Strength development of mortars using a magnesium silicate hydrate binder system under different curing conditions

Abstract

A magnesium silicate hydrate (M-S-H) binder system was studied to develop low CO2 emission cementitious materials. The binder system contained 60% magnesium oxide and 40% silica fume. M-S-H mortar mixtures were prepared with a fixed water content of w/c=0.40, compared to a control mix using Portland cement (PC). A polymer-based superplasticizer was used to improve the workability of the M-S-H mixtures. Samples were cured at different moist and curing temperatures for compressive strength tests performed at 7, 28 and 90 days. It is found that curing conditions have a significant influence on the strength development of mortar mixtures using M-S-H binder systems. Ambient conditions increase early strength for M-S-H binders, however, reduces long-term strength over 90 days. This curing regime surprisingly results in higher strengths at 28 and 90 days age for M-S-H samples compared to PC. Heated treatment increases early strength, however, decreases the long-term strength of M-S-H samples over 90 days curing period. M-S-H binders have slow strength development compared to PC. The highest compressive strengths of M-S-H samples cured in different regimes at 7, 28, 90 days were 50, 53 and 71 MPa while PC samples cured in water at 21oC at these ages had higher strengths of 55, 75, and 86 MPa, respectively.