cement and concrete materials materials fundamentals + mix design christopher hall 2009 s131...
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CEMENTMaterials 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 JournalACI Journal
•Materials and Structures [RILEM]
Information/websites
Virtual Cement & Concrete Testing Laboratoryincludes 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 tonsSteel 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
CEMENTWorld production 2001 1.6 billion tonnesEU production 2002 194 million tonnes
For each tonne cement produced0.800 tonne CO2 is also produced
0.525 tonne from decalcinationof limestone
0.335 tonne from combustionof fuel in the kiln
0.050 tonne from electricityproduction
CEMENT
In EU, cement industry produces3 per cent of total anthropogenic CO2
Source: Cembureau
CEMENT COMPOSITIONS
CaO
SiO2
Al2O3 Fe2O3
OPC zone
CEMENT COMPOSITION
Notation
CaO Al2O3
Fe2O3
SiO2
CEMENT COMPOSITION
Notation
CaO CAl2O3 AFe2O3 FSiO2 S
Table 2–2. Mineralogical Composition of Classic Cement Clinker
Oxide Composition Cement Notatiion Common Name Concentration (wt%)
3CaO • SiO2 C3S alite 55–65
2CaO • SiO2 C2S belite 15–25
3CaO • Al2O3 C3A aluminate 8–14
4CaO • Al2O3 • Fe2O3 C4AF brownmillerite 8–12
CEMENT COMPOSITION
Notation
CaO CAl2O3 AFe2O3 FSiO2 S
Clinker microstructure
C3SC2SC3AC4AF
150 micron
C3S
C2S
Clinker microstructure
C3SC2SC3AC4AF
150 micron
C3S
C2S
Clinker microstructure
C3SC2SC3AC4AF
150 micron
C3S
C2S
Clinker microstructure
C3SC2SC2AC4AF
C3AC4AF
C3AC4AF
Clinker microstructure
C3S, C2S, C3A, C4AF200 micron
Cement grinding
Gypsum additions (strictly sulphate)Particle size distribution
Images from LangeUIUChttp://cee.ce.uiuc.edu/lange/micro
Cement hydration 1
Heat evolutionInduction period
Cement hydration 2
Chemical reaction with waterAll minerals involved
115 micron
Cement hydration 2
Principal reaction which develops strength
C3S + water ---> C-S-H
Cement hydration 3
Chemical reaction with waterAll 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-Hblack= porosity
from Bentz, NIST
Computational materials scienceCellular 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
MortarsConcrete
Manufactured cement based materialsAutoclaved 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
A
B
Types of cements
Portland cement
Blended or composite cementsPortland + other mineral
components
BS EN 197-1Cement
Other mineral components are
Minerals which react with limePozzolansBlastfurnace slagFly ashNatural pozzolans
Inert fillersCrushed limestone
BS EN 197-1Cement