Effect of Concrete Compressive Strength and Supplementary Cementitious Materials on Lifecycle $CO_2$ Assessment of Reinforced Concrete Structures

철근콘크리트 구조물의 전과정 탄소평가에 대한 콘크리트 압축강도 및 혼화재의 영향

The present study established a $CO_2$ performance evaluation table to assess the lifecycle $CO_2$ amount of reinforced concrete(RC) structures. As input data necessary for the performance evaluation table, data collected from actual domestic surveys conducted in 2012 were used, which included data on the surrounding environments, lifecycle inventory database, life expectancy of structures, recycling activity scenario, and $CO_2$ concentration. The performance evaluation table embodies $CO_2$ emissions (from materials, concrete production, casting, demolition of structures, crushing of waste concrete, and transportation) and $CO_2$ uptake by concrete carbonation during lifetime of structures and recycled aggregates produced from the demolished concrete. For the case study using the performance evaluation table, structural design was conducted for an RC column and beam in office building with a rahmen system according to the variation of concrete compressive strength, and then lifecycle $CO_2$ amount was assessed for the determined section size and reinforcing details of the members. Furthermore, the lifecycle $CO_2$ amount of RC members was examined according to the replacement level of ground granulated blast-furnace slag(GGBS) and fly ash(FA), but at the same compressive strength. The present lifecycle $CO_2$ assessment for RC member reveals that at the same life expectancy of structures high-strength concrete on the $CO_2$ reduction is favorable to RC columns, but unfavorable to RC beams. The $CO_2$ reduction according to the replacement of GGBS and FA is greater in RC columns than in RC beams.