FRENCH INSTITUTE OF SCIENCE AND TECHNOLOGY FOR TRANSPORT, DEVELOPMENT AND NETWORK PHYSICO-CHEMICAL INSIGTH ABOUT THE LIME TREATMENT OF SOILS

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1 FRENCH INSTITUTE OF SCIENCE AND TECHNOLOGY FOR TRANSPORT, DEVELOPMENT AND NETWORK PHYSICO-CHEMICAL INSIGTH ABOUT THE LIME TREATMENT OF SOILS Dimitri Deneele 1st TERRE School Fundamentals of an interdisciplinary approach to design and climate adaptation of geo-infrastructure Naples, september 216

2 Context EARTHWORKS Soil stabilisation with binders Use of lime and/or cement Subbasesfor infrastructure development To use the materials located in the land projects 2

3 Lime stabilisation mechanisms 1% < [Lime] in mass< 5% Short-term effect Long-term effect / pozzolanic reaction POZZ + LIME + WATER Hydrates ph> 12 Dissolution Si, Al,.Ca C-S-H/C-A-S-H Plasticity Swelling potential Mechanical strength 3

4 Evolution of mechanical properties Bell et al EG

5 Scientific locks What are the physico-chemical mechanisms leading to an improvement of the mechanical properties during soil stabilization? Model Natural materials soils KAOLINITE SMECTITE Al 4 Si 4 O 1 (OH) 8 (Na,Ca),3 (Al,Mg) 2 Si 4 O 1 (OH) 2.nH 2 O 5

6 Scientific locks What are the physico-chemical mechanisms leading to an improvement of the mechanical properties during soil stabilization? Durability of soil stabilization (leaching)? 6

7 Multi-disciplinary and multi-scale approach Chemo-hydro-mechanical approach in soils stabilisation LARGE SCALE SMALL SCALE Thermal Analysis FTIR Zetameter Solid state NMR XRD SEM, TEM 7

8 % Ca(OH)2 & Hydrates % Ca(OH)2, hydrates Résistance à la compression simple (kpa) Macro-Micro coupling Macro and global analysis! Ca(OH) 2 1 RC Unconfined compressive strength (Mpa) Hydrates Temps de cure Curing time Maubec et al. 216 ACS 8

9 % Ca(OH)2 & Hydrates % Ca(OH)2, Hydrates Résistance à la compression simple (kpa) Macro-Micro coupling Macro and global analysis! 3,5 3 Ca(OH) 2 RC ,5 2 1,5 Hydrates UCS (MPa) 1 6,5 4 2 Curing time Temps de cure Maubec et al. 216 ACS 9

10 Description of the pozzolanic reaction From global analysis to atomic environnement! * * 98 days * * 28 days Q2 * * 7 days * Q 1 * 3 days * * 1 day d, ppm Pomakhina et al. 212 CCR 1

11 Amopunt of Si (grams) Description of the pozzolanic reaction 2 Mineralogical contribution 1,5,4 Montmorillonite 1,2, C-A-S-H Cristobalite Curing time (days) Amount (1-3 mol) Time (days) non-bridging, pairing Q 2 Feldspath Alc. bridging Q 2 CaO plane Pomakhina et al. 212 CCR Q 1 aluminum tetrahedron silicon tetrahedron 11

12 [Ca] Concentration in solution en Ca (mg/l) (mg/l) Comparison of different materials 1 Calcium consumption KAOLIN MICA Kaol 2 C Mica 2 C Bent-Ca 2 C Bent-Na 2 C Ca-BENTONITE Na-BENTONITE Jours Curing time (days) Microstructure of materials 12

13 And the kaolinite reactivity? Delay of the pozzolanic reaction? What is the cause for the immediate gain in mechanical properties of lime treated clayey soils? K Unconfined Compressive Strength (kpa) Montmorillonite 1% CaO Kaolinite 1%CaO Time (days) -6 Bentonite Long term Short term % -7 C-S-H -8 M -9 (ppm) 29 Si NMR Q Chemeda et al. sub ACS 13

14 Quartz Experimental approach Examination of the chemical reactions at kaolinite-lime solution interface [Ca] = 22 mmol ph = Theta-scale KGa-1b SPwt Pwt KGa-2 B24 Low defect High defect Na - Kaolinite Part I Interfacial chemistry Gas adsorption Part II Surface charge and Particle interaction AFM Chemeda et al. sub ACS 14

15 AFM Surface force measurement on silica and alumina face Experimental protocol Gupta and Miller JCIS 344, 21 ph = 5 1 mg/l Tetrahedral Imaging in fluid + + Octahedral + + NaOH Silica glass Silica face Force curve measurement, 2.2, 5.5, 22 mmol/l Silica glass Fused Alumina Ca(OH) 2 15

16 Force (nn) Force (nn) Force (nn) Force (nn) Force (nn) Force (nn) Force (nn) Force (nn) Surface force in Ca(OH) 2 solution mmol/l ph = 6.8? Repulsion force? mmol/l ph = nn 29 nm Silica face Alumina face.6 nn 28 nm Separation 2.2 mmol/l (nm).94 nn 3 nm ph = 11.2 DLVO model = VDW and electrostatic double layer forces Ca(OH) 2 Ca OH mmol/l Separation (nm).34 nn 29 nm ph = mmol/l Separation (nm) ph = mmol/l Separation (nm) ph = nn.4 nn 19 nm 2 nm 22 mmol/l Separation (nm) ph = mmol/l Separation (nm) ph = nn 8 nm.2 nn 5 nm Separation (nm) How does it control particle interactions? 16 Separation (nm) 16

17 Force (nn) Force (nn) Mode of particles organisation in Ca(OH) 2 solution Force (nn) Force (nn) ph < 7 Cantilever Cantilever O T _ ph < 7 Kga-1b Si E + Si Silica face Si Si-Al face Al Alumina face Silica face silica face.7 nn 5.5 mmol/l Al Silica face Alumina face.4 nn 5.5 mmol/l 19 nm R F R F 2 nm Si Separation (nm) Separation (nm) 22 mmol/l Al 22 mmol/l.29 nn 8 nm R F Si R F.2 nn 5 nm Separation (nm) Si Si face Si Al face Separation (nm) 17

18 Suspension height, h (cm) Z potential (mv) Average size (nm) Mode of particles organisation in Ca(OH) 2 solution -1 ph K_pH=4.6 K_KOH_pH= E-F -5-6 Kaolin time (min) Kaolin KOH_pH= t (min) Vitale et al. 216 ACS 18

19 Suspension height, h (cm) Z potential (mv) Average size (nm) Mode of particles organisation in Ca(OH) 2 solution -1 ph Acidic environment K_pH=4.6 K_KOH_pH=12.4 K_Ca(OH)2_pH= Kaolin K_Ca(OH)2 4 Alkaline environment time (min) E-F Kaolin KOH_pH=12.4 CaO_pH= t (min) Vitale et al. 216 ACS 19

20 UCS (Mpa) UCS (Mpa) Résistance à la compression simple (kpa) Concentration en Ca (mg/l) And mechanical behaviour? Kaol 2 C Mica 2 C Bent-Ca 2 C Bent-Na 2 C Jours Ca-BENTONITE KAOLIN MICA Temps (Jours) Curing time (days) 2

21 And the pozzolanic reaction? Bentonite Kaolin Mica C-(A)-S-H C-A-H Gel C-(A)-S-H C-S-H Link between cementitious phase and mechanical behaviour?

22 UCS (Mpa) UCS (Mpa) Résistance à la la compression simple (kpa) 4 And natural soils? Mineralogical phases and association Silt HERICOURT Ca-BENTONITE Ca-BENTONITE KAOLIN KAOLIN MICA MICA Temps (Jours) Curing time (days) Quartz 55% Kaol 12%-Ms 1%-Sm4% Particles et Microstructure? Quartz 3%+ Feld. 11% Ms 46%-Kaol 19% VIGNEUX Silt 22

23 UCS (Mpa) Rc (MPa) Reactivity vs. Microstructure 6, Treatment 1% Lime + 5% Ciment Pozzolanic reaction and cement hydration 2 C 5 C 5, 4, 3, 2, 1,, 7 days 1 day 9 days raw 3 days 3 days 28 days 7 days 9 days 3 days Curing temps time de cure (days) Lemaire et al EG 23

24 UCS (Mpa) Rc (MPa) Reactivity vs. Microstructure 6, 5, 4, 3, Treatment 1% Lime + 5% Ciment Pozzolanic reaction and cement hydration 2 C 5 C 9 days 3 days 2, 1,, Ms 46%-Kaol 19%? 3 days 28 days 28 days 7 days Raw temps Curingde time cure (days) Lemaire et al EG 24

25 Gel C-(A)-S-H µ-xrf SEM qtz qtz inter-agglomerates link qtz inter-agglomerates macroporosity MIP intra-agglomerates microporosity 25

26 Gel C-(A)-S-H + Lime + Cement Clays Quartz or Feldspar Gel of C-A-S-H 26

27 µ-xrf SEM 1 µm + Lime + Cement Morphology/Mineralogy Effects of binders 27

28 PPermeability (m/s) calcium leached (%) And what about durability? 1% 8% Vigneux = dissolution of C-S-H 6% 4% 2% Héricourt = C-S-H stable % ,E-6 1,E-7 1,E-8 1,E-9 1,E Leaching time (days) 28

29 UCS (Mpa) And what about durability? Leaching time (days) 29

30 Summary UNDERSTANDING Pertinent multi-scale and multi-techniques approach: global and local analysis (XRD, TGA, NMR, Microscopies, mechanical behaviour) Good description of ph-ch evolution Reactivity is not always linked with an evolution of mechanical performances Durability = microstructure and leaching of C-S-H APPLICATION Field analysis to assess the durability (carbonation?) Extend to new soils : pyroclastic soils,

31 Thank you for your attention Contact : Dimitri Deneele Researcher Dimitri.Deneele@cnrs-imn.fr