Moisture stability of crystalline alkali-silica reaction products formed in concrete exposed to natural environment
Andreas Leemann, Zhenguo Shi, Mateusz Wyrzykowski, Frank Winnefeld
Abstract
Crystalline ASR products were extracted from concrete exposed to natural environment and analyzed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, Raman microscopy, X-ray diffraction and dynamic water vapor sorption. All extracted samples display similar compositions and Raman spectra. They sorb a limited amount of water vapor between 70 and 97% relative humidity (RH), amounting to 13–25 mass-%. Three different phases are identified, with d-spacings at low diffraction angles of 13.4, 12.3 and 10.8 Å. However, none of the phases show a change in d-spacing going from dry (~50% RH) to moist (~100% RH) conditions, indicating that no extra water is sorbed in the interlayer. This clearly indicates that swelling of crystalline ASR products is not responsible for stress generation and concrete cracking.