Plasma-chemical modification of concrete

Abstract

Plasma chemical modification (PCM) improves chemical resistance of a glazed decorative coating and expands opportunities for designing various types of the decoration of concrete. However, PCM exposes the material to a significant thermal shock that leads to dehydration of hydrosilicates in the cement matrix followed by loss of strength of the concrete coating. This results in a reduction in the service characteristics of the concrete protective and decorative layer such as adhesion strength and freeze-thaw resistance and shortens the coating durability. Therefore, the improvement of the PCM method is a hot topic of the study and it is one of the most effective and modern technologies, which will result in enhancement of serviceability of concrete with the glazed decorative coating. This study investigated the effect of incorporation of calcium aluminate cement as a silicon-based intermediate layer between the glazed decorative layer and the concrete surface. The study demonstrated that the calcium aluminate cement intermediate layer after plasma chemical modification was dehydrated. Based on mineral composition and structural analysis, the dehydrated layer was visually divided into three zones: the upper dense layer; an intermediate layer with micro cracks; and the bottom dense layer. The microstructure of the dehydrated zone is represented by small non-developed microcracks less than 50 μm. Magnesium spinel was the main crystal phase in a calcium aluminate cement matrix. The dense dehydrated zone had a shell-like fracture, which is typical for spinel with imperfect cleavage. This study developed a glazed decorative coating and a protective calcium aluminate cement-based intermediate layer with the adhesion strength of 4.1 MPa and freeze-thaw resistance of more than 50 cycles that exceed service characteristics of concrete with the coatings using other materials.