Performance of different grades of palm oil fuel ash with ground slag as base materials in the synthesis of alkaline activated mortar

This study examined the alkaline activated ground slag (GS) blended with different grades of palm oil fuel ash (POFA), namely: ground POFA (GPOFA), treated or calcined GPOFA (TPOFA) and ground TPOFA or ultrafine POFA (UPOFA) in the synthesis of alkaline activated GS-POFA mortar (AAG-POFA). The AAG-POFA mortars were prepared with 8M-NaOH_aq and Na₂SiO_3aq (Ms = SiO₂/Na₂O = 3.3) activators, and then cured at 60°C for 24 h. The findings showed that the grinding and calcination of POFA reduced the carbon content, loss on ignition, enhanced its fineness and increased the mineral (oxide) compositions. The grades of POFA used for the synthesis of AAG-POFA products impacted the morphologies of its microstructures, compressive strength, carbonation and amorphousity. TPOFA and UPOFA could be successfully used for the synthesis of AAG-POFA mortar with considerable structural strength. While AAG-UPOFA produced the highest mortar strength, the production of AAG-TPOFA mortar was more energy conservative. Finally, GPOFA was practically unsuitable for the synthesis of AAG-POFA as it resulted in low strength products while its mixture was characterized with low consistency, and poor dissolution or hydroxylation upon reacting with the alkaline activators.