Machine Learning–Enhanced Integrated Assessment of Thermal and Radiation Shielding Performance Degradation in GGBFS-Based Geopolymer Concrete: Quantifying Microstructural Damage and Optimizing Mix Design for Nuclear Applications

This study presents a comprehensive investigation into the concurrent thermal and radiation shielding performance of ground granulated blast furnace slag (GGBFS)-based geopolymer concrete (GPC) exposed to temperatures up to 600°C for durations of up to 120 min. Although GPC is widely acknowledged for its enhanced fire resistance and environmental benefits over ordinary portland cement (OPC) concrete, its dual functionality as a load-bearing and radiation-shielding material under thermal stress has not been rigorously quantified. This work bridges that gap by integrating mechanical, radiological, and microstructural analyses, directly linking thermally induced damage—such as dehydration, porosity growth, and microcracking—to measurable declines in performance. Experimental results (mean ± SD and n = 5 ) showed that after 120 min at 600°C, compressive strength decreased by 59.4%, from 36.47 ± 1.82 to 14.81 ± 0.74 MPa . Concurrently, the gamma ray linear attenuation coefficient and neutron removal cross section diminished by 36.5% and 25.3%, respectively, accompanied by marked increases in half-value and 10th-value layer thicknesses. A critical thermal threshold was identified near 400°C, beyond which degradation accelerates in a nonlinear manner. Statistical validation and machine learning models [artificial neural network (ANN), support vector machine (SVM), and long short-term memory (LSTM)] confirmed temperature and porosity as the dominant degradation drivers. Furthermore, mix design optimization via a genetic algorithm demonstrated that adjusting GGBFS content and Na 2 SiO 3 /NaOH ratios can recover up to ∼ 10 % of lost performance at 600°C. These findings challenge the assumption that GPC’s inherent fire resistance ensures reliable multifunctionality in nuclear applications, underscoring the necessity of thermally tailored geopolymer composites for extreme environments.