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CIVL 3137 2
ACI Definition
portland cement (n.) a cementitious productmade by heating raw materials containing oxides ofaluminum, silicon, and calcium to temperaturesapproaching 1500°C, then pulverizing the end productwith a small amount of gypsum.
CIVL 3137 4
Primary Ingredients
lime (CaO) ‒ 61‐67%limestone, marble, chalk, marl, calcite, seashells, blast furnace slag
silica (SiO2) ‒ 19‐23%clay, loess, shale, sand, sandstone, quartzite, fly ash, rice‐hull ash
alumina (Al2O3) ‒ 2‐6%clay, loess, shale, bauxite, fly ash
iron oxide (Fe2O3) ‒ 0‐6%clay, shale, iron ore, pyrite, blast furnace flue dust
Inside a Cement Kiln
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drying
Total time in kiln = 60‐90 minutes
400ºC1500ºC 800ºC
cooling
clinker
Inside a Cement Kiln
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3 2825
heatC
CaCO CaO CO
calcining
400ºC1500ºC 800ºC
cooling
clinker 1 ton of cement 1 ton of CO2
Inside a Cement Kiln
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sintering
C2Sforms
400ºC800ºC1500ºC
2 2 41200
2 heatC
CaO SiO Ca SiO
cooling
clinker
Inside a Cement Kiln
CIVL 3137 8
sintering
C3Sforms
400ºC800ºC1500ºC
2 4 3 51250
heatC
CaO Ca SiO Ca SiO
cooling
clinker
Inside a Cement Kiln
CIVL 3137 9
sintering
C3Aforms
400ºC800ºC1500ºC
2 3 3 2 613003 Ca Al Oheat
CCaO Al O
cooling
clinker
Inside a Cement Kiln
CIVL 3137 10
C4AFforms
400ºC800ºC1500ºC
3 2 6 2 3 4 2 2 10CaO Ca Al O Fe O Ca Al Fe O
cooling
clinker
CIVL 3137 12
Cement Phases
Dicalcium silicateC2S (2CaO∙SiO2)
Tricalcium silicateC3S (3CaO∙SiO2)
Tricalcium aluminateC3A (3CaO∙Al2O3)
Tetracalcium aluminoferriteC4AF (4CaO∙Al2O3∙Fe2O3)
Cement Phases
TricalciumSilicate
50%
DicalciumSilicate
25%
Tricalcium Aluminate
12%
Tetracalcium Aluminoferrite
8%
Gypsum4%
Other1%
CIVL 3137 14
Typical Percentages by Weight(Mindess and Young, 1981)
Cement Composition
Characteristic C3S C2S C3A C4AFRate of hydration Med Slow Fast SlowHeat of hydration Med Low High LowEarly strength High Low Med LowUltimate strength High High Low LowSulfate resistance Good Good Poor Good
CIVL 3137 15
Responsiblefor
Short‐termHardening
Responsiblefor
Long‐termHardening
Responsiblefor
InitialSetting
Setting = transformation of cement paste from fluid to gel to solid
Hardening = gain in strength after concrete gel has become a solid
CIVL 3137 17
Hydration Chemistry
2 4 2 2 2 22 4 3 2 3Ca SiO H O CaO SiO H O Ca OH
dicalciumsilicate
water
calcium silicate hydrate
calciumhydroxidecrystals
CIVL 3137 18
Hydration Chemistry
3 4 2 2 2 22 6 3 2 3 3Ca SiO H O CaO SiO H O Ca OH
tricalciumsilicate
water
calcium silicate hydrate
calciumhydroxidecrystals
CIVL 3137 19
Hydration Chemistry
CS H CSH CH
calciumsilicate
water
calcium silicate hydrate
calciumhydroxidecrystals
Cement Composition
Type Name C3S C2S C3A C4AFI Normal 50 24 11 8II Modified 42 33 5 13III High early 60 13 9 8IV Low heat 26 50 5 12V Sulfate-resistant 40 40 3.5 9
CIVL 3137 21
Table 7-3
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Setting Time Factors
amount of C3Aamount of CaSO4cement fineness
amount of mixing wateramount of sun/wind
ambient temperature } placing conditions
} cement type
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Hardening Factors
amount of C3S
amount of C2S
ambient temperature
ambient humidity } curing conditions
} cement type
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Effects of Water Loss
Relative effects of water lossduring the first three days on28-day compressive strength
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Effects of Water Loss
Stored in laboratory air after 3 days
Stored in laboratory air after 7 days
Stored continuously in laboratory air
Figure 7‐2