ASTM C309: Modern Conversations on an Established Standard

ASTM C309 has long been the standard by which membrane-forming concrete curing compounds are judged.
While applicable for its time and still a valid indicator when dealing with rougher finished concrete, the preparation method prescribed by ASTM C156 and then tested by ASTM C309 does not take into account current finishing techniques involved with today’s steel troweled floor slabs. To understand why this is relevant, the preparation procedures for the test itself need to be understood to make a comparison to the specific type of finish being discussed here.

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Rethinking the Cure of Concrete Floors

The Standard for measuring the effectiveness of curing compounds has historically been ASTM C 309, “Standard Specification for Liquid Membrane-Forming Compounds for Curing Concrete.” The test procedure for this specification measures the moisture loss of a test specimen that has a wood float finish and utilizes a liquid membrane-forming compound. While this Standard has proven to be an effective measure to gage acceptable curing products for concrete, developments in the placement/finish of concrete and advancing technologies of concrete chemicals have paved the way for innovative perspectives on curing of concrete, particularly as it pertains to industrial floors.

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