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CEMENT AND CONCRETE MATERIALS materials fundamentals + mix design Christopher Hall 2009 S131 [email protected] CEMENT Materials fundamentals •Sources of information •Cement manufacture + composition •Cement hydration •Microstructure •Concrete mixes •Properties: strength permeability durability Information/texts •Jackson & Dhir: Civil Engineering Materials, 5th edn, 1997 •Mindess, Young & Darwin: Concrete, 2002 •Neville & Brooks: Concrete Technology, 1987 •Neville: Properties of Concrete, 4th edn, 1995 •Bensted & Barnes: Structure and Performance of Cements, 2nd edn, 2001 Information/journals •Cement and Concrete Research •Magazine of Concrete Research •American Concrete Institute Journal ACI Journal •Materials and Structures [RILEM] Information/websites Virtual Cement & Concrete Testing Laboratory includes Electronic monograph from Bentz at NIST: http://ciks.cbt.nist.gov/vcctl/ See also microstructure images library from Lange at UIUC: https://netfiles.uiuc.edu/dlange/www/CML Cement Manufacture Raw materials limestone + clay on firing, produces a complex mixture of synthetic minerals, principally calcium silicates and calcium aluminates Manufacture CEMENT World production 2001 1.6 billion tons CEMENT World production 2001 1.6 billion tons Steel production 900 million tons CEMENT World production 2001 1.6 billion tonnes 2--5 % total CO2 emission Energy intensive manufacture Various figures are quoted. The energy cost of manufacture is around 3500 kJ/kg cement CEMENT World production 2001 1.6 billion tonnes EU production 2002 194 million tonnes For each tonne cement produced 0.800 tonne CO2 is also produced 0.525 tonne from decalcination of limestone 0.335 tonne from combustion of fuel in the kiln 0.050 tonne from electricity production CEMENT In EU, cement industry produces 3 per cent of total anthropogenic CO2 Source: Cembureau CEMENT COMPOSITIONS SiO2 OPC zone CaO Al2O3 Fe2O3 CEMENT COMPOSITION Notation CaO Al2O3 Fe2O3 SiO2 CEMENT COMPOSITION Notation CaO Al2O3 Fe2O3 SiO2 C A F S CEMENT COMPOSITION Notation CaO Al2O3 Fe2O3 SiO2 C A F S Table 2–2. Mineralogical Composition of Classic Cement Clinker Oxide Composition Cement Notatiion Common Name Concentration (wt%) 3CaO • SiO2 C 3S alite 55–65 2CaO • SiO2 C 2S belite 15–25 3CaO • Al2O 3 C 3A aluminate 8–14 4CaO • Al2O3 • Fe2O3 C4AF brownmillerite 8–12 Clinker microstructure 150 micron C3S C2S C3A C4AF C3S C2S Clinker microstructure 150 micron C3S C2S C3A C4AF C3S C2S Clinker microstructure 150 micron C3S C2S C3A C4AF C3S C2S Clinker microstructure C3S C2S C2A C4AF C3 A C4AF C3A C4AF Clinker microstructure C3S, C2S, C3A, C4AF 200 micron Cement grinding Gypsum additions (strictly sulphate) Particle size distribution Images from Lange UIUC http://cee.ce.uiuc.edu/lange/micro Cement hydration 1 Heat evolution Induction period Cement hydration 2 Chemical reaction with water All minerals involved 115 micron Cement hydration 2 Principal reaction which develops strength C3S + water ---> C-S-H Cement hydration 3 Chemical reaction with water All minerals involved Formation of lime (calcium hydroxide) pH of pore water Cement hydration 4 Water requirement about 30% by wt cement for complete reaction Cement hydration 5 Four stages of hydration in a microstructural model of C3S hydration. The degrees of hydration are: top left--0% top right--20%, bottom left--50% bottom right--87% Red=unreacted cement blue=CH yellow=C-S-H black= porosity from Bentz, NIST Computational materials science Cellular automaton model of cement and concrete D Bentz and E Garboczi NIST Cement hydration 6 Synchrotron X-ray view Summary of setting and hardening Workability Development of continuous network of hydrate material Strength development Porosity and permeability Timescale Strength and strength development Cement Based Materials Mortars Concrete Manufactured cement based materials Autoclaved aerated concrete Transport properties Permeability Sorptivity see Hall & Hoff: Water Transport in Brick, Stone and Concrete 2002 PERMEABILITY property Darcy’s law: u = Q/A = - kp /L k permeability Q volume rate of flow B A Types of cements Portland cement Blended or composite cements Portland + other mineral components BS EN 197-1 Cement Other mineral components are Minerals which react with lime Pozzolans Blastfurnace slag Fly ash Natural pozzolans Inert fillers Crushed limestone BS EN 197-1 Cement