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Curing, Hydration, and Microstructure of Cement Paste.


pdf icon Curing, Hydration, and Microstructure of Cement Paste. (2048 K)
Bentz, D. P.; Stutzman, P. E.

ACI Materials Journal, Vol. 103, No. 5, 348-356, September/October 2006.

Keywords:

cement paste; curing; hydration; microstructure; porosity; water; cements; low tempeature; calorimetry

Abstract:

This paper compares hydration characteristics and microstructures of cement pastes with water-cement ratios (w/c) of 0.35 and 0.435, cured under saturated and sealed conditions. Degree of hydration is quantified by loss on ignition (LOI) measurements. The microstructures, and specifically the pore structures, of the hydrated pastes are evaluated using scanning electron microscopy and low temperature calorimetry. The w/c specimens (equal to 0.35) cured under sealed conditions first form a depercolated (disconnected) capillary pore system that later reconnects due to self-desiccation and autogenous shrinkage. Conversely, in the w/c specimens (equal to 0.435), there is some indication that sealed curing actually leads to an earlier depercolation of the remaining capillary pores than saturated curing, but without a subsequent repercolation. The results indicate the criticality of proper curing for both w/c specimens suggest that curing for strength and curing for durability may require different practices and may provide the impetus for innovative curing strategies to produce concretes with optimum properties.