Enhancement mechanical properties of phosphoric-based geopolymer using aluminum dihydrogen phosphate

Phosphoric acid-based geopolymer (PGEO) is a acidic material, but the low strength and poor stability for the geopolymer synthesized with using fly ash limits its application and development. In this article, the aluminum dihydrogen phosphate (ADP) was introduced to form a composite activator to strengthen the mechanical strength of PGEOs synthesized from fly ash, and its hydration heat, workability, compressive strength, electrical conductivity (EC), and pHs were investigated, also the chemical and microscopic mechanism were also revealed. The results show that the geopolymerization heat was reduced after incorporating ADP activator. The workability were affected by the ADP content, the introduced ADP activator could improve the strength and long-term stability of PGEOs, and no compressive strength loss was found for the prepared geopolymer. The compressive strength reduced with EC raised with pH and, the Al–P existed in Al[OSi(P)]4 environment, and the geopolymer matrix composed of amorphous gels and crystalline compounds.