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FA 2.1 Robust and highly flowable concrete with controlled surface quality

FA 2.1 Robust and highly flowable concrete with controlled surface quality

Objectives:

  • Reliable design and production to obtain stable, robust and economical highly flowable concrete for buildings
  • To establish specifications and guidelines to obtain required surface qualities
Project manager: Klaartje De Weerdt
Disiplinary responsibre: Professor Stefan Jacobsen
PhD: Ya Peng
International advisor:                                         Olafur Wallevik, ICI, Iceland
   
There was a close cooperation with FA 2.3.


The project included the following activities:

  • Design and testing of stable and robust highly flowable concrete
  • Development of an objective tool for characterisation of concrete surfaces.

Main Topics

Robustness of self-compacting concrete, SCC

One obstacle for more extended use of SCC is the lack of understanding on concrete stability, and simple tools for describing and control of stability. The work revealed that some commonly used stability test methods, static stability methods in particular, do not reflect the stability challenges occurring on site. A recommendation is given based on comparison with in-field behaviour. The fundamental stability principles of the matrix phase are investigated by the use of a proposed conceptual model for sedimentation and bleeding. A new sedimentation test method for fresh matrix was developed based on continuous recording of the pore water pressure at various heights.

Concrete surface classification

The goal is to develop a classification tool in order to describe smooth formed concrete surfaces objectively, in order to avoid subjective descriptions leading to misunderstandings and timeconsuming and expensive conflicts for owners, architects and construction companies. In the suggested classification system, greyscale variations and pore size and distribution are the main parameters. The system is based on pictures. A prerequisite is then to find a procedure that always gives the same light conditions during photographing. This is solved by using a "soft box" (large umbrella). The pictures are then managed in a Matlabbased software, called "BetongGUI" (will commercially available) with two separate functions; pores and greyscale variations. A prototype was developed and offered the industry for testing.