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

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.