*Article* **The Optimization of Mix Proportion Design for SCC: Experimental Study and Grey Relational Analysis**

**Xinxin Ding 1,2,\*, Mingshuang Zhao 1,2, Xue Qiu 1, Yupu Wang <sup>1</sup> and Yijie Ru <sup>1</sup>**


**Abstract:** The optimization of mix proportions based on the targeted fresh and hardened performances of self-compacting concrete (SCC) is a foundation for its transition from laboratory research to industrial production. In this paper, the mix proportions of various SCC mixtures were designed by the absolute volume method with changes in the content of river sand and manufactured sand, the content of fly ash and granulated ground blast furnace slag (GGBS) and the maximum particle sizes of coarse aggregates. This experimental study was carried out to verify the workability, density and cubic compressive strength of SCC. The results show that SCC demonstrated good performance with appropriate mix proportions of manufactured sand and river sand. A hybrid effect of fly ash and GGBS appeared on the fresh performance of SCC with a constant strength, and the coarse aggregate with a smaller maximum particle size was beneficial to the workability but detrimental to the compressive strength of SCC. Finally, the optimization of the mix proportion of SCC was evaluated by grey relational analysis, in which the weight of the indicators was determined by the entropy method to improve the evaluation credibility. As a result, the optimal mix proportions of SCC were selected.

**Keywords:** self-compacting concrete (SCC); mix proportion design; optimization; experimental verification; the grey relational analysis
