Engineering MECHANICS, Vol. 21, 2014, No. 4, p. 257–268 257 MATERIAL PARAMETERS OF CEMENT AND ALKALI ACTIVATED FLY ASH BASED CONCRETE: LABORATORY MEASUREMENTS AND NUMERICAL SIMULATION Michal ˇ Sejnoha*, Miroslav Brouˇ cek*, Eva Novotn´ a* Zbynˇ ek Kerˇ sner**, David Lehk´ y**, Petr Frant´ ık** The paper reports on the determination of basic mechanical material parameters of several concrete and alkali activated concrete and fly ash mixtures intended for the construction of segmental lining used in TBM tunneling. The results of an extensive experimental program are discussed first. The principal attention is accorded to the experimental determination of specific fracture energy from a load-deflection curve, which, when compared to numerical simulations, shows certain inconsistency with the measurements of other material data. This is supported by the derivation of the data from inverse analysis employing the elements of soft computing. Dynamic simulation of crack propagation experiments is suggested to reconcile the essential differences and to identify the most important impacts affecting the results of experimental measurements. Keywords : alkali activated fly ash, concrete, fracture energy, finite element simula- tion, soft computing 1. Introduction Massive increase of CO 2 emission in recent years has supported a considerable effort to- wards substitution of ordinary Portland cement by alkali-activated aluminosilicate materials such as fly ash in the production of concrete. Using fly ash as admixture in cements is now common in many applications. Full substitution for large scale structural units, however, is still at its infancy and to foster its progress beyond laboratory samples will require fundamen- tal understanding of what is occurring already on the level of paste during alkali-activation process. Starting with recent accomplishments by [1] we expect considerable activity in this field in the coming decade. This topic, however, goes beyond the present scope. Instead we focus our attention on the macroscopic evaluation of the response of various specimens of mixtures of concrete and alkali-activated materials with emphases on the influence of fly ash replacing either a certain portion or an entire amount of cement. We report on both experimental and numerical part of this research effort as these should be considered on the same footing to mutually corroborate the obtained results. * prof. Ing. M. ˇ Sejnoha, Ph.D., DSc., Ing. M. Brouˇ cek, Ph.D., Ing. E. Novotn´ a, Ph.D., Czech Technical Uni- versity in Prague, Faculty of Civil Engineering, Th´akurova 7; 166 29, Prague; CZ ** prof. Ing. Z. Kerˇ sner, CSc., Ing. D. Lehk´ y, Ph.D., Ing. P. Frant´ ık,Ph.D., Brno University of Technology, Faculty of Civil Engineering Veveˇ r´ ı 331/95 602 00 Brno; CZ
MATERIAL PARAMETERS OF CEMENT AND ALKALI ACTIVATED FLY ASH BASED CONCRETE: LABORATORY MEASUREMENTS AND NUMERICAL SIMULATION
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