An investigation on geopolymerisation process of metakaolin using orthophosphoric acid and nano alumina by subjecting to thermal treatment

In this work investigation of phosphoric acid hardened Metakaolin clay with and without nano alumina before and after exposure to thermal load at 800 °C temperature has been reported. Control Specimens (M) were prepared by mixing Metakaolin, phosphoric acid (8M), and Metakaolin nano composites (M1) using 1% of Nano-alumina by weight of metakaolin. Different phases formed during the geopolymerisation and decomposition phases after heating were detected using FT-IR, XRD and micro structure by SEM (EDAX) analysis. The results showed that the nano alumina addition improved the compressive strength of mortar (M1) at room temperature to an extent of 30% to that of control (M) and further enhanced to 40 % (M1h) after thermal treatment. According to the XRD and FTIR results, inclusion of Nano-alumina powder enhanced the AlPO4 entities (Berlinite, hydrated form of aluminium phosphate) and amorphous hydrated phases. Higher amount of Al-O-P bonds with Si-O-T (T=Si,Al,P) tetrahedral units and absence of unreacted metakaolin in thermally heated samples confirmed the participation of nano alumina that accelerate the geopolymerisation reaction. Dense micro structure found in SEM micrograph which enhance the material compressive strength (28.3 MPa M1, 55.8 Mpa in M1h ) and thus has potential ceramic applications.