Climate-adaptive optimization of low-carbon slag-fly ash cementitious systems considering CO2 emissions and carbonation durability

초록

The sustainable design of low-clinker cementitious materials requires not only reducing embodied CO2 emissions but also ensuring long-term chemical durability under changing environmental conditions. However, conventional low-carbon concrete optimization often increases the use of supplementary cementitious materials, such as slag and fly ash, without explicitly considering the increased risk of carbonation-induced degradation. This study develops a climate-adaptive optimization framework for low-carbon slag-fly ash cementitious systems by integrating embodied CO2 emissions, carbonation durability, and future climate scenarios. An OPC-slag-fly ash ternary binder system is investigated, and carbonation depth is adopted as a service-life constraint. Time-dependent CO2 concentration and temperature changes under SSP2-4.5 and SSP5-8.5 scenarios are incorporated and compared with the conventional constant-environment assumption. Five representative cities, namely Seoul, Tokyo, Shanghai, Duisburg, and Rotterdam, are selected to capture regional differences in carbonation exposure conditions. The results show that emission-oriented optimization without carbonation constraints favors high supplementary cementitious material replacement and low cement content, leading to minimum CO2 emissions but insufficient durability in carbonation-sensitive environments. When carbonation durability is considered, the optimal mixtures become strongly region-and climate-dependent. Under future climate scenarios, several mixtures optimized under constant environmental conditions become infeasible, requiring lower water-to-binder ratios and higher cement contents to maintain the prescribed service life. These adjustments improve carbonation resistance but increase embodied CO2 emissions, revealing a clear trade-off between carbon reduction and durability assurance. The proposed framework provides a quantitative basis for sustainable, climate-resilient, and durability-oriented design of low-clinker cementitious materials using industrial by-products.

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