Abstract
Although water-to-cement ratio is the main factor of determining the compressive strength of the concrete, sand-to-aggregate ratio, and unit water content dominate segregation resistance and target slump of the concrete, respectively. Therefore, in this research, to suggest a fundamental data on sand-to-aggregate ratio and unit water content for mix design of high strength concrete, fundamental properties of the high strength concrete of 30 % water-to-cement ratio were evaluated depending on the various sand-to-aggregate ratio and unit water content. As a result of the experiment, for fresh state concrete properties, as the sand-to-aggregate ratio was increased, slump, slump flow, and air content were decreased, and as the unit water content was increased, slump, slump flow, and air content were increased. Based on the 180 mm of slump, each slump and slump flow measurements deduced favorable performances at lower and higher than this value, respectively. In segregation aspect, about 45 % of sand-to-aggregate ratio was good and under this conditions, it was good to control the superplasticizer dosage and unit water content. Furthermore, to achieve better compressive strength, under the 45 or 50 % of sand to aggregate ratio, low unit water content of $165kg/m^3$ showedmaximumvalueofcompressivestrength.