Heat treatment is extensively used to accelerate the process of the strength development of concrete for prefabrication purposes. This study was conducted to determine the effect of cement composition on the improvement of the one-day flexural strength of heat-treated mortar prisms. Considering the strength gain at the end of one day of heat treatment application, it call be concluded that a treatment temperature of 80 degrees C seems to be appropriate for CC 32.5 cement while it is 65 degrees C for the other cements tested, It is also concluded that an initial curing of 4 h is suitable in view of the technical success of heat treatment application. However, it may be shorter for blended cements for economic reasons. (c) 2005 Elsevier Ltd. All rights reserved.