Microscopic Analysis of Interfacial Transition Zone of Cementitious Composites Prepared by Various Mixing Procedures
Mechanical parameters of cementitious composites differ quite significantly based on the composition of cement matrix. They are also influenced by mixing times and procedure. The research presented in this paper was aimed at identification of differences in microstructure of normal strength (NSC) and differently mixed high strength (HSC) cementitious composites. Scanning electron microscopy (SEM) investigation together with energy dispersive X-ray spectroscopy (EDX) phase analysis of NSC and HSC samples was conducted. Evaluation of interfacial transition zone (ITZ) between the aggregate and cement matrix was performed. Volume share, thickness, porosity and composition of ITZ were studied. In case of HSC, samples obtained by several different mixing procedures were compared in order to find the most suitable procedure. In case of NSC, ITZ was identified around 40-50% of aggregate grains and its thickness typically ranged between 10 and 40 µm. Higher porosity and lower share of clinker was observed in this area as a result of increased water-to-cement ratio (w/c) and the lack of fine particles improving the grading curve of the aggregate. Typical ITZ with lower content of Ca was observed only in one HSC sample, where it was developed around less than 15% of aggregate grains. The typical thickness of ITZ in this sample was similar to ITZ in NSC (between 5 and 40 µm). In the remaining four HSC samples, no ITZ was observed. In general, the share of ITZ in HSC samples was found to be significantly smaller than in NSC samples. As ITZ is the weakest part of the material, this result explains to large extent the improved mechanical properties of HSC compared to NSC. Based on the comparison of characteristics of ITZ in HSC samples prepared by different mixing procedures, the most suitable mixing procedure from the point of view of properties of ITZ was identified.
Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1132509Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 922
 J. L. Zhang, X. Liu, Y. Yuan, H. A. Mang, “Multiscale modeling of the effect of the interfacial transition zone on the modulus of elasticity of fiber-reinforced fine concrete,” Computational Mechanics, vol. 55, issue 1, pp. 37–55, 2015.
 S. Erdem, A. R. Dawson, N. H. Thom, “Influence of the micro- and nanoscale local mechanical properties of the interfacial transition zone on impact behavior of concrete made with different aggregates,” Cement and Concrete Research, vol. 42, pp. 447–458, 2012.
 T. Akcaoglu, M. Tokyay, T. Celik, “Assessing the ITZ microcracking via scanning electron microscope and its effect on the failure behavior of concrete,” Cement and Concrete Research, vol. 35, pp. 358–363, 2005.
 A. Leemann, B. Münch, P. Gasser, L. Holzer, “Influence of compaction on the interfacial transition zone and the permeability of concrete,” Cement and Concrete Research, vol. 36, pp. 1425–1433, 2006.
 Y. Ke, S. Ortola, A. L. Beaucour, H. Dumontet, “Identification of microstructural characteristics in lightweight aggregate concretes by micromechanical modelling including the interfacial transition zone (ITZ),” Cement and Concrete Research, vol. 40, pp. 1590–1600, 2010.
 T. Hemalatha, A. Ramaswamy, J.M. Chandra Hishen, “Micromechanical analysis of self compacting concrete,” Materials and Stuctures, vol. 48, issue 11, pp. 3719–3734, 2015.
 W. Li, J. Xiao, Z. Sun, S. Kawashima, S. P. Shah, “Interfacial transition zones in recycled aggregate concrete with different mixing approaches,” Construction and Building Materials, vol. 35, pp. 1046–1055, 2012.
 V. Petráňová, T. Sajdlová, J. Němeček, “Micromechanical Homogenization of Ultra-High Performance Concrete”, Applied Mechanics and Materials, vol. 821, pp. 518–525, 2016.
 J. Němeček, Z. Keršner, P. Schmidt, I. Havlíková, H. Šimonová, L. Topolář, V. Veselý, P. Rovnaník, “Fracture Process in a Fine - Grained Cement - Based Composite Monitored with Nanoindentation and Acoustic Emission,” Key Engineering Materials, vol. 662, pp. 47–50, 2015.
 J. Thomas, H. Jennings, The Science of Concrete, online textbook of the Northwestern University, cited on 15th February 2017, http://iti.northwestern.edu/cement/monograph/Monograph5_5_2.html