Method of Test determination of water-soluble and acid-soluble chlorides in mortar and concrete, Part 2: Hardened mortar and concrete

IS 14959 Part 2: Scope & Key Specifications

• Scope:
  Covers volumetric method for determination of water soluble and acid soluble chlorides in hardened mortar and concrete. Applicable to samples from project sites or ready-mixed concrete plants.

• Sample Age:
  Concrete should be at least 14 days old before sampling to avoid disturbing bond.

• Chloride Calculation Formula:
  [ \text{Chloride, %} = 0.00142 (X - Y) ] Where:

  • (X) = volume of 0.02 N silver nitrate added (ml)
  • (Y) = volume of 0.02 N ammonium thiocyanate consumed (ml)
  • (m) = mass of concrete sample (g)

• Alternate Formula (from Clause 4.4 update):
  [ \text{Chloride, %} = 2 \times 0.709 \times \frac{(X - Y)}{m} ]

• Notes:

  • Use nitrobenzene to avoid interference from silver chloride particles during titration.
  • Record exact normality if standard 0.02 N solution is not achievable.

• References:

  • IS 1070:1992 (Reagent grade water)
  • IS 3025 (Part 32):1988 (Water & wastewater chloride test)

Summary Table

flowchart TD
    A[Concrete Sample ≥14 days] --> B[Prepare Sample]
    B --> C[Add 0.02 N Silver Nitrate (X ml)]
    C --> D[Add 0.02 N Ammonium Thiocyanate (Y ml)]
    D --> E[Calculate Chlor

IS 14959 Part 2: Key Formula for Chloride Determination

For hardened mortar and concrete, the percentage of chloride (acid soluble/water soluble) by mass is calculated volumetrically as:

[ \text{Chloride, %} = \frac{2 \times 0.709 (X - Y)}{m} ]

Where:

• ( X ) = volume of 0.02 N silver nitrate added (ml)
• ( Y ) = volume of 0.02 N ammonium thiocyanate consumed (ml)
• ( m ) = mass of concrete sample taken for test (g)

Important Notes:

• Nitrobenzene is added to avoid interference from silver chloride particles during titration.
• Samples should be at least 14 days old and free from damage.
• Standard normality solutions (0.02 N) of reagents are used; exact normality should be recorded if different.

Relevant References:

Summary Diagram: Chloride Test Process

flowchart TD
    A[Sample Preparation] --> B[Extraction of Chlorides]
    B --> C[Titration with 0.02 N Silver Nitrate]
    C --> D[Back Titration with 0.02 N Ammonium Thiocyanate]
    D --> E[Calculate % Chloride using formula]

This method ensures accurate determination of chloride content critical for assessing concrete durability and corrosion risk.

IS 14959 Part 2: Definitions and Key Formula for Chloride Determination

This standard covers the volumetric method for determining water soluble and acid soluble chlorides in hardened mortar and concrete.

Key Formula (Clause 4.4)

Calculate chloride content (%) by mass of mortar or concrete as:

[ \text{Chloride, %} = \frac{2 \times 0.709 \times (X - Y)}{m} ]

Where:

• X = volume of 0.02 N silver nitrate added (ml)
• Y = volume of 0.02 N ammonium thiocyanate consumed (ml)
• m = mass of concrete sample taken for test (g)

Notes:

• Addition of nitrobenzene avoids interference from silver chloride particles during titration.
• Concrete specimens should be at least 14 days old before sampling.
• Chlorides affect durability by causing steel reinforcement corrosion.
• The test distinguishes between water soluble and acid soluble chlorides.

Summary Table:

This formula is essential for assessing chloride-induced durability risks in concrete structures per IS 14959 Part 2.

IS 14959 Part 2: Method of Test for Chlorides in Hardened Mortar and Concrete

Key Specifications:

• Sample Age: Minimum 14 days old concrete before specimen removal.
• Sample Integrity: No abnormal defects or damage allowed.
• Test Type: Volumetric method for water soluble and acid soluble chlorides.

Important Formula (Clause 4.4):

[ \text{Chloride, percent} = \frac{2 \times 0.709 \times (X - Y)}{m} ]

Where:

• (X) = volume of 0.02 N silver nitrate added (ml)
• (Y) = volume of 0.02 N ammonium thiocyanate consumed (ml)
• (m) = mass of concrete sample (g)

Key Amendments:

• Use 0.02 N solutions for titrations instead of 0.2 N.
• Record exact normality if 0.02 N solution is difficult to prepare.
• Substitute 1.52 g for 1.7 g in reagent calculations.

Notes:

• Chlorides come from aggregates, water, admixtures, and cement.
• Chloride content affects durability due to steel corrosion risk.
• Follow IS 2:1960 for rounding off results.

flowchart TD
    A[Concrete Sample (≥14 days)] --> B[Crushing & Preparation]
    B --> C[Extraction of Chlorides]
    C --> D[Volumetric Titration]
    D --> E[Measure X (AgNO3 volume)]
    D --> F[Measure Y (NH4SCN volume)]
    E & F --> G[Calculate Chloride % using formula]
    G --> H[Report Results (rounded per IS 2:1960)]

This concise summary covers the essentials for performing chloride determination per IS 14959 Part 2.

IS 14959 Part 2: Reagents and Solutions Key Points

• Quality of Reagents (Clause 4.1.1):
  Use analytical reagent grade chemicals and distilled water as per IS 1070.

• Concentrated Nitric Acid (HNO3) 6N Solution (Clause 4.1.2):
  Prepare by diluting 38 ml of concentrated HNO3 (SG 1.42) to 100 ml with distilled water.

• Silver Nitrate (AgNO3) 0.02 N Solution (Clauses 4.1.6 & 1.7):

  • Weigh 1.7 g AgNO3, dissolve in distilled water, dilute to 500 ml in volumetric flask.
  • Standardize against 0.02 N sodium chloride using potassium chromate as indicator (5% w/v per IS 3025 Part 32).

Summary Table

Notes:

• Always standardize AgNO3 solution before use.
• Use potassium chromate indicator for titration endpoint detection.

flowchart LR
    A[Weigh 1.7 g AgNO3] --> B[Dissolve in distilled water]
    B --> C[Dilute to 500 ml in volumetric flask]
    C --> D[Standardize with 0.02 N NaCl]
    D --> E[Use potassium chromate indicator]

Use of Filter Paper as per IS 14959 Part 2

• Filter Paper Type:
  Use Whatman filter paper No. 1 or any equivalent brand with similar porosity.

• Sample Preparation (Clause 4.3.1.1):

  • Weigh 1000 ± 5 g pulverized mortar/concrete in 2L beaker.
  • Add 1000 ml distilled (chloride-free) water. Stir vigorously, warm gently for 15 min.
  • Let settle for 24 h. Decant ~200 ml supernatant.
  • Filter immediately through Whatman No.1 paper.

• Titration Procedure (Clauses 4.3.1.2 & 4.3.2.2):

  • Pipette 50 ml filtrate in 250 ml conical flask.
  • Add 5 ml of 6 N nitric acid.
  • Add known volume (X), preferably 25 ml of 0.2 N silver nitrate.
  • Add 1 ml ferric alum + 5 ml nitrobenzene, shake to coagulate precipitate.
  • Titrate excess silver nitrate with ammonium thiocyanate until faint reddish brown color appears.
    • Use 0.02 N ammonium thiocyanate (Clause 4.3.2.2) or 0.2 N (Clause 4.3.1.2).
  • Note volume of ammonium thiocyanate used = Y ml.

Key Formula for Chloride Content Calculation:

[ \text{Chloride %} = \frac{(X - Y) \times N \times 35.45 \times 100}{\text{Volume of sample (ml)} \times \text{Sample weight (g)}} ]

Where:

• (X) = volume of silver nitrate added (ml)
• (Y) = volume of ammonium thiocyanate used (ml)
• (N) = normality of silver nitrate solution
• 35.45 = atomic weight of chlorine

Summary Table of Reagents and Volumes:

IS 14959 Part 2: Procedure for Determination of Chlorides in Hardened Mortar and Concrete

Key Steps & Specifications:

• Sample Age: Minimum 14 days old concrete specimen.
• Sample Preparation: Remove without disturbing mortar-aggregate bond.
• Titration Method: Volumetric titration using silver nitrate and ammonium thiocyanate.

Important Formulas:

Chloride percentage is calculated as:

[ \text{Chloride, %} = \frac{2 \times 0.709 \times (X - Y)}{m} ]

Where:

• ( X ) = volume of 0.02 N silver nitrate added (ml)
• ( Y ) = volume of 0.02 N ammonium thiocyanate used (ml)
• ( m ) = mass of concrete sample (g)

Procedure Summary:

1. Pipette 50 ml filtrate into a 250 ml conical flask.
2. Add 5 ml of 6 N nitric acid.
3. Add a known volume (X) (preferably 25 ml or more) of 0.02 N silver nitrate.
4. Add 1 ml ferric alum and 5 ml nitrobenzene.
5. Shake to coagulate precipitate.
6. Titrate excess silver nitrate with 0.02 N ammonium thiocyanate until faint reddish brown color appears.
7. Record volume (Y) of ammonium thiocyanate used.

Notes:

• Standardize silver nitrate solution using 0.02 N sodium chloride.
• Adjust solution normality if exact 0.02 N is difficult.
• Follow IS 2:1960 for rounding off results.

flowchart TD
    A[Prepare 50 ml filtrate] --> B[Add 5 ml 6N HNO3]
    B --> C[Add X ml 0.02 N AgNO3]
    C --> D[Add 1 ml ferric alum + 5 ml nitrobenzene]
    D --> E[Shake to coagulate]
    E --> F[Titrate with 0.02 N NH4SCN]
    F --> G[Record volume Y]
    G --> H[Calculate Chloride % using formula]

This method ensures accurate determination of water

IS 14959 (Part 2): Water Soluble Chloride - Key Specifications & Formulas

• Scope: Volumetric method for water soluble chlorides in hardened mortar & concrete.

• Sample: Concrete ≥14 days old; avoid damaged samples.

• Reagents Normality: Use 0.02 N AgNO₃ (silver nitrate) solution; note difficulty in exact normality (Clause 4.1.7).

• Volume of Sample Solution: Use ≥25 ml of extracted solution for titration (Clause 4.3.1.2).

Key Formula for Chloride Content (%)

[ \text{Chloride, %} = \frac{2 \times 0.709 \times (X - Y)}{m} ]

Where:

• The factor 0.709 converts volume to mg chloride.

Notes:

• Chlorides include water soluble and acid soluble forms; water soluble chlorides are more readily available to cause corrosion.

• Testing follows volumetric titration with silver nitrate; ammonium thiocyanate is used as an indicator.

Summary Flow of Test:

flowchart TD
    A[Sample Preparation] --> B[Extraction of Water Soluble Chlorides]
    B --> C[Titration with 0.02 N AgNO₃]
    C --> D[Add Ammonium Thiocyanate Indicator]
    D --> E[Calculate Chloride % using formula]

References: IS 14959 (Part 2): 2001, Clause 4.3.1 & 4.4; IS 2:1960 for rounding.

IS 14959 Part 2: Acid Soluble Chloride - Key Points

• Definition: Acid soluble chlorides include both water soluble chlorides and those bound in the concrete matrix, released by acid treatment.

• Sample Preparation: Concrete must be ≥14 days old; specimens must be intact without damage.

• Titration Method:

  • Use 0.02 N silver nitrate (AgNO3) solution.
  • Volume of AgNO3 used (X ml) is noted.
  • Volume of 0.02 N ammonium thiocyanate (Y ml) consumed is also recorded.

• Formula for Chloride Content (%) (Clause 4.4 substitution):

  [ \text{Chloride, %} = \frac{2 \times 0.709 \times (X - Y)}{m} ]

  where:

  • (X) = volume of 0.02 N AgNO3 added (ml)
  • (Y) = volume of 0.02 N ammonium thiocyanate consumed (ml)
  • (m) = mass of concrete sample (g)

• Normality Notes:

  • Use 0.02 N standard solutions for titrations.
  • If exact 0.02 N is difficult, record the actual normality used.

• Elimination of Nitric Acid Addition: Clause 4.3.2.2 removes the step of adding 5 ml of 6 N nitric acid for acid soluble chloride determination.

Summary Table: Chloride Determination Parameters

This method ensures accurate quantification of acid soluble chlorides critical for assessing corrosion risk in hardened concrete.

IS 14959 Part 2: Calculation of Chloride Content

Key Definitions:

• Water Soluble Chloride (Clause 4.3.1): Chlorides extractable by water from hardened concrete.
• Acid Soluble Chloride (Clause 4.3.2): Chlorides extractable by acid digestion from hardened concrete.

Chloride Content Formula (Clause 4.4)

[ \text{Chloride, %} = \frac{2 \times 0.709 \times (X - Y)}{m} ]

Where:

• (X) = volume of 0.02 N silver nitrate added (ml)
• (Y) = volume of 0.02 N ammonium thiocyanate consumed (ml)
• (m) = mass of concrete sample taken for test (g)

Important Specifications & Notes:

• Use 0.02 N silver nitrate solution (not 0.2 N).
• Sample mass (m) is typically ~1.52 g (updated from 1.7 g).
• Concrete should be at least 14 days old before sampling.
• Exact normality of titrants should be recorded.
• Acid soluble chloride test excludes adding 5 ml of 6 N nitric acid (per latest clause update).

Summary Table: Volumetric Titration Setup

flowchart LR
    A[Concrete Sample (≥14 days)] --> B{Water Soluble Chloride Extraction}
    A --> C{Acid Soluble Chloride Extraction}
    B --> D[Titration with 0.02 N AgNO3]
    C --> E[Titration with 0.02 N AgNO3]
    D --> F[Calculate Chloride % using formula]
    E --> F

This method ensures accurate determination of harmful chlorides affecting concrete durability and reinforcement corrosion risk.

Apparatus Specifications (IS 14959 Part 2)

• Specimen Age: Concrete must be at least 14 days old before sampling to avoid disturbing mortar-aggregate bond.
• Specimen Condition: Avoid specimens with defects or damage during removal.
• Reagents: Use analytical reagent grade chemicals and distilled water (IS 1070 compliant).
• Silver Nitrate: Dry at 160 ℃ and cool in a desiccator before use.
• Volumetric Method: Apparatus must suit volumetric titration for chloride determination.

Key Formula for Chloride Content

[ \text{Chloride, percent} = 2 \times 0.709 \times \frac{(X - Y)}{m} ]

Where:

• (X) = Volume of 0.02 N silver nitrate added (ml)
• (Y) = Volume of 0.02 N ammonium thiocyanate consumed (ml)
• (m) = Mass of concrete sample (g)

Notes on Normality

• Use 0.02 N standard solutions for titrations.
• Record exact normality if standard normality is not achievable.
• Volumes used are 25 ml or more for solutions.

flowchart LR
    A[Sample Preparation] --> B{Concrete Age ≥ 14 days?}
    B -- Yes --> C[Specimen Removal without Damage]
    B -- No --> D[Wait until 14 days]
    C --> E[Dry & Weigh Sample (m)]
    E --> F[Titration with 0.02 N AgNO3 (X ml)]
    F --> G[Titration with 0.02 N NH4SCN (Y ml)]
    G --> H[Calculate Chloride % using formula]

This ensures accurate determination of water and acid soluble chlorides in hardened concrete per IS 14959 Part 2.

IS 14959 Part 2: Sampling and Sample Preparation for Chloride Determination

Key Specifications:

• Sample Age: Minimum 14 days old concrete (hardened enough to avoid disturbing mortar-aggregate bond).
• Sample Size: Pulverized mortar/concrete sample of 1000 ± 5 g.
• Sample Preparation:
  • Water Soluble Chlorides:
    • Add 1000 ml distilled water, stir vigorously, warm gently for 15 min.
    • Stand for 24 h, decant ~200 ml supernatant, filter through Whatman No. 1.
  • Acid Soluble Chlorides:
    • Add 100 ml 6N nitric acid + 900 ml distilled water, stir, warm gently for 30 min.
    • Stand 10-15 min, decant ~200 ml supernatant, filter through Whatman No. 1.

Silver Nitrate Solution Preparation (Clause 1.7):

• Weigh 1.7 g AgNO₃, dissolve in distilled water, dilute to 500 ml.
• Standardize against 0.02 N NaCl using potassium chromate indicator.

Chloride Content Formula (Clause 4.4):

[ \text{Chloride %} = \frac{2 \times 0.709 \times (X - Y)}{m} ]

Where:

• (X) = volume of 0.02 N AgNO₃ (ml)
• (Y) = volume of 0.02 N ammonium thiocyanate consumed (ml)
• (m) = mass of concrete sample (g)

Summary Table:

IS 14959 Part 2: Reporting of Results for Chloride Determination

Key Formula for Chloride Percentage

Calculate chloride (acid soluble/water soluble) percentage by mass of mortar or concrete as:

[ \text{Chloride, %} = 0.00142 \times (X - Y) ]

Where:

• X = volume of 0.02 N silver nitrate added (ml)
• Y = volume of 0.02 N ammonium thiocyanate consumed (ml)
• m = mass of concrete sample (g) (used in some variations)

Notes:

• Record the exact normality of silver nitrate solution used.
• Addition of nitrobenzene prevents interference from silver chloride particles during titration.
• Rounding off results must follow IS 2:1960 rules.

Volumetric Method Summary:

flowchart TD
    A[Concrete Sample (≥14 days)] --> B[Extract mortar/concrete powder]
    B --> C[Prepare filtrate]
    C --> D[Add 0.02 N AgNO3 (X ml)]
    D --> E[Add ferric alum & nitrobenzene]
    E --> F[Titrate excess AgNO3 with 0.02 N NH4SCN (Y ml)]
    F --> G[Calculate Chloride % = 0.00142 × (X - Y)]
    G --> H[Report results per IS 2:1960 rounding rules]

This ensures consistent, accurate reporting of chloride content critical for assessing concrete durability and corrosion risk.

Committee Composition - IS 14959 Part 2 (Annex A)

The Cement and Concrete Sectional Committee, CED 2, responsible for IS 14959 Part 2, comprises experts from:

• Industry Representatives: Cement companies (OCL India, Gujarat Ambuja, The India Cements, Grasim Industries), construction companies (B.G. Shirke, Gammon India, Larsen & Tubro)
• Government Bodies: Central Public Works Department, Ministry of Surface Transport, Central Water Commission, National Test House, Geological Survey of India
• Research Institutes: Structural Engineering Research Centre (CSIR), Indian Institute of Technology Kharagpur, Central Building Research Institute (CSIR)
• Others: Directorate General of Supplies and Disposals, Fly Ash Mission, Builder’s Association of India

Key Formula for Chloride Content (Clause 4.4)

[ \text{Chloride, %} = \frac{2 \times 0.709 \times (X - Y)}{m} ]

• X = volume of 0.02 N silver nitrate added (ml)
• Y = volume of 0.02 N ammonium thiocyanate consumed (ml)
• m = mass of concrete sample (g)

Notes:

• Nitrobenzene may be added to avoid interference by silver chloride particles during titration.
• Samples should be at least 14 days old and undamaged.

This committee composition ensures a comprehensive approach combining industry, government, and research expertise for standard development.