228-MPS : Mechanical properties of self-compacting concrete

Technical Committee 228-MPS

General Information

Chair: Prof. Kamal KHAYAT
Deputy Chair: Prof. Dr. Ir. Geert DE SCHUTTER
Activity starting in: 2007
Cluster A

Subject matter

Within concrete research, self-compacting concrete is reported to be the ‘hot topic’. Many research projects are being carried out world-wide, and this on aspects like rheology, workability, casting, mechanical properties, durability... RILEM has been very active within the field of Self-Compacting Concrete, by the organisation of RILEM Technical Committees (Committee TC-SCC on Self-Compacting Concrete chaired by A. Skarendahl, Committee TC-CSC on Casting of Self-Compacting Concrete chaired by A. Skarendahl, Committee TC-RFC on Rheology of Fresh cementitious systems chaired by Olafur Wallevik, TC 205-DSC on Durability of Self-Compacting Concrete chaired by G. De Schutter, TC-SCF on simulation of fresh concrete flow chaired by N. Roussel), and by the organisation of International Symposia (Stockholm 1999, Reykjavik 2003, Chicago 2005, Ghent 2007).

The actual RILEM Committee TC 205-DSC on Durability of Self-Compacting Concrete is finalising its work. The last meeting is planned during the RILEM Annual Week in Ghent, September 2007, in conjunction with the 5th International RILEM Symposium on Self-Compacting Concrete organised by TC 205-DSC. Within this Technical Committee, the specific durability aspects of Self-Compacting Concrete are focused on. A state-of-the-art report on this subject is actually in print (will be finished by September 2007).

It is the feeling and conviction of the members of the actual RILEM TC 205-DSC that by finalising the work on Durability of Self-Compacting Concrete, some important issues concerning SCC will still remain. One main topic in this respect is related to the Mechanical properties of Self-Compacting Concrete.

It is at this moment not fully clear whether existing design codes for structural concrete can be fully applied in case of self-compacting concrete. Some problems have been reported in the past e.g. concerning bond and shear behaviour of self-compacting concrete. Due to the lower aggregate content aggregate interlock would be less prominent in comparison with traditional concrete, which might result in a reduced bond behaviour and reduced shear resistance.

Another point of discussion is the strain-softening behaviour of self-compacting concrete under compression. It is not fully clear at this moment whether the softening behaviour of self-compacting concrete is similar to that of traditional concrete. As a consequence, can we still apply the traditional parabola-rectangular constitutive law as we do for traditional concrete? Or is there any evidence to modify the constitutive laws when dealing with SCC?

Creep and shrinkage of SCC are also heavily discussed in literature, leading to contradictory conclusions. It would be very interesting to collect the available data in this area, and with some detailed analysis and practical conclusions. Can we still apply traditional creep and shrinkage laws, or do we have to include (a) new parameter(s)?

When dealing with shrinkage, it is sometimes mentioned that SCC is showing an increased risk on early age cracking due to a possibly increased shrinkage, especially in the case of higher paste content. However, it is also clear that early age mechanical properties might be developing faster than for traditional concrete, e.g. due to the accelerating affect of some fillers like limestone powder. What is the net effect on early age cracking risk due to shrinkage and/or thermal effects?

The proposed new RILEM Technical Committee on Mechanical properties of Self-Compacting Concrete will have to gather the available information related to mechanical properties and mechanical behaviour of self-compacting concrete. Due attention should be given to the fact that the composition of SCC might be significantly different in different regions. Furthermore, it is not the intention to review the mechanical behaviour of traditional concrete. The committee will have to focus on specific mechanical aspects related to self-compacting concrete.

All relevant mechanical issues will be considered, like compressive strength and softening behaviour, tensile strength, flexural strength, elastic modulus, bond behaviour, shear strength, tension stiffening, creep, drying shrinkage, autogeneous shrinkage, restrained-shrinkage, early age cracking…

Terms of reference

The committee will comprise a selected membership of those organisations and research centres world-wide that have been active in searching for a basic understanding and modelling of mechanical properties of Self-Compacting Concrete. It will include universities, research institutes, material suppliers, contractors, building owners, public agencies... The members will also be recruited from participants in international symposiums and workshops on the topic of SCC, and from earlier RILEM TC’s dealing with SCC.

The state-of-the-art-report on Mechanical properties of Self-Compacting Concrete will be based on the following input:
- Previous state-of-the-art reports related to SCC (like ‘Casting of SCC’, ‘Durability of SCC’, ...)
- The proceedings of major international symposiums on SCC (Stockholm, Tokyo, Reykjavik, Chicago, Ghent, ...)
- Collection of data from relevant work, as published in international scientific journals
- The committee will represent a majority of ongoing research projects in this field. The committee will gather, as far as possible, the results of relevant parts of these projects

Estimated duration of the work is 3 years. The new Committee could start its activities in the fall of 2007.

Detailed working programme

- Establishing of consensus on strategy and limitation of work

- Collection and discussion of published data
- Identification of on-going projects regarding mechanical properties of SCC

- Defining a table of contents of the STAR on mechanical properties of SCC, and identifying authors
- First draft of the different chapters of STAR, by different authors

- Discussion of the first draft
- Planning of symposium

- Second draft of the STAR

- Final version of STAR, in ready to print format
- planning of symposium

Technical environment

The work will be an extension of the work in RILEM TC-CSC 'Casting of Self-Compacting Concrete”'and RILEM TC-DSC 'Durability of Self-compacting concrete'. The work will provide input to relevant standardisation-work in the field of SCC.

The TC fits into the RILEM's technical programme, in particular within the activities of cluster A ‘Mechanical performance and fracture’.

Expected achievements

The main deliverables are
- STAR on Mechanical properties of SCC
- a symposium

Group of users

- academics working with fundamental materials properties and numerical simulation of materials properties
- testing laboratories
- industrialists working with e.g. materials development
- structure designers

Specific use of the results

The results will contribute to a more precise design of concrete structures with self-compacting concrete. The potential risks and opportunities related to the use of SCC, if any, will be made clear. This will contribute to a more advanced use of SCC within concrete construction.