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Partner logo here 1 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid Project # 12 – Multiscale modelling Denis Davydov (PhD student) Milan Jirásek.

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Presentation on theme: "Partner logo here 1 Nanocem-RTN T0+20 Semi-Annual Meeting 10-2007 Madrid Project # 12 – Multiscale modelling Denis Davydov (PhD student) Milan Jirásek."— Presentation transcript:

1 Partner logo here 1 Nanocem-RTN T0+20 Semi-Annual Meeting Madrid Project # 12 – Multiscale modelling Denis Davydov (PhD student) Milan Jirásek (supervisor) Bruno Capra (industrial partner) Henrik Stang (academic partner)

2 Partner logo here 2 Nanocem-RTN T0+20 Semi-Annual Meeting Madrid Multiscale modelling July 10th, 1983 Born in Perm city, Russia (USSR) Sept – June 2000 Lyceum of Perm State Technical University, Russia. Sept – June 2004 Bachelor degree in Applied Mathematics and Computer Science, Department of Mathematical Modeling of Systems and Processes, Perm State Technical University, Russia. Graduation thesis on “Model for superplasticity”. Distinction: cum laudae. Sept – June 2006 Master degree in Applied Mathematics and Computer Science, Department of Mathematical Modeling of Systems and Processes, Perm State Technical University, Russia. Graduation thesis on “Uniaxial strain stability study problem of the nonlinear viscous material”. Distinction: cum laudae. Feb – present PhD research at Faculty of Civil Engineering, Czech Technical University, Prague. MC-RTN Project nr 12. “MULTISCALE MODELLING”

3 Partner logo here 3 Nanocem-RTN T0+20 Semi-Annual Meeting Madrid Multiscale modelling Objectives: Analysis of the role of loading rate in nanoindentation test, understanding and evaluation of the visco-elastic properties from nanoindentation. Extension of models for micromechanical properties of cement paste to time-dependent behavior. FEM approach as a homogenization technique at the scale of cement paste. Extension of multiscale model for concrete to time-dependent behavior. This includes analytical homogenization at the scale of mortar and concrete. Preliminary study on possible extension to inelastic phenomena such as cracking and plastic deformation.

4 Partner logo here 4 Nanocem-RTN T0+20 Semi-Annual Meeting Madrid Multiscale modelling Deliverables: Procedures for evaluation of nanoindentation tests taking into account the influence of loading rate. Numerical FEM simulation tool for viscoelastic properties of cement paste. Multiscale model for viscoelastic properties of mortar and concrete. Extension of the homogenization analytical techniques for the visco-elastic deformation. Recommendations for further investigation of inelastic properties of cement paste. DatePlacementBrief description CTU Micromechanical creep simulations; homogenization at the level of cement paste. Methodology for determination of viscoelastic properties Oxand Extension of multiscale model to viscoelastic behavior CTU Comparison between analytical and numerical homogenization techniques. Verification of predicted viscoelastic properties DTU Preliminary investigation of possible extension of micromechanical models to fracture analysis CTU Preparation and defense of PhD dissertation

5 Partner logo here 5 Nanocem-RTN T0+20 Semi-Annual Meeting Madrid Multiscale modelling Accomplishment during the first reporting period is Literature survey on: Chemistry, morphology, hydration kinetic Creep and shrinkage effects Models of the CSH structure and creep theories Creep modeling from engineering point of view Thermo-chemo-mechanical couplings Homogenization, Eshelbian approach, multiscale models Analytical solutions for indentation problem and dimensionless analysis

6 Partner logo here 6 Nanocem-RTN T0+20 Semi-Annual Meeting Madrid Multiscale modelling P Force E0E0 E1E1 R What is the error of Oliver-Pharr procedure of extracting elastic properties induced by experimental hypothesis of half-space homogeneous media? Difference between E 0 and E 1 |E0-Eop|/E0 - error h/R - dimensionless depth tang Difference between E0 and E1 |E0-E1|/E0 -

7 Partner logo here 7 Nanocem-RTN T0+20 Semi-Annual Meeting Madrid Kelvin-Maxwell-Voight visco-elastic model time sec Penetration depth nanometres Multiscale modelling Numerical modelling of the nanoindentation experiment experiment Norton’s visco-plastic model Too deep!!! (1.5micron) homogenized respond of surrounding rather then some phase of interest

8 Partner logo here 8 Nanocem-RTN T0+20 Semi-Annual Meeting Madrid Multiscale modelling 1) Perform nanoindentation experiments into specific places of cement paste to better capture intrinsic properties 2) Use different loading rates to distinguish better between viscous and plastic deformation and have several cycles 3)Try analytical and numerical fitting nanoindentation curves with visco- elastic creep and visco-plastic Norton model. Compare the results 4)Estimate a minimum area of the phase needed for reliable results “matrix” approach to the indentation measurements

9 Partner logo here 9 Nanocem-RTN T0+20 Semi-Annual Meeting Madrid Multiscale modelling Indent. Module M=E/(1-nu^2) All products (matrix) HD-CSH only (manual) All productsHD-CSH mean Std. dev time force Experimental programs to use: C 3 S Alite grain Turned out to be Belite Fit model on one experiment And check on another!

10 Partner logo here 10 Nanocem-RTN T0+20 Semi-Annual Meeting Madrid NEW IDEAS : Deviatoric creep (same for LD and HD) Porosity (different for LD and HD) + Self-Consistent Upscaling with Eshelby Solution = Like a Granular Media LD and HD CSH

11 Partner logo here 11 Nanocem-RTN T0+20 Semi-Annual Meeting Madrid NEW IDEAS : Force UPSCALING (Self-Consistent Scheme) Deviatoric creep (same for LD and HD) Porosity (different for LD and HD) + Self-Consistent Upscaling with Eshelby Solution = Like a Granular Media Indentation experiment: LD and HD CSH

12 Partner logo here 12 Nanocem-RTN T0+20 Semi-Annual Meeting Madrid NEW IDEAS : Force UPSCALING (Self-Consistent Scheme) Deviatoric creep (same for LD and HD) Porosity (different for LD and HD) Volumetric & deviatoric creep + Self-Consistent Upscaling with Eshelby Solution = Like a Granular Media Indentation experiment: LD and HD CSH

13 Partner logo here 13 Nanocem-RTN T0+20 Semi-Annual Meeting Madrid NEW IDEAS : Force UPSCALING (Self-Consistent Scheme) Deviatoric creep (same for LD and HD) Porosity (different for LD and HD) Volumetric & deviatoric creep + Self-Consistent Upscaling with Eshelby Solution = Like a Granular Media Use of elaborated analytical Solution based on one, published by Vandamme to fit Deviatoric creep properties From LD and HD CSH Indentation experiments Indentation experiment: LD and HD CSH

14 Partner logo here 14 Nanocem-RTN T0+20 Semi-Annual Meeting Madrid NEW PROBLEMS : machine precision Before: After: Hope to have HD CSH here Unhydrated grain Points to indent Real indents (with shift!)

15 Partner logo here 15 Nanocem-RTN T0+20 Semi-Annual Meeting Madrid NEW PROBLEMS : hard to identify/indent HD

16 Partner logo here 16 Nanocem-RTN T0+20 Semi-Annual Meeting Madrid NEW IDEAS (2): Use another indentation machine with higher precision, with AFM, but with bad optics Find “good” grains in advance using BSE/electron microscope. AFM gradient map BSE AFM grain End of HD zone indent

17 Partner logo here 17 Nanocem-RTN T0+20 Semi-Annual Meeting Madrid Effect of the not straight surface: Force Contact square has changed, So the Oliver-Pharr procedure Will give inappropriate results. Is it possible at all to use that Procedure in such a case???

18 Partner logo here 18 Nanocem-RTN T0+20 Semi-Annual Meeting Madrid Recent work:

19 Partner logo here 19 Nanocem-RTN T0+20 Semi-Annual Meeting Madrid Recent work (2): ? Is it good quality mix/clinker!?

20 Partner logo here 20 Nanocem-RTN T0+20 Semi-Annual Meeting Madrid Recent work (3):

21 Partner logo here 21 Nanocem-RTN T0+20 Semi-Annual Meeting Madrid MATRIX vs MANUAL Is it possible at all to access Properties of the phase of Interest by matrix method? Success will probably depend on ratio between characteristic size of the phase and distance between the indents. BUT in order to have indents close to each other one has to do small depths, which, from the morphological point of view for CSH, has to be greater then 100nm Does it worth trying to chose right indents from big matrix?

22 Partner logo here 22 Nanocem-RTN T0+20 Semi-Annual Meeting Madrid Multiscale modelling Perspectives: 1.Have more reliable procedure for nanoindentation of cement phase (with manual method or with choosing indents from a “matrix” method) 2.Better understand viscous and plastic behaviour during loading phase of indentation using different indentation rates 3.Have reliable results for cyclic loading by manual choice of indentation points and maximum penetration depth 4.Come up with a reliable model to describe the indentation experiment

23 Partner logo here 23 Nanocem-RTN T0+20 Semi-Annual Meeting Madrid Multiscale modelling Questions (Chemistry and Sample preparation/mixing): 1.What is the good C/S ratio for HD/LD CSH? 2.It is necessary to have a fresh, very well mixed and vibrated cement in quite a big amount (for good mixing) to provide “homogenous” hydrated paste without air bubbles, bunches of agglomerated aggregates. It is very important for good polishing. 3.Presence of Phosphor?? 4.Lots of Portlondite in paste?? 5.The best cement for that purpose?? (white/gray/…) Questions (Mechanical/Mathematical): 1.HD CSH zone and indents are often situated on the slope. Corrections to Oliver-Pharr? 2.Statistical lack of experimental curves in manual method to be representative, very time consuming. 3.Do properties of the CSH change in time?? What is right age to make indents??? According to some experiments (??) after one year the creep is recoverable absolutely. 4.Problems with manual indentation, machine precision or HD CSH finding

24 Partner logo here 24 Nanocem-RTN T0+20 Semi-Annual Meeting Madrid Multiscale modelling Thank you for you attention!


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