Influence of Ferrochrome Slag Co-Binder on Mechanical Behaviour of Fly ash Geopolymer Mortars

An experimental study was conducted to investigate the mechanical properties of fly ash geopolymer binder system containing 0 to 30 wt% ferrochrome slag. Paste and mortar samples were prepared using a mixture of sodium silicate (SS) and sodium hydroxide (SH), as the alkali - activator solution made at varied SS/SH ratio of 1.5 to 2.3, along with varied sodium hydroxide concentration ranging from 10.7 to 15.2 M. The ratio of alkali - activator to raw aluminosilicate material, was kept constant at 0.50, 0.52 or 0.54. Paste or mortar cubes of 50 mm size were cast and cured at 23, 40, 60 or 80 °C for compressive strength testing, while prisms of 25 × 25 × 285 mm size were prepared for drying shrinkage monitoring. Also measured were workability, density, water absorption and pore volume. Microanalytical studies were done using scanning electron microscopy, X - ray diffraction analysis, and Fourier transform infrared spectroscopy. It was found that fly ash geopolymer mortars containing 10% ferrochrome slag and cured at normal temperature gave the optimal compressive strength. There was significant increase in drying shrinkage of mortars, as the content of ferrochrome slag increased, but overall values were within normal range.