Strength and workability of magnesium silicate hydrate binder systems

This paper discusses the optimization of magnesium silicate hydrate (M-S-H) binder systems for cement paste and mortar. The compressive strength and workability (water demand, flow) of M-S-H binder systems were studied. The binary systems contain magnesia and silica fume in which each constituent accounts for 40-60% by mass of the binder. The ternary systems include 10-40% very fine crushed quartz which is used as a fine filler for the partial replacement for the cementitious materials. It was found that the pure M-S-H binder system has a much higher water demand compared to Portland cement due to the very high silica fume content. The use of polymer-based superplasticizer effectively reduced water to cementitious materials ratio (w/c) for M-S-H binder system. The optimal binary binder composition for strength and workability was found to contain 60% magnesium and 40% silica fume (Mg/Si molar ratio = 2.25). The addition of very fine crushed quartz filler from 10 to 40%, as a partial replacement for the magnesia and silica fume, further improved the rheology of the mixture allowing for a workable mix with a w/c = 0.30. The highest compressive strength of mortar samples achieved with ternary M-S-H system is up to 87 MPa.