What is the purpose of soil testing?

Soil testing determines properties such as moisture content, plasticity, and strength to ensure suitability for embankment, subgrade, and pavement layers.

Which IS codes are used for soil tests?

Most soil tests follow IS 2720 series. Some field tests may also reference MoRTH or IRC guidelines.

Why is moisture content important in highway construction?

Moisture content affects compaction, strength, and stability of subgrade and embankment layers.

What are common soil test methods?

Tests include Liquid Limit, Plastic Limit, Free Swell Index, CBR, Grain Size Analysis, and Moisture Content determination.

Which method is faster for moisture content determination?

Rapid Moisture Meter (RMM) method is fast for field-based testing, while Sand Bath/Oven-Drying is more accurate in the lab.

Top 8 Proven Steps for Tack Coat Methodology | As per MoRTH Clause 503 (5th Revision)

Table of Contents

Top 8 Proven Steps for Tack Coat Methodology (As per MoRTH Clause 503 – 5th Revision)

1. Scope

The work covers the application of a single uniform coat of bituminous binder (tack coat) over an existing primed or bituminous surface to ensure a strong bond between successive pavement layers, as per MoRTH Clause 503.

2. Reference Standards

MoRTH Specifications, Clause 503 (5th Revision)
IRC: SP: 84-2014 – Specifications & Standards for Road Works
IS: 8887 – Specification for Bitumen Emulsion
IS: 1203 – Determination of Penetration of Bituminous Materials

3. Materials

The tack coat shall consist of Rapid-Setting (RS-1 or RS-2) Cationic Bitumen Emulsion conforming to IS 8887. The material shall be approved by the Engineer based on the manufacturer’s test certificate and on-site verification.

4. Equipment

Calibrated bitumen pressure distributor
Air compressor or blower
Mechanical broom for cleaning surface
Thermometer and spray bar adjustment system

5. Preparation of Surface

The surface shall be free from dust, dirt, and loose material. If required, the surface shall be lightly swept and blown using an air compressor. The surface must be dry before tack coat application.

6. Application of Tack Coat

0.20–0.25 kg/m² on existing bituminous surfaces
0.25–0.30 kg/m² on primed granular surfaces

The bitumen pressure distributor shall ensure even spraying without streaking or overlapping. Spray bar height and pressure must be calibrated before use.

7. Curing and Protection

After application, allow the tack coat to “break” (turn from brown to black) — usually within 30 minutes. No traffic or construction equipment shall move over the surface until the emulsion has fully broken and become tacky.