Cement mineralogy and hydration of cement minerals

Cement Mineralogy

1. CaO => limestone SiO 2 ,Al 2 O 3 ==> clays, shale FeOx

2. Cement mineralogy - Alite – C 3 S Orthosilicate – monoclinic (M1 or M3) Biaxial Negative with 2V ~ 20-60° Low birefringence 0.002-0.010 ~ first order gray int. Color colourless with // polars – high positive relief 3 triclinic - 3 monoclinic and 1 rhombohedral polymorphs exist First cristal structure determination by Jeffery (1952)

3. Alite - Mineral formula: Ca3SiO5 - Chemical formula: 3CaO.SiO2 (C3S)

4. Cement mineralogy - Belite Five polymorps exist at ordinary pressures the b – C 2 S polymorph is most common. - Monoclinic - Space group P2 1 /n Biaxial Negative with 2V ~ 64-69° second order interference colors colourless – (amber) yellow with // polars – high positive relief First cristal structure determination by Midgley (1952) Larnite Ca 2 SiO 3 is the natural analogue of belite

5. - Mineral formula: Ca 2 SiO 4 - Chemical fomula: 2CaO.SiO 2 (C 2 S) Belite

6. Belite- crossed polars

7. Belite – striations - twinning

8. Cement mineralogy - Aluminate Phase - Cubic - Typically fills interstices between crystals of belite and ferrite. light-brown color Cement mineralogy - ferrite phase - Orthorombic – biaxial negative - Composition ranges from C 5 A 2 F to C 6 AF 2 - Typically fills interstices between crystals of belite and ferrite. light-brown – yellow color brownmillerite is a rare natural analogue.

9. , , , , Summary of clinker component information. Clinker component Crystal modifications Modifications in clinker Tricalcium silicate Ca 3 SiO 5 T 1 , T 2 , T 3 , M 1 , M 2 , M 3 , R (polymorphs) M 3 , M 1 , T 2 , R Dicalcium silicate Ca 2 SiO 4 5 polymorphs Tricalcium aluminate Ca 3 Al 2 O 6 C I , C II , O, M (ion stabilised) C I , C II , O Tetracalcium aluminoferrite Ca 2 (Al 2 O 3 ) x (Fe 2 O 3 ) 1– x Orthorhombic (Fe/Al range) Orthorhombic

10. Clinker Slag fly ash limestone European standardisation

11. Glasser - 1998 Prismatic alite crystals (dark) Round light brown belite crystals Reflected light optical microscopy on etched polished clinker sections

12. SEM backscattered electron image (BSE) showing alite (A), belite (B), aluminate (AL), ferrite (F), and porosity (P). Stutzman-2001

13. XRD-powder diffraction pattern (raw data) of a Vicat natural cement Gilles Mertens – 2006

14. Rietveld Refinement results of a Vicat natural cement Gilles Mertens – 2006

15. 1. Introduction - What is concrete ? - What is cement - OPC ? - Some history – natural cements 2. OPC - Cement - resources & clinker production - cement mineralogy - cement hydration - CSH - cement paste – pore structure 3. Cement replacing materials – blended cements - Why ? - Natural pozzolana - Artificial pozzolana

16. Hydration of cement minerals C 2 S + 2H  CSH + CH Ca(OH) 2 ; Portlandite Calcium Silicate Hydrate Belite + water