Rheology and Mix Design

Transcription

1 Rheology and Mix Design Aurélie FAVIER

2 Outline Introduction Basics on Rheology Overview on simple concrete rheology tests Flows regime in cementitious materials Interactions Consequences and admixtures Mix Design of Concrete Aurélie FAVIER

3 Introduction Aurélie FAVIER

4 Filling a mold Casting Visquous fluid Ordinary concrete Fluid concrete From N.Roussel Aurélie FAVIER

5 Back to basics Definition about rheology: science of flow and deformation of matter. Linked between the strain speed and the applied stress SSSSSSSSS ssssssssssss = φφ. gg. ee. sin(θθ) SSSSSSSSS rrrrrrrr = VV ee Depth Flow speed V Density Inclination Aurélie FAVIER

6 Behaviour s laws To link stress and shear rate, we introduce some behaviour s equation. The simplest is Newtonian fluid. Aurélie FAVIER

7 Yield stress fluid Yield stress for ordinary concrete : thousands of Pa Yield stress for ordinary mortar : hundreds of Pa Yield stress for cement paste : Pa Aurélie FAVIER

8 How to measure yield stress Aurélie FAVIER

9 Slump Aurélie FAVIER

10 Slump Aurélie FAVIER

11 Slump Aurélie FAVIER

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15 Behaviour type Aurélie FAVIER

16 Interactions Differents interactions: Brownian motion Collloidal interactions Hydrodynamic interactions Direct contacts Aurélie FAVIER

17 Parameters d particles diameter around 10 microns ρρ pp density of cement around 3.1 µ 0 suspending fluid ex. Water 1mPas at 25 C Φ volume fraction of solid W/B Φ = (1 + ρρ pp W/ρρ EE B) -1 Aurélie FAVIER

18 Thermal agitation kk TT wwwwwww kk BBBBBBBBBBBBBBBBBB cccccccccccccccc J at 20 C The random movement of microscopic particles suspended in a liquid or gas, caused by collisions with molecules of the surrounding medium. Aurélie FAVIER

19 Thermal agitation d -3 = number of particles in 1 cubic meter In Pa.s kkkk γγdd 3 Aurélie FAVIER

20 Colloïdal interactions In physical chemistry, the van der Waals force (or van der Waals' interaction), named after Dutch scientist Johannes Diderik van der Waals, is the sum of the attractive or repulsive forces between molecules (or between parts of the same molecule) other than those due to covalent bonds, or the electrostatic interaction of ions with one another, with neutral molecules, or with charged molecules. The resulting van der Waals forces can be attractive or repulsive. (Wikipedia) Aurélie FAVIER

21 Colloïdal interactions Electrostatic forces The surface of particles are positively charged repulsion Steric effect If you change particles charges by adding polymers or the interstitial liquid, you can modify the suspension Aurélie FAVIER

22 Colloïdal interactions At short distance the attractive Van der Waals forces dominate the electrostatic repulsion. Moreover, Van der Waals forces dominate the Brownian motion. θθ AA 0aa dd HH J Aurélie FAVIER

23 Defloculation As attractives forces dominate the system flocculation To deflocculate, we use plasticizers. Aurélie FAVIER

24 Recent development linked to the SP addition HPC High Performance Concretes UHPRC/UHPFC Ultra High Performance Reinforced / Fiber Concrete Shotcrete SCC Self Compacting Concretes 24 Aurélie FAVIER

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26 Historical development Ligninsulphonates O C Carbohydrates Naphthalinsulphonate Melaminsulphonate Vinyl Copolymer Poly-Carboxylate-Ether (PCE) H HO H H COOM C C C C OH H OH OH CH 2 OH * MeO * CH CH CH 2 CH * CO NR 1 R 2 R COONa C H 2 SO 3 Na C H 2 N n CO R 3 R 4 * CH 2 C CH 2 C * m n COOH CO-X-(CH 2 CHRO-) y R C n R C Na 2 S 2 O 5 O C CH 2 X N * N N C H2 N NH MeO N CH 2 SO 3 Na CH 2 Y n C SO 3 Na C Aurélie FAVIER

27 How? Bingham fluid τ = τ 0 + µ p γ SP By adding SP, we decrease the yield stress Aurélie FAVIER

28 Forces interpaticulaires Van der Waals Forces (attractives) Superplasticizers: Electrostatic effect to create repulsion Electrosteric effect depending on size and conformation of polymers Aurélie FAVIER

29 Effect of plasticizer on ratio W/B E/C Année Aurélie FAVIER

30 Self compacting concrete easy to cast no bleeding no vibration needs 30 Aurélie FAVIER

31 Construction speed 31 Aurélie FAVIER

32 32 Aurélie FAVIER

33 But. [Zingg et al., 2009] 33 Aurélie FAVIER

34 Conclusion about colloidal forces In Pa.s AA 0aa γγ12hh 2 dd 2 Aurélie FAVIER

35 Hydrodynamic forces When you increase the shear rate the viscous dissipation increases. And the energy of the viscous dissipation : μμ 0 γγff Φ Aurélie FAVIER

36 Hydrodynamic forces In dilute system (W/B >6): Einstein equation:ff Φ = Φ In concentrated suspensions Krieger Dougherty relation: ff Φ = (1 Φ Φ mm ) -q Aurélie FAVIER

37 Hydrodynamic forces In Pa.s μμ 0 ff Φ Aurélie FAVIER

38 Inertia In high concentrated suspension Kinetic energy : ρρ pp dd 3 VV 2 With VV = dddddd Φ So energy from inertia : ρρ pp dd 5 γγ 2 ff 2 Φ In Pa.s ρρ pp dd 2 γγff 2 Φ Aurélie FAVIER

39 Sum of energy Aurélie FAVIER

40 Volume fraction The numbers of particles plays an important role : inertia but also direct contacts. Aurélie FAVIER

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42 Other admixtures Aurélie FAVIER

43 Viscosity agents Issue: To avoid the sedimentation To increase water retention Solutions: Addition of viscosity agents such as cellulosic ethers, glucose, natural gums Aurélie FAVIER

44 How it works? C. Brumaud 2011 Aurélie FAVIER

45 Air entrainers Issue: Increase of gel resistance Solutions: Addition of air entrainers such as sulfonates or organic fatty acids, they are anionic Lemoniteur.fr Aurélie FAVIER

46 Effect on rheology For ordinary concrete, yield stress is around 2000Pa, air entrainer can help the rheo thinning. For self compacting concrete with yield stress close to 50 Pa, air entrainer helps the shear thickening of the system Aurélie FAVIER

47 References Roussel lectures ENPC Flatt lectures ETH Favier (2013) PhD dissertation Brumaud (2011) PhD dissertation Aurélie FAVIER

48 Mix design Aurélie FAVIER

49 Dreux Gorisse Aurélie FAVIER

50 Bolomey method Take in consideration the cement content PP(pppppppppppppppppppp oooo tttttttttt dddddd mmmmmmmmmmmm) = AA + (100 AA) dd DD Aurélie FAVIER

51 Software BetonLab pro ( also available for free but with restrained conditions) Based on compaction index EMMA Optimisation of packing Aurélie FAVIER

52 Bolomey and SIA Swiss standard : SIA norm : curve of Fuller B PP = 100 dd DD But cement is not included : SIA gives a minimum cement content 350kg/m3 Aurélie FAVIER

53 Loi de Feret, 1896 R = K c c + e + v 2 Résistance à la compression Constante,: Fonction de l âge, mode de conservation et liant Volumes de: c ciment e eau v vides c /(e + v) R = K c /( e + v)+1 2 Aurélie FAVIER

54 Loi de Bolomey R = K C E + V K ' Pour v < ~2% R C = σ G 0. 5 c E Aurélie FAVIER

55 Powers 3 αc R = a αc + e + v α = fraction du ciment hydraté Équivalent à: R = a( 1 P) 3 Ou P = porosité: En fonction du nombres de paramètres inconnus (a et α), cette formule n est pas pratique à utiliser Aurélie FAVIER