Modifications to improve the properties of the binder and other alternative materials - Студенческий научный форум

XII Международная студенческая научная конференция Студенческий научный форум - 2020

Modifications to improve the properties of the binder and other alternative materials

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Innovation is identified as a very crucial part of the continued growth and development in the construction industry . Innovation in the road construction sector is very beneficial, as it is certain to bring better results, like betterperforming roads with lower adverse environmental impacts and lowered costs and improved quality that would require low maintenance. It has been seen that the adoption of innovative technologies has brought about benefits such as increased share in the market, as well as a better competitive position in the market . In this research, we would look into the adoption of innovative methods in the road construction sector to gain better outcomes that can be visibly seen and easily measured in terms of reduction of costs of maintenance and road rehabilitation and better performance.

Currently in the world undergoing through a large number of road infrastructure development projects. Due to this initiative, fresh attention has been drawn to the issues related to latest road technology. This paper presents some

emerging road materials and innovative application concepts, which appear to be promising for future developments.

Emerging road materials can evolve in two ways as modification of existing road materials and as development of alternative road materials.

Existing materials may require modifications soasto improve their engineering properties. Also, locally available materials, which are otherwise not satisfying general specification requirements, can be suitably modified so that they become acceptable. This also serves the purpose of economy in terms of savings of haulage of costly materials fromelsewhere. Sometimes, design may require special purpose materials having specific properties (for example high or low permeability, enhanced shear strength etc.) which can be achieved through material modifications. Discussion on soil stabilization, ground improvement techniques and advanced cement concrete materials have been kept outside the scope of the present paper.

Analysis of Bitumen Properties during Ageing Using Atomic Force Microscopy.

It is well-known that bituminous materials age during exposure to sunlight, heat and oxygen. This ageing process causes both the properties of the bitumen and the behavior in a typical asphalt mixture to change. Depending on the level of ageing, the bitumen or asphalt may become unsuitable for its intended application. Various methods exist for the analysis and characterization of ageing of bitumens. In this paper a potential alternative method that has not received much attention yet as an ageing characterization method is discussed. The Atomic Force Microscope (AFM) is a device that is used on a daily basis by scientists working specifically in the nanotechnology field. The AFM allows various properties of a sample to be investigated, including the surface morphology. Researchers have investigated the AFM as a method for evaluating properties of bituminous binders. During previous work the author has evaluated the effect of artificial laboratory ageing on the surface morphology of a specific binder. In this paper the general ageing process is summarized and the AFM technique for characterizing the surface morphology of bitumen samples, both neat and treated with TiO2, are discussed. Data from various laboratory aged and field aged samples are presented.

Binder (bitumen) modification.

Binder (bitumen) modification is done with the help of additives which may or may not react chemically with bitumen. Binder modification results improvement of one or more properties of the binder (and hence the mix) viz. fatigue resistance, stiffness modulus, rutting resistance, stripping potential, temperature susceptibility, oxidation potential etc.

For conventional binders, it is generally observed that the mixes with high stiffness modulus (E) show low fatigue life, and vice versa. However, for an economical pavement design, both high elastic modulus as well as high fatigue life is desirable. Through binder modification, thisparticular disadvantage can be avoided.

Industrial and domestic wastes

Industrial and domestic waste products provide a prospective source of alternative materials. These materials are cheaply available. Also, their use in road

constructionprovides an efficient solution to the associated problems of pollution and disposal of these wastes.

Secondary household waste (MSW) after further processing can be used as a fine aggregate in bitumen mixtures. Processing is carried out to remove ferrous and non-ferrous metals and achieve the desired gradation of particle size. Due to the presence of a large proportion of fine ash in solid waste, it is mainly used as a filler. Ash can also be stabilized with Portland cement or lime to obtain a stabilized primary / secondary material.

Other alternative materials.

Extenders, suchas sulphur, may be used as substitute to bitumen . These materials can be used only as a fraction of total bitumen content;hence they

can act as partial substitute only. Use of sulfur in bitumen leads to decrease in overall bitumen, as it acts as an extender. It eventually leads to the decrease in mixing and compaction temperatures, attributable to a decrease in viscosity.

Steel slag aggregate is a good example of syntheticaggregates obtained from by-products of industrial processes. It has good binding properties with bitumen due to its high calcium oxide content. The angular shape of the aggregates helps to form strong interlocking structure. Road pavings with steel slag aggregate showgood skid resistance and mechanical strength able to withstand heavy traffic and surfacewearing. Also, many industrial and other waste products like fly-ash, cement kiln dust, incenerated refuse etc. have been successfully used to produce synthetic aggregates. Mixing bitumen with rubber (natural or crumb form) sometimes poses difficulty. As an alternative approach, tiny crumb rubber pieces can be mixed with aggregates known as dry-process. Research shows improved fatigue performance for this kind of materials, also, this process does not require any modification to the existing batch mixing plant.

Foamed bituminous mix.

Foamed bituminous mix (FBM) is a foamed mixture of air, water and bitumen. It is produced by injecting a very small quantity of water into the hot bitumen, resulting in spontaneous foaming and temporary alteration of the physical properties of the bitumen. Although the foamed bitumen technology was developed more than forty years ago, it is now gaining popularity owing to its present-day standardization, good performance, ease of construction and compatibility with a wide range of aggregate types. Usage of FBM results in reduction in binder content and transportation costs, as it requires less binder and water than other types of cold mixingmethods.

The strength characteristics of FBMs are highly moisture dependent. This is because of the relatively low binder content and high void content of foamed bituminous mixes. Hot bituminous mix are not as temperature susceptible as hot bituminous mix (HBM). Since the larger aggregates are not coated with binder, the friction between the aggregates is maintained at higher temperatures. Foamed bitumen can achieve stiffness comparable to those of cement-treated materials, with the added advantages of flexibility.

Foamed bituminous mix usually lack resistance to abrasion and raveling and are not suitable for wearing/friction course applications. Some specific situations where use of foamed bitumen technology can be considered are:

- а pavement which has been repeatedly patched to the extent that pavement repairs are no longer cost effective;

- granular base too thin to consider using cementitious binders;

- can be effectively used in desert road stabilization.

Relatively high cost, requirement of specific equipment for mix production, sensitivity to aggregate grading and stripping risk are some of the disadvantages with the foamed bituminous mix.

Composite pavement.

Composite pavement can be of two types namely, flexible composite pavement and rigid composite pavement. The flexible composite pavement is comprised of concrete top layer over a flexible (bituminous) base. Similarly, the rigid composite pavement is comprised of bituminous top layer over a rigid base. Composite pavement combines the advantages of flexibility, durability and high strength as given by the two types of conventional individual pavements.

Ultra-thin whitetopping.

Overlaying technique of pavement rehabilitation is well known and widely practiced. However, ultra thin whitetopping (UTW) of concrete over existing

bituminous pavement is a relatively new concept, which is rapidly gaining acceptance. It is better than conventional overlays in terms of cost, construction

time and durability. UTW can be designed for low-speed, low volume traffic areas such as street intersections, aviation taxiways and runways,bus stops and tollbooths. In this technique, a thin layer of high-strength, fiber-reinforced concrete is placed over a clean, milled surface of distressed bituminous concrete pavement to achieve a full or partial bonding. Bonding makes the two layers behave as a monolithic unit and share the load. Due to bonding, the neutral axis in concrete shifts

from the middle of concrete layer towards its bottom. This results in a lowering of stresses at the bottom of concrete layer. Composite behavior of layers affects the

corner stress.

WinterPave asfalt anti-freeze.

Freezing rain, snowfall and black ice are some of the many dangerous winter conditions that plague drivers and pose challenging obstacles for winter maintenance professionals. WinterPave® asphalt anti-freeze is a proven technology developed in Europe that Cargill is rolling out in the U.S. after several years of adaptation, testing and development.

The product is a proprietary additive that gives traditional asphalt anti-icing properties when mixed directly with the product during production. By adding the anti-icing additive directly into the asphalt surface, municipalities, contractors and the public can experience safer winter roads as well as benefit from fewer chlorides released into the environment when compared to traditional methods.

WinterPave asphalt anti-freeze will benefit the public by effectively helping reduce the bond of ice and snow to the pavement, creating safer driving conditions,” said Debby Capela, Cargill Deicing Technology business development manager. “Municipalities, commercial contractors and others who work to keep roads, bridges and parking areas safe for motorists and pedestrians will experience easier plowing conditions.

WinterPave asphalt anti-freeze features and benefits

Mixed directly with asphalt during production for easy installation

Delays formation of slippery conditions caused by snow and ice for easier, faster plowing. Longer margin of time for snowplow drivers to intervene during heavy snowfall. Releases fewer chlorides into the environment.Helps extend pavement life and may help the reduction of potholes.

WinterPave® asphalt anti-freeze helps prevent snowpack and ice from bonding to the pavement at surface temperatures greater than 17 degrees Fahrenheit. This prevents hazardous hard-pack from adhering to the road surface and allows for easier plowing and safer conditions.

Environmental benefits of the product result in a reduced number of sodium chloride applications needed to melt away hard-pack. Once introduced to the asphalt mixture, the WinterPave asphalt anti-freeze product allows for slow and continual release of the anti-icing mixture onto the road surface for concentrated, effective results for keeping the roads clear.

The anti-icing product is incorporated with asphalt during asphalt production, which creates a simple installation process that is the same as installing non-treated asphalt. By adding WinterPave asphalt anti-freeze to asphalt, the additive has no adverse effects on the structural components of the pavement, such as application, performance, durability or skid resistance.

The release of WinterPave asphalt anti-freeze is another step in Cargill’s dedicated path of environmental stewardship and providing innovative solutions for winter maintenance professionals.

Innovative snow melting technologies can be classified using ground source heat pipe , heated fluids with heat pump , and electrical heaters . Among these methods, the heat pipe snow melting system has been regarded as the most environmental friendly method, as the ground heat source is used only which is a clean and renewable energy. The heat pipe snow melting system can transport the heat of the ground soil to pavement surface and melt snow anytime when the ground evaporator is warmer than the condenser imbedded in pavement.

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