Anti-foaming admixture itaka susitankinancio betono misinio savybems

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. Keywords: anti-foaming admixture (AFA), decreasing the air-volume, self-compacting concrete (SCC), superplasticiser, rheological properties, workability loss. Betono misinio sudetis turi buti tokiu savybiu, kad uztikrintu nereikalingo oro kiekio pasisalinima. Idomu, kad i sias savybes dazniausiai nera atsizvelgiama atliekant susitankinancio betono bandymus. Remiantis ivairiais susitankinancio betono misinio tyrimais, buvo nustatyta, kad per dideliam oro kiekiui itakos turi superplastikliai, nepaisant to, kad jie turi tankinanciu savybiu. Norint susitankinanCio betono misinyje (SCC) sumazinti per dideli oro kieki, siuloma naudoti priesputi (AFA). Kadangi AFA iterpimas i susitankinancio betono misini sumazina oro kieki, padideja misinio pasklidimo skersmuo ir sumazeja pasklidimo trukme. Jeigu misinio sudetyje yra AFA, misinio takumas neskatina issisluoksniavimo, o tai gali atsitikti naudojant SCC tik superplastikli. Taciau AFA iterpimo trukme turi poveiki misinio takumo laipsniui, bet nera reiksminga pasiektam mazam oro kiekiui SCC. Be to, susitankinancio betono misinio su AFA klojumas ilgesni laika islieka to paties lygmens. Reiksminiai zodziai: priesputis (AFA), oro turio sumazejimas, susitankinantis betonas (SCC), superplastiklis, reologines savybes, klojumo nuostoliai.