2.4 HYDRATION OF CEMENT

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2.4 HYDRATION OF CEMENT

• 2.4.1 The Hydration Reaction
• 2.4.2 Volume products of hydration

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Progress ofcement hydration
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Hydration of PFA
PFA reacts with the lime produced by the
hydration of cement to give more hydration
products - reducing the voids and lowering the
permeability.
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Cement HydrationGel pores 0.005 nm
Capillary pores 10 nm
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The need for Gypsum

• If pure C3A is mixed with water the reaction
  leads to uncontrolled setting. To prevent this
  Gypsum (Calcium Sulphate CaSO4.2H2O) is added to
  the cement clinker. This reacts with the C3A to
  form insoluble calcium sulphoaluminate, but
  eventually tricalcium aluminate hydrate is
  formed.

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Heat of Hydration
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Definitions (conventions for cement and
concrete) 

• Bulk volume The overall volume defined by the
  outer dimensions of the sample
• Net volume The volume of solids (excluding
  pores)
• Density The mass divided by the bulk volume
• Specific Gravity The mass divided by the net
  volume
• Porosity Volume of Pores
• Bulk Volume
• Bulk Volume - Net Volume
• Bulk Volume
• Units 1m3 1000 litres (l)

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Effect of w/c on permeability
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Pore size distribution
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2.4 HYDRATION OF CEMENT

• 2.4.1 The Hydration Reaction
• 2.4.2 Volume products of hydration

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Section 2.4 Question 1
Volumes in litres NOTE THAT THE TOTAL VOLUME
IS CONSTANT When mixed Part Hydrated
More Hydrated
Cement 0.063
Cement 0.127
Cement 0.317
Hydrated cement 0.465
Hydrated cement 0.35
Water 0.4
Pores 0.24
Pores 0.19