FROM DISORDERED TO ORDERED PACKINGS: A NEW PACKING MODEL FOR UHPC?

Author(s): Gerard Roquier (1)
Paper category: Proceedings
Book title: SynerCrete’18 International Conference on Interdisciplinary Approaches for Cement-based Materials and Structural Concrete
Editor(s): Miguel Azenha, Dirk Schlicke, Farid Benboudjema, Agnieszka Jędrzejewska
ISBN: 978-2-35158-202-2
e-ISBN: 978-2-35158-203-9
Publisher: RILEM Publications SARL
Publication year: 2018
Pages: 707-712
Total Pages: 6
Language : English

Abstract: A high efficiency packing model constitutes a key concept in a wide range of concrete. In a binary mixture, the peak shape at the optimum of a packing fraction curve represented as a function of the volume fraction of the fine class does not really exist, due to the compaction which is not optimal: the Compressible Packing Model (CPM) was developed with the introduction of a compaction index K. The latter is representative of the packing process efficiency and is one of the three parameters which are taken into account in the original CPM. The two other parameters are the wall effect parameter and the loosening effect parameter. Concerning this last geometrical effect, the cavity size ratio at which the loosening effect appears significantly depends of the coarse particle shape and of their surface roughness. By the introduction of a critical cavity size ratio as the fourth parameter, the CPM has evolved into the 4-parameter CPM. Herein, this model is validated both for application to disordered ternary mixtures of spherical, round aggregate and crushed aggregate particles (from K=4.7 to K=15) and for application to binary crystalline structures of alloys (K=100). The 4-parameter CPM appears to be a useful tool for predicting the packing fraction of the granular skeleton in all circumstances. The microstructure of UHPC could be thus optimized by precise gradation of all particles in the mix to yield minimum void ratio.

Online publication : 2018
Publication type : full_text
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