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

• Published in: Construction & building materials 2023-12, Vol.407, p.133538, Article 133538
• Main Authors: Sim, Sungwon, Rhee, Jeong Hoon, Oh, Jae-Eun, Kim, Gun
• Format: Article
• Language: English
• Subjects: Durability; Fly ash; Ground-granulated blast-furnace slag; Microcracking; Thermal damage
• ISSN: 0950-0618
• DOI: 10.1016/j.conbuildmat.2023.133538

•This study investigates thermal durability enhancement via cement replacement.•GGBFS and fly ash mitigate microcracking under high temperatures.•Nonlinearity parameter detects transition from micro to macroscale defects.•Results confirm the physicochemical evidence such as the decomposition of CH.•GGBFS and fly ash reduce cement dosage while enhancing structural integrity. 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).