Two types of deformation - creep and shrinkage - occurring in cements and concretes are caused by compression and time. They lead to the loss of compressive strength. In the present study both deformation types were experimentally examined using concrete samples made from ordinary Portland cement OPC 32.5 containing 0; 15 and 30% oil shale ash (OSA). Tests made during months showed that concretes produced using Portland cement with 15% OSA shrank less than samples containing no OSA (OPC contr.). This finding agrees with the condition that concrete samples produced using 15% :OSA-added cement are not to display a deformation rate higher than 0.1% within six months and 0.5% within three months.