Theory & Method
Gillmore Apparatus - QualiGill™ C266
The Gillmore needle method determines cement setting time by monitoring the resistance of a cement paste specimen to penetration by two standardized weighted needles of different diameters and masses. Setting is a progressive stiffening process in which the cement paste transitions from a plastic, workable consistency to a rigid, hardened state as the hydration reaction proceeds. Two stages of setting are defined and measured: initial set and final set.
To perform the test, a pat of cement paste of standard consistency is prepared on a flat glass plate according to ASTM C266 and allowed to rest undisturbed at controlled temperature and humidity. At regular time intervals, the two Gillmore needles are gently lowered in turn onto the surface of the cement paste specimen. The initial setting needle — weighing 113.4 g with a tip diameter of 2.12 mm — bears a higher stress per unit area and is used to detect the transition from a plastic to a semi-rigid state. The cement paste is considered to have reached initial set when the initial setting needle no longer sinks visibly into the surface under its own weight.
The final setting needle — weighing 453.6 g with a tip diameter of 1.06 mm — bears a substantially higher contact stress, enabling detection of the higher degree of hardening associated with final set. The cement paste is considered to have reached final set when the final setting needle fails to make a complete circular impression on the specimen surface. The time elapsed from water addition to initial set and final set are recorded as the initial and final setting times of the cement, respectively, and compared against the specification limits of the applicable cement standard.
The Gillmore needle method is preferred over the Vicat needle method for certain cement types — particularly masonry cement and hydraulic hydrated lime — and is also used when the Gillmore method is specifically required by the applicable project specification or standard.
