👍 (ТулГУ / Обновлённый сайт) Иностранный язык (английский) / 002 / Направление: Промышленное и гражданское строительство / Тема: Ремонт износа (Перевод / Оценка - 84 баллов)

Тема:

РЕМОНТ ИЗНОСА

Направление:

Промышленное и гражданское строительство

Источник:

Лапицкая С.И., Бабушкина О.Н., Ибатулина К.А., Крыжановская А.В. Методические указания по дисциплине «английский язык» Тексты для самостоятельной работы для направления: «270800 Строительство», по профилям: «Промышленное и гражданское строительство», «Экспертиза и управление недвижимостью», «Городское строительство и хозяйство», «Водоснабжение и водоотведение», «Теплогазоснабжение и вентиляция», «Автомобильные дороги и аэродромы», квалификация выпускника: бакалавр, форма обучения: заочная. – Тюмень: РИО ФГБОУ ВПО ТюмГАСУ, 2013

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

ККР зачтена на отлично - 84 баллов (скрин в демо-файлах)

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Если нужна помощь с другими тестами - пишите в личку.

https://studwork.org/info/86802

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Английский текст - ниже:

Repairing the wearing

When an asphalt pavement is reaching the end of its life cycle or is showing early distress, it can be overlaid with a new surface, or it can be recycled using a number of different techniques. Which technique to choose depends on a number of factors, including geographical location, available equipment, road depth, road condition, climate, traffic flow, curb height, quality of existing materials, and the underlying structure.

For example, cold in-place recycling (CIR) is the process of recycling asphalt pavement to produce a rehabilitated pavement. CIR is used to eliminate surface irregularities and ruts and to improve pavement profile and ride quality. Economic and environmental advantages are also realized from recycling existing road materials. The process is performed at the road site and uses many pieces of equipment (tanker trucks, milling machines, crushing / screening units, mixers, pavers, rollers) to recycle 100% of the recycled asphalt pavement (RAP) generated, while hot-in-place recycling (HIR), of which there are a number of processes, involves the heating, softening, scarifying, mixing, and spreading of existing pavements, often with additives to improve or correct deficiencies in the old pavement.

The decision to apply bitumen emulsion is due to the low temperatures during the harsh winters in northern areas. It ensures a higher flexibility of the base course and reduces the possibility of future road damage through cracking. Soil stabilization can specifically modify the properties of wet soils which cannot be sufficiently compacted, in this way producing soils which can be placed and compacted immediately. The soil stabilizers scarify the soil and simultaneously mix in a binding agent, for example cement or lime.

On the new machines, the milling and mixing rotor with its special cutting tool arrangement mixes in the binding agent uniformly across the entire working width. The rotor is driven via the tractor’s power take-off, and mechanical belt drives on both sides of the stabilizers achieve the highest possible efficiency, thus making optimum use of the power of the diesel engine. A crucial advantage of the new soil stabilizers is their height-adjustable, flexible side plates which ‘float’ on the surface and need not be pulled through the soil to be stabilized. In this way, the full power of the engine and the tractor goes into the stabilizing operation. Due to the side plates, the milling and mixing rotor can penetrate the soil down to the full working depth immediately upon setting in. Both stabilizers have a working depth of up to 50 cm, and working widths of 2.16 m (WS 2200) and 2.5 m (WS 2500) respectively.

A scraper blade fitted to the rear of the stabilizers ensures that the mixed material is pre-levelled, and due to their low weight of 3,800 kg and 4,200 kg respectively, the soil stabilizers can be transported quickly from one construction site to the next. They are coupled to the tractor using the standardized three-point mounting, category III in accordance with DIN/ISO 730-1.

Asphalt rubber

Asphalt rubber is a medium that solves the problem of waste tyres and at the same time produces a material that is suitable for highway use. In the US alone it is estimated that each year around 300 million used tyres become available. VSS (Valley Slurry Seal), in conjunction with its sister company International Surfacing Systems (ISS), has been one of the modern innovators of the process, which was developed in the 1960s. They started putting tyre rubber in as a modifier with the liquid asphalt cement. When the tyre rubber is combined with the liquid asphalt cement the end result is asphalt-rubber binder, ideal for rehabilitating worn roadways, increasing longevity of road surfaces, producing added vehicle traction and therefore improving road safety and reducing traffic noise.

Typically, asphalt rubber has a minimum of 15% tyre rubber or crumb rubber modifier (CRM), and the higher this percentage, the more viscous the material, meaning it behaves better in a pavement preservation or construction application, and afterwards, especially when considering long term performance. Tyre rubber contains chemical elements that can affect the quality and behaviour of the final asphalt mix. Scrap tyres are ground up and the steel and fabric removed: what remains is crumb rubber, containing all of the chemicals that tyre manufacturers have created to produce a long wear tyre.

When CRM is mixed with the liquid asphalt cement, at a very high temperature for a certain period of time, the CRM and asphalt cement combination or resulting asphalt rubber binder reacts or interacts, the improved physical properties are achieved. This means that the various asphalt rubber systems that are applied to a road surface contain all the benefits of the tyre rubber and the asphalt, becoming something extra when used as a hot mix paving medium or sprayed on the surface of the roadway for a chip seal application. It is said that asphalt rubber becomes very resistant to ageing, often maintaining a healthy life for over a decade with some asphalt rubber pavement preservation applications still performing after 20 years.

The machines can manufacture asphalt rubber binder materials for chip seals or stress absorbing membrane (SAM), stress-absorbing membrane interlayer (SAMI), and open-graded or gap-graded asphalt concrete, and can also produce other modified binders that have combinations of SBS polymer and CRM as the modifying medium with percentages ranging up to 22%. All these specialized binder materials can be blended in the field at production rates ranging from 15 to 75 tonnes / hr.

During the modified binder production process asphalt moves through the heat exchanger to a high shear blender, and crumb rubber or polymer or a combination of both is conveyed into the asphalt blender. The extender oil tank also feeds the mixing tank if oils are added to the binder. After the material is mixed it goes through the discharge pump into the reaction trailer and material is pumped into one compartment so it can react, while the another compartment supplies the asphalt plant, thus allowing for continuous operation of the plant as one side can be charged while the other is being emptied. The binder is then discharged to the hot mix asphalt plant to combine with the aggregates.

Bitumen advances

In the countries of Western Europe there is an increasing shift away from new highway construction to maintaining and rebuilding existing roads. Highway maintenance techniques do vary between European countries but some commonalities exist. One of the most notable is for surface dressing, which in the past has been regarded as a cheap but comparatively low quality process. Surface dressing techniques have had a reputation for delivering road surfaces with higher than desirable running noise and loose chippings that can cause cracked windscreens (windshields) in an undesirably large number of vehicles.

However, according to John Baxter (UK), consultant director and secretary of the Road Surface Dressing Association, new technology means that surface dressing can now offer a competitive repair option. This is due to the development and widespread use of road binders that exhibit good cohesion and comparatively low temperature susceptibility. Baxter says that in the past as much as 80% of the binders used were of the unmodified cutback type or K170 bitumen emulsion. However he explains that the market has changed and this type has been largely withdrawn from the European market, with up to 80% of binders used now being polymer modified types. This is an important point as polymer modification improves the cohesion of the binders and reduces temperature susceptibility. As a result, the surface dressing performance is significantly improved and the greater cohesion means that chippings will be retained. Meanwhile the improvements in temperature susceptibility mean that the binder will not become brittle in winter weather conditions, further improving chippings retention. In a similar vein, in hot weather the road surface will not soften.

Another key factor for the use of surface dressings has been the development of sophisticated equipment using computer controls to provide a consistent and accurate application rate for the binder. A sufficient and consistent binder thickness is vital to ensure that the chippings are retained. In the past the application rate would be controlled by varying the speed of the tanker, based on the driver's readings of a calibrated speedometer and this led to somewhat haphazard material thicknesses. But the new generation equipment uses a computer to control material delivery by linking the spray bar pump with the vehicle's powertrain to provide a far more accurate flow rate. Proper training practices have also been developed along with quality assurance systems, further helping improve the reliability of surface dressing applications.

Using surface dressing can help seal a pavement and provide sufficient skid resistance, offering an efficient and low cost repair option and as it is a cold process, energy costs are also low. When the surface dressing needs to be removed, conventional cold milling can be used while the recovered material can also be recycled using either foam bitumen processes or through a hot mix plant. Using cold recycling with either foam bitumen or emulsion-based processes with surface dressing also allows early opening of the road to traffic, reducing traffic disruption caused by repairs.

Polymers in road construction

Polymers have for many years been widely used by societies. Back in the year 1500 the Mayan civilization in Central America are assumed to be among the first to find an application for polymers, as their children where fond of playing with a ball made from local rubber trees. Today it is extensively used in our day to day life in various forms. In the construction of buildings it is considered as fundamental. Now it is in the construction of roads. The biggest problem facing government’s today about roads is the cost of building and maintaining them, the time it takes to build them and the amount of natural resources it takes to build them.

The main ingredients in building a properly stabilized road today is cement, lime, various size stone and appropriate soils. Many countries in the world do not have these resources to build roads with, they thus have to either import the raw material, or due to financial constraints, use whatever local resources they have. These local raw materials are often not conducive to a sustainable road and not long after will fail, thereby repeating the sad cycle of reinvestment for the same road. Alternatives have to be found. In this, there have been many studies done worldwide to find modifiers to economically modify the locally available raw materials, from using wood chips, tree gum, waste materials, by-products from steel mills and others. There where even attempts made at using nuclear wastes. All the aforementioned have some or other negative factor, however, there has been significant progress made by using polymers.

Already in Holland a company is using polymer products that alter bitumen to keep the driving surface asphalt pliable. A pilot experimental study of some acrylic polymers was undertaken. Their applicability as stabilizers for soil, with the emphasis on economy, was determined. Selection of the test polymers was based on their suitability for in situ soil stabilization. Polymers currently used in four different industries were evaluated by compression and freeze-thaw tests. In all cases, polymer, stabilized soil specimens, outperformed their unmodified counterparts. The relative economy of this polymer made it competitive with other stabilizing agents. The most frequently used modifier is cement; however cement-soil has low resistance to mechanisms as periodic abrasions and flexibility.

Many other additives have been evaluated as soil stabilizers and the commercial success of these modifiers has varied, with many having limited application due to high unit costs, handling difficulties, minimum soil improvement, undesirable physical properties, or excessive set time. In today’s chemical industry many special polymers have been developed to meet a particular demand. The manufacturers of this product have a 15 year history, which is good for decision makers and investigators alike. A representative from the local European distributors of this polymer, states that although this product is a success as it is, the principal of this product is continuing doing research on polymers. In general more investigation is needed as polymers need to be more aggressive in the use of infrastructure in today’s society. It is a ‘green’ product, easy to use and competitive.