Impact of Al(OH)3 addition to POFA on the compressive strength of POFA alkali-activated mortar

The study reports the influence of Al(OH)3 as alumina source on the compressive strength of POFA alkali-activated mortar (POFA AAM). The synthesis of the developed POFA AAM stems from the mixture proportioning of Na2SiO3(aq), NaOH(aq), POFA and Al(OH)3. At the 28th day, after 65 °C heat and laboratory curing, the compressive strength of the POFA AAM were tested. It was observed that the compressive strength of all the POFA AAM specimens with Al(OH)3 addition were lower than those of the specimens without Al(OH)3 addition. The only exception was with the POFA AAM at 2% Al(OH)3 addition in all NaOH molarities. The compressive strength losses recorded in some POFA AAM were due to weak interfacial zones creation between the activated products and the zeolitic phases, which became more apparent at higher Al(OH)3 additions. The strength development of the POFA AAM microstructure was studied with the aid of SEM/EDS, XRD and FTIR.