Characterization of viscoelastic behavior of synthetic alkali–silica reaction gels

The viscoelastic properties of ASR gels have a major impact on the gels' restrained swelling pressure and the resulting damage to concrete. This study employed a design of experiments approach to synthesize and test eighteen cylindrical ASR gel specimens of different compositions, expressed in terms of their Ca/Si, Na/Si and K/Si molar ratios. The gel cylinders were loaded uniaxially to determine their compressive strength and Poisson's ratio. In addition, the true stress−strain−time results under constant load were used, in combination with the Burgers model, to extract the viscoelastic parameters of the gels, including elastic moduli and viscosity values. These were linked to the gels' chemical composition via regression analyses. It was observed that gels with higher alkali contents had drastically reduced elastic moduli and viscosity. In contrast, the concentration of calcium in the gels generally increased such mechanical properties.