Influence of supplementary cementitious material on CO2 balance of cracked RC members in their whole life cycle

Abstract

The building construction industry is a significant source of carbon dioxide (CO2) emissions. To reduce CO2 emissions, supplementary cementitious materials are widely used in the concrete. At the same time, during the service life and post-demolition period of the reinforced concrete (RC) members, atmospheric CO2 is absorbed by carbonation. In the present paper, influence of the supplementary cementitious material (SCM) on CO2 balance, i.e., the difference between the CO2 emissions and uptakes, of cracked RC members in their whole life cycle (including the service and post-demolition periods) is evaluated. Three types of concrete — ordinary Portland cement (OPC) concrete and two ‘green’ concretes (one with 30% of fly ash (FA) and the other one with 50% ground granulated blast-furnace slag (GGBS)), are considered. The carbonation depths in the cracked RC members are estimated based on the results of accelerated carbonation tests of cracked RC test specimens made from the same types of concrete. Corrosion initiation times, service life and repair times of the cracked RC beams are determined under different exposure conditions. Finally, the CO2 emissions and absorptions of the cracked RC members are assessed over their whole life cycle. The resulting CO2 balance assessments on cracked RC beams made from the same types of concrete in the test show that, from the view of the whole life cycle, the OPC RC members have a noticeably worse environmental impact than the RC members made from the GGBS concretes; while the RC members from the GGBS concrete are more environmentally friendly than those from the FA concrete.