Air Entraining Agents in Road Concretes and Characterization of the Air Void System in the Fresh Concrete

Various air-entraining agents were investigated for their physicochemical characteristics and for their foaming power. Correlations were found between this power and the parameters characteristic of entrained air. These parameters were determined on the fresh concrete using the DBT "Air Void Analyser". Air-entrained concretes have a water absorption very similar to that of conventional road nnretes, in spite of a higher total porosity. As a result, the degree of saturation obtained is markedly lower. Resistance to scaling in the presence of de-icing salt is considerably improved by the use of an air-entraining agent. However, it is rather difficult to gain control of the use of this type of admixture: its efficiency is highly dependent on the cement type, the sand type and the time elapsed between concrete manufacturing and laying.