A novel optimization design framework for mix proportion of mass concrete: A case study of foundation in super high-rise buildings

To address thermal cracking in mass concrete structures, this study proposes an optimization framework for mix proportions to minimize the cement usage while ensuring the required concrete strength, using the foundation of Shenzhen CITIC Financial Center as a case study. Concrete components are grouped into three categories: (1) water and superplasticizer, (2) cement, fly ash, and slag, and (3) fine and coarse aggregates. Grey relational analysis (GRA) was applied to quantify correlations between compressive strengths (7-, 28-, and 60-day) and mix parameters. Experimental validation confirmed the optimal mix proportions. Key findings include: (1) superplasticizer reduces water demand by 10–15% while enhancing strength; (2) fly ash exhibits comparable grey relational coefficients to cement in C50 concrete (0.78 vs. 0.80), enabling partial cement replacement (up to 30%), whereas slag shows significantly lower coefficients (0.42); (3) for C50 concrete, fine and coarse aggregates have nearly identical impacts on strength (coefficients: 0.65 vs. 0.63), but their influence becomes less predictable for C45 concrete (±15% deviation). The proposed GRA-based framework provides a systematic approach for optimizing mass concrete mixtures under limited trial data, balancing thermal and mechanical performance.