Anti-foaming admixture (AFA) and its influences on the properties of a fresh self-compacting concrete mix

The properties of a concrete mix should secure the self-elimination of needless air bubbles from its volume. What is interesting, these properties are not taken into consideration in commonly used self-compacting tests. On the basis of different tests concerning self-compacting concrete mixes, it has been discovered that too high air content in their volume was a result of a superplasticiser, in spite of meeting the self-compactibility criteria. To decrease too high air volume in SCC, the use of an anti-foaming admixture (AFA) is proposed by the authors. Because of an AFA introduced into a self-compacting mix, air-content in this mix is decreased, mix flow diameter is increased and flow time is decreased. In case of a mix incorporating an AFA, its high flowability does not cause segregation of the mix, which is possible in case of SCC incorporating only a superplasticiser. However, time of introduction of an AFA is essential to get higher flowability degree, but is not important in achieving low air volume in SCC. Moreover, the workability of a self-compacting mix with an AFA keeps the same level for a longer period of time.