Department of Mechanics: Seminar: Abstract Konigsberger 2016
Application of continuum micromechanics for multiscale analysis of cementitious materials: poroelasticity and creep
Markus Königsberger, Bernhard Pichler, and Christian Hellmich
TU Wien – Vienna University of Technology, Institute for Mechanics of Materials and Structures
June 10, 10:00, Thákurova 7, 166 29 Prague 6, room B366
ABSTRACT:
Cementitious materials, such as mortars or concrete, exhibit a complex heterogeneous microstructure, built up by different hydrates, pores, voids, and unhydrated cement clinker. Continuum micromechanics approaches have proven to be useful to tackle the multiscale characteristics of the material, due to their predictive nature, their limited number of involved parameters, and their time- efficient computations. After a brief overview of the fundamentals of multiscale continuum mechanics of microheterogenous materials, this talk focuses on two applications developed very recently: A bottom-up approach for prediction of poroelastic properties of hydrating cement paste [1], and a top- down approach to identify the hydrates’ creep properties [2]. It is shown how upscaling of the solid C-S-H stiffness as well as the pore pressures within gel and capillary pores can explain the poroelastic bevior on the macroscopic scale of cement paste. Thereby, we explicitly consider that the C-S-H gel densifies during ongoing hydration, and quantify this densification by a hydration model [3], developed on the basis of NMR relaxometry measurements [4]. We also show that experimentally observed age- and composition-dependent creep behavior can be traced back to intrinisic (i.e. age- and composition- independent) viscoelastic behavior of the hydrates by downscaling 500 three minute-long creep tests performed during the first days of hydration [5].
REFERENCES:
[1] M. Königsberger, B. Pichler, and C. Hellmich. Molecular-to-continuum poroelasticity upscaling of hydrating cement pastes considering progressive C-S-H-gel densification. In preparation
[2] M. Königsberger, M. Irfan-ul-Hassan, B. Pichler, and C. Hellmich. Downscaling-based identification of non-aging power-law creep of cement hydrates. Journal of Engineering Mechanics, 2016. Under revision.
[3] M. Königsberger, B. Pichler, and C. Hellmich. Densification of C-S-H is mainly driven by available precipitation space, as quantified through an analytical cement hydration model based on NMR data. Cement and Concrete Research, DOI 10.1016/j.cemconres.2016.04.006, 2016.
[4] A.C.A. Muller, K.L. Scrivener, A.M. Gajewicz, and P.J. McDonald. Densification of C-S-H measured by 1H NMR relaxometry. The Journal of Physical Chemistry C, 117(1):403-412, 2012.
[5] M. Irfan-ul-Hassan, B. Pichler, R. Reihsner, and C. Hellmich. Elastic and creep properties of young cement paste, as determined from hourly repeated minute-long quasi-static tests. Cement and Concrete Research, 82:36-49, 2016