Laboratory study of the effect of saturation degree on quality of fair-faced concrete surfaces

The concrete composition is one of the most significant factor influencing the quality of the fairfaced concrete surfaces. Practical experiences showed, that in case of architectural concrete slightly oversaturated concrete mixtures result in higher quality surfaces. In this work the surface quality of fair-faced concrete samples was examined depending on the saturation degree of the cement paste and the dimensions of the mould. The main evaluation aspects were the surface void ratio, the discoloration, the honeycomb and bleeding. The surface void ratio was obtained by using digital image processing techniques, while the other surface irregularities were examined using manual methods. The concrete samples were classified according to the Austrian and German guidelines. The effect of saturation degree on the mechanical properties of the concrete was also studied. Results show that the increase in saturation degree of cement paste improves significantly the surface quality, while the dimensions of the mould have a reduced, but also a positive effect. In the meantime, there is a decrease in the mechanical properties of the concrete.