Methods of physical tests for hydraulic cement, Part 10: Determination of drying shrinkage
1988 Edition

Overview of Methods for Determining Drying Shrinkage - Essential Formulas and Specifications

1. Calculation of Drying Shrinkage (Clause 9.1):
Length measurements of specimens are taken at 7 and 35 days, and drying shrinkage percentage is calculated as:

[ \text{Drying Shrinkage (%) } = \frac{\Delta L}{L_0} \times 100 ]

Where:

• (\Delta L) = Mean length difference of three specimens (rounded to 0.01%)
• (L_0) = Effective gauge length

2. Allowed Weight Variations (Clause 4.2, Table 1):

3. Rounding Rules (Clause 0.4):
Final test results must be rounded off following IS 2-1960, preserving the indicated significant figures.

4. Equipment Requirements:
The flow table and its accessories should comply with IS 5512-1969 (Clause 4.5).

flowchart TD
    A[Measure specimen lengths at 7 & 35 days] --> B[Determine average length difference (ΔL)]
    B --> C[Compute drying shrinkage % = (ΔL / L0) × 100]

This section summarizes the fundamental requirements for drying shrinkage measurement according to the standard.

Scope of the Standard and Principal Specifications

Scope:
This portion of the standard describes the method to quantify length change caused by drying shrinkage in hardened cement paste, mortar, and concrete.

Essential Conditions and Procedures

• Testing Temperature:

  • Initial and subsequent measurements conducted at 27 ± 2°C
  • Specimens stored at 27 ± 2°C with 50 ± 5% relative humidity

• Specimen Handling:

  • Prevent moisture loss before the initial length measurement
  • Utilize length comparators for accurate length measurement
  • Maintain consistent specimen orientation during measurements

• Flow Table Compliance:

  • Must adhere to IS 5512 requirements

Fundamental Formula (Clause 9.1)

Drying shrinkage is computed as:

[ \text{Drying Shrinkage (%) } = \frac{\Delta L}{L_0} \times 100 ]

Where:

• (\Delta L) = Mean length change of three specimens (mm)
• (L_0) = Effective gauge length (mm)

Results are reported to the nearest 0.01%.

Summary Table

flowchart TB
    A[Prepare specimens] --> B[Store at 27 ± 2°C, 50 ± 5% RH]
    B --> C[Measure initial length (L0)]
    C --> D[Further storage]
    D --> E[Measure lengths at 7 & 35 days (L)]
    E --> F[Calculate drying shrinkage percentage]

Note: Follow rounding guidelines from IS 2-1960 for reporting.

Guidelines for Sample Selection and Specimen Preparation

Key Details:

• Specimen Design: Rectangular specimens prepared under standardized conditions.
• Batch Mixing: Mix constituents separately per proportions detailed in Clause 6.2; water content adjusted as per IS 4031 Part 7 to achieve flow between 100 and 115% (25 drops within 15 seconds).
• Mixing Method: Employ mechanical mixing according to IS 4031 Part 7, Clause 7.3.1.
• Specimen Quantity: Minimum of three specimens tested per batch.
• Measurement Intervals: Lengths measured at 7 days and 35 days.
• Shrinkage Calculation:

[ \text{Drying Shrinkage (%) } = \frac{\text{Average length difference between 7 and 35 days}}{\text{Effective gauge length}} \times 100 ]

• Values reported to the nearest 0.01%.

Summary Table: Sampling and Measurement

flowchart TD
    A[Batch mixing] --> B[Prepare 3 specimens]
    B --> C[Measure length at 7 days]
    C --> D[Measure length at 35 days]
    D --> E[Calculate average length difference]
    E --> F[Compute drying shrinkage percentage]
    F --> G[Report findings]

This procedure ensures precise and standardized sampling according to the standard.

Specified Temperature and Humidity Conditions for Testing

Highlights:

• Temperature is maintained strictly at 27 ± 2°C during moulding, curing, and drying.
• Relative humidity varies depending on the process:
  • Curing: ≥ 90%
  • Drying cabinet: 50 ± 5%
  • Moulding: 65 ± 5%
• Temperature and humidity should be recorded at least twice daily in drying cabinets.
• Air circulation must be consistent within drying cabinets to promote uniform evaporation.

flowchart LR
    A[Moist Room] -->|27 ± 2°C, RH≥90%| B[Curing specimens]
    C[Control Cabinet] -->|27 ± 2°C, RH=50 ± 5%| D[Specimen drying]
    E[Moulding Room] -->|27 ± 2°C, RH=65 ± 5%| F[Mould preparation]

Adhering to these conditions is vital for reproducible and accurate test results.

Synopsis of Required Apparatus and Equipment Standards

Major Equipment Specifications:

• Flow Table and Accessories: Must comply with IS 5512-1969 for hydraulic cement and pozzolanic materials.
• Length Comparator: Device for measuring length changes in hardened cement paste, mortar, and concrete specimens.
• Specimen Storage: Controlled environment cabinet at 27 ± 2°C and 50 ± 5% RH to prevent moisture loss.
• Measurement Conditions: Length comparator, specimens, and reference bar maintained at 27 ± 2°C during measurements.

Formulas (Clause 9.1):

Drying Shrinkage (%) after specified curing periods:

[ \text{Drying Shrinkage} = \frac{\Delta L}{L_0} \times 100 ]

• (\Delta L): Average length difference of three specimens (mm)
• (L_0): Effective gauge length (mm)
• Report figures to nearest 0.01%

Measurement Procedure (Clause 8.2):

• Initial length recorded after removing specimens from water.
• Protect specimens from moisture loss prior to initial measurement.
• Final length measured after 28 days under controlled conditions.
• Ensure specimens are positioned identically in the length comparator for each measurement.

Rounding Instructions:

• Follow rounding standards from IS 2-1960.
• Maintain the prescribed number of significant digits.

flowchart TD
    A[Specimen preparation] --> B[Store at 27 ± 2°C, 50 ± 5% RH]
    B --> C[Measure initial length]
    C --> D[Store for 28 days]
    D --> E[Measure final length]
    E --> F[Calculate drying shrinkage]

Refer to IS 5512-1969 and associated standards for detailed dimensions and tolerances.

Essential Instructions for Preparing Moulds

Mould Specifications

• Cross-sectional dimensions: 25 mm × 25 mm with an internal length of 282 mm as per IS 10086-1982.
• Apply a thin film of mineral oil to the mould surface before casting.
• Stainless steel or corrosion-resistant metal inserts with knurled ends are used to establish an effective gauge length of 250 mm.
• Inserts must be clean and free from oil.

Materials and Mixing (Clause 6.3)

• Dry ingredients mixed separately, following proportions in Clause 6.2.
• Water volume adjusted according to IS 4031 Part 7 to achieve a flow between 100 and 115% (25 drops in 15 seconds).
• Mechanical mixing practiced as described in IS 4031 Part 7 (Clause 7.3.1).

Environmental Controls (Clause 3.1)

• Maintain a temperature of 27 ± 2°C for the moulding area, materials, and mixing water.
• Relative humidity maintained at 65 ± 5%.

Summary Table:

flowchart TD
    A[Mix dry materials] --> B[Add water and mix mechanically]
    B --> C[Prepare moulds with mineral oil coating]
    C --> D[Position reference inserts (250 mm gauge)]
    D --> E[Cast specimens]

This ensures specimens are consistently prepared as per the standard.

Guidance on Mortar Preparation for Testing

Material Ratios (Clause 6.2)

• Cement to Standard Sand ratio: 1:3 by weight
• Standard sand should comply with IS 650 specifications.

Mixing Conditions (Clause 6.1)

• Use clean and uncontaminated equipment.
• Maintain water and ambient temperatures at 27 ± 2°C.
• Water used should be potable or distilled.

Mould Preparation (Clause 5.1)

• Moulds coated lightly with mineral oil.
• Stainless steel or corrosion-resistant metal inserts with knurled heads to set 250 mm gauge length.

Moulding Procedure (Clause 7.1)

• Mix thoroughly and place mortar in moulds in two layers.
• Compact each layer by pressing with thumbs and forefingers, ensuring complete filling.
• Level and smooth the top surface using a trowel.
• Employ rubber gloves during handling to prevent contamination.

Summary Table: Mortar Mix and Handling

flowchart TD
    A[Combine cement and standard sand (1:3)] --> B[Mix with water at 27 ± 2°C]
    B --> C[Prepare moulds coated with mineral oil and inserts]
    C --> D[Fill moulds in two layers, compact manually]
    D --> E[Level and finish surface]
    E --> F[Specimen ready for curing and testing]

This ensures uniform and reproducible mortar specimens.

Procedures and Requirements for Casting Specimens

• Mixing Ratios (Clause 6.3):

  • Use dry materials per proportions in Clause 6.2.
  • Water dosage adjusted according to IS 4031 Part 7 to yield a mortar flow of 100–115% with 25 drops in 15 seconds (as per flow table test).
  • Mechanical mixing as outlined in IS 4031 Part 7, Clause 7.3.1.

• Mould Dimensions (Clause 4.6):

  • Beam mould cross-section: 25 mm × 25 mm.
  • Internal length: 282 mm, per IS 10086-1982.
  • Effective gauge length between reference inserts: 250 mm.

• Environmental Conditions (Clause 3.1):

  • Temperature maintained at 27 ± 2°C for moulding room, materials, and water.
  • Relative humidity controlled at 65 ± 5%.

• Mould Preparation (Clause 5.1):

  • Moulds receive a thin mineral oil coating to avoid adhesion.
  • Stainless steel or corrosion-resistant metal inserts with knurled heads used for gauge length.

Summary Table

flowchart TD
    A[Dry materials] --> B[Mix with water mechanically]
    B --> C[Prepare moulds coated with mineral oil]
    C --> D[Insert reference inserts]
    D --> E[Cast specimens]

This ensures compliance with the standard’s moulding requirements.

Step-by-Step Testing Methodology

1. Specimen Preparation and Mixing (Clause 6.3):

• Dry materials mixed separately according to Clause 6.2 proportions.
• Water addition as per IS 4031 Part 7 to attain a flow between 100–115% (25 drops in 15 seconds).
• Mechanical mixing performed as per IS 4031 Part 7 (7.3.1).

2. Length Measurement (Clause 8.2):

• Initial length measured immediately after water removal using a length comparator.
• Specimens and comparator kept at 27 ± 2°C.
• Specimens protected against moisture loss before measurement.
• Specimens stored at 27 ± 2°C and 50 ± 5% RH.
• Subsequent length measurement carried out after 28 days under identical temperature conditions.
• Specimens positioned consistently in the comparator during all measurements.

3. Rounding (Clause 0.4):

• Final results rounded off following IS 2-1960 rules.
• Maintain the specified significant figure count.

Length Change Formula

[ \text{Length Change (%) } = \frac{L_{28} - L_0}{L_0} \times 100 ]

where:

• (L_0) = initial length
• (L_{28}) = length after 28 days

Environmental Conditions Summary

flowchart TD
    A[Mix ingredients] --> B[Check mortar flow]
    B --> C[Cast specimens]
    C --> D[Store at 27 ± 2°C, 50 ± 5% RH]
    D --> E[Initial length measurement]
    E --> F[Store for 28 days]
    F --> G[Final length measurement]
    G --> H[Calculate length change percentage]

This procedure ensures accurate determination of drying shrinkage.

Calculation Method for Drying Shrinkage

Formula (Clause 9.1)

The drying shrinkage percentage is determined by:

[ \text{Drying Shrinkage (%) } = \frac{\Delta L}{L_0} \times 100 ]

Where:

• (\Delta L = L_7 - L_{35}) is the mean length difference between measurements at 7 and 35 days (in mm).
• (L_0) is the effective gauge length in mm.

Summary of Steps:

• Measure the length of three specimens at 7 days and then at 35 days.
• Calculate the average length difference to the closest 0.01% of the gauge length.
• Present this value as the drying shrinkage result.

Specifications:

• Specimens are rectangular and prepared as per the standard.
• Testing environment involves controlled temperature and humidity.
• Gauge length is precisely measured to ensure accuracy.

Practical Recommendations:

• Use a micrometer or length comparator for precise measurement.
• Ensure specimens are cured and dried under specified conditions.
• Averaging results over three specimens enhances reliability.

flowchart TD
    A[Prepare 3 specimens] --> B[Measure length at 7 days]
    B --> C[Measure length at 35 days]
    C --> D[Calculate length difference (ΔL)]
    D --> E[Compute drying shrinkage % = (ΔL / L0) × 100]
    E --> F[Report average shrinkage]

This ensures consistent and standardized drying shrinkage evaluation.

Guidelines for Reporting Test Outcomes

Rounding of Results (Clause 0.4):

• Final values must be rounded according to IS 2-1960, retaining the specified number of significant digits.

Drying Shrinkage Calculation (Clause 9.1):

• Compute average length change of three specimens between 7 and 35 days:

[ \text{Drying Shrinkage (%) } = \frac{\sum (\Delta L)}{3 \times L_0} \times 100 ]

where:

• (\Delta L) is length change per specimen (mm)

• (L_0) is effective gauge length (mm)

• Report results to the nearest 0.01%.

Measurement Conditions (Clause 8.2):

• All length measurements taken at 27 ± 2°C.
• Specimens stored in controlled conditions at 27 ± 2°C and 50 ± 5% RH.
• Length comparator used with consistent specimen orientation.

Permissible Weight Variations (Table 1, Clause 4.2):

Reporting Workflow Diagram

flowchart TD
    A[Measure initial length at 27 ± 2°C] --> B[Store specimens at 27 ± 2°C, 50 ± 5% RH]
    B --> C[Measure length at 7 and 35 days]
    C --> D[Calculate average shrinkage percentage]
    D --> E[Round results as per IS 2-1960]

This ensures standardized and accurate reporting of drying shrinkage values.