#1 Rapid Chloride Migration Test | RCMT Testing in India

Rapid Chloride Migration Test
(RCMT — NT Build 492)

Determination of the chloride migration coefficient of concrete under non-steady state conditions — providing a more fundamental durability parameter than RCPT for service life modelling and design.

Overview

What is the Rapid Chloride Migration Test?

The Rapid Chloride Migration Test (RCMT) measures the non-steady state chloride migration coefficient (Dnssm) by applying 30V DC across a concrete disc for 24 hours, then splitting the specimen and measuring the chloride penetration depth using silver nitrate indicator. Dnssm is a fundamental material property used in service life prediction models.

Conducted as per NT Build 492, RCMT provides a true diffusion coefficient in m²/s — far more meaningful for service life design than the empirical Coulomb charge of RCPT. It is specified for marine concrete, bridge deck design and durability-based design per fib Model Code and DuraCrete. Global Lab conducts RCMT alongside RCPT for comprehensive chloride resistance characterisation.

True Migration Coefficient

Dnssm in m²/s — directly used in fib Model Code service life calculations.

30V Applied Voltage

Lower voltage than RCPT — reduced heat generation and more accurate diffusion measurement.

Silver Nitrate Indicator

Chloride penetration depth measured precisely using AgNO₃ colorimetric method.

Service Life Input

Dnssm used in DuraCrete, Life-365 and fib MC 2010 service life models.

NABL Certified Reports

All results on NABL-accredited letterhead per NT Build 492.

Combined with RCPT

RCMT + RCPT offered together for comprehensive chloride resistance profile.

Test in Action

Rapid Chloride Migration Test — Site Images

RCMT Cell Assembly with NaCl and NaOH Chambers

30V Applied for Non-Steady State Migration

AgNO3 Spray Reveals Chloride Penetration Depth

Test Procedure

How the Rapid Chloride Migration Test is Conducted

1

Specimen Preparation

50mm thick disc cut from 100mm dia core or cylinder. Vacuum saturated with Ca(OH)₂ solution per NT Build 492.
2

Cell Assembly

Specimen mounted between catholyte (10% NaCl) and anolyte (0.3N NaOH) chambers.
3

Voltage & Duration

30V DC applied. Initial current measured to determine test duration (6–96 hours).
4

Chloride Penetration Depth

After test, specimen split. AgNO₃ solution sprayed on split face. Colorimetric depth measured at 7 points.
5

Dnssm Calculation & Report

Migration coefficient Dnssm = (0.0239(273+T)L) / (U-2)t × [xd - 0.0238√((273+T)Lxd/(U-2))]. NABL report within 48 hours.

Standards & Specifications

Applicable Test Standards

Standard	Title	Scope	Type
NT Build 492	Chloride Migration Coefficient from Non-Steady State Migration Experiments	RCMT	Nordic Standard
fib Model Code 2010	Model Code for Concrete Structures — Service Life Design	Service Life	fib
DuraCrete	Probabilistic Performance Based Durability Design of Concrete Structures	Durability Design	DuraCrete
ASTM C1202	Standard Test Method for Electrical Indication of Concrete Ability to Resist Chloride Penetration	RCPT Reference	ASTM

Applications

Where is the CAPO Test Used?

Marine structure service life design using fib Model Code approach

Bridge deck concrete durability specification for 100-year design life

Nuclear structure concrete chloride migration coefficient determination

Research on SCM combinations for optimised chloride resistance

Precast marine pile and segment durability characterisation

Comparative evaluation of admixtures for chloride resistance improvement

Why Choose Global Lab

Our Advantages

NABL Accredited ReportsLegally valid NT Build 492 certificates for project and research requirements.

True Diffusion CoefficientDnssm directly usable in service life models — not an empirical Coulomb charge.

Combined Durability PackageRCMT + RCPT + Resistivity + Water permeability for complete chloride resistance profile.

Service Life CalculationOur engineers can perform fib Model Code service life calculations using Dnssm.

Pan-India CoverageTesting across all 7 NABL-accredited lab locations.

Fast 48-Hour ReportNABL report with Dnssm issued within 48 hours of test completion.

Rapid Chloride Migration Test(RCMT — NT Build 492)