What concrete grade is used for kerb construction?

Concrete kerbs are generally constructed using M20 grade concrete designed and approved as per IS 10262 and MoRT&H Clause 1700.

What tolerance is allowed for kerb line and level?

The permissible tolerance for kerb line and level is generally ±5 to ±6 mm unless otherwise specified in the project documents.

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.

Methodology for Kerb Casting – MoRTH Compliant

Methodology for Kerb Casting

Q: What is the recommended interval for expansion joints in concrete kerbs?

Expansion joints in concrete kerbs are normally provided at 5 m intervals by saw cutting after the concrete has attained sufficient strength.

MoRTH Compliant Cast-in-Situ & Precast Mix Design QC & Safety

1. Scope

This method statement describes the procedure for construction of cement concrete kerbs in central medians, footpaths, traffic separators and road edges in accordance with approved drawings and MoRT&H specifications. The methodology covers both mechanized cast-in-situ kerb construction and precast kerb installation where machine casting is not feasible. The intent of this document is to ensure uniform quality, dimensional accuracy, durability, and safety during execution of kerb works.

2. Reference Standards

Standard / Specification	Reference
MoRT&H Specifications for Road & Bridge Works	Clause 409, Clause 1700
Concrete Mix Design	IS 10262:2019
Plain & Reinforced Concrete	IS 456:2000

3. Materials & Mix Design

Concrete kerbs shall be constructed using cement concrete conforming to the approved mix design. The mix shall be designed, tested and approved by the project Quality Control laboratory in accordance with IS 10262 and MoRT&H Clause 1700 before commencement of works.

Concrete Grade: M20
Cement: OPC / PPC conforming to relevant IS standards
Aggregates: From approved source, clean, hard, durable and well graded
Slump Range: 10–25 mm to suit kerb casting operations
Curing: Water curing or approved curing compound

4. Type of Construction & Equipment

Kerbs shall preferably be constructed using a mechanized continuous kerb casting machine to ensure uniformity in alignment, dimensions, surface finish and productivity. The mechanized methodology offers better control over line, level and consistency and is therefore recommended for long and continuous stretches of kerbs.

Precast concrete kerbs may be adopted in restricted or isolated locations such as junctions, sharp curves, tie-ins and constrained areas where operation of a kerb casting machine is not feasible. In such cases, kerbs shall be laid manually over approved bedding concrete.

Type of Construction

Mechanized Kerb Construction using continuous kerb casting machine
Manual Kerb Casting with fixed formwork
Precast Kerb Installation at junctions, curves and constrained areas

Equipment & Tools

Kerb casting machine (sensor-controlled / string-line controlled)
Batching plant for concrete production
Transit mixers for transportation of concrete
Auto level with staff for line and level control
Hand tools for finishing and minor corrections

5. Preparation & Transportation of Concrete

Concrete shall be produced at an approved batching plant and transported to site using transit mixers. Slump shall be checked at site before placement to ensure conformity with the approved limits. Any non-conforming concrete shall be rejected and removed from site.

6. Laying Procedure

Set out kerb line and level using pegs and string line at 10 m intervals, reduced to 5 m on curves.
Prepare the base by ensuring WMM or PCC surface is clean, level and approved.
Position the kerb casting machine accurately over reference lines.
Feed approved concrete mix into the machine and cast kerb continuously, maintaining required dimensions.
Provide bedding concrete of 40–70 mm thickness where specified.
Finish exposed surfaces manually to achieve smooth and uniform appearance.
Cut expansion joints at nominal 5 m intervals after concrete gains sufficient strength using a saw blade of 3–5 mm thickness.
Where machine casting is not feasible, kerbs shall be cast manually using approved formwork.

7. Quality Control & Inspection

Quality control shall be exercised at all stages of construction as per MoRT&H requirements. Inspection records shall be maintained jointly with the Engineer’s representative to ensure compliance with approved specifications.

S.No	Activity	Inspection	Tests	Remarks
1	Approval of base (WMM / PCC)	Required	Level & density checks	Before casting
2	Kerb casting & finishing	Required	Visual & dimensional checks	During work
3	Concrete strength	Required	Cube compressive test	As per MoRT&H

8. Tolerances

The permissible deviation for line and level of concrete kerbs shall generally be within ±5 to ±6 mm, unless otherwise specified in the approved project drawings or contract documents.

9. Safety Measures

All safety measures shall be implemented as per the approved EHS plan. Adequate PPE, barricading, traffic diversion arrangements, warning signage and safe equipment operation shall be ensured during kerb construction works to protect workers and road users.