“In Mumbai, the cement concrete roads built 20 years ago are still in a good shape. All the roads in the country would be
converted into cement concrete ones. And I guarantee that they will last for 200 years,” Nitin Gadkari
Road infrastructure plays an important role in a country’s development. There are two major types of materials widely used in road
construction, namely concrete and bitumen. Concrete roads require low maintenance expenditure.They are impervious to water and
to the ill effects of oil and lubricant spillage. Bitumen is a by-product of the petroleum refining industry.
It is proven that the resistance of bitumen surfaces and their strength deteriorates rapidly under the influence of aggressive climate and usage conditions.
On purely techno-economic considerations, concrete roads have proved to be far superior as compared to bitumen roads.
In many European countries, notably Germany, France, Austria, Belgium, Netherlands and Switzerland, concrete roads were built on a considerable length of the most heavily trafficked routes. In the USA, nearly 60 percent of the interstate highway system was built in concrete. Most road networks in the
EU was developed from a national viewpoint. The aim of the Trans- European Transport Network (TEN) is to build a transport network that
would facilitate the flow of goods and people between EU countries.
The TEN is set to encompass 90000 km of motorway and high-quality roads by 2020. The EU will eventually have a role in the safety
management of the roads belonging to TEN through safety audits at the design stage and regular safety inspections of the network as for many European countries rural road
fatalities account for the highest proportion of road deaths. Cement concrete pavements in Belgium have comprised a major portion (Over 70 percent) of the rural land
reallocation projects in Belgium since 1958. The initial choice was based on the good performance of this type of pavement on state and secondary roads in the 1930s. Apart
from this criterion, the selection of the type of pavement can also be influenced by the way construction projects are subsidized. In this regard, the selection of concrete
structures are favored by financing structures that subsidize all or a portion of the investment costs for pavements except maintenance, which is often the responsibility of
local organizations. India’s road infrastructure has seen consistent improvement in the last few years. Connectivity has improved and road transportation has become a focus
of rapid development. Roads are providing better access to services, ease of transportation and freedom of movement to people. Recognising the significance of a reliable and
swift road network in the country and the role it plays in influencing its economic development, the Ministry of Road Transport and Highways (MORTH) has taken up
the responsibility of building quality roads and highways across the country.
Global Scenario Recognising the need to foster competition and thereby ensure economical options, many European countries and USA have made it compulsory when
calling for road-building tenders, to invite bids on both flexible and concrete specifications. In such cases, concrete roads scored over bituminous roads in several instances.
The wide acceptability of concrete as a road pavement material is mainly due to certain principal advantages it scores over bituminous material. The USA is often cited as the
benchmark for rigid pavements.Concrete roads were first built in the US a century ago, beginning with a six-mile stretch. That multiplied to 11,000 miles in 20 years. It is
interesting to note that in the USA, 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. Concrete roads make up more than half their roads.
In the Netherlands as well, motorways and/or freeways are controlled access highways for fast motor vehicles only and are consistently built with multiple carriageways,
guard rails, and interchanges with overpasses. Realising the loss of thousands of crores of rupees to the economy due to bitumen roads, which develop potholes and become
unserviceable particularly after rains, the government of India has been providing the major thrust to the construction of durable and longlasting highways, urban and rural
roads. Several schemes such as NHDP, PMGSY, and JNNURM have been launched to achieve this goal.
For the XII plan, the government has earmarked one trillion dollars for the infrastructure development of the country, a large chunk of this would be spent in the construction
of roads and highways. Road Infrastructure in India India’s preferred road-laying material has for long been bitumen. However, a few of the National Highways have concrete roads
too. In some locations, such as in Kanpur, British-built concrete roads are still in use. Concrete roads are durable, weather-proof and require lower maintenance compared
to bituminous roads. Moreover, new concrete technology has developed such as cool pavement, quick pavement and permeable pavement, which has rendered it more attractive and eco-friendly. Just one glance at Mumbai’s most famous landmark Marine Drive will amply demonstrate the durability and resilience of concrete roads.
Mumbai residents will scarcely remember a single day when Marine Drive was closed for repairs or maintenance, unlike other bituminous roads. Even after seven decades of its construction, this seafront arterial road shows few signs of distress as compared to much newer stretches built in recent years.
Union Transport Minister, Nitin Gadkari recently said that all the roads in the country would be converted into cement-concrete ones to ensure their stability and durability. “In Mumbai, the cement concrete roads built 20 years ago are still in a good shape. All the roads in the country would be converted into cement concrete ones. And I guarantee that they will last for 200 years,” he said. India’s development agenda for the 21st century cries out for the new impetus to rapid advancements and progress in building roads which are so vital to our economy.
The construction of roads has demonstrated that it can be a major development activity and quite literally the road to economic success. India is now, hence, quickly accepting and implementing traffic technology solutions in creating safer and durable ways for transport.
There have been rapid advances in concrete technology during the past three decades or so. The improvement in strength and other structural properties achieved earlier through the use of steel reinforcement are now accepted as routine and the reinforced cement concrete and prestressed concrete have become conventional materials. Later work led to the development of a variety of concretes in the form of, among others, fibre reinforced concrete, polymer concrete, Ferrocement, sulphur concrete, lightweight aggregate concrete, autoclaved cellular concrete, high-density concrete, ready-mixed concrete, self-compacting concrete, roller compacted concrete, high strength concrete, super high-strength concrete, high performance concrete, high-volume fly ash concrete, self-curing concrete, floating concrete and smart concrete. Some of these concretes are briefly discussed here:
Fibre Reinforced Concrete Different types of mineral, organic and metallic fibers have been used.Among the mineral fibers, use of asbestos in the production of asbestos cement products is well
known. Since water absorption of the asbestos fiber is high, its use in concrete increases water requirement. Consequently, there is a reduction in strength of the concrete. Organic fibers such as coir,
jute, rayon, and polyester are attacked by the highly alkaline condition in concrete. As a result, concrete containing these fibers loses strength with time. Other organic fibers namely, nylon,
polypropylene, and polyethylene are alkali-resistant. But, due to their lower modulus of elasticity, the incorporation of these fibers do not increase strength. Concrete containing nylon or polypropylene fibers, however, is reported to develop higher impact resistance. Virgin Poly-Propylene fibers of structural grades, such as Forta Ferro Fibres, having high strength and modulus of elasticity are now available from FORTA Corpn USA. These are being extensively used all over world for Pavement/highways/Runway construction, Fibre shot creation of tunnels, Repair and
Rehab jobs and Bridge deck construction incl India. Among all fibers, the use of steel fiber in concrete has received far greater attention, in the past but because of the corrosion problem structural grade polypropylene and other synth fibers are taking over now. The compressive strength, tensile strength, fatigue strength, modulus of elasticity, abrasion resistance, skid resistance and thermal conductivity of steel fiber reinforced concrete has been found to be slightly higher than the corresponding plain concrete. While creep and shrinkage are more or
less unaffected, there is over 100 percent increase in the flexural strength and impact toughness of plain concrete when reinforced with steel fiber. At the same fiber content, use of a blend of fibers having the different aspect ratio, in place of single aspect ratio fiber, gives greater structural benefits. It has also been found more beneficial as well as economical to use steel fibers only in the tensile zone of the flexural member. Unlike plain concrete, steel, fiber reinforced concrete is not brittle and offers far greater resistance to cracking. The fibers act as crack arrestors and restrict the growth of flaws in concrete from enlarging under stress into visible cracks. The ultimate failure is reached only when some of the fibers get pulled out of the matrix. As compared to plain
concrete, the resistance of steel fiber reinforced concrete to thermal shock and heat spalling is also far superior.
The major applications of steel fiber reinforced concrete are in pavements (both for new construction and overlays), precast concrete units, concrete reactor pressure vessels, blast resistant structures, machine foundations, tunnel linings and structures requiring resistance to thermal shocks, such as refractory linings. Polymer Concrete Depending upon the method of monomer incorporation into the concrete, the polymer concrete is termed as: polymer impregnated concrete, when dried precast concrete is impregnated with monomer and polymerized in-situ, polymer cement concrete, when cement, aggregate, water, and monomer are mixed together and polymerized after laying and, polymer concrete, when aggregate and monomer are mixed together
and polymerized after laying. A number of factors such as distance to be penetrated, degree of drying, total porosity and pore size in concrete, monomer viscosity, whether or not vacuum
and/or pressure is applied, influence the extent of monomer filling in polymer impregnated concrete. The widely used monomers are methyl methacrylate, styrene, acrylonitrile and
chlorostyrene. The monomer polymerization is done either by thermal catalytic process or by radiation As compared to plain concrete, the strength and other properties of polymer concrete is considerably higher. At 6 percent polymer loading, the mechanical properties of polymer impregnated concrete vis-à-vis corresponding plain concrete were found to be as follows:
Compressive strength, 2 to 4 times higher Tensile strength, about 4 times higher Modulus or Elasticity, About 4 times higher Creep and Permeability, Almost Nil With almost nil permeability,
the polymer impregnated concrete has much greater resistance to the attack of acidic and/or sulfate containing waters. Economics permitting, applications of polymer concrete having
good scope are: concrete pipe manufacture, concrete piles, concrete tiles, tunnel supports and linings, precast concrete decks, precast concrete building units for use in aggressive conditions,
desalting structures, lightweight concrete constructions and providing surface protection to cast in-situ concrete. Cement and concrete in road construction and transports The contribution of cement and concrete to transportations and particularly to road construction is considerable. Bridges, tunnels, safety barriers, concrete roads and sound barriers are several examples
of successful cement application. A characteristic of the use of cement in the aforementioned applications is the small maintenance cost together with the elongation of the service life of the structure. In road building, cement is also used for the treatment of aggregates and the stabilization of soils. The production of cement binding mixtures contribute to the upgrade of the
bearing capacity of subgrade along with an increase of the bearing capacity of the pavement layers. This increased bearing capacity provides the ability to construct road surfaces of lesser thickness and thus of a significantly lower cost. Furthermore, based on techno-economic studies developed by highway owner agencies, the use of concrete overlays on existing deteriorated asphalt pavements that have failed due to an increased number of passes or excessive vehicle loads is the solution most favored, in order to extend the freeways lifetime and upgrade their capacity
to current design standards. Concrete pavements Due to their high bearing capacity and increased stiffness, their specific property not to deform under heavy permanent loads, is the reason why concrete pavements are used for: Parking aprons, taxiways and runway takeoff areas in airports Parking grounds for vehicles of heavy weight Heavy duty Industrial floors (vehicles on tracks and military tanks) Floors for handling and storage of containers at ports Industrial floors with high requirements in terms of flatness and durability to abrasion and surface exposure to aggressive attacks (use of toxic materials, welding etc) Bridge decks Road pavements in long tunnels for fire safety reasons, immediate reuse of the road following a fire and better energy consumption during service life (lower intensity lighting required) Pavements at toll stations (resistance to braking and acceleration) Concrete floors form an unrivalled type of paving for highways, roads of heavy traffic and simple rural and urban roads. These floors, apart from their ability to withstand permanent deformations and their high bearing capacity, also enjoy
additional advantages, which render them attractive in an application: A greater degree of safety in driving due to improved visibility. The reason is that obstacles are more visible in concrete roads due to the bright color of the surface in comparison to asphalt road paving Small to insignificant maintenance cost High durability over time Reduced total cost of the floor (service life cost analysis) Insignificant rolling noise Low tire wear Lower overall energy consumption Soil stabilization with cement, cement, and hydrated lime or cement and fly ash Cement can be utilized as well in the construction of pavement layers and for the stabilization of subgrade soil materials with average or small plasticity.
In cases of soil materials with more than average plasticity or in cases of swelling soil materials, a combination of cement and hydrated lime or cement and fly ash can be used with impressive results as far as the improvement of the mechanical properties of these soils is concerned. In all these cases, the durability of the stabilized materials against environmental impacts is substantially higher than that of the non-stabilized material. In this way, considerable savings are achieved due to the reduced thickness of the road pavements, while the environmental advantages are equally important since there is no use of materials transported from elsewhere or use of quarried materials. Construction of this type is widely applied internationally,
although quite limited in our country so far. Recycling of pavements with cement It is a recent successful evolution, for the restoration and/or upgrade of worn out from traffic road
surfaces, with the least possible environmental strain and a very low cost. In these cases, the material of the worn road surface in a depth of approximately 20-35 cm (including the asphalt
layers) is being milled and pulverized in specialized equipment together with water and cement. The above materials are fully blended and spread to form a cement stabilized layer on the
surface of which, one or two asphalt layers are added. With the new recycled road surface, the operating characteristics are restored and the pavement bearing capacity is substantially higher than that of the old one. Using this method, the material that exists on the road surface is used on-site, without the need of transportation to nearby installations or areas of disposal or
transportation of new material. The environmental benefits are obvious. Previous concrete (no fines concrete) Pervious concrete is also known as ‘no fines concrete’. Even though its use as a structural material in Europe, dates as far back as 60 years, previous concrete is becoming very widely used today, in the construction of concrete pavements and slabs on grade under low or normal traffic, pedestrian pavements, parking areas, and landscaping works on grade. Due to its environmentally friendly impact, pervious concrete provides the optimal solution where extensive surface coverage is needed, thereby contributing to the sustainable development of a built area. Its use has been recognized as a Best Management Practice by the Environmental Protection Agency in the U.S., because of the significant contribution pervious concrete has in the reduction of surface contamination and the successful management of stormwater runoff. In the case of a conventional pavement construction the surface runoff leads 90% of the container surface pollutants (oils, hydrocarbons) directly into the sea and the rivers, whilst when using pervious concrete the pollutants are driven instead into the ground, where they are being naturally cleaned through biological degradation. In this way, using pervious concrete for parking lot pavements and city roads provides a direct opportunity to replenish the groundwater table through a process of natural filtering, to provide sustainable planting within paved areas and
to reduce the temperature level in densely populated areas (the heat island effect), since the surface moisture is retained into the soil. Based on in situ measurements, the ambient temperature in parking lots made of pervious concrete is lower than the temperature of similar areas, covered with asphalt. In industrial applications, pervious concrete has been used successfully
for the construction of the floors in greenhouses and industrial dairy farms (places of congregations of live animals such as poultry, pigs, etc.), thereby allowing for self-cleaning technologies of
the floors that lead to improved hygiene conditions of the site. The basic maintenance required by previous concrete floors is the periodic cleaning of the floor with pressurized vacuum steam cleaners, in order to prevent clogging of the voids with organic materials. The absence of large drops in ambient temperature due to frost conditions in Greece makes its use in this climate much more appropriate. From the technical point of view, the mix design of pervious concrete includes cement, limited amounts of water (a W/C ratio of about 0.35 to 0.45), chemical additives and
aggregates having a very narrow gradation (and different maximum aggregate size on a case by case basis) and complete absence of sand. As a result, a concrete with a compressive strength of up to 35 MPa is produced, having a void content of 15-35 percent. The concrete exhibits a continuous porous structure, cavities intercommunicate with each other so as to permit the flow
of surface runoff water through the mass, with a drainage rate up to 700 lt/min/m2. Prior to the application of pervious concrete, a hydraulic design for the stormwater runoff management is required, to collect the surface runoff through a specially designed base which is now required to provide both support of the pavement as well as storage and drainage of the surface water.
The Way forward In India, cement concrete roads were built in isolated locations on national highways, state highways and city roads since early 1950.
In the last decade of the 20th century, few major road projects like Mumbai-Pune Expressway (90Km), Delhi-Mathura (100Km section), Indore bypass road (35Km) etc. were undertaken with concrete pavement. These experiences accelerated the construction of 1600Km concrete road under Golden quadrilateral. Further the advantages of cement concrete road over bitumen road in terms of longer life, less maintenance, good riding quality, better skid resistance, lower life-cycle cost, no effect of rainwater, no effect of spillage of oil, better reflectivity, saving in fuel
consumption, etc. has also lead to a construction of more concrete roads in several parts of India. However, due to higher initial cost and the requirement of higher degree of care in design
and construction, the concrete roads were not preferred over bitumen roads. Now the major road projects are being implemented using modern equipment, there has been substantial confidence and capacity building among the engineers and the contractors in the area of concrete roads. The cost difference between concrete and bitumen roads, which used to be
over 50 percent earlier, has come down from 15 to 25% now. This gap has further come down to 10 from 15 percent due to an adaptation of High Volume Fly Ash Technology in the concrete road.
High Volume Fly Ash (HVFA) concrete was developed nearly two decades ago. In this type of concrete, about 40-60 percent of the Portland cement is replaced by a suitable quality of fly ash for different applications including concrete pavements. HVFA concrete exhibits improved fresh concrete properties and excellent mechanical properties and long-term durability along with
the economy.Good quality HVFA concrete can be produced with the judicious use of cement and superplasticizers for different structural applications with varying percentage of fly ash additions. It can be used successfully in our country with very low life-cycle cost and good performance because fly ash is abundantly available and the temperature is also conducive for better reactivity
of fly ash as compared to countries like Canada and US, where the cold climate is prevailing for most of the year.
“India’s preferred road-laying material has for long been bitumen. However, a few of the National Highways have concrete roads too. ”