Effects of addition of Al(OH)_3 on the strength of alkaline activated ground blast furnace slag-ultrafine palm oil fuel ash (AAGU) based binder

摘要

Effects of Al(OH)_3 content on the compressive-strength of alkaline activated ground blast furnace slag (GBFS)-ultrafine palm oil fuel ash (UPOFA) based mortar (AAGU) were investigated. The mortar was activated with combined activators (Na_2SiO_(3aq) of silica modulus (Ms - SiO_2/Na_2O) of 3.3 and 10 M NaOH_(aq)). The Scanning Electron Microscope couple with energy dispersive X-ray (SEM + EDX) revealed the possibility of formation of distinctive products of calcium-silicate-hydrate (C-S-H) and Ca/Na-alumino-sili-cate-hydrate (C/N-A-S-H) while Fourier transform infra-red spectroscopy (FTIR) revealed the existence of higher degree of Si-Al substitution, amorphousity and carbonation as a result of inclusion of Al(OH)_3 in the mixture. The 3-day compressive-strength of AAGU_(Al) mortar increased with Al(OH)_3 up to optimum value of 4 wt.% of PMs (GBFS + UPOFA) but started decreasing when the Al(OH)_3 is outside the optimum. The strength of 42-49.5 MPa could be achieved at the Al(OH)_3 dosage of 3-4 wt.% while the equivalent SiO_2/Al_2O_3 molar-ratio ranged from 6.72 to 8.94.