The contribution of ASTM C 494 Type F superplasticizing admixture, commonly used in the construction market, to the compressive strength of concrete in relation to cement composition was investigated. To accomplish this, three types of cements as blended cement (KC 32.5), pozzolanic cement (TC 32.5), and Portland cement (PC 42.5) were used in preparing concrete mixes with different cement contents of 300, 350, and 400 kg/m(3). To achieve equal workability, a slump ranging from 5-9 cm was targeted for all mixes. Admixture was added to mixing water as 1%, 2%, and 3% by weight of the cement content. Control concrete specimens without admixture were also cast for comparisons. Evaluation was based on the ratios of compressive strengths of concrete containing admixture to the compressive strength of control specimens obtained at the end of 1, 3, 7, and 28 days of curing. Based on the findings obtained from the study, the optimal cement contents were found to be 400 kg/m(3) for KC 32.5, 350 kg/m(3) for TC 32.5, and 300 kg/m(3) for PC 42.5, respectively. The maximum strength gain in concrete was achieved with a 3% admixture addition regardless of cement type. Admixture addition to the concrete mix of more than 3% did not seem to be significant to the strength gain using KC 32.5. The strength gain in concrete using TC 32.5 and PC 42.5 cements especially in early age showed a linear type relationship with the addition of superplasticizer. (C) 2000 Elsevier Science Ltd. All rights reserved.