--- title: "Construction equipment; prime, tack and seal coats" subject: "Transportation Engineering II" chapter: 3 key: "semester_7/transportation_engineering_ii:equipment-plants-prime-tack-seal-coat" source: https://www.bctengineer.com/q/semester_7/transportation_engineering_ii/equipment-plants-prime-tack-seal-coat site: BCT Engineering --- # Construction equipment; prime, tack and seal coats Transportation Engineering II · Chapter 3: Road Construction Technology - Asked in: 2073 Shrawan, 8 marks - Video: [what is Prime Coat,Tack coat & Seal Coat?|difference between prime,tack and seal coat](https://www.youtube.com/watch?v=sBcObwNIcqE) — Civillogy (Study of Civil Engineering) - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/transportation_engineering_ii/equipment-plants-prime-tack-seal-coat - Whole chapter: https://www.bctengineer.com/md/semester_7/transportation_engineering_ii/chapter-3 ## Question What are the equipment and plants needed for the various activities of road construction? Describe prime coat, tack coat and seal coat with their usefulness. ## Short answer Equipment and plants include bulldozers, graders, rollers, crushers, hot-mix plants, pressure distributors, paver-finishers, chip spreaders and batching plants. Prime coat binds granular base and bituminous layer; tack coat bonds old and new bituminous/CC layers; seal coat seals voids, waterproofs and improves skid resistance. ## Answer #### 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. #### Prime coat, tack coat and seal coat - **Prime coat**: low-viscosity cutback bitumen (MC-30 / MC-70) or emulsion sprayed on an unbound granular (WBM/WMM) surface before bituminous layers are laid (rate 0.6-1.0 kg/m2). It binds loose dust, plugs the surface voids, hardens the top, and provides adhesion between the base and the bituminous layer (IRC:16). - **Tack coat**: a thin film of bitumen emulsion (RS-1 / SS-1) or cutback (rate 0.20-0.30 kg/m2) sprayed on an existing bituminous or cement concrete surface before overlaying. It bonds the old and new layers, preventing slippage and delamination. - **Seal coat**: a thin surface treatment of bitumen (about 0.7-1.0 kg/m2) with 6.7 mm chips or sand, laid on a newly laid open-textured surface (such as premix carpet) or on an old surface (IRC:14 / MoRTH Section 513). It seals the voids, makes the surface waterproof, protects it against weathering and improves skid resistance. **Usefulness**: the three coats give the bond, waterproofing and protection that make the layers act together: - Prime coat bonds the granular base to the bituminous layer and protects the base from rain during construction. - Tack coat prevents slipping between bituminous layers and between old and new surfaces. - Seal coat protects the surface from water, ageing and wear, and improves skid resistance. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Where is prime coat applied and why? A. On an existing bituminous surface, to bond layers B. On an unbound granular surface, to bind dust, plug voids and bond with the bituminous layer C. On concrete, to cure it D. On top of the wearing course for skid resistance Answer: B. Prime coat, 0.6-1.0 kg/m2 of cutback or emulsion, treats the WBM or WMM base. (Key point: Prime coat use) 2. What is the function of a tack coat? A. To waterproof the top B. To bond old and new bituminous or concrete surfaces, preventing slippage and delamination C. To harden the granular base D. To smooth the surface Answer: B. Tack coat is a thin film (0.20-0.30 kg/m2) applied before overlaying. (Key point: Tack coat use) 3. What is a seal coat? A. A thin bitumen treatment with 6.6 mm chips or sand that seals voids and protects against weathering B. A thick 50 mm binder course C. A cement slurry layer D. A sub-base stabiliser Answer: A. Seal coat of 0.6-0.9 kg/m2 waterproofs and improves skid resistance. (Key point: Seal coat) 4. Which roller is listed among compaction equipment? A. Transit mixer B. Sheep-foot roller C. Rotavator D. Jaw crusher Answer: B. Compaction uses smooth-wheel, vibratory, sheep-foot and pneumatic tyre rollers and plate compactors. (Key point: Compaction equipment) ## Related in Transportation Engineering II - [Seal, prime, tack coat and bituminous concrete](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Aseal-prime-tack-coat-bituminous-concrete) — Transportation Engineering II, chapter 3 - [Prime vs tack coat; surface dressing method](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Aprime-vs-tack-coat-surface-dressing) — Transportation Engineering II, chapter 3 - [Road construction activities; otta seal procedure](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Aactivities-otta-seal-construction) — Transportation Engineering II, chapter 3 - [Road construction activities; plants for bituminous and CC](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Aroad-construction-activities-plants-bituminous-cc) — Transportation Engineering II, chapter 3 - [Road construction equipment and DBSD procedure](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Aequipment-plants-activities-dbsd) — Transportation Engineering II, chapter 3 - [Road construction equipment and mass haul characteristics](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Amass-haul-diagram-equipment-plants) — Transportation Engineering II, chapter 3, asked 3× ## Related in other subjects - [Road construction equipment, paver and bitumen sprayer](https://www.bctengineer.com/question.md?key=semester_8%2Fconstruction_management%3Aroad-equipment-paver-sprayer) — Construction Management, chapter 4