Investigation on Ultrasonic P-wave Velocity and Attenuation Parameters for Sulfate Degraded Concrete

Abstract

Concrete durability is affected due to various deterioration mechanisms. Sulfate attack on concrete is one of the major reasons for loss in mechanical properties of concrete and causes spalling and cracking. It is a mechanism, which causes a chemical break down within the concrete wherein the sulfate ions combines with C-S-H forming ettringite which destroys the cement paste (Mishra 2014).Ultrasonic pulse emission techniques was used to evaluate the extent of degradation due to external sulfate attack. In this study, the wave velocity and wave attenuation measurements are considered for the degradation analysis. The specimens were subjected to �diffusion� exposure regimen in two different solutions namely limewater (LW) and 5% sodium sulfate solution. The diametric velocities and attenuation were then calculated for a 300 kHz transient wave. This study shows that velocity decreases over time and exposure due to the degradation of concrete paste by the sulfate. But, no change in attenuation is observed in this study. This may be due to aggregates not being affected by the sulfate exposure (as attenuation depends on aggregate degradation).