The invention relates to a blocked mercaptosilane of general formula I below:(HO)2R1—Si—Z—S—C(═O)-Ain which:R1 represents a monovalent hydrocarbon-based group chosen from alkyls, which are linear or branched, cycloalkyls or aryls, having from 1 to 18 carbon atoms;A represents hydrogen or a monovalent hydrocarbon-based group chosen from alkyls, which are linear or branched, cycloalkyls or aryls, having from 1 to 18 carbon atoms;Z represents a divalent bonding group comprising from 1 to 18 carbon atoms.