An experimental study was carried out for the development and characterization of innovative photopolymerizable siloxane-modified acrylic formulations for possible use as protective coatings for stone substrates.Two amounts of calcarenitic stone particles (25wt.% and 35wt.%) were added to a siloxane-modified acrylic mixture. The effect of stone particles inclusion on the reactivity and surface properties of the photopolymerizable systems was investigated. To this aim, the kinetics of the radical photo-polymerization reaction, induced by UV radiations in the presence of a suitable photoinitiator, was studied by calorimetric analysis, both in air and nitrogen atmosphere. The formulations, coated on a glass substrate, were photo-cured by using a medium pressure Hg UV lamp in air. On the coatings photo-polymerized in air were measured: gel content, transparency, scratch and surface hardness.