MEAN SPACING OF AIR VOIDS IN HARDENED CONCRETE

Geometric probability concepts and stereological principles are used t o derive an equation for the mean spacing of air voids in hardened con crete. The equation is sBAR = 2p2/alphaA where sBAR is the mean sparin g, p is the volume fraction of paste in the concrete, A is the volume fraction of air in the concrete, and a is the specific surface of the air voids. Thus, the input parameters for the equation are the same as those obtained from the standard air-void system analysis of hardened concrete. The equation is valid for all values of paste-to-air ratio, p/A. The mean spacing yields a better estimate of the actual spacing of the air voids in hardened concrete than the standard spacing factor .