--- title: "Road construction activities; otta seal procedure" subject: "Transportation Engineering II" chapter: 3 key: "semester_7/transportation_engineering_ii:activities-otta-seal-construction" source: https://www.bctengineer.com/q/semester_7/transportation_engineering_ii/activities-otta-seal-construction site: BCT Engineering --- # Road construction activities; otta seal procedure Transportation Engineering II · Chapter 3: Road Construction Technology - Asked in: 2072 Chaitra, 8 marks - Video: [Otta seal fixable Pavement work गर्ने तरिकाहरु](https://www.youtube.com/watch?v=N34Hr-w010s) — CEQ TV - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/transportation_engineering_ii/activities-otta-seal-construction - Whole chapter: https://www.bctengineer.com/md/semester_7/transportation_engineering_ii/chapter-3 ## Question What are the various activities involved in road construction? Explain the construction procedure of otta seal. ## Short answer Road construction activities are survey, clearance, earthwork, drainage/protection, subgrade preparation, sub-base/base, surfacing, shoulders, furniture and quality control. Otta seal: prepare base, spray soft binder at 1.4-2.0 L/m2, spread graded 16-19 mm aggregate, roll with pneumatic roller for many passes, broom loose stones; traffic improves it. ## Answer #### 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. #### Construction procedure of Otta seal **Otta seal** is a low-cost bituminous surfacing made of a single or double layer of graded natural gravel or crushed stone (maximum size 16-19 mm) rolled into a relatively thick film of soft binder (cutback such as MC-3000, or 150/200 penetration bitumen) sprayed on the base. It originated in Norway (Norwegian Public Roads Administration, Note 31) and is used on low-volume roads in Nepal under DoR guidelines. **Materials**: graded aggregate (continuous grading, maximum size 16 or 19 mm; fines below about 10 percent; flakiness below 30 percent) from a crusher or river source; soft binder (150/200 penetration bitumen cut back with kerosene, or emulsion). A prime coat on the base is generally not required, which is one of the advantages of Otta seal. **Construction** 1. Prepare the base (WBM, crushed gravel or stabilised base) to a smooth, tight surface; patch defects and sweep it clean (prime only if the specification asks for it). 2. Spray the binder with a distributor at the specified rate (about 1.4 to 2.0 litres per m2 for the first layer, depending on the grading and the base) at its spraying temperature (about 120-150 C for hot binders). 3. Immediately spread the aggregate (about 13-16 litres per m2, slightly damp) by chip spreader or tipper to cover the binder fully. 4. Roll with a pneumatic tyre roller (at least 12 t) with many passes (about 15 or more); the kneading forces the binder up through the aggregate. 5. Broom loose stones back onto the surface during the first days. For a double Otta seal, apply the second layer (binder and a finer graded aggregate) in the same way after the first layer has bedded in under traffic. 6. Allow traffic at low speed. The seal improves with traffic over the first weeks as the binder works up into the aggregate. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What is done in subgrade preparation? A. Scarifying, watering and compacting the top 500 mm and checking CBR B. Only sweeping C. Laying DBM D. Sealing joints Answer: A. The top 500 mm is compacted to specification and CBR checked. (Key point: Subgrade work) 2. What is an Otta seal? A. A single or double layer of graded gravel or crushed stone rolled into a soft binder on a base B. A cement concrete slab C. Hot-mix dense asphalt D. A thick WBM layer Answer: A. It originated in Norway as a low-cost surfacing for low-volume roads using aggregate up to 16-19 mm. (Key point: Otta seal definition) 3. Which roller is used for Otta seal and what does it do? A. A steel roller of 2 t to crush stones B. A pneumatic tyre roller of at least 12 t, forcing the binder up through the aggregate C. A sheep-foot roller D. No rolling is needed Answer: B. At least 4 passes with a heavy pneumatic roller embed the aggregate and bring binder up. (Key point: Roller for Otta seal) 4. When is the aggregate spread in Otta seal construction? A. Hours after the binder has cooled B. Immediately after spraying the binder C. Before spraying the binder D. After first traffic Answer: B. The slightly damp aggregate is spread immediately to cover the binder while it is workable. 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