PRESENTATION Q_CEM-presentation Cambridge.pptx

Quartenary Cement with fast set - and low carbon footprint-accelerated set without impact on durability in time - compensation of shrinkage

1. Quality Over Quantity 1

2. Quaternary Cement

3. case study ACA ;Amorphous Calcium Aluminate, a glass type aluminium silicate predominantly forming C 12 A 7 case study FCA , ; Amorphous Aluminium Trihydroxide a flash Calcined Alumina, Al (OH) 3 Two parallel studies were done investigating the effect of partial replacement of Portlandcement and hybride thereof Main objectives ; the effect on set and early strength impact on shrinkage Both proofed , in combination with sufficient Calcium Sulphate , being excellent precursors in forming ettringite at early stage of hydration

4. Aluminium trihydrate (ATH) is derived from bauxite mainly by the BAYER process Bauxite is digested in caustic soda and aluminium hydroxide is precipitated Aluminium hydroxide is than calcined to obtain aluminium oxide , or pure alumina Re-calcination through flash calcination The fine white powder is ground to a high surface area and classified to a defined PSD Production

5. Solutions in the presence of lime , alumina and calcium sulfate complex hydrates are formed ; AFt (ettringite) 3CaO . Al2O3 . 2CaSO4 . 32H2O AFm (mono sulfo aluminate) 3CaO . Al2O3 . CaSO4 . 12H2O 4CaO . Al2O3 . 19H2O

6. ettringitic system Cs Ca Al sulfate calcium alumina

7. chemical reaction on hydration by fast release of alumina ions reacting quickly with available calcium and sulphate ions forming a high amount of ettringite crystals (AFt also KLEIN’s compound) a tri-sulpho-aluminate salt; 3CaO•Al2O3•3CaSO4•32H2O precipitation of ettringite

8. Cš hemi-hydrate gypsum anhydrite Al calciumaluminate cement cacium sulfo aluminate amorphous calcium aluminate flash calcined alumina Ca calcium oxide calcium hydroxide (hydraulic) Portlandcement 3CaO•Al2O3•3CaSO4•32H2O ettringite

9. A higher aluminium concentration in a cement matrix on its own does not guarantee a faster set but depends largely on the amount of available sulfate It is shown that alumina gel is formed preventing silicates going into solution resulting in and retardation of set and lower strength development Higher sulfate concentrations further accelerate hydration It is finding the balance of all constituents

10. ettringite are needle,ladth or rod like crystals (morphology can vary) formed at early stages of hydration ettrinigite are fine needles, hexagonal shaped crystals on average 1 ~ 7 μ in size increase in volume on hydration binds excess water (32 water molecules) improve the density by filling the pore structure ETTRINGITE

11. experimental 2 types of flash calcined amorphous alumina were tested ; FCA-6 top size 6 micron AFX-6 top size 6 micron + 50% by weight anhydrous calcium sulfate FCA-10 top size 10 micron AFX-10 top size 10 micron + 50% by weight anhydrous calcium sulfate In all instances 3,5 and 7% by weight was mixed with a CEM I 52,5R White Portlandcement Prisms were made according EN-196-1 - 16x4x4 cm Initial tests were done at 24 hours and 7 days t

12. Phase Chemical alumina Al203 SiO2 Fe2O3 Na2O L.O.I. m2/g BET D50 Top size FCA ALPHA ≥ ≤ ≤ ≤ ≤ ≥ Micron Micron I 99,5 0,05 0,02 0,4 10 280 5-10 6 I 99,5 0,05 0,02 0,4 10 280 5-10 9 analysis FCA

13. Chemical Al 2 3 SiO 2 CaO SO 3 Fe 2 O 3 Alkali C 3 S C 3 A Blaine % % % % % % % % cm 2 /g 5,63 23,34 67,5 2,59 0,57 0,27 48,57 12,67 4100 analysis CEM I 52,5R Chemical CaSO 4 SiO 2 f CaO Blaine % % % cm 2 /g 98,8 0,1 0,3 6000 analysis Anhydrous Calcium Sulfate

14. 24 hours strength 7 days strength flexural compressive flexural compressive OPC control 3,44 15,59 5,71 35,5 3,5% FCA-6 2,96 14,75 6,19 30,28 3,5% AFX-6 4,71 23,22 7,05 40,92 3,5% FCA-10 2,73 13,69 6,36 28,6 3,5% AFX-10 3,63 20,85 6,39 32,28 7 % FCA-10 3,6 13,17 6,61 33,93 7 % AFX-10 4,62 18,29 6,96 40,83 7 % FCA-10 3,3 15,6 5,91 28,6 7 % AFX-10 3,45 18,29 6,23 33,47 mix design

15. XRD analysis ettringite 3,5% FCA-6 9,1 % 3,5% AFX-6 22,6 % 7 % FCA-10 12,6 % 7 % AFX-10 18,2 %

16. From the types of FCA tested on white Portlandcement type AFX-6 at 3,5% by weight preformed the best in terms of flexural strength On compressive strength again type AFX-6 performed best at an addition rate of 7 % XRD-testing confirms that it is in line with the amount of ettringite being formed we noticed a shortening of the setting time in all cases except when aluminum is overdosed aluminium silicate hydrogel prevents cement hydration

17. In conclusion Both FCA and ACA are excellent precursors in forming ettringite crystals at an early stage of hydration; even at a limit addition rate the effect is noticeable alumina goes in solution quickly reacting with sulfate from cement in case of insufficient sulfate , alumina gel retards the hydration an equilibrium can be found by increasing sulfate addition higher amount of ettringite accounts for higher initial strength , volume expansion and accelerated drying Given the current market whereby access to CEM I cement is becoming more difficult and focus is on reduction of carbon footprint FCA and ACA can play an important role in improving the early age characteristics of cement and hybrid cements the use of mineral accelerators shorten the curing time i.e. saving energy further studies are done to investigate the effect on other hydraulic binder systems

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