A STUDY OF THE EFFECTS OF NICKEL CHLORIDE AND CALCIUM-CHLORIDE ON HYDRATION OF PORTLAND-CEMENT

Portland cement samples containing amounts of CaCl2 and NiCl2 ranging from approximately 1% to 20% by weight have been examined by Si-29 and AI-27 solid-state MAS NMR as a function of time, and some of the matu re pastes have been characterized by X-ray diffraction. Changes in phy sical properties that had been previously observed as a function of am ounts of salt added are clearly traceable to differences in the silica te matrices. Low concentrations of both salts promote Q1 formation, bu t high concentrations result in formation of much more Q2 at the expen se of Q1. Both salts accelerate both aluminate and silicate hydration, and the effects appear to be almost entirely due to chloride. Minor v ariations in hydration rates at high Ni concentrations may be the resu lt of nickel salt precipitation.