Specification for pressure meter for determination of air content of freshly mixed concrete

IS 9799: Scope and Key Specifications

• Scope: Specifies requirements for the pressure meter used to determine the air content in freshly mixed concrete.

• Rounding Off Values: As per IS 2-1960, final test or analysis values must be rounded to the same number of significant digits as specified in the standard.

• International Coordination: The standard aligns with international practices while considering Indian field conditions.

• Measuring Bowl Specifications (Clause 2.2):
  The measuring bowl must be a flanged cylindrical bowl made of steel, cast iron, brass, or other hard metals resistant to cement attack. Surfaces must be machine-finished.

This ensures the bowl capacity matches the aggregate size for accurate air content measurement.

flowchart LR
    A[Fresh Concrete Sample] --> B[Measuring Bowl]
    B --> C[Pressure Meter]
    C --> D[Air Content Determination]

Summary: IS 9799 defines equipment specs and procedures for air content testing in concrete, emphasizing precision and material standards.

IS 9799: Parts and Accessories for Pressure Meter (Air Content of Concrete)

Key Specifications (Clause 2.2)

• Measuring Bowl:
  • Material: Steel, cast iron, brass, or other hard metals resistant to cement attack.
  • Finish: Outer rim, flange upper surface, and interior must be machine-finished.
  • Shape: Flanged cylindrical bowl.

Nominal Capacity of Measuring Bowl (related to max aggregate size)

Notes:

• Capacity ensures representative sampling for air content measurement.
• Proper material and finish prevent contamination and wear.

flowchart TD
    A[Concrete Sample] --> B[Measuring Bowl]
    B --> C{Max Aggregate Size}
    C -->|38 mm| D[Capacity 0.005 m³]
    C -->|75 mm| E[Capacity 0.01 m³]
    C -->|150 mm| F[Capacity 0.10 m³]

Use this table and specifications to select the correct measuring bowl for accurate air content determination per IS 9799.

IS 9799: Measuring Bowl Specifications & Key Details

Measuring Bowl (Clause 2.2)

• Material: Steel, cast iron, brass, or other hard, cement-resistant metals.
• Finish: Outer rim, flange upper surface, and interior surfaces must be machine-finished.
• Shape: Flanged cylindrical bowl.
• Nominal Capacity vs. Maximum Aggregate Size:

Calibration Cylinder (Clause 2.4)

• Volume = 3% to 6% of measuring bowl volume.
• Made from No. 16 gauge brass tubing.
• One end sealed with a 6 mm thick brass disc.

Conical Cover Assembly (Clause 2.3)

• Material: Steel, cast iron, brass, or other non-corrodible hard metals.
• Interior surface slope ≥ 30° from flange surface.
• Designed for pressure-tight, rigid fit with measuring bowl.

Summary Diagram

graph TD
  A[Measuring Bowl]
  B[Flanged Cylindrical Shape]
  C[Machine Finished Surfaces]
  D[Capacity per Aggregate Size]
  E[Calibration Cylinder]
  F[3-6% Bowl Volume]
  G[Conical Cover Assembly]
  H[≥30° Interior Slope]
  I[Pressure-tight Fit]

  A --> B
  A --> C
  A --> D
  A --> E
  A --> G
  E --> F
  G --> H
  G --> I

This ensures accurate volume measurement for concrete mix testing per IS 9799.

IS 9799 - Conical Cover Assembly Key Points

1. Material & Geometry (Clause 2.3)

• Material: Steel, cast iron, brass, or other hard, non-corrodible metals.
• Inclination: Interior surfaces inclined ≥ 30° from flange surface.
• Design: Outer rim, flange lower surface, and sloping interior ensure a pressure-tight, rigid assembly with the measuring bowl.

2. Stand Pipe Specifications (Clause 2.3.1)

• Type: Graduated precision bore glass tube or uniform bore metal tube with glass water gauge.
• Graduations:
  • Range in air content (%)
  • Divisions ≥ 2 mm wide
  • Accuracy: ± 0.1%
• Diameter: Sized so water column lowers enough to measure air content down to 0.1% under normal pressure.
• Pressure Gauge: Connected above water column to show applied pressure.

3. Accessories & Sealing (Clause 2.3.2)

• Valves: Air vent valve, water inlet valve, and water bleed petcock.
• Clamping: Wing nut type clamps recommended for pressure-tight seal.
• Seal: Preferably O-rings to avoid air entrapment.

Typical Dimensions (Fig. 1 - 0.005 m³ Capacity)

• Refer to IS 9799 Fig. 1 for detailed dimensions of the conical cover and measuring bowl.

Summary Table of Key Specs

flowchart TD
    A[Measuring Bowl] --> B[Conical Cover Assembly]
    B --> C[Stand Pipe with Graduations]
    B --> D[Air Vent Valve]
    B --> E[Water Inlet Valve]
    B --> F[Water Bleed Petcock]
    B --> G[Wing Nut Clamps + O-ring

IS 9799: Calibration Cylinder Key Details

• Volume:
  Calibration cylinder volume = 3% to 6% of measuring bowl volume.
  For example, if bowl volume = 0.005 m³,
  Calibration cylinder volume = 0.00015 m³ to 0.0003 m³ (150 to 300 cm³).

• Material & Construction:

  • Made from No. 16 gauge brass tubing.
  • One end closed with a 6 mm thick brass disc soldered firmly.

• Spring:

  • A coil spring holds the calibration cylinder in position (Clause 2.5).

• Stand Pipe (Clause 2.3.1):

  • Graduated glass or metal tube with water gauge.
  • Graduations: minimum 2 mm wide, accuracy ±0.1%.
  • Internal diameter chosen to measure air content as low as 0.1%.
  • Pressure gauge connected above water column to show applied pressure.

Quick Reference Table for Calibration Cylinder Volume

Summary Diagram of Calibration Cylinder Setup

flowchart TB
    A[Measuring Bowl] --> B[Conical Cover Assembly]
    B --> C[Calibration Cylinder]
    C --> D[Coil Spring (holds cylinder)]
    B --> E[Stand Pipe (graduated)]
    E --> F[Water Column + Pressure Gauge]

This ensures precise calibration and measurement of air content in fresh concrete as per IS 9799.

IS 9799 Key Specifications for Pressure Gauge:

• Diameter: 75 mm (Clause 2.6)
• Range: Twice the normal working pressure (e.g., 0.05 to 0-20 N/mm² used satisfactorily)
• Graduation: Suitable scale with divisions not less than 2 mm wide and accuracy of 0.1% (Clause 2.3.1)
• Connection: Gauge connected to air chamber above water column in the standpipe assembly (Clause 2.3.1)

Important Notes:

• The pressure gauge is part of the pressure meter assembly used to determine air content in fresh concrete.
• The standpipe is a precision bore glass tube or metal tube with a glass water gauge, graduated in % air content.
• The water column displacement under pressure correlates with air content measurement up to 0.1%.

Summary Table

flowchart LR
    A[Air Chamber] -->|Pressure| B[Pressure Gauge (75 mm)]
    A --> C[Standpipe with Water Column]
    C --> D[Graduated Scale (% Air Content)]

This setup ensures accurate air content measurement in concrete per IS 9799.

IS 9799: Key Specifications for Tamping Rod

• Tamping Rod Dimensions (Clause 2.7.2):

  • Diameter: 16 mm
  • Length: 230 mm
  • Cross-section: Circular
  • One end rounded
  • Material: Steel conforming to IS 7320-1974 (Concrete slump test tamping rod specification)

• Purpose: Used for compacting concrete in slump tests to ensure uniformity.

• Additional Notes:

  • The tamping rod must be straight and smooth to avoid damaging the concrete sample.
  • Rounded end prevents aggregate damage during tamping.

Related Tools (for context):

Measuring Bowl Capacity (Clause 2.2):

flowchart LR
    A[Tamping Rod] --> B{Diameter: 16 mm}
    A --> C{Length: 230 mm}
    A --> D{Rounded End}
    A --> E[Steel, IS 7320-1974]

This tamping rod ensures proper compaction during concrete slump testing as per IS 9799 requirements.

IS 9799 Key Specifications for Mallet and Trowel:

• Trowel (Clause 2.7.1):

  • Standard brick mason's type trowel.

• Mallet (Clause 2.7.3):

  • Made of wood with a rubber or rawhide head.
  • Weight: 250 to 500 g, depending on bowl capacity.
  • Refer to Fig. 2 for dimensions (all in mm).

• Additional Tools:

  • Tamping Rod (Clause 2.7.2):
    • Steel, circular cross-section, 16 mm diameter, 230 mm length, rounded end.
    • As per IS 7320-1974.

• Pump (Clause 2.7.6):

  • Foot pump or pressure bulbs for required pressure.

• Rubber Padding:

  • Thickness: 3 mm to be pasted as specified.

Summary Table:

This ensures proper handling and compaction during concrete slump testing as per IS 9799.

IS 9799: Marking and Identification - Key Points

• Clause 3.1 Requirements:

  • Each apparatus component must be clearly and indelibly marked.
  • Marking must not interfere with apparatus performance.
  • Marking must include:
    • Manufacturer's name or registered trademark (or both)
    • Date of manufacture

• Rounding Off Results (IS 2-1960):

  • Final test or analysis values must be rounded off according to IS 2-1960.
  • Number of significant digits retained should match the specified value in IS 9799.

Summary Table for Marking Requirements

Practical Tips:

• Use durable labels or embossing resistant to environmental effects.
• Position markings where they do not affect apparatus function or safety.
• Follow IS 2 for rounding test results to maintain standard compliance.

flowchart TD
    A[Component] --> B[Marking]
    B --> C[Manufacturer Name/Trademark]
    B --> D[Date of Manufacture]
    B --> E[Non-interfering with Performance]

IS 9799: Assembly and Operation Key Points

1. Conical Cover Assembly (Clause 2.3)

• Material: Steel, cast iron, brass, or other hard, non-corrodible metals.
• Design: Flanged cover with interior surfaces inclined ≥ 30° from flange surface.
• Fit: Outer rim, lower flange surface, and sloping interior ensure a rigid, pressure-tight seal with the measuring bowl.

2. Stand Pipe for Air Content Measurement (Clause 2.3.1)

• Type: Graduated precision bore glass tube or metal tube with glass water gauge.
• Graduations: Percent air content, divisions ≥ 2 mm wide, accuracy ±0.1%.
• Diameter: Sized to measure air content down to 0.1% under normal pressure.
• Pressure Indication: Pressure gauge connected above water column.

3. Accessories (Clause 2.7.6)

• Pump: Foot pump or pressure bulbs to develop required pressure.

4. Additional Specifications

• Rubber Padding: 3 mm thick for sealing.
• Tools: Wooden mallet and steel strike-off bar (dimensions per figures).

Typical Pressure Meter Dimensions (Fig. 1)

• Capacity: 0.005 m³
• Refer to IS 9799 Fig. 1 for dimensional details.

Summary Diagram of Assembly:

graph TD
  A[Measuring Bowl] --> B[Conical Cover Assembly]
  B --> C[Flanged Cover with 30° Incline]
  B --> D[Stand Pipe with Water Gauge]
  D --> E[Pressure Gauge on Air Chamber]
  F[Foot Pump or Pressure Bulb] --> E
  G[Rubber Padding] --> B

This ensures precise air content measurement in concrete by maintaining pressure tightness and accurate water column readings under pressure.

IS 9799: Calibration and Accuracy of Pressure Meter

Key Specifications:

• Calibration Cylinder (Clause 2.4):

  • Volume = 3% to 6% of measuring bowl volume.
  • Material: No. 16 gauge brass tubing.
  • One end sealed with a 6 mm thick brass disc.

• Stand Pipe (Clause 2.3.1):

  • Graduated precision bore glass tube or uniform bore metal with glass water gauge.
  • Graduations in % air content, divisions ≥ 2 mm wide.
  • Accuracy: ±0.1% air content.
  • Internal diameter sized to measure air content down to 0.1% under normal pressure.
  • Pressure gauge connected above water column to indicate applied pressure.

Accuracy & Rounding (Clause 0.5):

• Results rounded per IS:2-1960.
• Significant figures match those of the specified value.

Calibration Accuracy Formula (Conceptual):

[ \text{Air Content} (%) = \frac{V_{\text{air}}}{V_{\text{total}}} \times 100 ]

Where:

• (V_{\text{air}}) = Volume of air measured (from calibration cylinder)
• (V_{\text{total}}) = Total volume of measuring bowl

Summary Diagram: Calibration Setup

flowchart LR
    A[Measuring Bowl] --> B[Calibration Cylinder (3-6% volume)]
    B --> C[Stand Pipe with Graduations]
    C --> D[Water Column & Pressure Gauge]
    D --> E[Air Content Measurement (±0.1% accuracy)]

This ensures precise air content measurement in fresh concrete per IS 9799.

IS 9799: Maintenance and Care – Key Specifications

• Measuring Bowl (Clause 2.2):
  • Material: Steel, cast iron, brass, or hard metal resistant to cement attack.
  • Finish: Machine-finished outer rim, flange upper surface, and interior.
  • Nominal Capacity vs. Max Aggregate Size:

• Cover & Stand Pipe (Clause 2.3.1):

  • Stand pipe: Graduated precision bore glass or uniform metal bore with glass water gauge.
  • Graduation: Percent air content, divisions ≥ 2 mm wide, accuracy ±0.1%.
  • Internal diameter designed for water column drop measurable to 0.1% air content under normal pressure.
  • Pressure gauge connected to air chamber for applied pressure monitoring.

• Maintenance Tips:

  • Keep measuring bowl clean and free from cement buildup.
  • Ensure stand pipe and water gauge are clear and calibrated regularly.
  • Check pressure gauge accuracy before testing.

flowchart LR
    A[Measuring Bowl] --> B[Fill with Concrete]
    B --> C[Cover with Stand Pipe]
    C --> D[Apply Pressure]
    D --> E[Read Air Content on Gauge]
    E --> F[Record & Maintain Equipment]

This ensures precise air content measurement and longevity of equipment per IS 9799.

Rounding Off Numerical Values as per IS 9799 & IS 2-1960

• Final test or analysis values must be rounded off according to IS: 2-1960 rules.
• The number of significant figures in the rounded value should match the specified value in IS 9799.
• Typically, rounding follows:
  • If the digit after the last significant figure is <5, drop it.
  • If the digit is >5, round up.
  • If exactly 5, round to the nearest even number (banker's rounding).

Measuring Bowl Capacities (Clause 2.2)

Summary

• Use IS: 2-1960 for rounding rules.
• Retain significant figures as per standard values.
• Measuring bowl capacity depends on aggregate size (see table above).

flowchart LR
    A[Observed/Calculated Value] --> B{Round off as per IS:2-1960}
    B --> C[Match Significant Figures of Specified Value]
    C --> D[Final Rounded Value]

This ensures consistency and accuracy in reporting test results.