Compressive strength and microstructure of alkali-activated waste glass-slag cements.

Composite alkali activated cements of waste glass (WG) and ground granulated blast furnace slag (GGBFS) were studied in pastes for 720 daysThe factors for the experimental design (Taguchi method) were: %WG, sodium silicate modulus (Ms), curing temperature, and %ultra-fine WG; the response variable was the compressive strength. ²⁹Si Nuclear Magnetic Resonance, scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction indicated that the reaction products in pastes with WG contents greater than 50% were predominantly silica gel, which reached up to 140 MPa; on the other hand, phases of C-S-H/C-A-S-H predominated in pastes with GGBFS content > 50%, which showed high early strength. Silica gel performed as a cementitious phase contributing to the 720-days strength, but it was unstable underwater; however, it was stabilized when intermixed with C-S-H/C-A-S-H. Curing at 40-60 °C promoted cracking and strength loss after 14 days. [ABSTRACT FROM AUTHOR]