Internal Curing Role of Absorbed Water in Aggregates

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Title: Internal Curing Role of Absorbed Water in Aggregates

Author(s): T. A. Hammer, 0. Bjontegaard, and E. J. Sellevold

Publication: Special Publication

Volume: 218

Issue:

Appears on pages(s): 131-142

Keywords: absorbed water; aggregate; autogenous shrinkage; chemical shrinkage; internal curing; permeability; pore structure

Date: 2/1/2004

Abstract:
The 3 main factors determining the efficiency of lightweight aggregate (LWA) as internal curing agents in concrete are discussed with reference to published papers: I) total amount of water in LWA, 2) LWA particle spacing factor and 3) the LWA pore structure. A desorption method is suggested to characterize factor 3) directly as the ability of the LWA to release water. The method is applied to two LWA types and the results demonstrate clear differences. The role of water in ordinary aggregates is discussed with reference to autogenous shrinkage measurements in concrete and the equivalent paste. It is concluded that the aggregate with 0.8% water absorption indeed serves as internal curing agent by reducing and delaying the autogenous shrinkage. Finally, it is shown that sealed curing does reduce and delay both the cement and pozzolanic reactions.