Cement fineness is an important quality characteristic that can affect hydration, strength development, and other performance properties. A Negative Pressure Cement Fineness Tester uses controlled airflow and negative pressure to determine cement fineness by sieve analysis.

I. What Is a Negative Pressure Cement Fineness Tester?

A Negative Pressure Cement Fineness Tester is a laboratory instrument used to determine the fineness of cement by measuring the amount of material retained on a specified test sieve. A 45 μm (No. 325) sieve is commonly used for international testing applications.

ASTM C430-26 specifies the determination of hydraulic cement fineness using a 45 μm sieve, while ASTM C1891-25 specifically covers air-jet sieving of hydraulic cement using a 45 μm sieve.

II. How Does It Work?

How Does It Work?

The working principle can be summarized in four main stages:

1. Cement Sample Is Placed on the Test Sieve

A specified quantity of cement is accurately weighed and placed evenly into the test sieve. The sieve is then securely covered to prevent material loss during testing.

2. Negative Pressure Is Created

The vacuum system generates a controlled negative pressure inside the testing system. This creates an airflow through the test sieve and helps prevent fine cement particles from simply remaining on the mesh surface.

3. Air Jet Separates the Particles

An air nozzle directs airflow across the underside or surface of the sieve. The airflow helps disperse and separate cement particles.

Particles smaller than the sieve aperture can pass through the mesh and are carried away by the airflow, while larger particles remain on the sieve.

For example, when a 45 μm sieve is used, the test evaluates the amount of cement retained on the 45 μm sieve. ASTM C1891-25 specifically defines air-jet sieving for hydraulic cement using this sieve size.

4. The Residue Is Weighed

After the specified test time, the instrument stops or the test is stopped according to the applicable procedure. The material retained on the sieve is collected and weighed.

The percentage of sieve residue can then be calculated:

Fineness (%) = (Mass of Residue / Original Sample Mass) × 100

A lower residue generally indicates that a greater proportion of the cement particles are finer than the selected sieve aperture.

III. Advantages of Negative Pressure Sieve Analysis

The combination of airflow and negative pressure helps improve particle dispersion and reduce the influence of manual operation. It can provide fast testing, consistent operating conditions, good repeatability, and efficient collection of fine particles.

The method is particularly suitable for routine cement quality control and laboratory testing.

IV. Negative Pressure Sieve Method vs. Blaine Method

The negative pressure sieve method should not be confused with the Blaine air-permeability method. The sieve method determines the proportion of cement retained on a specified sieve, while the Blaine method determines the specific surface area of cement. They are different testing methods and require different instruments.

V. Applications

Negative pressure cement fineness testers are widely used in:

Cement manufacturing plants;

Construction material laboratories;

Quality control laboratories;

Concrete and mortar laboratories;

Universities and research institutions;

Cement inspection facilities.

VI. How to Improve Test Accuracy

Several factors can affect cement fineness test results:

Use a properly calibrated test sieve.

Accurately weigh the cement sample.

Keep the sieve clean and free from blockage.

Maintain the specified negative pressure.

Use the correct test duration.

Ensure the sieve and connections are properly sealed.

Prevent moisture and contamination of the cement sample.

Follow the applicable testing standard consistently.

ASTM C430-26 specifically addresses sieve calibration and cleaning in addition to the sieve, nozzle, and pressure-gauge requirements.

VII. Reference Standards

Relevant international standards include:

ASTM C430-26 — Standard Test Method for Fineness of Hydraulic Cement by the 45-μm (No. 325) Sieve

ASTM C1891-25 — Standard Test Method for Fineness of Hydraulic Cement by Air Jet Sieving at 45-μm (No. 325)

VIII. Conclusion

A Negative Pressure Cement Fineness Tester uses a combination of test sieving, controlled airflow, and negative pressure to separate cement particles according to size. By reducing dependence on manual sieving and providing controlled testing conditions, the instrument can support efficient and repeatable cement fineness testing.

For cement laboratories and quality-control departments, selecting the appropriate sieve, maintaining stable negative pressure, keeping the test sieve clean, and following the applicable standard are essential for obtaining reliable results.