ABSTRACT
This work analyses the changes in concrete microstructure due, first, to the amount of air-entraining agent (AEA), and then to freeze-thaw cycles. For this purpose, 5 series of concrete with different dosage of AEA have been manufactured, which have been subjected to 300 freeze-thaw cycles. In addition, the specimens were scanned with computed tomography (CT) at 0, 50, 100 and 300 cycles. The results reveal that AEA has a strong influence on pore size distribution. As the AEA increases, so does the porosity, the number of air voids and their size. However, this increase occurs up to a limit that coincides with the maximum recommended by the manufacturer. On the other hand, it seems that the series with lower AEA, characterized by a more impermeable matrix, have better freeze-thaw resistance.
