Plasticity is an important physical property of masonry mortar and stucco (plaster). Quality workmanship and economic use of materials by masons and plasterers requires highly plastic mortar and stucco. Hydrated lime enhances the plasticity of masonry mortar and stucco by providing excellent water retention and workability.
In 1919, after nearly 10 years of work, chemist Warren Emley developed a method to quantify plasticity. In essence, plasticity testing as developed by Emley quantifies the quality of lime in terms of water retention and workability. Nearly 100 years later, the measurement of plasticity continues to be definitive in ASTM Specification for Finishing Hydrated Lime (C206) and ASTM Specification for Hydrated Lime for Masonry Purposes (C207) utilizing procedures and apparatus outlined in ASTM Test Methods for Physical Testing of Quicklime, Hydrated Lime, and Limestone (C110). This paper reviews the history of the plasticity test method, laboratory methods, instrument nuances, and the need to establish ASTM precision and bias statements for the test method.