Evolution of viscosity of concrete under sulfate attack

This paper presents a theoretical and experimental study on the attenuation coefficient of the ultrasonic expansion wave in concrete specimens made of different mixes and suffering from sulfate attack. The relationships between the attenuation coefficient, relaxation time, and the wave velocity of the elastic expansion wave were derived. By using simple ultrasonic techniques, the variation of the attenuation coefficient with time during the process of sulfate attack was determined experimentally. The results showed that the magnitude of the attenuation coefficient of concrete increased with time, reflecting damage evolution in the material caused by sulfate attack. This suggested that the damage caused by sulfate attack in concrete can be determined by using simple ultrasonic testing methods. Also, it was found that the concrete specimens with added fly ash had a better performance (reduced sulfate attack) than those with added fine ground slag.