The Influence of NaOH Concentration on Molar Ratios of Palm Oil Boiler Ash Based Geopolymer

Abstract

Palm oil boiler ash (BA) has been synthesis with alkaline activator to produce boiler ash based geopolymer. The ratio of BA/alkaline activator and Na2SiO3/NaOH was fixed for the entire experiment, where six different of NaOH concentration (6 M, 8 M, 10 M, 12 M, 14 M, 16 M) was used to produce geopolymer paste. The compressive strength of geopolymer paste with NaOH concentration 14 M showed the maximum strength which is 13.9 MPa. The strength reduce when geopolymer paste used NaOH concentration more than 14 M. In term of molar oxides SiO2/Al2O3, Na2O/SiO2and H2O/Na2O with the increasing of NaOH concentration Na2O/SiO2ratio also increased but H2O/Na2O ratio decreased. Meanwhile SiO2/Al2O3ratio remain constant because the BA/alkaline activator and Na2SiO3/NaOH ratio were constant in this study. The XRD analysis illustrated that the value of 2θ for all geopolymer samples were approximately the same which is 27° with major components of quartz and minor component of cristobalite.