Ultimate Guide for Road Construction || Mastering in Road Construction

Summary

This video explains the process of widening an existing road from two lanes to four lanes, detailing each phase of the construction. It covers subgrade preparation, embankment filling, sub-base installation, and the use of wet mix macadam, curbstones, and asphalt layers like dense bituminous macadam and wearing course. The video also discusses the importance of surveyors, control pegs, and the various materials and machinery involved. Additionally, the road's design and specifications are emphasized, including the role of the pavement layers in supporting heavy loads and ensuring durability. The video concludes with an overview of miscellaneous works like road markings and signage installation.

Takeaways

• 😀 Widening existing roads from two lanes to four involves various construction processes, including modifications to the existing road structure and the addition of multiple layers.
• 😀 Before construction starts, the natural surface's reduced levels are recorded for later excavation and embankment calculations.
• 😀 Subgrade formation is essential to prepare the base for the road, ensuring the removal of vegetation, topsoil, and any weak soil layers.
• 😀 The subgrade must be compacted to 95% relative density using specifications like the modified proctor density for highways.
• 😀 Sub-base material options include unbound granular and cement-bound sub-bases, with a focus on using locally available materials for cost-effectiveness.
• 😀 Wet mix macadam (WMM) is used as a base for flexible pavements, and its preparation must adhere to specific moisture content and compaction requirements.
• 😀 Surveyors play a key role in controlling the road's width, thickness, and overall alignment using control pegs and string lines.
• 😀 Asphalt work involves several layers: prime coat, tack coat, dense bituminous macadam (DBM), and wearing course (WC), each with precise material and temperature specifications.
• 😀 Dense bituminous macadam (DBM) provides a strong foundation with crushed aggregates, while the wearing course (WC) is the final surface layer with smoother aggregates and slightly more binder material.
• 😀 Shoulders are critical for providing lateral support, protecting from water intrusion, and offering parking space; they are typically constructed with a road base and topped with an asphaltic layer.
• 😀 Miscellaneous tasks, such as central verge filling, road markings, and signage installation, complete the project before final delivery.

Q & A

What is the purpose of the road widening project discussed in the video?

The purpose of the project is to widen an existing two-lane road to a four-lane road to improve traffic flow, accommodate more vehicles, and enhance safety.

Why is it important to remove surface vegetation or topsoil during the subgrade formation process?

Surface vegetation and topsoil are organic materials that decompose over time, potentially creating voids that could lead to pavement settlement. Removing these layers ensures a more stable base for the road construction.

What is subgrade formation, and why is it necessary for road construction?

Subgrade formation is the process of preparing the base layer of the road by removing surface vegetation and compacting the soil to a specific level. It is necessary to create a stable and strong foundation for the subsequent layers of the road.

What are the two types of sub-base materials mentioned in the video?

The two types of sub-base materials discussed are unbound granular sub-base and cement-bound sub-base. The unbound granular sub-base is more commonly used in road projects.

What is the purpose of the wet mix macadam (WMM) in road construction?

Wet mix macadam (WMM) is used as the base course in flexible pavements. It provides a strong and uniform support layer, ensuring high resistance to deformation and distress.

What role do surveyors play in the road construction process?

Surveyors are responsible for marking the width, depth, and level of the road layers. They fix control pegs at intervals to ensure the correct alignment and thickness of each pavement layer.

What is the primary function of the curb stones in road construction?

Curb stones are used to delineate and protect the carriageway, preventing vehicles from straying off the road and helping to separate the road from adjacent areas like sidewalks and medians.

How is the prime coat used in the asphalt work process?

The prime coat is a binding layer between the bituminous and non-bituminous surfaces, like the wet mix macadam. It is applied by spraying heated bitumen over the surface to improve adhesion before laying subsequent layers.

What is the significance of the dense bituminous macadam (DBM) layer in road construction?

Dense bituminous macadam (DBM) provides a strong and durable base for the road surface. It is composed of a mixture of coarse aggregates, fine aggregates, and bitumen, offering resistance to traffic loads and environmental conditions.

What is the difference between DBM and the wearing course (WC) in asphalt work?

The key difference is that the wearing course (WC) is the final surface layer with smoother gradation of aggregates and a higher percentage of bitumen content compared to DBM. It is designed to provide a smooth, durable top layer for the road.