Irc.org.in

From the editor’s Desk
CompoSITeS IN CoNSTRuCTIoN oF RoADS AND
Developing Infrastructure and its related systems their identities and properties. In composites, one is integral to the economic and social well being of the materials will be in “Reinforcing phase” of a nation. Such systems affect our daily lives and the other will be in “Matrix phase”. Typically, ranging from the ability to move from one reinforcing material in the form of fibres, sheets location to another to such fundamental issues as or particles are strong with low densities while the the quality of air we breathe and water we drink. matrix is usually a ductile or tough material. The Because these systems are so all-encompassing outcome of this ‘Composition’ is that the newly and complex, they are often taken for granted, formed material has superior properties over its resulting in low levels of maintenance and uneven levels of attention from policy makers Many people do not realize that composites are and technologists alike. The level of capital and probably the most common structural materials in running investment in the nation’s infrastructure the world and have always been an essential part is massive and keeping these assets in usable of their lives. Man’s first use of such composite condition is one of the major challenges facing materials was probably the earth reinforced structures using layers of bamboos and earth. Civil Engineers are known to test the limits of Plywood is another example of Man’s attempts structures, by going higher, longer or lighter. to capture and employ Nature’s inherent wisdom. On the other hand, Civil Engineers are working Third example of a composite material is reinforced against the unpredictable elements of nature like concrete, as is used in the construction of roads water, wind, snow, earthquakes, soft grounds and bridges. Despite the fact that composites etc which at most times are difficult to quantify. are generally more expensive in comparison to Hence, they are perforce very conservative. These traditional construction materials, they have the two professional characteristics come together advantages of being stronger, better resistant to when Civil Engineers are exploring the exciting environmental degradation, have higher strength opportunities offered by the high-tech engineering and other material properties like high temperature materials available to them, today. The challenges resistance, excellent thermal insulation, sound to reduce weight, increase spans, build higher or damping properties etc. The development and slender constructions automatically mean they application of new Advanced Composite Materials must look at new engineering materials in their are among the fastest growing sectors of modern technological endeavours. At the end, these may prove to be cheaper on a life cycle cost analysis. A composite is multiphase material formed from a combination of two or more materials that differ in The decay of steel and concrete in bridges composition or form, bonded together, but retaining entails a huge amount of efforts and money in eDIToRIAl
repair and replacement. Increased service loads, In the construction of roads, when dealing with traffic volumes, changes in use, deteriorated difficult sites, the conventional practice was reinforcements, errors in design and construction limited to either replacing the unsuitable soils, and structural modifications etc mean that in many or bypassing them with costly deep foundations. cases reinforced concrete structures need to be Additionally, the age-old problems of land scarcity, repaired or re-constructed. External plate bonding need to rebuild ageing infrastructure in urban is being widely used to increase the strength of such areas, increased realization of seismic hazards and under reinforced structures. Literature survey has regulations have given the impetus for evolution revealed that advanced composite material such of a number of ground improvement techniques. as Carbon Fibre Reinforced Plastic (CFRP) strips Innovative ground modification approaches are could be externally bonded to existing structures routinely used, nowadays, to solve unique soil- to strengthen them. This is an economical, speedy related problems and often are considered to and practical solution for extending the service be the most economical means to improve an life of structures. Fibre reinforced plastic has undesirable site condition. Geosynthetics have greater strength capabilities and is less susceptible proven to be amongst the most versatile and cost- to environmental deterioration than steel. Such effective ground modification material.
composites also do not deteriorate in the presence In addition, Civil Engineering today faces of salts, which shorten the life of a conventional challenges that require building reinforced structure near the coasts. Studies have found that fibre reinforced plastic has weight to strength structures which can withstand natural disasters like earthquakes, tsunami and landslides etc. This ratio of 50 times compared to that of concrete requires the creative use of composite materials and 18 times that of steel. This technique has in existing structures and future infrastructure been developed in Switzerland, Canada, USA systems. Composites are now successfully applied and Japan and as a result, it is now possible to in making reinforced concrete structures more replace the heavy steel plates with light carbon earthquake resistant, around the world.
Roads and bridges face problems of cracking, For certain applications, the use of composites rutting, deterioration, corrosion, overloading, rather than metals has in fact resulted in savings traffic jams and partial or complete failure of of both cost and weight. The design of a structural structures etc. It is, therefore, essential to make the component using composites involves both existing structures, as well as new projects to be material and structural design. Unlike conventional envisaged in future, sustainable, durable and long materials e.g., steel, the properties of the composite lasting with use of natural and creative composite material can be designed considering the structural materials. Composite materials have the potential aspects and strength requirements. Composite to be “the civil engineering structural materials properties like stiffness, thermal expansion, etc can be varied continuously over a broad range of values under the control of the designer. The use of composite structural members, deck surfaces and bridge railings can decrease the “dead load” associated with the bridges and allow for reduced (R.p. Indoria)
weight of bridges or increased vehicle-load-

Source: http://irc.org.in/ENU/knowledge/Editorial/February%202010.pdf