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A hydraulic cement capable of setting, hardening and

remaining stable under water. It consists essentially ofhydraulic calcium silicates, usually containing calcium

sulfate.

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Raw Materials:2/3 calcareous materials (lime bearing) - limestone

1/3 ar illaceous materials (silica alumina iron)- cla

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Raw Material

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Crushing

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Blending

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Old Method

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Kilniln

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Grinding

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Production ProcessOooops, Problem

Production of cement

CO2 production in theworld

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Cement grains

Courtesy from Prof. Karen Scrivener, EPFL

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Early Hydration

3 hours 10 hours

our esy: ro . aren cr vener

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Hydration Products

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n er

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a

S SiO2A Al2O3

F Fe3O4

H H2O

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C3S : 3CaOSiO2

:C3A : 3CaOAl2O3

C4AF : 4CaOAl2O3Fe3O4

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See video 1

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+ -- + +2C2S + 4H --> C3S2H3 + CH + 62 cal / gC3A + CSH2 --> Ettringite + 300 cal / g

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See video 2

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Hydration Products

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y ra e as e

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-Calcium Silicate Hydrate

Notation: C-S-HC S Ratio: 1.5 to 2.0Main Characteristics: High Surface (100 to 700 m2/ g) ---->

g an er a s orce ----- reng .

Volume % : 50 a 60

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- -

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- a c um y rox e port an te

Volume % : 20 to 25low Van der Walls force

problems with durability and strength

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Calcium Hydroxide

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-Calcium Sulfoaluminate Hydrates

first : ettringite

after : monosulfate hydrated.

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Ettringite

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Review

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Review 2

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Review 3

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Type I- General Purpose

Type II- moderate heat of hydration and sulfate resistance8%) : general construction, sea water, mass concrete

ype - g ear y strengt : emergency reprecast, winter construction.

ype - ow ea , , :

concrete

ype - su a e res s an su a e n so , s

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Advanced Light Source at Berkeley

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Imaging at High Spatial Resolution:Soft X-Ray Microscopy to 15 nm

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Two Common Soft X-Ray Microscopes

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Early hydrates forming during the pre-

(Sheaf ofwheat)

Cement

rain

C3S hydrated for 34min. in saturated limeand calcium sulfate atw/c=5, 1s exposuretime, 516eV, scale bar

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(Sheaf ofwheat)

Cement

rain

C3S hydrated for 56min. in saturated limeand calcium sulfate atw/c=5, 1s exposuretime, 516eV, scale bar

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In-situ Massive precipitation

8h 30min.

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In-situ Massive precipitation

8h 36min.

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9h 16min.

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Spot

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Summary

Sheaf of wheat hydrates are forming on thecement rains durin the first minutes

precipitation of C-S-H (needles)

The early hydrate layer covering the cement grains

trans orms ur ng t e acce erat on per o

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Admixtures: Accelerators (CaCl2)

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Summary

CaCl2 increases the rate of formation of- - .

This C-S-H is less dense than in a control

sam le.

e acce erat ve power o a may come

from its ability to flocculate hydrophilic

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Retarders: Sucrose

31 minutes 68 minutes 100 minutes

Sucrose has delayed the early formation of C-S-H. ,

Once the retardation is over, hydration proceeds very rapidly

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Condition

Lets study a cement paste with w/c= 0.63Start with 100 cm3 of cement.

Compute the mass of cement: Mc = 3.14* 100 = 314 g

Compute the mass of water: Mw = 0.63 * 314 = 200 g

Vw= 200 cm3

Vc= 100 cm3

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Hydration Process

Miracle of hydration: Vp = 2 Vc

50%Vw= 200 cm3 Vw= 150 cm3

Vc= 100 cm3 Vc=50 cm3

Vp = 100 cm3

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Once More

75%Vw= 200 cm3 Vw= 125 cm3

Vc= 100 cm3 Vc=25 cm3

Vp = 150 cm3

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Finally

100%Vw= 200 cm3Vw= 100 cm3

Vc= 100 cm3

Vp = 200 cm3

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Exam question

Calculate the water/cement ratio needed to

cement paste.

*

100%100 cm3

.

W/c= 0.32

100 cm3

cm

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o s n e y ra e emeno s n e y ra e emen- n er ayer space n

* size = 5 to 25

* some effect on drying shrinkage and creep

-> 50 nm : detrimental to strength and impermeability< 5 nm: im ortant to dr in hrinka e and cree

-Air Voids~

* entrained air: 50 to 200 mm

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Water inside the pores

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Orders of magnitude

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Orders of Magnitude

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More Advanced Material