WBM Road (Water Bound Macadam Road) | Material & equipment Required For WBM Road Construction | Construction Procedure of WBM Road | Maintenance of WBM Road | Advantages & disadvantages of WBM road
WBM Road (Water Bound Macadam Road):-
WBM road stands for Water Bound Macadam Road. It is a type of road construction where coarse aggregate is laid in layers and compacted with water. The interlocking of the aggregates provides stability and durability to the road. WBM roads are commonly used in rural areas and low-traffic urban areas. They are cost-effective and require less maintenance as compared to other types of roads.Material Required For WBM Road Construction:-
1. Stones: Stones of different sizes ranging from 90 to 150 mm are used for the construction of WBM roads. These stones should be hard, durable and weather-resistant.
2. Coarse Aggregates: Coarse aggregates including crushed stones, gravel, and various types of rock are needed for the base layer of WBM roads. They provide strength, stability, and resistance against erosion and traffic loads.
2. Coarse Aggregates: Coarse aggregates including crushed stones, gravel, and various types of rock are needed for the base layer of WBM roads. They provide strength, stability, and resistance against erosion and traffic loads.
The properties of coarse aggregate for water bound macadam road include:
i. Strength: The aggregate should have sufficient strength to withstand the weight of heavy loads and prevent deformation. Strength of coarse aggregate water bound macadam should not exceed 45%.
ii. Durability: The aggregate should be durable enough to resist wear and tear, erosion, and weathering.iii. Size: The aggregate size should be larger than the thickness of the compacted layer to ensure better interlocking and stability.
Standard size of coarse aggregate water bound macadam Sub-Base / Base (WBM) (Coarse Aggregates (53 mm to 22.4 mm)) IS:2386 (Part-I)
iv. Shape: Shape of coarse aggregate water bound macadam aggregate should be angular and have good interlocking properties to provide a stable base.v. Cleanliness: The aggregate should be free from any impurities such as dust, clay, or organic matter, which can weaken the bond between the aggregate and the binder.
vi. Specific Gravity: specific gravity of coarse aggregate water bound macadam aggregate should have a specific gravity of at least 2.5 to ensure that it can provide good stability and strength to the pavement.
vii. Water Absorption: water absorption of coarse aggregate for water bound macadam road should not absorb more than 2% of water to ensure that the bond between the aggregate and the binder is not weakened.
viii. Gradation: The aggregate should be well-graded to ensure that it can lock together and form a stable layer. The grading should be such that larger particles occupy the lower portion of the layer and smaller particles at the upper portion.
Following grading adopted for water bound macadam road.
x. Abrasion Resistance: The aggregate should be able to resist abrasion and wear caused by traffic and weather conditions. Following are the abrasion value.
Sub-base = 60
Base course = 50
Surfacing course = 40
xi. Alkali-Silica Reactivity: The aggregate should not react with the alkali present in the binder, which can lead to damage and premature failure of the pavement.
xii. Surface Texture: The surface of the aggregate should be rough enough to provide good grip and ensure skid resistance for vehicles.
3. Fine Aggregates: Fine aggregates such as sand, stone dust, and quarry dust are required for filling the gaps between the coarse aggregates and improving the compaction and stability of the overall road structure.
Fine aggregates for water bound macadam are typically required to possess the following properties:
i. Gradation: Fine aggregates should have a well-graded particle size distribution to enable the efficient binding of the material and promote drainage capabilities.
ii. Cleanliness: Fine aggregates should be free from any type of organic or foreign matter, which can hamper the binding property and reduce strength values.
iii. Durability: Fine aggregates must be strong and durable enough to withstand the effects of abrasion, impact, and weather conditions.
xii. Surface Texture: The surface of the aggregate should be rough enough to provide good grip and ensure skid resistance for vehicles.
xiii. Impact value: The aggregate impact value for water bound macadam should be following.
Sub-base = 50
Base course = 40
Surfacing course = 30
xiv. Flakiness index: The aggregate flakiness index for water bound macadam should be following.
Base course = 15
Surfacing course = 15
Fine aggregates for water bound macadam are typically required to possess the following properties:
i. Gradation: Fine aggregates should have a well-graded particle size distribution to enable the efficient binding of the material and promote drainage capabilities.
ii. Cleanliness: Fine aggregates should be free from any type of organic or foreign matter, which can hamper the binding property and reduce strength values.
iii. Durability: Fine aggregates must be strong and durable enough to withstand the effects of abrasion, impact, and weather conditions.
iv. Angularity: Fine aggregates with angular particle shapes are ideal for providing better interlocking and bond strength.
v. Surface Texture: Fine aggregates with a rough surface texture provide greater grip and traction for vehicles using the road.
vi. Absorption: Fine aggregates should have low water absorption values as this helps to prevent the formation of potholes and increases the longevity of the road surface.
These properties are important for achieving a well-compacted, stable, and durable water bound macadam road that can withstand the repetitive traffic loads.
4. Binding Materials: Binding materials like clay, moorum, and soil stabilizers are used to enhance the cohesion between the aggregates and provide additional stability to the road.
5. Bitumen: Bitumen is a commonly used binding material in water bound macadam road construction. Water bound macadam roads are low-cost, low-volume roads that are constructed by spreading coarse aggregates on a compacted subgrade and then binding them together with a thin layer of bituminous materials.
Bitumen is used as a binder in water bound macadam roads because it provides excellent adhesion between the coarse aggregates and improves the strength and durability of the road. It also helps to prevent dust and erosion, making the road more stable and safer for vehicular traffic.
The properties of bitumen, such as its viscosity, curing time, and abrasion resistance, make it an ideal binding material for water bound macadam roads. Bitumen is typically heated before it is applied to the coarse aggregates, which makes it easier to spread and ensures that it binds properly to the road surface.
Overall, bitumen is a crucial component in the construction of water bound macadam roads, playing an important role in enhancing their durability, stability, and safety for vehicular traffic.
2. Paver finisher: it is also used for the important factor while working on a WBM road.
3. Wheelbarrows: Wheelbarrows are required for transportation of materials such as stones, gravel, and sand.
4. Shovels: Shovels are required for digging and leveling the road surface.
5. Compactors: They are used to compress the WBM layers during the construction process.
1. Setting out the road alignment: The first step is to set out the length and width of the road and define the outer edges of the road with pegs and strings.
2. Excavation: Excavation is done to a depth of approximately 350 mm to 400 mm (depending on requirement) and remove any soft spots, stumps, or other organic material. The foundation is leveled and compacted to ensure stability.
3. Sub-grade preparation: The prepared foundation is then graded to the correct slope and level with the help of a motor grader. A water sprinkling system is used to moisten the sub-grade soil. Heavy vibrations machines are used to compact the sub-grade to the desired density.
4. Applying a layer of coarse aggregate: A layer of large-sized aggregates is laid down over the compacted sub-grade soil. The thickness of this layer is about 100 – 150 mm, and the aggregate size remains within the range of 75-100 mm. The layer is watered and compacted by using a vibratory roller until a dense layer is obtained.
5. Applying a layer of medium-sized aggregate: The next layer of WBM road construction comprises medium-sized Aggregates such as gravel, crushed stone, and slag. The layer is approximately 100 mm – 150 mm thick with particles ranging from 40 mm – 75 mm. The layer is watered and compacted by a vibratory roller until a dense layer is achieved.
6. Applying a layer of fine aggregate: The final layer of WBM road construction involves the use of fine aggregates such as sand, gravel, or quarry fines to fill in the gaps between the coarser aggregates. The layer is approximately 50 mm thick, and the particles range from 10 mm – 25 mm.
7. Binding material: Bitumen, tar, or cement is used as a binding material to bond all the layers. It is then spread out evenly over the surface and allowed to settle for a few days.
8. Surface dressing: The top surface is finished with a thin layer of crushed aggregates or asphalt to provide a smooth surface for vehicular traffic.
9. Compaction: Finally, the compacted road is tested for its strength and stability. The defects, if any, will be rectified, and the final road will be ready for use.
Thus, WBM road construction involves a series of steps starting from setting out the alignment to the final layer of surface dressing with bitumen or asphalt. The quality of material, proper compaction, and stabilization determine the longevity and durability of the road.
v. Surface Texture: Fine aggregates with a rough surface texture provide greater grip and traction for vehicles using the road.
vi. Absorption: Fine aggregates should have low water absorption values as this helps to prevent the formation of potholes and increases the longevity of the road surface.
These properties are important for achieving a well-compacted, stable, and durable water bound macadam road that can withstand the repetitive traffic loads.
4. Binding Materials: Binding materials like clay, moorum, and soil stabilizers are used to enhance the cohesion between the aggregates and provide additional stability to the road.
5. Bitumen: Bitumen is a commonly used binding material in water bound macadam road construction. Water bound macadam roads are low-cost, low-volume roads that are constructed by spreading coarse aggregates on a compacted subgrade and then binding them together with a thin layer of bituminous materials.
Bitumen is used as a binder in water bound macadam roads because it provides excellent adhesion between the coarse aggregates and improves the strength and durability of the road. It also helps to prevent dust and erosion, making the road more stable and safer for vehicular traffic.
The properties of bitumen, such as its viscosity, curing time, and abrasion resistance, make it an ideal binding material for water bound macadam roads. Bitumen is typically heated before it is applied to the coarse aggregates, which makes it easier to spread and ensures that it binds properly to the road surface.
Overall, bitumen is a crucial component in the construction of water bound macadam roads, playing an important role in enhancing their durability, stability, and safety for vehicular traffic.
Equipment Required For WBM Road Construction:-
1. Equipment: Equipment required for the construction of WBM roads includes motor graders, bulldozers, excavators, rollers, bitumen sprayers, and water tankers.2. Paver finisher: it is also used for the important factor while working on a WBM road.
3. Wheelbarrows: Wheelbarrows are required for transportation of materials such as stones, gravel, and sand.
4. Shovels: Shovels are required for digging and leveling the road surface.
5. Compactors: They are used to compress the WBM layers during the construction process.
Construction Procedure of WBM Road:-
The construction procedure of WBM (Water Bound Macadam) road involves the following steps:1. Setting out the road alignment: The first step is to set out the length and width of the road and define the outer edges of the road with pegs and strings.
2. Excavation: Excavation is done to a depth of approximately 350 mm to 400 mm (depending on requirement) and remove any soft spots, stumps, or other organic material. The foundation is leveled and compacted to ensure stability.
3. Sub-grade preparation: The prepared foundation is then graded to the correct slope and level with the help of a motor grader. A water sprinkling system is used to moisten the sub-grade soil. Heavy vibrations machines are used to compact the sub-grade to the desired density.
4. Applying a layer of coarse aggregate: A layer of large-sized aggregates is laid down over the compacted sub-grade soil. The thickness of this layer is about 100 – 150 mm, and the aggregate size remains within the range of 75-100 mm. The layer is watered and compacted by using a vibratory roller until a dense layer is obtained.
5. Applying a layer of medium-sized aggregate: The next layer of WBM road construction comprises medium-sized Aggregates such as gravel, crushed stone, and slag. The layer is approximately 100 mm – 150 mm thick with particles ranging from 40 mm – 75 mm. The layer is watered and compacted by a vibratory roller until a dense layer is achieved.
6. Applying a layer of fine aggregate: The final layer of WBM road construction involves the use of fine aggregates such as sand, gravel, or quarry fines to fill in the gaps between the coarser aggregates. The layer is approximately 50 mm thick, and the particles range from 10 mm – 25 mm.
7. Binding material: Bitumen, tar, or cement is used as a binding material to bond all the layers. It is then spread out evenly over the surface and allowed to settle for a few days.
8. Surface dressing: The top surface is finished with a thin layer of crushed aggregates or asphalt to provide a smooth surface for vehicular traffic.
9. Compaction: Finally, the compacted road is tested for its strength and stability. The defects, if any, will be rectified, and the final road will be ready for use.
Thus, WBM road construction involves a series of steps starting from setting out the alignment to the final layer of surface dressing with bitumen or asphalt. The quality of material, proper compaction, and stabilization determine the longevity and durability of the road.
Maintenance of WBM Road:-
WBM (Water Bound Macadam) roads are constructed by compacting layers of crushed stones and soil. These roads require regular maintenance to ensure their durability and functionality. Here are the steps involved in maintaining WBM roads:1. Cleaning: Cleaning the road of debris, dust, and dirt is an essential step in maintaining WBM roads. The cleaning process can be done by sweeping or washing the road surface.
2. Filling potholes: Potholes on the road surface can be filled with a mixture of stones and soil. The mixture should be compacted to ensure stability.
3. Patching: Damaged sections of the road can be repaired by patching. The damaged area is removed, and new WBM material is used to fill the area and compacted.
4. Grading: The surface of the road needs to be leveled to avoid waterlogging. Gravel and soil material can be added to level the surface.
5. Watering: Water is essential to bind the WBM material. The surface of the road requires regular watering to ensure stability.
6. Rolling: The road is compacted with a roller to provide stability to the road surface.
7. Drainage: Drainage is an essential component of the WBM road. The road surface needs to slope to the side, and drainage channels need to be provided to prevent waterlogging.
8. Resurfacing: Resurfacing involves adding fresh layers of crushed stones and soil to the existing road surface. This is done to restore the surface of the road to its original form and ensure durability.
These maintenance steps need to be performed regularly to keep the WBM road in good condition.
2. WBM Road is easier and faster to construct as it requires less equipment and lesser skilled labor.
3. WBM Road provides good traction to vehicles due to the rough surface of the stones.
4. WBM Road has good drainage properties as it allows water to seep through the surface and therefore does not cause waterlogging.
5. WBM Road is an eco-friendly road as it does not require raw materials like bitumen or asphalt.
2. WBM Road generates a lot of dust which can cause problems for pedestrians and nearby residents.
3. WBM Road requires regular maintenance as the stones have a tendency to shift and become uneven with time.
4. WBM Road is limited to low traffic areas and cannot withstand heavy traffic.
5. The rough surface of WBM Road can cause a harsh ride for passengers and vehicles.
2. Filling potholes: Potholes on the road surface can be filled with a mixture of stones and soil. The mixture should be compacted to ensure stability.
3. Patching: Damaged sections of the road can be repaired by patching. The damaged area is removed, and new WBM material is used to fill the area and compacted.
4. Grading: The surface of the road needs to be leveled to avoid waterlogging. Gravel and soil material can be added to level the surface.
5. Watering: Water is essential to bind the WBM material. The surface of the road requires regular watering to ensure stability.
6. Rolling: The road is compacted with a roller to provide stability to the road surface.
7. Drainage: Drainage is an essential component of the WBM road. The road surface needs to slope to the side, and drainage channels need to be provided to prevent waterlogging.
8. Resurfacing: Resurfacing involves adding fresh layers of crushed stones and soil to the existing road surface. This is done to restore the surface of the road to its original form and ensure durability.
These maintenance steps need to be performed regularly to keep the WBM road in good condition.
Advantages of WBM Road:-
1. The cost of constructing WBM Road is lower as compared to other types of roads.2. WBM Road is easier and faster to construct as it requires less equipment and lesser skilled labor.
3. WBM Road provides good traction to vehicles due to the rough surface of the stones.
4. WBM Road has good drainage properties as it allows water to seep through the surface and therefore does not cause waterlogging.
5. WBM Road is an eco-friendly road as it does not require raw materials like bitumen or asphalt.
Disadvantages of WBM Road:-
1. WBM Road is less durable as compared to other types of roads like asphalt or concrete.2. WBM Road generates a lot of dust which can cause problems for pedestrians and nearby residents.
3. WBM Road requires regular maintenance as the stones have a tendency to shift and become uneven with time.
4. WBM Road is limited to low traffic areas and cannot withstand heavy traffic.
5. The rough surface of WBM Road can cause a harsh ride for passengers and vehicles.
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