Title: Novel Admixtures to Reduce the Stickiness of Low W/C Concretes
Author(s): Manuel Ilg and Johann Plank
Publication: Symposium Paper
Appears on pages(s): 77-88
Keywords: concrete; stickiness; superplasticizer; non-ionic co-dispersant; polycarboxylate; flow properties; V-funnel; self-compacting concrete
Concretes formulated at low water-cement ratios exhibit good material properties. Nevertheless, such concretes exhibit a honey-like consistency with a low speed of flow (“creeping behavior”) which is highly undesirable. In this paper it is shown that non-ionic small molecules can help to improve the fluidity at low water-cement ratios significantly and eliminate the “stickiness” when combined with ordinary PCE superplasticizers. For this purpose, different non-ionic glycol derivatives were screened via mini-slump testing. It was found that especially less polar species behave as very powerful co-dispersants. To gain a more profound understanding of the working mechanism, heat flow calorimetry was carried out. Additionally, concrete lab tests were performed to ascertain the impact of the non-ionic molecules on the V-funnel empty time of SCCs. Based on adsorption measurements it is inferred that the co-dispersants act as osmotic spacers which keep the cement particles apart and prevent them from agglomeration.