Early-Age Stiffening of Paste, Mortar, and Concrete in Lab and Field

摘要

Standard and nonstandard penetration-resistance tests were conducted on cement paste, mortars incorporating that paste, and concretes incorporating those mortars. Simultaneously, the diminishing ability to consolidate the concrete with a vibrator, impress a footprint into the concrete surface, manipulate that surface with a magnesium float, and otherwise deform the surface was recorded. The time at which freshly-placed concrete can no longer be effectively consolidated with an immersion vibrator, the time at which professional concrete finishers would begin hand- or power-floating of a concrete surface, and the limit of the capacity to deform concrete by adjusting formwork all occur significantly before mortar reaches "initial setting " as defined by ASTM C403. Likewise, the time at which a recently-cast concrete surface can no longer be manipulated by a hand float occurs well in advance of "final setting " as defined by ASTM C403.