Abstract
High strength and high durability have been regarded as the ultimate goals of conventional concrete. However, concrete generates the extremely large environmental loads. Therefore, ‘low-carbon performance’ is required as a new performance in addition to conventional high strength and high durability when developing new concrete. Cement is a material that emits the largest amount of CO2 among other materials for concrete. Reducing the cement content per unit amount of concrete is an effective means of reducing CO2. One such example is the use of admixture such as ground granulated blast-furnace slag and fly ash. However, the concrete of high replacement ratios of the admixture is considered to remarkably decrease the performance of early strength and the crack resistance. Thus, it is realistic for reducing CO2 to versatilely use cement with low replacement ratios of admixture. That is, it will become more important to comprehensively evaluate the basic and environmental performances of concrete in various cases. In this study, the effect of a fly ash and a ground granulated blast-furnace slag on fresh properties, strength properties and durability was examined. In addition, the effect of the reductions of environmental impact of those admixtures was clarified. When the ground granulated blast furnace slag and fly ash was used, early strength of concrete was seen to be decreased compared with concrete without admixture. However compressive strength of concrete at the age of 28 days, fresh properties and durability could be obtained the same performance as concrete without admixture. Moreover, the ratio of compressive strength of concrete to CO2 emission was reduced when the fly ash and ground granulated blast-furnace slag increased.
