Rubber asphalt production process and processing equipment

Abstract Introduces the definition and manufacturing process of rubber asphalt, analyzes the rubber asphalt production process, processing equipment and key technologies, showing that rubber asphalt technology is a mature application technology.

Keywords rubber asphalt; production process; processing equipment; key technology

Rubber crumb processed from waste tires, its main chemical composition is natural rubber and synthetic rubber (such as styrene butadiene rubber, butyl rubber, polybutadiene rubber), in addition to sulfur, carbon black, silicon oxide, iron oxide, calcium oxide and other additives components. These components are good asphalt modifiers, added to asphalt can improve the asphalt of high and low temperature performance, anti-aging properties and anti-fatigue properties, and play a role in thinning the pavement, extending the service life of the pavement, delaying the reflection of the cracks, reduce noise and so on. Scrap tire rubber chips for asphalt modification, this modified asphalt mixture production process is simple, low cost, not only to improve the quality of pavement, but also on the waste rubber can be large capacity.

1.Definition of rubber asphalt

Asphalt rubber refers to the grinding of fine waste tire rubber powder (according to 0 ~ 2mm gradation) and asphalt (some mixed with a certain percentage of additives) mixed at a certain ratio, and in the role of high temperature mixing made of adhesive materials collectively. The amount of waste tire rubber powder is not less than 15% (internal mixing) or 17.6% (external mixing).

Rubber crumb to join the asphalt mixture processing method there are two kinds: one for the dry mixing method, that is, the waste tire rubber powder and asphalt, minerals together put into the mixing building mixing, the production of rubberized asphalt mixture; another for the wet mixing method, that is, the waste tire rubber powder and asphalt first processed into rubberized asphalt, and then with the minerals and mixing, rubberized asphalt mixture. A large number of tests have proved that the rubberized asphalt mixture is the ideal production method is wet mixing method, that is, McDonald wet processing method. The most important feature of this method is more than dry mixing method of a high-temperature reaction process, that is, the rubber crumb and ordinary asphalt according to a certain proportion of uniform mixing, and will be stirred asphalt, rubber crumb mixture into the high-temperature kettle, so that the rubber crumb and asphalt reaction and stirring for a certain period of time, and ultimately made into a qualified rubberized asphalt modified binder.

2.rubber asphalt production process

2.1 Rubber asphalt production technology

The following rubber asphalt is strictly in accordance with the wet processing method of rubber asphalt binder, its additives, material formulations, production processes, special equipment and construction methods constitute a complete set of rubber asphalt technology. Most of the current international countries and regions have their own rubberized asphalt technical guidelines and standards, which are more mature in the United States, Arizona, California, Texas, Florida, as well as Australia, South Africa, the relevant technical standards.

Asphalt rubber has four major technical indicators: viscosity, needle penetration, softening point and elastic recovery, which should vary according to the regional climate, and the technical standards in literature [1] should be referred to for specifics.

Rubber crumb production is generally used in the waste tire crushing method at room temperature, crushed rubber powder after sieving and removal of non-rubber components according to different particle size ratios. In order to improve the use of performance, rubber crumbs can also be added to the appropriate external dopant; to prevent the rubber crumbs stick together, calcium carbonate or talcum powder can be added, but the dosage can not be more than 3% of the mass of rubber crumbs. Rubber crumb should also meet the corresponding physical and chemical indicators.

Finished rubber asphalt viscosity index in addition to the rubber crumb ratio, but also with the reaction time and reaction temperature has a great relationship. From the test curve can be seen, with the change of reaction time, the viscosity of asphalt rubber at a certain time is a significant increase, and then reduced until relatively stable. At 190 ℃ ~ 210 ℃ reaction, viscosity in a relatively short period of time can reach the maximum value.

The matrix asphalt used must comply with the provisions of the asphalt grade selection according to the national and regional discretion. Matrix asphalt should also be used according to the different construction areas of the climatic conditions for the corresponding choice, the cold areas generally choose 110 # or 90 # matrix asphalt, temperature areas generally choose 90 # or 70 # matrix asphalt, hot areas choose 70 # or 50 # matrix asphalt.

Due to the rubber asphalt binder in the high temperature environment will continue to dissolve, decomposition, in principle, should be used within 24h finished rubber asphalt, such as the need for temporary storage, the rubber asphalt temperature should be lowered to 145 ℃ ~ 155 ℃ range, the storage time is generally not more than 3 d. When the temperature drops below 190 ℃ need to be re-heated, only allows two re-heating cycle (1 re-heating cycle is defined as any time), and the rubber asphalt binder will not be used for any other purpose. , the rubberized asphalt binder is cooled and then reheated to 190℃~210℃). The rubberized asphalt binder must meet all technical specifications. To maintain the viscosity at the specified level, it is necessary to add some rubber crumbs (limited to not less than 10% of the total weight) to the mix when heating and reacting for 45-60 min at 190°C~210°C.

2.2 Rubber asphalt production process

Rubber asphalt is processed by specialized rubber asphalt equipment, rubber asphalt production process with the production scale, process conditions and design ideas vary, but the basic principles of the production process is the same. Its main production process is shown in Figure 2.

(1) in order to improve production efficiency and prevent asphalt aging, will be lower than 17 ℃ matrix asphalt through the rapid heating device to 210 ℃ or so. 2) matrix asphalt through the asphalt flowmeter measurement added to the mixing device. 3) rubber crumb after weighing device weighing the proportions of the simultaneous delivery to the mixing device. 4) rubber crumb and matrix asphalt in the mixing device by high-speed mixing, shear, mixing. 5) Mixing The homogeneous mixture through a special rubber asphalt pump input to the reactor. 6) The mixture in the reactor stirring, insulation (190 ℃ ~ 210 ℃) and dissolved about 40 ~ 60min. 7) The qualified rubber asphalt binder into the finished product storage tank or directly transported to the asphalt mixing plant.

3.Rubber asphalt processing equipment and key technologies

Classification and characteristics of processing equipment. Rubber asphalt processing equipment can be divided into continuous and batch type according to the production process. Intermittent process is characterized by: rubber crumb and asphalt measured in batches into the rubber asphalt mixing device for mixing, mixing and mixing of the mixture into the kettle, followed by the next batch of material mixing, the formation of the cycle of the cycle of operations. Continuous rubber asphalt processing plant process is characterized by: rubber crumb and asphalt continuous measurement and continuous into the rubber asphalt mixing device for mixing, mixing and good finished product from the mixing device into the reaction kettle.

Rubber asphalt processing equipment can be divided into fixed and mobile according to mobility. Fixed is characterized by: the equipment of the independent device can be divided into several flatbed trucks on the transport, in the site according to a fixed position, only a small amount of installation works can be put into production, but this way to move the site is relatively inconvenient. This type of equipment is generally motor-driven, the site needs to have a certain power supply. Mobile is characterized by: equipment installed in the tractor chassis, with the tractor head hooked up to the transfer site transportation. This type of equipment is generally self-powered, driven by an internal combustion engine.

Although the structural form of rubber asphalt processing equipment is different, but the basic composition should include the following parts: substrate asphalt rapid warming device, rubber crumb feeding device, mixing device, reaction kettle, finished product storage tanks and electronic control operation room. The work of each device is connected to each other through the asphalt pipeline.

Equipment pipeline connection, in order to improve productivity can be used 2 ~ 3 kettle parallel alternating work, but also consider the pipeline connection can achieve the following functions.

(1) the matrix asphalt measurement and delivery to the mixing device.

2) the mixing device in the rubber asphalt mixture into the reactor.

3) the mixture in the reaction kettle reaction, so that it is a small circular flow, in order to uniformly mix.

4) Qualified finished rubber asphalt binder by the reactor output to the asphalt mixing plant or rubber asphalt storage tanks.

5) the reactor is directly connected to the mixing plant, the excess rubber asphalt mixture

6) multiple reactor parallel alternating work, the tanks of the mixture can be in and out of each other, without affecting.

7) for rubber asphalt sprinkler and other peripheral equipment to add aged rubber asphalt mixture.

8) when the reactor mix viscosity is too low need to add further rubber crumb, the reactor rubber asphalt binder can be reversed into the mixing device and metering.

9) when the reaction kettle When the viscosity of the mixture is too high need to add matrix asphalt, heated matrix asphalt can be input to the reactor.

10) After the construction, asphalt mixing plant pipeline mixture can be pumped back to the reactor.

11) When the mixing device of the rubber asphalt pump can not work properly, through the reactor asphalt pump will be mixed in the mixing device of the mixture sucked into the reactor.

12) Any reactor rubber asphalt mixture can be input

13) The rubberized asphalt mixture in any reactor can be input, output to another reactor.

In China there has been quite mature rubber asphalt production equipment, like Feiteng Road Construction Equipment Co., Ltd. specializes in the production of asphalt production equipment for fifteen years, with a comprehensive R & D design department, and after-sales management, is China's leading asphalt equipment manufacturers, its development of rubber, modified asphalt production equipment is a self-heating multi-functional asphalt batching production equipment. The equipment is suitable for all kinds of rubber powder modified asphalt, SBS modified asphalt preparation production, development, storage.

The equipment mainly consists of tank (including insulation), heating system, asphalt temperature automatic control system, rubber powder feeding system, matrix asphalt injection port, finished product pumping system, weighing and measuring system, stirring and mixing system, electrical control system, control room and other components.

This rubber asphalt production equipment itself has a strong heating capacity and strong mixing capacity; rubber powder screw feeder, convenient rubber powder feeding additive; with liquid raw materials into the tank function; with weighing and measuring function, can be convenient to grasp the proportion of dosage. With a finished product pump out function; can meet the site without thermal oil boiler in the case of rubber modified asphalt, SBS modified asphalt and other production preparation and storage needs.

4. Advantages of rubber asphalt

(1) high-temperature viscosity, high softening point, strong deformation resistance, can effectively prevent rutting in the long uphill section.

(2) low-temperature modulus of strength is small, low tensile stress, can prevent low-temperature cracks in high sea level areas.

3）Stress-absorbing layer has strong interlayer adhesion, which can prevent the shear nudging of bridge deck in long downhill section.

(4) It has strong elasticity and stress absorption function, which can prevent the reflection cracks of bridge deck pavement and water-stabilized base layer.

5）It has excellent fatigue strength, which can thin the thickness of the road surface and at the same time extend the

A large number of successful construction cases show that rubberized asphalt can be widely used in cement road overlay, new roads, old asphalt pavement repair, bridge deck pavement and other projects. Its cost-effective far better than other modified asphalt, in the construction investment, maintenance costs are lower than other modified asphalt, rubberized asphalt pavement at the same time, the service life of road performance also has obvious advantages.