Mechanical Properties of Na2CO3-Activated High-Volume GGBFS Cement Paste

The use of Na₂CO₃to improve the mechanical properties of high-volume slag cement (HVSC) is experimentally investigated in this study. Ordinary Portland cement (OPC) was replaced with 50, 60, 70, 80, and 90% ground-granulated blast-furnace slag (GGBFS) by weight. Na₂CO₃was added at 0, 1, 2, 3, 4, and 5 wt.% of HVSC (OPC + GGBFS). The compressive strength, water absorption, ultrasonic pulse velocity, dry shrinkage, and X-ray diffraction spectra of the Na₂CO₃-activated HVSC pastes were analyzed. The results indicate that Na₂CO₃was effective for improving the strength of HVSC samples at both early and later ages. There was a trend of increasing HVSC sample strength with increasing Na₂CO₃content. The 5% Na₂CO₃-activated HVSC (50% OPC + 50% GGBFS) paste had the best combination of early to later-age strength development and exhibited the highest UPV and the lowest water absorption among the Na₂CO₃-activated HVSC samples at later age.

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