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Road Network in India: Highway Construction & Process

All you need to know about Roads, Highways & Expressways in India.

Index

 

A strong infrastructure greatly facilitates economic growth. India being a developing nation the highways sectors plays an important role economic development of a nation. India has the second-largest road network after United States of America. The most common & important modes of infrastructure are roads–highways & expressways. Additionally, growth in vehicles technology has led to a need for roads that can correspond with new age development. We will dive into how India constructs its network of roads–highways, expressways, structures & urban infrastructure.


Types of Roads in India

All road or highway projects are sanctioned by the respective state governments in India. Since 1990s many government initiatives have been placed for the development of road infrastructure in India. As per Ministry of Road Transport & Highways, all NH(National Highways) road projects shall be made of Concrete Roads while Asphalt Roads are recommended for low road traffic areas such as urban roads, rural roads, etc.


We will dive deeper into the materials used as we move into the process of building highway roads.

Roads, however, fall into different categories namely–state highways, national highways, expressways, etc depending not on the material used but the places they connect. The Indian road network is administered by various government authorities, given India's national government. The table below showcases the total length of India's national highway network by type of road and administering authority.


Category

Managing Authority

Length (km)

Expressways

National Expressways Authority of India under Ministry of Road Transport and Highways

2091

National Highways

National Highways Authority of India under Ministry of Road Transport and Highways

151,000

State Highways

Public works department of state/union territory

186,528

Category of Highways

Expressways

An access-controlled road with direct user charges is known as a tollway. Expressways are high-speed toll road that is a four-lane highway or more lanes and are access controlled where entrance and exit are controlled by the use of ramps that are incorporated into the design of the expressway. Most of the existing expressways in India are toll roads. Expressways are a type of Highway in India. The National Highways Authority of India aims to expand the expressway network and plans to add an additional 18,637 km of expressways by 2022 apart from existing national highways.


National Highways

National highways are major road connecting major cities throughout the country and are at-grade roads. National Highways are designated with NH, followed by the highway number. Indian national highways are further classified based on the width of the carriageway of the highway.


The Golden Quadrilateral and North-South and East-West Corridor were major ongoing highways project in India.


National Highways (NH) is classified into a variety of types namely– single lane highway, double lane highway, four-lane highway, six-lane highway, eight-lane highway.


State Highways

State highways are highways connecting major cities throughout a state and are also at-grade roads. They also connect with National Highways (NH) or State Highways of neighbouring states. State Highways are designated with SH, followed by the highway number and preceded by state code. Maharastra is the leading state with a maximum share of State Highways (SH) and ongoing highways project in it.


How are highway roads built?

Highways consist of roads and structures in form of ramps, elevated roads/flyovers within themselves. Depending on the category of the highway they are sanctioned either by the state or central government bodies in India. Ministry of Road Trasport & Highways (MoRTH) run by the Government of India has decided to construct all National Highways as concrete roads. Since they are durable, safer, greener & cheaper when compared on a life cycle basis. There are several steps to road construction depending on the material used. The process also widely varies on the material with which a road is to be built. We will look at different types of roads and their processes.


Concrete Roads

Step 1: Site Clearance

First, the ROW (right of way) is marked for a project which marks the boundary of the highway on either side. Site undergoes C&G (Cleaning & Grubbing) and Encroachment clearing which encompasses clearing of trees, profiling the ground, and clearing of encroached government land by local persons and bodies that fall into the project boundaries so as to ensure construction according to the plan.


MoRTH section 200 states details of site clearance.


MoRTH (5th Revision),Cleaning & Grubbing, Scope: This work shall consist of cutting, removing and disposing of all materials such as trees, bushes, shrubs, stumps, roots, grass, weeds, rubbish, top organic soil, etc. to an average depth of 150 mm in thickness, which in the opinion of the Engineer are unsuitable for incorporation in the works, from the area of road land containing road embankment, drains, cross-drainage structures and such other areas as may be specified on the drawings or by the Engineer. It shall include 18 necessary excavation, backfilling of pits resulting from uprooting of trees and stumps to required compaction, handling, salvaging, and disposal of cleared materials with all leads and lifts. Clearing and grubbing shall be performed in advance of earthwork operations and in accordance with the requirements of these Specifications.
Step 2: Survey Work

Once the site is cleared, survey work begins. Surveyors determine the boundaries of the project. In a highway project, centreline markings are made to create a base on which the construction would take place. To mark a centreline for the highway total station is divided with the help of the provided coordinates.

Following the centreline line mark chainage marking, the project's OGL(original ground level) is recorded. The level of ground provided before the project begins is recorded so as to know the baseline. So that when we fill or cut the road further in the project, we have a baseline to measure the deflection. This also comes in handy during billing contractors. measured is subtracted from FGL (finished ground level) to get the height of the Embankment.



Step 3: Earthworks

Embankment forms the first earth layer on the road. Embankment typically is made between 200-250mm. But may differ according to the FGL & OGL. The embankment is made of soil or stone, built to hold back water, for protection, or to support a road. The embankment layer is followed by the Subgrade layer. The subgrade layer is mainly composed of native soil and may also have aggregates up to 50mm but not exceeding 2/3rds of the layer. During the subgrade layering camber, slope and superelevation are key. For Embankment & subgrade, the tolerance in surface levels is (+/–) 20mm as per MoRTH Rev 5. Once all the material is poured the ground undergoes compaction with the help of a motor grader & roller compactor.

Step 4: Granular Sub-base

Next, a geotextile sheet is laid out on the entire base. This sheet prevents water from the ground to rise up. Above this sheet is the GSB (Granular Sub-Base) is added. GSB is a drainage layer. GSB is compacted till the density achieved is at least 98% of the maximum dry density of the material. The tolerance for the GSB layer is (+/–) 6mm.


Step 5: Dry Lean Concrete

DLC (Dry Lean Concrete) is the next layer added after compaction of the GSB layer. DLC made in the batching plant is carried to the site and laid out with the help of a paver machine. The temperature of DLC is to be maintained from 25-30 deg celsius and must be laid out within 2 hours from leaving the batching plant. The compaction of DLC is done with a double drum vibratory roller. DLC is cured for 7 days before introducing any traffic on the surface.


Step 6: Pavement Quality Concrete

Before PQC (Pavement Quality Concrete) is layered, the surface is cleaned by a dry brush machine & water jet spray. After cleaning a separation membrane is laid on the surface. Various tests like atmosphere data (humidity & wind flow), concrete mix slump test, temperature & density are taken place before & during PQC laying work. The paver then lays the PQC. After the PQC is laid by the paver, the dowel bars are inserted to act as expansion and compression joints. The surface is then smoothened using a floater. To create friction for the moving traffic, the concrete surface is then textured using bristles. PQC is then cured for 28 days before allowing live traffic on it. Meanwhile, the surface undergoes testing.



Asphalt or Bituminous Roads

All though Concrete roads & Asphalt roads have a different process of the build. Step 1 & Step 2 are common among the two. So we will begin from Step 3 in constructing Asphalt roads.



Step 3: Earthworks

A typical bituminous road consists of various layers. The level of road to be achieved is provided by the government in the form of FGL.

After the road is leveled. As in a concrete road, a layer of embankment and subgrade is added. After the Embankment, the subgrade is then layered on top. The height of each layer is in accordance with the given requirement. Embankment and Subgrade together make up the formation layer of the road. The height of each layer is crucial. Any change in the height of the layer can directly affect the compaction of the road. Only once a road is put to use with live traffic the road starts to settle. All the layers are decided to keep in mind the settlement height needed.


Step 4: Subbase or Non-Bituminous Subbase course

Subbase mainly consists of GSB. As the name suggests, this layer is a coarse granulated aggregate. GSB uses aggregates less than 75mm in size. The thickness of this layer is 1:1 with the formation layer. This forms the second layer of the road.


Step 5: Earthen Shoulder

After the GSB layer comes a layer of WMM (Wet Mix Macadam). But before adding in the WMM layer earthen shoulder is built for the road to support and lock the layers. This also ensures optimum usage of WMM by creating a border on the edge making it easier to pour without spillage. These earthen shoulders are built on both sides of the road.



Step 6: Non-butiminius base course

As the name suggests, this layer is a wet mixture of non-bituminous aggregate and soil made with water. The maximum size of aggregate for this layer is 53mm. Since this layer exceeds 200mm in most cases, this mixture is laid out in 2 parts on top of the other.


Step 7: Butiminius surface course

After the base course comes the surface course with bituminous. To begin layering with bitumen, the prime coat is first laid out on the base course. A prime coat is a heated emulsion that is sprayed onto the WMM bed. Following the prime coat is DBM(Dense Bituminous Macadam) which is a mixture of aggregate, dust, lime, and bitumen. These mixed together in a hot mix plant results in DBM which is then poured on the prime coat.

After the DBM is added through a paver, a tack coat is applied to the surface. Tack coat forms an adhesive bond between the tack coat and the next layer of coating. The tack coat prevents slippage and may sometimes function as a more long-term sealer to protect the substrate from moisture and bacteria.

The topmost layer on a bitumen road is the BC (Bituminous Concrete). This layer is composed of aggregate smaller than 19mm and larger than 13mm along with dust, lime, and bitumen. Like DBM, the mix is also created in a hot mix plant.


Concrete Road v/s. Asphalt Road


Concrete Roads

Asphalt Roads

Have a life-cycle of 30-40 years

Have a life-cycle of upto 10 years

Cost 20% expensive during construction but cost 20-25% cheaper when considered on life cycle basis

Cost cheaper to construct than concrete

Do not get highly affected by changes in weather, humidity & temperature.

Are susceptible to higher wear & tear by changing environment

Repairs are difficult, time consuming or expensive.

Repairs are quick and inexpensive.

Curing takes a longer time than Asphalt

Curing takes lesser time hence have quicker project cycles

Are a greener option due to the materials used and longer life

Bitumen is a pollutant hence they contribute highly to pollution during construction & usage.


Summary

There are 3 main categories of highways in India namely; Expressways which are 8 lane high-speed highways that connect 2 or more cities, National Highways commissioned by the Indian government that connects major cities within the nation & State highways that connect cities & towns within the state.


Ministry of Road Transport & Highways (MoRTH) is the apex body for formulation and administration of the rules, regulations, and laws relating to road transport, transport research. MoRTH lays out various standards for materials & processes to increase the mobility and efficiency of the road transport systems in India.


As per MoRTH, all NH & SH must be Concrete Roads while Asphalt roads are recommended only for low traffic roads, like intracity and rural roads. Concrete roads are made of 5 layers; Embankment, Subgrade, GSB, DLC, and PQC. While Asphalt roads are made of 6 layers; Embankment, Subgrade, GSB, WMM, DBM & BC. Concrete roads are rigid pavement roads whereas Asphalt Roads are flexible and are affected by duress, wear & tear, and heat.


The NHAI is responsible for ensuring the execution & practice of the rules and safety requirements in all highway projects as laid forth in MoRTH's circulars and directives for centrally sponsored highway roads. As of 2022, road construction in India has touched a maximum of 37km per day. The Indian government takes major effort and aims at bringing this up to 40km on a per-day basis.


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