1. The document discusses the hydration process of cement, which involves a series of irreversible chemical reactions between cement and water. This leads to the formation of hydration products over time, causing the cement paste to stiffen, set, and harden. 2. There are five stages of cement hydration: mixing/dissolution, dormant period, acceleration, deceleration, and densification. The hydration reactions produce compounds like calcium silicate hydrate (C-S-H) and calcium hydroxide (CH) that provide strength to the concrete. 3. Factors that affect the hydration process include the chemical composition of cement, cement type, sulfate content, fineness,

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2. HYDRATION OF CEMENT
Presented To:
Dr. M. Irfan Ahmad Khokhar
Presented By:
• M. Rizwan Riaz 2011-MS-CES-01
(rizwansamor@gmail.com)
• Muhammad Safdar 2011-MS-CES-11
• Fatima Mehvish 2011-MS-CES-30
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3. CONTENTS
The discussion is divided into the following sections :
• Introduction
• Hydration Process
• Heat of Hydration
• Factors Affecting Hydration
• Measurement of Cement Hydration
• Approaches to Control Hydration
• References
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4. Hydration
• Series of irreversible exothermic chemical reactions
between cement and water
• Cement-water paste sets and hardens, “gluing” the
aggregate together in a solid mass
Formation of hydration products over time leads to:
• Stiffening (loss of workability)
• Setting (Solidification)
• Hardening (Strength gain)
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5. Why is it Important?
Understanding the basics of hydration is important to
• Ensure the strength and durability of concrete
• Recognize and mitigate the stresses to prevent
cracking
• Appreciate the importance of good curing and
construction practices
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6. Composition of Cement Clinker
Consists primarily of calcium aluminates and calcium silicates
 Calcium aluminates
– Tricalcium aluminate (C3A)
– Ferrite (C4AF)
 Calcium silicates:
– Alite (C3S)
– Belite (C2S)
 Gypsum is added to avoid
the uncontrolled setting
resulting from C3A reaction
with water.
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7. Cement Components
Alite or 3CaO•SiO2 or C3S
−Hydrates & hardens quickly
−High early strength
−Higher heat of hydration (setting)
Belite or 2CaO• SiO2 or C2S
−Hydrates & hardens slower than Alite
−Gives off less heat
−High late strength (> 7 days)
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8. Cement Components
Aluminate or 3CaO• Al2O3 or C3A
−Very high heat of hydration
−Some contribution to early strength
−Low C3A for sulfate resistance
Ferrite or 4CaO• Al2O3 • Fe2O3 or C4AF
−Little contribution to strength
−Lowers clinkering temperature
−Controls the color of cement
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9. Hydration Process
There are two types of reaction underlying the hydration
process:
• Through-solution hydration
• Solid-state hydration or Topochemical hydration
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10. Hydration Process
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11. Stage 1: Mixing/ Dissolution Stage
(< 15 minutes)
Sulfate reacts with aluminate and water to form C-A-S-H, a precursor to
Ettringite.
The gel limits water’s access to aluminate
Reactions slow. Heat drops
Too little sulfate: flash set
Too much sulfate: false set
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12. Stage 2: Dormant/ Induction Period
(2–4 hours)
During this dormant period, the silicates (alite and belite) slowly
dissolve, releasing calcium ions in solution
During dormancy; before initial
set; the mix can be
transported, placed, finished, an
d textured.
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13. Stage 3: Hardening/ Acceleration Stage
(2–4 hours)
C-S-H, fiber-like particles & CH forms and give concrete its strength
Heat is generated causing thermal expansion
Initial and Final Set occur
The gel-like C-A-S-H transforms
into a needle-like solid
(ettringite) that contributes
somewhat to early strength.
Curing necessary right after
finishing
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14. Stage 4: Cooling/ Deceleration Stage
(several hours)
After final set, the buildup of C-S-H and CH begins to limit access of
water to undisclosed cement
Silicate reactions slow.
Heat peaks and begins to drop
Concrete cools and contracts
Cracking can occur
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15. Stage 5: Densification/ Steady Stage
(can continue for years)
Start of belite reactions and they can continue for years
Belite reactions also produce C-S-H and CH, forming a solid mass
Longer length of this stage gives:
•Greater concrete’s strength
•Lower permeability
•Greater durability
To promote continued
hydration, moisture must be
retained in the slab as long as
possible.
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16. 5 Stages of Hydration
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17. Hydration Reactions
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18. Characteristics of hydration
cement compound
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19. Heat of hydration
• Heat liberated when cement comes in contact with
water as a result of the exothermic chemical reaction
between cement and water.
Significance:
• Can result in thermal cracking which can reduce
concrete durability.
• Significantly influences lift thickness which impacts
economic savings and construction period.
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20. Cement Hydration Mapped on a Heat vs. Time Curve
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21. Effect of member thickness on
temperature of concrete
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22. Mechanism of heat generation
Reaction of calcium silicates:
• 2C3S + 7H → C3S2H8 + 3CH ΔH=-500J/g
• 2C2S + 7H → C3S2H8 + CH ΔH=-250J/g
Reaction of tri-Calcium Aluminate
• C3A + 3CŠH2 + 26H → C6AŠ3H32 ΔH=-1350J/g
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23. Measurement of Heat of
Hydration
Standards:
ASTM C 186
we measure the heat of solution of;
Dry cement. Partially hydrated cement.
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24. Use & Significance
• Cement specification.
• For research purposes at any age.
• Helpful for calculating temperature rise in
mass concrete
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25. Apparatus
• Calorimetric apparatus.
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26. Cont…
26

27. Cont…
27

28. Cont..
• Mixer
• Storage
• Mortar
• Drying oven
• Weighing bottles
• Stop watch
• Sieves
• weights
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29. Cont…
Plastic vials Muffle furnace
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30. Cont…
crucibles Analytical balance
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31. Reagents &Materials
• HF
• HNO3
• WAX
• ZnO
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32. Determination of heat capacity of
apparatus
• Take total weight of the solution to 425g
• Assemble calorimeter
• Start stirring motor (20 mint)
• Allow system to become uniform
• Introduce ZnO
• Read the temperature OF;
solution period
rating period 32

33. Cont..
• Calculate the corrected temperature rise
as follows:
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34. Cont..
• Calculate the heat capacity of the calorimeter and
contents as follows:
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35. Sampling & Test Specimens
• Preparation of Cement Paste
• Preparation of Partially Hydrated
Sample for Heat of Solution Test
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36. Procedure:
• Calorimetric Procedure
Determine the heat of solution of the dry
cement sample.
Determine the heat of partially hydrated
sample.
• Determine loss on Ignition
•
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37. Calculations.
• Heat of Solution of Dry Cement
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38. • Heat of Solution of Partially Hydrated
Sample
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39. • Heat of Hydration
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40. Approaches to control heat of
hydration
• Control of Cement Amount
• Use of low-heat Cement
• Use of Pozzolans
• pre-cooling
• post-cooling
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41. Factors Affecting Hydration
Major factors:
• Chemical Composition of Cement
• Cement Type
• Sulfate Content
• Fineness
• Water/Cement Ratio
• Curing Temperature
• Effects of SCMs and Admixtures
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42. Chemical Composition of Cement
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43. Cement Type
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44. Cement Type
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45. Sulfate Content
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46. Fineness of Cement
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47. Water/Cement Ratio
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48. Curing Temperature
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49. Supplementary Cementitious Materials
How they work
• SCMs convert CH (a somewhat less desirable product of
hydration) into C-S-H (which gives concrete its strength).
How SCMs may affect hydration
• Often slow hydration, extending working time and delaying
set, strength gain.
• Reduce heat peak.
• Extend heat generation. 49

50. Fly Ash Replacement Effect
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51. Water Reducers
How they work
• Disperse cement clusters, freeing trapped water
which can then react (hydrate) with cement.
• How they affect hydration
• More of the mix cement is hydrated, resulting in a
greater volume of hydration products.
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52. Water Reducers
How they work
• Coats cement particles so they dissolve more slowly.
How they affect hydration
• Slow hydration.
• Reduce heat peak and extend hydration and heat
generation (similar to water reducers).
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53. Set Accelerators
How they work
• Reduce time required for super saturation of calcium
ions.
How they affect hydration
• Earlier initial and final sets.
• Increased heat generation; higher maximum peak on
the hydration curve.
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54. References
• Technical summary 4-a, National concrete pavement technology center,
IOWA State University, August 2007.
• Wolfgang B., Concrete an example for complex porosity, Institute of
building materials research (IBAC), RWTH Achen university, Germany.
• Dr. K. Kurtis, Cement and Hydration, School of civil engineering, Georgia
Institute of technology, Atlanta, Georgia.
• Feng Lin, Modelling of hydration kinetics and shrinkage of Portland cement
paste, Coloumbia University, 2006.
• S. G. kim, Effect of heat of hydration on mass concrete placement, IOWA
state university, 2010.
• A.S.M abdul Awal & M. Warid Husain, Effect of palm oil fuel ash in
controlling heat of hydration of concrete, University of technology, Johor
Malaysia.
• P. Juilland et al., Effects of mixing on early hydration of alite and OPC
system, Cement and Concrete Research, 2012. 54

55. References
• Concrete technology today, Vol. 18, Portland Cement Association, July
1997.
• A.K Schindler & K. J. Folliard, Heat of hydration Model for cementitious
materials, ACI Material Journal.
• L. E. Copeland et al. Chemistry of hydration of Portland Cement, Search
Department, Bulletin 153.
• Jochen Stark, Recent Advances in field of cement hydration and
microstructure analysis, cement and Concrete Research, 2011.
• J. W. Bullard et al., Mechanism of Cement Hydration, Cement Concrete
Research, 2011.
• H. F. W. Taylor, Cement Chemistry, Academic Press London, 1990.
• Mindess et al., Properties of hydrated Cement Compounds, 2004.
• Standard Test Method for Measurement of Heat of Hydration (ASTM C
186)
• Class Notes 55

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