Feasibility of Calcined Marl as an Alternative Pozzolanic Material

Transcription

1 1st International Conference Calcined Clays for Sustainable Concrete, June 23rd - 25th Feasibility of Calcined Marl as an Alternative Pozzolanic Material Tobias Danner 1 Harald Justnes 1,2 Geir Norden 3 Tone Østnor 2 Lausanne,

2 Feasibility of Calcined Marl Introduction: Percent of global GHG emissions Power (coal) Power (gas) Power (oil) Power (other) Cement Refining Iron & Steel Petrochemical Other orldknow ledge.com 5-7 % of global CO 2 -emissions today derive from cement industry most effective way to reduce these emissions is the use of supplementary cementitious materials the right choice of the material is mainly a uestion of availabilty. Marl is clay with high amounts of CaCO 3, rendering it unsuitable for the clay industry. But can it be made reactive? 2

3 Feasibility of Calcined Marl Approx. mineralogical compostion of the marl in %: Smectite Kaolinite Illite Calcium Carbonate Quartz Marl Chemical compostion of the marl in %: SiO 2 Al 2 O 3 Fe 2 O 3 CaO MgO Na 2 O K 2 O MnO P 2 O 5 TiO 2 Marl Calcination of the marl: IBU-Tec Germany à small rotary kiln (7m), 45 min retention time, C (50 C steps) Milling of the marl: UVR-FIA GmbH Germany, discontinousdrum mill to d µm 3

4 Feasibility of Calcined Marl 28 days compressive of mortars: Standard procedure NS-EN % replacement of OPC by calcined marl: compressive strength [MPa] % SØ-800: 12% higher strength than reference mortar with 20 % metakaolin* only 3% strength increase calcining temperature * Comercial Metakaolin (Metaver N) from Newchem 4

5 Phase transformations during calcination between ºC A A A A W D CaCO SiO 2 W A 850/1000 Kaolinite: AS 2 H 2 Calcite - Cc Smectite/Illite 800/950 amorphous phase 750/ /850 Gehlenite - C 2 AS at 850 ºC Anorthite CAS 2 650/800 Wollastonite - CS 600/750 Diopside CMS 550/ θ 5

6 Feasibility of Calcined Marl FT-IR: Al-O-Si deformation Si-O stretching OH-stretching region Si-O-Si deformation complete dehydroxylation of clay Al-Al-OH deformation band disappears àcomplete dehydroxylation of octahedral layer Decomposition of calcite not complete: ~ 5% left (TG/DTG) raw 650 C 800 C CO32- stretching/ bending modes Significant structural changes in the clay mineral structure Decreasing content of octahedral cations: Al-NMR: Al(VI) à Al(IV) wavenumber [cm-1] 6

7 Mössbauer Spectroscopy: Søvind Marl: 4 Fe 2+ + O 2 à 4 Fe O 2- Oxidation of iron: Sample Fe 2+ [%] Fe 3+ [%] raw-clay calcined clay 7 93 Feasibility of Calcined Marl [1] Sample Isomer shift Fe 2+ Fe 3+ Quadrupole splitting Isomer shift Quadrupole splitting raw clay Calcined clay Main coordination change: Fe 2+ (VI) à Fe 2+ (IV) Fe 3+ (VI) à Fe 3+ (V) + changes in the ligand structure Bothiron species originally in octahedral coordination à substitution for Al 3+ and Mg 2+ in octahedral layer of clay minerals 7 [1] Schroeder, P.A., American Mineralogist 75, (1990).

8 Feasibility of Calcined Marl EPMA: Calcined marl: Coccoliths in Søvind Marl: 800 C: [1] X Weight %_X: Al2O3 [1] Young & Henriksen (2003), Rev. Min. & Geoch. 54, SiO Fe2O CaO 10.3 K2O 1.8 Na2O 1.0 MgO 2.4

9 Pozzolanic activity Calcium hydroxide consumption by thermal analysis: Feasability of Calcined Marl Paste with marl/lime ratio of 1/1 mixed with alkaline solution (0,158 M, KOH/NaOH = 2/1, ph = 13.2) Marl/Lime = 1/1 20 C 38 C Curing for 28 days and 6 month at 20 and 38 C TGA/DTG was used to calculate the calcium hydroxide content Reduction in calcium hydroxide decomposition peak in range C relative to reference was taken as pozzolanic activity CH at 0 days [%] CH at 28 days [%] Consumed CH [%] 0-28 days Consumed lime [g] per gram clay CH at 6 month [%] Consumed CH [%] 0-6 month Consumed lime [g] per gram clay After 28 days comparable to the lime consumption ofmetakaolin 9

10 Feasibility of Calcined Marl relative intensity XRD: Søvind Marl/lime 1/1 cured at 20 ºC: Fe-substituted carbo-aluminate hydrate Smectite Quartz Calcite Lime = calcium hydroxide monocarbo-aluminate hydrate hemicarbo-aluminate hydrate Theta Scale 6 m 28 d 0 d 130 TG/DTG: C-S-H Signsof Katoite Al-MAS-NMR: Al(IV) à Al(VI) Al (V) incorporation in C-S-H phases Al substitution for Ca in C-S-H 10

11 Feasibility of Calcined Marl SEM (Polished cross section of samples embedded in epoxy resin) 38 C 20 C 2 1 C-S-H 4 C-S-H Illite Clay glass Calcite 3 AFm Clay WDX_1: Ca: 26.1, Si: 10.8, Al: 4.5 2: Ca: 29.1, Si: 5.2, Al: 1.4 3: Ca: 21.8, Si: 4.6, Al: 11.1, Fe: 4.4 4: Ca: 15.2, Si: 8.9, Al: 6.3, Fe:

12 Feasibility of Calcined Marl Industrial Scale Production Test: Compressive strength of mortars with 20, 35, 50, 65 % (volume) replacement of OPC by calcined marl Amount of Superplasticizer in % of total dry material 20 % repl % repl % repl % repl

13 Feasibility of Calcined Marl Conclusions: Calcined Marl can be made an efficient pozzolanicmaterial by calcination and be considered as industrial pozzolan within the standard EN % replacement of Portland cement by marl calcined at optimum temperature gave the same 28 days strength as reference with 100% cement. à it may be feasible to make portland pozzolan cements (CEM VI/B) Significant structural changes in the clay minerals (XRD, FT-IR, 27 Al-NMR) Mössbauer spectroscopy is applicable to document structural changes increasing the clay reactivity Formation of Ca-enriched reactive glass phase from reaction of clay minerals and decomposing coccoliths Due to some remaining calcite upon calcination carboaluminate hydrates were the main hydration products formed in marl/lime pastes besides C-S-H and C-A-(S)-H. 13

14 1st International Conference Calcined Clays for Sustainable Concrete, June 23rd - 25th Thank you for your attention Acknowledgements: Financial support by Saint-GobainWeber and help with mortar tests by the COIN-group ( is gratefully acknowledged 14