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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Liquid Hardeners Realize Maximum Performance When Applied After 28 Days

Patience is a Virtue - Testing Confirms Liquid Hardeners Realize Maximum Performance When Applied After 28 Days

A growing trend within the concrete flooring industry is to apply liquid hardeners on freshly-troweled concrete in what is referred to as a “pre-seal” or a “cure-coat.” Conversely, Nox-Crete has historically advised applicators to wait and apply liquid floor hardeners a minimum of 28 days after concrete placement to allow for maximum performance. The 28 day recommendation was based on intuition and a strong understanding of the chemistry behind liquid floor hardeners and the means by which they densify concrete surfaces. The lack of conclusive data led Nox-Crete to not only ask but to answer the question, does the timing of the application (Day One vs. Day 28) impact the liquid floor hardener’s ability to improve abrasion resistance? Continue reading