---
title: "Explanatory note: interface treatment"
subject: "Transportation Engineering II"
chapter: 3
key: "semester_7/transportation_engineering_ii:interface-treatment-note"
source: https://www.bctengineer.com/q/semester_7/transportation_engineering_ii/interface-treatment-note
site: BCT Engineering
---

# Explanatory note: interface treatment

Transportation Engineering II · Chapter 3: Road Construction Technology

- Asked in: 2066 Bhadra, 2 marks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/transportation_engineering_ii/interface-treatment-note
- Whole chapter: https://www.bctengineer.com/md/semester_7/transportation_engineering_ii/chapter-3

## Question

Write down an explanatory note on bituminous construction type: interface treatment.

## Short answer

Interface treatment provides a bond between pavement layers by sweeping clean and spraying a prime coat on granular bases (0.6-1.0 kg/m²) or a tack coat on bituminous surfaces (0.20-0.30 kg/m²), followed by curing. It prevents slippage, delamination, and water entry, and is done just before laying.

## Answer

**Interface treatment** is the preparation of the surface between two pavement layers (for example, between a granular base and a bituminous layer, or between an old and a new bituminous layer) to give a good bond. The surface is first swept clean and then sprayed with a prime coat on granular bases or a tack coat on bituminous or concrete surfaces. A good interface bond prevents slippage and delamination, helps the layers act together as one structure (reducing tensile strain at the bottom of the bituminous layer), and stops water entering between layers. Interface treatment is done just before laying, with the correct rate of spray (prime coat 0.6-1.0 kg/m2, tack coat 0.20-0.30 kg/m2) and sufficient curing/breaking time.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Interface treatment means:
   A. Mixing two bituminous layers together
   B. Preparing the surface between two pavement layers to give a good bond
   C. Widening the pavement interface at the shoulder
   D. Treating the subgrade with lime
   Answer: B. It is the preparation (cleaning and prime or tack coat) of the surface between layers to ensure bond. (Key point: Meaning)

2. Which treatment is given to a granular base and to an existing bituminous surface respectively?
   A. Tack coat; prime coat
   B. Prime coat; tack coat
   C. Prime coat; prime coat
   D. Tack coat; tack coat
   Answer: B. Prime coat suits granular bases; tack coat suits bituminous or concrete surfaces. (Key point: Choice of coat)

3. A good interface bond is important mainly because it:
   A. prevents slippage and delamination and lets layers act as one structure, reducing tensile strain at the bottom of the bituminous layer
   B. makes the road darker
   C. increases the camber
   D. removes the need for compaction
   Answer: A. Bond keeps layers acting together, avoids slippage and delamination, and stops water entering between layers. (Key point: Why bond matters)

## Related in Transportation Engineering II

- [Explanatory note: surface dressing](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Asurface-dressing-note) — Transportation Engineering II, chapter 3
- [Bituminous premix carpet construction](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Apremix-carpet-construction) — Transportation Engineering II, chapter 3, asked 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
- [Bituminous pavement types; asphalt concrete construction](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Atypes-bituminous-pavement-ac-construction) — Transportation Engineering II, chapter 3
- [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
- [Double surface treatment materials and procedure](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Adouble-surface-treatment-material-procedure) — Transportation Engineering II, chapter 3

## Related in other subjects

- [Post construction anti-termite treatment](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Apost-construction-antitermite) — Civil Engineering Materials, chapter 9
- [Foundation treatment before gravity dam construction](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Afoundation-treatment-gravity-dam) — Hydropower Engineering, chapter 4
- [Tests on bituminous binders](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Abitumen-tests-list) — Transportation Engineering I, chapter 6, asked 8×
- [Types of bitumen and bituminous materials](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Abitumen-types) — Transportation Engineering I, chapter 6, asked 6×