# Durability Assessment of Alkali-Activated Geopolymers Matrices for Organic Liquid Waste Immobilization

## TL;DR

This study evaluates how well different geopolymer materials can withstand harsh conditions when used to safely contain radioactive organic waste.

## Contribution

The study introduces optimized geopolymer formulations for immobilizing radioactive organic waste under extreme thermal conditions.

## Key findings

- Oil-loaded specimens showed significant strength and microstructural degradation after cyclic climatic ageing.
- BFS matrices demonstrated the best thermal resistance due to C-A-S-H gel formation.
- Fire-exposed blank matrices retained partial mechanical integrity after thermal exposure.

## Abstract

This study investigates the mechanical and microstructural performance of three alkali-activated geopolymer formulations, constituted of metakaolin (MK), blast furnace slag (BFS), and a ternary blend of MK, BFS, and fly ash (MIX), for the immobilization of simulated radioactive liquid organic waste (RLOW). Thermal ageing tests were performed to evaluate geopolymer durability, including fire exposure (800 °C) and climatic chamber cycles (from −20 to 40 °C). Characterization through thermogravimetric analysis (TGA), compression tests, and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) was carried out to assess material degradation after thermal ageing. Preliminary results showed substantial strength and microstructural degradation in oil-loaded specimens after cyclic climatic ageing, while fire-exposed blank matrices retained partial mechanical integrity. BFS matrices exhibited the best thermal resistance, attributable to the formation of Ca-Al-Si-hydrate (C-A-S-H) gels. These findings support the use of optimized geopolymer formulations for safe RLOW immobilization, while contributing to the advancement of knowledge on sustainable and regulatory-compliant direct conditioning technology.