Stability of Entrained Air in Self-Consolidating Concrete Under Vibration

Fresh concrete is routinely vibrated to achieve consolidation in formwork, but over-vibration. poses a risk to the entrained air system that provides freeze-thaw durability. The mechanics of vibration, rheology, and air bubble movement are examined in this study. The experimental work considers cementitious materials and model materials under vibration using an immersion probe. The magnitude of vibration is measured by an immersed accelerometer sensor. Initial findings show aggregate volume fraction playing a strong role in determining the radius of vibrational influence. Video imagery of transparent model materials shows the movement of entrapped air at further distances from the immersion probe as the particle volume fraction increases. A better understanding of vibration of yield stress fluids and bubble buoyancy will lead to improvements in best practices for vibration of concrete.