209-RFC: Rheology of cement based materials such as fresh concrete

Organizers / Managers

Technical Committee 209-RFC

General Information

Chair: Dr. Ólafur WALLEVIK
Deputy Chair: Prof. Mette GEIKER
Activity starting in: 2004
Cluster B

Subject matter

For cement based materials (concrete, mortar and cement paste) there is an increasing need for fundamental knowledge in order to control their rheological properties and their time and temperature dependence. Such properties determine the handling characteristics of the fresh concrete as well as its stability, i.e. the ability to prevent segregation. These are crucial issues at the building site. The need for fundamental rheological knowledge is increasing as a result of more frequent use of new materials such as blended multi-powder cements, fillers, various industrial by-products and a new generation of more effective plasticizing admixtures. New concrete types pose new demands; particularly SCC, i.e. a concrete that can be placed in complicated formwork without any mechanical assistance. The group will evaluate critical mechanisms that control the rheological properties of cement-based materials.

The idea is to bring forward a contribution to the fundamental understanding of the rheological properties of cement based materials. Such understanding will form the basis for a better control of these properties and thereby, improved effectiveness on the building site.

Some keywords are
· Thixotropy
· Thixotropic-strength
· Gel-strength
· Coagulation- and dispersion rate
· Electrostatic- and steric stabilization
· experimental error
· limitation of measurements

Terms of reference

The committee comprises a selected membership of those relatively few organisations and research centres worldwide that have been active in searching for a basic understanding and modelling of the rheological behaviour of cement based material. It includes universities, research institutes, material suppliers, contractors, building owners, public agencies and representatives from international associations and standardi-sation bodies.

This aim is to be reached with a review of the current state-of-the-art knowledge. Report of the result will be made with in mind the practical use of this type of science. The point is to limit the task group with the relevant state-of-the-art theory in a clear manner and not make a too ambitions plan which will be hart to fulfill.

Detailed working programme

 24 November  2004: First planeraring meeting Copenhagen
 Mars  2004: First working meeting during the RILEM days in Chicago
 August  2004: TC meting and workshop  During Nordic Rheology Conference Iceland
 February 2005: TC meting
 September 2005: Symposium
 December 2005: Final report – RILEM publications

Technical environment

Expected achievements

The overall results of the group is planned to be reported in a RILEM publication. Additionally, a workshop is planned, as well as a symposium in 2 or 3 years. Terminology will likely not be addressed. The plan is rather to sick to the British standard as much as possible.

Group of users

- Academics working with fundamental materials properties and numerical simulation of materials properties
- Testing laboratories
- Industrialists working with e.g. materials development

Specific use of the results

The results will contribute to a more precise design of concrete structures with respect to the risk of bad mix design, unexpected rheological behaviour, and thus, to extended life time and less repair of concrete structures. The economic impact is, thus, significant.

Also, the work will improve the fundamental understanding of the rheological behaviour of cement-based material, which is a requisite to design more robust concretes.