Road construction activities; plants for bituminous and CC

Activities in road construction

The main activities in constructing a road are:

1. Survey and setting out - final location survey, fixing the centre line, bench marks, and clearing limits (right of way).
2. Site clearance - cutting trees, removing stumps, boulders and topsoil; demolition of structures.
3. Earthwork - excavation in cut, hauling and filling to form the formation level; compaction of embankment in layers (150-200 mm) to 95-97 percent of Proctor density; benching and slope trimming in hills (planned using the mass haul diagram).
4. Drainage and protection works - side drains, catch-water drains, cross-drainage (culverts, causeways), retaining/breast walls, bioengineering for slopes.
5. Subgrade preparation - scarifying, watering, compacting the top 500 mm of soil to specification and checking CBR.
6. Sub-base and base courses - granular sub-base (GSB), WBM/WMM or stabilised base; each layer spread, watered and rolled.
7. Surfacing - prime coat, tack coat, bituminous binder course (DBM/BM) and wearing course (BC, premix carpet, surface dressing, Otta seal), or a cement concrete pavement slab.
8. Shoulders and kerbs - construction of earth/gravel shoulders, kerbs and edge drains.
9. Road furniture and finishing - signs, markings, guard rails, kilometre posts, plantation.
10. Quality control and measurement - field tests, levels, thickness, density and payment measurement, following the Nepal DoR "Standard Specifications for Road and Bridge Works" and IRC/MoRTH specifications.

Plants and equipment for bituminous roads

• Aggregate: stone crusher and screens.
• Binder: bitumen boiler/heater, pressure distributor (sprayer) for tack and prime coats.
• Mix production: hot-mix plant (batch or drum) with dryer, mixer and temperature control.
• Placing: paver-finisher, motor grader, chip spreader.
• Compaction: smooth-wheel (8-10 t) and tandem rollers, pneumatic tyre roller.
• Haulage and site tools: covered tippers, sweeper/blower, thermometers.

Plants and equipment for cement concrete roads

• Batching and mixing plant with silos, weigh batchers and transit mixers.
• Paving: slip-form paver or fixed-form paving train, with side forms and dowel baskets.
• Compaction: needle vibrators and surface (screed) vibrators.
• Finishing: straight edges, floats, texturing (tining) machine, curing compound sprayer.
• Joints: concrete saw (joint cutter), sealant applicator.
• Subgrade/sub-base: grader, rollers and a DLC paver.