Methods of analysis of hydraulic cement by X-ray fluorescence spectrometer

IS 12803 - Scope & Calibration Key Points

Scope (Clause 9.2 - 9.3.4)

• Purpose: Calibration of XRF (X-ray fluorescence) for elemental analysis in cement and related materials.
• Calibration is based on linear regression between XRF counts per second (CPS) and element concentration (%).

Key Formula (Clause 9.3.4)

[ Y = mX + c ]

• X: CPS for an element
• Y: Concentration (%) of element
• m: Slope of calibration curve
• c: Y-axis intercept

Interference Correction (Clause 9.3.4.2)

When interference exists, the formula modifies to: [ Y = mX + c + \sum \text{(interference terms)} ]

• Interference depends on other elements present.
• Typical interfering elements for major cement constituents:

Notes:

• Interference coefficients vary by XRF analyzer.
• Minor constituents usually have negligible interference.

graph LR
A[XRF Counts (CPS)] --> B[Calibration Curve]
B --> C[Linear Equation: Y = mX + c]
C --> D{Interference?}
D -- Yes --> E[Add interference terms]
D -- No --> F[Use linear calibration]

IS 12803: Outline of the Method — Key Points

1. Preparation of Standards for Calibration (Clause 9.2)

• Standards must be prepared carefully for accurate calibration of XRF instruments.
• Calibration accounts for matrix effects and inter-element interferences.

2. Experimental Procedure (Clause 4.2)

• Follow the detailed experimental steps for sample preparation and measurement.
• Reproducibility checks are mandatory (Clause 5).

3. Reproducibility Limits for Constituents (Clause 5)

4. Calibration Equation with Interference (Clause 9.3.4.2)

[ Y = mx + c + \sum (k_i \times C_i) ]

• (Y): Measured XRF intensity
• (x): Concentration of element analyzed
• (c): Constant
• (k_i): Interference coefficients
• (C_i): Concentration of interfering elements

5. Typical Interferences (Clause 9.3.4.2)

Summary Diagram: Calibration with Interference

graph LR
  A[Element Analyzed] -->|XRF Intensity| B[Measured Signal Y]
  C[Interfering Elements] -->|Interference Coeff

IS 12803: Reproducibility of Results – Key Points

1. Reproducibility Limits for Constituents (Clause 5)

The difference between repeated determinations (%) must not exceed:

2. Calibration & Checks (Clauses 9.1.1, 9.2, 9.3.3)

• Use standard reference samples for daily calibration.
• Monitor XRF intensity (CPS) for drift.
• Recalibrate if deviations occur.
• Confirm calibration by analyzing a standard cement sample.

3. Practical Notes

• Repeat measurements if reproducibility limits are exceeded.
• Ensure instrumental parameters are consistent between sample and standards.

flowchart TD
    A[Prepare Standard Samples] --> B[Measure XRF Intensity (CPS)]
    B --> C{Is CPS stable?}
    C -- Yes --> D[Analyze Test Samples]
    C -- No --> E[Recalibrate Instrument]
    E --> B
    D --> F[Check Reproducibility Limits]
    F -- Within Limits --> G[Accept Results]
    F -- Exceeds Limits --> H[Repeat Determination]

This ensures reliable and consistent chemical analysis per IS 12803.

IS 12803 - Equipment Key Points

1. Clause 6.2 - Sample Preparation Equipment:

   • Includes all apparatus needed for preparing samples before testing.
   • Must ensure uniformity and representativeness of the sample.

2. Clause 6.2.2 - Fusion Equipment:

   • Equipment used for fusion of samples, such as fusion ovens or furnaces.
   • Must maintain precise temperature control for consistent fusion.

3. Clause 6.4.2 - Cooling & Vacuum Systems:

   • Chilled water supply system to cool X-ray tubes.
   • Suitable vacuum pump and air compressor as per manufacturer specs.
   • Ensures stable operation and prevents overheating.

4. Clause 9.3.3 - Calibration Measurements:

   • Regular calibration of equipment to maintain accuracy.
   • Measurements must be traceable and documented.

Typical Specifications Summary

Example: Fusion Temperature Control Formula

[ Q = m \times C_p \times \Delta T ]

• Q = Heat energy required (J)
• m = Mass of sample (kg)
• C_p = Specific heat capacity (J/kg°C)
• ΔT = Temperature change (°C)

flowchart LR
    A[Sample Preparation] --> B[Fusion Equipment]
    B --> C[Cooling System]
    C --> D[X-ray Tube]
    B --> E[Vacuum Pump]
    B --> F[Air Compressor]
    D --> G[Measurement & Calibration]

This flow ensures sample prep, fusion, cooling, and calibration are integrated for reliable testing per IS 12803.

IS 12803: Sample Preparation Equipment & Procedure Summary

Key Specifications (Clauses 6.2, 9.1, 9.1.1)

• Sample Size: ~100 g for grinding.
• Grinding: Use suitable mill to achieve particle size < 20 microns.
• Pellet Preparation:
  • Take 15-20 g of ground sample.
  • Fill in steel disc/ring or aluminium cup.
  • Apply pressure & time as per preliminary experiments for stable pellets.
• Consistency: Particle size, pressure, and pressing time must be identical for calibration and test samples.
• Binder: Add if required, in fixed proportion for both calibration and test samples.

Important Parameters to Determine Experimentally:

• Grinding time to reach <20 μm particle size.
• Pressure (P) and time (t) for pressing pellets to ensure reproducibility.

Typical Procedure Flow:

flowchart TD
    A[Sample (~100g)] --> B[Grinding to <20μm]
    B --> C[Weigh 15-20g ground sample]
    C --> D[Fill steel disc/aluminium cup]
    D --> E[Apply pressure & time]
    E --> F[Stable Pellet for XRF analysis]

Note: Calibration standards must be prepared using the same procedure to ensure accuracy in XRF intensity measurements.

IS 12803 – Pressed Pellet Equipment & Technique Key Points

Pressed Pellet Equipment (Clause 6.2.1)

• Press capacity: Up to 50 tonnes controllable pressure.
• Pellet size: Suitable for X-ray fluorescence (XRF) analysis.
• Equipment includes steel disc/ring or aluminium cup for pellet formation.

Pressed Pellet Preparation (Clause 9.1.1)

• Sample size: ~100 g ground to particle size < 20 microns.
• Pellet mass: 15-20 g of ground sample.
• Pellet formation:
  • Fill sample in steel/aluminium mould.
  • Apply predetermined pressure and time (from preliminary tests) to ensure stable, reproducible pellets.
• Binder: Add if necessary, in fixed proportion for calibration and test samples.
• Maintain consistent:
  • Particle size
  • Pressure
  • Pressing time

Reporting (Clause 10.1)

• Report concentration values directly from calibration graph or software.
• Also report:
  • Loss on Ignition (LOI)
  • Insoluble residue (per IS 4032:1985)

Summary Table for Pressed Pellet Preparation

flowchart TD
    A[Sample ~100g] --> B[Grinding to <20 microns]
    B --> C[Filling 15-20g in mould]
    C --> D[Press under controlled pressure & time]
    D --> E[Stable pressed pellet for XRF]
    E --> F[Analysis & Reporting]

This ensures reproducible, stable pellets for accurate XRF elemental analysis.

IS 12803 - Fusion Equipment Key Points

1. Fusion Equipment Requirements (Clause 6.2.2 & 6.2.2.1)

• Must melt sample + flux at ≥ 1200°C.
• Common heating systems:
  • Resistance heating
  • Induction heating
  • Gas heating

2. Fusion Procedure (Clause 9.1.2.1)

• Mix predetermined sample (ignited basis) + flux thoroughly in crucible.
• Fuse to obtain a clear, bubble-free melt.
• Cool in crucible or transfer immediately to a preheated (≈ 800°C) 95% Pt + 5% Au mould.
• Temperature & time depend on flux type and sample:flux ratio, predetermined to yield a transparent homogeneous glass bead.

3. Flux Additives

4. Instrument Stabilization (Clause 9.3.1)

• Keep XRF instrument ON per manufacturer’s stabilization time.
• Maintain:
  • Detector gas flow
  • Spectrometer chamber temperature
  • Room temperature
  • Chilling water temperature
    within prescribed limits for accuracy.

Summary Diagram of Fusion Process

flowchart TD
    A[Sample + Flux Mix] --> B[Fuse at ≥1200°C]
    B --> C{Clear Melt?}
    C -- Yes --> D[Cool in Crucible OR Transfer to Preheated Pt-Au Mould (≈800°C)]
    C -- No --> B
    D --> E[Obtain Transparent Homogeneous Glass Bead]

This ensures proper bead formation for XRF analysis as per IS 12803.

IS 12803: Key Points on Muffle Furnace & Fusion Procedure

Muffle Furnace (Clause 6.3)

• Operating temperature: Continuous operation up to 1200°C.
• Equipped with an indicating pyrometer for accurate temperature control.

Melting Equipment (Clause 6.2.2.1)

• Must melt sample + flux to ≥1200°C.
• Types: Resistance heating, induction heating, gas heating.

Fusion Procedure (Clause 9.1.2.1)

• Mix predetermined sample + flux thoroughly in a crucible.
• Fuse to get a clear, bubble-free melt.
• Cool in crucible or transfer immediately to a 95% Pt + 5% Au mould preheated to ~800°C.
• Temperature/time depends on flux and sample ratio (must be predetermined).

Flux Additives

• Potassium/sodium nitrate: For oxidizing atmosphere.
• Lanthanum oxide: Prevents bead cracking (glass former).
• Sodium bromide/lithium fluoride/bromide: Prevents bead sticking to Pt-Au crucible.

Reproducibility Limits (Clause 5)

Summary Diagram: Fusion Process

flowchart LR
    A[Sample + Flux] --> B[Mix thoroughly in crucible]
    B --> C[Fuse at ≥1200°C in Muffle Furnace]
    C --> D[Clear, bubble-free melt]
    D --> E{Cooling}
    E -->|Cool in

IS 12803 - X-ray Fluorescence Spectrometer (XRF) Key Points

1. Instrument Stabilization (Clause 9.3.1)

• Keep the XRF instrument switched on for the manufacturer's specified stabilization time.
• Maintain detector gas flow, spectrometer chamber temperature, room temperature, and chilling water temperature within prescribed limits for accuracy.

2. Measurement of XRF Intensities (Clause 9.3)

• XRF intensities must be measured under stable instrument conditions.
• Calibration curves relate element concentration to measured intensity.

3. Calibration Curves & Formula (Clause 9.3.4.1)

• Calibration curves are obtained via computer assistance.

• The relationship for each element is linear:

  [ C = m \times I + c ]

  Where:

  • ( C ) = concentration of element
  • ( I ) = measured XRF intensity
  • ( m ), ( c ) = calibration coefficients stored in the computer

Summary Table: Calibration Parameters

flowchart LR
    A[Start: XRF Instrument ON] --> B[Stabilize Instrument]
    B --> C[Maintain Temp & Gas Flow]
    C --> D[Measure XRF Intensity (I)]
    D --> E[Apply Calibration: C = m*I + c]
    E --> F[Output Element Concentration (C)]

Note: Always follow manufacturer’s detailed instructions for instrument conditions to ensure precise and reproducible results.

IS 12803 - Key Points on Sample Preparation and Calibration

1. Sample Preparation (Clause 9.1 & 6.2)

• Sample Preparation (9.1): Samples must be representative, homogeneous, and prepared to specified sizes.
• Equipment (6.2): Use calibrated, clean, and appropriate equipment (e.g., crushers, grinders) to avoid contamination or alteration.

2. Preparation of Standards for Calibration (Clause 9.2)

• Prepare standards with known concentration or properties.
• Use high-purity materials.
• Follow precise weighing and mixing procedures to ensure accuracy.

3. Measurements for Calibration (Clause 9.3.3)

• Calibration measurements must be repeated multiple times (usually 3+) to ensure consistency.
• Record values and calculate mean and standard deviation.
• Use calibration curves plotting known standard values vs. instrument response.

Typical Calibration Formula:

[ y = mx + c ]

• y: Instrument response
• x: Known concentration
• m: Slope of calibration curve
• c: Intercept

Sample Calibration Table (Example):

flowchart LR
    A[Sample Collection] --> B[Sample Preparation]
    B --> C[Standard Preparation]
    C --> D[Calibration Measurement]
    D --> E[Calibration Curve]
    E --> F[Instrument Calibration]

Summary: Ensure representative sampling, use calibrated equipment, prepare pure standards, and perform repeated measurements to develop accurate calibration curves as per IS 12803.

IS 12803 – Sample Preparation for XRF Analysis

Key Points from Clause 9.1 (Preparation of Sample)

• Sample Size: ~100 g initially.
• Grinding: Use a suitable mill to reduce particle size to < 20 microns.
• Pellet Formation: Take 15-20 g of ground sample.
• Molding: Fill into steel disc/ring or aluminium cup.
• Pressing: Apply predetermined pressure and time (from preliminary tests) to form stable pellets.
• Consistency: Keep particle size, pressure, and pressing time identical for calibration and test samples.
• Binder: Add a fixed proportion binder if required, consistently for calibration and test samples.

Important Specifications (Clause 6.2 & 9.2)

• Equipment: Use grinding mills and hydraulic presses suitable for uniform particle size and pellet formation.
• Standards: Prepare calibration standards similarly to test samples to ensure reproducibility.

Summary Table of Parameters

flowchart TD
    A[Start: 100g Sample] --> B[Grinding to < 20 microns]
    B --> C[Take 15-20g Ground Sample]
    C --> D[Add Binder (if required)]
    D --> E[Fill in Steel Disc/Aluminium Cup]
    E --> F[Press under predetermined Pressure & Time]
    F --> G[Stable Pellet for XRF Analysis]

Note: Consistency in sample preparation parameters is critical for reliable XRF results per IS 12803.

Pressed Pellet Technique as per IS 12803

Key Steps (Clause 9.1.1)

• Sample size: ~100 g, ground to <20 microns particle size.
• Pellet mass: 15-20 g of ground sample.
• Pellet holder: Steel disc/ring or aluminium cup.
• Pressure & time: Pre-determined by experiments to ensure reproducibility.
• Binder: Added in fixed proportion if required, same for calibration and test samples.
• Consistency: Particle size, pressure, and pressing time must be identical for calibration and test samples.

Equipment (Clause 6.2.1)

• Press capacity: Up to 50 tonnes.
• Pellet size: Suitable for X-ray fluorescence (XRF) analysis.

Reporting (Clause 10.1)

• Report concentration from calibration graph/computer.
• Report Loss on Ignition (LOI) and Insoluble Residue per IS 4032:1985 alongside.

Typical Parameters for Pressed Pellet Preparation

flowchart TD
    A[Sample ~100g] --> B[Grinding to <20 microns]
    B --> C[Take 15-20g ground sample]
    C --> D[Add binder (if required)]
    D --> E[Fill in steel disc/aluminium cup]
    E --> F[Press under controlled pressure & time]
    F --> G[Pressed Pellet for XRF analysis]

Summary: Control particle size, pressure (up to 50 tonnes), pressing time, and binder proportion strictly for reproducible XRF results. Report elemental concentration with LOI and insoluble residue.

Fused Bead Technique (IS 12803 - Clause 9.1.2)

• Sample Preparation:

  • Take sample as per IS 4032 (Loss on Ignition).
  • Mix predetermined ignited sample quantity with flux thoroughly in a crucible.

• Fusion Process:

  • Fuse mixture to obtain a clear, bubble-free melt.
  • Cool in crucible or cast immediately into a 95% Platinum + 5% Gold mould preheated to ~800℃.
  • Fusion temperature/time depends on flux type and sample-to-flux ratio (must be predetermined for transparent, homogeneous beads).

• Additives:

  • Potassium/Sodium nitrate: For oxidizing atmosphere during fusion.
  • Lanthanum oxide: Prevents bead cracking (glass former).
  • Sodium bromide/Lithium fluoride or Lithium bromide: Releasing agents to prevent bead sticking to crucible.

• Crucibles (Clause 6.2.2.2):

  • Use 95% Pt + 5% Au, Graphite, or Platinum-Rhodium crucibles.
  • Graphite is reusable but has shorter life than Pt-Au or Pt-Rh crucibles.

Typical Fusion Parameters (to be predetermined):

flowchart TD
    A[Sample + Flux] --> B[Fusion in Crucible]
    B --> C{Clear Melt?}
    C -- Yes --> D[Cool or Cast into Pt-Au Mold]
    C -- No --> B
    D --> E[Glass Bead for X-ray Analysis]

This technique ensures transparent, homogeneous glass beads for accurate X-ray fluorescence analysis.

IS 12803 — Measurement of XRF Intensities (Clause 9.3)

Key Points:

• Repetition: Measure XRF intensities for all elements 3 times using standard samples (9.1.1/9.1.2) and selected instrumental parameters (9.3.2).

• Calibration Equation:
  For element concentration ( x ) and measured intensity ( Y ), the basic relation is:
  [ Y = mx + c ]
  where:

  • ( m ) = slope (sensitivity)
  • ( c ) = intercept (background)

• Interference Correction:
  When interference from other elements exists, modify equation as:
  [ Y = mx + c + \sum (k_i \times C_i) ]
  where ( k_i ) = interference coefficient for element ( i ), and ( C_i ) = concentration of interfering element ( i ).

Typical Interferences (Table 9.3.4.2):

• Note: Interference coefficients vary by XRF analyzer model. Minor constituents generally have negligible interference.

• Computerized Calibration:
  Calibration coefficients ( m ) and ( c ) can be stored and used in software for automated corrections (9.3.4.1).

Summary Diagram of Measurement Process:

flowchart TD
    A[Prepare Standard Samples] --> B[Set Instrument Parameters]
    B --> C[Measure XRF Intensities (3 times)]
    C --> D[Apply Calibration: Y = mx + c]
    D --> E{Interference Present?}
    E -- Yes --> F[Apply Interference Corrections]
    E -- No --> G[Calculate Concentrations]
    F --> G

This approach ensures accurate elemental quantification by accounting for matrix effects and inter-element interference in XRF analysis per IS 12803.

IS 12803 — Key Formulas & Specifications for Calculations (Clause 9.3.4)

Calibration & Interference Correction

• Basic calibration equation:

  [ Y = mx + c ]

  where,

  • (Y) = XRF intensity (counts per second, CPS)
  • (x) = concentration of element
  • (m), (c) = calibration constants

• With interferences:

  [ Y = mx + c + \sum (k_i \times C_i) ]

  where,

  • (k_i) = interference coefficient for interfering element (i)
  • (C_i) = concentration of interfering element (i)

Typical Interferences in Cement XRF:

Calibration Protocol Highlights:

• Use standard reference samples daily to check XRF system performance.
• If drift in CPS occurs, recalibrate immediately.
• Confirm calibration correctness by analyzing a standard cement sample.

flowchart TD
    A[Start: Prepare Standards] --> B[Measure XRF Intensity (Y)]
    B --> C{Is there interference?}
    C -- Yes --> D[Apply interference correction: Y = mx + c + Σ(k_i*C_i)]
    C -- No --> E[Use basic calibration: Y = mx + c]
    D --> F[Calculate concentration (x)]
    E --> F
    F --> G[Check calibration daily]
    G --> H{Drift detected?}
    H -- Yes --> I[Recalibrate]
    H -- No --> J[Proceed with analysis]

Summary: Use the linear calibration with interference terms for accurate elemental quantification. Always verify calibration daily using standard samples as per IS 12803 Clause 9.3.3 & 9.3.4.