Best Professionally Explained Road Construction Process-Read It Now!

 

 

 

The road construction process from base course to paved asphalt concrete:

 

This is a summary of the Step-by-step details of how professional engineers construct diverse types of roads.

The highway construction process is complex and usually involves a team of professionals on a single project.

The team includes infrastructure planners, Highway Engineers, Geo-technical Engineers, landscape architects, project managers, construction workers and highway contractors.

When a new road is being built These professionals combine expertise and their efforts for its success.

 

 

 

In summary, a new highway construction project in an area will principally involve Five (5) key steps:

• Survey the route –before construction and during the road building process to set design points on the pavement structure as shown on the construction drawings.
• Process the earthworks -that makes roads subgrade, base course layers.
• Pavement structure construction– contractors build the pavement layers sectionally, and the construction material is evaluated to assure quality and durability.
• Wearing course surface material paving–This depends on the diverse types of road surface material i.e gravel base material, bituminous material, or concrete slab.
• The road furniture installation –to enhance safety and the road beauty

The construction process on site is usually not as easy as the five-step-by-step summary above.

An enormous number of person-hours go into the planning process, concept design preparation, feasibility studies, project financing, contractor appointment, the actual road building and commissioning for public use.

Before the construction process starts:

 

The developer’s ideas are transformed into a concept during the pre-construction operations, which also results in a basic plan that can be implemented to complete the road construction project.

Design drawings are based on the earliest sketches. All the project deliverables for clients and developers go into these drawings.

All the developer’s stated requirements—also known as the deliverables—are depicted in these illustrations. The sketches are merely preliminary concept ideas at this point.

Two to three adjustments are usually normal after feasibility studies are completed.

Road Planning

 

City planners research trends in urban transportation. Following that, they conduct preliminary desktop traffic survey investigations to identify regions of bottlenecks, high volume, broken road surfaces and traffic flow.

Rerouting traffic through these areas is necessary to reduce congestion.

The survey also gives priority to the interstate links and new road development routes to buildings, hospitals, schools, and churches.

 

feasibility studies

 

Engineers use the preliminary planning data to conduct actual tests on the road site.

Accurate data on traffic volume, Soil types, obstruction on the motorway route, occupied areas etcetera is critical. Once the data is available, the Geotechnical Engineer and other site teams forward the data to the design team.

 

During the construction process.

 

During construction, the appointed project manager coordinates the design and the construction building teams from start to finish. A work schedule will allow highway design to continue concurrently with the road construction on site. If the project is delaying, the contractor has to get more construction workers to accelerate the highway construction process

We explore the two different construction team’s road-building tasks here:

1.      Detailed motorway Design

 The modern motorway design process is governed by road design manuals. The road’s geometry and structure are the main concerns of the design engineer and differ depending on the different types of roads to be built.

Road design factors such as speed, superelevation, crown slope, and typical road cross-section are a function of its geometry.

Structural planning maximizes the capacity of the highways to manage traffic demands. The size of the road layers is determined by the design. A highway engineer designs the following road layers:

 

 

 

i)        Surface wearing Course layer:

 This is the topmost road surface layer visible to pedestrians. It provides a durable, abrasion-resistant surface course that is smooth. Well-proportioned layers of asphalt or hot mixed bitumen are used to make it. Asphalt concrete protects the base material from water ingress and eventual degradation during rainy seasons.

ii)      Base Course layer: 

This layer of the road lies beneath the wearing course. Its essential job is to distribute the strains caused by traffic loads fairly. Gravel is mostly used as a base material.

iii)     Subbase Course layer: 

In terms of load redistribution, it supports the base course and is located immediately below it. This layer usually comprises of a higher grade than the base material as indicated in the road construction specification.

iv)     The subgrade layers:

This layer supports the entire road pavement structure embankment and serves as the foundation of the road. All the traffic loads from the road surface are structurally supported by this layer. The subgrade layer has the highest gravel material grade compared to the base and subbase materials.

 

 

 

 

The present-day road contractors use sophisticated road construction techniques. This involves off-site construction of some parts of the road pavement structure which are later installed on the road while the normal earthworks mixing and compaction progresses for the various road layers

 

Design specifications

 

Highway engineers build Roads according to a certain set of design and specifications guidelines. Countries, regions, or continental areas have their preferred construction systems.

 The American (AASHTO)/European system

The Americans pioneered the modern road design process through the American Association of State Highway and transportation officials (AASHTO).

 AASHTO has slight differences in subgrade and base material and traffic loads specification from the Australian system. Most European countries have a variant national highway design system.

The little variances relate to the diverse types of highway geometry criteria that are used. That also covers material properties for road building, and how each works.

The Asian Pacific system

Additionally, the Asia Pacific countries have a different road design process.

The Asian countries through regional block integrations have global specifications for all the member countries.

 Standing out from the pack, are the Chinese. The Chinese under the belt and road initiative, are interconnecting 150 countries to boost global trade.

In Kenya, the Chinese road building process for the Nairobi Expressway was in record time ahead of schedule. The Chinese effectively used pre-stressed concrete slabs to span longer lengths of the off-grade sections of the road. This effectively accelerated the Nairobi Expressway construction project.

 

2.      The road construction process on site

The actual road building process on site progresses in five (5) steps as follows:

Step 1-Surveying

Setting out the survey points shown on the design drawings. This work is for a surveyor.

Unlike the old days when the process could take a long time when using rudimentary surveying tools, today Total stations and satellite GPS set out the points extremely fast to an accuracy of one (1) second for all the different types of road construction.

Step 2-Earthworks processing

Earthworks mixing and compaction begin. A grader operator mixes the loose soil with water severally as guided by the road supervisor.

Next follows a water bowser driver, who pours an optimum amount of water on the soil material. A motorway roller compactor machine driver then drives on the moist material to a level where the soil mixture is well consolidated.

The minimum width of soil for mixing and compaction is 100-150mm as specified in the road construction manual and method statements.

For highway roads with grade-separated sections, some activities like concrete slab beams, and construction happens offsite and when ready are transported to the motorway building site for installation by the contractor.

The quality manager has a quality control team amongst the construction workers that take material samples for testing in the laboratory. Road construction quality control technicians assess every step of the mixing and compaction for all gravel material composed of road layers for compliance.

Step 3- Highway  building layers process

The highway construction contractor repeats the above process for the subgrade, base course, and sub-base layer.

While the earthworks process is the same, the number of soil layers, compaction level, and the processed pavement width may differ as structurally specified in the drawing by the structural engineer.

The surveyor sets out both the longitudinal and vertical location points for the chainage. They also set out the vertical levels to control the upward road build-up process of the embankment.

The materials engineer confirms if the processed layer has met the design specifications. To confirm this, the quality control conducts field density and plasticity tests on the material sampled from the road.

A key test done is a field density test which confirms whether the soil compacted is well consolidated with minimal air voids.

 The Engineer confirms if the specifications are ok, and the team continues constructing the next layer.

 

Step 4-Road surfacing layer construction

The final process of road construction is the road-wearing course. Depending on which types of roads are being built, the surface material can be asphalt concrete, gravel, or concrete slab.

Asphalt paved roads are popular as asphalt is durable, water resistant and gives good skid friction for rainy and sunny weather conditions.

The road’s surface course can be sub-classified as rigid or flexible pavements. Flexible pavements are less expensive to build and have a greater capacity to expand and contract with temperature differences, so they do not need expansion joints.

Rigid pavements offer higher flexural strength, longer design life, and reduced maintenance costs. A concrete slab road surface is rigid, and this kind of road’s design life is more than 20 years old.

The key heavy road building equipment used is a paver. A paver lays down the thick bituminous materials substance on top of suitable binder material composed of cutbacks (MC30 and K1-60).

The asphalt concrete hot mix design outlines the proportion of prime coat -low viscosity binder bituminous materials applied on the base surface. During asphalt concrete paving, the quality control team conducts frequent testing to ensure the paved material meets the hot mix specifications

 The purpose of the prime coat is to waterproof the base course layer below the layers of asphalt which is also referred to as the bituminous materials layer.

A pneumatic roller consequently drives smoothly and gently over the road surface comprising of chippings and binder material to give it a final finish. The driver does the rolling eight times for satisfactory results.

Step 5-Road furniture and beautification Installation

The road surface is now complete, next the construction team sets out to install the highway furniture.

This comprises motorway markings, road signage, drainage channels on the straight edges side of the highway, motorway lighting, guardrails installation and final planting of flowers or trees on the road shoulders.

These installations make the road safe to use for pedestrians, cyclists, and motorists. They also make the highway appealing to look at.

Road structures are icons of locations like the Golden gate bridge, Guoliang Hanging Tunnel Road in China, and the Boris moots bridge across the English Channel.

 

In conclusion

The highway construction process is intricate, arduous, and time-consuming. But with proper planning, the right budget and good collaboration between the construction project implementation teams, any types of road construction process become smooth and leads to magnificent highways that define our great cities and our neighbourhoods.