What is the difference between this test and Part 1 of IS 14959?

Part 2 is for hardened concrete and mortar, while Part 1 is for fresh concrete and constituent materials.

Why is it important to test for chlorides in hardened concrete?

To assess the risk of corrosion of embedded steel reinforcement, which can be caused by chlorides penetrating the concrete from the environment (e.g., de-icing salts, marine spray) or from contaminated materials.

What are the acceptable limits for chloride content?

This standard only provides the test method. The acceptable limits are defined in design codes like IS 456:2000 (Table 8), which vary depending on whether the concrete is plain, reinforced, or prestressed.

What is the principle of the titration method used?

It uses Mohr's method, where a chloride solution is titrated against silver nitrate. Silver chloride precipitates, and the endpoint is detected when excess silver nitrate reacts with a potassium chromate indicator to form a reddish-brown silver chromate precipitate.

IS 14959

: 2000

Method of Test determination of water-soluble and acid-soluble chlorides in mortar and concrete, Part 1: Fresh mortar and concrete

CurrentSpecializedTesting MethodMaterials Science · Cement, Concrete, Aggregates and RCC

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This standard details the laboratory test methods for determining both water-soluble and acid-soluble chloride content in fresh concrete and mortar samples. The procedures are based on chemical titration and are essential for quality control to prevent reinforcement corrosion and ensure long-term durability.

Method of Test determination of water-soluble and acid-soluble chlorides in mortar and concrete, Part 1: Fresh mortar and concrete

Quick Reference Values

Sample drying temperature105 ± 5 °C

Sample finenessPassing 150-micron IS Sieve

Minimum sample weight for testing5 g

Titrant normality0.1 N Silver Nitrate (AgNO3)

Indicator for titration5 percent Potassium Chromate (K2CrO4) solution

Key Formulas

Chloride percent by mass = (3.545 * V * N) / W

Practical Notes

Water-soluble chlorides indicate the immediate corrosion risk, while acid-soluble chlorides represent the total chloride content (both free and bound).

Proper sampling from the structure is critical for a representative result. Samples are often taken as drilled powder at different depths from the concrete surface.

The results from this test are compared against the permissible limits given in IS 456 (Table 8) to determine compliance and potential for long-term damage.