Phosphated Comb Polymers - A New Generation of Highly Effective Superplasticizers

Author(s): Johannes Stecher, 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: 61-71
Total Pages: 11
Language: English

Abstract: One of the key aspects for self-compacting concrete is extremely high fluidity at low water to cement ratios. For the effective dispersion of such systems, comb shaped superplasticizers with optimised properties are required.

In this research, comb polymers holding phosphate instead of the carboxylate groups contained in conventional PCE products were synthesized and tested. The rational behind this approach was the high affinity of phosphate groups towards calcium ions. From this, a strong interaction with cement was expected. The phosphated polymers were compared with phosphate-free polymers of identical molecular architecture based on MPEG-methacrylate ester technology.

It was found that the phosphated polymers exhibit slightly superior dispersing performance when compared with conventional polycarboxylates, and that they retain paste fluidity better than PCEs. Their main advantage, however, is that they transform the sticky behaviour of concretes prepared at low w/c ratio with conventional polycarboxylates to one with high flow speed, especially in self- compacting concrete. Accordingly, phosphated comb polymers produce shorter V funnel empty times, faster flow in the flow line and reduced stickiness. Interestingly, the same effect was achieved by introducing only a minor amount of phosphate groups into a conventional polycarboxylate polymer.

The results signify that phosphate groups can provide different product characteristics to concrete superplasticizers, and that minor incorporations can even further fine-tune the behaviour of conventional polycarboxylates for applications in high-performance concretes such as UHPC or SCC.

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