Determination of ASR in Concrete Using Characterization Methods

Basaltic rocks are the main source of local crushed rock aggregate for concrete in their region. Basaltic rocks are also potential rocks for alkali–silica reaction (ASR). ASR is a complex mechanism that deteriorates concrete via creating volumetric expansion over time between the reactive silica in the aggregate and the alkali components in Portland cement. However, due to the multi-scale nature of this long-term phenomenon, understanding its mechanism in concrete structures remains difficult to assess. In this study, the morphology and analytical composition of three groups of concrete prepared with basalt aggregate, basalt aggregate with 20% fly ash substitution of cement, and limestone aggregate were analyzed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDX); it was characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and differential thermal analysis (DTA) and compared with the ASR structure. The (Na + K)/Si and Ca/Si ratios in SEM/EDX analysis and the water peaks in FT-IR and TGA analyses will help to determine the footprint of ASR.

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