Detecting Solidification Using Moisture Transport from Saturated Lightweight Aggregate

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Title: Detecting Solidification Using Moisture Transport from Saturated Lightweight Aggregate

Author(s): R. Henkensiefken, G. Sant, T. Nantung, and J. Weiss

Publication: Special Publication

Volume: 259

Issue:

Appears on pages(s): 77-88

Keywords: chemical shrinkage; internal curing; lightweight aggregate; setting; solidification; x-ray absorption

Date: 2/1/2009

Abstract:
The propensity for early-age shrinkage cracking in low w/c concretes has spawned the development of new technologies that can reduce the risk of cracking. One such technology is internal curing. Internal curing uses saturated lightweight aggregate to supply ‘curing water’ to low w/c paste as it hydrates. Significant research has been performed to determine the effects of internal curing on shrinkage and stress development in sealed samples. However, relatively little detailed information exist about how water is released from the lightweight aggregate to the surrounding cement paste. This study examines the timing of moisture release from saturated lightweight aggregate (LWA). Specifically this paper focuses on fluid transport around the time of set. X-ray absorption is used to trace the time at which water moves from the lightweight aggregate to the paste. X-ray observations are compared with results from the Vicat needle, autogenous shrinkage, and acoustic emission tests. These results are contextualized in terms of structure formation and vapor space cavitation in the cement paste.