Physio-chemical characterisation of high-volume cement replacement in low carbon cement composite binders incorporating silicon manganese slag and ground granulated blast furnace slag

This study investigates mechanical and microstructural performance of cement composites incorporating silicon manganese slag (SiMn slag) and ground granulated blast furnace slag as supplementary cementitious materials. Binary binders with SiMn slag and ternary binders with combinations of SiMn slag and GGBFS replacing cement by 30 %, 50 %, 70 % and 90 % were investigated for their mineralogical and microstructural properties along with compressive strength over curing durations of 3, 7, 28, and 90 days. Analytical techniques like XRD, FTIR, TGA, isothermal calorimetry and SEM-EDS were employed to characterise hydration products and observe microstructural development. The laboratory study revealed low early-strength development in all investigated composite binders. However, after 28 days 30 % and 50 % cement replaced binaries achieved comparable compressive strength performance with 2.8 % less and 0.5 % higher strength gains compared to control specimens, respectively. At 90 days these binaries developed 12 % and 2.5 % higher strength, respectively, than the control while 50 % cement replaced ternary achieved similar strength to that of the control (84 MPa). The study highlights the contribution of pozzolanic reaction of SiMn slag to form dense, less porous microstructures comprising mostly of C-S-H, contributing to long-term strength development. The results demonstrated the potential of utilising the industrial by-product SiMn slag, in low-carbon cement production. • SiMn slag can replace 50 % of cement without reducing compressive strength. • 70 % cement replacement achieved 80 % compressive strength of control. • All composite binders showed lower early compressive strength development.