POFA-engineered alkali-activated cementitious composite performance in acid environment

Abstract

The durability performance of palm oil fuel ash engineered alkali-activated cementitious composite (POFA-EACC) mortar exposed to different acid solutions is assessed in this study. 50 mm cubic specimens used for the study were prepared from 100% POFA, alkali-activator (Na2SiO3(aq)/NaOH(aq)) ratios of 2.5, different molarities (10, 12 and 14 M) of NaOH(aq) and 2% volume fraction of polyvinyl alcohol (PVA) fibres. Specimens were exposed to 10% H2SO4(aq), 10% HNO3(aq) and 10% HCl(aq) at pH of 0.56, 0.52 and 0.42 respectively for 3, 6 and 9 months, with unexposed specimens as control. Small changes in compressive strength were identified with POFA mortar specimens during exposure to H2SO4(aq), while exposure to HNO3(aq) and HCl(aq) greatly reduced the strength of the POFA mortar specimens. The results were supported through microstructural examinations using SEM, while the characterization was done using XRD and FTIR. The high resistance of POFA-EACC mortar to H2SO4(aq) is the contribution received through the formation of gypsum, which hinders the infiltration of more acids into the matrix microstructure.