Experimental measurements, in conjunction with a simple dissolution/precipitation microstructure model, have indicated that alkalis (present as either sulfates or hydroxides) can have a dramatic influence on the percolation of the capillary porosity in hydrating cement paste, possibly via their influence on the morphology of the gel hydration products. Future research will extend these experiments to a variety of w/c ratios and will also consider whether lithium ions behave in a manner similar to potassium and sodium.