rubber powder that can be added to bitumen is 15% relative to the total weight of bitumen. The tests performed on this product indicate a limited increase in the rheological properties of bitumen. In my invention, however, up to more than one time, the initial weight of bitumen can be added to rubber powder. As the results of the tests show, the rheological properties of bitumen and asphalt have increased significantly, leading to a decrease in bitumen consumption in the production of asphalt. Moreover, as the conditions for breaking the network structure of rubber are present and the sulfur bonds are revived, the elastic properties of bitumen increase. Rubber granules have also been utilized for asphalt flexibility.

Technical Problem

Giving priority to sensitive users such as cyclists, the importance of public transportation, and reducing dependence on private cars and air pollution are only part of the fundamental issues in keeping up with the developments based on the principles of sustainable development. A property that affects cycling comfort is paying attention to the quality of the pavement. The severe weakness of cyclists in accidents and the possibility of body parts fracture due to collision with the hard surfaces of the pavement are essential factors in declining the safety of cyclists. Although the significance of asphalt flexibility in bike lanes is clear, the need for suitable bitumen to make resistant asphalt with highly elastic properties in the road construction industry has made experts use asphalt sand or fine-grained asphalts. In conventional methods, rubber powder is added to bitumen and asphalt to increase flexibility of asphalt. Bitumen is physically mixed with rubber, and the rubber particles are placed only as fillers in the structure of bitumen and asphalt. The use of small rubber particles in bitumen and asphalt cannot raise the elasticity of asphalt to a large extent. In contrast, using large rubber particles in the structure of bitumen and asphalt (to increase elasticity) causes the asphalt to lack strength and disintegrate. The purpose of this invention is to simultaneously use fine and coarse rubber particles in the asphalt structure and provide the necessary conditions for the interaction of bitumen with rubber to produce asphalt with high elasticity and the proper strength.

Solution to Problem

The claimed invention is “Ultra-Elastic Rubber Asphalt by Polymerization Method and the Symmetry Technique” which is comprised of the following:

Rubber powder (20%), pure bitumen (75%), carbon black (5%), sulfur (1%), zinc oxide (1%), fine-grained stone materials as per the asphalt mix design (70% to 90%), rubber granules with dimensions of 3-5 mm (10% to 30%) and chemical supplement (sulfur and zinc oxide) (1%).

As an elastomer, rubber powder in asphalt, as well as having a positive effect on the environment and economy, significantly improves the mechanical and rheological properties of bitumen and asphalt. Rubber powder increases the strength and elastic properties (recoverable deformation) within the operating range of the temperature. It also lowers the temperature sensitivity of the pavement and enhances the resistance to asphalt rutting and fatigue. Additionally, lower maintenance and repair costs, less noise, and higher braking resistance are the advantages of rubber asphalt compared to regular asphalt. According to scientific experiments and field research results worldwide, there are two conventional processes for adding rubber particles to bitumen or asphalt.

1. The dry process: rubber is directly added to the asphalt mixture.

2. The wet process: first, rubber powder is added to bitumen and mixed with it by high-shear mixers, then rubber-modified bitumen with stone materials is added, and the asphalt mixture is made.

In this invention, combining the dry and wet processes to add rubber powder to bitumen and rubber granules directly to asphalt eliminated the weaknesses of each of the previous methods. That enabled us to produce a wholly sticky and elastic bitumen capable of effectively interacting with stone materials and rubber granules. We arrived at a composite pavement (strength, cohesion, and flexibility) with load capacity and resistance against deformation due to the passing of light vehicles, along with improved surface characteristics and ease of pavement maintenance and repair.

In order to produce this type of flexible asphalt, which is a combination of the dry and wet processes, rubber powder must be added to bitumen (wet process), and rubber granules must be added to asphalt (dry process), which is called the “symmetry technique.” Using pure bitumen, polymer-modified bitumen, or conventional rubber powder bitumen is unsuitable due to the lack of necessary adhesion. Employing bitumen with high viscoelastic properties and the ability to interact effectively with stone materials and rubber granules is necessary. Otherwise, there is a possibility of asphalt deterioration and reduced compressive strength.

The invented solution to resolve the above problems is mixing rubber powder with bitumen in the presence of carbon black at a temperature of 170 °C for 4 hours. At 170 °C, carbon black causes the gradual breaking of the rubber network structure; thereby, the maltenes part of the bitumen can penetrate the Di-en structure of the rubber and cause the rubber powder to swell. This method's addition of rubber powder to bitumen produces a homogeneous compound with adhesion and elasticity properties and the ability to polymerize. ( )

After the rubber network structure is broken and transverse sulfur bonds are opened, the rubber turns into a hydrocarbon with free Di-en chains. The wet process of mixing bitumen with rubber powder is applied at this stage.

Next, by mixing this compound with fine-grained stone materials and adding rubber granules to the above asphalt mixture (the dry process) in the presence of 1% sulfur and zinc oxide (ZnO) at 160 °C, the situation is ripe for repeated and gradual vulcanization reaction of natural rubber (Di-en rubber chains) in bitumen. This chemical reaction is the polymerization process.

Adding chemical supplements (sulfur and zinc oxide) to the prepared compound and mixing them with stone materials according to the asphalt mix design, and adding rubber granules to the above mixture, prepares the ground for a gradual and controlled vulcanization reaction in asphalt. After covering the roads with asphalt, rubber asphalt with super-elastic properties by polymerization method and symmetry technique is made ( ).

The polymerization ability in this type of super-elastic asphalt is the re-formation of the chemical structure of rubber in bitumen after mixing with stone materials and rubber granules. Employing this technology established a more effective connection between bitumen, stone materials, and rubber crumb. It made a suitable substrate for holding stone materials and rubber granules together, creating a resistant, coherent, and flexible pavement layer to produce super-elastic asphalts.

In this invention, by using a type of bitumen with polymerization ability, high viscoelastic properties, fine-grained stone materials, adding rubber granules to the asphalt mixture directly, and the simultaneous use of the advantages of the wet and dry processes for mixing rubber crumb with bitumen and asphalt, we were able to present a suitable asphalt mixture for making resistant, coherent and flexible asphalt for bike lanes or sidewalks.

Advantageous Effects of Invention

Among the notable significant features of this project, the following are most notable:

1- Increased asphalt elasticity, which:

A) Reduces the possibility of injury to the cyclist in an accident

B) Makes asphalt reversible (asphalt shape memory capability)

C) Makes it possible to use this asphalt in stadiums and schools

2- Lessening the possibility of a slippery asphalt surface

3- Reducing chances of asphalt surface freezing

4- Lowering traffic noise

5- Helping to remove environmental pollutants due to the use of worn tires

Fig.1

the process of compound production with adhesion and elasticity.

Fig.2

the process of producing super-elastic rubber asphalt by polymerization method and symmetry technique.

Fig.2

[Table 1] the granulation table.

Ultra-elastic rubber asphalt by polymerization method and symmetry technique can be applied in bike lanes, sidewalks, or the floor of schoolyards to improve safety in the event of accidents. For this purpose, using fine-grained stone materials, based on the Iran Highway Asphalt Paving Code Number 234 (IHAP Code 234) issued by the Ministry of Roads and Urban Development, and SBR granules, 12 600-gram samples of super-elastic asphalt were made in a 4-inch mold. The granules properties of this flexible asphalt are mentioned in ( ) (Table 1).

First, stone materials with maximum dimensions of 12 mm were obtained from an asphalt mixing plant to make this flexible asphalt. After separating the stone materials by standard mesh sieves, 600-gram samples of the stone material mixture and 10, 20 and 30 percent rubber granules, as in ( ) (Table1), were prepared. Then each of the mixed stone materials samples (without rubber granules) was placed in an oven at a temperature of 170 °C for 24 hours. The special bitumen with polymerization ability was heated up to 160 °C, and 1% sulfur and zinc oxide (ZnO) were added. After that, hot stone materials (170 °C), prepared bitumen (160 °C), and rubber granules were added to each other, and when fully mixed, the produced asphalt sample was poured into a standard 4-inch mold and compacted with a Marshall Compactor Hammer (75 blows to each side).

Asphalts based on the ( ) (Table 1) have elastic properties. However, the degree of flexibility of the produced asphalts varies proportionally to the percentage of added rubber granules and the percentage of granulation of stone materials.

The invention of ultra-elastic rubber asphalt by polymerization method and symmetry technique can efficiently reduce the injuries of cyclists or pedestrians during an accident. Also, moving bicycles on resistant and flexible asphalt can result in a quiet, low-noise, and safe trip for cyclists. This asphalt is designed for light-traffic routes, such as bike lanes, sidewalks, and schoolyard floors.

Claims

The claimed invention is "Ultra-Elastic Rubber Asphalt by Polymerization Method and the Symmetry Technique" and consists of rubber powder (20%), pure bitumen (75%), carbon black (5%), fine-grained stone materials as per the asphalt mix design (70% to 90%), rubber granules with dimensions of 3 to 5 mm (10% to 30%), and chemical supplements, including sulfur and ZnO (1%).
The production method is as follows:
First, bitumen is mixed with the rubber powder in the presence of carbon black using the "wet process", and a compound with polymerization capability is produced. Next, this compound is mixed with fine-grained stone materials and rubber granules (dry process) in the presence of 1% sulfur and ZnO at a temperature of 160 °C, creating favorable conditions for making chemical bonds (sulfur cross-links in Di-en chains of rubber in bitumen). This is chemical reaction is the polymerization process. These compounds provide the conditions required for a gradual and controlled vulcanization reaction in asphalt.
According to claim 1, rubber granules with dimensions of 3 to 5 mm have been used.
According to claim 1, sulfur and ZnO have been used for the polymerization process in asphalt.
According to claim 1, mixing these compounds and the simultaneous mixing of rubber powder with bitumen (the wet process) and adding rubber granules to asphalt (the dry process), i. e. applying the "symmetry technique" will produce a consistent asphalt with elastic properties.