Hybrid Lime-Pozzolan Geopolymer Systems: Microstructural, Mechanical and Durability Studies

This work studies the possibility of using geopolymer materials to enhance the mechanical and durability properties of hydrated lime-pozzolan mixtures, which gave rise to the so-called "hybrid systems". Two different waste types were used as pozzolan in the lime-pozzolan system: rice husk ash (RHA) and spent fluid catalytic cracking (FCC). The geopolymer fabricated with FCC was activated with commercial reagents (NaOH and Na₂SiO₃), and also with alternative sources of silica to obtain a lower carbon footprint in these mixtures. The alternative silica sources were RHA and residual diatomaceous earth (RDE) from the beer industry. The geopolymer mixture substituted the lime-pozzolan mixture for 30% replacement in weight. The hybrid systems showed better mechanical strengths for the short and medium curing ages in relation to the lime-pozzolan mixtures. Thermogravimetric analyses were performed to characterise the types of products formed in these mixtures. In the durability studies, hybrid systems better performed in freeze-thaw cycles and obtained lower capillarity water absorption values.