Effect of air entrainment on shrinkage of blended cements concretes

Shrinkage strains of air-entrained (AE) concretes were bigger than strains of non-air-entrained concretes made with the same cements. The results clearly showed an increase in strains with increasing content of air voids, regardless of cement type. Higher shrinkage strains of AE concretes may be most probably related to their microstructure of complex porosity and in particular, to porous cement paste adjacent to air void. Occurrence of air void-cement paste interfacial transition zones of higher porosity as well as their overlapping and interconnection may increase vapour diffusion accelerating moisture loss and drying shrinkage. Another likely reason for shrinkage increase may be increase in the volume of cement paste and decrease in the volume of aggregate in AE concrete.