- Production process
- Mixing and compaction of bituminous mix
- Aging and
- Mechanical response of bituminous mix.
BackgroudIndia has the second largest road network in the world measuring about 3.3 million km length in 2011 (NHAI, 2012). This includes unpaved and paved roads. In terms of density of paved roads this accounts for 0.07 km per 1000 people. Considerable financial outlay is earmarked by the country in constructing or improving the existing road network.
Most of the road construction in India involves the use of bituminous materials and it is important to understand the challenges involved in design, construction and maintenance of such structures. A typical cross-section of a bituminous pavement is shown in Figure 1. The precise thickness and the quality of the material to be used depend on the estimated traffic (normally specified in terms of repetitions of standard axle load) and the strength of the existing subgrade. Generally, the top two layers of pavements are laid with bituminous mixtures and the performance of these layers are directly related to the grade and percentage of bitumen used. The percentage of bitumen used varies from 5 to 7% and this is determined by the mix design procedures. Considerable improvement in pavement performance can be achieved by selecting the appropriate grade of binder to be used in pavement construction. Depending upon the importance of the pavement to be constructed, modified bitumen is used instead of unmodified one. A wide variety of modifiers exists and the most important ones are polymers (elastomer/plastomer) and crumb-rubber. While modified binders have different design and construction issues, most of the aspects discussed in this article are applicable to both unmodified and modified binders.
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