- 2080 Bhadra · 8 marks
Road construction equipment and DBSD procedure
Short answer
Road equipment is grouped by work: earthwork (dozer, excavator, grader), compaction (rollers), aggregate (crusher), granular (spreader), bituminous (hot-mix plant, paver, distributor), concrete (batching plant), and small tools. DBSD applies two coats of bitumen with stone chips over a prepared base: prime, spray first coat, spread 13.2 mm chips, roll, then repeat with 11.2 mm chips.
What are the equipment's and plants needed for the various activities of road construction? Write down the material and construction procedure of DBSD.
Equipment and plants for road construction activities
Tools, equipment and plants are grouped by the work they do.
| Work | Equipment / plant | Use |
|---|---|---|
| Clearing and earth work | Bulldozer, excavator (backhoe), front-end loader, scraper, motor grader, tipper/dumper | Clearing, cutting, loading, hauling, spreading and trimming soil; forming camber and side drains |
| Compaction | Smooth-wheel roller (8-10 t), vibratory roller, sheep-foot roller, pneumatic tyre roller, plate compactor, rammer | Compact subgrade, sub-base, base and bituminous layers |
| Aggregate production | Stone crusher (jaw/cone), screens, batching plant | Produce graded aggregate for WBM, WMM, bituminous and concrete |
| Granular layers | Grader, paver or aggregate spreader, water tanker, WMM mixing plant | Mixing, spreading and wetting of GSB, WBM and WMM |
| Bituminous work | Bitumen boiler/heater, pressure distributor (sprayer), hot-mix plant (batch or drum), paver-finisher, chip spreader, sweeper/broom | Spray prime, tack and seal coats; mix, lay and finish bituminous mixes |
| Cement concrete | Concrete batching plant, transit mixer, slip-form or fixed-form paver, needle and surface vibrators, joint cutter, curing sprayer | Produce, place, compact and finish PQC; saw joints |
| Soil stabilisation | Pulveriser (rotavator), cement/lime spreader | Mix cement or lime with soil |
| Small tools | Spades, wheelbarrows, tamping rammers, straight edge, templates, levelling staff, thermometers | Hand work and quality checks |
Plants (hot-mix plant, crusher, batching plant) are fixed installations that produce materials; equipment is mobile machinery that places and compacts them. The choice depends on the quantity of work, haul distance, site access and cost; on small hill roads in Nepal, labour-based methods with light equipment are common.
Double bituminous surface dressing (DBSD)
Double bituminous surface dressing (DBSD) is a surface treatment of two successive applications of bitumen and stone chips on a prepared WBM or granular base, forming a 20-25 mm waterproof wearing surface (IRC:17 and IRC:23; Nepal DoR "Standard Specifications for Road and Bridge Works"). It is used for low-cost roads.
Materials
- Binder: bitumen 80/100 or 60/70, cutback or emulsion; typical rates are about 1.2 kg/m2 for the first coat (with 13.2 mm chips) and about 1.0 kg/m2 for the second coat (with 11.2 mm chips), as fixed by the specification.
- Aggregate: crushed stone or gravel, AIV below 30 percent, flakiness below 25 percent, water absorption below 1 percent, stripping value below 5 percent; first coat 13.2 mm (about 0.15 m3 per 10 m2); second coat 11.2 mm or 6.7 mm (about 0.09 m3 per 10 m2).
- Prime coat over a WBM base if required: 0.6-1.0 kg/m2 of cutback or emulsion.
Construction procedure
- Prepare the base: sweep and clean it, fill all depressions, patch potholes and ensure the correct camber. Apply a prime (or tack) coat and let it cure.
- Spray the first coat of binder with a pressure distributor at the specified rate and spraying temperature (about 150-170 C for paving bitumen; lower for cutback, and emulsion is sprayed cold or warm), as a uniform film, one lane width at a time.
- Immediately spread the first-coat chippings (13.2 mm) by chip spreader or manually, covering 100 percent of the binder without piling.
- Roll with an 8-10 t roller, moving from the edge to the centre; brush off surplus chips.
- Apply the second coat of binder and the smaller chips (11.2 mm) in the same way, then roll.
- Do the final rolling with a pneumatic roller and sweep off loose chips; open to traffic after 24 hours at low speed (20 km/h) for a few days.
- Quality control: bitumen temperature and rate of spread (tray test), chip spread rate, grading, cleanness and surface regularity.
✓ Answer checked by Claude Opus 5.5 (high effort)
Related questions
- Road construction activities; plants for bituminous and CC · Transportation Engineering II, chapter 3
- Road construction activities; otta seal procedure · Transportation Engineering II, chapter 3
- WBM: material, equipment, procedure, quality control · Transportation Engineering II, chapter 3
- Road construction equipment and mass haul characteristics · Transportation Engineering II, chapter 3 · asked 3×
- Construction equipment; prime, tack and seal coats · Transportation Engineering II, chapter 3
- Surface dressing and DBSD construction · Transportation Engineering II, chapter 3
- Road construction equipment, paver and bitumen sprayer · Construction Management, chapter 4
- Advantages and disadvantages of construction equipment · Construction Management, chapter 4 · asked 6×
- Factors in selecting construction equipment · Construction Management, chapter 4 · asked 6×
- Equipment for highway and pavement construction · Construction Management, chapter 4 · asked 3×