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Concrete roads by themselves offer tremendous advantages over conventional bitumen roads in both operational and financial terms, writes Sumit Banerjee, Managing Director, ACC Limited
Indian roads are presently not being built with the right choice of material. The two major types of materials used in road construction in the country are bitumen based roads and those made of concrete. Only a very small share of all roads in the country is made of concrete, despite its superiority on many counts as a medium for road building. Concrete roads by themselves offer tremendous advantages over conventional bitumen roads in both operational and financial terms. These advantages are well known and repeated in every seminar or conference on concrete roads. The most salient of these advantages are durability and relative freedom from maintenance which go to offer substantial long term economies in our cash strapped cities. The cement and concrete industry as well as the machinery and equipment suppliers and road construction agencies are ready to meet all the challenges of helping build world class roads.
RoadsStory continues below 
– national scenario
India’s billion strong population straddles a land area of about 3.3 million sq km. While three fourths of Indians still live in our 600,000 villages, we are urbanising rapidly. The rest of the population lives in cities and towns that comprise five metropolitan cities soon to feature in the world’s list of mega cities, 25 mini metros with a population over one million and 2500 smaller cities and towns with a population of 1 lakh and above.
The country’s road network of almost 3.5 million km comprising both paved and unpaved surfaces is the world’s second largest. This corresponds to a road density of about 106 km of roads per 100 sq km of land area. That marks a colossal leap from the road density of 12 km/100 sq km we had in 1951. But it is abysmally low compared to the density of 200-300 km/100sq km we see in the more developed economies.
Of the 106 km per 100 sq km in India, the surfaced road density is barely 45 and that too of questionable quality. Barring a meagre 2% of the total road length in the country that is made of concrete roads, the remaining vast share is made largely of unbound aggregates surfaced with bitumen or asphalt based wearing courses of varying and inadequate thicknesses.
Bitumen roads
India’s preferred road-laying material has for long been bitumen, a by-product of the petroleum refining industry. The choice was popularised by British engineers, whose familiarity with the macadamised surface led them to deploy the same technology in India. Rigid pavements, however, are not new to this country and were built well before independence. There are numerous instances of concrete roads built in the erstwhile regions of UP, Karnataka, Maharashtra and Andhra Pradesh. For many years thereafter, cement was in scarce supply and the cost considerations were not at all favourable. But that picture has changed very substantially since then with the advent of newer materials, new varieties of cement, new technologies and new road construction equipment.
Bituminous surfaces have major drawbacks intrinsic to the basic choice of this material and the limitations of its usage. This author does not at all seek to belittle bitumen, but it is proven that the resistance of bitumen surfaces and their strength deteriorates rapidly under the influence of aggressive climate and usage conditions.
Potholes are only the earliest and most visible signs of the failure of bitumen roads. We Indians can be very aggressive when it comes to how we use our civic amenities. These roads surrender quickly but surely to attack by water, temperature, oxidation and sunlight, petroleum and lubricant spills and the assault of the harsh wheels of all manner of over-laden vehicles, animal-driven carts, handcarts and leaking tankers. Our roads are subject to more abuse, garbage and refuse than their counterparts in the world’s advanced countries.
The first impact of all these shortcomings is at once on the rapid wear and tear of tyres and wheels, the vehicles themselves and on the fuel consumption of road-bound vehicles.
If these indeed are the tortures that the average roads in India must undergo, then it is clear that Indian roads must be built with a material that suffers none of the shortcomings of bitumen. The material used must be impervious to water, high temperature and harsh weather conditions. It must be able to withstand attack from spillage of petroleum, oil, lubricants and other aggressive pollutants. The material must withstand abrasion, high axle loads, harsh wheels and high traffic densities. But simultaneously the material must also match the benefits of bitumen which are low cost and the facility to undertake stage-wise construction and repair.
Technical studies across the world and in India have shown that concrete roads are best suited to a large country with extreme weather patterns and harsh usage conditions such as ours.
They require low maintenance expenditure, particularly sub-surface, since the structural capacity in rigid pavements is largely ensured by the slab itself. Concrete roads are relatively easier to build today, thanks to new emerging techniques and equipment. They can be built without causing significant damage to the immediate environment. Because they are relatively maintenance-free they eliminate the need for frequent traffic shutdowns disruptions and diversions for subsequent repairs which are necessitated by frequent repairs to flexible pavements. Concrete roads are impervious to water and to the ill effects of oil and lubricant spillage. The surface of concrete roads offers better skid resistance.
Concrete roads can be built independent of variations in sub-grade as it has little influence on the performance of the road. A smoother ride on concrete roads means we can expect economies in fuel consumption. Trials carried out by the Central Road Research Institute have shown that laden goods carriers consume 15-20% less fuel on concrete roads as compared to bituminous ones. It also ensures lower wear and tear for vehicle tires, suspensions, chasses and shock-absorbers. It is estimated that concrete pavements bring down vehicle running costs by 10-15% through better ride quality.
Using the life cycle cost analysis comparison; concrete roads match the cost of flexible pavements within 10 years. Even though the initial cost of concrete roads may be costlier, the cost equation begins to shift in favour of concrete at intervals of 5, 10, and 15 years, when flexible pavements require major facelifts to prolong their useful lives. After 20 years, the life cycle cost of concrete roads becomes cheaper by 10 - 15% compared to bitumen roads. The gap becomes widest at the 20-year interval and beyond. The cost competitiveness of concrete pavements may be further enhanced by the use of fly-ash based blended cements.
Concrete roads enjoy a long life, possibly as long as 40 years and under certain conditions they can be maintenance-free for at least 50 years – which is an invaluable asset for a resource-strapped country like ours. Many concrete roads in India have far outlived their original planned life serving as ample proof of the durability of this kind of road. On purely techno-economic considerations, concrete roads have proved to be far superior as compared to bitumen roads.
Global roads - The big picture
Concrete is the preferred choice of material to build roads in most of the developed world. The US is often cited as the benchmark for rigid pavements. Concrete roads were first built in US a century ago, beginning with a six mile stretch. That multiplied to 11000 miles in 20 years. It is interesting to note that in US, the growth of automobiles is correlated strongly with the growth of concrete roads. Today concrete roads link the country’s west coast on the pacific with the east coast on the Atlantic. In a country where petroleum prices are much cheaper than here in India, it is cement rather than bitumen/asphalt that is the chosen paving material. The case for concrete obviously does not need to be proved in US. Concrete roads make up more than half their roads.
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