Enhancing the durability performance of thermally damaged concrete with ground-granulated blast furnace slag and fly ash

Abstract

This study investigates the effectiveness of ground-granulated blast furnace slag (GGBFS) and fly ash in improving the durability of concrete specimens subjected to thermal damage. Multiple techniques, including nonlinear impact resonance acoustic spectroscopy (NIRAS), compressive strength, X-ray diffraction, and thermogravimetry, are employed to capture the physical and chemical phenomena resulting from a temperature elevation of 200, 400, 600, and 800 ◦C. The experimental results demonstrated that replacing cement with fly ash (20 wt%) and GGBFS (40 wt%) yields significant mitigation of microcracking development, highlighting their potential as agents for enhancing concrete durability under high-temperature exposure. Notably, the hysteresis nonlinearity parameter (α) measured using NIRAS exhibits a high sensitivity for detecting the transition from micro to macroscale defects, and the trend of α sufficiently coincides with the results of the mineralogical analyses, confirming the evaporation of free water, dehydration of calcium silicate hydrate (C-S-H), and decomposition of calcium hydroxide (CH).