This paper reports a part of an ongoing laboratory investigation in which the compressive strength of ground granulated blast-furnace slag (GGBFS) concrete studied under dry and wet curing conditions. In the study, a total of 45 concretes, including control normal Portland cement (NPC) concrete and GGBFS concrete, were produced with three different water-cement ratios (0.3, 0.4, 0.5), three different cement dosages (350, 400, 450 kg/m(3)) and four partial GGBFS replacement ratios (20%, 40%, 60%, 80%). A hyperplasticizer was used in concrete at various quantities to provide and keep a constant workability. Twelve cubic samples produced from fresh concrete were de-moulded after a day, then, six cubic samples were cured at 22 +/- 2 degrees C with 65% relative humidity (RH), and the remaining six cubic samples were cured at 22 +/- 2 degrees C with 100%RH until the samples were used for compressive strength measurement at 28 days and three months. Three cubic samples were used for each age and curing conditions. The comparison was made on the basis of compressive strength between GGBFS concrete and NPC concrete. GGBFS concretes were also compared within themselves. The comparisons showed that compressive strength of GGBFS concrete cured at 65%RH was influenced more than that of NPC concrete. It was found that the compressive strength of GGBFS concrete cured at 65%RH was, at average, 15% lower than that of GGBFS concrete cured at 100%RH. The increase in the water-cementitious materials ratios makes the concrete more sensitive to dry curing condition. The influence of dry curing conditions on GGBFS concrete was marked as the replacement ratio of GGBFS increased. (c) 2006 Elsevier Ltd. All rights reserved.