ASTM C266
Overview of ASTM C266 - Standard Test Method for Time of Setting of Hydraulic-Cement Paste by Gillmore Needles
Introduction
The ASTM C 266 standard outlines a procedure to determine the setting time of hydraulic-cement paste using the Gillmore needles. This test is crucial for understanding how quickly cement paste begins to set, affecting its handling and application in construction.
Scope and Safety
Scope:
This method assesses the setting time of hydraulic-cement paste using Gillmore needles.
Inch-pound units are the standard, with SI units provided for reference.
Safety Concerns:
Highlights the need for protective measures due to the caustic nature of fresh hydraulic cement mixtures.
Summary of Test Method
A paste of normal consistency is prepared from the cement to be tested, and the setting time is determined using Gillmore initial and final needles. The initial and final setting times are identified based on when the needles cease to leave a complete circular impression on the paste surface.
Significance and Use
This test method is essential to verify whether a cement paste meets the specified limits for the Gillmore time of setting, which is critical for its suitability in various construction applications.
Apparatus
The required apparatus includes a flat trowel, mixer, bowl, paddle, scraper, glass graduates, mass-determining devices, plane non-absorptive plates, and Gillmore needles with specific dimensions and weights.
Reagents and Materials
Potable water or reagent water as per ASTM D1193 specifications is used for mixing the cement paste.
Sampling and Conditioning
Cement samples should be obtained following Practice ASTM C183. The testing environment, including materials, should be maintained at specific temperature and humidity levels.
Test Procedure
Preparation of Cement Paste:
Mix 650 g of cement with water to achieve a paste of normal consistency as per Test Method ASTM C187.
Molding Test Specimen:
Form a pat from the paste on a plane non-absorptive plate and place it in a moist cabinet or room.
Time of Setting Determination:
Apply the Gillmore initial and final needles to the surface of the pat to determine the initial and final setting times.
Reporting
Report the initial and final setting times in minutes, rounding to the nearest 5 minutes.
Precision and Bias
Provides the standard deviation for single-operator and multi-laboratory tests.
No bias information is available due to the lack of a suitable reference material.
Conclusion
ASTM C266 is an important standard test method in the field of construction material science. It offers a reliable way to determine the setting time of hydraulic-cement paste, which is a key factor in assessing its application and performance in various construction scenarios. The use of Gillmore needles provides a standardized approach to measure the setting time, contributing to the consistency and quality assurance in cement utilization.