AASHTO T 192-2023
Fineness of Hydraulic Cement by the 45-μm (No. 325) Sieve

Standard No.

AASHTO T 192-2023

Release Date

2023

Published By

American Association of State Highway and Transportation Officials  US  /  AASHTO

Latest

AASHTO T 192-2023

Introduction

Standard Overview and Technical Background

AASHTO T 192-23, "Standard Test Method for Fineness of Hydraulic Cement Using the 45-μm (No. 325) Sieve," is a technical standard newly revised in 2023 and maintains technical consistency with ASTM C430-17. This standard specifically addresses the use of the 45-μm sieve for the determination of fineness of hydraulic cement, establishing standardized testing procedures and quality control requirements.

Fineness, a key indicator of cement quality control, directly affects cement hydration rate, strength development, and workability. The 45-μm sieving method quantifies the amount of residual cement particles, providing important data support for cement production process optimization and concrete mix design. The 2023 edition of the standard incorporates technical revisions to screen calibration and cleaning frequency, further improving the accuracy and comparability of test results.

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Technical requirements for instruments and equipment

The standard has extremely strict requirements on the specifications of test instruments to ensure the repeatability of test results.

Instrument Type	Specifications	Conforms to Standards	Key Parameters
Screen Frame	Circular metal frame, water corrosion resistant	-	Diameter 51±6mm (woven mesh) or 76±6mm (electroformed sheet), depth 76±6mm
Woven Metal Screen	45μm stainless steel AISI 304 type	ASTM E11	Mesh size 45μm, corresponding to No. 325 sieve
Electroformed Sieve	45μm Reinforced Nickel Sieve	ASTM E161	71±2 holes/cm (180±5 holes/inch)
Spray Nozzle	Corrosion-resistant metal structure	-	17.5mm inner diameter, 17 0.5mm holes, flow rate 1500-3000g/min@69±3kPa
Pressure Gauge	Minimum diameter 76mm	-	Graduation 7kPa, maximum capacity 207kPa, accuracy ±2kPa@69kPa

Screen installation requirements are particularly critical: the woven metal screen should be installed without twisting, looseness, or wrinkles, and the welded joints must be smooth and flat. The connection between the electroformed screen and the frame must be made of waterproof material to ensure smoothness. These details directly affect the accuracy of cement particle retention during the test.

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Detailed Explanation of the Screen Calibration Procedure

The standard requires the use of NIST Standard Sample No. 114 or No. 46h for screen calibration to ensure traceability of test results. The calibration procedure includes:

Calibration Example Analysis: Place 1.000g of the standard sample on a clean and dry 45μm sieve and test according to the procedure in Section 5. The sieve correction factor is calculated as follows: Correction factor = (Test residue - Specified residue) / Test residue × 100%. As shown in Table 1, the standard sample residue is 12.2%, corresponding to a theoretical residue of 0.122g per 1g sample; the measured residue on the calibrated sieve is 0.093g; the difference is +0.029g; the correction factor = +0.029/0.093 × 100 = +31.2%. Important: The correction factor is a multiplicative factor, not a fixed value. The actual correction amount in the test is proportional to the residue. This relative correction method better reflects the physical nature of the sieving process and avoids the systematic errors that may be introduced by absolute correction.

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Test operation process specification

The standard test procedure contains strict operating steps and time control:

1. Sample preparation: Accurately weigh 1.000g cement sample and place it on a clean and dry 45μm sieve
2. Wetting treatment: Thoroughly wet the sample with a gentle stream of water
3. Pressure adjustment: Adjust the spray nozzle pressure to 69±4kPa (10±0.5psi
4. Sieve washing: Move the sieve in a horizontal circle under the spray at a rate of 1 time/second for 1 minute
5. Final rinse: Immediately rinse once with approximately 50cm³ of distilled or deionized water
6. Drying and Weighing: Gently blot the underside of the screen dry. Dry in an oven or on a hot plate. After cooling, brush off any residue and weigh using an analytical balance with an accuracy of 0.0005g.

During this operation, the bottom of the spray nozzle should extend approximately 12mm below the top of the screen frame to ensure even coverage. During the drying phase, care should be taken to avoid overheating, which may soften the solder. Oven drying at 110°C for 12.5 ± 2.5 minutes is recommended.

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Screen cleaning and maintenance requirements

The standard has clear provisions on the cleaning frequency of different types of screens:

Screen type	Cleaning frequency	Calibration frequency	Cleaning method
Woven metal screen	≤5 times after measurement	≤100 times after measurement	Ultrasonic cleaning or hot cleaning solution immersion
Electroformed screen (71 holes/cm)	≤3 times after measurement		Avoid ultrasonic cleaning, hot cleaning solution immersion is recommended

Acceptable cleaning procedures include: using a low-power ultrasonic bath with a maximum power input of 150W and an appropriate laboratory cleaning solution at room temperature for 10-15 minutes; or soaking in an appropriate laboratory cleaning solution near boiling point, followed by rinsing. Avoid using dilute hydrochloric acid or acetic acid solutions for cleaning; use only soap or detergent-based solutions.

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Calculation Results and Accuracy Analysis

The cement fineness is calculated to an accuracy of 0.1% using the following formula:

F = 100 - Rc

Rc = Rs × (100 + C)/100

Where: F = Corrected percentage passing a 45μm sieve; Rc = Corrected residual percentage; Rs = The amount of sample remaining on a 45μm sieve (g); and C = Sieve Correction Factor.

Calculation Example: Sieve correction factor C = +31.2%, test sample residue Rs = 0.088g, correction residue Rc = 0.088×(100+31.2)/100 = 11.5%, pass percentage F = 100 - 11.5 = 88.5%.

The standard has clear requirements for test accuracy: the multi-laboratory accuracy for products of ordinary fineness is ±0.75% (1s), and the results between different laboratories should be consistent within ±2.1% at a 95% confidence level; the multi-laboratory accuracy for products of high fineness is ±0.50% (1s), and the inter-laboratory consistency is ±1.4%. Due to the lack of suitable reference materials, the standard does not make a statement on deviation.

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Quality Control and Implementation Recommendations

Based on AASHTO R18 quality management system requirements, the laboratory should establish a complete quality control procedure:

1. Personnel Qualification: Operators must receive professional training and be familiar with the details of standard procedures and instrument characteristics
2. Equipment Calibration: Establish a regular plan for screen calibration and pressure gauge verification to ensure measurement traceability
3. Environmental Control: The test environment should avoid vibration and airflow interference, and the water temperature should be kept stable
4. Complete Records: Record the sample information, operating conditions and calculation results of each test in detail
5. Comparison Verification: Regularly participate in inter-laboratory comparisons to verify the accuracy and consistency of test results

During implementation, special attention should be paid to the following: The condition of the screen directly affects test results. Records of screen usage should be maintained to track performance changes after each cleaning and calibration. Strict control of spray pressure and time is key to ensuring test reproducibility. Sample representativeness is crucial for reliable results, and sampling and splitting procedures must comply with relevant standard requirements.

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Technological Evolution and Industry Impact

The 2023 revision of AASHTO T 192-23 reflects the latest developments in fineness testing technology: the introduction of electroformed screens provides more precise aperture control, but also places higher demands on cleaning methods. Optimized calibration procedures enhance inter-laboratory comparability of results. Clear regulations on cleaning frequency help maintain the long-term stability of testing equipment.

This standard has important application value in cement production quality control, concrete mix design, and project acceptance. Accurate fineness data helps optimize cement grinding processes, control early strength development, and predict concrete workability and durability. With the development of high-performance concrete and specialty cement, the 45μm screening method, as a basic quality control method, and its standardized implementation are of great significance to ensuring project quality.

Future technological development trends include the development of automated testing equipment, the application of digital image analysis technology, and the study of correlations with other fineness characterization methods (such as the Blaine specific surface area method). These developments will further enrich the technical system for cement fineness quality control.

AASHTO T 192-2023 history

• 2023 AASHTO T 192-2023 Fineness of Hydraulic Cement by the 45-μm (No. 325) Sieve
• 2019 AASHTO T 192-2019 Standard Method of Test for Fineness of Hydraulic Cement by the 45-μm (No. 325) Sieve
• 2011 AASHTO T 192-2011 Standard Method of Test for Fineness of Hydraulic Cement by the 45-μm (No. 325) Sieve
• 1999 AASHTO T 192-1999 Standard Method of Test for Fineness of Hydraulic Cement by the 45-muem (No. 325) Sieve

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