Influence of the storage conditions on the dimensional changes of heat-cured mortars

Some cementitious materials cured at elevated temperature may expand on sub sequent exposure to moisture. Concern has been expressed as to the relevanc e of small laboratory specimens to field concretes, in particular due to th e potential leaching of ions into the storage solution. The work presented here aims at investigating this effect. Mortars cured at elevated temperatu re in identical fashion were subsequently stored at 90-100% relative humidi ty (RH) and in water, a LiOH solution, and KOH solutions of various concent rations. The largest and most rapid expansion occurred with mortars immerse d in water. The samples stored at 90-100% RH expanded more slowly. Expansio n was even slower when subsequent storage was in LiOH or KOH solutions. The same samples were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD). These techniques indicated that ettringite had formed ov er time in all samples, with little apparent relation to the degree of expa nsion. The composition of the C-S-H gel changed over time, differently for the different storage conditions. (C) 2001 Elsevier Science Ltd. All rights reserved.