Though appropriate for its time, the Standard Test Method for Water Loss Through Liquid Membrane-Forming Curing Compounds for Concrete – or ASTM C309 – was developed when finishing techniques had not yet progressed to the effectiveness of contemporary practices. Wood float finishes, as required by ASTM C309 in accordance with ASTM C156, create a more porous surface than steel-bladed power trowel techniques commonly used today. Steel troweled finishes result in a harder, tighter surface that reduces moisture loss, aiding cement hydration.
The prevalence of more effective steel trowel finishing techniques has led to improved hydration of concrete over wood float-finished surfaces. These advanced finishing techniques have led to renewed interest in the development of alternative curing methods capable of achieving the water retention requirements of ASTM C309 on more effectively troweled floors. However, as long as ASTM C309 requires specimens to be prepared according to the finishing techniques of ASTM C156, many potentially effective cures are prevented from successfully meeting these specifications. Read More