Material design and engineering application of Fair-faced self-compacting concrete

Fair-faced concrete (FFC) with excellent decorative effect is a kind of concrete which can be directly used as external facade, whereas the low workability and complex molding process of the ordinary FFC restricts its broad application. In this study, the C40 self-compacting FFC (named as fair-faced self compacting concrete or FFSCC for short) was prepared. With the reference of average paste thickness (APT) theory, the effects of coarse aggregate gradation and content, sand content and mineral admixture content on workability, compressive strength and decoration effect of FFSCC were quantitatively analyzed to obtain an optimal mix proportion of FFSCC. The results indicated that the increased proportions of 5-10 mm aggregates or higher aggregate content would lead to the lower APTs, which resulted in lower workability, lower surface porosity, and higher strength. Fitting results between APT and several properties presented that the fluidity, flow velocity and compressive strength possessed the linear relationships with APT values. While the passing capacity, segregation ratio and surface porosity possessed the quadratic polynomial relationships with APT values. Furthermore, atomic force microscopy (AFM) was applied to observe the surface texture of FFSCC. Results showed that its surface roughness (RMS) was 3.7 nm, which was smoother than the polished cement paste. Finally, the optimal FFSCC was successfully applied in second lining of Nan Kunshan tunnel. (c) 2021 Elsevier Ltd. All rights reserved.