Improvement of SCC Flow Properties through Addition of Non-Adsorbing Small Molecule Co-Dispersants

Author(s): Manuel Ilg, Johann Plank
Paper category: Conference
Book Title: 8th International RILEM Symposium on Self-Compacting Concrete - SCC 2016
Editor: Kamal H. Khayat
ISBN: 978-2-35158-156-8
e-ISBN: 978-2-35158-157-5
Publisher: RILEM Publications SARL
Publication year: 2016
Pages: 49-59
Total Pages: 11
Language: English

Abstract: Colloidal suspensions such as e.g. cement pastes can be dispersed either through electrostatic or steric repulsive forces. These mechanisms require that the polymers applied adsorb onto the particle surface. However, it has been noticed recently that also non-adsorbing non-ionic polymers can significantly enhance the plasticizing effect of MPEG ester-based polycarboxylate (PCE) superplasticizers, especially at low w/c ratios (≤ 0.30).

In this study, the effect of non-ionic small molecules on the dispersing ability of two IPEG-based PCEs exhibiting different side chain densities was investigated. As non-adsorbing molecules, diethylene glycol and a polyether amine were probed. It was found that the non-adsorbing molecules can provoke a considerable increase of cement paste flow when combined with IPEG-PCEs. The effect is particularly strong for PCEs possessing high anionicity and at very low w/c ratios (< 0.25) in cement paste. Furthermore, V-funnel empty times of mortars revealed that the non-adsorbing molecules also improve the flow speed and reduce the stickiness of such concretes.

Our investigations suggest that non-ionic, inexpensive small molecules can act as co-dispersants for PCE superplasticizers. They can help to optimize the cost of the admixture and also provide a concrete which can be placed faster. Mechanistic considerations suggest that the non-ionic co-dispersants present spacer molecules which through an osmotic effect keep the cement particles apart.

Online publication: 2016
Publication Type: full_text
Public price (Euros): 0.00