Air-void parameters measurement of fresh concrete

To explore the method to evaluate air-void parameters of fresh concrete rapidly, the spacing factor and specific surface of freshly mixed concrete of different air contents, different slumps and different mineral admixtures (fly ash, fly ash-slag, fly ash-slag-silica fume composite) are studied by air-void analyzer (AVA), and the correlation between the air content measured by AVA and air content determinator is compared. The results show that the spacing factor of the fresh concrete decreases firstly and then increases with the increase of air content, however the specific surface has the opposite rule. When the air content is more than 8%, the spacing factor of fresh concrete increases and the specific surface decreases. For the fresh concrete samples with similar air content, the specific surface increases firstly and then decreases with the increase of slump, but the spacing factor decreases firstly and then increases. Mineral admixture can reduce the spacing factor of fresh concrete and increase the specific surface to some degree. There is a good correlation between the air content measured by two methods, and the air content measured by AVA is about 70% of the air content measured by the air content determinator.