WBM (Water Bound Macadam) Road: Construction Procedure, Advantages and Disadvantages

Hello visitors, on this page I will discuss the Water Bound Macadam road construction technology. The water-bound macadam road is the latest road construction technology. After making an earthen road we can construct this type of road.

The crushed or broken stone aggregates are the main essential material to construct a Water Bound Macadam road. Using stone aggregates rather than rolling or moving vehicles.

Water bound Mecadam

The main principle of the Water Bound Macadam pavement structure is that the crush of broken stone aggregates is bound together by the action of rolling or traffic moving.

Water-bound macadam is known after the name of John Macadam.

The bidding is achieved by stone dust used as filler material in the presence of water on this road. The water is used to make the required gradient and shape slope of stone aggregates to each other by the action of rolling or traffic. 

Usually, the thickness of the water-bound macadam road layer is 8-30 cm. The chamber may be ranging between 1 by 36 and 1 by 48 in Water Bound Macadam Road Construction.

Water Bound Macadam Road Construction Materials

Visitors, if you know already about the required materials to construct Water Bound Macadam Road. Also, you can read the following materials to know more details about the construction materials. 

The crushed or broken aggregates are important materials to construct this road because this material should be hard, durable, acceptable, and free from elongation in the Water Bound Macadam road. 

We maintain the stone and aggregate properties in the different pavements like a subbase, subgrade, and surface course. Maintain properties detailed below:

Loss angle abrasion value = 60% (sub-base) / 50%(Base course) / 40% (Surface course)

Aggregates value = 50% (sub-base) / 40%( base course) / 30% ( surface course)

Flakiness index = 15 % ( base course) /15% ( surface course)

Screening

The screening is used to fill up the road in the computed layer of course aggregate.

They considered small-sized of course aggregate with non-plastic material. Screenings used to bind coarse aggregate to each other on the water-bound macadam road construction technology.

The screening also maintains the following properties below

Liquid limit <20% plasticity index <6% proportion of fine passing 0.075 mm sieve size<10%.

Binding Material

Binding materials are used to prevent the revealing of the stone. Fine-grain and locally available materials like limestone dust etc may be used for water-bound macadam roads. 

The binding materials maintain the following properties:

Plasticity index 4 to 9 % in WBM surface course construction 

Plasticity index <6% In WBM layer as a base course and sub-base course.

Equipment Required

The construction of the Water Bound Macadam road required the following equipment.

• Aggregate spreader
• Roller
• Tipper
• Water tanker
• Manually for small projects.

water Water-bound Macadam road Construction Procedure

Preparation of subgrade

For the preparation of the subgrade, the following steps are necessary which are listed below.

Site clearing

Site clearance may be done manually using a space pick or hand shovel or using mechanical equipment like a dozer, scraper, tippers, rollers, etc.

Excavation and construction of fills

Excavation and construction of fills to bring the road to the desired grade may also be done manually or using excavation and compaction equipment. 

The shaping of subgrade

The subgrade should compute the desired grade camber and longitudinal profile. 

Pavement construction

The soil was dumped on the prepared subgrade and pulverized. The moisture content check and if extra moisture is needed and rolled in the layer such that the compaction thickness net doesn’t exceed 10 cm.

Materials required with compaction factor (labor 20 % extra) are along the road.

Arrangement of lateral confinement

Spreading of course aggregate with compacted thickness of 8 to 15 cm.

Compaction with smooth wheel roller or vibratory roller 6 to 10 tons.

Application of screening aggregates and wet rolling of fill about 50 % of total voids.

Application of filler materials (stone dust) with a Plasticity Index value less than or equal to 9 in two thin successive layers.

Finishing of the surface with 6 cm thick sand earth sprinkling with water and rolling.

On the road, the pavement marked shoulder distance.

Opening to traffic after a few days of completion of water-bound macadam road construction.

Quality control

Checking chamber and pavement grade.

Conducting after bergs limit of filler material gradation of aggregate, frankness index.

Note: The Flakiness Index is the total weight of the material passing the various thickness gauges or sieves, expressed as a percentage of the total weight of the sample gauged.

Advantages of WBM Road

The following points are the advantages of water bound macadam road

• The WBM road construction costs are relatively low compared to others.
• No need to require skilled labor for the construction of WBM.
• The locally available materials can be used to construct the WBM road.
• In this construction, the vehicle or traffic load can resist around 900 tons per day per lane on the road pavement.
• easy to road safety provision

Disadvantages of WBM

The following are the disadvantages of WBM Road.

• The road maintenance cost is higher than others.
• The traffic or vehicles are dangerous to move on the road due to the low maintenance of the road.
• The WBM road is directly affected by the water.

Conclusion

Water-bound macadam road may be a road during which the wearing course consists of unpolluted crushed aggregates that are mechanically interlocked by rolling. These aggregates are bound alongside filler material and water laid on a well-compacted base course.

Water-bound macadam road may be a road during which the wearing course consists of unpolluted crushed aggregates. These aggregates are bound alongside filler material and water laid on a well-compacted base course.

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