Effect of entrained air voids

7 The effects of entrained air on microstructure and transport properties of concrete with up to 11.5% air at different w/c 8 ratios, curing and conditioning regimes were investigated. It was found that air voids disrupt the packing of cement and 9 increase the heterogeneity of the microstructure. The width of the affected interface is around 30 μm. Gaseous 10 diffusivity and permeability are increased by up to a factor of 2-3 at the highest air contents. This effect is similar to that 11 due to increasing w/c ratio from 0.35 to 0.50 when samples are conditioned at 52% r.h or 50 ̊C. The effect on sorptivity 12 is less consistent, while the effect on electrical conductivity is influenced by the moisture condition of the air voids. It is 13 estimated that every 1% increase in air concrete increases transport by 10% or decreases it by 4%, depending on 14 whether the air voids act as conductors or insulators. 15