In this study, several aspects of the surface treatment of concrete with ethyl silicate were investigated. After the treatment, two different types of concrete (w/c 0.45 and 0.65) showed a dramatic decrease in capillary suction, chloride diffusion coefficient and carbonation depth. A penetration depth into the concrete of about 3–5 mm was assessed. Microstructural investigations showed evidence of a chemical interaction of the amorphous silica gel within the concrete forming calcium silica gel and a selective distribution of silica gel, which was mainly deposited in the small pores. In addition, the brightness and colour changes of the concrete surfaces after the treatment were analyzed quantitatively, finding limited differences, further decreasing over time. This last aspect is relevant for architectural applications of concrete, for example façades of residential buildings, where the architects may be interested in using the texture of concrete but are concerned by possible colour changes related to surface treatments application.