THREE DIMENSIONAL ANALYSIS OF AIR VOID SYSTEMS IN CONCRETE

Abstract

The addition of an entrained air void system in concrete to reduce damage from freeze-thaw cycles may be considered one of the great technological advances in building materials in the last 50 years. This is despite the fact that we are not completely clear how and why it is so effective. To help shed light on these questions, we have applied a high-resolution 3D imaging technique to analyze an entrained air void system in concrete. X-ray microtomography allows us to image the internal structure of materials at spatial resolutions approaching 1 micron. 3D image analysis techniques can be used to extract quantitative measurements from the images. Using these techniques, the entrained air system in four different concretes was measured. Sample measurements include void-size distributions, air bubble spacing factors, and connectivity of the void system. These measurements allow us to challenge conventional assumptions on the internal void system in concrete.