Influence Of Blended Cements On The Performance Of Water Repellent Agents

Ingress of moisture and harmful ions (e.g. chloride, sulfate) into cementitious materials is one of the major factors in defining their durability. Modifications of building materials by targeted deposition of surface functional agents that make the surface hydro- and/or oleophobic aim to minimize moisture and ion ingress, and thus extend service life of the cement based structures. Water repellent and easy-to-clean coatings for inorganic substrates have gained strong attention during the last few years and various formulations based on silicones or alkylpolysiloxanes have been developed. Cementitious building materials are highly complex systems with many components and changing properties in the course of a building's service life. The interactions between the chemical agents and the cement based materials depend on many factors. The chemical properties of the material substrate appear to be the most important but in the context of their influence on the functionality of silanes and/or siloxanes these characteristics have not been well understood yet. The aim of this study was to evaluate the effect of different blended cements on water repellent agents' performance. Two organosilicon compounds were applied on fresh blended cements containing limestone (L), fly ash (F), slag (S) and trass (T), and investigated in terms of their functionality. The surface properties of functionalized blended cements were studied based on wettability, i.e. contact angle measurements, before and after exposure to artificial and natural weathering. The first results indicate that slag and trass more distinctly affect the water repellent surface performance after aging.