The alkali content of cements has long been a subject of interest, due both to the role of alkalis in deleterious alkali-silica reactions (ASR) and also to their influence on the hydration and microstructure of cement paste. It is generally accepted that potassium and sodium ions (present along with either sulfates or hydroxides) accelerate the early hydration of cement, while resulting in reduced hydration and strength at later ages [1, 2]. Electron microscopy observations have suggested that the alkalis also modify the morphology of the calcium silicate hydrate gel (C-S-H) formed during hydration, particularly for the hydration of tricalcium silicate (C3S) pastes [3, 4]. The influences of alkalis and the altered morphology of the C-S-H gel on transport properties and durability have been less studied. Recently [5], low temperature calorimetry (LTC) results have indicated that after about 100 d of saturated curing, cement pastes with a water-to-cement ratio (w/c) of 0.40 by mass fraction, containing additional alkalis, exhibited a depercolated (disconnected) capillary pore structure, while the capillary pores in the original (low alkali) cement paste were still highly percolated. This paper presents further studies that have been conducted to verify this observation, using a combination of LTC and loss-on-ignition (LOI) experimental techniques, in concert with a simple dissolution/precipitation hydration model.