Mix Design and Performance of Coastal Fair-Faced Concrete Based on Orthogonal Experiments

Compared with inland areas, coastal fair-faced concrete (CFFC) in coastal environments is subject to more severe environmental erosion during its service life. An inappropriate mix design can lead to the failure of concrete structures. It is therefore necessary to develop appropriate mix designs and conduct research into their performance. The orthogonal method was combined to study the influence laws of four factors, namely water-cement ratio (W/B), cement content (WC), fly ash content (WFA), and microbead content (WBM), on the slump (Sp), mechanical properties (fc7d, fc28d), and apparent porosity properties (SM) of CFFC. After verification, the durability of CFFC with the optimal ratio was further examined. The results show that the order of influence of each factor on Sp, fc7d, fc28d, and SM is: W/B > WC > WBM > WFA, WFA > W/B > WC > WBM, W/B > WC > WFA > WBM, WC > W/B > WFA > WBM, respectively. The SF and flowability of CFFC with the optimal ratio are 198 mm and 579 mm, respectively; the corresponding fc7d and fc28d are 45.06 MPa and 64.03 MPa, respectively; and the maximum pore diameter, surface pore area ratio, and standard deviation of the pore distribution of the optimal CFFC are 2.14 mm, 0.31%, and 1.52 mm, respectively. The 84 d rapid chloride penetration coefficient, 28 d maximum carbonation depth, and 28 d shrinkage of the optimal CFFC are 2.1 × 10−12 m2/s, 5.6 mm, and 405 µε, respectively. When prepared using the optimal mix proportions, CFFC can meet the requirements for high-performance fair-faced concrete projects in coastal areas, thereby providing valuable guidance for the practical applications of CFFC in coastal engineering.