Prediction of ultrasonic pulse velocity and physicochemical properties of rice husk ash concrete exposed to elevated temperatures and post-fire curing

The novelty of this study is its evaluation of the physicochemical properties and non-destructive testing performance of concrete containing rice husk ash (RA) subjected to post-heating curing. The study examines temperatures of 300°C, 500°C, and 700°C. Post-heating curing was performed in water and in air for 28 and 56 days. Ultrasonic pulse velocity (UPV), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric (TG)/differential thermogravimetric (DTG) analysis were determined to evaluate thermal damage and recovery mechanisms. Predictive relationships between UPV and the outcomes of destructive tests were established, allowing the condition of the concrete to be estimated without relying solely on destructive methods. The high R-squared values, ranging from 0.83 to 0.98, confirm that UPV is a reliable indicator of thermal damage and recovery. Physicochemical analyses highlighted the rehydration and pozzolanic activity of RA, with 8% RA recovering 36.7% compressive strength after 56 days of water re-curing. A statistical optimization using the Taguchi method and ANOVA was additionally performed to identify the most effective parameters influencing strength recovery. Post hoc Tukey HSB was used to compare RA levels and temperatures. Optimization results highlighted that 8% RA content provided the most significant improvement in recovery behavior, particularly under water re-curing conditions. Finally, a life cycle assessment (LCA) was conducted to evaluate the environmental impacts of the studied concrete mixtures. This assessment showed that incorporating RA significantly lowered environmental impacts, reducing global warming potential by 21.3% and resource depletion by 24.8%. • Physicochemical and non-destructive evaluation of rice husk ash concrete after fire and re-curing • Predictive modeling of strength based on ultrasonic pulse velocity • Environmental impact analysis of rice husk ash concrete using life cycle assessment • Re-curing enhanced recovery in rice husk ash concrete through continued pozzolanic activity. • Rice husk ash increased resistance to thermal degradation in concrete.